NCD981927502_19910901_Geigy Chemical Corporation_FRBCERLA RI_Draft Remedial Investigation Study Book 1 of 2-OCR

MEMORANDUM
DATE: October 3, 1991
SUBJECT: Geigy NPL Site Draft RI Report
Aberdeen, NC
FROM: Giezelle S. Benn
Remedial Proje
TO: Geigy Review
Rutherford B. Hayes, Water
Steve Hall, ESD
Wade Knight, ESD
Chuck Pietrosewicz, ATS DR
Elmer Akin, Risk Assessment
Jack Butler, NC DEHNR
Attached is the draft Remedial Investigation Report for the ·
Geigy NPL Site in Aberdeen, NC. Please review this document
and provide any comments that you have to me no later than
October 24, 1991.
It is very important that we keep to this schedule. The
FS report is due in the Region on October 15, 1991.
project is targeted for a 2nd quarter ROD, March
Therefore, your support is greatly needed.
If you have any questions, please give me a call at x7791.
draft
-This
1992.
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
E~M-Southeast, inc.
DRAFT REPORT
REMEDIAL INVESTIGATION STUDY
Geigy Chemical corporation Site
Aberdeen, North Carolina
Book 1 of 2
Prepared for:
The Potentially Responsible Parties
for the
Geigy Chemical Corporation Site
Prepared by:
ERM-Southeast, Inc.
7300 Carmel Executive Park
Charlotte, NC 28226
September 25, 1991
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
SECTION
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical corporation Site
.Aberdeen, North Carolina
Table of contents
1.0 INTRODUCTION
1.1 Purpose of the Remedial Investigation
1.1.1 Characterization of the Site
1.1.2 Data Collection
1.2 Site Background
1.2.1 Site History/Waste Characterization
1.2.2 Site Description
1.2.3 Removal Actions
1.2.3.1 Initial Removal (Feb. and Oct. 1989)
1.2.3.2 March-April 1991 Removal
1.2.4 Previous Investigations
1.3 Report Organization
2.0 AREA FEATURES
2.1 Geographic Setting and Topography
2.2 Land Use and Economy
2.3 Regional Geology
2.3.1 Geology
2.3.2 Soils
2.4 Regional Hydrogeology
2.4.1 Ground Water
2.4.2 Well Inventory
2.4.3 Surface Water
2.4.3.1 Occurrence and Flow
2.4.3.2 Surface Water Usage
2.5 Demographics
2.6 Climate/ Air Quality
2.6.1 Climate
2.6.2 Air Quality
2.7 Ecological Habitats
2.7.1 Ecological Habitats
2.7.2 Environmentally Sensitive Areas and
Rare/Endangered Species
3.0 SITE HYDROGEOLOGIC INVESTIGATION
3.1 General Site Stratigraphy
3.2 Site Hydrogeologic Units
3.2.1 Uppermost Aquifer
3.2.2 Second Uppermost Aquifer
3.2.3 Third Uppermost Aquifer
3.3 Monitor Well Installation
i
1-1
1-1
1-2
1-2
1-5
1-5
1-5
1-6
1-6
1-7
1-7
1-8
2-1
2-1
2-1
2-1
2-1
2-2
2-3
2-3
2-5
2-5
2-5
2-5
2-6
2-6
2-6
2-6
2-7
2-7
2-7
3-1
3-2
3-3
3-3
3-6
3-9
3-11
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical corporation Site
Aberdeen, North Carolina
Table of contents
(continued)
SECTION
4.0
5.0
3.3.1 Drilling Methods
3.3.2 Well Construction
3.3.3 Well Development
3.3.4 Abandonment of Hollow Stem Augers
3.4 Physical Laboratory Tests
3.4.1 Grain Size Analysis
3.4.2 Permeability Tests
3.5 Aquifer Tests
3.6 Ground Water Sampling and Analysis
3.6.1 Sampling Procedures
3.6.1.1 Monitor Wells and On-Site Monitor
Supply Well
3.6.1.2 Sampling of Off-Site Wells
3.6.2 Phase 2, Step 1 Analytical Results
3.6.2.1 Field Parameters
3.6.2.2 TCL Volatiles
3.6.2.3 TCL Semi-Volatiles
3.6.2.4 Pesticides
3.6.2.5 TAL Metals
3.6.3 Phase 4, Step 2 Analytical Results
3.6.3.l Field Parameters
SOIL
4.1
4.2
4.3
3.6.3.2 TCL Volatiles
3.6.3.3 TCL Pesticides
INVESTIGATIONS
General
Soil Description
Soil sampling
4.3.1 Phase 1 Soil Sampling and Analysis
4.3.2 Phase 2 Soil Sampling and Analysis
4.3.3 Phase 3 Soil Sampling and Analysis
4.3.4 Phase 4 Samples -Additional Information
4.3.4.1 Off-Site Soil Boring
4.3.4.2 Semi-Volatile Samples
4.3.4.3 Horizontal Delineation of Contamination
DITCH
5.1
5.2
5.3
SEDIMENT INVESTIGATION
General
Ditch Sediment Description
Ditch Sediment Sampling
5.3.1 Phase 2 Ditch Sediment
5.3.2 Phase 3 Ditch Sediment
5.3.3 Phase 4 Ditch Sediment
ii
Samples
Samples
Samples
PAGE
3-11
3-11
3-12
3-12
3-12
3-12
3-13
3-13
3-14
3-14
3-15
3-15
3-16
3-17
3-17
3-17
3-17
3-18
3-18
3-18
3-19
3-'-19
4-1
4-1
4-1
4-1
4-1
4-2
4-3
4-4
4-5
4-5
4-5
5-1
5-1
5-1
5-1
5-1
5-2
5-2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical corporation site
Aberdeen, North Carolina
Table of Contents
(continued)
SECTION
6.0
7.0
NATURE AND EXTENT OF CONTAMINATION
6.1 Ground Water
6.1.1 Pesticides
6.1.2 TCL Volatiles
6.1.3 TCL Semi-Volatiles
6.1.4 TAL Metals
6.1.5 Field Parameters
6.2 Soils
6.3 Ditch Sediment Samples
6.4 Air
CONTAMINANT FATE AND TRANSPORT
7.1 Summary of Site Conditions
7.2 Potential Routes of Migration
7.2.1 Air Migration
7.2.1.1 Volatilization
7.2.1.2 Fugitive Dust
7.2.2 Soil Migration
7.2.2.1 Migration of Surface Soil
7.2.2.2 Migration through Vadose Zone
7.2.3 Ground Water Migration
7.2.3.1 Migration to Ground Water
7.2.3.2 Migration in Ground Water
7.3 Environmental Transformations
7.3.1 Biological
7.3.2 Chemical
7.3.2.1 Photolysis
7.3.2.2 Hydrolysis
7.4 Summary of Contaminant Fate
8.0 SUMMARY AND CONCLUSIONS
REFERENCES
iii
(
Soil
PAGE
6-1
6-1
6-1
6-3
6-4
6-4
6-4
6-5
6-5
6-5,
7-1
7-1
7-1
7-2
7-2
7-2
7-3
7-3
7-3
7-4
7-4
7-5
7-5
7-6
7-7
7-7
7-8
7-9
8-1
I
I
D
D
I Figure
1-1
I 1-2
1. 3
I 1-4
1-5
I 2-1
2-2
2-3
I 2-4
2-5
I 3-1
3-2
3-3
3-4
I 3-5
3-6
I 3-7
3-8
I 3-9
3-10
I
3-11
I 3-12
I 3-13
4-1
I 4-2
4-3
4-4
I 5-1
5-2
I
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical corporation Site
Aberdeen, North Carolina
LIST OF FIGURES
Site Location Map
Site Plan
Areas Designated for Removal -February and
October 1989
Soil Excavation Areas (March-April 1991)
Location of City of Aberdeen Municipal Supply
Wells, USGS Cluster Well and Private Wells in
the Vicinity of the Site
USGS Topographic Maps
Generalized Geologic Map of Moore County
Soil Survey of Area Near the Geigy Chemical
Corporation Site
Generalized Hydrogeologic Section
Location of Sand Hills Nature Preserve
Monitor Well Locations
Location of Hydrogeologic Profiles A-A' and B-B'
Hydrogeologic Cross Section A-A'
Hydrogeologic Cross Section B-B'
Ground Water Elevation Map -Uppermost
Aquifer
Elevation of Uppermost Confining Layer
Ground Water Elevation Map -Second
Uppermost Aquifer
Inferred Outcrop Area of Site -Second
Uppermost Aquifer
Phase 2, Step 1 Ground Water Investigation -
November 1990; Field Parameters
Phase 2, Step 1 Ground Water Investigation -
November 1990; Volatile and Semi-Volatile
Parameters
Phase 2, Step 1 Ground Water Investigation -
November 1990; Pesticides
Phase 4, Step 2 Ground Water Investigation -
July 1991; Field Parameters
Phase 4, Step 2 Ground Water Investigation -
July 1991; Volatiles and Pesticides
Phase 1 Soil Samples; Pesticide Analyses;
May 1990
Phase 2 Soil Sample Locations
Phase 2 Surface Soils, Pesticide Concentrations
Phase 4 Soil Sample Locations
Ditch Sediment Sample Locations
Ditch Sediment Sample Results
iv
I
I
I
I
0 Table
I 1-1
1-2
I 1-3
1-4
I 2-1
2-2
2-3
I 2-4
I 2-5
2-6
2-7
I 3-1
I 3-2
3-3
3-4
I 3-5
3-6
I 3-7
3-8
I 3-9
I 3-10
3-11
I
I
I
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical corporation Site
Aberdeen, North Carolina
