NCD062555792_20011018_Sigmons Septic Tank Service_FRBCERCLA RISK_Baseline Risk Assessment Work Plan - RI FS-OCR

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SUPE11_[_JJN[UECTION
BASELINE RISK ASSESSEMENT
WORK PLAN
REMEDIAL INVESTIGATION/
FEASIBILITY STUDY
SIGMON'S SEPTIC TANK SITE
STATESVILLE, IREDELL COUNTY,
NORTH CAROLINA
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DRAFT
BASELINE RISK ASSESSMENT WORK PLAN
REMEDIAL INVESTIGATION/FEASIBILITY STUDY
SIGMON'S SEPTIC TANK
Statesville, Iredell County, North Carolina
USEPA Work Assignment 040-RICO-A44F
Black & Veatch Project No. 48140.0101
Prepared Under
EPA Contract No. 68-W-99-043
October 18, 2001
Prepared by
Black & Veatch Special Projects Corp.
1145 Sanctuary Parkway, Suite 475
Alpharetta, Georgia 30004
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Table of Contents
Section: TOC
Draft
Revision Date: October 18, 2001
Page i of ii
Page N°.
1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
I.I Site Description ...................................................... 1-1
1.2 Operational History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
1.3 Previous Investigations ................................................ 1-6
1.4 Baseline Risk Assessment Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
1.5 Organization of the Baseline Risk Assessment ............................. 1-16
2.0 Baseline Human Health Risk Assessment ..................................... 2-1
2.1 Data Evaluation ............ , ......................................... 2-1
2.1.1 Evaluating Data Quality .......................................... 2-1
2.1.2 Identification of CO PCs .......................................... 2-2
2.1.3 Data Summary .................................................. 2-4
2.2 Exposure Assessment ................................................. 2-4
2.2.1 Conceptual Site Model ............................................ 2-5
2.2.2 Physical Setting ................................................. 2-5
2.2.3 Contaminant Sources, Release Mechanisms, and Migration Pathways ...... 2-7
2.2.4 Receptors and Exposure Pathway Descriptions ........................ 2-7
2.2.5 Quantification of Exposure ....................................... 2-13
2.3 Toxicity Evaluation .................................................. 2-16
2.3.1 Cancer Evaluation .............................................. 2-16
2.3.2 Evaluation ofNoncancer Effects ................................... 2-19
2.3.3 Dermal Toxicity Values .......................................... 2-20
2.3.4 Target Organ Toxicity ........................................... 2-20
2.3.5 Sources of Toxicity Information ................................... 2-21
2.4 Risk Characterization ................................................. 2-22
2.4.1 Cancer Risk ................................................... 2-22
2.4.2 Noncancer Hazards of Chemicals .................................. 2-23
2.4.3 Risk Characterization Results ..................................... 2-25
2.5 Remedial Goal Option Development .................................... 2-25
2.5.1 Selection of Chemicals of Concern ................................. 2-25
2.5.2 Remedial Goal Options Estimation Methodology ...................... 2-26
2.6 Uncertainty Analysis ................................................. 2-27
2.6. l Types of Uncertainty ............................................ 2-28
2.6.2 Sources of Uncertainty .......................................... 2-28
2.7 Human Health Risk Conclusions ........................................ 2-29
3 .0 References .............................................................. 3-1
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section: TOC
Draft
Revision Date: October 18, 2001
Page ii of ii
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Tables
Table 1-1
Table 1-2
Table 1-3
Table 2-1
Table 2-2
Figures
Figure 1-1
Figure 1-2
Figure 1-3
Figure 2-1
Table of Contents (Continued)
Page N2•
Analytical Results for ES! Soil Samples .............................. 1-11
Analytical Results for ES! Groundwater Samples ....................... 1-13
Analytical Results for ES! Surface Water Samples ...................... 1-14
Selection of Exposure Pathways ..................................... 2-8
Variables Used to Estimate Potential Chemical Intakes .................. 2-10
Site Location Map ................................................ 1-2
Site Layout Map .................................................. 1-3
ES! Sample Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
Conceptual Site Model ............................................. 2-6
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
1.0 Introduction
Section 1
Draft
Revision Date: October 18, 2001
Page 1 of 18
The purpose of this Baseline Risk Assessment Work Plan is to describe the protocol for evaluating risk to
human health receptors associated with soil, groundwater, surface water, and sediment at the Sigmon's
Septic Tank site. The primary objective of the Baseline Risk Assessment (BLRA) is to provide risk-based
information to be used as input for site management decisions.
This Work Plan is intended to serve as the template for the BLRA, which will comprise a section of the
Remedial Investigation (RI) report. The BLRA will include all the equations and variable values necessary
for quality control (QC) and replication of computations used to calculate risks associated with the soil,
groundwater, surface water, and dry sediment underlying the site. Human health risk methods and results
will be presented in the Baseline Human Health Risk Assessment (BHHRA).
1.1 Site Description
The Sigmon's Septic Tank Site is located at 1268 Eufola Road, approximately 5 miles southwest of
Statesville, Iredell County, North Carolina(NCDENR, 1998, NCDENR, 2000). The site lies between
Eufola Road to the north and Lauren Drive to the south and is surrounded by private residences to the east
and west (BVSPC, 2001). The site location map is shown on Figure 1-1.
Sigmon's Septic Tank Site occupies approximately 15.35 acres, including a lagoon areaofapproximately
1.2 acres (USGS, 1999). The site contains three buildings: the home ofMary Sigmon, the work location
of Sigmon Environmental Services Inc. (current name of the septic tank service), and a storage shed
(NCDENR, 2000). The east, west, and south boundaries of the site are fenced and signs are posted
warning of the disposal area; however, access to the site is possible due to breaks in the fence. The site
layout map is shown on Figure 1-2.
Surface water runoff flowing to the southwest, south, and southeast is intercepted by a drainage ditch on
the north side of Lauren Drive. The ditch carries the flow approximately 650 feet east to a culvert under
Lauren Drive. The culvert discharges on the south side ofLauren Drive approximately 20 feet from the
Davidson Pond. Therefore, if the flow is sufficient, surface water runoff from the site reaches the Davidson
Pond.
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REF. -USGS 7 .5 MINUTE SERIES TOPOGRAPHIC MAP: TROUTMAN, NC 1993.
SITE LOCATION MAP
SIGMON'S SEPTIC TANK SITE
STATESVILLE, IREDELL COUNTY, NORTH CAROLINA
1" = 3,000'
FIGURE
1-1
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--' • • .. . -·--------
REF. -USGS 7.5 MINUTE SERIES TOPOGRAPHIC MAP: TROUTMAN, NC 1993.
SITE LAYOUT MAP
SIGMON'S SEPTIC TANK SITE
STATESVILLE, !REDELL COUNTY, NORTH CAROLINA
1" = 600'
FIGURE
1-2
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section I
Draft
Revision Date: October 18, 200 I
Page 4 of 18
Surface water runoff flowing from the site to the northwest and west enters an intermittent stream northwest
of the site. This stream flows for approximately 950 feet and joins another intermittent stream. The second
intermittent stream carries runoff from the Lambreth pond to the Williams pond. The Lambreth pond is
located to the west of the site near the Lambreth residence. From the confluence of the two streams the
surface water flows into a wetland area before entering Williams pond. Drainage from the Williams pond
enters an intermittent stream and flows southwest approximately 2,100 feet to the two consecutive
successive ponds owned by the Sliwinski family. Drainage from these ponds is intermittent. This
intermittent stream flowing from the Sliwinski ponds and the intermittent stream flowing from the northeast,
the Davidson pond, converge at an unnamed perennial tributary of the Catawba River. The unnamed
tributary flows southwest for 4,700 feet to the confluence with the Catawba River/Lake Norman.
The immediate vicinity of the Sigmon Septic Tank facility is sparsely populated, and includes primarily rural
residential and agricultural use. The facility is bounded on the east, west, north, and south by residential
and agricultural areas.
Figure 1-3 provides a site vicinity map.
The region surrounding the site in Iredell County has a temperate climate characterized by mild winters and
warm summers. Average temperatures range from a high of75 degrees Fahrenheit (°F) in summer to a
low of 44° F in winter, with a mean annual temperature of 60° F (NCDC, 2000). The normal daily
maximum temperature is 89°F in July (NCDC, 2000). The normal daily minimum temperature is 30°F
in January (NCDC, 2000).
The average wind speed is 7.4 miles per hour (mph) (NCDC, 2000). The average wind speed is highest
in spring. The maximum wind speed is 46 mph from the west (NCDC, 2000).
Normal annual total precipitation in Iredell County averages 48 inches while mean annual evaporation is
approximately 40 inches, yielding a net mean annual precipitation of 8 inches (USDC, 1979). The 2-year,
24-hour rainfall averages 3.5 inches (USDC, 1961).
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REF'S. -USGS 7.5 MINUTE SERIES TOPOGRAPHIC MAP: TROUTMAN , NC 1993; NCDENR, ESI REPORT SIGMON'S SEPTIC TANK SERVICE, MARCH 2000.
SIGMON'S SEPTIC TANK SITE
STATESVILLE, !REDELL COUNTY, NORTH CAROLINA
HISTORICAL SAMPLING LOCATIONS
DECEMBER 1999 ESI
1" = 600'
FIGURE
1-3
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
1.2 Operational History
Section I
Draft
Revision Date: October 18, 2001
Page 6 of 18
The Sigmon family has owned and operated a septic tank pumping and waste disposal business since
1970. The Sigmon' s Septic Tank Service, a wholly owned subsidiary of AAA Ehterprises, pumped septic
tank wastes and heavy sludge from residential, commercial, and industrial custombrs, installed and repaired I
septic tanks, and provided a variety of industrial waste removal services. From 1970 to 1978, the
wastewater generated from the operations at Sigmon' s Septic Tank Service wJre discharged to the City I
of Statesville wastewater treatment plant. From approximately 1973 to I 97f, the sludges were land
applied to area farmlands. From 1978 to 1992, Sigmon's Septic Tank Service ?isposed of septic wastes
in eight to ten unlined lagoons on the south section of the 15-acre site. The total lagoon area is
approximately 1.2 acres. The wastes were described as septage, grease, 1and milky white liquid
(NCDENR, 2000).
In 1995, the North Carolina Division ofEnvironmental Management (DEM) required that the lagoons be
closed. According to AAA Enterprises, seven of the eight lagoons were prope~ly closed in accordance
with the DEM Notice ofRegulatory Requirements (NCDENR, 2000). How+er, although the lagoon
sludges were excavated to a depth of IO feet and mixed with sawdust, the excavated waste was piled
onsite adjacent to the lagoon area. The lagoons were backfilled with soil froJ the north portion of the
Sigmon's property. The waste pile and lagoons still remain on site.
In January 1996, Mary Sigmon, daughterofthe late owner, Henry Sigmon, formed Sigmon Environmental
Services (SES), which is currently active at the property. Both Sigmon's Septi6 Tank Service and AAA
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Enterprises ceased operations for financial reasons in September 1995 (NCDENR, 2000). SES is an
active septic removal business. Septic wastes are temporarily stored in above grolmd tanks on the property,
and the sludges are periodically removed and transported to a wastewater &eatment plant for disposal.
1.3 Previous Investigations
The Sigmon's Septic Tank site first came to the attention of the North CarolinaDepartmentofNatural
Resources and Community Development (NRCD) and the Iredell County Hell th Department in June
1980, on a site inspection to investigate the septage disposal problems of the are~. In September of 1980,
temporary monitoring wells were installed by the NRCD and DEM, at the reqJest of the Department of
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon 's Septic Tank Site
Section l
Draft
Revision Date: October 18, 2001
Page7of18
Human Resources. Samples were analyzed for alkalinity, bicarbonate, carbonate, chloride, dissolved
solids, hardness, and pH (NCDENR, 2000).
In November 1980, Mr. Sigmon submitted an interim status hazardous waste permit application (EPA Part
A) indicating that the site was used for disposal ofhazardous waste. In June 1981, Mary Sigmon, daughter
and current owner of the septic tank service, requested that the permit application be withdrawn because
they were no longer transporting hazardous waste. In April 1982, Mary Sigmon requested the facility be
re-classified as a transporter of hazardous waste (NCDENR, 2000).
