United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R04-93/157
September 1993
&EPA Superfund
Record of Decision:
Helena Chemical Landfill, SC
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S0272.101
REPORTDOCUMENTA~ON 11. REPORT NO. . 2. 3. RaclpIent'. Acn_lr No.
PAGE EPA/ROD/R04-93/157
4. TItle U1d Subtitle 5 Report Date
SUPERFUND RECORD OF DECISION 09/08/93
Helena Chemical Landfill, SC 6
First Remedial Action - Final
7. Author(s) a Performing Organization A8pt. No.
9. Performing Organization Name and Addnass 10 Project Tuk/Work Unit No.
11. ContI'8Ct(C) or Granl(G) No.
(CI
(G)
12. SponsorIng OrganIzation Heme end Adcll'8Ss 13. Type of Report .. PerIod Ccwsnd
U.S. Environmental Protection Agency
401 M Street, S.W. 800/800
Washington, D.C. 20460 14.
15. SuJIPIsrn8rtary Net.
.PB94-964014
16. Ab8trac:t (UmIt: 200 words)
The 4-acre Helena Chemical Landfill site is located on the northern portion of the
13.5-acre Helena Chemical Company property in Fairfax, Allendale County, South
Carolina. Land use in the area is mixed commercial, industrial, agricultural, and
residential. A water supply well to the city of Fairfax supplies water to 2,300
residents, and is located 200 feet west of the property. Surface water at the facility
drains into a small ditch which subsequently drains into Duck Creek, a tributary
located northwest of the property that flows into the Cooswatchie River located to the
west of the property. In addition, several wetland areas occur in the northern portion
of the facility in close proximity to the former landfill. Prior to the 1960s, and
until 1978, the Helena Chemical Company and two previous owners manufactured liquid and
powdered insecticides onsite. The facility consists of three buildings: the north
warehouse, which was used to formulate liquid insecticides; the south warehouse, which
was used to formulate powdered insecticides; and the office. The former landfill is
located north of the north warehouse and was reportedly used for disposal of chemical
wastes. Several above-ground solvent tanks,. which have since been removed, were used
to store solvents transported to the site by rail. Types of chemicals formulated or
stored onsite included pesticides, solvents, diesel fuels, and clays. In 1980, State
(See Attached Page)
17. Document Analysis L Descriptors
Record of Decision - Helena Chemical Landfill, SC
First Remedial Action - Final
Contaminated Media: s.oil, sediment, gw, sw
Key Contaminants: VOCs (benzene), other organics (pesticides), metals (chromium, lead)
b. lcIentlfterslOpln
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EPA/ROD/R04-93/157
Helena Chemical Landfill, SC
First Remedial Action - Final
Abstract (Continued)
investigations regarding an onsite waste dump indicated high levels of various pesticides
at the site. In 1981, the State required Helena Chemical to provide additional information
regarding site activities. The State, EPA, and Helena Chemical conducted additional site
investigations from 1981 through 1992. These investigations confir.med the presence of
site-related pesticides in the soil and indicated the presence of pesticides in sediment,
debris, ground water, and surface water in the vicinity of the for.mer landfill. Two
removal actions were conducted at the site during 1984 and 1992, and 500 and 1,000 yds3 of
contaminated soil, respectively, were removed to a pe~tted hazardous waste landfill.
This ROD addresses a first and final remedy for the remaining onsite contamination in the
soil, sediment, ground water, and surface water. The primary contaminants of concern
affecting the soil, sediment, ground water, and surface water are VQCs, including benzene;
other organics, including pesticides; and metals, including chromium and lead.
The selected remedial action for this site includes excavating approximately 20,000 yd3 of
contaminated soil and debris from the former landfill and areas adjacent to the northern
warehouse; treating the soil an debris using hydrolytic/photolytic dechlorination (HPD),
followed by ex-situ biodegradation; returning the treated soil and debris to the original
excavated areas; covering the treated soil with at least one foot of clean fill; providing
for a contingent remedy including low temperature thermal desorption, if treatability
studies indicate that the HPD/biological treatment cannot attain the soil remediation
goals; demolishing the for.mer formulation buildings, if necessary, to allow for removal
and treatment of all contaminated soil; testing the demolished buildings to determine
appropriate handling and disposal options; mitigating any impact to wetlands; extracting
and treating contaminated ground water onsite to POTW pre-treatment requirements, with
discharge to the local POTW; and monitoring excavated and treated soil and ground water
(in-situ, as well as, extracted and treated) to ensure compliance with all performance
standards. The estimated present worth cost for this remedial action is $3,900,000.
PERFORMANCE STANDARDS OR GOALS:
The soil excavation standard is based on protection of human health and the environment
and is equal to 50 mg/kg total pesticides. Soil treatment standards are based on RCRA
LDRs and range from 66 ug/kg to 1,300 ug/kg. Chemical-specific ground water treatment
goals are based on SDWA MCLs, and include benzene 5 ug/l; chromium 100 ug/l; lead 15 ug/l;
and pesticides 0.002-3 ug/l.
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RECORD OP DECISION
S'CHKARY OP REHBDIAL ALTERNATIVB SELECTION
HELENA CHBMICAL StJPBRP'UND S:ITB
PAIRFAX, ALLBNDALB COUNTY
SOOTH CAROLINA
PREPARED BY:
O. S. BNVIRONMEN'l'AL PROTECTION AGENCY
REGION IV
ATLANTA, GEORGIA
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DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Helena Chemical
Fairfax, Allendale County, South Carolina
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for
the Helena Chemical Superfund Site (the Site) in Fairfax, South
Carolina, which was chosen in accordance with the the Comprehensive
Environmental Response, Compensation and Liability Act of 1980, as
amended by the Superfund Amendments and Reauthorization Act of 1986
and, to the extent practicable, the National Oil and Hazardous
Substances Contingency Plan (NCP). This decision is based on the
Administrative Record file for this Site.
The State of South Carolina concurs with the selected remedy.
Appendix B contains the letter indicating their concurrence.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this
Site, if not addressed by implementing the response action selected
in this Record of Decision (ROD), may present an imminent and
substantial endangerment to public health, welfare, or the
environment.
DESCRIPTION OF THE SELECTED REMEDY
This remedial action addresses
principal threat at. this Site;
groundwater contamination.
onsite soil
as well as
contamination, the
onsite and offsite
The major components of the selected remedy include:
SOURCE CONTROL
o
Excavation of contaminated surface and subsurface
soil, with verification sampling;
o
Treatment of the contaminated soils by means of
hydrolytic/photolytic dechlorination and biological
degradation; .
o
Placement of the treated soils into on-Site excavations.
o
Site re-grading to prevent uncontrolled storm-water
run off into waters of the State or the United States.
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-2-
GROUNDWATER
o
Extraction of contaminated groundwater from the surface
(shallow) aquifer;
o
Treatment and discharge of the treated groundwater to a
local Publicly-Owned Treatment Works (POTW).
MITIGATION FOR ADVERSE IMPACTS TO WETLANDS
o
Mitigation for adverse impacts to environmental receptors
in accordance with regulatory guidelines established
under the authority of Section 404 of the Clean Water
Act.
SITE MONITORING
o
Quarterly sampling of groundwater and nearby public water
supply to monitor the concentrations and movement of
contaminants in affected and potentially affected
aquifers.
CONTINGENCY REMEDY
o
Low temperature thermal desorption (L~) is a
contingency remedy for soil treatment, to be implemented
should the chosen soil treatment technology prove
incapable of achieving performance standards.
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 to t~e remedial
action, and is cost effective. This remedy utilizes permanent
solutions and alternative and/or innovative treatment technology to
the maximum extent practicable for this Site. The selected
groundwater remedy component satisfies the preference for
treatment. The selected remedy for source control and soil
treatment also satisfies the preference for treatment. .
Since selection of this remedy will result in contaminated
groundwater remaining onsite above health-based levels until remedy
implementation is complete, a review will be conducted within five
years after commencement of remedial action to insure that the
,;
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-3-
remedy continues to provide adequate protection of human health and
the environment.
~/Y1~
Patrick M. Tobin
Acting Regional Administrator
9- 9 - 5' ~
Date
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TABLB OF CONTENTS
1.
SECTION
PAGE
1:.0
2.0
3.0
4.0
5.0
6.0
7'.0
8.0
SITE LOCATION AND DESCRIPTION ..... .......... ... ..........1
1.1
1.2
1.3
1.4
1.5
Site Location.......................................1
Site Description....................................1
Site Topography and Drainage. ................. ......4
C 1 ima t e ............................................. 4
Geology and Hydrogeologic Setting. ..... ..... ..... ...5
SITE HISTORY AND ENFORCEMENT ACTIVITIES ...... ........ ....6
HIGHLIGHTS OF COMMUNITY PARTICIPATION .. ..... ... ....... ...8
SCOPE AND ROLE OF THIS ACTION WITHIN SITE STRATEGY... ....9
SUMMARY OF SITE CHARACTERISTICS ... .......................9
5.1
5.2
Site-Specific Geology and Hydrogeology. .............9
Nature and Extent of Contamination ..... ..... .......18
5.2.1 Surface and Subsurface Soils .... ............20
5.2.2 Groundwater................................ .27
5.2.3 Surface Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
SUMMARY OF SITE RI SKS ...................................34
6.1
6.2
6.3
6.4
6.5
Contaminants of Concern............................ 36
Exposure Assessment.......... . . . . . . . . . . . . . . . . . . . . . .49
Toxicity Assessment........... .......... ... ...... ...52
Risk Characterization ........ .......... ... .........56
Environmental (Ecological) Risks ....... ..!.........59
DESCRIPTION OF REMEDIAL ALTERNATIVES ........ ............60
7.1
7.2
7.3
7.4
7.5
7.6
Alternative 1;
Alternative 2;
Alternative 3;
Alternative 4;
Alternative 5;
Alternative 6;
No Action.. . . . . . . . . . . . . . . . . . . . . . . . . .63
Landf i 11 ............................ 63
Biodegradation. ..................... .64
HPD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
HPD/Biodegradation. . . . . . . . . . . . . . . . . . .66
LTTD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
8.1
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES .........68
8.2
Criteria for Comparative Analysis ............... ...68
8.1.1 Threshold Criteria. . . . . . . . . . . . . . . . . . . . . . . . . .68
8.1.2 Primary Balancing Criteria ..................68
8.1.3 Modi fying Criteria.. . . . . . . . . . . . . . . . . . . . . . . . .69
Comparison of Alternatives. ........................69
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SECTION
9.0
10.0
Table of Contents (cont'd.)
1.1.
9.1
THE SELECTED REMEDY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
PAGE
9.2
9.3
Description of Selected Remedy......... ... .... .....71
9.1.1 Source Control.. . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
9.1.2 Ground Water Remediation ................. ...72
9.1.3 Wetlands Mitigation...................... ...73
9.1.4 Compliance Testing ..... ... ........ ..... .....74
9.1.5 Contingency Remedy... . . . . . . . . . . . . . . . . . . . . . . .75
Applicable or Relevant and Appropriate Rrequirements
( ARARs ) ......................................... 7 5
9.2.1 Applicable Requirements ........ ... ..... .....75
9.2.2 Relevant and Appropriate Requirements... .....76
9.2.3 Criteria 8To Be Considered8...... ....... .....79
Performance Standards.............................. 80
9.3.1 Excavation Standards........................ 80
9.3.2 Treatment Standards ................ .........80
9.3.3 Ground-Water Remediation Stds. ... ...........81
9.3.4 Storm Water Discharge Stds. ....... ..... .....81
9.3.5 Wetlands Mitigation............. . . . . . . . . . . . .81
STATUTORY DETERMINATIONS ........... ........... ......, ...82
APPENDICES
APPENDIX A - RESPONSIVENESS SUMMARY
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LIST OP PIGURES
iii
FIGURE
PAGE
- 1
2
3
4
5
6
Location Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Site Layout Map........... . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Monitoring Well and Soil Boring Locations .......... .10
Pesticides in Surficial Soils....................... 21
Soil Pathway Exposure Assumptions ..... ... ..... ..... .46
Ground-Water Pathway Exposure Assumptions ..... ..... .48
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LIST OF TABLBS
l.V
TABLE
-1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
PAGE
Phase II Slug Test Results. .... ..... ....... ..~..... .14
Hydraulic Gradients..... . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Phase III Slug Test Results ....... ......... ........ .16
Preliminary Contaminants of Concern. ... .......... ...19
Phase II pesticides in Surface Water & Sediment ... ..33
pesticides in Soils................................. 37
Semi-Volatiles in Soils........... ..... . ......... .. .39
Volatiles in Soils............................... . . .40
Summary of Ground-Water Contamination ... ......... ...41
Phase III Pesticides in Surface Waters & Sediments...43
GW Contaminant Exposure Data ...... ...... ... ...... ...50
Soil Contaminant Exposure Data .... ..... .............51
Summary of GW Exposure Risk ......... ............. ...53
Summary of Soil Exposure Risk ....... ... .............54
Summary of Health-Based Risk Criteria .. .......... ...55
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DECISION SUMMARY
HELENA CHEMICAL SUPKRFOND SITE
FAIRFAX, ALLENDALE COUNTY, SOUTH CAROLINA
SITE LOCATION AND DESCRIPTION
Paqe 1
1.0
1.1
SITE LOCATION
Helena Chemical Company, Fairfax, South Carolina is located on 13.5
acres adjacent to Highway 321 in Allendale County, South Carolina.
Figure 1.1 is a vicinity map. Located at the facility is a former
landfill which contains pesticide residues and other waste
materials generated on-Site. The former landfill .occupies
approximately four (4) acres on the northeast portion of the
Fairfax property. Figure 1.2 is an approximately scaled survey of
the facility showing the location of the landfill. The site is
encircled by a chain link security fence topped with barbed wire.
A city water well that is utilized by a population of approximately
2,300 is located 200 feet west of the property.
1.2
SITE DESCRIPTION
Three buildings exist on the Fairfax property; the north warehouse,
the office, and the south warehouse. The north warehouse, which
was once utilized to house the liquid insecticide formulation
operation, is currently used to store various pesticides,
herbicides, and fertilizers which are sold to farmers. There are
several significant features of the liquid formulation building
which were focal points of the investigation. Two 22,000 gallon
above ground sol vent tanks were once located near the north
entrance to the .kettle room. in the former liquid formulation
building. These tanks were present prior to Helena's occupancy of
the property. Solvents used in the formulation process were
delivered to the site by rail car via a rail spur which was used to
se'rve the facility. The solvents were offloaded by pressurizing
the tanker cars and pumping the solvents through product lines
which ran under the formulation building to the storage tanks. The
storage tanks were located in the area identified as the .tank
farm. on Figure 2. The solvents were then gravity fed to the
kettle as needed. The solvent tanks are no longer present;
however I the concrete .slab on which the tank saddles rested still
exists. The remains of a tank farm which was used to store the
technical grade pesticide compounds are located on the east side of
the liquid formulation building. Only the concrete pads on which
the tanks rested and a retaining wall remain. During the Remedial
Investigation (RI) a drain pipe which originates inside the
warehouse was observed and is suspected to have been used to
discharge effluent onto the ground surface in an area northwest of
the structure. The south warehouse where powdered insecticides
were formulated is no longer in use. A septic tank system which
serviced the property is located between the north liquid
formulation building and the office~
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2
Figure 1;
Helena Location Map
.,J-
r-.....
-.....
'-.
--
-"""""-.........
-"--""
------
----
--
,
/
.. /~
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3
Figure 2;
Helena Site Map
~
I "
.! ~'"
i i r'"~ m:~.['~ ~' ""
~~ ~ . """""~~"'" ~
2 i "~ - ~ -', i \\'" - ~ ~E~~~IN(
I ~
I ~ --fENCE
I Q-,J ~) ~ ...... ---- - APPROXIMATE
~ X. '" PRDPERTY BOUNDARY
: APPROX. 13.5 ACRES { 1 "" v"; I . [-] ~ '[..~ (\ -----.:.\
L__. . .' YJ. -- I ~-..... .~
APPRCX SEPTIC ~ I
TANK UlCATIDN
~y. R'AII Rn.an
$~
100
I
scale
o
100
I
feet
HICiH"'AY
$-13
£nVlrO""'tn~ol olld Sofrty Drslgll5. mG
U.S. HIJY 321
EN ..5.J:u:E.8
FIGURE 1.2
FACILITY SKETCH
HELENA CHEMICAL ca
F AIRFAX. SOUTH CAROLINA
DWG DATE:DJ 29 92 DWG NAME:HELSITJ
572. $/HER r11£Cr IX ~". -,. «ftJV3_~
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4
Located northwest of the north warehouse are the remains of a house
that burned sometime prior to 1988. The house belonged to the
previous property owner, Charles Blue. .
According to City of Fairfax Water Department records, a 12. water
main constructed of cast iron extends across the site between the
north warehouse and the former landfill. The water line trends in
a general east-west direction and is reported to have been
installed approximately ten years ago.
Between the years of 1971 and 1978, Helena used the Fairfax
facility for the formulation of liquid, and some dry, agricultural
insecticides. Prior to the ownership by Helena Chemical Company
(beginning in 1971), two other chemical companies operated at the
Fairfax facility: Atlas Chemical Company, owned by Billy Mitchell
(prior to the mid 60's), and then Blue Chemical Cornpany~ owned by
Charles Blue (mid 60's through 1971). Both Atlas Chemical Company
and Blue Chemical Company utilized the Fairfax facility for the
formulation of insecticides. Chemicals formulated and/or stored at
the facility prior to Helena's ownership include: DDT, .aldrin,
toxaphene, disulfoton, dieldrin, chlordane, BHC (benzene
hexachloride), and ethoprop (Mocap). The Fairfax facility is
presently being operated as a retail sales outlet and warehouse for
ag.ricultural chemicals. Chemicals used in the previous formulation
of insecticides by Helena at the Fairfax facility 'include!
toxaphene, methyl parathion, EPN (ethyl p-nitrophenyl
thionobenzene-phosphonate), and disulfoton. In producing the
insecticides, the chemicals were formulated as mixtures with other
ingredients including diesel fuel, aromatic solvents, and clays.
1.3
SITE TOPOGRAPHY AND DRAINAGE
The local topography of the Fairfax area exhibits little relief~
The Helena Chemical property slopes slightly to the north. North
of the property is a topographically low area that collects surface
water during period of high rainfall. Additionally, surface water
from the facility drains into a small ditch that parallels the
property to the northwest. . This ditch carries the water to Duck
Creek, a tributary located northwest of the property, which in turn
flows into the Coosawatchie River located to the west of the
Fairfax property. The creek and the river are located within a
three (3) mile radius of the Site.
1.4
CLIMATE
The relatively temperate climate of Fairfax is typical of the South
Carolina coastal plains region. This is largely due to the close
proximity of the Atlantic Ocean and its warm Gulf Stream current
flowing northward near the southeastern border of the state
creating a warming effect on the region.
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5
Da.ta provided by the South Carolina State Climatology office
indicated the annual mean temperature in the vicinity of Fairfax is
6S.1°F. The mean annual precipitation of Fairfax is approximately
47.95 inches. These figures are based on data gathered at Hampton,
S.C. which is the closest reporting station to Fairfax (a reporting
station has recently been established in Allendale, S.C.; however,
at the present time insufficient data has been gathered to
calculate the annual means) .
Prevailing winds in the Fairfax area exhibit seasonal variations.
In the spring, southwest winds are predominate; summer, south and
southwest winds prevail; autumn, prevailing winds are from the
northeast; and in winter, northeast and southwest winds have close
to the same frequency. Average wind speeds throughout the year
range from 6 to 10 miles per hour (Climate Report No. G5, S.C.
State Climatology Office, May 1990).
1.5
GEOLOGY AND HYDROGEOLOGIC SETTING
Site specific geological and stratigraphic data were developed
during the installation of test borings and monitoring wells;
Three distinct stratigraphic units were observed in the upper 145
feet of unconsolidate~ sediments encountered at the site, and a
fourth may be present.
The lowermost stratigraphic unit identified during the
investigation was a gray to green, fine grained clayey sand
interbedded with clay laminae and numerous shell fragments. The
unit was moist, but did not exhibit the saturated properties as
seen in the overlying sands. Based on lithology, this unit is
presumed to be the upper portion of the McBean/Santee Limestone
Formation. The observed thickness of this unit was approximately
45 feet. The maximum thickness of this formation was not determined
during the investigation.
Overlying what is presumed to be the McBean Formation is a
predominantly yellow to gold, fine to coarse sand. This unit is
also characterized by numerous shell fragments interspersed among
the sand grains. These sands are thought to be a member of the
Barnwell Group. The Barnwell Group is comprised of the Tobacco
Road Sand and the Dry Branch Formation. Recent investigations have
indicated that the contact between the formations is a one to three
foot thick layer. of coarse sand and gravel. This gravel layer was
not positively identified in any of the borings; therefore,
distinct facies changes were not stratigraphically identified
during the RI.
Overlying the sands of the Barnwell Group is a light gray and green
medium sand which in some locations graded .to a coarse tan sand
with some pebbles and shell fragments. The lower contact between
the formations was distinguished by a silicified shell hash in
other locations. The sands graded in a fining upward sequence to a
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6
very fine to medium grained sand intermingled with a dense red,
orange, and gray mottled clay. These sediments are characteristic
of what is thought to be the Duplin Formation.
Based on the boring logs from MW-12, MW-14, MW-19 and MW-20, there
appears to be a lateral facies change to the north of the landfill.
Surface soils north of the landfill consist of a dark gray, dense
clay. Due to limited information, it is unclear whether the
detrital sand underlying this area is a continuation of the Duplin
or if a portion of the Duplin has been eroded and the sand a
product of more recent depositional processes. .
The highest yielding aquifer in the area surrounding Fairfax is
found within the sands of the Cape Fear, Middendorf, and Black
Creek Formations. These regional aquifers are some of the most
permeable units in the stratigraphic column, providing large
quantities of water for both municipal and private use.
The high clay content of the Black Mingo Formation results in
relatively low permeability. This has led to the designation of
the formation as an aquitard or aquiclude. Some small domestic
wells, however, may be utilizing water from more permeable portions
of the Black Mingo.
Although previous studies have indicated the McBean was not thought
to be important as a public or commercial source, member beds
within this formation produce sufficient water for use. The Town
of Fairfax south municipal well is screened within the
McBean/Santee Formation. A pumping test on the municipal well
conducted by the city engineers indicated a transmissivity of 500
ft.2/day at a pumping rate of approximately 298 gpm. The overlying
sands of the Barnwell Group have been described as a relatively low
permeability, low yielding aquifer that is used primarily for
domestic water supply. The Barnwell underlying the site, however,
is recognized as a highly permeable, saturated sand.