LIST OF TABLES
Soils Removal, Surficial Volumes, February
and October 1989
Soil Volumes Removed, March-April 1991
Building and Soils Removal -Confirmation
Samples; March-April 1991
Detected Pesticide Constituents -Private
Well Ground Water Samples
Generalized Stratigraphic Units
Principal Soils Characteristics, Moore County
North Carolina Coastal Plain Geologic and
Hydrogeologic Units
1980 Census of Population and Housing in
Aberdeen and Moore County
Temperature and Precipitation
1989 Air Quality Data
Major Habitats and Associated Wildlife Found
in Moore County
Relationship of the Site Hydrogeologic Units with
Regional Hydrogeologic and Geologic Framework of the
North Carolina coastal Plain
Ground Water Elevation Data
Monitor Well Construction Details
Summary of Well Development
Site Aquifer Designation, Classification and Percent
Fine Material of Selected Soil Samples for Grain
size Analysis
Summary of Slug Test Results
Phase 2 Step .1 Ground Water Investigation -
Field Parameters
Phase 2 Step 1 Ground Water Investigation -
TCL Volatiles
Phase 2 Step 1 Ground Water Investigation -
TCL Semi-Volatiles
Phase 2 Step 1 Ground Water Investigation -
TCL Pesticides
Phase 2 Step 1 Ground Water Investigation -
TAL Metals
V
I
I
I
I
I
Table u 3-12
D 3-13
3-14
I 4-1
4-2
4-3
I 4-4
I 4-5
4-6
I 4-7
4-8
4-9
I 4-10
I 4-11
4-12
4-13
I 5-1
5-2
5-3
5-4
I 5-5
I 7-1
7-2
7-3
I 7-4
I
I
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical Corporation Site
Aberdeen, North Carolina
LIST OF TABLES
(continued)
Phase 4 Step 2 Ground Water Investigation -
Field Parameters
Phase 4 Step 2 Ground Water Investigation -
TCL Volatiles
Phase 4 Step 2 Ground Water Investigation -
TCL Pesticides
Phase 1 Soil Samples -TCL/TAL Parameters
Phase 2 Soil Samples -Site Specific Parameters
Phase 2 Background Soils; TCL Pesticides/
TAL Metals
Phase 2 Soils; Sample Locations Above
Significant Concentrations
Phase 3 Soil Samples Analyzed for TCL/TAL
Parameters
Phase 3 Soil Samples -Site Specific Parameters
Phase 3 Soil Samples -TCL/TAL Results
Cation Exchange Capacity and Total Organic
Carbon
Phase 3 Soil Samples; Pesticides Detected at
the Five Foot Sample Interval
Phase 3 Soil Samples; Pesticides Detected
at the Ten Foot Sample Interval
Off-Site Boring; Site Specific Parameters
Additional Surface Soil Samples
Phase 4 Soil Samples; Site Specific Parameters
Phase 2 Sediment Samples, Site Specific Parameters
Off-Site Sediment Samples, Site Specific Parameters
Phase 3 Sediment Samples, Site Specific Parameters
Phase 3 Sediment Samples, Total Pesticide
Concentrations
Phase 4 Sediment Depth Samples; Site-Specific
Parameters
Physical and Chemical Properties of Selected Pesticides
Site and Chemical Data for Pesticides
Estimated Retardation Factors for Pesticides in Ground
Water
Summary of Environmental Transformations
vi
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
g
n
g
1-A
3-A
3-B
3-C
3-D
3-E
3-F
3-G
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical Corporation Site
Aberdeen, North Carolina
LIST OF APPENDICES
TCL/TAL List
Exploratory Boring and Monitor Well Boring Drilling Logs
USGS Piezometer Well Cluster Information
Monitor Well Construction Diagrams
Quality Assurance Samples; Monitor Well Drilling and
Installation
Physical Laboratory Test Data Sheets
Slug Test Data
Ground Water Analytical Results Collected by EPA Region IV ESD·
From Private and Municipal Wells in the Aberdeen Area October
1989
vii
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
REMEDIAL INVESTIGATION
DRAFT REPORT
Geigy Chemical corporation site
Aberdeen, North Carolina
1.0 INTRODUCTION
The Geigy Chemical Corporation Site (the Site) is located just east
of the corporation city limits of Aberdeen, North Carolina on
Highway 211 in southeastern Moore County (Figure 1-1). The Site
was operated as a pesticide blending and formulation facility from
approximately 1947 to 1967. From 1968-1989, the Site was operated
by retail distributors of agricultural chemicals, mainly
fertilizers.
Three of the Potentially Responsible Parties (PRPs), Olin
Corporation, CIBA-GEIGY Corporation, and Kaiser Aluminum and
Chemical Corporation, agreed to conduct a Remedial Investigation
and Feasibility Study (RI/FS) for the Site. An Administrative
Order on Consent (AOC) covering the RI/FS was signed by the USEPA
Region IV Administrator and the PRPs in December 1988. An RI/FS
Work Plan (1) and a Project Operations Plan (POP) (2) were written
in accordance with the consent order and approved by the EPA.
Field work commenced at the Site during May 1990. The information
collected during the RI is presented in summary form in this
report.
1.1 Purpose of the Remedial Investigation
The purpose of the RI report is:
•
•
•
•
•
•
•
Describe the Site, its operating history and previous
investigations.
Describe the environmental setting of the Site and
surrounding areas.
Characterize the nature and extent of contamination
originating from the Site.
Collect data on hydrogeologic conditions at the Site,
including a description of the stratigraphy, lithology
and hydrogeologic units.
Present the results obtained from soil, ditch sediment
and ground water sampling events.
Delineate the potential contaminant migration pathways .
Describe the removal actions carried out during the term
of the RI/FS.
1-1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The Site description and history is provided in Section 1.2 and the
environmental setting is discussed in Section 2. A description of
the removal actions at the Site is provided in Section 1.2.3.
1.1.1 Characterization of the Site
One objective of this investigation was to determine the areal and
vertical extent of contaminant migration originating from the site.
Potential routes of off-Site migration of chemicals were identified
as follows:
• sediment transport in on-Site ditches
• ground water discharge to downgradient locations
• ground water discharge to lower aquifers
• airborne transport of soil/waste particulates to off-Site
locations
• on-Site soil erosion
Ground water, surface soils and ditch sediments are the principal
media for chemical migration. Therefore, field activities were
implemented to evaluate the presence and potential impact of such
migration.
1.1.2 Data Collection
The field investigation programs were designed and implemented to
provide additional information regarding both physical and chemical
characteristics of the Site. The activities conducted under the
field programs delineated in the RI/FS Work Plan are summarized as
follows:
Task 1 -RI/FS Work Plan Preparation
An RI/FS Work Plan was prepared prior to initiation of field
activities. The document detailed health and safety operations;
the number, location and method of soil and ground water sample
collection; well installation procedures; chemical analyses; and,
measures taken to ensure quality control. The document included a
Site specific health and safety plan, a quality assurance project
plan (QAPP) and a Site operations plan (SOP), as described in Tasks
3,4 and 5.