In 1987, four additional temporary monitoring wells were installed and sampled by DEM (MW 1 through
MW 4). Analytical results were compared to EPA Drinking Water MCLs and/or North Carolina Title
I SA Subchapter 2L Classification and Water Quality Standards Applicable to Groundwater. The following
sample results were above the applicable standards: nitrates, barium, chromium, copper, iron, mercury,
manganese, and lead. During this investigation lagoon samples were also collected.
During a 1990 site investigation, Keith Masters of the Hazardous Waste Compliance Unit observed that
surface impoundments numbers eight and nine had been closed out. Surface impoundments numbers seven
and ten contained water run-off from the six operating ponds and were connected by a septic T. The
waters collected in these two ponds were used for irrigation purposes.
Sigmon's Septic Tank Service received a Notice ofViolation from DEM on August 9, 1990, regarding
the groundwater contamination. Sigmon's was required to submit a site assessment report and to install
two new monitoring wells to replace MW! and MW2, which had been damaged. The two new monitoring
wells were installed in the same location as the original wells. The site was referred to the NC Hazardous
Waste Section in September 1990, based on the 1987 lagoon sampling analytical results
In 1991, groundwater samples were collected by DEM from nearby drinking water wells. The analytical
results revealed elevated levels of metals and organics.
In 1992, DEM and the Hazardous Waste Section conducted an on-site investigation of the Sigmon site
lagoons. Analytical results from this sampling indicated elevated levels of7 metals and 13 volatile organics
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section 1
Draft
Revision Date: October 18, 2001
Page 8 of 18
in the aqueous lagoon samples and 4 metals and 18 volatile organics in the sludge samples. However, all
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recorded levels were below RCRA Toxicity Characteristic Leachate Procedure (TCLP) levels for toxicity
characteristics. Accordingly, the Hazardous Waste Section referred the sitb to the NC Solid Waste
Section because the chemical constituents within the lagoons did not meet tJe statutory definition of
hazardous waste.
In May 1993, DEM noted levels of mercury, lead, 2-chlorotoluene, benzene, ,1 ,3,5-trimethylbenzene,
-butylbenzene, and naphthalene above the NC 2L groundwater standards in Jo monitoring wells. The
Sigmon's were subsequently ordered to supply an alternate drinking water sourde for two residences that I
were approximately 400 feet from the lagoon area. In September 1993, AAA Enterprises contracted
Shield Environmental Associates to analyze samples from the lagoon area. Re~ults from these samples
indicated elevated levels of petroleum hydrocarbons, metals, and organic dompounds.
According to AAA Enterprises, seven of the eight lagoons were closed in accolance with DEM Notice
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of Regulatory Requirements for I SA NCAC 2L .0106 (f) (3) and ( 4) in I 995. The excavated waste was
piled onsite adjacent to the lagoon area and the lagoon sludge was excavated 1to a depth of IO feet and
mixed with sawdust. Subsequently, the lagoons were filled with soil from th~ northern portion of the
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Sigmon's property. The site was then referred to the NC Superfund Section by DEM with the possibility
of emergency removal of the waste pile. However, land application of the slJdge was considered but
denied due to sufficient acreage to apply the sludge.
In September 1995, both Sigmon's Septic Tank Service and AAA Enterprises ceased operations for
financial reasons. In January 1996, Mary Sigmon formed Sigmon Environmenthl Services (SES), that is
currently active at the site. SES was permitted as a septage management firm by the NC Solid Waste
Section to discharge septage to a nearby wastewater treatment facility. In Decdmber 1996, the site was I
added to CERCLIS database for further investigation. In January 1997, theiNC Superfund Section
referred the site to Region IV EPA Emergency Response and Removal Branchlforremoval evaluation.
EPA subsequently determined that the site did not meet removal eligibility]
In 1998, the Superfund Section conducted a Combined Preliminary Assessmlt/Site Inspection of the
Sigmon's Septic Tank Service. The investigation confirmed the presence of groimdwatercontamination
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section 1
Draft
Revision Date: October 18, 2001
Page9 of 18
south and east of the Sigmon's property and the presence of organic and inorganic compounds within the
waste pile and the lagoon. Barium, chromium, lead, manganese, mercury, chlorobenzene, 1,4-
dichlorobenzene, and 1,2-dichlorobenzene were detected within several wells. The surface water
pathways were also of concern. Two of the four primary points of entry (PPEs) were documented as
fisheries and sampling results detected barium, chromium, lead, and manganese within one of the fisheries
(Davidson pond) and magnesium within the other fishery (unnamed tributary).
On December 6 and 7, 1999, the North Carolina Superfund Section conducted sampling for the Expanded
Site Investigation (ES!) at the Sigmon Septic Tank site. Ten surface and subsurface soil, six sediment and
surface water, and nine groundwater samples were collected and analyzed during the ES!. Four of the soil
samples were collected from three lagoons that exhibited signs of stressed vegetation. Two of the soil
samples were collected from the waste piles. The last two soil samples were collected from the drainage
ditches along Lauren Dr., west and east of the Davidson pond. Two background soil samples were also
collected. Five sediment and surface water samples were collected from the Davidson pond and the
unnamed tributary. The background sediment sample was collected upstream on the unnamed tributary.
Seven of the groundwater samples were collected from private residential wells (Cascadden, Lambreth,
and Potts families), and one of the groundwater samples were collected from an on-site monitoring well.
The background monitoring well was located Northwest of the Lambreth/Potts well.
Organic and inorganic constituents detected in onsite surface and subsurface soils include: antimony at42
mg/kg, barium at 1,400 mg/kg, cadmium at 4.6 mg/kg, chromium at 140 mg/kg, copper at 380 mg/kg,
lead at 250 mg/kg, magnesium at 4,100 mg/kg, manganese at 290 mg/kg, nickel at 350 mg/kg, potassium
at 3,200 mg/kg, selenium at2.5 mg/kg, silver at 3.5 mg/kg, zinc at 1,400 mg/kg, a~etone at 160 ug/kg,
carbon disulfide at 9 ug/kg, methyl ethyl ketone at 76 ug/kg, cyclohexane at 39 ug/kg, benzene at 18 ug/kg,
methyl cyclohexane at 180 ug/kg, toluene at 290 ug/kg, tetrachloroethylene at 5 ug/kg, methyl isobutyl
ketone at 80 ug/kg, methyl butyl ketone at 270 ug/kg, chlorobenzene at 200 ug/kg, ethyl benzene at 300
ug/kg, total xylenes at 1,300 ug/kg, isopropyl benzene at 12 ug/kg, 1,3-dichlorobenzene at 170 ug/kg, 1,4-
dichlorobenzene at 290 ug/kg, 1,2-dichlorobenzene at 250 ug/kg, (3&/or4)methyl phenol at48,000 ug/kg,
naphthalene at 6,200 ug/kg, 4-chloroaniline at 980 ug/kg, 2-methyl naphthalene at 4,300 ug/kg, 1, 1-
biphenol at 3,500 ug/kg, dimethyl phthalate at 47,000 ug/kg, phenanthrene at 1800 ug/kg, benzyl butyl
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section 1
Draft
Revision Date: October 18, 200 I
Page10of18
Work Assignment No. 040-RICO-A44F
Sigmon 's Septic Tank Site
phthalate at 220,000 ug/kg, and bis(2-ethylhexyl)phthalate at I 00,000 ug/kg. Swnmaries of the organic
and inorganic analytical results for soil are presented in Table 1-1.
Volatile organic compounds (VOCs) and metals detected in groundwater concentrations include: barium
. I at 83 ug/1, cobalt at 1.2 ug/1, manganese at 260 ug/1, magnesium at 10,000 ug/1, total mercury at4.6 ug/1,
nickel at 4.2 ug/1, 1, 1 dichloroethane, cis-1,2-dichlorthene, 1,4-dichlorobenzene, dhlorobenzene at 72 ug/1, I
xylenes at 2 ug/1, 1,2-dichlorobenzene at 8 ug/1, benzene at 2 ug/1, and 1,3 dichlorobenzene at I ug/1.
Summaries of the VOC and metal analytical results for groundwater are pr~sented in Table 1-2.
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Inorganic constituents detected in the surface water samples include: arsenic at 18 ug/1, barium 210 ug/1, I
cadmium 1.2 ug/1, cobalt 14 ug/1, iron 7,000 ug/1, manganese l,300ug/l, nickel 11 ug/1, and zinc 220ug/l.
Summaries of the metal analytical results for surface water are presented in Table 1-3.
1.4 Baseline Risk Assessment Protocol
The BLRA as described in this Work Plan is based on U.S. EPA guidance including, but not limited to,
the following:
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EPA, 1988, Guidance for Conducting Remedial Investigations and Feasibility Studies Under
CERCLA, Interim Final, EPA 540-G-89-004. Office of Emergency aAd Remedial Response
(OERR), Washington, DC. October;
EPA, 1989a, Risk Assessment Guidance for Superfund (RAGS), Volume I, Human Health I
Evaluation Manual (Part A), Interim Final, Office of Emergency and Remedial Response,
Washington, DC, EP A/540/1-89/002.
EPA, I 991, Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation
Manual Supplemental Guidance, Standard Default Exposure Factors! Interim Final, Office
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of Solid Waste and Emergency Response, OSWER Directive: 9285.6-03.
Table 1·1
Analytical Results for ESI Soil Samples
Sigmon's Septic Tank Site
Sample Description ws SST-010-WS SST-011-WS SST-012-WS SST-013-WS SST-113-WS SST-014-SS SST-014-SB SST-017-SL SST-018-SL
Drainage ditch Drainage ditch
on Lauren Or., on Lauren Or., PRGs
Lagoon west of the east of the (Residential NC Soil
Contaminant Waste Pile Waste Pile sample Lagoon sample Lagoon sample Duplicate Background Background pond pond Values' Values EPA SSL!