Previous investigations tentatively identified the presence of the
Cooper Marl at the Site. Recent investigations, however, have
indicated that the surficial sediments are characteristic of the
Duplin Formation of Miocene age. The upper portion of the Duplin
Formation appears to be acting as an aquitard at the Site.
2.0
SITE HISTORY AND ENFORCEMENT ACTrvITIES
Several companies have operated pesticide formulation facilities on
the Site currently owned by Helena. Prior to the mid-60's, the
Site was owned by Atlas Chemical Company, and from the "mid-60's
until 1971 by Blue Chemical Company. Between the years 1971-1978,
Helena Chemical company used the Site for the formulation of both
liquid and dry agricultural insecticides. Chemicals that have. been
stored and/or formulated at the facility during its active life
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7
include DDT, aldrin, toxaphene, disulfoton, dieldrin, chlordane,
benzene hexachloride (BHC), ethoprop, methyl parathion and ethyl p-
nitrophenyl thionobenzene-phosphonate (EPN) . During the
formulation process these chemicals were mixed with carrying agents
including diesel fuel, volatile organic chemicals and adsorbent
materials.
The first regulatory actions taken with respect to the Helena Site
occurred in November, 1980, as a result of reports by a former
employee of Helena and a newspaper reporter that a waste dump was
being operated on the Site. The Site was investigated at that time
by. the South Carolina Department of Health and Environmental
Control (SCDHEC). Numerous soil samples were collected and
analyzed in December, 1980. High levels of various pesticides;
including aldrin, BHC isomers, chlordane, dieldrin, disulfoton,
endrin and toxaphene were detected in these samples. As a result
of these findings, SCDHEC requested that Helena provide further
information regarding activities at the Site, including chemicals
handled as part of the operation, waste disposal practices and
other pertinent information with respect to past and present Site
activities.
SCDHEC issued a Notice of Violation to Helena in July, 1981, for
the operation of a waste disposal facility in violation of
applicable South Carolina regulations. Negotiations between SCDHEC
and Helena resulted in the issuance of Administrative Consent Order
No. 81-05-SW on October 1, 1981. In compliance with the terms of
this Consent Order, Helena conducted investigations at the Site
lasting from October, 1981, to July, 1982. The results of these
studies indicated that surficial soils were heavily contaminated
with pesticides, including those identified in the earlier sampling
described above. The results of analyses of ground-water samples
obtained as part of this investigation were contradictory; the
positive results reported from the first sampling event were not
confirmed in samples taken at that time or in subsequent sampling
events. Surface water samples, taken from water standirig in the
wetland areas in the northern portion of the Site, were found to be
heavily contaminated with site-related pesticides.
Helena prepared a plan for site remediation which was submitted to
SCDHEC for review, and, under the terms of an amendment to
Administrative Consent Order No. 81-05-SW, dated March 12, 1984,
remediation efforts were conducted that consisted mainly of the
removal of contaminated soils to a permitted hazardous waste
landfill.
In 1985, EPA, in conjunction with SCDHEC, conducted a Site
Screening Investigation at the Helena Chemical Site in order to
prepare a Hazard Ranking System (HRS) package for the Site in order
to determine whether the Site should be included on the National
Priorities List (NPL). The HRS ranking was completed in June,
1987, and the Helena Site was proposed for listing in June, 1988.
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8
The Site was listed on the NPL in February, 1990.
In' April, 1989, an Administrative Order by Consent (AOC) was
jointly developed, negotiated and agreed to by EPA arid Helena
Chemical Company. Under the terms of this AOC, Helena agreed to
conduct a Remedial Investigation (RI) and Feasibility Study (FS) at
the Site under the oversight of EPA. The purpose of the RIfFS
process was to develop an appropriate. remedy for the Site as
required by the National Contingency Plan (NCP). Helena retained
the services of Environmental Safety and Designs, Inc. (ENSAFE), of
Memphis, Tennessee as their contractor to conduct the RIfFS. RI
field activities began in May, 1989, and were completed in April;
1992.
Two removal actions for contaminated soils have taken place at the
Site. In addition to the removal of approximately 500 cubic yards
of contaminated material conducted by Helena in March, 1984, as
discussed above, in April, 1992, approximately 1000 cubic yards of
contaminated soils were a~so removed by Helena under the oversight
of EPA and likewise transported to a secure hazardous waste
landfill.
3.0
HIGHLIGHTS OF COMMUNITY PARTICIPATION
Initial community relations activities at the Helena Chemical NPL
Site included development and finalization of the Community
Relations Plan in December 1989. An information repository was
established at the Fairfax City Hall in January 1990.
A "kickoff" fact sheet announcing the start of the RIfFS was issued
in April 1990. On April 19, 1990, EPA held a public meeting at the
Fairfax Community Center to present the Agency's plans for the
RIfFS. The meeting was attended by several local citizens;
representatives of Helena Chemical, elected local officials and was
covered by local newspapers. EPA's presentation to the public
included information on how to participate in the investigation and
remedy selection process under Superfund. At the meeting, several
questions were asked and a fair amount of interest was expressed by
the community.
Following completion of the FS, a second public meeting was held on
May 27, 1993, to update the public on the RI findings to date, and
to present the proposed plan for the remedial actions at the Site.
The meeting was attended by only a few members of the public, with
no press coverage.. At this meeting, the primary concerns expressed
by the public involved the threat posed by contaminated ground
water to the nearby public supply well.
Proposed Plan fact sheets were distributed on May 18, 1993. An
advertisement was published in two of the local newspapers on the
same date. Both the advertisement and the fact sheet highlighted
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9
the Public Comment period extending from May 18, 1993, until June
17, 1993.
At the Proposed Plan public meeting on May 27, 1993, EPA presented
the Agency's selection of Preferred Alternatives for addressing
soil, sediment, surface water and groundwater contamination at the
Site. Public comments and questions are documented in the
Responsiveness Summary, Appendix A.
4.0
SCOPE AND ROLE OF THIS ACTION WITHIN SITE STRATEGY
The purpose of the remedial alternative selected in this ROD is to
reduce current and future risks at this Site. The remedial action
for soil will remove current and future health threats posed by
contaminated shallow soil and will prevent leaching of the soil
contaminants to groundwater. The groundwater remedial action will
remove future risks posed by potential usage of contaminated
groundwater. It will also serve to remove the threat to surface
water by reducing the concentrations of surficial aquifer
contaminants reaching nearby surface water systems. Wetlands
mitigation will address the unacceptable levels of environmental
risk posed by contamination of sediments and surface waters in on-
site and adjacent jurisdictional wetlands. This is the only ROD
contemplated for this Site.
5.0
SUMMARY OF SITE CHARACTERISTICS
The RI investigated the nature and extent of contamination on and
near the Site, and defined the potential risks to human health and
the environment posed by the Site. A supporting RI objective was
to characterize the Site-specific geology and hydrogeology. The
main portion of the RI was conducted from May 1989 through April
1992. Onsite locations of soil borings, soil samples, and monitor
wells are shown in Figure 3.
5.1
SITE SPECIFIC GEOLOGY AND HYDROGEOLOGY
The local hydrogeologic characterization discussed below was
derived from RI data, including falling head permeability tests,
grain size analyses, slug tests, piezometric surface maps, and
numerous boring logs. In addition, the Barnwell Group aquifer
system was monitored to determine if the City of Fairfax Municipal
well affected the aquifer during pumping and non-pumping events as
described below. .
For the purpose of the RI, the hydrogeologic assessment
concentrated primarily on the uppermost aquifer at the Site. The
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10
Figure 3; Monitoring Wells and Soil Borings
~ ("" . $-
o ~ CITY IF rAII!F"AX~ 100
'" r'- HlMCIPAL Io'EU.
ffi }' I
~~! c ", .~. ~ ~~.
~1 '''-- ~ K) \
~ : -- -- -- ~ ~ H\'/ila '< ~ LEGEND
I -- --~, H\'/-17 \ ~ - TREE LINE
I """-<.. - fENCE
I T ~ ---- - APPROXIHATE
I )\,/-1 Q-J ~) ~ PROPERTY BOUNDARY
I H\,/-2 APPROX. 13.5 ACRES '\2 ... K ~ - - - ~~L STREAH
I H\'/-15 { ~ .BH-3 \--- - INTERMITTENT STREAM
I . HCB-5 ""'-16' J ..... '" 0 "",-I - HDNITORING "ELL LOC.
:-3lK"f':~ fOR~ ~ttON J ~ "ra.~'H .BHIHCB-I - =~TUIO .
r:LJ DISCHARGE PIPE ~.~lt "'-5 "'" ~\
15 I ~ CB-I0 "CB-~'
~ ~-4,
~: K EQUlPHD/T . "~:~ . . " ~
~ I "'ASH PAD ~ HCB-l i ~ ""'-14 '\ ~20
is I U \oJ HCB a C ""-19
~II ~HCB-2 g I -$- {
;j K ~"'-6 ~ HCB-7 ""-12 ~
~ L- _1. IJAREHOUSE ~ Q)HCX1t HC.: ~-~ ~
o
100
I
feet
HIGH\IAY
S-13
CSX RAI~(w)
-------------
---
"",-2600 M\J-25
u.s. HIJY 321
""'-;>""0+1\,/-21
£nv//"onf'lenta{ ana SaFety Pesl9fIs. Inc.
FIGURE 2.4
BORING AND MONITORING
IJELL LOCATIONS
HELENA CHEMICAL ca
FAIRFAX, SOUTH CAROLINA
~ SINO I1II(lT /IR. IO#fif$TN _34 ~_?WU DWG DA1E:OJ 9 92 we NAME:HElFAX28
-.r ". ..
EN ...!:i.RFE8
-------
11
uppermost aquifer occurs within sands of the Barnwell Group and the
lower portion of the Duplin Formation. Member beds within these
fGrmations may exhibit minor facies changes; however, they are
considered to be hydraulically connected.
Beneath the site, the upper portion of the Duplin Formation at
t~mes demonstrates the hydrogeologic characteristics of an
aquitard. High clay content and corresponding low permeability are
two characteristics that limit vertical groundwater flow in this
unit. Grain size analyses and boring logs indicate that the Upper
Duplin has a high silt and clay content. The average silt and clay
fraction from nine (9) soil samples was 33 percent. The samples
averaged 90 percent finer than the upper limit designation. for fine
sand. These analyses suggest that the Upper Duplin is a silty;
clayey very fine sand with the capability to retard groundwater
flow.
Estimates of permeability were determined with Shelby tube samples
collected from the Upper Duplin. Eight undisturbed soil samples
were obtained from MW-4, MW-8, MW-10, MW-14, MW-20, MW-22, MW-24,
and MW-26 by pushing a thin walled Shelby tube 12-24 inches into
the soil. Rigid wall falling head permeability tests were
conducted on these samples in accordance with the Corp of Engineers
method EM 110-2-1906. The resulting permeability values were
indicative of an aquitard, and they highlight the capability of
this unit to restrict near surface groundwater movement. Two
additional thin wall Shelby tubes were collected from the clay cap
overlying the closed landfill, and these soil samples also exhibit
low permeabilities.
The upper aquifer system appears to be comprised of, in descending
order, the lower sands of the Duplin Formation, the Tobacco Road
Sand Formation, and the Dry Branch Formation. These units exhibit
sa.turated conditions and appear hydraulically connected in the
study area. Although there are a few thin clay/silt, laminae
present in the upper 30 feet of the unit the limited thickness and
lateral extent of these laminae suggest that they do not impede
vertical groundwater flow. Well logs indicate these sands to be
vertically uninterrupted from an average depth of approximately 12
feet to a depth of at least 90 feet below ground surface. The
overall thickness of the uppermost aquifer is estimated to be
approximately 80 feet.
The Fairfax municipal well log included in the RI describes a
yellow and gray clay from 90 to 103 feet. During the installation
of soil boring HCB-5 on the north end of the Helena property a dark
gray to green, fine grained clayey sand interbedded with clay
laminae and numerous shell fragments was ident'ified from
approximately 95 to 145 feet below ground surface. The unit was
moist, but did not exhibit the saturated properties as seen in the
upper Eocene sands and appeared relatively impermeable. Based on
the aforementioned lithological descriptions, this unit is thought
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12
to be representative of the upper section of the McBean F0rmation.
Defining the lateral and vertical extent of this unit was beyond
the scope of this investigation. The drillers log from the City of
Fairfax municipal well, however, indicates the presence of
limestone at depths of 260 to 347 below ground surface. The
limestone may be representative of the Santee which varies
considerably in the area and may signify actual lateral facies
changes between the downdip Santee and the updip McBean.
Water level measurements conducted during the RI indicate that
groundwater flow directions in both the shallow and deep portions
of the upper aquifer exhibit seasonal variation. Summer water
levels indicate that shallow flow is directed to the
south-southwest. The piezometric diagram of water levels taken in
April 1991, however, reveals directional components to the south,
east and southeast. Similarly, but to a lesser extent, groundwater
flowing in the deeper portions of the aquifer exhibits variation in
direction throughout the year. Although deep. well control is
limited, flow direction in the summer is directed to the southwest.
This corresponds with shallow flow directions. The data for April
and September, 1991, indicate that the deeper groundwater flow was
to~ard the south-southeast.
The lack of vertical groundwater flow is apparent from the minimal
differences in water level between wells in the nine (9)
deep/shallow well clusters at the site. From the eight (8) water
level measuring events that have been conducted, the maximum
downward vertical gradient was 0.018 feet per foot between MW-1 and
MW-2 for July, 1990. The minimum was 0.0001 feet per foot between
MW-19 and MW-20 for October, 1991. The average downward gradient
of the nine (9) well clusters for the eight (8) measurement events
was 0.002 feet per foot. .
Interestingly, the upper aquifer appears to change from unconfined
to confined conditions at different times throughout the year. The
July, 1990 water levels for most of the wells on site were from 2
to 2.5 feet below the top of the confining portion of the Duplin
formation. This suggests unconfined conditions may exist for at
least a portion of the year. Conversely, confined conditions were
encountered in the spring of 1991 when water levels were well above
the contact between the more permeable sands of the upper aquifer
system and the overlying less permeable clayey sands. This
artesian condition was further supported by groundwater flowing out
the top of MW-14 in March, 1991. One simple explanation for this
phenomenon is associated with changing water levels in the upper
aquifer.
During the dryer portion of the year (July and August), water
levels fall below the base of the clayey sands of the Duplin
Formation. This effectively dewaters the upper portion of the
aquifer. Dewatering is a characteristic behavior of unconfined
aquifers. During wet periods when water levels rise above the
-------
13
contact between the permeable sands and the low permeability clayey
sand within the Duplin, the aquifer exhibits confined conditions.
To obtain estimates of groundwater velocity, several slug tests
were conducted at the site on March 4 and 5, 1991. Testing
consisted of rising and/or falling head slug tests for MW-2, MW-4,
MW-6, MW-8, and MW-10.
Rising and falling head slug tests were performed to characterize
the hydraulic conductivity (K) of aquifer materials. Slug tests
were initiated during Phase II-B and Phase III of the RI. Before
each slug te.st was initiated, the static water level in. the well
was measured using an electronic water level indicator. A
stainless steel cylinder of known volume was then introduced
.instantaneously. into the well, at which time, the water level and
the time were recorded. Periodically, water level/elapsed time
measurements were made as the head fell back to the original level.
Similarly, rising head slug tests were preformed by removing the
slug and recording water level/elapsed time measurements as the
head rose back to normal. For slug tests, the time required for
the water level to return to normal is a function of the hydraulic
conductivity (K) of the aquifer.
For this investigation, an In-Situ, HERMIT 1000B data logger and a
50 psi pressure transducer were used to record water level/elapsed
time measurements during each slug test. For purposes of graphing
data, the instrument was programmed to record measurements on a
logarithmic time scale. The slug consisted of a five-fOot (5)
long, 1.66-inch dfameter stainless steel cylinder with a stainless
steel ring welded on one end. A teflon coated stainless steel cord
tethered to the ring served to suspend the slug in the well just
above or below the water level. At the beginning of each test, the
da.ta logger was activated the instant the slug was either lowered
into or removed from the water.
The hydraulic conductivity (K) calculated from each slug test is
presented in Table 1 below. The methods used to arrive at these
values are discussed below. Rising and falling head slug test data
from each well were graphed as time (elapsed) versus Log (H/Ho) in
order to create a straight line. Log(H/Ho) is the Log base ten of
the change in head divided by the initial head. Hydraulic
conductivity (K) was computed from these plots using a. method
developed by Hvorslev.
This method utilizes a variable known as the basic time lag in an
equation that calculates the hydraulic conductivity. Hvorslev
contends that the basic time lag is the time at which the head
ratio (H/Ho) equals 0.37. Log (H/~) was plotted against time on
standard graph paper. A corresponding basic time lag was taken
from the time scale at .the bottom of each diagram, and then
calculated using an equation for hydraulic conductivity.
-------
14
L
Falling 2.5
MW4 Falling 1.23 kmax = 9.5
ft/day
MW6 Falling 9.2 kInin = 1. 23
ft/day
MW6 Rising 4.6 kave = 5.3
ft/day
MW8 Rising 9.5
MW10 Falling 4.2
MW10 Rising 5.6
The Hvorslev equation used in these calculations was developed for
confined conditions with the assumption that the test. well is
screened in the upper portion of a permeable unit that is overlain
by an impermeable unit. This scenario approximately describes
Fairfax site. conditions. .
To estimate groundwater velocity, the hydraulic gradient was
derived from the piezometric data generated during the RI. The
maximum and minimum slopes between contour lines were measured
directly from the isocon maps developed from this data, and these
values are shown in Table 2.
Shallow Wells Max 0.0026
Min 0.00033
Deep Wells Max 0.0035
Min 0.0007
Estimates of the shallow horizontal groundwater velocity (V) were
calculated from the following formula:
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15
v = Ki/n
Where:
v = groundwater velocity
K = hydraulic conductivity
i = hydraulic gradient
n = porosity
A porosity (n) of 25 percent was chosen based on estimates for
medium-to coarse-grained, poorly sorted sand aquifers. The maximum
and minimum estimated velocities were calculated using the maximum
and minimum hydraulic conductivities and corresponding hydraulic
gradients in the formula. .
Bstimated Shallow Groundwater Velocity V (ft/day)
Vmax = (Kmax * imax)/n = 0.1 ft/day
Vmin = (Kmin * imin)/n = 0.0016 ft/day
Additional slug tests were completed upon completion of Phase III
field activities. With the following exceptions, Phase III slug
tests were conducted in a manner similar to the Phase II-B slug
tests: .
Phase III tests incorporated a different type of slug than
Phase II-B. Instead of using the stainless steel cylinder,
one gallon of deionized water was .instantaneously. introduced
in the well.
Only falling head tests were conducted as water was not
. instantaneously. removed from the well.
For the Phase III investigation, an In-Situ HERMIT 2000 data logger
and a 20 psi pressure transducer were used to record water
level/elapsed time measurements during each slug test. A one
gallon jug of deionized water was used to slug each well. At the
beginning of each test, the data logger was activated the instant
that water was poured into the well.
Data reduction and compilation were conducted using the same
equations and calculations described for the Phase II-B slug tests~
The Phase III slug test graphs are presented in Appendix C and
Table 3 summarizes the hydraulic conductivity values derived from
the graphs.
To determine if the aquifer supplying the Fairfax municipal well is
separate from the shallow aquifer beneath the site, two aquifer
communication tests were conducted the week of November 11, 1991.
The City of Fairfax public works department provided - full
cooperation during the tests.
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16
~
:!I!I~1Ii~t;il!!li!ii;!i!I!~\lill::!I!I!I\~11:~~:~!~11 \. .w....
...:~i~[tl~t~fi1~\~:it~!:~II:::!I!:!lfJ.
MW5
MW15
Falling
Falling
Falling
10.04
3.23
MW17
3.15
The first test involved pumping the city well for three 1-hour long
intervals separated by nonpumping periods of approximately 1-hour
in length. This test was designed to approximate the normal
operating conditions of the city pump system. During. the test,
water levels were monitored in three observation wells (MW-5,
MW-15, and MW-17). Data from this test were inconclusive because
identifiable trends did not develop from short duration p~ping.
Th~ second test was conducted to investigate what effects might
result from pumping the city well for longer than one hour. Pumping
duration for the second test lasted approximately 5.5 hours and
MW-5, MW-15, and MW-17 served as observation wells again. With a
pumping duration of 5.5 hours, this test was never designed or
intended to be a constant rate aquifer test.
A Hermit 2000 data logger with three pressure transducers and a
barometric pressure probe were used during each test. Each
observation well had one of the pressure transducers-monitoring
water level fluctuations. The barometric probe was placed on the
ground to measure changes in barometric pressure during the tests.
The data logger recorded measurements from the four transducer
iHputs simultaneously and on five-minute intervals during pumping
and nonpumping events.
For the second test, the data logger was activated approximately
17.5 hours before the city well pump was started to investigate
local water level trends. The static water level in each
monitoring well at the time the data logger was activated became
the zero reference level for that well. Throughout the recording
period, the data logger recorded water level changes from this
original reference level.
Prior to the test, the city water tank was allowed to "drain to
approximately 1/3 capacity. Because some water had to remain in
the tank to maintain water pressure, this was the lowest water tank
level that Fairfax water supply officials would permit. Pumping at
390 gallons per minute (gpm), it took the city water supply well
approximately 5.5 hours to refill the water tank during the test.
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17
Drawdown values from each well were plotted against time to
investigate water level trends. Drawdown is represented as a
positive deflection from the original zero reference level in the
data. Water levels recorded above the original reference level
were recorded as negative drawdowns. Similarly, a rise in water
level is represented by a negative deflection. In all three
monitoring wells there was a general downward trend in water levels
with time. This may be the result of increasing barometric
pressure at the site. When the water level graphs were compared to
the barometric pressure graph, however, the graphs show a definite
change in water level with respect to pressure along the time axis.
The difference in drawdown changes may be due to the difference in
water level elevation. .
Interestingly, water levels in each observation well rose abruPtly
when the pump was turned on. Although immediate, the maximum rise
in any of the wells was slightly above 0.1 feet. While the pump
was running, water levels fluctuated greatly. When the pump
stopped, water levels dropped to levels corresponding to prepumping
trends.
This phenomenon of abrupt rise and fall of water levels induced by
pumping is common in confined and semiconfined aquifers. The
occurrence is attributed to the elastic properties of aquifer
materials (Lohman, 1972). When the hydraulic pressure in an
artesian aquifer is reduced from pumping, the aquifer matrix
compresses to compensate. This matrix compression is physically
manifested as a slight net reduction in the thickness of the
aquifer. When pumping is halted, the aquifer matrix elastically
rebounds and the original aquifer thickness is recovered.