Task 2 -Site Reconnaissance
Site reconnaissances were conducted during August 1988 and January
1989 in order to assess the health and safety requirements for the
RI and to verify existing conditions. The August 1988
reconnaissance provided a preliminary assessment of migration
pathways based on Site features. Results of the reconnaissance
were presented in the RI/FS Work Plan (1). The January 1989 Site
1-2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
reconnaissance identified obvious areas of pesticide contaminated
surface soils near the warehouse loading doors and railroad dock.
These areas were subsequently removed (Reference Section 1.2.3.1).
Task 3 -Site-Specific Health and Safety Plan
A Site-specific Health and Safety Plan was developed for the RI and
approved by the EPA as Appendix A to the RI/FS Work Plan. The
purpose of the plan was to establish safety protection requirements
and procedures for field teams; ensure adequate health and safety
equipment and training for personnel during on-Site activities; and
to protect the general public and environment during the RI.
Tasks 4 and 5 -Quality Assurance Requirements
Site-specific quality assurance requirements for sampling programs
associated with the RI were developed in the QAPP (Appendix B of
the Work Plan) and the Field Sampling Plan (Appendix C of the Work
Plan). The plans address field sampling procedures, analytical
methods, and data evaluation.
Tasks 6 through 9 -Site Security, subcontractors, Community
Relations and Access Agreements
General procedures were identified regarding site security,
procurement of subcontractors, community relations and reporting
and, access to work areas.
Task 10 -Initial Soil Removal
Prior to conducting the field activities, an initial soil removal
operation was conducted. The removal is discussed in Section
1. 2. 3.
Task 11 -Subsurface Soils Investigations
The subsurface soils investigation was conducted in four phases.
In Phase 1, eleven surface soil samples were collected and analyzed
for the Target Compound/Target Analyte List (TCL/TAL) of parameters
(Reference Appendix 1-A). The purpose of the initial sampling was
to develop Site specific parameters for analysis during subsequent
phases.
Phase 2 soil samples were surface grabs collected on a forty foot
grid across the Site to delineate the areal extent of
contamination. The samples were analyzed for Site-specific
parameters as developed in Phase 1 and approved by EPA. Based on
the Phase 1 analytical results, pesticides were chosen as Site
specific parameters for sampling. In addition, copper and zinc,
which were added to fertilizers as micronutrients, were added to
the Site specific parameters. Lead, which was indicated as a
regional ground water concern, was also added to the list of Site
specific parameters to be analyzed at the Site.
1-3
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I·
I
I
I
I
Phase 3 of the soils investigation consisted of depth sampling
(i.e. , two, five and ten foc;>t depths) at the Phase 2 sample
locations that exhibited significant quantities of Site-specific
parameters. The purpose of the Phase 3 soil samples was to present
a vertical profile of potential contaminant migration.
Phase 4 samples included additional surface soil grabs to further
define the horizontal extent of contamination and to define the
boundaries of potential "hotspots".
The soils investigation is discussed in Section 4 of this report.
Task 12 -Ground Water Investigation
To evaluate the movement and quality of ground water in the
immediate vicinity of the Site, a ground water investigation (Phase
2, Step 1) was implemented. Prior to installation of monitoring
wells, an exploratory boring was installed on-Site to determine the
Site stratigraphy. The information from the exploratory boring was
used to refine the anticipated depths and screened intervals of the
monitor wells.
During Phase 2, Step 1 of the ground water investigation, ten
monitor wells were installed on-Site. The wells were installed at
various depths to assess the potential for vertical migration of
constituents. Six wells were installed in the uppermost aquifer
(MW-lS through MW-GS), three wells were installed in the second
uppermost aquifer (MW-lD, MW-4D and MW-GD) and one well was
installed in the third uppermost aquifer (PZ-1). The Phase 2, Step
1 ground water results indicated the presence of pesticides in the
uppermost aquifer. An additional ground water investigation (Phase
4, Step 2) was, therefore, implemented. Nine monitor wells (six
uppermost aquifer wells, and three second uppermost aquifer wells)
were installed at off-Site locations to assess the potential of
off-Site migration of constituents from the Site. In addition, the
Phase 4, Step 2 investigation included sampling of two upgradient
private wells to assess the origin of trichloroethene indicated in
on-Site wells MW-4D and MW-GD. Sampling of a USGS observation well
in proximity of the Site was also conducted. The ground water
investigation is discussed in Section 3 of this report.
Task 13 -Ditch Sediment Investigation
Samples of sediments from on-Site ditches were collected to provide
information on the transport of potentially contaminated sediments
to off-Site locations. Ditches are utilized to convey stormwater
from the Site and are normally dry during periods of no rainfall.
The ditch sediment investigation is discussed in Section 5.
Task 14 -Preparation of a Remedial Investigation Report
The RI Report presents a compilation of data collected during the
Site investigation. In addition, the report discusses the nature
and extent of contamination at the Site and the fate and transport
1-4
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
of contaminants. The data is presented in a manner to allow the
development of remedial alternatives as well as an assessment of
potential risks associated with the site.
1.2 site Background
1.2.1 Site History/Waste Characterization
The site has been leased and operated by various chemical companies
since about 1947. From approximately 1947 to 1967, the Site was
leased or rented by several companies for pesticide formulation and
retail sales. Since 1968, the site has been used by retail
distributors of agricultural chemicals, mainly fertilizers. The
most recent occupant, Lebanon Chemical Corporation, operated a farm
service center on the Site for retail distribution of agricultural
pesticides and fertilizers. The Site is currently unoccupied;
however, the Aberdeen and Rockfish Railroad which traverses the
southern portion of the site is still active.
Known operators at the Site and approximate dates of operation are
as follows:
• White & Peele (1947-1948)
• Blue Fertilizer (1948-1949)
• Geigy Chemical Corporation (now CIBA-GEIGY Corp.) (1949-
1955)
• Olin-Matheison Corporation (now Olin Corp.) (1956-1967)
• Columbia Nitrogen Corporation (1968)
• Kaiser Aluminum & Chemical Corporation (1969-1984)
• Lebanon Chemical Corporation (now Kaiser-Estech Corp)
(1985-1989)
Agricultural fertilizers, both liquid and dry, in bulk and bagged
form, have been distributed from the facility at various times
during the operating history. Micronutrients, such as copper and
zinc, were added to fertilizers in small quantities (i.e. 0.05% to
0.3%) to increase the quality and yield of crops. The pesticides
DDT, Toxaphene and BHC are known to have been formulated on-Site.
Technical grade DDT, toxa'phene and BHC were shipped in bags or
barrels to Aberdeen. The technical grade pesticide was blended
with clay or other inert materials to form a usable product and
repackaged for sale to local cotton and tobacco growing markets.
Pesticides were not manufactured at the Site, but rather only
formulated (i.e., blended) into a product suitable for local
consumer use.
1.2.2 Site Description
The Site is an approximately one-acre parcel located on the
Aberdeen · and Rockfish Railroad right-of-way, just east of the
corporation city limits of Aberdeen, on Highway 211 in southeastern
Moore County. The property is in the form of an elongated triangle
between Highway 211 and the railroad, with the highway and railroad
intersecting at the apex of the triangle. A Site location map is
1-5
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
provided as Figure 1-1.
The Site is currently vacant and consists of partial concrete
foundations from two former warehouses, an office building, and a
concrete tank pad as shown on the Site plan and topographic map
(Figure 1-2). The tank pad previously held four above ground
storage tanks with capacities of 8,500 to 10,000 gallons each. The
tanks, used to store liquid fertilizer solutions, were removed by
Lebanon Chemical Company upon vacating the site in 1989.
At the east end of the former warehouse buildings is an on-site
water supply well. The total depth of the well was sounded at 140
feet, however, records of the screened interval and other
construction details are not available. The well water was
probably used for process operations, lavoratories, showers and on-
Site drinking water.
No record of hook-up to municipal water or sewer systems has been
found. No septic tank or field drain could be located on Site.
The warehouse superstructures and some soils were removed during
March through April 1991 in a voluntary action undertaken by the
PRPs. The AOC was amended in February 1991 to include the removal.