lnorqanics Ima/km
Aluminum 31000 16000 48000 11000 25000 22000 11000 33000 30000 15000 1-NO 50
IAntimonv --42J --28J 25J 29J 0.49UJ 0.52UJ ----a->-NO 3.5
A.rsenic 32 3.8 2.2 2.4 --2 1.3U 3.2 2.7 3.4 a,;ig~ ND 10
Barium 230 310 140 310 1200 1400 17 18 85 160 <54(>-848 165
Cadmium 4.6J 3.9J 0.57J 3.8J 2.BJ 3.5J 0.07UJ 0.07UJ -----ND 1.6
Calcium 4100 6500 1700 9600 5600 9100 600U 640U --2700 NO NO ND
Chromium. total 75 60 40 68 120 140 7.9 19 21 31 ..o-27 0.4
Cobalt --------0.89UJ 1.SUJ 7.BJ 470-NO 20
Conner 200J 380J 64J 340J 260J 310J 3.4UJ 2.7UJ 10J 24J ago-NO 40
Iron 23000 17000 24000 9700 17000 17000 8200 29000 20000 19000 2300-NO 200
lead 180J 180J 64J 170J 210J" 250J 5.BJ 10J 13J 12J /"401 NI> 270 50
Maonesium 4100 2700 3800 1200 2800 3000 180 450 1300 4200 NO ND ND
Manqanese 290 180 · 220 160 220 240 37 47 240 180 ~o-NO 100
Mercury 0.26 0.56 -0.51 0.61 0.8 0.05U 0.06U ----.2e-Y ND 0.1
Nicker 74 61 20 33 310 350 2 4 8.2 17 ---ND 30
Potassium 3200 2200 3300 990 2400 2500 240 570 1100 4000 ND NO ND
Selenium ------2.5J 1.6J 2J 0.42UJ 0.44UJ ---39--ND 0.81
Silver 3.5 --3.2 0-28U 1.2U ---39-NO 2
Sodium 380 1200 760 1200 3100 4000 36U 38U --110 ND ND ND
Vanadium 49 41 56 · 27 36 36 20 69 46 45 --55---ND 2
Zinc 870 880 310 1400 930 1-100 7.4 11 36 100 = NO 50
Oraanics lua/kal
3 &/or 4) meth,,lnhenol 7200J 48000. 23000 23000 . 370U 50J ·---31000 ND NO
1, 1-biohenvl 1700J --2100J 2400J 3500J 370U 400U ---3500000 ND 60000
4-chloroaniline 14000J 3400J 89J 9400J 14000J 9800J 11U 130J ---24000 ND ND
1,2-dichlorobenzene --250 6J -11U 12U ----3700000 7000 ND
1,3-dichlorobenzene 7J 19 -76 170 11U 12U ·---1300 24000 ND
1,4-dichlorobenzene 24 120 44 10J 290 100 11U 12U -3400 1000 NO
2,4-dinitrotoluene -------370U 45J -720 NO ND
2-methvlnaohthalene 3600J 1900J 2200J 2700J 4300J 370U 400U ----ND 3000 NO
4-nitroohenol ·-920U 79J .. --49000 NO ND
cenaohthene -------370U 60J --130J 370000 8000 20000
cetone 21 67 43 160 130 11U 12U 160000 2810 NO
nthracene ---------370U 400U . 250J 2200000 995000 100
Benzenaldehvde ----3000J --370U 400U 440J 52J 610000 NO NO
Benzene --18 --14J 14J 11U 12U ----650 5.6 50
Benzofa)anthracene ----370U 400U -830 620 340 NO
Benzo a\nurene -----· ----370U 400U -730 62 88 100
Benzo b)fluoranthene -· -----370U 400U --960 620 1000 ND
Benzo :ghilanthracene --370UJ 400UJ ·-280J NO 6720000 ND
Benzo k)fluoranthene -----370U 400U 840 6200 12000 ND
Ben~ butvl ohthafate 220000 ----370U 400U -NO NO NO
- --.. - -----·---
----

-
------

-

-
-

-
-
Table 1-1
Analytical Results for ESI Soil Samples
Sigmon's Septic Tank Site
Sample Description WS SST-010-WS SST-011-WS SST-012-WS SST-013-WS SST-113-WS SST-014-SS SST-014-SB SST-017-Sl SST-018-Sl
Drainage ditch Drainage ditch
on Lauren Dr., on Lauren Or., PRGs
Lagoon west of the east of the (Residential NC Soil
Contaminant Waste Pile Waste Pile sample lagoon sample Lagoon sample Duplicate Background Background pond pond Values) Values EPA SSL
bis(2-ethvlhex.,,1nhthalate 240000 38000 920J 100000 97000 74000 370U 2700 ----35000 ND ND
Carbazole --------370U 400U --270J 24000 ND ND
Carbon disulfide SJ 4J 7J 4J BJ 9J 11 U 12U ----36000 4000 ND
Chlorobenzene 11J 9J 74 10J SOOOJ 200 11 U 12U ----15000 ND 50
Chrvsene --------370U 400U --920 62000 38000 ND
Cvclohexane ---39 -----11U 12U ---1400000 ND 100
Dibenzofuran --------370U 400U --6BJ 29000 4700 ND
Dimeth\ I ohthalate ------47000 370U 400U --460 100000000 ND 200000
Eth\ I benzene -41 300 --190 280 11U 12U ---2300000 240 50
Fluoranthene --------370U 400U --1600 230000 276000 100
Fluorene -

-
-----370U 400U --120J 260000 44000 ND
ldeno{ 1,2,3-cdinvrene -----370UJ 400UJ --320J 620 3000 ND
lsooron.,,lbenzene --12J -11J 16J · 11U 12U --ND 2000 ND
Methvl buM ketone -270 -----11U 12U --ND ND ND
Methvl ethvl ketone --34 --76 70 11U 12U ---730000 690 ND
Meth vi isobr ~I ketone -------80 " 11U 12U ----79000 ND ND
Methvlrvr1ohexane SJ 40 180 --26 38 11U 12U ' --260000 ND ND
Naohthalene 3700J 2500J -2000J 6200J 11000J 370U 400U ---5600 580 100
n-nitroso di-n-oron"lamine ------11U ?OJ ---69 ND 20000
Phenathrene 1800J -370U 400U -1200· ND 60000 100
Phenol -1'l.00-:5 370U 90J --3700000 ND 50
1-Nrene -370U 400U --1600 230000 286000 100
Stvrene --'1U 12U ,..._ -1700000 ND 100
Tetrachloroethvlene --SJ -----11\J 12U \-. ,-5700 7.4 10
oluene 17 63 210, 4J 7000J 290 11l.A 12U ~ -', 520000 7000 50
Xvlenes, total 200 1300 15J 730 200 11U '-12U --' --\ 210000 5000 50
ND = Not Determined
. ---Indicates that the oonstituent was not detected above the sample quantitation limit
Shadino -Exceeds PRG, NC soil value, or EPA SSL
Table 1-2
Analytical Results for ESI Groundwater Samples
Sigmon's Septic Tank Site
Sample Description SST-001-MW SST-002-PW SST-003-PW SST-103-PW SST-004-PW SST-005-PW SST-006-PW SST,Q07-PW SST-008-PW
Duplicate of I Region 9 North
On-site the PRGs Carolina
Monitoring Cascadden Cascadden Sheppard Lambreth/ John Davidson Background (Tap Water Federal 2L
Contaminant well Lees well welt well well Potts well Lambreth well well well Values) MCL Standards
lnorganics (ug/L)
Aluminum 8800 ------49U 3600 50 to 200• ND
A...,enic 4.2J --------------2.2UJ 0.045 50 50
Barium 620 16 380 380 83 31 32 -22 260 2000 2000
Calcium 210000 12000 22000 24000 13000 2700 4500 6200 2800 ND ND ND
Chromium 86 ------------0.70U 11 100 50
Cobalt 39 -2.6 2.4 1.2 -----a.sou 220 ND ND
Copper 26J --33J -------38J 30J 140 1300·· 1000
Iron 11000 -----------60U 1100 300" 300
lead 12 -4.4 3 --2 4.6 8.6 3.4 ND 15 .. 15
Magnesium 64000 --10000 10000 3800 ---1600 400U ND ND ND
Manganese 27000 21 260 260 100 15 7 -4.2 88 ND 50
Mercury 6,6J -1.3J 1.1J 4.6J ---0.10UJ 1.1 2 1.1
Nickel 73 --4.2 2.3 -------1.3U 73 ND 100
Potassium 11000J 1300J 4700J 4700J 2400J 1800J 1900J 1800J 1500J ND ND ND
Sodium 120000 3300 7800 8600 5000 2200 1600 5100 1400 ND ND ND
"'nc 44 110 31 28 200 820 560 1100 ND 2100
Organic (ug/LJ
1, 1 dichloroethane 3 0.6J 0.6J 0.8J ---1U 81 ND 700
1,2-dichlorobenzene • 8 ---1U 37 600 620
1,3-dichlorobenzene -1 ~· ----1U 0.55 600 620
1,4-dichlorobenzene 11 0.6J 0.6J 2 ----1U 0.5 75 75
Acetone 29J 5J -------SUR 61 ND 700
Benzerie 2 -0.4J ---1U 0.35 5 1
Chlorobenzene 72.• .. ------1U 11 ND 50
Chloroelhane 1 1U 4.6 ND ND
ds-1,2-dichloroethene 3 0.8J 0.8J 0.8J 1U 6.1 70 70
ylenes, total 2 0.5J 1U 140 10000 530
Notes:
ND = Not Determined
--Indicates that the constituent was not detected above the sample quantitation limit.
• = Secondary drinking water regulation
•• = Action level
ShadinQ = Exceeds PRG, MCL, or NC 2L Standards
- ---- - - --- - - ----
---- - ----------
Table 1-3
Analytical Results for ESI Surface Water Samples
Sigmon's Septic Tank Site
Sample Description SST-019-SW SST-020-SW SST-021-SW SST-022-SW SST-023-SW SST-024-SW
Davidson pond
Davidson pond surface water Surface water NC NC
suface water sample(at the attribution sample for Surface water sample Freshwater Freshwater
sample(at culvert discharge into the PPE#2 from an downstream of pond Upstream surface Standards Standards EPA
discharge into the intermittent steam). unnamed tributary in intermittent water sample on Surface water (Human (Aquatic Freshwater
Contaminant pond). PPE#1 PPE#1 (background) tributarv (attribution) unnamed tributarv sample from PPE#2 Health) Life\ SWSV
lnoraanic lua/U
Aluminum .. 1900 420U -.. .. ND ND 87
Arsenic 4.8J 3.6J 2.2UJ .. .. 18J ND so 190
Barium 210 120 3.6U 14 26 15 ND ND ND
Cadmium 1.2 -0.30U .. 1 .. ND 2 0.66
Calcium 8700 6300 2600U 4000 6000 4300 ND ND ND
Cobalt 14 4.8 0.60U .. ND ND ND
Iron 7000 3400 360U .. 740 .. ND 1000 1000
Lead 1.3 4.1 1.1U .. ND 25 1.32
Maanesium 2700 2000 1400 1200 2700 1500 ND ND ND
Manaanese 1300 770 9.4 11 130 35 ND ND ND
Nickel 11 4.3 1.3U .. .. . . ND 88 87.71
Potassium 20000J 16000J 4200J 1600J 4300J 2400J ND ND ND
Sodium 4400 1400 160U 4200 4900 4200 ND ND ND
Zinc 220 85 1.3U .. .. ND so 58.91
Oraanic (ua/Ll
Acetone I 13J .. BJ T I .. I .. ND ND ND
Toluene I .. 1U I I 0.4J I ND 11 175
--Indicates that the constituent was not detected above the sample quantitation limit.
ND= Not Determined
Shadina -Exceeds screenina value
I3asellne Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section I
Draft
Revision Date: October 18, 2001
Page 15 of 18
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
• EPA, 1992, Guidance for Data Usability in Risk Assessment (Part A), Final, PB92-963356.
•
Office of Emergency and Remedial Response, Washington, DC. April.
EPA, 1992a, Supplemental Guidance to RAGS: Calculating the Concentration Term, Office
of Solid Waste and Emergency Response, Washington, DC, Publication 9285.7-081.
• EPA, 1992b, Dermal Exposure Assessment: Principles and Applications, Interim Report,
Office of Research and Development, Washington, DC, EPA/600/8-91/0I IB, including
Supplemental Guidance dated August 18, 1992.
• EPA, 1992c, "Guidance on Risk Characterization for Risk Managers and Risk Assessors,"
Memorandum from F. Henry Habicht II, Deputy Administrator, to Assistant Administrators,
Regional Administrators, February 26, 1992.
•
•
•
•
•
EPA, 1995a, Supplemental Guidance to RAGS: Region 4 Bulletins Human Health Risk
Assessment, Waste Management Division, Atlanta, Georgia, November.
EPA, 1995b, EPA Risk Characterization Program. Memorandum from Carol M. Browner,
to Assistant Administrators, Associate Administrators, Regional Administrators, General Counsel,
Inspector General. March 21, 1995.
EPA, 1995c, Supplemental Guidance to RAGS: Region 4 Bulletins Ecological Risk
Assessment, Waste Management Division, Atlanta, Georgia, November, and amendments made
to this document by EPA Region 4 on August 11, 1999.
EPA, 1997a, Exposure Factors Handbook, Office ofResearch and Development, EP A/600/P-
95/002, August.
EPA, I 998, Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation
Manual, (Part D, Standardized Planning, Reporting, and Review ofSuperfund Risk Assessments)
(Interim).
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Baseline Risk Assessment Work Plan
EPA Conlract No. 68-W-99-043
Section I
Draft
Revision Date: October 18, 200 I
Page 16 of 18
Work Assignment No. 040-RICO-A44F
Sigma.n's Septic Tank Site
• EPA 2000b, Guidance for Data Quality Assessment (EPA QA/G-9), EP A/600/R-96/084.
Office of Research and Development, Washington, DC. July.
• EPA 2000c, Region 9 Preliminary Remediation Goals (PRGs) 2000, Annual Update, San
Francisco, California, November.
•
•
EPA, 2001 a, Region 3 Risk-Based Concentration (REC) Table, Philadelphia, Pennsylvania, May
8, 2001.
EPA, 2001b, Integrated Risk Information System (IRJS), On-line, National Center for
Environmental Assessment, Cincinnati, Ohio.
1.5 Organization of the Baseline Risk Assessment
As mentioned, the BLRA is composed of the BHHRA (human health risks) and the ERA ( ecological risks).
The BHHRA will present the human health assessment methods used, reLits generated, and the
interpretation of these results. The BHHRA will be organized as follows:
• Introduction: Provides a brief description of the site, site issues, history, regulatory framework,
and physical setting of the site. It also describes the protocol and o~ganization of the BHHRA.