Ultimately, what appears to be a rise and fall in water levels may
ac.tually be a decrease and increase in the thickness of the
aquifer. During the test, as aquifer thickness changed, ttle ground
surface, well casings, and the transducers attached to the casings
were lifted or lowered with respect to the nearly static water
level. These reactions were recorded by the transducers as changes
in water level.
With regard to communication between the deep city water supply
aquifer and the shallow aquifer beneath the site, the results of
this test are inconclusive. No large scale effects (obvious
drawdown) from pumping were observed in any of the monitoring wells
over the relatively short pumping duration used in this test. A
much longer pumping duration (24-hours or more) may be necessary to
investigate whether the observed phenomenon is the result of a
hydraulic connection between the two aquifers.
While evaluating the results of this pump test, however,
consideration should be given to the actual city pump system
configuration. According to Fairfax water supply officials, the
city pump rarely runs longer than 1/2 an hour at a time.
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18
Therefore, the pump test duration of 5.5 hours created much more
stress on the aquifer than normal pumping conditions would create.
Even though greater stress occurred during this test, no excessive
drawdowns were observed in the monitoring wells.
Given the uncertainty associated with the pump test already
conducted and the possibility of communication between the shallow
aquifer and the production zone of the City well, EPA believes that
further pump tests are warranted. The details by which additional
pump tests will be conducted will be determined during the Remedial
Design review process.
5.2
NATURE AND EXTENT OF CONTAMINATION
can be swmnarized as
Envirorunental
follows:
contamination at
the Site
1}
Organic and inorganic constituents of concern have been
identified :in the various media. The primary
constituents of concern at the Site include: aldrin,
alpha-BHC, beta-BHC, delta-BHC, gamrna-BHC, DDT, DDD, DDE,
dieldrin, endosulfan, endrin, endrin ketone, toxaphene (
endosulfan sulfate, disulfoton, benzene, lead and
chromium. Table 4, reproduced from the RI, identifies
the preliminary contaminants of concern for the Site.
2)
Surface and subsurface soils throughout the Site have
been affected by past waste disposal activities. The
highest levels of contamination are found in the vicinity
of the former liquid formulation building now used as a
warehouse, in the vicinity of the old landfill, and near
the southerrunost building on the Site in an area where
transhipments of materials from railroad cars occurred.
3}
Ground waters in the aquifers immediately underlying the
Site have been affected by waste disposal activities at
the Site. The ground waters underlying the Site are
considered to be Class lIB ground waters under the draft
EPA Guidelines for Ground-Water Classification,
indicating that they are a potential source of public
water supply. These ground waters are also classified as
Class GB ground waters under South Carolina regulations.
The ground water has been contaminated to levels that
render it a threat to public health should it ever be
used for potable water supply and which exceed state
ambient standards for Class GB ground waters. Ongoing
sampling has to date revealed no site-specific
contamination in the nearby municipal water supply well.
High levels of contamination remain in soils and waste
materials in the old landfill located in the northern
4}
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19
portion of the Site. These soils and waste materials are
likely to be a continuing source of ground-water
contamination.
5)
Surface water and sediments in on-site wetlands and
drainage pathways have been affected by past waste
disposal activities. Pesticide concentrations in samples
taken from on-site surface waters exceeded criteria that
I
I
SOIL/SBDDmN'l'S
Dieldrin
Endosulfan
Endrin Ketone
4,4'-DDT
Disulfoton**
Tributylphosphorotrithioate
(TBPT)**
Toxaphene
Aldrin
Endosulfan Sulfate
Endrin
Methoxychlor
4,4'-DDE
4,4'-DDD
BHC (a, B, 4 and gamma)
GROONDWATER
Benzene
Aldrin
Endosulfan II
Toxaphene
DDT (plus DDE & DDD)
BHC (a, B, 4 and gamma)
Dieldrin
Endrin
Endrin Ketone
Heptachlor Epoxide
Disulfoton
TBPT
Lead
Chromium
SURPACB WATER
.1
I
BHC (B, 4)
Dieldrin
Endrin Ketone
are protective of aquatic life. Sediments in the on-site
wetland areas were found to be contaminated with site-
related pesticides at levels that are likewise likely to
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20
have an adverse impact on indigenous aquatic life.
6 )
Background and on-site air sampling indicates that local
ambient air has not been affected by past waste disposal
activities.
5.2.1
Surface and Subsurface Soils
The results of the field investigation identified varying
concentrations of polychlorinated pesticide compounds and minor
quantities of volatile organics in shallow surface soils (0 to 3
feet) . Soiis from the 1 to 3 foot interval would normally be
considered shallow subsurface soils; however, for purposes of this
discussion soils from 0 to 3 feet will be referred to as surface
soils. Surface soils were collected employing hand augering
techniques as previously described. Figure 4 is an isocon
displaying the relative distribution of total pesticides in surface
soils at the Fairfax site.
In addition to surface soil samples, ten soil borings were
completed utilizing hollow stem auger techniques. Soil samples
were collected for analysis from the surface, and from just below
the interface of the vadose and saturated zones. Analytical
results from some deep soil boring samples have indicated elevated
levels of chlorinated pesticides.
5.2.1.1
VOCs in Soils
Soil samples collected throughout the RI have identified relatively
low levels of various volatile organic chemicals (VOCs). The most
commonly detected were acetone and methylene chloride; however, the
data validation review suggests that these and some other
contaminants may be laboratory artifacts. Two other chlorinated
solvents were identified in soil samples, tetrachloroethylene
(PCE), and trichloroethylene (TeE), although the TCE detected in
two samples is believed to be a laboratory artifact. In addition,
the aromatic solvents, benzene, toluene, ethylbenzene, and xylene
were identified. Xylene is considered to be directly related to
the formulation process. The VOCs found during the RI are
discussed below.
Acetone
Acetone is a clear, colorless liquid with a fragrant mint-like
odor. Acetone is a common organic solvent which is highly soluble
in water. It is also one of the most common laboratory
contaminants found in environmental samples. Acetone was
-------
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II:LJIG2J
~
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bI
.~
r.s..
(f)
..-i
d.~
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tf)
(f)
<1J..-i
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.~.~
UU
.~ .~
.LJ~
(f)~
<1J ;j
o.tf)
I
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I
~
TOT AL PESTICIDES
0-1'
I
4j
~
~
-.-
NlllNAY
loP
1'0 '-).
LEGEND
,......... - na: L»C
--FDa:
- - PIIftIIn ---
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~ CIIf7Do8 811111YM..
---=
.1
.1
nGUIE 4.1
PEST1C1DES IN SOILS
HEL.EtIA DOJCAI. CDHI'NIy
F'AIItf"M, SIJffii CARDU~
-------
22
identified
collected.
(ppb) .
in approximately 57 percent of the soil samples
Concentrations range from 2 ~g/kg (ppb) - 13,000 ~g/kg
Methylene Chloride
Methylene chloride is a clear, colorless, highly volatile liquid.
It is used as a degreaser, photographic film processing chemical,
solvent, raw material for organic synthesis, and a fumigant. It is
soluble in water to 20,000 mg/l. Methylene chloride is a common
laboratory contaminant found in environmental samples.
Approximately 38 percent of the surface soil samples analyzed
indicated variable levels of methylene chloride. Concentrations
range from 2 ppb - 140 ppb. .
Tetrachloroethylene
Tetrachloroethylene (PCE) is a colorless liquid with a chloroform-
like odor, and is slightly soluble in water (150 mg/l). It. is used
for dry cleaning, metals degreasing and heat exchange fluid. PCE
was formerly used in mixtures with grain protectants and certain
liquid grain fumigants (vermifuge).
Tetrachloroethylene was identified in less than one percent of the
soil samples. Concentrations ranged from 11 ppb - 240 ppb.
Trichloroethylene
Trichloroethylene' (TeE) is a c.olorless, mobile, volatile liquid
with a chloroform-like odor. It is used as a degFeaser, dry
cleaning solvent, gas purification agent, and a raw material in
organic chemical manufacturing.
Trichloroethylene was identified in two soil samples, 55-10-1 and
55-19-2. The concentrations were 24 and 210 ppb, respectively. TeE
was also detected at 19 ppb in the trip blank submitted with these
samples on 02/26/91. The samples were run consecutively indicating
the values may be laboratory artifacts or lab error.
Benzene
Benzene is a clear, colorless, volatile liquid which. is very
slightly water soluble. Benzene is a component of gasoline and an
organic solvent which was formerly used (on a limited basis) in
pesticide formulation.
Benzene
samples.
was identified in approximately three percent
Concentrations ranged from 3 to 1,300 ppb.
of
the
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23
Toluene
TE>luene is a colorless liquid with a benzol-like odor. It is used
as a solvent, and in dye manufacturing, artificial leather
production, asphalt and naphtha constituents, fuel blending and
extraction of organic soluble plant materials.
Approximately eight percent of the soil samples identified low
levels of Toluene. Samples range from a low of 1 ppb to a high of
210 ppb.
Bthylbenzene
Ethylbenzene is a colorless liquid with an aromatic odor and
limited water solubility (140 mg/l). It is used in synthetic
rubber manufacturing, as a solvent, and is component of gasoline.
Ethylbenzene was detected in approximately three percent of the
soil samples. Concentrations range from 3 ppb - 4100 ppb.
Xylene
Xylene is a clear liquid which consists of a mixture of three (3)
isomers: ortho-, meta-, and para-. Xylene is used in the
manufacture of a number of consumer products, and is also a
component of gasoline and a raw material for synthesis of organic
chemicals.
Xylene was detected in four percent of
highest concentrations were found in the
the former landfill. The values range
J.Lg/kg.
the soil samples. The
soils beneath the cap of
from 3 J.Lg/kg to 27,000
5.2.1.2.
Semi-Volatiles in Soils
Although no semi-volatile compounds were confirmed in soils during
the Data Validation report three tentatively identified compounds
(TIC's) were recognized: disulfoton, chlorobenzilate, and
butylphosphorotrithioate. Levels of disulfoton ranged from 60 ppb
- 430,000 ppb and were identified in four percent of the soil
samples collected. Butylphosphorotrithioate was detected in three
samples at a concentrations ranging from 750 to 7900 ppb.
Chlorobenzilate was not detected in samples collected by ENSAFE,
but was identified in. one split sample collected by the EPA
oversight contractor. Disulfotone sulfone was identified in one
sample at 51 ppb. Disulfoton sulfone is a degradation product of
disulfoton.
Disulfoton (a.k.a. Di-syston) is a colorless, oily liquid (in the
pure state), and the technical grade is brown in color. It is
generally insoluble in most organic solvents. Disulfoton was
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24
produced as an insecticide for mites and aphids on small grain~,
corn, sorghum, cotton, and other field crops.
Butylphosphorotrithioate is a colorless to pale yellow clear liquid
which is insoluble in water. It was produced as a pesticide and
cotton defoliant.
Chlorobenzilate (a.k.a. 4,4'-Dichlorobenzilic acid ethyl ester) is
a viscous liquid sometimes yellow in color, and is slightly water
soluble. It was manufactured as an acaricide. It was approved for
use in the USA in 1969 for application on 11 crops which were
primarily fruits and vegetables.
5.2.1.3
pesticides in Soil
Soil samples collected during the RI have indicated a varied
di'stribution of individual pesticide components. Concentrations
for total pesticides range from below detection limits' to 7170
mg/kg in surface and shallow subsurface soils. For the purpose of
total pesticides, the values indicated represent the summation of
all pesticide components identified during the RI. The primary
pesticide constituents identified were DDT (and its degradation
products), toxaphene, and BHC (including isomers). Contaminant
distribution data have been generated for the primary constituents
identified on the property. Those components comprising a less
significant fraction of the total pesticides identified include
aldrin, chlordane (including isomers), dieldrin, endrin, endrin
ketone, total endosulfans, heptachlor, heptachlor epoxide, and
methoxychlor.
The most significant levels of pesticides identified on the site
were found immediately north, northwest, and/or east of the north
warehouse. The overall levels of contamination generally show a
decrease in concentration with depth from the surface to three feet
below grade. Isolated.hot spots. however, show an increase in
concentrations at the one to two foot interval with subsequent
decrease in concentration again with depth. Individual pesticides
are further detailed below.
Toxaphene
Toxaphene (a.k.a. chlorinated camphene) is produced as a yellow,
waxy solid with a pleasant piney odor. Toxaphene is nearly
insoluble in water., It was used as an insecticide for cotton,
early stages of vegetables (peas, soybeans, and peanuts), and wheat
and other small grains. Current uses are limited to cattle and
sheep dipping (under certain provisions), disinfecting buildings,
and termite, insect, rodent and other pest control (limited
application). Toxaphene has not been produced commercially in the
U.S. since 1982. .
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25
Toxaphene is generally present at the highest concentration in the
pesticide fractions identified at the Site. Toxaphene was
identified in 40 percent of the samples collected and
concentrations ranged in value from 42 ~g/kg (ppb) to 2700 mg/kg
(ppm). Toxaphene data from the RI indicate contamination with the
highest concentrations is found immediately northwest of the north
warehouse, and elevated concentrations were also identified east of
the building.
DDT, DDE, and DDD
DDT (a.k.a. 4,4'-Dichlorodiphenyltrichloroethane) was produced as
colorless crystals or white/off-white powder. It is odorless or
has a slight aromatic odor. DDE and DDD are found as contaminants
(minor fraction) in DDT, and may also be produced through
degradation of DDT. These compounds are non-systemic contact and
stomach insecticides. DDT was used primarily to control insects
capable of spreading malaria, typhus, and other insect transmitted
diseases. Use of these products has been banned in the u.S.
DDT was detected in approximately 61 percent of the soil samples
collected during the RI. The reported concentration of DDT and its
degradation products in soils ranged from 2.3 ppb to 2,800 ppm.
Contaminant distribution data generated during the RI indicate
contamination from DDT is greatest at the surface and decreases
with depth.
BIIC (Lindane) and Iaomera
Lindane is produced as a
slightly soluble in water
organochlorine pesticide.
hexachloride (BHC).
white crystalline powder, and is only
(varies between isomers). Lindane is a
Lindane is the gamma isomer of benzene
All four BHC isomers (alpha, beta, gamma, and delta) were
identified in soil samples collected during the investigation. The
most frequently detected isomer was beta-BHC which was found in
approximately 38 percent of the soil samples. Concentrations of BHC
range from 0.1 ppb - 390 ppm. Again, data indicate a decrease in
concentration levels with increased depth.
Aldrin
Aldrin is produced as tan to dark brown crystals which are
essentially insoluble in water. It was formerly used as an
insecticide, and has been registered as a termaticide in the USA.
The manufacture and use of aldrin have been banned in the USA.
Aldrin was detected in approximately 17 percent of the soil
samples. Values ranged from 1.2 ppb - 800,000 ppb. predominant
soil contamination from aldrin was identified west and northwest o~
the north warehouse.
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26
Chlordane
Chlordane (pure form) exists as a colorless to amber, odorless;
viscous liquid which is insoluble in water. Chlordane was also
produced in emulsifiable concentrates, granules, dusts and wettable
powders (for termite control). It was formerly used as a fumigant
and acaricide, and also as a home and garden pesticide/insecticide.
As of 1983, the only approved use of chlordane in the USA is for
termite control.
Chlordane (alpha and gamma isomers) was identified in approximately
four percent of the soil samples. Chlordane concentrations range
from 15 ppb- 58,694 ppb.
Dieldrin
Dieldrin was produced as white crystals or light tan flakes which
are odorless and insoluble in water. Dieldrin was formerly used to
control soil insects, insects of public health concern and
termites. Its use as a broad spectrum insecticide ceased in 1974
when EPA restricted its use to direct soil injection for termite
control and non-food seed/plant treatment.
Dieldrin was identified in approximately 36 percent of the soil
samples collected during the RI. Dieldrin concentrations range
from 4.6 ppb - 96,000 ppb. Soil contamination was identified
between the warehouse and the former house and in the low lying
areas north and west of the former landfill. Concentrations
decrease with depth.
Total BDdosulfana
Endosulfan (two (2) isomers) was produced as brown crystals
essentially insoluble in water. Its primary application was as an
insecticide for vegetables. Endosulfan sulfate is a degradation
product of endosulfan. .
Endosulfan was detected in approximately 5 percent of the soil
samples collected. Endosulfan sulfate was detected in approximately
13 percent of the samples analyzed. Concentrations ranged from 2.1
ppb 22,000 ppb. The most significant concentrations were
identified immediately northwest of the warehouse. Less
significant contamination was identified in the low lying area
northwest of the landfill. Analytical data indicates that
Endosulfan concentrations have decreased with depth.
BDdrin
Endrin was produced as water insoluble white crystals dissolved in
a liquid carrier (organic solvent). The only uses currently
registered in the US are for cotton and bird perches. It.. is a
persistent insecticide used on field crops to control army cutworm,
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27
meadow voles, and grasshoppers under strict adherence to Federal
regulations on application. Endrin ketone is an impurity in and
degradation product of endrin.
Endrin and Endrin Ketone were identified in soil samples west of
the warehouse and west-northwest of the landfill. Concentrations
ranged from 0.74 ppb - 9,200 ppb. Approximately 12 percent of the
samples collected contained endrin and 16 percent its degradation
product endrin ketone. Concentrations appear to decrease with
depth with the exception of one anomaly from sample 55-3-3.
Heptachlor
Heptachlor was produced as white to tan, waxy-looking solid
crystals which are nearly insoluble in water. It has been used as
an insecticide for termite control, and was also formerly used in
fieldcrops (including corn, citrus, pineapples, cereal, vegetables
sugar beets, nuts and cotton) for pest control (fire ants, boll
weevils) . Heptachlor epoxide is a degradation product of
heptachlor.
Heptachlor was identified in approximately 25 percent of the soil
samples. The concentration of heptachlor and its degradation
products ranged from 1.0 ppb to 68,000 ppb. The predominant area
of. contamination was in the low lying area north and west of the
landfill with some minor levels of contaminant identified. north of
the warehouse.
Methoxychlor
Methoxychlor was produced as a white, crystalline solid dissolved
in an organic liquid carrier. It is essentially insoluble in
water. Methoxychlor has been used as an insecticide for livestock
and poultry, alfalfa, citrus , vegetables, soybeans, deciduous
fruits and nuts, and other crops as well as home use, garden and
ornamental plants, and forests. A common formulation is
Methoxychlor with.Diazinon (1:2 mix).
Four percent of the soil samples collected contained methoxychlor.
Concentrations ranged from 24 ppb - 12,000 ppb. Methoxychlor was
identified in the low lying area north of the landfill and
northwest of the warehouse.
5.2.2
Ground Water
A total of 22 monitoring wells were installed at the Fairfax site
du.ring the RI. Thirteen wells were completed as shallow monitoring
wells and nine wells were completed as deep monitoring wells. All
wells were completed within the upper Eocene aquifer system... The
installation and subsequent sampling of wells during Phase III of
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28
the RI corresponded with the third quarter sampling event of 199i
for the wells installed during Phase II-A.
Chlorinated pesticides and volatile organics were identified in
samples collected from on-site shallow monitoring wells. One deep
well (MW-3) also indicated low levels of pesticides in ground
water. Endosulfan sulfate was detected in MW-5; however, the
quantity was -j- flagged. Four metals were detected in various
wells at concentrations above their respective MCLs and are
discussed below.
The City of Fairfax municipal well (south well) was sampled during
Phases II-A and III of the field investigation. Samples were
co'llected both before and after treatment by a' chlorination
process. No Site-related contaminants were identified in any of the
samples collected from the municipal well samples. The north well
field, which is located approximately one mile north of the Site,
was not sampled. '
5.2.2.1 Volatile Organics in Groundwater
Groundwater samples collected throughout the RI have identified low
levels of various fractions of the volatile compound list. The
most commonly detected were acetone and carbon disulfide; however,
data validation suggests that these and other minor constituents
are laboratory artifacts. Other constituents identified include
benzene, chlorobenzene, chloroform, 1,2-dichloropropane,
ethylbenzene, methylene chloride, and xylene were identified.
Acetone
Acetone was identified in groundwater samples from all site
monitoring wells except for MW-1, MW-10, 20, 21, 22, 23, and 24.
Additionally, acetone was identified in the raw (before
chlorination) and finished (after chlorination) water samples
collected from the Fairfax municipal well. As mentioned previously
acetone is considered to be a lab artifact. Concentrations range
.from 3 ~g/l (ppb) 150 ~g/l (ppb) identified in numerous
groundwater samples.
Carbon Diaulfide
Groundwater samples from all site monitoring wells except for MW-1
and MW-3 identified varying levels of carbon disulfide. The
untreated city water was also positive for carbon disulfide.
Concentrations range from 3 ppb - 130 ppb. Carbon disulfide was
only detected in eight samples collected during all sampling events
subsequent to Phase II-A. Many of the reported concentrations were
-j - flagged (estimated values). In addition to the Phase II-A
wells, carbon disulfide was identified in monitoring wells MW-18,
MW-20 and MW-22 installed during Phase III of the RI.
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29
Methylene Chloride
Methylene chloride was detected in groundwater samples collected
from monitoring wells MW-1, MW-2, MW-4, MW-5, MW-8, MW-10, MW-12~
MW-14, MW-19 and the finished city water during the investigation.
Concentrations range from 1 ppb -.7 ppb. Once again, many of the
reported concentrations were 8j8 flagged.
Benzene
Benzene was identified in groundwater samples collected from MW-12
during Phase. II-A, the first quarterly sampling event under Phase
II-B, and the December sampling event. Concentrations of benzene
varied from 34 ppb to 52 ppb in the three respective sampling
events. Benzene was detected in MW-4 during two sampling events at
concentrations of 5 and 6 ppb. During Phase III benzene was
detected in MW-14 at 37 ppb.
Chlorobenzene
Chlorobenzene was detected in groundwater samples collected from
monitoring wells MW-4, MW-6, MW-8, MW-12 and MW-14. Concentrations
ranged from 2 ppb - 17 ppb.
Chloroform
The finished water sample collected from the City of Fairfax
municipal water well detected chloroform at 2 ppb. This occurrence
probably results from the City's water chlorination process. No
Chloroform was detected in the municipal well system during Phase
III sampling.
1,2-Dichloropropane
1,2-Dichloropropane was detected in samples collected from
monitoring wells MW-8, MW-12, and MW-14 in the quarterly sampling
events. Concentrations range from 6 ppb to 28 ppb.