The former warehouse buildings were constructed in various phases.
The first construction was initiated prior to 1950 and consisted of
the 60 square foot area on the eastern end of former Warehouse
Building A. Additional portions of former Warehouse Building A
were constructed westward, with former Warehouse Building B the
last constructed. The building superstructure was composed of
wooden columns and beams overlain by sheet metal to comprise the
walls and roof. There were various rolling doors which provided
truck and railroad dock access to the interior of the buildings.
The east end of former Warehouse Building A (including the original
structure) was believed to have been used primarily for the
formulation and packaging of pesticides. The remaining portions of
the former Warehouse were used primarily for the storage of
fertilizers and other agricultural chemicals.
1.2.3 Removal Actions
1.2.3.1 Initial Removal (February and October, 1989)
A Site reconnaissance, conducted during January 1989, identified
obvious areas of pesticide contaminated surface soils near the
warehouse loading doors and railroad dock. A two-phase soil
removal action, approved by EPA, was conducted at the Site to
remove the obvious areas of contaminated soils and debris. Two
reports documenting the February and October 1989 removals were
submitted to EPA (3). As shown in Figure 1-3, the areas designated
for removal were generally located near the access doors to the
warehouses. The initial removal was conducted in February 1989 by
GSX Services, Inc. Visually contaminated soils from areas A, B &
C were removed and sent to the GSX Landfill in Pinewood, SC for
1-6
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
disposal as hazardous waste. In addition, railroad ties removed
from the Area C spur track were disposed with the soils. (The
steel rails were stockpiled for future use by the railroad). Area
D was omitted from the removal action since removal from this area
was expected to result in erosion concerns. A total of 462 tons of
waste were _disposed.
Visually contaminated soils from Areas E, F, G and H were removed
during October 1989. Concentrated contaminated surface materials
were visually identified in each area, excavated and packaged in
six, JO-gallon fiberpack containers. This material was incinerated
at the ThermalKem facility in Rock Hill, SC. Other excavated
soils, a total of approximately 227 tons, were transported as
hazardous waste to the Laidlaw Environmental Services Landfill
(formerly GSX Services) in Pinewood, SC.
A summary of the volume of material removed from each area,
including the depth of excavation, is included in Table 1-1. After
the removal was conducted, the excavated areas were lined with a
permeable geotextile fabric and backfilled to grade with crushed
stone.
1.2.3.2 March-April 1991 Removal
In accordance with an amendment to the AOC, the warehouse
superstructures, pump house, and contaminated soils were removed
from the site during March through April 1991. The removal was
conducted in accordance with the procedures outlined in the
Warehouse Removal Work Plan (4) and the Work Plan for Soils Removal
Associated with the Warehouse and Railroad Spur (5), as approved by
the EPA. The excavated areas are shown on Figure 1-4. A summary
of the volume of material removed from each area, including the
depth of excavations, is included in Table 1-2. A report
documenting the removal activities (6) has been submitted to EPA.
The analytical results of the post-removal samples, indicating
existing Site conditions, are presented in Table 1-3.
1.2.4 Previous Investigations
An EPA site investigation was conducted at the Site in March 1988
by NUS Corporation (7). The objective of the Site investigation
was to collect soil and ground water samples from on-site and off-
Site locations to provide data necessary to document an EPA Hazard
Ranking System (HRS) evaluation.
The NUS investigation was conducted prior to any removal actions
that have taken place at the Site. In addition, the Site was
regraded by the railroad after the NUS investigation. Precise
sample locations were not provided in the NUS report and therefore,
the usefulness of the data was limited in subsequent
investigations. The soils analytical data collected during the
investigation no longer reflect existing site conditions.
1-7
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
None of the analyzed organic constituents including pesticides were
detected in the on-site water supply well. Isomers of BHC (i.e.,
alpha, beta, delta and gamma) were detected in five ground water
samples from off-Site sampling locations: two private wells and
three of the municipal wells. Lead was detected in concentrations
exceeding the published drinking water standards at that time in
two private wells (PW-01-Booth and PW-05-Bait and Tackle Store at
67 and 95 ug/1, respectively). Lead was not detected in the on-
Site ground water sample. Table 1-4 provides the analytical
results and Figure 1-5 shows the locations of the wells. Table 1-4
also includes analytical results of samples collected from the
private wells during 1989.
1.3 Report Organization
This report is organized in a manner similar to that suggested in
the document Guidance for Conducting Remedial Investigations and
Feasibility Studies under CERCLA (October 1988) . The major
sections are organized as follows:
Section 1 -
Section
Section
Section
Section
Section
Section
Section
Section
2 -
2.1 -
2.2
2.3
2.4
2.5
2.6
2.7
Introduction
Area Features
Geographic Setting and
Land Use and Economy
Regional Geology
Regional Hydrogeology
Demographics
Climate/Air Quality
Ecological Habitats
Topography
Section 3 -
Section 3.1
Section 3.2
Section 3.3
Section 3.4
Section 3.5
Section 3.6
Site Hydrogeologic Investigation
Section 4 -
Section 4.1
Section 4.2
Section 4.3
Section 5 -
Section 5.1
Section 5.2
Section 5.3
Section 6 -
Section 6.1
Section 6.2
Section 6.3
-General Stratigraphy/Lithology
-Hydrogeologic Units
-Monitoring Well Installation
-Physical Laboratory Tests
-Aquifer Tests
-Ground water Sampling and Analysis
Soil Investigations
-General
-Soil Description
-Soil Sampling
Ditch Sediment Investigation
-General
-Ditch Sediment Description
-Ditch Sediment Sampling
Nature and Extent of Contamination
-Ground Water
-Soils
-Ditch Sediments
1-8
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
g
section 6.4 -Air
Section 7 -Contaminant Fate and Transport
Section 8 -summary and Conclusions
1-9
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
2.0 AREA FEATURES
2.1 Geographic Setting and Topography
The Site is located in Moore county, North Carolina approximately
one-half mile east of the Town of Aberdeen. Aberdeen lies in the
Sand Hills physiographic province. The Sand Hills area is
characterized by rolling hills underlain by well drained,
unconsolidated sands. Many streams have cut deeply into the sandy
sediment. The overall slope of the Sand Hills area is to the south
and east and the average decrease in elevation is about 25 feet per
mile. A USGS topographic map of the Aberdeen area is presented in
Figure 2-1.
Sand Hills region ranges from about 270 feet mean
to more than 500 feet msl. The area around
in elevation from about 450 to 650 feet msl.
runs through the area at an elevation of
Elevation in the
sea level (msl)
Aberdeen ranges
Aberdeen Creek
approximately 325 feet msl.
2.2 Land Use and Economy
Moore County occupies a total area of 672 square miles and has an
estimated population of 59,013 people (1990 census).
Manufacturing and lumbering are the principal industries in Moore
County. Industrial plants in the area manufacture diverse products
such as textile mill products, furniture, fabricated metal products
and industrial machinery and equipment. The tourist trade is
important near Southern Pines, where golf courses and other
recreational facilities are maintained. These attractions and the
resulting service and entertainment industries have been largely
responsible for the area's emergence as a popular resort location.
Agriculture is also vital to the economy of the area.
Historically, agriculture has played a major roll in Moore County
economics, but has declined somewhat in recent years. Economic
statistics with respect to agriculture in the area are not
available for past years. The principal horticultural crops
currently grown in the area include peaches, apples and grapes.
The principal field and forage crops grown are watermelons, corn,
soybeans, sweet potatoes, tobacco, and coastal bermuda.
2.3 Regional Geology
2.3.1 Geology
The geology of the North Carolina Coastal Plain province has been
described by Schipf (8) and summarized by Winner and Coble (9) and
Giese and others (10). The geology of the North Carolina Coastal
Plain generally consists of unconsolidated sedimentary rocks which
were deposited on top of crystalline basement rocks. In general,
the Coastal Plain sediments dip and thicken toward the southeast.
The thickness of the sedimentary rocks in the Coastal Plain ranges
2-1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
from several feet at its western limit to more than 10,000 feet at
the North Carolina coastline. The thickness of the sedimentary
rocks in the Aberdeen area is approximately 200 to 250 feet.