I • Data Collection and Evaluation: Identifies data sources, evaluates data quality, and
identifies the chemicals present at the site that will be included in the risk lssessment process. lbis
step:
•
•
•
gathers and analyzes relevant data;
summarizes and tabulates the analytical data for each environmental medium;
presents the screening values that are used in the risk assessme~t to select chemicals of
potential concern (COPCs); I
presents the rationale for the selection of CO PCs (based on a comparison with screening
levels, background, etc.); and,
• identifies uncertainties associated with data evaluation;
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section I
Draft
Revision Date: October 18, 2001
Page 17ofl8
• Exposure Assessment: Identifies receptors and pathways, describes and calculates
exposure point concentrations (EPCs ), selects exposure assumptions, and presents methods for
calculating chemical intake rates.
• Toxicity Assessment: Involves the collection of quantitative and qualitative toxicity
information and a determination of the appropriate values to be used. The hierarchy for selecting
toxicological information for the BHHRA is used (i.e., IRIS, HEAST, NCEA).
• Risk Characterization: Describes quantitative methods for evaluating cancer risks and
noncancer hazards, and presents quantitative results and remedial goal options (RGOs ). It
summarizes data evaluation, exposure assessment, and toxicity assessment. The risk
characterization will identify and discuss contaminants and media of concern at the site. RGOs are
developed based on receptors and exposure routes.
• Uncertainty Analysis: Identifies uncertainties in all phases of the BHHRA and discusses their
individual effects on the risk assessment results and interpretation. An uncertainty analysis is
presented as a sub-section of each major section of the BHHRA ( e.g., data evaluation, exposure
assessment, etc.).
• Summary: Provides a brief summary of the entire risk assessment, including quantitative results,
uncertainties, and pertinent site information.
• Conclusions: Summarizes the results of the risk characterization, with a sufficient level of
elucidation addressing the effects that uncertainty may have on the results. Summary and discussion
are focused on those results and issues that are most likely to directly affect site management
decisions.
• References: Provides a complete list ofreference material used in preparation of the BHHRA.
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section I
Draft
Revision Date: October 18, 2001
Page 18 of 18
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
The ERA will present the methods used, results generated, and the interpretation of these results. The ERA
will be organized as follows:
• Site Description: Provides a description of the site with respect to ecological concerns such
as site use, acreage, vegetation, wildlife, habitats, and the likelihood oftlheatened and endangered
species being present.
•
•
•
Screening-Level Effects Evaluation: Identifies the sources of data and screening
benchmarks used, describes the methodology for determining chemiclls of potential ecological
concern (COPEC), identifies the COPEC, and describes uncertain1ties associated with the
screening-level effects evaluation.
Problem Formulation: Compares detected concentrations ofCOPEC to those encountered
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in background samples, spatially analyzes the distribution ofCOPEC, and evaluates impacted areas
with respect to exposure/risks to wildlife.
Conclusions: Briefly summarizes the results of the ERA and provides recommendations . I
Discussion is focused on those results and issues that are most likely to directly affect site
management decisions.
An overall risk assessment summary will overview the results of the BHHRA. This summary will focus on
presenting the "bottom-line" conclusions and issu~s that are most applicable to siie managementdecision-
making.
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RlCO-A44F
Sigmon's Septic Tank Site
Section 2
Draft
Revision Date: October 18, 2001
Page I of 29
2.0 Baseline Human Health Risk Assessment
2.1 Data Evaluation
Data used for the BHHRA will consist of the analytical results from the surface and subsurface soils, I
sediment, surface water, and groundwater samples collected during the PA/SI, ESI, and RI. A list of
chemicals present in site samples will be compiled as a first step of the data eJaluation. From this list,
CO PCs are selected to be carried forward into the exposure assessment (SectiJn 2.2). The processes of I evaluating the data quality (Section 2.1.1) and identifying COPC (Section 2.1.2) are described in the
following subsections.
2.1.1 Evaluating Data Quality
The analytical data may have qualifiers from the analytical laboratory QC or from the data validation
process that reflect the level of confidence in the data. Some of the more com~on qualifiers and their
meanings are (EPA, 1989a):
• U -Chemical was analyzed for but not detected; the associated value is the reporting limit.
• J -Value is estimated. \
• R -QC indicates that the data are unusable ( chemical may or may not be present).
I "J" qualified data will be used in the BHHRA; "R" qualified data will not. The handling of"U" qualified data
(nondetects) in the BHHRA is described in Section 2.2.5.1. The use of data Jith other less common
qualifiers will be evaluated on a case-by-case basis. Generally, data for which th~ identity of the chemical I
is unclear are not used in the BHHRA. If confidence is high that the chemical is present, but the actual
concentration is somewhat in question, the data generally will be used in th~ BHHRA.
If a blank contains detectable levels of common laboratory contaminants ( e.g., acetone, methyl ethyl
ketone, phthalate esters, etc.), then the sample results will be retained for further bonsideration only if the
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concentrations in the sample exceeds ten times the maximum amount detected in any blank. If a blank
contains detectable levels of uncommon laboratory contaminants, then the samplb results will be retained
for further consideration only if the concentrations in the sample exceed five time~ the maximum amount
detected in any blank.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Tentatively identified compounds (T!Cs) will be evaluated as follows.
Section 2
Draft
Revision Date: October 18, 200 I
Page 2 of29
When only a few TI Cs are present compared to the T AL and TCL chemicals, and no historical or other
site information indicates that either a particular TIC may indeed be present at the site ( e.g., because it may
be a by-product of a chemical operation conducted when the site was active) or that the estimated
concentration may be very high (i.e., the risk would be dominated by the TIC), then the TI Cs will not be
included in the risk assessment. The RPM will be consulted about omitting TI Cs from the quantitative risk
assessment and reasons for excluding TICs will be documented in the risk assessment report.
If many TI Cs are present relative to the T AL and TCL compounds identified, or if TIC concentrations
appear high or site information indicates that TI Cs are indeed present, then further evaluation ofTICs will
be necessary. If sufficient time is available, SAS will be used to confirm the identity and to positively and
reliably measure the concentrations of TI Cs prior to their use in the risk assessment. IfSAS methods to
identify and measure TI Cs are unavailable, or if there is insufficienttime to use SAS, then the TI Cs will be
included as chemicals of potential concern in the risk assessment and the uncertainty in both identity and
concentration will be noted.
2.1.2 Identification of COPCs
COPC identification is a screening process designed to focus the BHHRA on the chemicals that may
contribute significantly to overall risk. Only those analytes detected in at least one sample will be evaluated.
Chemicals for which all samples yield nondetects will be considered not to be present and, thus, will not
be evaluated. In this screening, chemical concentrations in environmental media will be compared to
chemical-and medium-specific risk-based screening concentrations derived from standard exposure
scenarios (Section 2.1.2.1) and compared to site background concentrations (for inorganics) (Section
2.1.2.2).
2. 1.2.1 Risk-Based Screening. The maximum detected concentration will be compared with the
appropriate risk-based screening concentration (RBSC). If the maximum detected concentration of a
chemical is less than or equal to its RBSC, the chemical in this medium will not be considered further in the
BHHRA because it is very unlikely that chemical concentrations at or below the RBS Cs would contribute
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section 2
Draft
Revision Date: October 18, 200 I
Page 3 of29
significantly to risk or hazard. If the maximum detected concentration exceeds the RBSC, the chemical will
be considered to be a COPC.
RBS Cs are derived from EPA Region 9 Preliminary Remediation Goals (PR Gs), which are based on
conservative, standard exposure assumptions (EPA, 2000). PRGs for noncan~er effects are calculated
using a hazard quotient (HQ) of 1.0 and for carcinogenic effects are calculated uslg an incremental lifetime
cancer risk (ILCR) of I E-6. Soil (and sediment) RBSCs are based on the "inteJted" residential soil PRG
I values and groundwater RBSCs are based on the household "tap water" PRG values. For cancer effects,
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the residential PRG values are used directly as RBSCs. Soil and groundwater RBSC values fornoncancer I
effects are derived by multiplying the integrated residential soil and tap water PRG values by a factorofO. l,
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respectively. This results in RBSC values associated with a hazard quotient (HQ) ofO. l, which is selected I ~de additional protection for simultaneous exposure to multiple chdmicals (EPA, 1995a).
For chemicals with both carcinogenic and noncancer PRG values, the more conselative (health-protective) I
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of the two values (the cancer-based RBC or the noncancer-based value calculated using an HQ ofO. l)
will be selected as the RBSC for the BHHRA.
Essential nutrients such as calcium, chloride, iodine, magnesium, phosphorus, potassium, and sodium may
be eliminated as CO PCs, provided that their presence in a particular medium iLudged to be unlikely to
cause adverse effects on human health (EPA, 1995a).
2.1.2.2 Background. Chemical concentrations of inorganic compounds will be compared to
background concentrations as an indication of whether a chemical is present frohi site-related activity or
as naturally-occurring background. In accordance with Region 4 guidance for b~ckground screening, the
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maximum detected concentration ofinorganic constituents will be compared with two times the average
background concentration. Chemicals with concentrations less than the bJckground value will be
eliminated from further consideration; however, if the maximum detected! concentration exceeds
background, the chemical will be retained as a COPC.
Background samples will be collected adjacent to and from upgradient monitoring well locations that are
distant to, and believed to be unaffected by, site operations and are not located J the groundwater plume
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section 2
Draft
Revision Date: October 18, 2001
Page4 of29
of some otheroff-site source of contamination. These samples will be sent to a laboratory and analyzed
for metals. Summary statistics will be provided in the BHHRA, and the analytical data for these
background samples will be appended.
2.1.3 Data Summary
The data evaluation will be presented for each medium in table format. These tables will include the
following information:
• Chemical name.
• Range of detected concentrations.
• Location of maximum concentration.
• Detection frequency.
• Range of detection limits.
• Concentration used for screening.
• Background value.
• Screening toxicity value.
• COPC flag.
• Rationale for contaminant selection or deletion.
2.2 Exposure Assessment
Exposure is the contact of a receptor with a chemical or physical agent. An exposure assessment estimates
the type and magnitude of potential exposure ofa receptor to CO PCs found at or migrating from a site
(EPA, 1989a). An exposure assessment includes the following steps:
• Characterize the physical setting.
• Identify the contaminant sources, release mechanisms, and migration pathways.
• Identify the potentially exposed receptors.
• Identify the potential exposure pathways.
• Estimate exposure concentrations.
• Estimate chemical intakes or contact rates.
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
2.2.1 Conceptual Site Model
Section 2
Draft
Revision Date: October 18, 2001
Page 5 of29
The conceptual site model (CSM) provides the basis for identifying and evaluating the potential risks to I
human health. The CSM (Figure 2-1) includes the receptors appropriate for all plausible land-use I
scenarios and potential exposure pathways. It graphically presents all possible pathways by which a
potential receptor may be exposed (including all source media, release and 1transport pathways, and
exposure routes), facilitates consistent and comprehensive evaluation of risk to Juman health, and helps to
I prevent potential pathways from being overlooked. The elements of a CSM include:
• Source.
•
•
•
•
Initially contaminated environmental medium.
Contaminant release mechanism .
Contaminant transport pathways.
Intermediate or transport media.
Exposure media
Receptors .
Routes of exposure .
The receptors and pathways in Figure 2-1 reflect plausible scenarios developed from information regarding
site background and history, topography, climate, and demographics.
2.2.2 Physical Setting
This section is based on the more-detailed account of the site description, history, and summary of previous
investigations provided in Section 1.0. Briefly, the site occupies approximate!~! 15.35 acres, including a
lagoon area of approximately 1.2 acres. The site contains three buildings: the home of Mary Sigmon, the
work location of Sigmon Environmental Services Inc. ( current name of the se~tic tank service), and a
storage shed (NCDENR, 2000). The east, west, and south boundaries of the site1are fenced and signs are
posted warning of the disposal area; however, access to the site is possible du~ to breaks in the fence.
The site is located in a rural area. To the southeast and south of the Sigmon propel, Mr. Chris Davidson
owns a relatively large parcel of property, which contains his residence, his businJss (a roofing company),
four rental houses, and a mobile home. John and Frances Lambreth own a tlome and pasture land
approximately 800 feet northwest of the lagoon area. The Steven Lambreth rental 1mobile home is located
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Primary
Source
Open Pits 1--►i
Former .
Lagoons .
Waste Piles I ~ .
---
Storage ... Tanks Area
Primary
Release
Mechanisms
. ..
• I Leaching • • I
Secondary
Source
I
Surface
Soil
• •
Subsurface
Soil
I Leaks I-
.
.