Bthylbenzene
Ethylbenzene was detected in samples collected from monitoring
wells MW-4, MW-8, MW-12 I MW-14, MW-19, MW-22, and MW-24 during
sampling events completed to date. Concentrations range from 2 ppb
- 190 ppb.
Xylene
Groundwater samples collected from monitoring wells MW-4, MW-6, MW.,..
8, MW-12, MW-14, MW-19, MW-22 and MW-24 exhibited elevated levels
of xylenes. Concentrations ranged from 5 ppb - 2000 ppb.
Monitoring well MW-4 contained the highest concentration.
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30
5.2.2.2
Semi-Volatiles in Ground Water
Disulfoton was identified in monitoring wells MW-4 and MW-12 during
two of the groundwater sampling events. Concentrations of 78 ppb
and 110 ppb were reported in MW-4 while concentrations of 3 ppb and
4 ppb were reported for MW-12. Both of the concentration values for
MW-12 were reported as estimated concentrations (i.e., 8j8
flagged). Butyl phosphorotrithioate was identified in MW-15 during
Phase III at a concentration of 49 ppb, and was likewise 8 j 8
flagged.
5."2.2.3
Pesticides in Groundwater
Monitoring well samples indicate that elevated levels of pesticides
exist in shallow groundwater. Contaminants identified .appear to
consist primarily of toxaphene, DDT (and its degradation products) ,
BRC (including isomers) and dieldrin. Those components comprising
a less significant fraction of the total pesticides identified
include aldrin, chlordane (including isomers), endrin and endrin
ketone, total endosulfans, and heptachlor and heptachlor epoxide.
Methoxychlor, which was identified in soil samples, was not
identified in groundwater.
Toxaphene
Toxaphene contamination comprises the most significant
concentrations of the pesticides fraction identified in groundwater
at the Site. Toxaphene was identified in groundwater samples from
monitoring wells MW-4, MW-6, MW-8, and MW-10 collected during the
Remedial Investigation. Concentrations ranged in value from 9.9 ppb
120.0 ppb. The laboratory did not identify toxaphene in
groundwater samples collected during the March 1991 sampling event;
however, toxaphene is believed to be present in MW-4, MW-6, and MW-
10.. Internal validation and assessment of chromatagrams indicates
the probable presence of toxaphene in these wells~' Due to severe
matrix interferences in these samples, however, toxaphene
quantification was not possible. The maximum concentration of
toxaphene was detected in MW-8.
The Maximum Contaminant Level (MCL) for toxaphene in groundwater
were established at 3.0 ppb.
DDT, DDB, and DDD
DDT, DDE, and DDD were detected in groundwater samples collected
from monitoring wells MW-4, MW-6, MW-12, MW-14, and MW-22 during
the RI and ranged in value from 0.045 ppb to 2 ppb. An MCL has not
been established for DDT, or its metabolites DDE and DDD.
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31
BH'C (Lindane)
Lindane and its BHC isomers (alpha, beta, and delta) were
identified in groundwater samples collected from monitoring wells
MW-3, MW-4, MW-6, MW-8, MW-10, MW-12, MW-14, MW-16, MW-18, MW-22 ,
and MW-24. Concentrations of BHC range from 0.024 ppb - 42.0 ppb.
The MCL for lindane has been established at 0.2 ppb.
Dieldrin
Dieldrin was identified in groundwater samples from monitoring
wells MW-4, MW-6, MW-8, MW-10,' MW-12, and MW-14 in the first
quarterly sclmpling event. Subsequent quarterly sampling events
identified dieldrin in monitoring wells MW-6, MW-8, MW-10, MW-12 ,
MW-14, MW-16, MW-18, MW-22, and MW-24. Concentrations range from
0.024 ppb.- 5.5 ppb.
An MCL has not been established for dieldrin.
Aldrin
Aldrin was detected in groundwater samples collected from
monitoring wells MW-4, MW-6, MW-8, and MW-12. Values ranged from
0.22 ppb - 7.9 ppb. The maximum concentration was detected in MW-
4 . .
An MCL has not been established for aldrin.
Chlordane
Chlordane (alpha and gamma isomers) was identified in groundwater
samples collected from monitoring wells MW-4 and MW-12. Chlordane
was detected in MW-4 during the Phase II-A sampling events at 1.2
ppb. Chlordane was identified in MW-12 during Phase II-A, and both
Phase II-B sampling events at concentrations ranging from 0.31 ppb
- 1.3 ppb. The MCL established for chlordane is 2.0 ppb.
Total Endo8ulfana
Endosulfans were detected in monitoring wells MW-4 and MW-6 during
the Phase II-A at concentrations of 1.8 ppb and .021 ppb
respectively. Phase III groundwater sampling indicated elevated
concentrations of endosulfans from monitoring wells MW-2, MW-5, MW-
14, and MW-24. Concentrations ranged from 0.054 ppb to 0.62 ppb.
Endrin
Endrin and endrin ketone were identified in groundwater samples
collected from monitoring wells MW-4, MW-6, MW-8, MW-10, MW-12 , MW-
18, MW-22, and MW-24. Concentrations ranged from 0.3 ppb - 2.1 ppb
for endrin, and from 0.064 ppb - 18 ppb for endrin ketone. The MCL
for endrin is 2.0 ppb.
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32
Heptachlor
Heptachlor and heptachlor epoxide were identified in monitoring
wells MW-6 and MW-12. The concentrations identified were 0.12 ppb
for heptachlor and 0.57 ppb for heptachlor epoxide. Groundwater
samples collected during Phase III of the RI did not show'
detectable quantities of heptachlor or heptachlor epoxide.
MCLs have been established at 0.4 ppb and 0.2 ppb, respectively.
5 ."2 . 2 . 4
Metals in Groundwater
The metals analyses conducted during the Phase II-A sampling event
did not provide conclusive evidence that metals contamination of
ground waters was a result of releases from the Site. Most metals
in groundwater were detected at concentrations below detection
limits or at levels comparable to background concentrations.
During subsequent Phase II-B and Phase III groundwater sampling
events beryllium, chromium, cadmium, and lead were detected in
samples at levels which exceeded their respective MCLs.
Beryllium
Beryllium was identified in monitoring wells MW-4, MW-8, and MW-20
at concentrations of 6 ppb, 9 ppb, and 5 ppb respectively. The MCL
for beryllium is 4 ppb. The detection of beryllium at
concentrations above MCLs was a one time occurrence in each of the
wells; therefore its presence does not appear to be significant.
Chromium
The presence of chromium was detected in monitoring wells MW-4, MW-
6,' MW-20, MW-23, and MW-24 at levels which exceeded the MCL of 100
ppb. The maximum concentration reported was 415 ppb which was
detected in MW-20. .
Cadmium
Cadmium was identified in MW-20 during both the September/October
1991 and December 1991 sampling at a concentration of 10 ppb. The
MCL for cadmium is 5 ppb.
Lead
Lead was detecte:d above the action level of 15 ppb in samples
collected from monitoring wells MW-12, MW-20, MW-23, and MW-26.
Lead was most frequently identified above the action level in MW-
12.
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33
Table 5
.
- Tabl. 4-22
p..1ic:idea ISurta~ Water/Sedimem
"he.. U-A."'n.S. III
NUMBER OF . NUMSER OF ;
PARAMETER 'MATRIX SAMPLES' .HrTS RAHGElppbl MEAN(ppbl
alpha - SHC Surface W8ter 2. - .~.. 0 - -
Sediment 10 2 0.1-60 30.5
beta - SHC Surfaca Water 2 2 0.57-1.2 1
Sediment 10 3 0.1.500 171.7
gamma - SHC Surface Water 2 0 - - I
Sediment 10 2 0.1.67 33.6 I
delta. SHC Surface Water 2 I - 0.28
Sediment 10 0 - -
Aldrin Surface Water 2 0 - -
Sediment 'O 1 - 990
Dieldrin Surface Water - 2 2 0.~:.6.2 3.5
Sediment 10 1 - 3200
4.4' ODD Surface Water 2 2 0.0':5.0.23 0.2
.
Sediment 10 9 18-3400 437
4,4' DOT Surface Weter 2 1 - 1.2
-
-' -
...,..: ~ ~
Sediment 10 7 5.3':5700 862.9
4,4' OOE Surlace Water 2 0 - -
_. Sediment. ;... 10 8 9.8.280 80
Endrin Ketone Surfaca Watar .2 2 0.35'1.4 1
Sediment 10 0 - -
Heptachlor Surface Water 2 0 - -
Sediment 10 2 2.1-25 13.6
Toxaphene Surface Water 2 1 - NOT
. .. QUANTIFIED
Sadiment 10 2 78-42000 21039
Gamma ' Surface Water 2 -. 0 - -
Chlordane
Sediment 10 2 18-900.7 459.4
Alpha Surface Water 2 0 - -
Chlordane
Sediment . 10 1 - 443
Endrin Surface Water 2 0 - -
Sediment 10 1 - 1,6
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34
5.2.3
Surface Water and Sediments
Sediments in the wetland areas located in the northern portion of
the Site were found to be contaminated with semivolatile chemicals
and pesticides. Table 5 summarizes the findings of the RI with
respect to contaminated sediments. There are no chemical-specific
ARARs for sediments, but the levels of contamination found in the
RI exceed concentrations that have been shown through toxicological
research to have an adverse impact to aquatic life due to toxic
effects of these contaminants. This research is summarized in the
National Oceanographic and Atmospheric Administration (NOAA)
publication . entitled The Potential for Bioloqical Effects of
Sediment-Sorbed Contaminants Tested in the National Status and
Trends Proqram, NOAA Technical Memorandum NOS OMA 52, August, 1991-
The pattern and distribution of contamination in the sediments
indicate that the primary source of contamination is the landfill
that was placed partially in the jurisdictional wetlands. Sediment
contamination also extends into off-site drainage pathways for
surface waters. The sediment contamination found in both on-site
and off-site locations poses an unacceptable risk to environmental
receptors.
On-site surface waters were found to have been contaminated with
pesticides at levels which exceed Ambient Water Quality Criteria
(AWQC) for the protection of aquatic life. Federal AWQC have been
established under the authority of Section 303 of the Clean Water
Act for the purpose of establishing protective guidelines for
ambient water quality. AWQC as developed by EPA are identified in
Section 121 of CERCLA as amended by SARA as chemical-specific ARARs
for NPL sites. In addition, the AWQC have been adopted by the
State of South Carolina as ambient surface water quality -standards,
and are therefore ARARs for the Site. Table 5 also summarizes the
findings of the RI with respect to surface water contamination at
the Helena Chemical Site. The surface water contamination
identified as part of the RI also poses an unacceptable risk to
environmental receptors in the on-site wetland areas. and iz:1
drainage pathways leading off-site.
6.0
SUMMARY OF SITB RISKS
A Baseline Risk Assessment was conducted to evaluate the risks
presented by the Helena Chemical Superfund Site to human health and
the environment, under present day conditions and under assumed
future use conditions. Currently, there are no residents living on
the Site and only a few residents residing close to the Site.
There are no potable water supply wells on the Site, although there
is a municipal water supply well located less than one-quarter mile
away. Information gathered from census data regarding population
trends in Allendale County and surrounding areas suggests that
future land use will remain commercial and industrial, with little
potential for residential use of groundwater as a potable water
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35
source. The Site was evaluated, however, under residential
exposure scenarios, including exposure pathways involving the use
of shallow ground water as a potable water supply source. These
exposure scenarios correspond to potential future use of the Site
for residential development.
Under the current land use scenario, potential human receptors at
the Site include residents in the vicinity of the Site who may be
occasional Site trespassers, and workers on the Site. The Site is
surrounded by residential, agricultural and light industrial areas.
Beyond these areas immediately surrounding the Site (including the
City of Fairfax), the local area is not densely populated, and
consists primarily of agricultural land and forests. The most
likely potential human receptors under the current land use
scenario are workers and occasional trespassers. No private
drinking water wells were identified either on-Site or immediately
downgradient from the Site, and no users of surface 'water for
potable water supplies were identified downgradient from the Site.
Under current land use, the Reasonable Maximum Exposure (RME) is
represented by the individual worker or Site trespasser who may be
exposed by direct contact and incidental ingestion of surface soil
and stream sediments.
Potential environmental receptors under the current land use
scenario include the plants and animals at the Site. Site
features, including the small unnamed stream and wetlands adjacent
to the Site, and nearby wooded areas and open fields, provide a
variety Of habitats. No unique or critical habitats have been
identified at the Site, and no vegetative stress is evident based
upon site visits by regulatory personnel. No threatened or
endangered species have been observed at the Site or in adjacent
areas.
Future land use for the Site was considered to include potential
development of the area as residential property. This potential
land use scenario is considered to be that which would result in
the greatest degree of risk to human health should the Site remain
unrernediated. The RME under a residential land use scenario is
assumed to be an adult person or child living on the Site property
and drinking potable water obtained from a private well drilled
into the Barnwell Formation. Under the future land use scenario,
environmental receptors would likely be more limited than at
present, since residential development of the property would in all
likelihood involve the elimination of the wetland and forested
areas on and adjacent to the Site.
EPA has determined that the elevated levels of pesticides in the
soils and ground waters at the Site pose the primary hazard to
human health at the Site. In addition, the elevated levels of
pesticides in the sediments and soils located in the wetland areas
adjacent to and downstream of the Site pose a hazard to
environmental receptors inhabiting those areas. Primary exposure
-------
36
pathways for humans are incidental dermal contact with and
ingestion of contaminated soils, and ingestion of contaminated
ground water. Air transport of particulate matter contaminated
with Site-related constituents of concern is not considered to be
a significant risk to human health because the contaminated soils
are generally in vegetated areas and the most heavily contaminated
soils have been removed prior to this time. Air sampling results
conducted during the Remedial Investigation indicated that airborne
contamination was not present above levels that would pose a
significant risk to human health.
EPA has established in the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP), 40 CFR Part 300, a range of 1 X
10.-4 to 1 X 10-6 as acceptable limit~ for excess lifetime
carcinogenic risks. Excess risk within EPA's acceptable limits
means that any individuals exposed to Site conditions Under the
assumed exposure scenarios will run a one in ten thousand (1 X 10-4)
to a one in one million (1 X 10-6) increased chance of developing
cancer. Under the "No Action" scenario, (assuming the Helena
Chemical Site is left as it is now) the estimated carcinogenic risk
for current land use is 8.0 X 10-5. The estimated excess cancer
risk calculated for the future land use scenarios at the Site is
2.6 X 10-4. These calculated risks for the future iand use scenario
exceed the acceptable risk levels established by EPA and are based
on the assumption that no cleanup activities will have occurred.
EPA has also established acceptable exposure limits based upon non-
carcinogenic health effects. A Hazard Index (HI) of 1.0 or greater
has been established by EPA as the criterion defining unacceptable
levels of exposure for non-carcinogenic health effects. The HI is
the ratio of exposure levels resulting from site conditions to
acceptable exposure levels (ie., exposure levels that result in no
adverse health affects) for any given contaminant. The HI for
potential non-carcinogenic effects under the current land use
exposure scenario is 0 .3 . The associated Hazard Index for
non-carcinogenic effects under the future land use exposure
scenario is 8.6.
Actual or threatened releases of hazardous substances from this
Site, if not addressed by the preferred alternative or one of the
other active measures considered, may present a current or
potential future threat to the public health, welfare, or the
environment.
6.1
CONTAMINANTS OF CONCERN
Numerous chemical contaminants were identified in site media during
RI Phases II-A, II-B, and III. Tables 6, 7, 8, 9, and 10 provide
a summary of those contaminants which were evaluated or considered
for evaluation during the Baseline Risk Assessment process.'- In
Tables 6-10 the term -hit. or .hits. refers to positive results of
-------
37
Table 6
I TilbJ.A" " ,I
... , ...
... Summ8IYof Soil ,p..1icidaConc.mr.dOne..
HCFSC :Site ..,.,..
. i.) .., ::..i.:. ,:,:.,... ):.:::'. ....: .. Numb.'uf. ..... ... .. ~arige
....
. .P..me.:,' .. . ".'.
::". ..S~:~i.. .sanipi.."".:: .: . NiIrnb8t,of HitS.,.,,:. ,(pJ)b} Maan Ippb} .
Aldrin Total 261 36 1 .2 - 800000 27100
Surface 162 6 1.4 - 8100 1690
alpha-SHC Total 261 32 2.1 - 390000 12300
Surface 162 6 4.4 - 1800 630
beta-SHC Total 261 62 4.9 - 270000 9900
Surface 152 15 4.9 - 6200 750
delta-SHC Total 261 22 4.1 - 210000 19000
Surface 152 4 5 - 1500 380
gamma-SHC Total 261 19 4.2 - 220000 1 1700
Surface 152 4 5 - 67 34
4,4'-DDT Total 261 124 6.1 - 2800000 31000
Surface 152 41 8.6 - 220000 19200
4,4'-DDE Total 261 66 0.74 - 21000 1100
Surface 152 31 4.6 - 15000 910
4,4'-DDD Total 261 72 2.3 - 750000 16800
Surface 152 22 4.0 - 60000 6400
Dieldrin Total 261 79 3.7 - 96000 3500
Surface 152 21 4.6 - 44000 2700
Endosulfan II Total 261 13 23 - 7100 660
Surface 152 4 23 - 7100 1820
Endosulfan Total 261 33 2.1 - 22000 1040
Sulfate
Surface 152 16 2.6 - 22000 1920
Endrin Totsl 261 26 6.8 - 1600 390
Surface 152 ,., 9.1 - 1600 550
Endrin Ketone Total 261 36 2.1 - 9200 630
Surface 162 12 6.3 - 1200 220
-------
Table 6
r
..........
. ..Piir8meter'......
Heptechlor
Heptachlor
Epoxide
Methoxychlor
Toxaphene
elpha-Chlordane
gamma-
Chlordane
38
(continued)
..,.0.;...,......
."T.bI...7-'.. ..
.. Summary ofSoIPeeticid..COncenntione....
. ..HCfSCSit. .... .
..).... .... . ..'...
.. .. ...Number.of.
... ..... .......... ....S*,"pI.. ..
...
:..1.
...
Nurribei.~f.~ft. < I~=l
. . "'"
. . . . .... .
. Sol. cr...
. .
Total 261 11 6.1 - 68000
Surface 152 3 19 - 35
Total 261 9 2.4 - 29
Surface 152 4 6 - 29
Total 261 10 24 - 12000
Surface 152 6 24.12000
Total 261 62 78 - 2700000
Surface 152 22 78 - 350000
Total 261 4 15.9600
Surface 152 1 -
Total 261 6 16-14000
Surface 152 4 1 6 - 66
...~~«P..j;
3300
66000
43300
2500
2600
9300
26
15
20
2050
15
39
;1
-------
39
Table 7
...,., ..
.,.'."i'. ...
.,..;,:/
.'...u
"..,;:. ".::,,:/.,.....
....
.. ..... :.... 'T8blei7~2 .
~~f!1~1!ij'9f.Soil.Semivolatile ..Concentrations
".:::.,::::,::/}:,:,r.::::"HCFSC::Sit8'... ... ...
i:.>'.
.
..,.. ...
.',.:
.,.....::..:: ::.;':
..
... ".- ...
... ... ',"... ....
... . ..." ... ...
:'i!ji~~;~~~::..
:')\~,",pies:...::
..' ..
.. ..
. n'''' .
.. .... . .. -.
...... ....' .
.. ,-..-""'"''
..... ........
",',',',"',',",",",',.,',",',
...... . "...".
"," '....
',.',',
..
...
.. .}:..;;;;..:....
.... .....
... .....
-.'" ...........
... '....' . ... .
........... ..,."
..... ,- .' ,-
,', ,",.',' ',' ','. ,',",",.'.'
. ... .""",,,'
:,::::':Soi,;~jisj:,::;::
. .';',-. "'":'.....':: ....
...... ... . '" .. .
:::N'Omberof:} , . <.:u"'" .". '.. .......,..::,..:...,j,:,..,.;,..,.:,.M.C...p8p8b..I1)' ..,':.',:,..:,
.... .. Hits:.." .' . ::."'66oe:>.
Chlorobenzilateb
Total 261 12 60-
430000
Surface 152 1 -
Total 261 3 750.
7900
Surface 152 0 -
Total 261 0 -
Surface 152 0 -
59400
Disulfoton..b
Tributylphoshoro-
trithioateb
97
3200
-
-
-
Notes: Only disulfoton of the semivolatile SAS compounds (originally Tentatively Identified
Compounds) were detected in site surface soils.
a
One disulfoton sulfone hit (51 ppb) was identified during Phase II-A. This hit occurred as a
Tentatively Identified Compound with estimated (W JW flag) concentration. This hit was not
used to compute the average disulfoton concentration.
b
Compound identified in a limited area in immediate vicinity of landfill.
-------
Table 8
1:-
" '
'''.'.
.. . ." ..
P:.ilim..ter."
Benzene
Chloroform
Ethytbenzene
Methytene Chloride
T ofuene
Acetone
2.Butanone
Xylenes
Carbon Disulfide
Trichloroethytene
Styrene
1.2-Dichloroethene
T etr.chloro.thene
1.2-Dichloropropene
Chlorobenzene
40
..
Table 7-3
Sutnmary 'af' ScII:VolatIIM 'Concentrations
'" .." """"',, :'HCFSC'alte ',' ",', ::;':;' ,
;t
,"..".","."' ,",'.'.".
'$o'~;
Totel
Surface
Tota'
Surfece
Total
Surface
Tote'
Surf.ce
Total
Surface
Totel
Surface
Total
Surface
Totel
Surfece
Tot.1
Surfece
Total
Surface
Total
Surface
Total
Surface
Totel
Surface
Total
Surface
Total
Surface
..".', ",',",". . .. ..:..:.. ,': -"'","
Nu.r.i;;fSa~':iNuInb.r of Hit.,'
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
210
151
119
.. Rang.;
6
3 - 1300
o
-
5
1 - 11
2
2 - 11
7
3 - .100
o
-
80
2 - 140
39
2 - 140
17
1 - 120
4
1 .89
2-13000
69
2 - 13000
31
1 - 36
13
3 - 32
9
3 - 27000
1
-
4
12.48
3
19 . .8
2
24 - 210
o
-
2
-
o
-
2
2 - 12
1
-
2
11 - 240
2
11 . 240
2
15.75
o
-
.
5 . 8000
o
-
,I
.M..~(ppbI.
223
-
4
7
1260
-
20
30
32
35
320
600
12
13
4250
3
30
35
117
-
2
-
7
12
130
130
45
-
2300
.'
-
-------
Table 9
I '.