The generalized stratigraphic units of the North Carolina Coastal
Plain are presented in Table 2-1. The rocks range from early
Cretaceous to Holocene in age. The stratigraphic units present in
Moore County, in ascending order above the basement rocks, are the
Cape Fear Formation, the Middendorf Formation and the Pinehurst
Formation.
The Cape Fear formation is late Cretaceous in age and unconformably
overlies the crystalline basement rocks. The cape Fear Formation
is generally composed of alternating beds of unconsolidated sand
and clay that typically range in thickness from three to fifteen
feet {Winner and Coble (9)). In Moore County, the Cape Fear
Formation outcrops only in the stream valleys in the eastern
portion of the county.
Overlying the Cape Fear is the Middendorf Formation, also of late
Cretaceous age. The Middendorf Formation is interpreted to be an
on-shore, non-marine facies of the Black Creek Formation which
exists in the Sand Hills area (Winner and Coble (9). The
Middendorf Formation is typically composed of a mixture of sands
and silty sands with interbedded layers of clay, silty clay and
gravel. Cross bedding, lenses, pinch outs and facies changes are
typical of the deposits of the Middendorf.
Unconformably overlying the Middendorf Formation and capping the
unit in the Sand Hills region is the Pinehurst Formation of
Tertiary Age. The Pinehurst Formation typically consists of poorly
sorted unconsolidated sands and gravel.
West of the.Coastal Plain province, the crystalline basement rocks
of .the Carolina Slate Belt outcrop in the Piedmont province. The
Piedmont rocks are comprised of metamorphic sandstones, mudstones,
and igneous rocks. In northern Moore County, the Piedmont rocks and
Coastal Plain sediments are separated by a northeast-trending
structural basin containing Triassic sediments. The structure,
known as the Deep River Triassic basin, is approximately ten miles
wide and is bounded on the east and the west by faults. The basin
deposits are poorly-sorted conglomerates, siltstones, and
claystones.
The major geologic units which outcrop in Moore county are
illustrated in Figure 2-2. The surface geology consists of Coastal
Plain sediments, crystalline rocks of the Piedmont province, and
Triassic basin rocks.
2.3.2 Soils
Soils within Moore County have been studied by the USDA Soil
Conservation Service (SCS), as part of the Moore county .soils study
which is still in progress. A generalized soils map of the area
2-2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
surrounding the Site is presented in Figure 2-3.
The Candor series soils occur at the Site and consist of deep,
somewhat excessively drained sandy soils. The principal
characteristics of the common soil types in the Aberdeen area are
summarized in Table 2-2.
2.4 Regional Hydrogeology
2.4.1 Ground Water
The Aberdeen area is underlain by three main regional aquifer
systems, which are termed, in ascending order above the crystalline
basement rocks, the Upper Cape Fear aquifer, the Black Creek
aquifer and the surficial aquifer. The North Carolina Coastal
Plain aquifer systems and their associated geologic units in North
Carolina are summarized in Table 2-3. A generalized hydrogeologic
cross section from the Sand Hills region to the North Carolina
coastline is depicted in Figure 2-4.
In the Coastal Plain aquifer system, ground water movement is
generally from upland areas toward stream valleys. Ground water
recharge occurs primarily by infiltration of rainfall in the
interstream areas. Vertical infiltration of recharge. water is
commonly restricted by the occurrence of clay layers which serve as
confining units. Ground water discharge is through seepage into
lakes, streams, and drainage ditches. Discharge also occurs by
evapotranspiration, upward leakage through confining beds to stream
valleys, and upward leakage to the bottom of estuaries.
Surficial Aquifer
The surficial aquifer of the Coastal Plain region of North Carolina
consists primarily of Quaternary age deposits which overlie
Cretaceous sediments. The age and lithology of the surficial
aquifer deposits vary across the coastal Plain area. In Moore
County, the surficial deposits are composed of sediments of the
Pinehurst Formation of Tertiary age. The Pinehurst Formation
generally is composed of poorly sorted fluvial material consisting
of coarse sand and gravel with silt and kaolinitic clay. The
percentage of sand in the aquifer in the Sand Hills area generally
is less than 70 percent (Winner and Coble, (9)).
The surficial aquifer is important to the Coastal Plain aquifer
system because it receives infiltration from rainfall and serves as
a source bed that moves downgradient into the deeper aquifers and
transmits water laterally to streams. The average thickness of the
surficial aquifer in the North Carolina Coastal Plain is 35 feet.
The average hydraulic conductivity is approximately 29 feet/day
(Winner and Coble, (9)).
2-3
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Black Creek Aquifer and Confining Unit
In the Sand Hills area, the Black Creek confining unit lies between
the surficial aquifer and the Black Creek aquifer. The Black Creek
confining unit is generally composed of clay, silty clay and sandy
clay. In the Sand Hills area, the Black Creek confining unit is
defined as the uppermost clay bed of the Middendorf Formation. The
average thickness of the Black Creek confining unit in the Sand
Hills area is 10 feet (Winner and Coble, (9)).
The Black Creek aquifer lies between the Black Creek confining unit
and the Upper Cape Fear confining unit. The Black Creek aquifer of
the Inner Coastal Plain consists mainly of late Cretaceous age
sediments of the Black Creek and Middendorf Formations. In the
Sand Hills area, the aquifer is composed of fluvial material
consisting of a mixture of fine-to medium-grained sand and silty
kaolinitic clay beds. The average percentage of sand in the
aquifer is 58 percent (Winner and Coble, (9)).
Recharge to the Black Creek aquifer occurs mainly in updip
interstream areas with discharge from the aquifer occurring to
streambeds and in downdip coastward areas. The average thickness
of the Black-Creek aquifer in the North Carolina Coastal Plain is
165 feet, with the thickness ranging from 22 to 409 feet. The
average estimate of hydraulic conductivity is 28 feet/day (Winner
and Coble, (9)).
Ground water from the Black Creek aquifer in the Sand Hills is
generally low in dissolved solids and hardness and is slightly
acidic. The Black Creek aquifer serves as the primary source of
potable ground water in the Aberdeen area.
Upper Cape Fear Aquifer and Confining Unit
The Upper Cape Fear confining unit, overlying the Upper Cape Fear
aquifer, consists of nearly continuous clay, silty clay and sandy
clay beds. In the Sand Hills area, the Upper Cape Fear confining
unit consists of the lowermost clay beds of the Middendorf
Formation. The average thickness of the Cape Fear confining unit
in the Coastal Plain of North Carolina is 48 feet. In the Aberdeen
area, the confining unit is approximately 60 feet in thickness
(Winner and Coble, (9)).
The Upper Cape Fear aquifer consists of beds of poorly sorted,
fine-to medium-grained sand in a clay matrix. The average
percentage of sand in the aquifer is 62 percent (Winner and Coble,
(9)). As with the Black Creek aquifer, recharge to the Upper Cape
Fear aquifer primarily occurs in updip interstream areas. Natural
discharge from the Upper Cape Fear aquifer occurs along and
directly into streams whose channels incise the unit. The average
thickness of the Upper Cape Fear aquifer in the North Carolina
Coastal Plain is 113 feet and ranges from 481 to 12 feet thick. In
the Aberdeen area, the Upper Cape Fear aquifer is only
2-4
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
approximately 10 to 20 feet in thickness and directly overlies the
crystalline bedrock (Winner and Coble (9)). Due to its limited
vertical extent, the Upper cape Fear aquifer is not a significant
source of drinking water in the Aberdeen area. The average
estimated hydraulic conductivity is 30 feet/day (Winner and Coble,
( 9) ) •
2.4.2 Well Inventory
Figure 1-5 shows the location of city of Aberdeen municipal wells,
and selected private wells within a 0.5 mile radius of the Geigy
Chemical Corporation Site. Ground water samples were collected in
1988 by the NUS corporation from municipal supply wells and private
wells in the Aberdeen area. The purpose of the sampling event was
to identify potential ground water contamination in the vicinity of
the Geigy Chemical Corporation site (NUS, (7)).
Solvents, pesticides, lead, copper, and zinc were detected in some
of the samples collected from private and municipal wells during
the NUS investigation in the Aberdeen area (NUS, (7)) Reference
Section 1. 2. 4.