•
Secondary
Release
Mechanism
Surface
Runoff
. ' .. , Infiltration
-
•
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Figure 2-1
Conceptual Site Model
Sigmon's Septic Tank Site
Statesville. Iredell County, North Carolina
Pathways
. ..
. ' .. -.. ,Groundwater •
Tertiary
Release
Mechanism
.
•
Discharge/ ... Seepage
Pathways
-
• I Fish*
. '
• I Surface Water
-I Sediment** .. '
• Fish will be quantitatively evaluated if it is determined that site-related COPCS are in the Davidson or Sliwinski ponds.
•• Only sediment that is not covered by water will be quantitatively evaluated for human exposure.
• Exposure route will be qualitatively evaluated.
■ Exposure route will be quantitatively evaluated.
Bp:B.reR::t.as
~ lh:::idrt:al Irg"5tim ..
I:enml Cb1ta::t
Irg:stim
lh:::idrt:al Irg"5tim
I:enml Cb ii a t
lh:::idrt:al Irg"5tim
I:enml Cb rt a t
. _Irg:stim . . I:enml Cb1ta::t
I:rh3Jatim
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.... .... .... ....
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~ C: C: ~ := .. -" 0 ..
oS ~ 0 0 0 Cl) s: s: UICI I!!'? I!!'? G><O° ~ .. ' a, o~ -::,--::IT" =I'-::IT" ... C:
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I Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section 2
Draft
I Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tk Site
I
Revision Date: October 18, 200 I
Page 7 of29
I to the east of the Sigmon property on Eufola Road, at an approximate distance of 1,110 feet northeast of ~•""'t' I. I 2.2.3'-Contaminant Sources, Release Mechanisms, and Migration Pathways
Contam~ant 1sources, releases mechanisms, and migration pathways are presented in Figure 2-1.
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2.2.4 Rece1tors and Exposure Pathway Descriptions
I Receptors will be selected to represent the upper bound exposure to all plausibly exposed groups of people
at the Sigmon'k Septic Tank site. Receptors under current and future use idclude current onsite residents,
current adolesbent trespassers, current offsite residents, future workers, n!ture construction workers, and
future onsite rJsidents. The pathways by which receptors may be expose~ are summarized in Figure 2-1
and Table 2-1 \
I The BLRA will be based on a reasonable maximum exposure (RME) assumption. The intent of the RME
assumption is t6 estimate the highest exposure level that could reasonabl~ be expected to occur, but not
necessarily th~ worst possible case (EPA, 1989a, 1991 a). It is interpre/ed as reflecting the 90 to 95th
percentile on e1xposure. As a result, these estimates are not intended tt represent a broadly defined
population (EP~, 1989a). In keeping with EPA (1991 a) guidance, variables chosen for a baseline RME
scenario for codtact rate, exposure frequency (EF) and exposure duration ~D) are generally upper-bound
estimates. Othe~ variables [ e.g., bodyweight (BW)) and surface area (SA) ke generally central or average
values.
The averaging time (AT) for noncancer evaluation is computed as the product ofED (in years) times 365
days per year, t6 estimate an average daily dose over the entire exposute period (EPA, 1981 a). For
cancer evaluatidn, AT is computed as the product of70 years, the assumed Buman lifetime, times 365 days
I per year, to estimate an average daily dose prorated over a lifetime.
The exposure jriable values to be used for each receptor in the BLRA contaminant intake model are I
compiled in Table 2-2.
Scenario Medium Exposure Exposure
Timeframe Medium Point
Current/Future Soil Surface Soil Area 1 (Northern Portion of
Sile)
Area 2 (Southern Portion of
Site\
Surface Water Fish Davidson Pond
Sliwinski Pond
Surface Water Sigmon Pond
Davidson Pond
Sliwinski Pond
Groundwater Groundwater Private Wells
Private Well
- --- --
TABLE 2-1
SELECTION OF EXPOSURE PATHWAYS
SIGMON'S SEPTIC TANK SERVICE
STATESVILLE, IREDELL COUNTY, NORTH CAROLINA
Receptor Receptor Exposure Onsite/ Type of
Population Age Route Offsite Analysis
Ingestion Quant
Resident Adult Dennal Onsite Quant
Ingestion Quant
Child Dermal Onsite Quant
Ingestion Quant
Trespasser Adolescent Dermal Onsite Quant
Ingestion Quant
Trespasser Adolescent Dermal Onsite Quant
Adult Ingestion Offsile a~,
Resident Child Ingestion Offsite a~,
Adult Ingestion Offsite Qual
Resident Child Ingestion Offsite Quar
Ingestion Quant
Resident Adult Dermal Onsite Quant
Ingestion Quant
Child Dermal Onsite Quant
Ingestion Quant
Resident Adult Dermal Offsite Quant
Ingestion Quant
Child Dermal Offsite Quant
Ingestion Quant
Resident Adult Dermal Offsite Quant
Ingestion Quant
Child Dermal Offsite Quant
Ingestion Quant
Resident Adult Dermal Dffsite Quant
Inhalation Quant
Ingestion Quant
ChHd Dermal Offsite Quant
Inhalation Quant
Ingestion Quant
Resident Adult Dermal Onsite Quant
Inhalation Quant
Ingestion Quant
Child Dermal Onsite Quant
Inhalation Quant
-iililll == ==,
Rationale for Selection or Exdusion
of Exposure Pathway
Adult residents may be exposed to contaminants in surface soil while working onsile.
Child residents may be exposed to c.ontaminants in surface soil while playing onsite.
Trespassers may be exposed to contaminants in surface soil while trespassing onsile.
Transpassers may be exposed to contaminanls in surface soil while trespassing onsite.
Nearby adult residents may eat fish caught in Davidson Pond.
Nearby child residents may eat fish caught in Davidson Pond.
Nearby adult residents may eat fish caught in Sliwinski Pond.
Nearby child residents may eat fish caught in Sliv.inski Pond.
Onsite adult residents may be exposed to contaminants in the pond behind the Sigmon house.
Onsite child residents may be exposed to contaminants in the pond behind the Sigmon house.
Nearby adult residents may be exposed to contaminants in surface water in Davidson Pond.
Nearby child residents may be exposed to contaminants in surface waler in Davidson Pond.
Nearby adult residents may be exposed to contaminants in surface water in Sliwinski Pond.
Nearby child residenls may be 8xposed to contaminants in surface water in Sliwinski Pond.
Nearby adult residents may be exposed to site-related contaminants in groundwater.
Nearby child residents may be exposed to site-related contaminants in grounct.vater.
Onsite adult residents may be exposed to site-related contaminants in groundwater.
Qnsite chHd residents may be exposed to site-related contaminants in grounct.Yater.
--- -- -
------
_Scenario---Medium---Exposure Eipo=e
nmeframe Medium Point
Future Surface Soil Surface Soil Area 2 (Southern Portion of
Sile)
Subsurface Area 2 (Southern Portion of
So;I Site)
--= Ciiiiiil
TABLE 2-1
SELECTION OF EXPOSURE PATHWAYS
SIGMON'S SEPTIC TANK SERVICE
STATESVILLE, IREDELL COUNTY, NORTH CAROLINA
Receptor Receptor Exposure Onsite/ Type of
Population Age Route Offsite Analysis
Ingestion Quant
Worker Ad,H Oennal Onsite Quant
Ingestion Quant
Resident Adult Dermal Onsite Quant
lllQestion Quant
Child Dermal Onsite Quant
Ingestion Quant
Construction Worker Adult Dermal Onsile Quant
Ingestion Qual
Resident Adult Dermal Onsile Qual
Ingestion Qual
Child Dermal Onsile Qual
iiiii iiii --- - -
Rationale for Selection or Exclusion
of Exposure Pathway
Future workers may be exposed to contaminants in surface soil while working oosite.
Hypothetical future onsite adult residents may be exposed lo contaminants in surface soil during
landscaping or recreational activities.
Hypothetical future onsite child resioents may be exposed to contaminants in surface soil while
playing.
Future construction workers may be exposed to contaminants in subsurface (and surface) soil
wtine worki""-.
Hypothetical future onsite adult residents may be exposed to contaminants in subsurface son
brought to the surface.
Hypothetical future onsite child residents may be exposed to contaminants in subsurface soil
brought to the surface.
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Table 2-2
Section: 2
Draft
Revision Date: October 18, 200 I
Page 10 of29
Variables Used to Estimate Potential Chemical Intakes
and Contact Rates for Receptors
Sigmon's Septic Tank Site, Iredell County, North Carolina
Pathway Offsite Resident Adolescent Industrial On-Site Construction
Variable Trespasser Worker Resident Worker
Ingestion of Fish ,t:::::--./;J,~ \ o ✓ 10 j "1:S' 1t,io..~,\e.,
Ingestion rate of fish . l6.02J NA NA NA NA
(IR,) (kg/day)
EF (days/year) '350• NA NA NA NA
Ingestion of Soil
Soil ingestion rate NA 100' 50' 100-adult' 330'
(IR,) (mg/day) 200-child'
EF (days/year) NA 12° 2501 350" 250°
Dermal Contact with Soil ,.------..__ ' .,--,--__ -\/_
Body surface area NA ~ 2!300··;' 5 0 -a lt"·i s oo'o•·i
exposed to surface soil CJ l,900-cb~t '(_)
(SA,0) (cm2) \ K .....
Dermal absorption csv csv csv "-csv csv
fraction (ABS) (unitless)
EF (days/year) NA 12° 2501 350" 250'
Ingestion of Surface Water
IR,w (L/hr) 0.01 '·' 0.01 b,c NA 0.01'·' NA
Ef:._(days/yea~) ~4~ -1'2') NA ( 12° ":::> NA
ET(hours/day) (1~ U1 ') NA (ic') NA
' I ",,_,I ",,/ Dermal Contact with Surface vyat~, ,1 ,,.,-r-'\ ~ "\
SA,w (cm2) /6, 170:~ti~ b 850"·" NA 6, 1,70-a'auJ --, NA
3 900-ch ·• ·~ l3, 900-child" • I
' ' -
PC ( cm/hour) csv csv NA csv NA
ET (hour/event) (j~ ~ NA <f"1 C) NA
EF (days/year) 45° '
_.--1,2°_,,) NA <5¥) NA
Ingestion of Sediment -
Soil ingestion rate 100-adult' 1001 NA 100-adult'
(IR,) (mg/day) 200-child' 200-child' NA
Ei;-(daysJyear) ;::::> ~\ 12' NA 350" NA
Dermal Contact with Sediment "'' -------' .
Body surface area 5;000-~61:i~"" """'-2;420"·0 NA 5,0 ~~ --NA
exposed to surface soil /3,900-Q)!.~•-J 3,900.::C i · •d
(SA,0) (cm') \.
Dermal absorption csv csv NA csv NA
fraction (ABS) (unitless) ~ :::: ~"
EF (days/year) \~2' 12° NA 350•------, NA
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Baseline Risk Assessment Work Plan
EPA Contract No. 6
1
8-W-99-043
Section: 2
Draft
Revision Date: October 18, 2001
Page 11 of29
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tarik Site
Table 2-2
Variables Used to Estimate Potential Chemical Intakes
and Contact Rates for Receptors\
Sigmon's Septic Tank Site, Iredell County, North Carolina I
I Adolescent Industrial On-Site Construction Pathway Offsite Resident Variable Tresoasser Worker Resident Worker
Ingestion of\Groundwater * I
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IR,w (L/hr) I 2-adult' NA 1' 2-adult' NA
1-child1 1-child'
EF /davs/veah 350" NA 2501 350" NA
csv
NA
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Chemicll-specific value.
Not applicable.
, I Residents may also be exposed to contaminants in groundwater via dermal contact and InhalatIon of
voes while showering. The risk assessment will assume that chemicIal intake from these two
exposur~ routes is equal to the chemical intake from ingestion of grouhdwater.
U.S. En~ironmental Protection Agency (EPA), 1997, Exposure Facto~ Handbook, EPA/600/P-
95/002F]August. I
U.S. EPf-, 1989, Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation
Manual (Part A), Interim Final, Office of Emergency and Remedial Response, Washington, DC,
EPA/540/1-89/002. I .
Professiqnal judgment.
U.S. Environmental Protection Agency (EPA), 1995, Supplemental Guidance to RAGS: Region 4
Bu//etins,I Human Health Risk Assessment, Atlanta, GA, November. \ ·
Adult Resident was based on an average adult male's hands, forearms, feet, and lower legs (6,170
cm2). Ch
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ild Resident was based on the 50th percentile surface area ot'\the hands, arms, feet, and legs
of males age 3-6 (3,900 cm2).