"....
".':..' '.:. c
.. ":.::':':'.':'
..
..
:'. .Parameter..: CRCI...
Aldrin 0.05
alpha-SHC 0.05
beta-SHC 0.05
delta-SHC 0.05
gamma-SHC 0.05
4,4'-DDT 0.1
4,4'-000 0.1
4,4'-DDE 0.1
Dieldrin 0.1
Endo6ulfan II 0.1
Toxaphene" 1.0
Endrin 0.1
Endrin Ketone 0.1
41
. .
..." .
. . .' . .....:.t.~.:7;4.. ..."..,
Summary:~tGraundw.terCon~lnant8.
. ".': ..... .-:. ...-..:...., ".'. . . :HCfSC':'&tt8.::, .'. . ..:.:..
...
. ..
..
.. .
~ampliOgD.t.;:;: ':'::'1~='
October 91 2
Deoember 91 2
Ootober 91 9
Deoember 91 8
October 91 8
December 91 7
October 91 7
December 91 5
October 91 7
December 91 6
Ootober 91 1
December 91 1
October 91 3
December 91 1
October 91 2
December 91 0
October 91 9
December 91 7
October 91 1
December 91 0
October 91 0
December 91 1
October 91 0
December 91 1
October 91 7
December 91 6
, "
..,:. : ..:{
:,:~~~f;
.. ,
, ,
..,
. ..
. - . . . .
......' -
. \\;:~~'~'::;:2.3/::\:i:
,:\:0'.'66:'. .1.2::::::::::,:.
(OW'-'.18::i')::
''':0".11 - 31:)
0;;l6 - 26 ..
:JM9 - 26..,
d>:.Q2.4- 5:7:::-
:A;M)9,4 . 1 ;2}:\:
.. ....
. .".
. .....
u..' ..
,O~t:l,6:6}::
"
': '::()~23':~ ,2.2'::::,.,.
"".':"':','; "'.,J2KL
,:.,:i::::<:..::.;" ~
j)~Q46~ 0.5S:::)
:::/,:::;.,.",.. . :"::':':
.:,'.::': : .::.:::':{:
.:~;'Qti1- 2.0}{
;::{)]
".' "',
::.:::::::'::::
-:':::41%:i4":3:~::i!:::,
:::;:::{i#3:;.S:s:;iI:!::
":::\::;:"",.'.,\::;
)::;::) "::W
..::\!
...',}}
,::"::,:.",,,,
\:;.
i~0~.~J
::::::::::~j~1;':1+:::[i:::!:::
..
'.';
: Mean'"
:(ppbf
:01 HIta '
..
..
..,
1.59
0.93
2.78
6.72
5.42
4.70
1.25
0.62
1.47
0.91
::'::"
0.45' :
1.2)":
..:,:.::,:'
0.26;<
2.10 ":',:::.:.
1.03 .:':"
::':..'
,:':;.:::
0.99 :[::::,:
2.70 I:::::.:'
0.62 }:{'
- i::;:::,'
?::'.
36.0 1::/\:;::::,::.
-
0.3
6.15
4.15
,,"
::. ,
:.:.',
Cf#'~
", . ....',',,',
":s5%ci~,*;:,::
Confidence: :
:Umfi Mea" .::::::.
::Ippbl~:""
0.266
3.44
3.74
1.06
0.69
0.175
0.24
0.21
1.11
0.13
8.29
0.081
2.98
..
-------
42
Table 9
(continued)
. Table-7-4 ... . ... ... . .
.."Umm8ry of Groundwat.COn18minant8 ....
::. .. . HCFSC:Sit.... .......:.... ......
"P.
..... """0 ""'" ..."
.,",.,",",.. ,'.",'..'.', ",".".
<:~~tWpiifiOD.te} .
October 91
3
December 91
o
Benzene
5.0
October 91
2
5.85
December 91
Disulfoton
5
October 91
o
9.12
December 91
2
TBPT
10
October 91
o
10.7
December 91
Chromium
October 91
21
. . ... . .
" . 'd..
" .n.. ...
.. ... .. . .
...3.9.. ."'1. 5......
::::: ~ -;:~;"~::' ::::;::::';"
69.75
December 91
14
. . ....
.. . ''''.. .
....to;0.;291;1:
51.9
Lead
October 91
24
.. "'...
". ..... n...
. .... """...
"H. ... '.
.. ..0.. ., .. .. ...
....: ;.,.:.:.:.4
-------
Table 10
43
... .. . Table 7-& ..... .
.PMticid..,(SldlliceWliterlSedmenU..;. .
...,.:...:... .... PIia..,II-AHr;;a;til.'.,',.,:., .'.'.;';.. .
. . ... .
P#!o.RAMETER
.. . .
. . .
'elpha-SHe: .
. .. ... ..
..... ..".
::beta:":.SHC
'. .'
. 'Q8~m'~ -. SHC':'
delta. SHC:
.:.:.;.:.;:.;.:.:.:.;.; ,"
:.~:.~.:~.:...'...;'.".'}'"...'. i\).:'./, . .
".'.'.'.','.".".",",','.'..',
.:.~,~...:,.;.,.~,..;,.;.::;.;;.,;..;;;..'::.:.,;....;0."...;;.J;..<1:....:....;ri!';\:?';;;;':;';;';:':
:;,::::':;';:;:::;:;:;:;:;:;:::::;:;:;:::::;:;:::
""'"':"':':';':';':':':':":':':';'::'::".'::
""
. . .
.-. ....
. . , . .' . . . . .. .. ..
: ./;ir"'.~MBar.OF»':' . ..:).UMBER:::O.F:':::~
..:..;;.:. SAMPLfS;:.::. ... HITS::;..
. MEAH(ppb}
. .
. .....' ....
. ; RAHGElppb)
...
. MATR1X :
Surface Water 2
Sediment
9
Surface Water 2
Sediment
9
Surfece Water 2.
Sediment
9
Surface Water 2.
Sediment
9
Surface Water 2
Sediment
9
Surface Water 2
Sediment
9
Surface Water 2
Sediment
9
Surface Water 2
Sediment
9
Surface Water 2
Sediment 9
Surface Water 2
Sediment
9
Surface Water 2
Sediment
9
Surface Watar 2
Sediment
9
Surface Water 2
Sediment
9
o
60
2 0.57-1.2
2 1 6-500 257.5
o
67
0.28
o
0
2
990
0.41.6.2 3.5
3200
0.045-0.23 0.2
18.3400 437
1.2
14-6700 1207
9.8-280 80
0.35-1.4
2
9
5
o
8
2
o
o
25
NOT
QUANTI RED
2 78.42000 21039
o
2 18-67 42.6
-------
44
analyses. Many of the contaminants identi fied during the. RI
occurred at low frequency and/or in very low concentrations
relative to the practical quantification limit for each compound.
The selection of contaminants that would be fully evaluated during
the Baseline Risk Assessment in order to quantify Site risks were
selected in accordance with guidance as contained in the document
Risk Assessment Guidance for Superfund (RAGS), EPA/540/1-89/002,
12/89. The selection process included the following criteria: (1)
the chemical has demonstrated significant toxicity to animal life
in published reports, (2) USEPA health-based numbers can be
obtained for the chemical, (3) whether its occurrence is
significant,. based on frequency, concentration and exposure
potential, in regard to the total risk posed by the Site. The
rationale used for selection of the evaluated contaminants and for
eliminating the other contaminants is provided in the. following
discussions.
The selected contaminants of concern for the baseline risk
assessment are shown in Table 4. pesticides were the primary
hazardous contaminants detected. In addition, a limited number of
semi-volatile, volatile, and inorganic parameters were identified
and will be carried through the baseline risk assessment process as
explained below. Only Contract Laboratory Program (CLP) data were
used for the evaluation of baseline risk at the Helena Chemical NPL
Site.
In soils, DDT (plus DDE and DDD), BHC (all isomers), toxaphene and
dieldrin were the most frequently detected and generally were found
in the higher concentrations. Aldrin, endosulfan sulfate, endrin
and endrin ketone were the next most frequently detected
pesticides. Endosulfan, heptachlor, heptachlor epoxide,
methoxychlor, and chlordane were the least frequently detected.
Disul foton and tributylphosphoro-trithioate (TBPT,
butylphosphorotrithioate) were also detected infrequently, but were
nonetheless evaluated as part of the BRA. Due to the low frequency
of detection and the relatively low concentrations of heptachlor,
heptachlor epoxide and chlordane (both isomers) found in site
soils, these compounds were not evaluated as part of the BRA as it
was determined that they would not contribute significantly to the
overall risk posed by the site. This approach is consistent with
the process for eliminating compounds from further consideration as
outlined in RAGS. Endosulfan sulfate and endrin ketone are not
lis'ted in EPA databases which contain Agency reviewed toxicity
data, and as a result the reference doses (RfD's) of their parent
compounds (endosulfan and endrin, respectively) were used to
compute the risk posed by these compounds. This procedure provided
a conservative estimate of risk (or hazard index) .
A large number of inorganic parameters were detected in soil
samples. No inorganic contamination associated with site
activities was found, however, in soils at a frequency and/or
-------
45
concentration sufficient to warrant consideration as a contaminant
of' concern.
Site-related contamination was identified in the surface water
samples gathered during the RI. An evaluation of this data
indicates that pesticides are the only hazardous substances
detected at significant concentration and frequency in this medium
to warrant further consideration. Due to the intermittent nature
of the surface water on-site, this medium was not considered a
significant pathway for direct human exposure. .
In groundwater, aldrin, BHC (all isomers), DDT (plus DDE & DDD) ,
dieldrin, and endrin ketone were detected in the highest
concentration or frequency, and represent the contaminants of
concern from the groundwater perspective. Other detected
chlorinated pesticide compounds included endosulfan II, endrin,
toxaphene, endosulfan sulfate, and heptachlor epoxide. With the
exception of heptachlor epoxide, these compounds were also
evaluated in the Baseline Risk Assessment (BRA). Heptachlor
epoxide was detected in one groundwater sample during Phase II-A.
It has not been detected in any other sample during subsequent
groundwater sampling events. As a result, heptachlor epoxide was
not considered a contaminant of concern for the groundwater
pathway. Heptachlor epoxide was therefore not evaluated as part of
the BRA process. TBPT was also detected in one groundwater sample
during the 3rd Quarter 1991 groundwater sampling event. Disulfoton
was detected in two groundwater samples from the 4th Quarter 1991
sampling event and was evaluated as a contaminant of concern in
groundwater. Benzene, lead, and chromium were also detected in
groundwater samples. The frequency of detection and concentration
for these parameters was generally higher than for the pesticide
compounds and they were evaluated due to their potential
contributions to overall risk (or hazard index).
Carbon disulfide was not consistently detected between RI phases.
As a result, carbon disulfide results were attributed to laboratory
artifacts, and were not evaluated further. Although bis (2-
ethylhexyl)phthalate (BEHP), acetone, methylene chloride, and 2-
butanone were identified in a significant number of samples, they
were not evaluated as contaminants of concern. These compounds are
conunon exogenous contaminants attributable to sampling methods
and/or laboratory artifacts, and are not related to current or
former site operations.
Numerous polynuclear aromatic. hydrocarbons (PAHs) and phenolic
compounds were identified in soil and groundwater during RI Phase
It-A. These compounds were detected at low frequencies and at
concentrations at or near their respective practical quantitation
limits. Subsequent to Phase II-A, the semi-volatile contaminants
of concern were limited to tentatively identified compounds (TICs)
identified during Phase II-A. The TICs were disulfoton, TBPT, and
chlorobenzilate. As a result, the BRA focused on the TICs and
-------
Figure 5
.,.
.,
., ."
'.~. .
46
,"
""...---~.......,
, . .' ,":RgW'8 7.3
~:~-==~a~:erm"
",'.. 'HCFSC Site Soia .
FutweSft6R..ldem. and CUrrent Site Worken
FUTURE SITE RESIDENTS
SOIL INGESTION PA THWA Y
Age-adjusted Ingestion Factor (IF ...u.-;J
IF ...,.OJ (mg-yr/kg-day) = !.B...u""~",,,, + IR~"""~1~7';!1
BW......
where:
IF...,...
BW.......
BW...7,.,
ED,,,,,,,
ED...7>JI
IR...,.......
1R_,,,7'JI
IF ...,.OJ
BW...7.;!1
age-adjusted soil ingestion factor (mg-yrlkg-day)
average body weight from ages 1-6 (kg)
average body weight from ages 7-31 (kg)
exposure duration during IIges 1-6 (yr)
exposure duration during age8 7-31 Iyr)
ingestion rate of soil aga 1 -6 (mg/day)
ingestion rate of soil age 7-31 (mg/day)
age-adjusted ingestion factor (mg-yr/kg-day)
DERMAL CONTACT PATHWAY
Age-adjusted Contact Factor (CF ~
CF ...,.OJ (mg-yr/kg-day) = ~..,,,, x AF x ED ..I... + ~..7';!1 x AF X ED",7';!1
BW....... BW...MI
where:
CF -,...
SA...,...
SA_7~1
AF
ED.......
ED...7~.
aga-adjusted contact factor (mg-yr-event/kg~ay)
skin surface area available for contact (cm'/event)
skin surfaclI area &Vailable for contact (cm'/event)
80il to skin adherence factor (mg/cmJ)
exposure duration during agll '-6 (yr)
exposurll durlltion during agll 7-31 (yr)
COMBINED DAILY ABSORBED DOSE
Non-Carcinogena
Daily Absorbed DOSlle
((IF ...,...xc.x1 O""lcg/mgxEF.IIA THe)
+ IICF ...,...xC.x1 O""lcg/mg x EF. x A BSIIA THe)
Carc:inogena
Daily Absorbed Dose =
((IF ...,...xc.x1 O""lcg/mgxEF.IIA T cI
+ ClCF ~.x1 O""lcg/mg )( EF. x ABSIIA T c)
'.'?':"'."'.,'.
..,I\'::...,.....
...,,:
Default Value8
109 mg-yr/kg-day
16 kg
70 kg
6 yellrs
24 Yllars
200 mg/dllY
100 mg/day
109 mg-yr/kg-day
--
3400 mg-yr-event/kg-day
2430 cmJ/event
2300 cmJ/event
2 mg/em!
6 yr
24 yr
-------
Figure 5
where:
C,
EF.
AT.c
ATc
ASS'
47
(continued)
."t":~"":::;:-r~?'~.~"~~'.:\....'.'..~.:)~:7.3 . . .'.... '.'T.:.. . .
,q ....~./~:.~~~==~:~.+:..
..., ...q..;...., ... q .HCfSCSita Soia,.. '.,. ... ... q ,
.. ..::'FuCiire.SiteResiden1ll.andCUrrent S"rte Wcner.
Chemical concentration in soil
Residential exposure frequency
Averaging time (non-cercinogenl
Averaging time (carcinogen\
Absorption factor (unitless)
CURRENT SITE WORKERS
.','.:'" .
Default Values
chemical-specific
350 days/yeer
10.950 days
25.550 days
0.01
COMBINED SOIL INGESTION AND DERMAL CONTACT PATHWAYS DAILY ABSORBED DOSE
Non-Carcinogens
Combined Chronic Absorbed 00S8 =
((IR....--.. x C, x 10" kg/mg x EF- x EO_If(SW- x AT.c.......)) +
IIC, x 10" kglmg x ASS x AF x SA- x EF. x EO.\/ISW. x AT.c......))
Carcinogens
Combined Chronic Absorbed Dose =
((IR....--.. x C, x 10" kg/mg x EF. x EO_)/(SW- x ATc.......)} +
IIC. x 10" kg/mg x ASS x AF x SA.. x EF. x ED_\/(SW. x ATc._.1I
where:
IR_-
C.
EF-
ED-
BW-
AT .c.--
AT c---
ASS
AF
SA-
Worker soil inge8tion rate (mg/day)
Soil contaminant concentration (mglkg)
Worker exposure frequency (days/year)
Worker exp08ure duration (years)
Worker body weight (kg)
Worker lIVeraging time-non-carcinogen (days)
Worker lIVeraging time-carcinogen Idays)
Absorption factor (uniden)
Soil to skin adherence factor (mg/cm2)
Skin surface IIrllll IIVllilllble for contact (cmZ/event\
- .
Defeult Values
100 mg/dev
Chemical-specific
250 davs/year
30 vears
70 kg
10.950 days
25.550 days
0.01. .
2 mg/cm%
2300 cm%/event
-
-------
48
Figure 6
0. -.
" '.'
""<":.:y>'"
. ."-'"-"."..,.,"
'. ,.,. i.:"': "....::':':'.".
. .'..':.",.,-.(" ''''';'''''''''..' .
,,"E~U8UO~S'F.~t,~~~~ntb~:-<:hronic;~~sme
: . '. '..For:The'Grcnmdwate"PathWay"
. .
FUTURE SITE RESIDENTS
Non-Carcinogenic
Chronic Absorbed Dose from Groundwater =
Cw x IRw.,.. x EF x ED/(BW x ATNd
Carcinogenic
Chronic Absorbed Dose from Groundwater =
Cw x IRw.,. x EF x ED/(BW x AT cI
Where:
Default Values
C.
IR......
EF
ED
BW
ATNc
ATe
Groundwater contaminant concentration (mglliterl
Groundwater ingestion rate (1/day)
Groundwater exposure frequency (days/year)
Residential exposure duration (years)
Body weight (kg)
Averaging time for non-carcinogens (days)
Averaging time for carcinogens (daysl
Chemical-specific
2 liter/day
350 days/year
30 yeers
70 kg. :~.. -
30 yeers x 365 d/yr..1 0,950 days
70 vears x 365 d/yr..25,550 davs
a - Oefault exposure assumptions value. referenced from USEPA, RAGS, 12/89 and OSWER Directive 19285.6-03.
Note:
Assume absorbed dose is equivalent to intakelingested dose.
Cancar Risk," Carcinogenic Chronic Absorbed Dose x Siopa Factor
Huard Index.. Non-Carcinogenic Chronic Absorbed Dose/RfD
-------
49
eliminated PARs and phenolic compounds from further considerationon
the basis of low detection frequency and low concentration.
6.2
EXPOSURE ASSESSMENT
Contaminated media at the Site include surface and subsurface soil;
shallow groundwater; and surface water and sediments in on-Site and
adjacent wetlands. Pathways involving air as a medium were not
considered due to the extensive grass and vegetative cover at the
Site, and the lack of positive results from air monitoring for
Site-specific contaminants.
Populations that could potentially be exposed to Site contaminants
under current exposure conditions are on-Site workers and
occasional trespassers. Potential future land use exposure
scenarios include child and adult residents living on the Site, and
children and adults living near the Site who might visit or play on
the Site.
Based on these potential receptors, three general exposure pathways
were selected for numerical risk quantification:
1.
Current exposure of adult non-residents (Site workers and
trespassers) to contaminants in surface soils through
incidental ingestion and dermal contact.
Future exposure of on-site adult and child residents to
contaminants in shallow soils through incidental ingestion and
dermal contact.
2.
3.
Future exposure of onsite adult and child
contaminants in groundwater through ingestion.
residents
to
In order to quantify the exposure associated with each pathway,
various standard procedures were used to determine key variables in
the exposure calculations. These variables include the contaminant
level in the medium, usually referred to as the exposure point
concentration; and the amount of the chemical taken into the body,
or chronic daily intake, which must be calculated using a number of
assumptions. Since EPA policy is that exposure estimates must
approximate a Reasonable Maximum Exposure (RME) scenario, each of
the variables was selected with the goal of producing the maximum
exposure that could reasonably be expected to occur. Tables 13 and
14 present the exposure point concentrations calculated for the
contaminants of concern in soils and ground water. It should. be
noted that the mean concentrations for each contaminant detected in
the .hot spots. were used as the exposure point concentrations in
the RME evaluation.
Calculation of average daily intake requires input of numerous
exposure parameters which are usually applicable to a particular
-------
Table 11
50
,:';r.:z~~,j..~.!::.j'(t;~!~~i1~~f~~:~~.>&p08:i;~:~~~:~f~.:::<~1':~.forfUU. SM ReeCemw'
...., .... ...... . ~~
..... ...'''' .."
.- .. d"
"" """'..,"'.' . "... ',"., ,', .. ':'.:, ''''::''''}HCFsC' Sb ""',"',, .
...
.::
"p.r.~~.'J
Aldrin
alpha-BHC
beta-BHC
delta-BHC
gamma-BHC
DDT
DDD
DDE
Dieldrin
Endosulfan II
Endrin
Endrin Ketone
,Toxaphene
Endosulfan
Sulfate
Disulfoton
Benzene
Lead
Chromium
Notes:
"
...' "'.-
.. ". .
, . ..
.. ,
::'F-n8nt~.6%.:::
,::,UCLM"n ,,::'::
'.' (ppiitJ
0.00027
0.0034
0.0037
0.0011
0.00069
0.00017
0.00024
0.00021
0.0011
0.00013
0.000081
0.0030
0.0083
0.000091
0.0091
0.0069
0.0115
0.0697
.. ,
.":Clft8nt..
'.'Upper
. """'.Bound,' ,
e:.ncerRi8k
5.4E-5
2.54E-4
7.90E-S
NA
1 .05E-5
7.00E-7
6.75E-7
8.31E-7
2.08E.4
NA
NA
NA
1.07E-4
NA
NA
1.99E-6
NA
-
: ,'",',
, CW1'ent
Hazard
Indice8 ,
0.24
NA
NA
NA
0.063
0.0096
NA
NA
0.61
0.073
0.0073
0.27
NA
0.050
6.25
NA
0.23
8.19E-4
..
...
..
.:. COnc:entr81ion' (ppbl Requi'ed 10 Obtain
1~Ri8Ic
1 cr": Riak ""
-
1.35
-
-
-
-
-
-
0.53
-
-
-
7.75
-
-
-
-
-
.-
10"fr.k.
0.049
0.135
0.47
-
0.66
-
-
-
0.053
-
-
-
0.775
-
-
-
-
-
The ensuing reduction in contaminant levels would also reduce the t Hazard Indices to below unity 11 I.
Groundwater cleanup ooals may be calculated bV solvinO the fonowing:
Groundwater Cleanup Goal Ippbl .. Risk Level Goe' x Current Groundwater Concentration
Current Risk Level
0.0049
0.0135
0.047
0.066
0.0053
-
0.0073
_.
-
0.078
1.5
IHI=11
2.94
':.::
-
-
-
-
-
-
-
-------
51
Table 12
. .
-.
:~f:~~;ti~~::diH~+r\'=::~: .',"
,I,~;:~;!~~:::::':;:;:::::' ...