2.4.3 Surface Water
2.4.3.1 Occurrence and Flow
Principal drainage within the Aberdeen area is provided by the
Little River and Drowning Creek (Figure 2-1). The divide between
these two drainages is a northwest-southeast trending ridge located
between Pinehurst and Southern Pines. Runoff to the north of the
divide is drained by Nicks Creek, Mill Creek, McDeeds Creek and
James Creek, which discharge to the Little River. South of the
divide, runoff discharges to Drowning Creek (Figure 2-1).
Surface runoff at the Site is generally to Aberdeen Creek which
flows into Drowning Creek, which flows southeastward and is part of
the Cape Fear River basin. North-south trending ridges formed by
a well developed, dendritic (i.e., branch-like) drainage pattern
project from the principal divide. Runoff is received by Deep
Creek, Horse Creek, Aberdeen Creek and Quewiffle Creek, which
discharge to Drowning Creek. Drowning Creek flows into the Lumber
River which flows southward and is part of the Pee Dee River Basin.
2.4.3,2 Surface Water Usage
An indication of surface water quality in Moore County was
determined from water records of community water supplies. Four
towns in Moore County obtain their community water supplies from
surface water sources. The communities include Carthage, Robbins,
Southern Pines, and Vass. Carthage obtains its water from Nicks
Creek during the summer months, and Twin Pond during the winter
months. Robbins obtains its water supply from Bear Creek.
Southern Pines receives their community water supply from Drowning
Creek, and Vass' supply is from the Little River.
2-5
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
2.5 Demographics
General demographic characteristics of the people living in the
Town of Aberdeen and in Moore County during the year 1980 are
summarized in Table 2-4. Information listed in the table includes
the number of people living in urban vs. rural areas, the median
age of people based on gender, median and mean family income in
1979, and occupations of employed people 16 years and older.
2.6 Climate/ Air Quality
2.6.1 Climate
Moore County is hot and generally humid in summer due to the moist,
maritime air. Winter is moderately cold but short since the
mountains to the west protect the area from many cold waves.
Precipitation is quite evenly distributed throughout the year and
is adequate for all indigenous crops. Table 2-5 provides data on
temperature and precipitation for the survey area as recorded at
Fayetteville and Pinehurst, North Carolina, in the period 1951 to
1973. Aberdeen is approximately 30 miles west of Fayetteville and
approximately five miles south of Pinehurst.
The total annual average precipitation is 43 inches at Fayetteville
and 46 inches at Pinehurst. Of this, 60 percent of the
precipitation usually falls in April through September, which
includes the growing season for most crops. The heaviest one-day
rainfall during the period of record was 5.12 inches at
Fayetteville on September 12, 1960, and 7.12 inches at Pinehurst on
October 15, 1954. Thunderstorms occur approximately 45 days each
year, and most are in summer. Tropical storms moving inland from
the Atlantic Ocean may occasionally cause extremely heavy rain for
one to three days.
The average seasonal snowfall is three inches at Fayetteville and
five inches at Pinehurst. The greatest snow depth at any one time
during the period of record was four inches at Fayetteville and
eight inches at Pinehurst. On an average of one day per year, at
least one inch of snow accumulates on the ground. The number of
such days varies greatly from year to year. Heavy snow may
occasionally cover the ground for a few days to a week.
The average relative humidity in midafternoon is about 60 percent.
Humidity is higher at night, and the average at dawn is about 85
percent. The sun shines 70 percent of the time possible in summer
and 60 percent in winter. The prevailing wind is from the
southwest. Average windspeed is highest, nine miles per hour, in
spring.
2.6.2 Air Quality
In 1989, the North Carolina Department of Environment, Health and
Natural Resources monitored four air quality parameters in
Fayetteville, located approximately 30 miles east of Aberdeen.
2-6
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
These parameters include total suspended particulates (TSP),
particulate matter -10 micrometer (PM-10), carbon monoxide (CO)
and ozone (03 ) •
Table 2-6 lists the values recorded during the year 1989 for TSP,
PM-10, co, and o 3 , as well as the National Primary Standards and
the North Carolina standards for these parameters. The National
and North Carolina maximum eight-hour standard of 9 ppm for carbon
monoxide was exceeded one time in 1989 with a recorded value of 9.8
ppm. All of the other parameters monitored in Fayetteville were
within national and state standards.
2.7 Ecological Habitats
2.7.1 Ecological Habitats
A wide variety of vegetation provides food, cover and protection
for the wildlife found in Moore County. The major habitats and
species of wildlife associated with these habitats are summarized
in Table 2-7.
Habitats which attract openland wildlife consist of cropland,
pasture, meadows and areas that are overgrown with grasses, herbs,
shrubs, and vines. These areas produce grain and seed crops,
grasses and legumes and wild herbaceous plants. Wildlife attracted
to openland habitats include quail, dove, fox and rabbit.
Habitats for woodland wildlife consist of deciduous and/or
coniferous plants and associated grasses, legumes, and wild
herbaceous plants. Wildlife associated with these areas include
woodpeckers, squirrel and fox.
Habitats for wetland wildlife consist of ponds, marshes and open
swampy shallow water areas. Wildlife found in such areas are duck,
muskrat, racoon and red-wing blackbirds.
2.7.2 Environmentally Sensitive Areas and Rare/Endangered Species
There are several environmentally sensitive areas containing rare
and/or endangered species in the vicinity of the Site in Aberdeen.
However, it is important to note that the Site has been in
industrial use since the 1950's. The area surrounding the one-acre
Site is zoned for commercial use.
The Sand Hills Natural Preserve is a State-owned natural area
located approximately three miles northeast of the Site (Reference
Figure 2-5) and the Paint Hill Area is a Priority Natural Area
located 1-1/4 miles north of the site. Both areas contain longleaf
pine forests and associated plant and animal communities.
Prior to 1893, the dominant tree type in the Coastal Plain was the
longleaf pine, which once covered an estimated 10 million acres of
eastern North Carolina. By the early 1900 's, turpentining and
logging operations had. destroyed the last virgin strands of long
2-7
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
leaf pine. Today, second and third-growth longleaf remain in small
isolated pockets of the state.
Many species of plants and animals co-evolved with longleaf
communities and grow nowhere else. The ecological community
depends on periodic fire to maintain their habitats and carry out
their life cycles. The red-cockaded woodpecker, an endangered
species, and the fox squirrel are two of many species of wildlife
to evolve specific adaptations to the fire-dependent longleaf pine
community. Two rare plant species, the Sand Hills Milkweed and the
Wells Tyxie Moss, grow in the Paint Hill Area. In addition, a
species of fish found in Aberdeen Creek, the Sand Hills chub, is
listed as a candidate for federal protection.
2-8
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
3.0 SITE HYDROGEOLOGIC INVESTIGATION
An initial ground water investigation (Phase 2, Step 1) was
conducted at the Site in accordance with the procedures outlined in
Task 12 of the approved RI/FS Work Plan. The purpose of the
initial ground water investigation was to determine the
stratigraphy beneath the Site and to characterize the movement and
quality of ground water in the immediate vicinity of the site. An
exploratory boring (EB-1) was also drilled at the Site prior to the
commencement of monitor well drilling activities. The purpose of
the exploratory boring was to assess the hydrogeologic units
beneath the Site in order to design the monitor wells based upon
Site-specific subsurface conditions. The initial ground water
investigation consisted of the drilling, installation, and sampling
of a total of ten ground water monitor wells at the Site.
During the Phase 2, Step 1 investigation, six monitor wells (MW-lS
through MW-6S) were screened in the uppermost aquifer beneath the
Site, three monitor wells (MW-1D, MW-4D and MW-6D) were screened in
the second uppermost aquifer and one monitor well (PZ-1) was
screened in the third uppermost aquifer. In addition, physical
laboratory tests were conducted on selected soil samples from the
monitor well borings; and, aquifer tests were performed at each
monitor well location. The locations of the exploratory boring and
the ten monitor wells installed at the Site are depicted in Figure
3-1.