U.S. EPA, 1991, Risk Assessment forSuperfund Volume I: Human Health Evaluation Manual
Supplem~ntal Guidance, Standard Default Exposure Factors, Interim ~
1
inal, Office of Solid Waste and
Emergenby Response, OSWER Directive: 9285.6-03.
Adolesceht Trespasser was based on the 50th percentile surface area of the hands and arms of males
age 7-16 1(2,420 cm'). \
Trespasser was based on the hands, feet, and legs (5,850 cm') of males aged 7-16.
I ' Worker was based on the 50th percentile surface area of an adult male's hands and forearms (2,300
cm2). It i~ expected that all other body parts will be covered while working and that there is minimal
contact wi,th sediment. \
Adult Resident and Construction Worker were assumed to be 25 percent of the 50th percentile total
body surfJce area of an adult male (5,000 cm2). This is the recommended value in EPA's Exposure
Factors H~ndbook for adults and outdoor soil. Child Resident was bas~d on the 50th percentile
I ' surface area of the hands, arms, feet, and legs of males age 3-6 (3,900 cm2).
U.S. EPA, Region 4, recommendation from Office of Technical ServiceJ, October 2001.
~,(fl
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_:.:,,-------... .,,,; , .. sG·"
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section 2
Draft
Revision Date: October 18, 200 I
Page 12 of29
2.2.4. 1 On-site Resident. The residential scenario is created to evaluate the upper-bound exposure
under the current and future land use scenario. Onsite residents may be exposed to contaminants in surface
soil while playing or working onsite. Onsite residents could also potentially be exposed to contaminants
in groundwater via ingestion and via dermal contact and inhalation while showering. Finally, onsite residents
may be exposed to contaminants in surface water that may collect in the "pond" located south of the
Sigmon house. Relevant pathways for exposure include incidental ingestion and dermal contact with
surface water; and incidental ingestion and dermal contact with dry sediment in the pond.
The residential scenario is evaluated using both an adult and child. Cancer risk is estimated as the sum of
the risks calculated for the adult and the child. The child is used for the noncancer evaluation.
It is assumed that the ED for a young child is 6 years (ages 1 through 6years), and for an adult is 24 years
(ages 7 through 30 years) (EPA, 1991a). Therefore, a resident's total ED is 30 years (EPA, 1991a). The
adult resident is assumed to weigh 70 kilograms (kg) and the young child is assumed to have an average
BW of 15 kg throughout the 6-year ED (EPA, 1995a). Both the adult and the young child are assumed
to spend 350 days per year ( days/year) at home (EF=350). It is assumed that residents may wade in the
pond, but that there will never be sufficient water in the pond for swimming.
2.2.4.2 Offsite Resident. Nearby residents may be exposed to contaminants in nearby surface water
bodies (i.e., Davidson pond, Sliwinski pond) during recreational activities such as fishing, wading, or
playing. Nearby residents may also be expose to contaminants in groundwater. Relevant pathways of
exposure include incidental ingestion and dermal contact with surface water; ingestion of fish; and ingestion,
dermal contact, and inhalation of groundwater.
2.2.4.3 Adolescent Trespasser. The adolescent trespasser is assumed to be a developing child,
ages 7 through 16 years, with an average BW of 45 kg throughout this I 0-year exposure period (ED= 10
years). This receptor may live near the site, but not on the site. The adolescent trespasser is assumed to
be exposed to contaminants in surface soil ( and dry sediment) via incidental ingestion and dermal contact.
Trespassers may also be exposed to contaminants in surface water via incidental ingestion and dermal
contact in the Sigmon, Davidson, or Sliwinski ponds during recreational activities. Once again, it is
assumed that adolescent trespassers exposure to surface water is limited to wading.
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Baseline Risk Assessment Work Plan Section 2
EPA Contract No. 68-W-99-043 Draft
Work Assignment No. 040-RICO-A44F Revision Dale: October 18, 2001
Sigmon's Septic Ta\1k Site Page 13 of29
I 2.2.4.4 Worker. The site may be re-developed for commercial/industrial use in the future. The future
worker is assJmed to be a 70 kg adult who spends 250 days peryearworLng at the site (EF=250 days)
for 25 years. 'fhe worker is assumed to be exposed to contaminants in surf1ce soil via incidental ingestion
~nd demrnl cdntact while working onsite. It is also assumed that a futtke worker may be exposed to
contaminants in groundwater in a private well. The worker is assumed to 6e exposed to groundwater via
ingestion.
2.2.4.5 Construction Worker. Future construction workers may be exposed to contaminants in
surface and su6surface soil while working onsite. Potential exposure rouies for the construction worker
will include idcidental ingestion and dermal contact with surface and 1subsurface soil.
I 2.2.5 Quantification of Exposure
The following\ basic equation will be used to calculate human intake of a COPC (EPA, 1989a):
DI= C x HIF Eq. 2.1
Where:
DI = Daily Intake (mg of chemical per kg of body weight per day).
C J
1
Concentration of the chemical in mg/kg or mg4 (ppm).
HIF =i Human Intake Factor (kg of medium per kg boly weight per day).
Each intake variable in the above equation has a range of values. The intake variable values for a given
pathway will be leiected so that the combination ofintake variables results iA an estimate of the reasonable
maximum expdsure that can be expected to occur (EPA, 1989) (see Tab!~ 2-2). This section describes
the method by Lhich the exposure concentrations and the human intrule factors will be derived.
I An example of how a HIF is derived is listed below:
HIF for l child resident ingesting soil = IR x EF x ED x CF/ BW x AT Eq. 2.2
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section 2
Draft
Revision Date: October 18, 200 I
Page 14 of29
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Where:
IR = Ingestion Rate of Soil mg/day 200
EF = Exposure Frequency days/year 350
ED = Exposure Duration years 6
CF = Conversion Factor kg/mg 10""
BW = Body Weight kg 15
AT-N = Averaging Time (Non-Cancer) days 2,190
In this case, the HIF is 1.3 E-05 kg/kg/day.
2.2.5.1 Exposure Point Concentrations. The concentration term used in the intake equations is
an upper bound estimate of the arithmetic average concentration for a chemical of potential concern based
on a validated set of site sampling results. Ideally the exposure point concentration should be the true
average concentration within an exposure unit. Due to the uncertainty associated with estimating the true
average concentration at a site, the 95 percent upper confidence limit (UCL) of the arithmetic mean will
be used for this variable (EPA, 1989). The following procedures will be implemented prior to calculating
the 95 percent UCL for each COPC:
•
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Duplicate samples will be averaged to reduce the bias introduced when more than one
sample was available from any one location. lfthe difference between the sample and its
duplicate is large, then the highest of the two samples will be used.
Constituent concentrations reported as non-detect will be assumed to be equal to one-half
the sample quantitation unit.
• Non-detects (samples with a "U'' qualifier) will be omitted from the analysis if one-half the
sample quantitation limit exceeds the maximum detected concentration for a given
chemical. The remedial project manager will be notified if this situation presents itself.
When the 95 percent UCL exceeds the maximum detected concentration, the maximum detected
concentration will be used as the exposure point concentration.
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Baseline Risk Assessment Work Plan Section 2
EPA Contract No. 618-W-99-043 Draft
Work Assignment No. 040-RICO-A44F Revision Date: October 18, 2001
Sigmon's Seplic TaAk Site Page 15 of29
In accordance tth Region 4 guidance, it will be asswned that the sampling data are lognonnally distributed;
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therefore, the following fonnula will be used to detennine the 95 percent UCL of the arithmetic mean of I the log-transfonned data (EPA, 1995a):
Eq. 2.3
I Where:
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s
Where:
X;
constant (natural log)
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-arithmetic mean of the log-transfonned data for contaminant I
[ statistic detennined by the standard deviation and slmple size .
[ sample size for contaminant in the particular mediJ set
-standard deviation of the Iog-transfonned data set
s = n(n-1)
= the log-transformed data for contaminant I
Eq. 2.4
EPA Region 4 makes an exception to the use of the UCL as the exposure point concentration for
groundwater. Grbundwater exposure point concentrations should be the ari
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thmetic average of the wells
in the highly con!entrated area of the plwne (EPA, 1995a). Therefore, expdsure point concentrations in
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groundwater wiB be the arithmetic average of the wells in the center of the plume.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section 2
Draft
Revision Date: October 18, 200 I
Page 16 of29
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
2.3 Toxicity Evaluation
Toxicity is defined as the ability of a chemical to induce adverse effects in biological systems. The purpose
of the toxicity assessment is two-fold:
•
•
Identify the cancer and noncancer effects that may arise from exposure of humans to the CO PCs
(hazard assessment).
Provide an estimate of the quantitative relationship between the magnitude and duration of exposure
and the probability or severity of adverse effects ( dose-response assessment).
The latter is accomplished by the derivation of cancer and noncancertoxicity values, as described in the
following sections.
2.3.1 Cancer Evaluation
Few chemicals are known to exhibit carcinogenic effects in humans, but numerous chemicals are suspected
to be human carcinogens. The evaluation of the potential carcinogenicity ofachemical includes both a
qualitative and a quantitative aspect (EPA, 1986). The qualitative aspect is a weight-of-evidence evaluation
of the likelihood that a chemical might induce cancer in humans. The EPA recognizes six weight-of-
evidence group classifications for carcinogenicity:
• Group A -Human Carcinogen: human data are sufficient to identify the chemical as a human
carcinogen.
•
•
•
•
Group BI -Probable Human Carcinogen: human data indicate that a causal association is
credible, but alternative explanations cannot be dismissed.
Group B2 -Probable Human Carcinogen: human data are insufficient to support a causal
association, but testing data in animals support a causal association.
Group C-Possible Human Carcinogen: human data are inadequate or lacking, but animal data
suggest a causal association, although the studies have deficiencies that limit interpretation.
Group D-Not Classifiable as to Human Carcinogenicity: human and animal data are lacking or
inadequate.
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section 2
Draft
' Work Assignment No. 040-RICO-A44F Revision Date: October 18, 2001
Sigmon 's Septic Tdnk Site Page 17 of 29
• GrouJ E-Evidence ofNoncarcinogenicityto Humans: human data are negative or lacking, and
adequ1ate animal data indicate no association with cancer.
The toxicity vllue for carcinogenicity, called a cancer slope factor (SF), is an estimate of potency. The
slope factor esiimates an upper-bound probability of an individual developJg cancer as a result of a lifetime
of exposure td a particular level of a potential carcinogen. Potency estimates are developed only for
chemicals in 6roups A, BI, 82 and C, and only if the data are sufficieJt. The potency estimates are
statistically deAved from the dose-response curve, using the best human o* animal study or studies of the
chemical. AltJough human data are often considered to be more reliable ihan animal data because there
is no need to eJtrapolate the results obtained in one species to another, m6st human studies have one or
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more of the following limitations:
• The djration of exposure is usually considerably less than lifetime.
• The coLentration or dose of chemical to which the humans were Lposed can be approximated
only crLdely, usually from historical data.
•
•
•
•
Conculent exposure to other chemicals frequently confounds interpretation.
Data relarding other factors ( e.g., tobacco, alcohol, illicit or mediclal drug use, nutritional factors
and dietlrry habits, heredity) are usually insufficient to eliminate corifounding or quantify its effect
on the ~esults. I .
Most epidemiologic studies are occupational investigations of workers, which may not accurately
I reflect the range of sensitivities of the general population.
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Most epidemiologic studies lack the statistical power (i.e., sample size) to detect a low, but
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chemical-related increased incidence of tumors.
Most potency Jtimates are derived from animal data, which present different limitations:
• It is necelsaryto extrapolate from results in animals to predict resull in humans; usually done by
estimatiJg an equivalent human dose from the animal dose.
• The rangi of sensitivities arising from genotypic and phenotypic diversity in the human population
is not reflected in the animal models ordinarily used in cancer studies.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section 2
Draft
Revision Date: October 18, 200 I
Page 18 of29
• Usually very high doses of chemical are used, which may alter normal biology, creating a
physiologically artificial state and introducing substantial uncertainty regarding the extrapolation to
the low-dose range expected with environmental exposure.
• Individual studies vary in quality ( e.g., duration of exposure, group size, scope of evaluation,
adequacy of control groups, appropriateness of dose range, absence of concurrent disease,
sufficient long-term survival to detect tumors with long induction or latency periods).