~zti;!~~~~~:l~cFSC.~
',".,
"'.C:,
. ,'," "..' .....::>.:"::;::~~~. &~R~~:
, ,
. .
''':;:':.
...'.'''''.''''':' ..
.'
, .--
.. ......"
"."."."'.'..".'.',".".", ,".- "."".,"'
.... ... ..'" ....
:':.:V~~:;:.:::::
','.', 'CmvJkg)""
.... ,:,:,::::,::;:::::::::::":'~';:
".."".',",'...".'.",
~:;:':;;~~~:~;I*' '.:
r: Ikk~nci.::R8kLeVeL.:
":..."',:'::
":",,,,".':::>
,
,
.:jt:.:
.. ...."
..
. :. ......"..
..- ...... .....
.t:~nilimiMnr ."
:1~'- ,::;:
:1~'"
,0--
Aldrin 1.59 5.3E-5 -
alpha-SHC 0.53 S.5E-S -
beta-SHC 0.75 2.S5E-6 -
delta-SHC 0.3S NA NA
gamma-SHC 0.034 S.SSE-S -
DDT 19.2 1.2SE-5 -
DDD 6.45 3.04E.S -
DOE 0.91 S.07E-7 -
Dieldrin 2.69 S.45E-5 -
Disulfoton 0.097 NA NA
Endosulfan 1.82 NA NA
Endosulfan 1.92 NA NA
Sulfate
Endrin 0.55 NA NA
Endrin Ketone 0.22 NA NA
Methoxychlor 3.3 NA NA
TSPT 0.0 NA NA
I
Toxaphene 43.3 9.35E-5 -
0.3
0.03
-
0.08
-
NA
-
15
-
-
0.32
NA
NA
- ~:'" -NA
NA
NA
NA
NA
4.S3
0.28
NA
-
1.5
2.1
-
0.032
NA
NA
-NA
NA
NA
NA
NA
0.463
Note8:
No compound presented a hazard index in excess of 1; a 6near relationship exists between soil concentration and
aaaociated risk level., therefore the cleanup objective. for each risk level may be computed by determining the
following:
X (Soil Cleanup Goall = Risk Level Goal x Current Soil Concentration/Current Risk Level
NA
No Slope Factor for the compound.
Current contaminant level. in .oil do not present 8 risk in exce.. of the r88pective risk level..
-------
52
exposure pathway. The exposure parameters used for soils
aresummarized in Figure 5. The same parameters for ground-water
exposure are shown on Figure 6.
The result of the exposure assessment is a set of tables showing a
calculated average daily intake value for each chemical or
compound, as well as a summary value for each exposure pathway.
Tables 13 and 14 contain these data and summaries.
6.3
TOXICITY ASSESSMENT
In this portion of the Baseline Risk Assessment, the toxic effects
of contaminants were investigated and evaluated. The critical
variables needed to calculate estImates of risk were obtained from
the EPA toxicological databases. Critical toxicity values for
Helena Chemical Site contaminants are presented in Table 15.
Slope factors (SFs) have been developed by EPA's Carcinogenic
Assessment Group for estimating lifetime cancer risks associated
with exposure to potentiall carcinogenic contaminants of concern.
SFs, which are expressed in terms of (mg/kg-day)-t, are multiplied
by the estimated intake of a potential carcinogen in order to
provide an upper-bound extimate of the excess lifetime cancer risk
associated with exposure at that intake level. The term .upper
bound. reflects the conservative estimate of the risks calculated
from the SF. Use of this approach makes under-estimation of the
actual cancer risk highly unlikely. Slope factors are derived from
the results of human epidemiological studies or chronic animal
bioassays; if anima.l bioassays are used, animal-to-human
extrapolation and uncertainty factors are applied to account for
the use of animal data to predict effects on humans. The SFs for
the carcinogenic contaminants of concern are contained in Table 15.
Reference doses (RfDs) have been developed by EPA for use in
indicating the potential for adverse health effects from exposure
to contaminants exhibiting noncarcinogenic effects. RfDs, which
are expressed in units of mg/kg-day, are estimates of lifetime
daily exposure levels for humans, including sensitive individuals
or subpopulations. Estimates intakes of contaminants of concern
ingested from environmental media can be compared to the RfD. RfDs
are derived from human epidemiological studies or animal studies to
which uncertainty factors have been applied, to account for the use
of animal data to predict effects on humans. The RfDs for the
noncarcinogenic contaminants of concern are also contained in Table
15.
Carcinogenic contaminants are classified according to EPA' s weight-
of-evidence system. This classification scheme is summarized
below:
Group A:
Known human carc~nogen.
-------
53
Table 13
-
.'".' ....L..."""");:/~~~~~~~EJ~:~~~~4:~.'
,;:~::::,.; "., ::: " .. .. "".f.'," :',.
" '. :'.':SIope
... ":~%UCl~' '.': ,'.FaCtor... Refe.oenceDos8 Upper Bound
.':'-Nrametef.. (Pllbl '(SF). (RfDr Cancer Risk' Hazard Index.'
Aldrin 0.266 17 0.00003 S.32E.S 0.24
alpha-BHC 3.44 6.3 NA 2.S4E.4 NA
beta-BHC 3.74 1.8 NA 7.90E.S NA
delta-SHC 1 .06 NA NA NA NA
gamma-SHC 0.69 1.3 .0003 1 .OSE.S 0.063
DDT 0.175 0.34 0.0005 7.00E.7 0.0096
DDD 0.24 0.24 NA 6.7SE.7 NA
DDE 0.21 0.34 NA 8.31E.7 NA
Dieldrin 1 .1 1 16 0.00005 2.08E.4 0.61
Endosulfan II 0.13 NA 0.00005 NA 0.013
Endrin 0.081 NA 0.0003 NA 0.0013
Endrin Ketone 2.98 NA 0.00034 NA 0.27
" ... _.
Toxaphene 8.29 1.1 NA '.~ '-~~ 1.07E-4 NA
Endosulfan Sulfate 0.091 NA 0.000054 NA 0.050
Disulfoton 9.12 NA 0.00004 NA 6.25
TBPT 10.7 NA NA NA NA
Banzene 6.85 0.029 NA I:::':.: 1.99E-6 NA
Lead 11.5 NA 0.0014. I..:,:".:,"'>' NA 0.23
Chrorriium 69.75 NA 1.0 ::/;:< NA 8.19E-4
.. ..
Sum of Cancer Risks and Huard Indices4 ::t Risk .....7: 1 E-4.'.. ..:::1: :ffl-,,-7.S0):.
a - a..umes consumption of 2 liters/day of contaminated round water (et 95% UCL for each paramater) over
.;
c
g
a 70 vear period for carcinogens end a 30 year period for non-carcinogens.
Rgure 7.2 provide. the equations used to compute chronic daily intake for e.tablishing risk levels and hazard
indice..
95% Upper Confidence Umits means calculated using detected values for hits and one-half the sample
quantitation limit for non-hits. Data used was derived from the 3rd and 4th Quarter 1991 Groundwater
Sampling Evanta.
RID for endrin applied to endrin ketone; RfD for endosulfan applied to end08ulfan .ulfate.
The unit risk for leed is calculated from a treatment technology based MCL of 0.015 mg/1. A USEPA
approved RfD for lead has not been established. .
Huerd Indices have been summad e8 a conservative estimete of no~rcinogenic risk; generelly summetion
of Huard Indica8 is eppropriate only for contaminants having the same target organ effect (for non-
carcinogens!.
b
d
e
f
-------
54
Table 14
...
::/".;7.:(:'/Y .. ":~7-1~::7:'0' '. . '.' '.:u, .
.' Summ..yof'~bfor ~entAd~.Worlc8n'anclFUUir8 Site:Reeidenta
,'fromOr8l'.n.tDerm.aI Ejpoean-1i:»'cor-nin8m. in &OllSadim8nt8 .
.~ ::::::<: . .' uHCFSC.n. . '.':,':..'.' "'.:':>
..
Concen1ration of
Contamift8nt
Imglkg).
Contaminant
Fuuwe Resident Upper
Bound Riak Level"
lor Hazard Indexl
Adult Worker Upper Bound
Risk Level"
lor HaZ8rd Index)
1.59
Aldrin
5.3E-5
IHI =0.0243)
6.5E.6
1.56E-5
IHI =0.076)
0.53
alpha-SHC
2.0E-S
0.75
beta.SHC
2.65E.6
8.3E.7
0.38
delta-SHC
NA
NA
19.2
6.45
0.91
2.69
.
1.82
1.92
0.55
0.22
3.3
43.3
0.097
0.0
DDT
8.68E-8
(HI =0.00052)
1.28E-5
(HI=0.1761
2.7E-8
(HI = 1.6E-4)
0.034
gamma-SHC
DDD
3.04E-6
4.0E-6
(HI =0.0551
9.5E-7
DDE
6.07E.7
8.45E.5
(HI =0.2461
1.9E- 7
Endosulfan
(HI =0.1671-;'
(HI =0.1761
2.6E-5
(HI =0.0771
(HI =0:0"52)
Dieldrin
Endrin
(HI =0.0084)
(HI =0.0551
(HI =2.6E-31
Endosultan Sulfate
Methoxychlor
IHI =0.00341
IHI..0.0031
IHI = 1.1 E-31
IHI = 9.4E.41
Endrin Ketone
Disulfoton
9.35E.5
IHI..0.011)
2.92E-5
Toxaphene
IHI =0.0035)
TBPT"
NA
NA
.... . .. ... ~...~... "...
n', .. .'" n'"" ...... .
<'~:<:::::;:~mj:of'Upp~~:::B~nd' Cancer Risk.
.
2;67£4
8.0E.5
:..'
. . ... ,_. ..... ..
..... .. ,".
.. ... n..
: Sum ofHwrd 'Indicee.
. .... .. .. . ..
Sumof. HI=;82.
'Sum of HI =0.32
Notes:
a
Mean concentration in soil 195% C.t. was not calculated as the data are not normally distributed). The mean
contaminant concentrations in the "hot spots" on8ite were assumed to be preeent over the entire site area. Uniform
exposure 10 all arees onsite was 8s8umed to provide 8 conservative estimete of exposure. Thie approach is consistent
.-with USEPA. Region IV guidance for e8tablishing RME level..
HI (Hazard Index) of > 1 Is e cauee for conC8rn. Upper bound risk levels of 10" to 1 0" are considered on e can.by.
ca.. basi8 as to their 8cceptability by the USEPA.
c TBPT was not identified in surface soils onsite.
NA Not applicable
b
-------
55
Table 15
c~":,a;t;lg~~~a~l:::: ,.
.:/..::,.:.
COntaniinaitt
..
..
.. . ..
.. ..... .
.S'~pe f8criDr.csFi
.cniglkgJdayr~
.-
..
..
::.RfD
.. (mgIkgldayJ
ARAR
(Met. u mglt)
Chlordane
1.3
0.00006
0.002
Endrin
NA
0.0003
0.002'
Heptachlor
4.5
0.0005
0.0004
HeptachJor Epoxide
9.1
0.000013
0.0002
Disulfoton
NA
0.00004
NA
Senzene
0.029
NA
0.005
Aldrin
17
0.00003
NA
a-SHC
6.3
NA
NA
B-SHC
1.8
NA
NA
gemme-SHC lLindene)
1.3
0.0003
0.0002
delta-SHC
NA
NA
NA
Dieldrin
16
0.00005
NA
Endosulfan
NA
DDD
0.24
0.000.9.5
NA
...
NA _.
NA
DDE
0.34
NA
NA
DDT
0.34
0.0005
NA
Toxaphene
1.1
NA
0.003
TBPr
NA
NA
NA
Methoxychlor
NA
0.005
0.04
Chlorobenzilate
NA
0.02
-
Chromium4
NA
1.0
0.1
lead
NA
0.0014"
0.015"
A proposed MCl of 0.002 mgll
No verified rilk baled criterie exilt for TBPT.
The unit ri.k for IlIIId il calculeted from e treetment technology billed MCl of 0.015 mgJl. A USEPA epproved RfD for
lead ha. not been esteblilhed.
d be.ad on ellumption that ell chromium is present in the (III) valence state.
e unit ri,k computed from MCl
NA Not evailable or not determined
Slope Fector Iynonymoul to Cencer Potency Fector (CPFJ
a
b
c
-------
56
Group B1: Probable human carcinogen, based on limited human
epidemiological evidence.
Group B2: Probable human carcinogen, based on
human epidemiological evidence but
evidence of carcinogenicity in animals.
inadequate
sufficient
Group C:
possible human carcinogen,
carcinogenicity in animals.
limited
evidence
of
Group D:
Not classifiable due to insufficient data.
Group E:
Not a human carcinogen, based on adequate animal
studies and/or human epidemiological evidence.
6.4
RISK CHARACTERIZATION
It should be noted that there is some degree of uncertainty
associated with the calculated numerical estimates of human health
risks generated in the Baseline Risk Assessment. This is due to
the considerable number of assumptions required to provide
variables in the equations, and the specific selections of each
variable from a range of possibilities. The potential risk
associated with soils and groundwater exposure was quantified
through the standard risk assessment scenarios (Tables 13 and 14) .
6.4.1
Ground Water
Ground-water risk based upon residential drinking water. exposure
was evaluated as a potential future risk. Samples from several.
monitoring wells had at least one contaminant that exceeded the
current MCL.
Table 13 presents the individual risks associated with each
parameter found in ground water along with total carcinogenic and
non-carcinogenic values. The total groundwater risk for future
residents consuming water from the surficial aquifer was calculated
at 7.1 x 10-'. The summation of the Hazard Indices for the future
groundwater exposure scenario was calculated at 7.8. Toxaphene,
dieldrin and alpha-BHC account for 80 percent of the carcinogenic
risk. Disulfoton accounts for 80 percent of the non-carcinogenic
risk. These values indicate that significant carcinogenic and
noncarcinogenic risk may be posed by consumption of contaminated
groundwater from a potable water well located onsite. The
assumptions upon which these risk levels were based are
conservative.
The groundwater risk levels were computed using the 95 percent
Upper Confidence Limit of the mean from each well for each'
parameter. The 95 percent Upper Confidence Limit was computed
-------
57
using detected values for hits and one-half the sample quanti tat ion
limit for non-detects. The mean value for each groundwater
monitoring well (for the 3rd and 4th Quarter 1991 sampling events)
was used. This more rigorous statistical approach for computing
"the Reasonable Maximum Exposure (RME) was used due to the greate~
uncertainty associated with the distribution of contaminants in the
groundwater medium.
Under current circumstances, contaminants attributable to the site
pose no imminent carcinogenic or non-carcinogenic risk to site
workers or area residents through the groundwater exposure pathway.
The adjacent municipal potable water well is screened in a deeper
saturated zone separated by a possible aquitard from the
contaminated aquifer. The municipal well has been tested, and no
site constituents have been detected in the potable source.
Residences within the groundwater contaminant plume" area are
connected to the municipal water system rendering private wells
unnecessary.
In light of these factors, future resident exposure through the
groundwater pathway may be minimized through control of the iimited
shallow aquifer contamination. Control would serve to reduce
contaminant levels in the shallow aquifer (with concurrent
reductions in the future resident groundwater onsite exposure risk
potential), and would prevent migration of contaminants to the
unaffected deep aquifer supplying the nearby municipal well.
Surface water is not considered a significant pathway for direct
human exposure.
6.4.2
Soils
Direct soil exposure poses a pathway of significant reasonable
potential risk (current and future). Upper bound cancer risk and
toxicity hazard index val~es were calculated for the contaminants
of concern. A summary of these calculated values is shown in Table
14.
The soil samples indicated that soils had a wide range of
contaminant levels with rather defined areas of greater contaminant
concentration (north and northeast portions of the Site). The vast
majority of Site contamination exists within an area from the north
warehouse building onsite to 300 feet north and northwest of this
warehouse building. Careful perusal of the data gathered during
the RI reveal approximately 30% of the Site's total soil area is
contaminated with total pesticide levels greater than 100 ppb.
Volatiles in soils tend to be in these same areas (warehouse and
old landfill) but only constituted 20-25% of the total area. Soil
contaminant mean concentrations were computed using the 'hot spot~
"method where only those samples with detectable contaminant
concentrations were included in the calculations. The total area
-------
58
of the' hot spots' encompasses approximately 30 percent of the
entire site area. In order to provide a conservative exposure
estimate, the computed mean concentration of each contaminant (from
'hot spots') was assumed to exist over 100 percent of the site.
This approach is consistent with EPA guidance for establishing
reasonable maximum exposure (RME) levels.
Throughout most of the year, site sediments are not submerged, and
as a result, present the same exposure pathways as site soils.
Sediment contaminant concentrations were within the range observed
in site soils. Therefore, no differentiation was made between soil
and sediment for risk computation purposes for the ingestion and
dermal contact pathways. .
In order to provide a conservative estimate of the potential risk
posed by the direct ingestion and dermal contact soil exposure
pathways, the following exposure scenario assumptions were applied ~
The potential for direct soil ingestion or dermal contact with
soils is greatest for those soils closest to ground surface. As a
result, the arithmetic mean was computed for each constituent of
concern using soil concentrations from samples collected within one
foot of ground surface. The distribution of pesticide contaminants
indicated that higher concentrations for an area are generally
present at the surface. Only positive results were used for the
calculation of mean contaminant concentrations in soil. As a
result, the mean values calculated (and used for calculation of
chronic daily intakes) were biased toward the higher range of all
values observed for soils. This approach is consistent with the
'hotspot' approach discussed in USEPA, RAGS, 12/89.
In addition for purposes of calculating carcinogenic risk (or
hazard index), it was assumed that the computed average contaminant
concentrations were present over 100 percent of the site. It was
also assumed that current site workers and future site residents
would have uniform exposure to all areas onsite. This assumption
is conservative in that current site operations are restricted to
approximately 25 percent of the site area. Highly contaminated.
soils are concentrated north and northeast of the north warehouse;
The current operations area is restricted to the southern portion
of the north warehouse. Current site workers do not enter other
highly contaminated areas over the course of everyday operations.
The relevant current and potential future soil exposure scenarios
for this site are considered to be adult workers and future site
residents exposed through the combined pathway of ingestion and
dermal adsorption of contaminated soil. Trespassers would be
expected to spend a minimal amount of time on-site compared to
adult workers and therefore should be more than adequately
protected based on the occupational risk calculations.
Table 14 summarizes computed risk values (and hazard indices) for
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the soil direct ingestion and dermal contact exposure pathway. The
combined carcinogenic risk from surface soil contaminants is 8.0 x
10-5 for current adult workers and 2.57 X 10-4 for future site
residents. Aldrin, toxaphene, and dieldrin account for the
majority (approximately 85 percent) of the total upper bound cancer
risk for onsite surface soils for both current adult workers and
future site residents. The sum of hazard indices is less than
unity (1) for current adult workers and 1.0 for future site
residents, using only soil exposure pathways. It is worth noting,
however, that the sum of hazard indices is generally relevant only
in instances where the target organ for each contaminant is the
same. As a.result, the computed sum of hazard indices yields a
more conservative assessment of non-carcinogenic risk.
The areas directly north and northwest of the northernmost
warehouse represent the area of concern for most surface soil
contaminants. It should be noted that each individual surface soil
contaminant was assumed to be present over 100 percent of site
surface soils (at the mean concentration). In reali.ty, each
contaminant is present in a much smaller area. The contamination
distribution assumptions and the occupational exposure duration
assumptions used in calculating risk are conservative. It should
also be noted that occupational exposures are intermittent and not
continuous. Again, the conservative assumption of continuous
exposure was used.
6.4.3
Surface Water
The surface water identified on-site is intermittent in nature, and
only exists after rainfall associated with storm events. Standing
water is generally isolated to the densely vegetated area along the
north property line. This area is not subject to recreational use,
and site workers do not have occasion to enter this area during
normal site operations. As a result, surface water is not
considered a viable exposure pathway.
6.5
ENVIRONMENTAL (ECOLOGICAL) RISKS
Surface water and sediment samples were gathered during the RI from
on-Site areas and in drainage pathways leading from the Site into
local surface water streams. These samples were shown to be
contaminated with Site-specific pesticides at levels which present
an unacceptable level of risk to environmental receptors.
Surface water samples were contaminated with pesticides at
concentrations which exceed ARARs, namely Federal Ambient Water
Quality Criteria (AWQC) and State of South. Carolina ambient
standards for surface waters. The AWQC and state standards have
been established based upon protection of aquatic life from adverse
ef fects of exposure to toxics, and it is presumable ...that
concentrations which exceed these criteria and standards will have
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an unacceptable adverse impact on environmental receptors.
Sediment samples were also found to be contaminated with Site-
specific pesticides. There are no promulgated standards or
criteria for sediment quality at either the State or Federal level,
so no ARARs exist for" sediment quality. Considerable research has
been conducted, however, on the environmental effects of exposure
to contaminated sediments. This research has been compiled by the
Na"tional Oceanographic and Atmospheric Administration (NOAA), in
the document entitled The Potential for Bioloqical Effects of
Sediment-Sorbed Contaminants Tested in the National Status and
Trends Proqram, NOAA Techni cal Memorandum NOS OMA 52, Augus t, 1991.
The levels of sediment contamination found at this Site exceed the
levels cited in this document as being likely to contribute to
adverse impacts to biological receptors.
7.0
DESCRIPTION OF REMEDIAL ALTERNATrvES
The Feasibility Study (FS) considered a wide variety of general
response actions and technologies for remediating soil and
groundwater. Based on the FS, Baseline Risk Assessment, and
Applicable or Relevant and Appropriate Requirements (ARARs), the
remedial action objectives (RAOs) listed below were established for
the Site. Alternatives were developed with the goal of attaining
these objectives:
Groundwater - EPA believes that active remediation of groundwater
(such as a groundwater pump and treat system) in the Barnwell
formation underlying the Site is a practicable and appropriate
response. The Barnwell Formation is classified under the EPA
Guidelines for Ground-Water Classification as a Class IIB ground
water, ie., a potential source of potable water supply. These
ground waters also are classified as Class GB waters of the State.
The contamination at the Site has resulted in impairment of the
ground-water resource as a potential drinking water source due to
unacceptable risks to human health. In addition, the likelihood of
a hydraulic connection between the Barnwell Formation and the
underlying McBean/Santee Formation exists; the nearby municipal
supply well draws water from the McBean/Santee Formation. In order
to prevent migration from the existing contaminant plume into the
underlying drinking water supply aquifer, ground-water extraction
is warranted.
The remedial action objective for contaminated ground water is to
restore the affected aquifer to a condition that renders it
suitable for use as a potable water supply. Criteria based upon
protection of human health via drinking water exposure for site-
specific contaminants of concern are listed in Table 6. These
criteria constitute the remedial goals for ground water at the
Helena Site.