As discussed in Section 3.6, sampling and analysis conducted in
accordance with the Phase 2, Step 1 investigation indicated the
presence of pesticides in the uppermost aquifer beneath the Site
and the presence of trichloroethene in two wells (i.e. MW-4D and
MW-6D) screened in the second uppermost aquifer. Based on these
results, an expanded ground water assessment program was
implemented to further characterize the hydrogeologic conditions
and contaminant distribution in the vicinity of the Site. The
objectives of the Phase 4, Step 2 investigation, as described in
the "Addendum to the RI/FS Work Plan" (12), were to characterize
the lateral extent of pesticides in the shallow aquifer, define
site ground water flow, and assess the lateral continuity of the
uppermost confining layer. As part of the expanded assessment, six
shallow monitoring wells (MW-7S, MW-BS, MW-9S, MW-lOS, MW-12S and
MW-13S) were located in off-Site areas downgradient of the existing
monitoring system. In addition, three wells (i.e., MW-11D, MW-14D
and MW-15D) were installed in the intermediate aquifer. The
locations of the Phase 4, step 2 wells are shown in Figure 3-1.
The following sections provide a description of the methods and
results of the initial ground water investigation conducted at the
site.
3-1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
3.1 General Site Stratigraphy
The stratigraphy beneath the Site was determined based upon
lithologic samples collected during the drilling of the exploratory
boring and monitor well borings. Detailed drilling logs for each
boring completed as part of the ground water investigation are
presented in Appendix 3-A.
The stratigraphy beneath the Site is depicted in two geologic cross
sections A-A' and B-B'. The locations of the cross sections are
presented in Figure 3-2 and the individual cross sections, A-A' and
B-B', are presented in Figures 3-3 and 3-4, respectively. Geologic
cross-section A-A' is an east to west trending profile extending
from the City of Aberdeen Municipal Supply Well #4 (MUW-04)
eastward to monitor well MW-15D. No detailed drilling logs are
available for MUW-04. The stratigraphy in the vicinity of
municipal well MUW-04 was, therefore, interpreted and correlated
with the strata beneath the Site based upon drilling and
geophysical logs from the United states Geologic Survey (USGS)
piezometer well cluster GS-02, which is located approximately 130
feet east of MUW-04 (see Figure 3-1). The USGS piezometers were
installed in 1990 as part of an on-going aquifer study being
conducted in the Aberdeen, NC area by the USEPA. Information
obtained from the USGS concerning well cluster GS-02, as well as
other USGS well clusters in the near vicinity of the Site, is
presented in Appendix 3-B. Geologic cross section B-B' is a
southwest to northeast trending profile extending from monitor well
MW-11D northeastward to monitor well MW-BS.
The stratigraphy beneath the Site generally consists of a series of
relatively permeable silty, clayey and gravelly sands separated by
relatively low permeability sandy and silty clay confining layers.
The maximum depth of strata which were drilled and sampled beneath
the Site is 185 feet (EB-1), corresponding to an approximate mean
sea level elevation of 295 feet. This elevation is equivalent to
the total depth elevation of Aberdeen municipal well MUW-04.
Three distinct permeable sand units and three distinct low
permeability clay confining layers were identified in the strata
encountered beneath the Site. Since each of the permeable sand
units apparently acts as a distinct hydrogeologic unit, each unit
and corresponding confining layer was given a name designation
based upon the depth within the stratigraphic profile. The sand
units were labelled, in order of descending depth, the uppermost
aquifer (referred to as the first aquifer), second uppermost
aquifer (second aquifer), and third uppermost aquifer (third
aquifer). Similarly, the confining layers were labelled, in order
of descending depth, the uppermost confining layer (first confining
layer), second uppermost confining layer (second confining layer)
and the third uppermost confining layer (third confining layer).
The strata beneath the Site to which each of these labels
corresponds is depicted in geologic cross-section A-A' and B-B'
(Figure 3-3 and Figure 3-4).
3-2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Based upon information in Winner and Coble ( 9) and the USGS'
preliminary interpretation of the strata at well cluster GS-02
(Coble (13)), each of the hydrogeologic units encountered beneath
the Site was correlated with a specific hydrogeologic unit and
geologic formation present in the Coastal Plain region of North
Carolina. The correlation of the units beneath the Site with the
regional geologic and hydrogeologic framework of the North Carolina
Coastal Plain is presented in Table 3-1.
The uppermost aquifer at the Site is interpreted to be part of the
undifferentiated surficial sands, which comprise the surficial
aquifer in the Coastal Plain of North Carolina. These surficial
sands are generally considered to be Tertiary-age deposits in the
Sand Hills region. As indicated in Table 3-1,. the base of the
uppermost aquifer may also include the uppermost sediments of the
Middendorf Formation of Cretaceous age. The surficial sands of the
Sand Hills region are generally difficult to distinguish from the
Middendorf sands due to their similar character (Coble(13)).
All of the strata encountered at the Site below the surficial sands
are interpreted to be Cretaceous-aged sediments of the Middendorf
Formation. Winner and Coble (9) define the Black Creek confining
unit as the first clay bed near the top of the Middendorf
Formation. Therefore, the uppermost confining layer at the Site is
interpreted to be the Black Creek confining unit. In the Sand
Hills region of North Carolina, the Black Creek aquifer lies
between the Black Creek confining unit and the Upper Cape Fear
confining unit. The second aquifer, second confining layer and
third aquifer present at the Site are all interpreted to be part of
the Black Creek aquifer. The deepest sediments encountered beneath
the Site, designated the third confining layer, are interpreted to
be the upper portion of the Upper Cape Fear confining unit.
A detailed description of each of the aquifers encountered beneath
the Site and their corresponding underlying confining layers is
presented in the following sections.
3.2 Site Hydrogeologic Units
3.2.1 Uppermost Aquifer
The uppermost aquifer at the Site extends from the ground surface
to the top of the first confining layer (see Figure 3-3). The
uppermost aquifer is approximately 63 feet thick at the eastern end
of the Site and thins with the topographic slope to a thickness of
approximately 40 feet near the western end of the Site.
The uppermost aquifer is primarily composed of loose to medium
compact, mottled, multi-color (primarily tan, pink, white, brown,
rust and purple) silty and clayey sands. Based upon visual
observation of soil cores, the total silt and clay content in this
unit ranges from 10% to 40%. The sand is generally poorly sorted,
fine to coarse-grained and subangular to subrounded in shape. Thin
clay layers (up to 1/2" in thickness), pebbles, and layers up to
3-3
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
two inches thick of hematite-cemented sandstone occur locally
throughout the uppermost aquifer.
A shallow, relatively thin, slightly sandy clay layer is present in
the uppermost aquifer extending from the middle portion of the Site
westward toward well MW-3S. This thin clay layer is three to five
feet thick and was encountered at a depth of approximately 15 feet
below ground level at MW-2S, MW-3S, well pair MW-GS and MW-6D, and
PZ-1.
A thin sandy clay layer was also noted in the uppermost aquifer in
the far eastern portion of the Site at well pair MW-lS and MW-1D
and EB-1. This clay layer is approximately two to three feet thick
and is present at a depth of approximately 42 to 45 feet below
ground level.
Sands with relatively little or no silt or clay content were noted
at the base of the uppermost aquifer at monitor well locations MW-
lS, 2S and GS. These relatively coarser sands are approximately
five to seven feet thick.
Ground water within the uppermost aquifer occurs under water table
or unconfined conditions. Saturated soils in the first aquifer
were encountered at approximate depths of 45 feet (MW-lS) to 35
feet (MW-3S and MW-4S) below ground level beneath the Site.
Ground water elevation data collected from the site monitor wells
from the period October 1990 to February 1991 (Phase 1, Step 2
Investigation) and from the period July 1991 to August 1991 (Phase
4, Step 2 investigation) are presented in Table 3-2. It should be
noted that monitor wells MW-lS through MW-13S are all screened in
the uppermost aquifer at the Site. A ground water elevation map
for the uppermost aquifer, constructed from water level
measurements obtained July 8, 1991 is presented in Figure 3-5. The
ground water elevation contour map was constructed based upon the
fundamental hydrogeologic premise. that the water level contour
pattern of shallow unconfined ground water flow in small drainage
basins is a subtle replica of the topography (Toth (14), Toth (15);
NRCD {11)).