The SF is usually expressed as "extra risk" per unit dose; that is, the additional risk above background in
a population corrected for background incidence. It is calculated by the equation:
Eq. 2.5
where:
SF cancer slope factor (per mg/kg-day)
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P(ctJ = the probability of developing the types of cancer associated with the chemical at a I
dose of I mg/kg-day
P(oJ = the background probability of developing the types of cancer associated with the I
chemical at a dose of O mg/kg-day.
The SF is expressed as risk per mg/kg-day. In order to be appropriately conservative, the SF is usually
the 95 percent upper bound on the slope of the dose-response curve extrapolated from high ( experimental)
doses to the low-dose range expected in environmental exposure scenarios. EPA (1986) assumes that
there are no thresholds for carcinogenic expression; therefore, any exposure represents some quantifiable
risk.
The oral SF is usually derived directly from the experimental dose data, because oral dose is usually
expressed as milligrams per kilogram per day (mg/kg-day). When the test chemical was administered in
the diet or drinking water, oral dose first must be estimated from data for the concentration of the test
chemical in the food or water, food or water intake data, and BW data so that dose rates may be
expressed as mg/kg-day.
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Work Assignment No. 040-RICO-A44F Revision Date: October 18, 2001
Sigmon's Septic T.ink Site Page 19 of29
The EPA lntekated Risk Information System (IRIS) (EPA, 200 I b) expresses inhalation cancer potency
as a unit risk f~ctor (URF) based on concentration, or risk per microgram\of chemical/m3 of ambient air.
Because canclr risk characterization requires a potency expressed as ris~ per mg/kg-day, the URF must
be converted io the mathematical equivalent of an inhalation cancer SF, br risk per unit dose. Since the
inhalation uni/ risk is based on continuous lifetime exposure of an adult h~an (assumed to inhale 20 cubic
meters (m3) oi air/day and to weigh 70 kilograms) the mathematical conver~ion consists of multiplying the
unit risk (per n1crogram per cubic meter [µg/m3]) by 70 kilograms and by 1 looo microgram per milligram,
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and dividing the result by 20 cubic meters per day.
2.3.2 Eva/lation of Noncancer Effects
Many chemicJls, whether or not associated with carcinogenicity, are associated with noncarcinogenic
effects. The e1valuation of noncancer effects (EPA, 1989b) involves:
• QualitLve identification of the adverse effect(s) associated with the chemical; these may differ
•
•
•
depending on the duration ( e.g., acute or chronic) or route ( e.g., oral or inhalation) of exposure
ldentiJcation of the critical effect for each duration of exposure (t., the first adverse effect that
occurs 1as dose is increased)
Estim1on of the threshold dose for the critical effect for each duration of exposure
Develobment of an uncertainty factor; i.e., quantification ofthl uncertainty associated with
intersp~cies extrapolation, intraspecies variation in sensitivity, sevJrityofthe critical effect, slope
of the d6se-response curve, and deficiencies in the data base, in regard to developing a reference
I dose (ruD) for human exposure
• ldentifiiation of the target organ for the critical effect for each route of exposure.
These infonnatiln points are used to derive an exposure route-and duratioj_specific toxicity value called
an RID, expressld as mg/kg-day, which is considered to be the dose for hJmans, with uncertainty of an
order of magnitJde or greater, at which adverse effects are not expected to\occur. Mathematically, it is
estimated as the Jatio of the threshold dose (usually a no-observed-adverse-effect level in study animals)
. I ~ to the uncertamty ,actor.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
Section 2
Draft
Revision Date: October 18, 2001
Page 20 of29
IRIS (EPA, 200Ib) and the Health Effects Assessment Summary Tables (EPA, 1997d) express the
inhalation noncancer reference value as a reference concentration (RfC) in units of milligrams per cubic
meter (mg/m3). Because noncancerrisk characterization requires a reference value expressed as mg/kg-
day, the RfC must be converted to an inhalation RID. Since the inhalation RfC is based on continuous
exposure of an adult human ( assumed to inhale 20 cubic meters of air/day and to weigh 70 kilograms), the
mathematical conversion consists of multiplying the RfC (mg/m3) by 20 m3/day and dividing the result by
70 kilograms.
2.3.3 Dermal Toxicity Values
Dermal RfDs and SFs are derived from the corresponding oral values, provided there is no evidence to
suggest that dermal exposure induces exposure route-specific effects that are not appropriately modeled
by oral exposure data. In the derivation of a dermal RID, the oral RID is multiplied by the gastrointestinal
absorption factor (GAF), expressed as a decimal fraction. The resulting dermal RID, therefore, is based
on absorbed dose. The RID based on absorbed dose is the appropriate value with which to compare a
dermal dose, because dermal doses are expressed as absorbed rather than exposure doses. The dermal
SF is derived by dividing the oral SF by the GAF. The oral SF is divided, rather than multiplied, by the
GAF because SFs are expressed as reciprocal doses.
2.3.4 Target Organ Toxicity
As a matter of science policy, EPA (1989a) assumes dose-and effect-additivity for noncarcinogenic
effects. This assumption provides the justification for adding the HQs or hazard indices (HI) in the risk
characterization for noncancer effects resulting from exposure to multiple chemicals, pathways, or media.
However, EPA (1989a) acknowledges that adding all HQ or HI values may overestimate hazard, because
the assumption of additivity is probably appropriate only for those chemicals that exert their toxicity by the
same mechanism. HI and HQ values are described in Section 2.4.2 and are introduced here, because the
application of hazard additivity hinges upon the following discussion.
Mechanism of toxicity data sufficient for predicting additivity with a high level of confidence are available
for very few chemicals. In the absence of such data, EPA ( 1989a) assumes that chemicals that act on the
same target organ may do so by the same mechanism of toxicity, unless the data clearly indicate otherwise.
That is, the target organ serves as a surrogate for mechanism of toxicity. When the sum of HI values for
all media for a receptor exceeds I due to the contributions of several chemicals, it is appropriate to
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Work Assignment No. 040-RJCO-A44F Revision Date: October 18, 2001
Sigmon'sSepticTabkSite Page21 of29
segregate the jhemicals by route of exposure and mechanism of toxicity (i.e., target organ) and estimate I separate HI values for each target organ.
As a practical latter, since human environmental exposures are likely to involve near-or sub-threshold
doses, the targe1t organs chosen for a given chemical are the ones associated kth the critical effects. Target
organs are alsb selected on the basis of duration of exposure (i.e., the\target organs for chronic or
subchronic exbosure to low or moderate doses are selected rather than the target organs for acute
exposure to hi~h doses) and route of exposure. Because dermal RID valtes are derived from oral RID
I I values, the target organs for oral exposure are adopted as the target organs for dermal exposure. For some
chemicals, no ra\-get organ is identified. This occurs when no adverse effects! are observed or when adverse
effects such as )educed longevity or growth rate are not accompanied by rbcognized organ-or system-
specific functidnal or morphologic alteration.
2.3.5 SourcJs of Toxicity Information
Toxicity values are chosen for the BHHRA using the following hierarchy: . I
• EP A's on-line IRIS database (EPA, 200 I b) containing toxicity values that have undergone the
most rigbrous Agency review.
The lateJi version of the annual Health Effects Assessment Summary Tables, including all
supplemehts (EPA, 1997d) and other EPA documents, memoranda, frirmer Environmental Criteria
and Asse1ssment Office, National Center for Environmental Ass6ssment derivations for the
Superfunh Technical Support Center.
•
All toxicity valuJ, regardless of their source, will be evaluated for appropriateness for use in the BHHRA.
\ I
The most defensible GAF for each chemical is used to develop dermal toxicity values (EPA, 1995a).
When quantitativd data are insufficient to estimate a chemical-specific GAF, kegion 4 default values are
used. These are 6.8 for VOCs, 0.5 for semi volatile organics, and 0.2 for! inorganics.
Tables that list thJcancer and noncancertoxicity values, as well as other pertinent information, will be I I
provided in the BHHRA. Summarized toxicity profiles for the COCs will be appended.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
2.4 Risk Characterization
Section 2
Draft
Revision Date: October 18, 2001
Page 22 of29
Risk characterization is the process of applying numerical methods and professional judgment to determine
the potential for adverse human health effects to result from the presence of site-specific contaminants. This
is done by combining the intake rates estimated during the exposure assessment, with the appropriate
toxicity information identified during the toxicity assessment. Noncancer hazards and cancer risks are
characterized separately.
Quantitative expressions are calculated during risk characterization that describe the probability of
developing cancer (incremental lifetime cancer risks), or the nonprobabilistic comparison of estimated dose
with a reference dose for noncancer effects (hazard quotients and hazard indices). Quantitative estimates
are developed for individual chemicals, exposure pathways, exposure media, and source media for each
receptor. These quantitative risk characterization expressions, in combination with qualitative information,
are used to guide risk management decisions.
Generally, the risk characterization follows the methodology prescribed by EPA (1989a), as modified by
more recent information and guidance. EPA methods are appropriately designed to be health-protective,
and tend to overestimate rather than underestimate risk.
2.4. 1 Cancer Risk
The risk from exposure to potential chemical carcinogens is estimated as the probability of an individual
developing cancer over a lifetime, and is the ILCR. In the low-dose range, which would be expected for
most environmental exposures, cancer risk is estimated from the following linear equation (EPA, 1989a):
where:
ILCR = (I) (SF) Eq. 2.6
ILCR incremental lifetime cancer risk, a unitless expression of the probability of
developing cancer, adjusted for background incidence, calculated
= intake of chemical, averaged over 70 years (mg/kg-day)
SF cancer slope factor (per mg/kg-day).
The "I" term in Equation 2.6 is equivalent to the "DI" term (intake) in Equation 2_. l.
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Work Assignment No. 040-RICO-A44F Revision Date: October 18, 2001
Sigmon's Septic TaAk Site Page 23 of29
The use ofEqlation 2.6 assumes that chemical carcinogenesis does not exhibit a threshold, and that the
dose-response 1relationship is linear in the low dose range. Because this equlition could generate theoretical
cancer risks gr~ater than I for high dose levels, it is considered to be inacctlrate at cancer risks greater than
I E-2. In theJ cases, cancer risk is estimated by the one-hit model:
ILCR = 1 -e[!IJ/SFJ]
Eq. 2.7
where:
!LOR = incremental lifetime cancer risk, a unitless expression of the probability of
\ developing cancer, adjusted for background indidence, calculated
-e<TF) = the exponential of the negative of the risk calci'ated using Equation 2.9.
As a matter of policy, EPA (1986) considers the carcinogenic potency of simultaneous exposure to low
doses of carcino1genic chemicals to be additive, regardless of the chemical's hiechanisms of toxicity or sites
( organs of the liody) ofaction. Cancer risk arising from simultaneous exbosure by a given pathway to I
multiple chemicals is estimated from the following equation:
Risk p = ILCR (,h,m I)+ ILCR (,h,m 2) + ... ILCR (,h,m ;J Eq. 2.8
where:
RiskP = total pathway risk of cancer incidence, calculated
ILCR( chem;) = individual chemical cancer risk.
Cancer risk for \a given receptor across pathways and across media is summed in the same manner.
Lifetime cancer tsks in the range of I E-6 to I E-4 are generally regarded as Lceptable (EPA, 1990); risks
less than this rahge are regarded as negligible.
2.4.2 Noncalcer Hazards of Chemicals
The hazards assobiated with noncancer effects of chemicals are evaluated bylcomparing an exposure level
or intake with aA RID. The HQ, defined as the ratio of intake to RID, is estimated as (EPA, 1989a):
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
where:
HQ=! I RfD
HQ = hazard quotient (unitless, calculated)
Section 2
Draft
Revision Date: October I 8, 200 I
Page 24 of29
Eq. 2.9
I intake of chemical averaged over subchronic or chronic exposure period (mg/kg-day)
RID reference dose (mg/kg-day).
The I term in Equation 2.9 is equivalent to the "!" or "HIF" term (intake) in Equation 2.1.
· As shown above, both "I" and the RID are in units of mg/kg-day. The RID has been developed to
represent a dose rate unlikely to result in any adverse noncancer health effects, even to the most susceptible
members of the population. Therefore, if"!" is equal to or less than the RID (i.e., HQ:'.ol), adverse
noncancer health effects are unlikely. HQ values exceeding I do not indicate that noncancer hazard is likely
to occur, but rather that the occurrence of an adverse noncancer health effect can not be termed "unlikely."