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Given the likelihood of a hydraulic connection between the Barnwell
and the McBean/Santee formations, and the inconclusive nature of
tne pump test conducted as part of the RI, EPA anticipates that
effective implementation of the ground-water remediation at this
Site will include another pump test. The purpose of such a pump
test will be to determine the degree of interconnection between the
formations mentioned above. The exact means by which this pump
test will be conducted will be determined during remedial design
activities.
Surface and Subsurface Soils - Soils on the Site, both at the
ground surface and at depths grater than one foot, are contaminated
at levels which exceed criteria protective of human health under an
exposure scenario which assumes unrestricted land use, including
residential development, and which exceed concentrations that are
likely to continue to leach contaminants to ground water. The
overall remedial action objective for the surface and subsurface
soils is to remove and remediate contaminated soils to such a
degree that both ground-water quality (in conjunction with ground-
water extraction and treatment) and human health are protected.
The RI identified soil remediation goals for both of these
purposes. Table 7 presents a comparison of these remedial goals as
developed in the RI. EPA review of the remedial goals developed in
the RI for the protection of ground water revealed, however, that
the technical basis for these goals was inadequate. EPA therefore
conducted an independent analysis of soil contamination levels and
has determined that a soil remediation goal of 50 ppm total
pesticides is protective of human health and the environment, and
will result in the removal of 90% of the total pesticide mass that
exists at the site.
The evaluation performed by EPA was based upon contaminant
distribution data provided in the RI. EPA used this contaminant
distribution data to calculate the contaminant mass associated with
the soils at the Site as it is related to contaminant
concentrations. Contaminants migrating from a relatively
concentrated source area via soils or ground water tend to be
logarithmically distributed. By determining the concentration at
which the bulk of contaminant mass will be removed and optimizing
this concentration with relation to the volume of soil requiring
treatment (i .e., by avoiding a situation whereby the law of
diminishing returns is created), the appropriate soil remediation
goal can be estimated.
The proposed remedial action would then consist of treating the
soils by a combination of bioremediation and hydrolytic/photolytic
dechlorination (HPD) , and replacement of the treated soils in the
on-site excavations, followed by covering the backfilled material
with one foot of clean soils. The performance standards for
treatment of the soils would satisfy the Land Disposal Restrictions.
(LDRs) found in 40 CFR Part 268, promulgated under the authority of
the Resource Conservation and Recovery Act (RCRA). This proposal
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is based partly upon the concept that ground-water quality can be
protected by treatment of soils in these source areas in
combination with extraction and treatment of contaminated -ground
water. The removal and treatment of soils in the source areas is
also protective of human health via direct contact and incidental
ingestion.
Wetlands and Contaminated Sediments The placement of fill
material in jurisdictional wetlands, and the contamination of the
sediments in the wetlands that resulted from this placement, have
resulted in an unacceptable level of risk to environmental
receptors. The remedial action objective for the fill and the
contaminated sediments is to mitigate for the impacts that have
resulted in these unacceptable levels of risk to environmental
receptors. Mitigation will comply with the requirements of Section
404 of the Clean Water Act, and specific mitigative measures will
be determined in accordance with the criteria and guidelines
established under Section 404 (b) (1) of that Act. These regulations
are relevant and appropriate to the circumstances of the release of
contaminants from the landfill placed in jurisdictional wetlands.
The following section provides a summary of the six (6)
alternatives developed in the FS Report to address the
contamination of soils, sediments and ground water at the Helena
Chemical NPL Site. The primary objective of the FS was to
determine and evaluate alternatives for the appropriate extent of
remedial action to prevent or mitigate the migration or the release
or threatened release of hazardous substances from the Site. With
the exception of the No-Action alternative, all alternatives
include the same provision for extraction, treatment and proper
di.sposal of contaminated ground water. Likewise, all alternatives
with the exception of No Action have the same provi.sion for
mitigation of the adverse effects associated with pesticide
contamination in the wetlands adjacent to the Site. While wetlands
mitigation is not discussed in the FS as a component of any of the
alternatives, EPA has determined that unacceptable levels of risk
to environmental receptors have resulted from the release of site-
specific contaminants into jurisdictional wetlands. Mitigation for
these releases has been determined to be relevant and appropriate
to the circumstances of the release under the criteria for such
determinations contained in the NCP. Alternatives 2 through 6
(Alternative 1 being the No-Action alternative) differ only in the
technologies to be applied for the remediation of contaminated
soils.
The following descriptions of remedial alternatives are summaries
of more complete descriptions found in the FS report. The FS
report contains a more detailed evaluation of each alternative and
is available for review in the Administrative Record for the Site.
All costs are based upon capital costs plus the present worth of
annual operation and maintenance costs.
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7.1
ALTERNATIVE 1 - NO ACTION
By statute, EPA is required to evaluate a .No Action. alternative
to serve as a basis against which other alternatives can be
compared. Under the No Action Alternative, no remedial response
would be performed on any of the media of concern (surface soil'.
ground water or sediments) at the Site. This alternative does not
reduce the risk calculated by the Baseline Risk Assessment. The No
Action Alternative results in an excess cancer risk of 8.0 X 10-5
and a Hazard Index for non-carcinogenic effects of 0.3 for current
land use exposure scenarios, and an excess cancer risk of 2.6 X 10-4
and a Hazard Index for non-carcinogenic effects of 8.6 for
potential future land use scenarios.
The estimated present worth cost for the no-action alternative is
$480,000. This cost is for monitoring of ground water and soils
for thirty years.
7 ."2 ALTERNATIVE 2 - DEMOLISH FORMULATION BUILDINGS; CONSOLIDATE
CONTAMINATED SOILS AND DEBRIS IN ONSITE LANDFILL; GROUND-WATER
EXTRACTION, TREATMENT AND DISPOSAL; AND WETLANDS MITIGATION
All alternatives, excluding No Action, include ground-water
containment by means of extraction, treatment and appropriate
disposal. The installation of ground-water extraction wells will
prevent the migration of contaminants beyond the present extent of
the contaminant plume, and will over time remove contaminants from
the ground water lying beneath the Site. At present, the extent of
contaminated ground water is confined to the shallow aquifer (the
Barnwell Formation) and does not appear to extend laterally to off-
site areas.
Extracted ground water will be treated to criteria appropriate for
the final means of disposal. At present, it is planned that the
extracted ground water will be treated and discharged to the local
sanitary sewer system, also known as a POTW. Pretreatment
requirements will be set by the owner/operator of that sanitary
sewer system in order to insure that the discharge permit for the
system will not be violated. It is possible, based upon initial
estimates of ground-water quality, that no pretreatment will be
necessary; for the purposes of preliminary cost estimates, however,
it is assumed that some degree of pretreatment for extracted ground
water will be required. The actual technologies to be employed
will be based upon the pretreatment criteria established by the
owner/operator of the POTW.
Extraction of contaminated ground water will continue until the
ground-water remediation goals are met throughout the extent of the
plume. Should it prove to be technically impracticable to achieve
these remedial. goals, EPA will amend the ROD to reflect any changes
in remediation criteria.
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All alternatives, with the exception of No-Action, also include the
demolition of on-site buildings as necessary to remove contaminated
soil for treatment. Testing of the demolished buildings will be
conducted during remedial design in order to determine the
appropriate methods of disposal for demolition debris. It is
likely that the demolition debris will not be significantly
contaminated, so that no special handling will be required,
al,lowing disposal of the demolition debris as non-hazardous solid
waste.
All alternatives, with the exception of the No-Action Alternative,
also include. mitigation for contaminated soils and sediments in the
wetland areas adjacent to the Site and downstream can be
accomplished in a number of ways under the regulations, guidelines
and criteria established under Section 404 (b) (1) of the Clean Water
Act, which is an ARAR for the remedial action at this Site. The
exact form of mitigation that will satisfy the requirements of this
ROD will also conform with the Memorandum of Agreement (MOA)
between the Corps of Engineers and EPA which took effect on
February 7, 1990. This MOA is a criterion 8to be considered8 in
the determination of remedial actions for the Site. Removal of the
fill placed in the affected wetlands, accompanied by removal of the
contamination that has resulted from transport of toxic materials
from that fill, is one potential method. Another would be the
restoration of degraded wetlands at some off-site location.
Another possibility is the acquisition of unaffected wetlands that
are currently threatened by development or other destructive
activities and placing those wetland areas in a protected status.
A number of factors will be used to determine the most cost-
ef,fective and environmentally sound manner in which compliance with
the mitigation guidelines will be achieved.
Alternative 2 calls for the demolition of the former formulation
buildings on the Site, excavation of contaminated soils and
disposal of contaminated soil in an on-site landfill constructed
especially for this purpose. All soils exceeding 50 ppm total
pesticides would be placed in the landfill. The landfill would be
constructed to meet all applicable technical requirements regarding
design of such landfills, including top and bottom liners to
prevent infiltration of rainfall and also to prevent any further
contamination of ground water. Long-term maintenance of the
landfill would be required as part of the implementation of this
alternative.
The estimated cost for this alternative is $5~5 million.
7 .3 ALTERNATIVE 3 - DEMOLISH FORMULATION BUILDINGS, EXCAVATION AND
ON-SITE BIOLOGICAL TREATMENT OF CONTAMINATED SOILS, GROUND-WATER
EXTRACTION, TREATMENT AND DISPOSAL, AND WETLANDS MITIGATION
The ground water and wetlands portions of this alternative are
,
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identical to those described under Alternative 2. They will
consist of ground-water extraction, treatment and disposal
(preferably in the local sanitary sewer), and mitigation of
wetlands impacts. Demolition of Site buildings will also be as
described under Alternative 2.
Under this alternative, contaminated soils containing greater than
50 ppm total pesticides would be treated on-site by means of
biological degradation. Biological degradation would take place in
treatment cells constructed on-site that would be lined to prevent
any leaching of contaminants to ground waters underlying the Site.
Biological treatment cells would consist of lined pits into which
the contaminated soils would be placed. Once placed into the
cells, moisture content, temperature and nutrient levels would be
adjusted and maintained to maximize the rate of biological
activity. Both aerobic and anaerobic conditions are envisioned in
order to maximize the effect of biological degradation.
Anticipated treatment would consist of anaerobic treatment,
particularly for soils contaminated with DDT, followed by aerobic
treatment. Some of the Site soils may require aerobic treatment
alone.
Treatability studies would be conducted to determine if this
alternative can achieve the remedial goals, but preliminary data
indicate that significant reductions in concentration of many site-
specific contaminants can be achieved by biological degradation.
Once soils are treated to the remedial goals, they would be
replaced in the on-site excavations from which they were removed~
The performance standard for treatment would be based upon the LDRs
for site-specific contaminants.
The estimated cost for this alternative is $8.0 million
7.4 ALTERNATIVE 4 DEMOLITION OF FORMULATION BUILDINGS,
EXCAVATION AND HYDROLYTIC/PHOTOLYTIC DECHLORINATION OF CONTAMINATED
SOILS, GROUND-WATER EXTRACTION, TREATMENT & DISPOSAL, AND WETLANDS
MITIGATION
The ground water and wetlands portions of this alternative are
identical to those described under Alternative 2. They will
consist of ground-water extraction, treatment and .disposal
(preferably in the local sanitary sewer), and mitigation of
wetlands impacts. Demolition of Site buildings will also be as
described under Alternative 2.
Under this alternative, contaminated soils containing greater than
50 ppm total pesticides from the Site would be treated "by means of
hydrolytic/photolytic dechlorination (HPD) of the pesticide
contaminants. This process would be implemented at Helena Chemical
by mixing contaminated soils with chemical reagents and exposing
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them to heat and ultraviolet (UV) radiation. The mixing process is
necessary to distribute the reagents (usually hydrated lime,
possibly supplemented by sodium hydroxide) throughout the mass of
contaminated material. The mixed material/reagent mass is then
placed in thin layers .in cells similar to those proposed for
biological treatment in order for the soils to be exposed to heat
and UV energy from the sun. The soil mass would also be kept moist
in order to enhance biodegradation of any organic end products
resulting from the hydrolytic/photolytic dechlorination process.
Sails would be periodically .turned over. to maximize contaminant
exposure to UV radiation. The performance standard' for the
treatment process would be the LDRs for site-specific contaminants:
Treatability studies would also be required to determine if this
technology would be capable of achieving the required performance
standards.
The estimated cost for this alternative is $7.2 million.
7.5 ALTERNATIVE 5 - DEMOLISH FORMULATION BUILDINGS, EXCAVATION,
HYDROLYTIC/PHOTOLYTIC DECHLORINATION AND BIOLOGICAL TREATMENT OF
SOILS ON-SITE, GROUND-WATER EXTRACTION, TREATMENT AND DISPOSAL, AND
WETLANDS MITIGATION
This is the preferred alternative for remediation of the Helena
Site.
The ground water and wetlands portions of this alternative are
identical to those described under Alternative 2. They will
consist of ground-water extraction, treatment and disposal
(preferably in the local sanitary sewer), and mitigation of
wetlands impacts. Demolition of Site buildings will also be as
described under Alternative 2.
Under this alternative, the two technologies discussed under
Al ternati ves 3 and 4 above would be combined in order to take
advantage of the particular benefits of each. Past studies and
experience with biological treatment have indicated that biological
treatment alone is effective for many of the site-related soil
contaminants at Helena (notably DDT and its metabolites),
Biological treatment alone, however, is less effective for
toxaphene, which is another Site contaminant found in significant
concentrations, 1 ikewise contributing significantly to the risk
associated with Site exposure. HPD, on the other hand, has been
shown in pilot-scale studies to be effective in the destruction of
toxaphene. The two technologies would be combined in a treatment-
train mode, with HPD treatment followed by biological treatment.
In addition to biological treatment of site-specific contaminants
other than toxaphene, the second step of the treatment train would
also serve to further degrade the breakdown products produced by
the initial HPD step.
,
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Otherwise, the treatment processes would be as described under
Alternatives 3 and 4, above. The soil remediation goal would
remain at 50 ppm total pesticides, and the treatment performance
standard would be based upon the LDRs for site-specific
contaminants. The estimated cost for this alternative is $3.9
million.
7.6 ALTERNATIVE 6 - DEMOLISH FORMULATION BUILDINGS, EXCAVATION AND
LOW TEMPERATURE THERMAL DESORPTION OF SOILS ON-SITE, GROUND-WATER
EXTRACTION, TREATMENT AND DISPOSAL, AND WETLANDS MITIGATION
The ground water and wetlands portions of this alternative are
identical to those described under Alternative 2. They will
consist of ground-water extraction, treatment and disposal
(preferably in the local sanitary sewer), and mitigation of
wetlands impacts. Demolition of Site buildings will also be as
described under Alternative 2.
Under this alternative, contaminated soils exceeding 50 ppm total
pesticides from the Site would be treated on-site by means of low
temperature thermal desorption (LTTD). This process. involves
processing contaminated soils through a rotary dryer or kiln. The
soil mass is heated to a temperature level that is sufficient to
drive the contaminants off of the soil matrix, but not high enough
to actually incinerate or destroy the contaminants. Soil
contaminants are volatilized from the solids and purged from the
kiln or dryer by means of an inert purge gas. After the purge gas
leaves the desorption unit, it is treated by an off-gas treatment
system that prevents the soil contaminants from being released into
the environment. Typical air pollution control equipment (such as
cyclonic precipitators and baghouses) are also used to protect air
quality during operation of desorption units.
LTTD typically concentrates the Site contaminants into a low-
volume, highly concentrated waste stream that must in turn be
disposed of in a manner that complies with all environmental
regulations. This residual waste stream would be disposed of
either by incineration or by transport to an approved waste
disposal facility.
Numerous vendors for this type of treatment system exist, and EPA
h~s experienced good success with its use on soils contaminated
with pesticides at other Superfund sites. Treatability studies
. would likewise be necessary in order to assess the suitability of
this technology for application at the Helena Chemical Site. The
performance standard for this treatment system would likewise be
the LDRs for site specific contaminants.
The estimated cost for this alternative is $4.4 million.
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8.0
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The alternatives for Site remediation were evaluated based on the
nine criteria set forth in the NCP (40 CFR ~ 300.430(e) (9)). In
the sections which follow, brief summaries of how the alternatives
were judged against these criteria are presented.
8.1
CRITERIA FOR COMPARATIVE ANALYSIS
8 .1.1
Threshold Criteria
Two threshold criteria must be achieved by a remedial al~ernative
before it can be selected.
1. Overall protection of human health and the environment
addresses whether the alternative will adequately protect human
health and the environment from the risks posed by the Site.
Included in judgement by this criterion is an assessment of how and
whether the risks will be properly eliminated, reduced, or
controlled through treatment, engineering controls, and/or
institutional controls.
2. Compliance with applicable or relevant and appropriate
recruirements (ARARs) addresses whether an alternative wi11 meet all
of the requirements of Federal and State environmental laws and
regulations, as well as other laws, and/or justifies a waiver from
an ARAR. The specific ARARs which will govern the selected remedy
are listed and described in Section 9.0, Selected Remedy.
8.1.2
Primary Balancinq Criteria
Five criteria were used to weigh the strengths and weaknesses among
al'ternatives, and to develop the decision to select one of the
alternatives. Assuming satisfaction of the threshold criteria,
these are the main considerations in selecting an alternative as
the remedy.
1. Lonq term effectiveness and permanence refers to the ability of
the alternative to maintain reliable protection of human health and
the environment over time, once the remediation goals have been
met.
2. Reduction of toxicity I mobility I or volume addresses the
anticipated performance of the treatment technologies that an
alternative may employ. The 1986 amendment to CERCLA, the
Superfund Amendments and Reauthorization Act (SARA), directs that,
when possible, EPA should choose a treatment process that
permanently reduces the level of toxicity of site contaminants,
eliminates or reduces their migration away from the site, and/or
reduces their volume on a site. .'
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3. Short-term effectiveness refers to the length of time peeded to
achieve protection, and the potential for adverse effects to human
health or the environment posed by implementation of the remedy,
until the remediation goals are achieved.
4. Implementability considers the technical and administrative
feasibility of an alternative, including the availability of
materials and services necessary for implementation.
s. Cost includes both the capital (investment) costs to implement
an alternative, plus the long-term O&M expenditures applied over a
projected period of operation.
8.1.3
Modifyinq Criteria
State acceptance and community acceptance are two additional
criteria that are considered in selecting a remedy, once public
comment has been received on the Proposed Plan.
1. State acceptance:
this remedy.
The State of South Carolina concurs with
2. Community acceptance was indicated by the verbal. comments
received at the Helena Chemical NPL Site Proposed Plan public
meeting, held on May 27, 1993.. The public comment period opened on
May 18, 1993, and closed on June 17, 1993.
Written comments received concerning the Helena Chemical NPL Site,
and those comments expressed at the public meeting, are addressed
in the Responsiveness Summary attached as Appendix A to this ROD.
8.2
COMPARISON OF ALTERNATIVES
All alternatives, except Alternative 1, provide adequate protection
of human health and the environment. All alternatives, again with
the exception of Alternative 1, achieve all identified ARARs. With
respect to short-term effectiveness and implementability,
Alternatives 2-6 are all are comparable. Treatment Alternatives 3
through 6 achieve overall protectiveness and risk reduction by
permanently treating the waste and using the treated materials to
prevent contact with less affected soils beneath the treatment
areas. Landfill Alternative 2 achieves similar risk reductions,
but does not satisfy the statutory preference for reducing the
toxicity and volume of the waste, although the mobility. of Site
contaminants would be greatly reduced. Therefore, Alternatives 3-6
are preferable to Alternative 2.
Neither Alternative 3 nor Alternative 4 (biological treatment alone
or HPD alone) has been shown to be fully effective for the entire
range of pesticide contaminants found at the Site. The long-term
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effectiveness of Alternatives 3 and 4 is therefore less assured
than that for Alternatives 5 and 6. Alternative 6, treatment of
soils by LTTD, would make use of a proven treatment technology that
could reasonably be expected to achieve the remedial goals
specified in this ROD. Prelimina:ry studies regarding the proposed
technology described under Alternative 5 (combining biological
treatment with HPD) indicate that remedial goals for all Site
contaminants are likely to be achievable.
Alternatives 5 and 6, therefore, are those that best meet the
statuto:ry preference for permanent solutions that reduce the
toxicity, mobility and volume of waste materials while using
technologies that can reasonably be expected to achieve the
remedial goals determined to be protective of human health and the
environment, and to achieve ARARs. They also fulfill the other
criteria regarding long- and short-term effectiveness and
implementability. The projected cost for Alternative 5 is
significantly less than that for Alternative 6. Given that
Alternative 5 can be implemented at significantly less cost than
could Alternative 6, Alternative 5 is the preferred alternative.
EPA recognizes, however, that the preferred remedy includes a soil
treatment technology (HPD/biological treatment) that is an
innovative technology that has not been demonstrated capable of
achieving performance standards specified in Section 9, below. EPA
therefore will retain Alternative 6 as a contingency remedy to be
implemented should treatability studies of HPD/biological treatment
prove that this technology is incapable. of achieving the
performance standards for this Site. The only difference between
Alternative 5 and Alternative 6 is the soil treatment technology to
be employed. Alternative 6 contains low temperature thermal
desorption (LTTD) as the soil treatment technology.
9.0
THB SBLBC'l'BD RBMBDY
Based upon consideration of the requirements of CERCLA, the NCP,
the detailed analysis of alternatives and public and state
comments, EPA has selected a remedy that includes source control,
ground-water remediation, and mitigation for wetlands impacts for
this Site. At the completion of this remedy, the residual risk
associated with this Site will fall within the acceptable range
mandated by CERCLA and the NCP of 10-6 to 10-& which is determined
to be protective of human health. The unacceptable level of risk
posed to environmental receptors will also be adequately addressed.
The total present worth cost of the selected remedy, Alternative 5,
is estimated at $3.9 million.
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9.1
DESCRIPTION OF SELECTED REMEDY
9:1.1.
Source Control
Source control will address the contaminated' soils and waste
materials at the Site. Source control shall include excavation of
contaminated soils and waste materials, on-Site treatment by means
of combined hydrolytic/photolytic dechlorination (HPD) and
biological degradation, and placement of the treated soils and
waste materials back into on-Site excavations. The treated soils
will then be covered by a minimum of one foot of clean backfill.'
The major components of source control to be implemented include:
9.1.1.1.
Excavation
Excavation of materials contaminated with greater than 50 ppm of
total pesticides at the Site. Excavation will be limited to the
uppermost three feet of soils at the Site in order to prevent
creation of a preferential flow path for infiltration of rain water
into the shallow aquifer.
9..1.1.2.
Treatment of Excavated Soils
Treatment of all excavated materials by means of a combination of
hydrolytic/photolytic dechlorination and biological degradation.
Contaminated soils and waste materials containing greater than 50
ppm total pesticides from the Site would be treated by means of
hydrolytic/photolytic dechlorination (HPD) of the pesticide
contaminants. This process would be implemented at Helena Chemical
by mixing contaminated soils with chemical reagents and exposing
them to heat and ultraviolet (UV) radiation. The mixing process is
necessary to distribute the reagents (usually hydrated lime,
possibly supplemented by sodium hydroxide) throughout the mass of
contaminated material. The mixed material/reagent mass is then
placed in thin layers in cells similar to those proposed for
biological treatment in order for the soils to be exposed to heat
and UV energy from the sun. The soil mass would also be kept moist
in order to enhance biodegradation of any organic end products
resulting from the hydrolytic/photolytic dechlorination process.
Soils would be periodically .turned over. to maximize contaminant
exposure to UV radiation.
Contaminated soils containing greater than 50 ppm total pesticides
would also be treated on-site by means of biological degradation
subsequent to the HPD process steps. Biological degradation would
take place in treatment cells constructed on-site that would be
lined to prevent any leaching of contaminants to ground waters
underlying the Site. Treatability studies would be conducted to
determine if this alternative can achieve the remedial goals, but
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72
preliminary data indicate that significant reductions .in
concentration of many site-specific contaminants can be achieved by
biological degradation. Once soils are treated to the remedial
goals, they would be replaced in the on-site excavations from which
they were removed, and covered by a minimum of one foot of clean
fill. The performance standard for the combined treatment process
would be based upon the LDRs for site-specific contaminants.
Biological treatment cells would consist of lined pits into which
the contaminated soils would be placed. Once placed into the
cells, moisture content, temperature and nutrient levels wo~ld be
adjusted and maintained to maximize the rate of biological
activity. Both aerobic and anaerobic conditions are envisioned in
order to maximize the effect of biological degradation.
Anticipated treatment would consist of anaerobic treatment,
particularly for soils contaminated with DDT, followed bY aerobi~
treatment. Some of the Site soils may require aerobic treatment
alone. .
The final element of the source control portion of the .overall
remedy will be to grade the Site and construct any structures or
appurtenances necessary so. that the Site complies with all
regulations regarding storm water run off from industrial
facilities. This will prevent any further non-point source
contribution from future Site activities to contamination in
adjacent waters of the United States.
9.1.2. Ground Water Remediation
Groundwater remediation will address the contaminated groundwater
at the Site. Groundwater remediation will include extraction of
contaminated groundwater, treatment, and discharge to the local
Publicly Owned Treatment Works (POTW).
The major components of groundwater remediation to be implemented
include:
Extraction from the surficial aquifer by means of pumping wells and
treatment by standard treatment technologies generally available to
achieve pre-treatment requirements imposed by the POTW; and
Discharge of treated water to the nearest access point into the
sanitary sewer collection system serving the local POTW.
The installation of ground-water extraction wells will prevent the
migration of contaminants beyond the present extent of the
contaminant plume, and will over time remove contaminants from the
ground water lying beneath the Site. At present, the extent of
contaminated ground water is confined to the shallow aquifer (the
Barnwell Formation) and does not appear to extend to.. any
significant degree laterally to off-site areas, although one well
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located off the Site property (MW-18) was contaminated during the
RIo
-.
Extracted ground water will be treated to criteria appropriate for
the final means of disposal. At present, it is planned that the
extracted ground water will be treated and discharged to the local
sanitary sewer system, also known as a POTW. Pretreatment
requirements will be set by the owner/operator of that sanitary
sewer system in order to insure that the discharge permit for the
system will not be violated. It is possible, based upon initial
estimates of ground-water quality, that no pretreatment will be
necessary; for the purposes of preliminary cost estimates, however,
it is assumed that some degree of pretreatment for extracted ground
water will be required. The actual technologies to be employed
will be based upon-the pretreatment criteria established by the
owner/operator of the POTW.
Extraction of contaminated ground water will continue until the
ground-water remediation goals are met throughout the extent of the
plume. Should it prove to be technically impracticable to achieve
these remedial goals, EPA will amend the ROD to reflect any changes
in remediation criteria.
9.1. 3
Wetlands Mitiqation
Mitigation for contaminated soils and sediments in the wetland
areas adjacent to the Site and downstream can be accomplished in a
number of ways under the regulations, guidelines and criteria
established under Section 404(b) (1) of the Clean Water Act, which
is an ARAR for the remedial action at this Site. These guidelines
and criteria include the MOA between EPA and the Corps of
Engineers, effective date February 7, 1990, concerning the
determination of mitigation. Removal of the fill placed in the
affected wetlands, accompanied by removal of the contamination that
has resulted from transport of toxic materials from that fill, is
one potential method. Another would be the restoration of degraded
wetlands at some off-site location. Another possibility is the
acquisition of unaffected wetlands that are currently threatened by
development or other destructive activities and placing those
wetland areas in a protected status. A number of factors will be
used to determine the most cost-effective and environmentally sound
manner in which compliance with the mitigation guidelines will be
achieved.
The exact form of mitigation for the effects of contaminated
sediments will be based in part upon the consideration that,
al.though the sediments are contaminated to a level that is expected
to adversely impact flora and fauna normally found in such a
habitat, and that therefore pose an unacceptable level of risk to
environmental receptors, the habitat function has not been
completely destroyed. In addition, other valuable wetland
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functions remain intact and could conceivably be physically
destroyed by an active removal of contaminated sediments. Physical
reconstruction of wetland areas damaged by such physicai
disruptions is theoretically possible, but EPA's experience with
reconstructed wetlands as part of regulatory actions taken under
the authority of Section 404 of the Clean Water Act has been that
limited success can be expected from such projects. Also,
reasonable estimates of the time required to achieve full
restoration of the existing wetlands under this approach may be
similar to that required for natural attenuation and biodegradation
of site-related contamination to insignificant concentrations.
Finally, it is possible that other sources of pesticide
contamination exist that will not be addressed as part of the
remedy for the Helena Chemical Site, since those sources are not
related to the Site or activities that took place at the Site.
Even should a successful reconstruction of contaminated wetlands be
achieved, it is possible that these other sources wbuld re:-
contaminate the wetland areas adjacent to the Helena Site,
rendering the reconstruction ineffective in the long term.
Executive Order 11990, and regulations related to that Order found
at 40 CFR Part 6, will also be considered in determining the most
effective means by which the mitigation will be accomplished.
These regulations require EPA to avoid, to the extent possible, the
adverse impacts associated with the destruction or loss of wetlands
and to avoid direct or indirect support of new construction in.
wetlands if a practicable alternative exists. Mitigative measures
consistent with these requirements will therefore be given
preference in determining specific actions to be required as part
of the remedial action.
By insuring that adequate habitat for ind Tenous species
potentially found in the wetlands associated with ne Site will be
made available by the mitigative measures proposed, the adverse
impacts to. the habitat function of the Helena wetlands can be
remedied. While individuals of these species may under some
mitigative options continue to be impacted by toxic effects of
contaminants in the sediments at the Site, the viability of the
various species populations in the area will be protected and
enhanced by the long-term stability and availability of suitable
habitat provided for by mitigation as part of the remedy.
9.1.4.
Compliance Testinq
Monitoring of groundwater (both in situ and after extraction and
treatment), excavated soils, and treated soils shall be conducted
as part of this remedial action. After demonstration of compliance
with Performance Standards, Site ground water shall be monitored
for five years. If monitoring indicates that the Performance
Standards set forth below are being exceeded at any time after
pumping has been discontinued, extraction and treatment of the
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ground water will recommence until the Performance Standards are
once again achieved.
Compliance testing of the residual soils that have been subjected
to treatment will also be performed, to insure compliance with the
LDR requirements established as performance standards for' the soil
treatment technology. .
9.1.5
Continqenev Remedy
Should treatability studies demonstrate that the selected remedy
described above, HPD/biological treatment, cannot achieve
performance standards established for the Site, the treatment
technology used for soil remediation at the Site will be low
temperature thermal desorption (LTTD) in lieu of HPD(biological
treatment. LTTD has been successfully used at other NPL sites with
similar soil contaminants and levels of contamination, and
therefore can be expected to satisfactorily achieve performance
standards at this Site.
Using this technology, contaminated soils exceeding 50 ppm total
pesticides from the Site would be treated on-site by means of low
temperature thermal desorption (LTTD). This process involves
processing contaminated soils through a rotary dryer or kiln. The
soil mass is heated to a temperature level that is sufficient to
drive the contaminants off of the soil matrix, but not high enough
to actually incinerate or destroy the contaminants, Soil
contaminants are volatilized from the solids and purged from the
kiln or dryer by means of an inert purge gas. After the purge gas
leaves the desorption unit, it is treated by an off-gas treatment
system that prevents the soil contaminants from being released into
the environment. Typical air pollution control equipment (such as
cyclonic precipitators and baghouses) are also used to protect air
quality during operation of desorption units.
Numerous vendors for this type of treatment system exist, and EPA
has experienced good success with its use on soils contaminated
with pesticides at other Superfund sites. Treatability studies
would likewise be necessary in order to assess the suitability of
this technology for application at the Helena Chemical Site. The
performance standard for this treatment system would likewise be
the LDRs for site specific contaminants.
9.2.
APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARs)
9.2.1.
Applicable Reauirements
The remedy will comply with all applicable
following Federal and State regulations:
portions' of
the
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40 CFR Part 6, Subpart C, promulgated under the authority of the
National Environmental Policy Act. Specifically:
Section 6.302(a), governing protection of wetlands, including
referenced Appendix A to 40 CFR Part 6. These regulations
incorporate Federal Executive Order 11990 into Federal
regulation.
40 CFR Part 122, promulgated under the authority of the Clean Water
Act. Specifically:
Section 122.26,
industrial &ites.
governing
storm
water
discharges
from
Section 122.50, governing
treatment works (POTWs).
40 Part 136, promulgated under the authority of the Clean Water
Act. These regulations govern the water quality testing of
discharges associated with NPDES-related activities. For this Site
they are applicable to testing of waters discharged to a POTW and
to the testing of storm water discharges.
discharges
to
publicly
owned
South Carolina Code of Regulations (SCCR) Chapter 61-72, governing
the discharge of storm waters from industrial sites. Specifically:
Section 72.307, containing design criteria for storm water
discharge facilities.
SCCR Chapter 61-69, governing ambient water quality standards for
surface and ground waters. Specifically:
Section 61-68(C), establishing applicability of state water
quality standards.
Section 61-68(E), establishing minimum criteria for all state
waters.
Section 61-68(F), establishing ambient standards for surface
waters.
Section 61-68(G), establishing ambient standards for ground
waters.
9.2.2.
Relevant and ApproDriate Reauirements
40 CFR Part 141, promulgated under the authority of the Safe
Drinking Water Act. Specifically:
Maximum Contaminant Levels (MCLs) and Maximum Contaminant
Level Goals (MCLGs) promulgated under the authority of the
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Safe Drinking Water Act are specifically identified in the
National Contingency Plan (NCP) as remedial action objectives
for ground waters that are current or potential sources of
drinking water supply. The ground waters underlying this Site
are classified as Class IIA ground waters under the EPA
Guidelines for Ground-Water Classification. Ground-water
extraction and treatment is included in this remedy in order
to satisfy EPA's stated goal of returning usable ground waters
to their beneficial uses within a reasonable time frame (see
FR Vol. 53, no. 245, p 51433, and Section 300.430(a) (1) (ii) (F)
of the NCP). MCLs and MCLGs are therefore relative and
appropriate for use as remedial action obj ecti ves for the
remedial action at this Site.
Maximum Contaminant Level Goals (MCLGs) are found in 40 CFR
Part 141, Subpart F.
Maximum Contaminant Levels
141, Subparts Band G.
(MCLs) are found in 40 CFR Part
40 CFR Part 230, Subparts Band H, promulgated under the authority
of the Clean Water Act. These regulations govern the mitigation of
impacts to jurisdictional wetlands associated with the placement of
fill material in waters of the United States and any secondary
adverse impacts resulting from that placement.
Since the solid waste on-Site is not hazardous waste, but contains
hazardous constituents, the following regulations established under
the authority of RCRA are relevant and appropriate to the
circumstances of the release, but are not directly applicable.
This includes regulations found at 40 CFR Parts 261-268 cited
below.
40 CFR Part 261, Subpart B. These regulations establish methods
for the testing of hazardous materials at RCRA-regulated
facilities. They will be used to guide testing procedures
established as part of the compliance monitoring portion of this
remedy.
40 CFR Part 264, Subpart B, established under the authority of
RCRA. Specifically:
Section 264.14, establishing criteria for Site security.
Section 264.15, establishing criteria for inspection of the
Site by the owner/operator.
Section 264.16, establishing criteria for training
personnel who will be involved in Site remediation.
of
40 CFR Part 264, Subpart D, which requires the development of a
contingency and emergency procedures plan for the Site.
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40 CFR Part 264, Subpart F, which governs releases from solid waste
management units. Specifically:
Section 264.95, which requires the establishment of a point of
compliance for ground-water protection standards. The
performance standards established in this ROD for ground-water
remediation will serve as the ground-water protection
standards. A point of compliance will be established at the
downgradient boundary of the final disposal site for treated
soils and waste materials.
Section 264.97, which establishes requirements for a ground-
water monitoring program. These requirements will be used to
establish a ground-water monitoring program for the purpose of
evaluating rel~ases from the final disposal site for treated
soils and waste materials.
Section 264.98, which established requirements for a detection
monitoring program. This detection monitoring program will be
used to evaluate potential releases from the final disposal
site for treated soils and waste materials. . .
40 CFR Part 264, Subpart G, which governs closure of solid waste
management units. Specifically:
Section 264.111,
standards.
which
sets
forth
closure
performance
Section 264.112, which requires the submission of a closure
plan for review and approval.
40 CFR Part 268, Subpart D, which establishes treatment standards
which must be achieved prior to land disposal of hazardous wastes.
These regulations will establish the performance standards for
treatment of contaminated soil and waste materials excavated from
the Site.
Federal Ambient Water Quality Criteria (AWQC) established under the
authority of Section 304(a) of the Clean Water Act.
These criteria are specifically identified in Section
121 (d) (2) (A) of CERCLA as amended by SARA to be ARARs for
CERCLA remedial actions. AWQC are developed as guidance fo~
the States to develop ambient surface water quality standards
that will be fully protective of human health and the
environment. As such, AWQC are relevant and appropriate to
the selected remedial action. Discharge of the treated
effluent from this site must not result in ambient surface
water concentrations that exceed chemical-specific AWQC.
SCCR Chapter 61-79, which contain the State of South Carolina
regulations governing the management, treatment, storage and
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disposal of hazardous wastes. These regulations are, in a manner
analogous to Federal RCRA regulations, relevant and appropriat~. to
the circumstances of the releases from this Site without being
directly applicable. In addition, since the South Carolina
regulations simply incorporate verbatim the Federal RCRA
regulations, the sections of SCCR Chapter 61-79 corresponding to
the Federal RCRA sections cited above are hereby incorporated into
this ROD as relevant and appropriate requirements.
9.2.3
Criteria "To Be Considered"
CERCLA guidance recommends the identification of criteria that may
be relevant and appropriate to the circumstances of the release at
a site, but which do not meet the statutory definition of an ARAR.
To be defined as an ARAR, a standard or criterion must be a
requirement or regulation promulgated under Federal or state
authority, and must be of general applicability. Other standards
or criteria, known as criteria to be considered or TBCs, may be
necessary in order for the remedy to be fully protective of human.
health and the environment. These TBCs may include EPA reference
doses, cancer potency factors, drinking water health advisories or
other health-based criteria.
A number of TBC criteria have been identified for ground-water
remediation at the Helena Chemical NPL Site. They are based upon
protection of human health via drinking water exposure, using data
contained in EPA data bases regarding toxicity and/or
carcinogenicity of these compounds, and also using standard
assumptions regarding intake and exposure via drinking water.
. The following TBC criteria have been developed based upon an
incremental carcinogenic risk of 1 X 10-6:
Aldrin 0.002 parts per billion (ppb)
alpha-BHC 0.006 ppb
beta-BHC 0.020 ppb
delta-BHC 0.006 ppb
Dieldrin 0.002 ppb
DDT 0.100 ppb
DDD 0.100 ppb
DDE 0.100 ppb
The following TBC criteria are based upon non-carcinogenic toxicity
(hazard index less than 1) :
Disulfoton
Endrin Ketone
Lead
1. 400 ppb
2.000 ppb
15.000 ppb
In addition, the Memorandum of Agreement between EPA and th~ U.S.
Army Corps of Engineers concerning the determination of mitigation
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under the Clean Water Act Section 404(b) (1) guidelines ia also a
TBC criterion for remedial actions related to wetlands mitigation
at this Site.
9.3. PERFORMANCE STANDARDS
The Performance Sta~dards for this component of the selected remedy
include the following:
9.3.1.
Excavation Standards
Excavation shall continue until the remaining soil and materials
are contaminated at a concentration of no more than 50 parts per
million (ppm) total pesticides. Total pesticides. shall be
determined by summing the concentrations of all pesticides found in
any soil sample analyzed for the pesticides fraction of the
Hazardous Substances List (HSL). Testing methods approved by EPA
shall be used to determine if the allowable pesticide concentration
levels have been achieved.
9.3.2.
Treatment Standards
Since the remedy also specifies land disposal of the treated waste,
the LDR-based ARARs are also performance standards for the residue
left after treatment of the soils and waste. These performance
standards are found in 40 CFR Part 268, Subpart D, Section 268.43.
They are:
From Table CCW1:
total
66
660
130
130
100
87
130
66
130
66
66
180
1300
per billion (ppb)
Aldrin
BHC, all isomers, total
Chlordane, total
Dieldrin
Disulfoton
DDT, DDE, DDD, total
Endrin
Endosulfan, all isomers,
Endosulfan sulfate
Heptachlor
Heptachlor epoxide
Methoxychlor
Toxaphene
parts
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
Note 1: Compliance
treatment residue.
to be determined by
grab samples
of
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9.3.3.
Ground-Water Remediation Standards
81
Groundwater shall be extracted until the following Maximum
Concentration Levels (MCLs) are attained at the wells designated
during remedial design by EPA as compliance points.
Aldrin
Benzene
alpha-BHC
beta-BHC
delta-BHC
Chlordane
Chromium
Dieldrin
DDT
DDD
DDE
Endrin
Lead
Lindane
Toxaphene
Heptachlor
0.002
5.0
0.006
0.02
0.006
2.0
100.0
0.002
0.1
0.1
0.1
2.0
15.0
0.2
3.0
0.4
parts
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
ppb
per billion (ppb)
9.3.4
Storm Water Discharqes
Final Site grading and drainage shall comply with the substantive
design criteria contained in SCCR Chapter 61-72, Section 72.307.
9.3.5
Wetlands Mitiqation
Wetlands mitigation actions taken as part of this remedy shall
comply with the substantive requirements of 40 CFR Part 230,
Subparts Band H, promulgated under . the authority of the Clean
Water Act. These regulations govern the mitigation of impacts to
jurisdictional wetlands associated with the placement of fill
material in waters of the United States and any secondary adverse
impacts resulting from that placement. Quantitative performance
standards. shall be established as part of remedial design
activities.
Mitigation activities shall also comply with the requirements of 40
CFR Part 6, Subpart C, promulgated under the authority of the
National Environmental Policy Act. Specifically:
Section 6.302(a), governing protection of wetlands, including
referenced Appendix A to 40 CFR Part 6. These regulations
incorporate Federal Executive Order 11990 into Federal
regulation.
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10.0
STATUTORY DETERMINATIONS
The selected remedy for this Site meets the statutory requirements
set forth at Section 121(b) (1) of CERCLA, 42 U.S.C. ~ 9621(b) (1).
This section states that the remedy must protect human health and
the environment; meet ARARs (unless waived); be cost-effective; use
permanent solutions, and alternative treatment technologies or
resource recovery technologies to the maximum extent practicable;
and finally, wherever feasible, employ treatment to reduce the
toxicity, mobility or volume of the contaminants. The
following sections discuss how the remedy fulfills these
requirements.
Protection of human health and the environment: The selected soil
remedy will remove the human health risks from dermal contact and
incidental ingestion of contaminated Site soils. The groundwater
remediation system will extract and treat contaminated groundwater,
thereby reducing and eventually removing the future risks to human
health which could result from ingestion of or contact with
groundwater, and the environmental risks which could result from
continued discharge of contaminants to adjacent jurisdictional
waters.
In addition, the remedy selected to address the contamination of
surface waters and sediments in the on-Site and adjacent wetlands
(mitigation as per CWA Section 404 guidelines) will be protective
of the environment.
Compliance with ARARs: The selected remedy will meet ARARs, which
are listed in Section 9.2of this ROD.
Cost effectiveness: The selected soil remedy component is the most
cost effective of the alternatives considered. Among the
alternatives that are protective of human health and the
environment and comply with all ARARs, the selected alternative is
the most cost-effective choice because it uses a treatment method
for which costs can be reliably predicted and because the use of
the POTW option is the most cost-effective means to dispose of the
treat~d groundwater.
Utilization of permanent solutions, and alternative treatment
technoloqies or resource recovery technoloqies to the maximum
extent practicable: The selected remedy represents the maximum
extent to which permanent solutions and treatment can practicably
be used for this action. All of the selected remedy components are
considered permanent solutions.
Among the alternatives that are protective of human health and the
environment and comply with all ARARs, EPA and the State of South
Carolina have determined that the selected remedy achieves the best
balance of trade-offs in terms of long-term effectivenes~ and
permanence, reduction of toxicity/mobility/volume, short-term
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effectiveness, i!nplementability, and cost. The 8elected
groundwater action i8 more readily implementable than the other
alternatives considered, and utilizes the mo8t c08t-effective
option for disposal of treated water. The selected 80il remedial
action achieves the best cOD;)liance with the five balancing
criteria described in the NCP. .
Preference for treatment a8 a DrinciDal remedv element: The
proposed groundwater remediation system will fulfill the preference
for treatment a8 a principal element, through extraction and
treatment of contaminated groundwater until the remedial goals are
achieved.
The 80il remedial action will a180 sati8fy the preference, due to
the treatment of soi18. b.y the 8elected technology,
HPD/biodegradation. Likewi8e, the contingency remedy fully
satisfies this preference.
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