The HQ does not define a particular risk level, nor can it be used to infer information regarding a dose-
response curve. That is, an HQ of0.01 does not imply a I in JOO chance ofan adverse effect, but
indicates that the estimated intake is I 00 times lower than the RID. This approach is different from the
probabilistic approach described in Section 2.4.1 to evaluate cancer risks.
In the case of simultaneous exposure of a receptor to several chemicals, an HI is calculated as the sum of
the HQs by:
where:
HI
I ' RID;
=
=
hazard index ( unitless, calculated)
intake for the ith toxicant
reference dose for the ith toxicant.
Eq. 2.10
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EPA Contract No. 68-W-99-043 Draft
Work Assignment No. 040-RICO-A44F Revision Date: October 18, 2001
Sigmon's Septic Tahk Site Page 25 of29
If an HI for a tven pathway exceeds I, individual HI values may be calculated for each target organ
associated with COPC in that pathway, as discussed in Section 2.3.4. Th~se are calculated as described
in the equatioh below:
HIOrgan =] Organ-I j RfDorgan-1 +] Organ-2 j RfDorgan-2 + ... ] Organ-; j RfDorgan-; Eq. 2.11
where:
Hl0 [gaa = hazard index (unitless, calculated) associate? with a given target organ
11 \ = intake for the i'h toxicant associated with a given target organ
R,o,g,n-; = reference dose for the ith toxicant affecting a given target organ.
2.4.3 Risk ~haracterization Results
Risk characterization results will be presented in tables and discussed in text. Results are presented
separately for chncer and adverse noncancer effects using the methods d~scribed in Sections 2.4.1 and
2.4.2, and discuksed for each receptor and environmental medium. Detailed spreadsheet calculations will
I be appended to the BHHRA.
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2.5 Remedial Goal Option Development
Region 4 requirds development of risk-based remedial goal options (RGOs) as part of the BHHRA (EPA,
1995a). RGOs hre site-specific risk-based concentrations that are backJalculated from the BHHRA
exposure and tokicity input assumptions at specified target risk or hazard l~vels. Therefore, risk-based
RGOs are sourJe medium-, receptor-, and chemical-specific.
2.5.1 Select1n of Chemicals of Concern
I The first step in RGO development is selection ofchemicals of concern (COC). Eitherofthe following two
conditions resuAs in designation of a COPC as a COC:
• The co1entration of the COPC exceeds its medium-specific applicable or relevant and . I . appropriate requirements.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Section 2
Draft
Revision Date: October 18, 200 I
Page 26 of29
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
• The COPC contributes significantly to unacceptable cancer risk (total site-related ILCR greater
than I x I 0-4) or hazard (total site-related HI greater than I).
Significant contribution to cancer risk is defined as contributing an ILCR across all exposure pathways for
a given source medium exceeding I x I 0-6; significant contribution to hazard is defined as contributing an
HI across all exposure pathways for a given source medium exceeding 0.1. The COC, therefore, may be
selected because of their cancer risk ( cancer COPC) or noncancer hazard (noncancer COPC). The RGO
estimation process for all the receptors, source media and exposure pathways is described in the following
section.
2.5.2 Remedial Goal Options Estimation Methodology
Cancer and noncancer RGOs are calculated for each medium in which COCs are identified. Medium-
specific RGOs are calculated for each receptor across all applicable exposure routes. RGOs for cancer
for a receptor and medium are calculated by the following equation (EPA, 1995a):
where:
RGO,0,
EPC,0,
TR
ILCRcoc
RGO coc = EPC coc TR
JLCRcoc
Eq. 2.12
= remedial goal option for a given COC, receptor and source medium, calculated
(mg/kg or µg/L)
exposure point concentration of the COC in the given medium (mg/kg or µg/L)
= target risk level (I x J0·6, I x 10·5, I x 10-4)
= total incremental lifetime cancer risk for the COC, for a given receptor added
across all exposure routes for a given source medium.
RGOs for noncancer COC are estimated as follows:
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Baseline Risk Asses,smcnt Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tailk Site
RGO
where:
= coc
EPC coc
ILCR
THI
coc
Section 2
Draft
Revision Date: October 18, 200 I
Page 27 of29
Eq. 2.13
RGO,0, = remedial goal option for a given COC, receptor and source medium, calculated (mg/kg or
Epc ~g/L) · · f h coc · th · I d. ( g/k IL) ,0, = exposure pomt concentration o t e m e given me 1urn m g or µg
THI = t~rget hazard index (0 .1, I, 3) \
Hico, = tbtal hazard index for the COC, for the receptor across all routes for given source medium.
The range ofRhos for each COC, for a given receptor and medium are bled on TR values of! O'°, 10-5,
I 104 and THI values of 0.1, I, and 3 (EPA, 1995a).
I 2.6 Uncertainty Analysis
The primary o~jective of the BHHRA is to characterize and quantify potential human health risks.
However, these hsks are estimated using incomplete and imperfect informatidn that introduces uncertainties
at various stagel of the risk assessment process. Uncertainties associate<l with earlier stages of the risk
assessment bedome magnified when they are concatenated with other hncertainties in the latter stages.
The chief goal Jthe uncertainty analysis is to evaluate uncertainties and ptsent them in context of their
potential impaction the interpretation of the BHHRA results and the types o~ environmental management
decisions that mly be based on these results. Although the BHHRA will include generic uncertainties that
are common to human health risk assessment protocols (e.g., additivi1 of health effects in the risk
characterization)l the uncertainty analysis will focus on those uncertainties that are peculiar to the Sigmon 's
Septic Tank sitJ and assumptions made in the BHHRA.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tank Site
2.6.1 Types of Uncertainty
Section 2
Draft
Revision Date; October 18, 2001
Page 28 of29
Uncertainties in risk assessment are categorized into two general types: I) variability inherent in the (true)
heterogeneity of the data set, measurement precision, and measurement accuracy; and 2) uncertainty that
arises from data gaps.
Estimates of the degree of variability tend to decrease as the sample size increases. This is because larger
data sets are less impacted by individual samples/measurements and typically allow for greater accuracy.
Uncertainty that arises from data gaps is addressed by applying models and assumptions. Models are
applied because they represent a level of understanding to address certain exposure parameters that are
impractical or impossible to measure ( e.g., COPC concentrations in shower room air). Assumptions
represent an educated estimate to address information that is not available ( e.g., surface water ingestion
rates, additivity of carcinogenic effects).
2.6.2 Sources of Uncertainty
A discussion will be provided to describe an overview of general sources of uncertainty and focus on those
most likely to affect the interpretation of the BHHRA results. These sources may include, but are not
limited to, the following:
•
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Representativeness of samples
Sampling methods
Background concentrations
Laboratory procedures
Land-use assumptions
Routes of exposure
Estimation of EPCs
Exposure assessment values
Toxicity values
Interactions of multiple contaminants .
The Sigmon's Septic Tank site BHHRA will identify and describe the unique set of uncertainties associated
with the site. Special attention will be given to those uncertainties that are thought to have the most
significant impact on interpretation of risk estimates and remediation decisions.
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EPA Contract No. 68-W-99-043 Drat1
Work Assignment No. 040-RICO-A44F Revision Date: October 18, 2001
Sigmon's Septic ra'nk Site Page 29 of29
EPA (1992c) Lidance urges risk assessors to address or provide descriptions ofindividual risk to include
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the "high end'[' portions and "central tendency (CT)" of the risk distribution. One way of fulfilling this . I
request, if either cancer or non cancer risk exceed generally acceptable limits ( cancer risk greater than 1 E-4
or target orgaispecific HI greater than 1 ), is to re-compute the !LC Rs or ~Is using CT values for as many
intake model tariables as possible. In contrast to the RME evaluation, which uses upper-end values for
intake or cont~ct rates, EF and ED, the CT evaluation chooses average1or mid-range values for these
variables (EPA, l 991 ). The intent is to provide perspective for risk man~gers. A CT will be included in
the uncertaint~ section of the risk characterization.
2.7 Huma\n Health Risk Conclusions
The BHHRA ill include a brief section that will summarize the results of the risk characterization, with a
sufficient level 1of elucidation addressing the effects that uncertainties may have on these results. The goal
is to present thJ BHHRA in a context that is most appropriate for the supp6rt of environmental decision-
making.
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Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RICO-A44F
Sigmon's Septic Tahk Site
3.0 References
Section 3
Draft
Revision Date: October 18, 2001
Page I of2
Black & Veatch, 200 I, Site Visit with U.S. Environmental Protection Agency and A TSDR, September
26, 2001.
NCDENR, 2000. North Carolina Department of Environment and Natural Resources, Expanded Site
Inspection Re~ort, Sigmon 's Septic Tank Service Site, NCD 062 555 792, Statesville, Iredell County,
North Caroli~a, March 31, 2000.
I NCDENR, 1998. North Carolina Department of Environment and Natural Resources, Combined
Preliminary Alsessment/Site Inspection Report, Sigmon 's Septic Tank Service Site, Statesville, Iredell
County, NortH Carolina, NCD 062 555 792, September 30, 1998.
United States Geological Survey (USGS), 1993, Troutman, North Carolina, 7.5-Minute USGS
Topographic f},uadrangle Map.
U.S. Envirojental Protection Agency (EPA), 2001a, Risk-Based Concentration Table, Region III,
Superfund Tedhnical Support Section, Philadelphia, Pennsylvania, A~ril 13.
U.S. Environmlntal Protection Agency (EPA), 200 I b, Integrated Risk llformation System (IRIS), On-,
line, National Center for Environmental Assessment, Cincinnati, Ohib.
U.S. EnvironmLtal Protection Agency (EPA), 2000, Region 9 PreliminJ Remediation Goals (PRGs),
Annual UpdatJ, San Francisco,. California, November.
U.S. Environm~ntal Protection Agency (EPA), 1997a, Exposure Facto'(/ Handbook, Final, National
Center for Environmental Assessment, Washington, DC, EP A/600/P-95/002Fa, August.
U.S. EnvironmLtal Protection Agency (EPA), 1997d, Health Effects AssLsment Summary Tables, FY
I 997 Update, Office of Solid Waste and Emergency Response, 9200.6h03 (97-1 ), EPA-540-R-97-
' 036, NTIS No. 1PB97-921199.
U.S. EnvironmLtal Protection Agency (EPA), 1995a, Supplemental Guidance to RAGS: Region 4
Bulletins Humah Health Risk Assessment, Waste Management Division, :.\tlanta, Georgia, November.
U.S. Environmltal Protection Agency(EPA), 1993, Superfund's StandJd Default Exposure Factors
for the Central 'rendency and Reasonable Maximum Exposure, Prelirriinary Review, Draft, May 5.
Baseline Risk Assessment Work Plan
EPA Contract No. 68-W-99-043
Work Assignment No. 040-RlCO-A44F
Sigmon's Septic Tank Site
Section 3
Draft
Revision Date: October 18, 2001
Page 2 of2
U.S. Environmental Protection Agency(EPA), I 992a,Supplemental Guidance to RAGS: Calculating
the Concentration Term, Office of Solid Waste and Emergency Response, Washington, DC, Publication
9285. 7-081.
U.S. Environmental Protection Agency (EPA), 1992b, Dermal Exposure Assessment: Principles and
Applications, Interim Report, Office of Research and Development, Washington, DC, EP N600/8-
91/0I IB, including supplemental guidance dated August 18.
U.S. Environmental Protection Agency (EPA), 1992c, "Guidance on Risk Characterization for Risk
Managers and Risk Assessors," Memorandum from F. Henry Habicht II, Deputy Administrator, to
Assistant Administrators, Regional Administrators, February 26.
U.S. Environmental Protection Agency (EPA), 1991, RiskAssessment Guidance for Superfund Volume
I: Human Health Evaluation Manual Supplemental Guidance, Standard Default Exposure Factors,
Interim Final, Office of Solid Waste and Emergency Response, OSWER Directive: 9285.6-03.
U.S. Environmental Protection Agency (EPA), 1990, "National Oil and Hazardous Substances Pollution
Contingency Plan," Federal Register 55(46): 8666-8865.
U.S. Environmental Protection Agency (EPA), 1989a, Risk Assessment Guidance for Superfund,
Volume I, Human Health Evaluation Manual (Part A), Interim Final, Office ofEmergency and Remedial
Response, Washington, DC, EP A/540/1-89/002.
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