' As illustrated in Figure 3-5, ground water flow in the uppermost
aquifer appears to be controlled by the presence of recharge areas
located at the eastern and western·ends of the site, and by the
presence of moderate topographic slopes on the northern and
southern sides of the site. Potentiometric data from the shallow
monitor wells indicate that ground water flow from the eastern and
western portions of the site meet in an elongated zone of
convergence which bisects the site. The axis of the convergence
zone approximately follows a line extending through monitor wells
MW-BS, PZ-1, and MW-12S, and to the southwest along the center of
a small drainage basin. This convergence zone is in turn bisected
by a hydraulic divide which occurs in the vicinity of monitor well
MW-12S.
3-4
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
For the area east of the convergence zone, ground water in the
uppermost aquifer predominantly flows to the west and northwest and
is believed to receive recharge in the relatively flat lying area
which lies between Highway 211 to the north, the Aberdeen and
Rockfish Railroad JJine to the south, and a dirt gravel road to the
west. The eastern :limit of this local recharge area is beyond the
area of this investigation and has not been specifically located.
The hydraulic gradi'ent in the uppermost aquifer across the eastern
portion of the sit~, as measured between monitor wells MW-4S and
MW-6S, is 0.026 ft/ft (2.6%). Similarly, for the area west of the
convergence zone, I ground water in the · uppermost aquifer
predominantly flows to the east-southeast and is believed to
receive recharge inlthe flat lying area located near city well MUW-
04. The hydraulic gradient in the uppermost aquifer across the
western portion of the site, as measured along a line trending from
USGS well cluster 1GS-02 to MW-3S, is 0.017 ft/ft (1.7%). The
hydraulic gradient \within the convergence zone, as measured from
monitor well MW-12S northward to MW-BS for the August 1991 gauging
event is calculated to be 0.0076 ft/ft (0.76%). The July 1991
gauging data was no~ utilized to calculate the hydraulic gradient
within the convegence zone due to the fact that an accurate water
level measurement c'ould not be obtained at MW-BS with a depth to
water electrode appkrently due to the low specific conductance of
the ground water atlthis location.
As ground water flo~ approaches the convergence zone, the hydraulic
gradient exhibited ~y the uppermost aquifer substantially decreases
and the direction of ground water flow from the eastern and western
portions of the site is re-directed to either the north or to the
southwest. The dir~ction in which ground water flow is re-directed
is dependent on the[location of a given flow path with respect to
the hydraulic divide which transects the convergence zone.
Accordingly, for th~ area north of a line extending through USGS
well cluster GS'-02 [ and wells MW-13S, MW-12S and MW-11D, ground
water flow appears to be re-directed to the north and to exit the
Site in the vicinit'y of MW-BS. Ground water flow south of this
divide appears to belre-directed to the southwest, where it follows
the course of a small drainage basin.
The uppermost aquilfer beneath the .site is underlain by the
uppermost confining! layer (see Figure 3-3 and Figure 3-4.). As
indicated in the drilling logs of the monitor well and exploratory
borings, the uppermost confining layer is continuous across the
site. Based upon the geophysical logs of USGS well cluster GS-02
and the drilling log'.s of the installed off-site monitor wells, the
uppermost confining ~ayer also extends north, south and west of the
Site. In addition,~ review of the geophysical logs of other USGS
well clusters . in the vicinity of the Site indicates that the
uppermost confining layer appears to be present beneath most of the
higher elevation areas (above approximately 420 ft. msl) in the
region surrounding the Site. However, based on the elevation of
the confining layeribeneath the Site and elevations indicated on
the topographic map of the area (Figure 2-1), it appears that this
' • I • confining layer may outcrop in the valley created by Aberdeen Creek
3-5
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
at a distance appi;-oximately 2,000 feet west of the Site. The
location of the other USGS well clusters in the vicinity of the
site and their corresponding geophysical logs are presented in
Appendix 3-B. The !area-wide existence of the uppermost confining
layer is consistent with the interpretation of this layer as the
Black Creek confin~ng unit.
The uppermost confihing layer beneath the Site is a very stiff, tan
slightly sandy clai. The sand content in the uppermost confining
layer ranged from 10% near the top of the layer to 30% near the
base. The sand grain size generally increased downward from very
fine-grained in th~ upper portion to medium-grained at the base.
Laboratory tests ofisamples collected from the uppermost confining
layer indicated a permeability on the order of 10-8 cm/sec (see
Section 3.4.2). I
Drilling logs indicate that for the area immediately underlying the
site, the thickness of the uppermost confining layer ranges from
approximately 6 to ;20 feet. As illustrated in cross section A-A'
(Figure 3-3), the thickness of the uppermost confining layer near
the eastern edge of lthe Site is approximately 20 feet (wells MW-140
.and MW-15D), thins to approximately 6 feet near the center of the
Site (well pair MW16 and MW-6D), and is believed to increase to
approximately 10 feet in thickness near the western tip of the Site
(well MW-13S). Thelthickness of the uppermost confining layer at
the western edge of the site can only be inferred as the confining
layer was not penetrated at well location MW-3S, MW-7S, MW-12S, or
MW-13S. However, based upon the geophysical log at· USGS well
cluster GS-02, the uppermost confining layer is inferred to have an
approximate thickness of 10 feet near city Well MUW-04.
Split spoon samples collected during the drilling and installation
of monitor well MW-11D, located approximately 360 feet south of the
site, indicate thatlthe thickness of the uppermost confining layer
at this location thi,ns to approximately one foot. The thickness of
the uppermost confining layer at well MW-lOS, which lies mid-way
between MW-11D and I location of former Warehouse A is therefore
estimated to be approximately 6 feet.
A contour map of the I upper contact of the uppermost confining layer
(Figure 3-6) indicates that the surface of the clay layer is
undulatory and exhibits a depression in the vicinity of well MW-6S
I and MW-6D. The presence of a lens of well sorted, coarse to very
' . . coarse sand on top of this contact at well pair MW-6S and MW-60 and
MW-2S suggest that the surface of the uppermost confining unit may
have undergone lodal scouring during. the deposition of the
overlying sands. I
3.2.2 Second Uppermost Aquifer
The second uppermosJ aquifer at the Site extends from the base of
the uppermost confirting layer to the top of the second uppermost
confining layer (see Figure 3-3) and is approximately 40 feet in
thickness. The sedond aquifer is generally composed of medium
3-6
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
compact to compact, multi-color (purple, yellow, tan, pink and gray) silty and clayey sands. Based upon visual observations of soil cores, the total silt and clay content in the second aquifer ranges from approx~mately 20% to 40%. The sand in the aquifer is generally fine to coarse-grained and subrounded to subangular in shape. I
Thin clay layers (up to two inches in thickness), gently dipping laminations (up to\ 10°), hematite-cemented sandstone layers and pebbles occur loca]ly throughout the second aquifer. The bottom seven to eight feet of the second aquifer is composed of medium compact, silty finei, to coarse sands. Silt content in this lower zone is approximate•ly 30%.
An approximate two-~oot thick lens of sandy clay was noted in the second aquifer at monitor well location MW-1D only, at a depth of 82 feet below ground level. A compact, gravelly coarse to very coarse sand layer is also present beneath the far eastern portion of the Site in the [second aquifer (see Figure 3-3). The coarse layer was encountered at well locations MW-1D, MW-4D and EB-1. This layer is approximately eight feet thick and occurs at a depth of approximately 85\to 90 feet below ground level.
Saturated conditions within the second aquifer were found to occur at depths ranging from 100 feet (MW-15D) to 67 feet (MW-6D) below ground level. Thislindicates that ground water within the second aquifer occurs at a depth of approximately 3-15 feet below the base of the overlying upp'ermost confining layer, which was confirmed by ground water levelJ measurements from the Site monitor wells screened in the second aquifer. Ground water elevation data for the monitor wells screened in the second aquifer (MW-1D, MW-4D, MW-6D, MW-11D, MW-14D a:nd MW-15D) are presented in Table 3-2.
1 I . . A ground water e evation contour map for the second aquifer, constructed from water level measurements obtained July 8, 1991 is presented in Figurel 3-7. The ground water elevation map was constructed based upbn triangulation of the ground water elevation data from the six monitor wells screened in the second aquifer. The ground water el~vation data indicate that the direction of ground water flow within the second aquifer is toward the west-northwest. In order to investigate the variability of flow direction within the[second aquifer, the direction of ground water flow was determined f,or each of the ground water measurement events completed from October 1990 to February 1991 and July 1991. (Table 3-2). The ground water elevation data indicate that the ground water flow during this period ranged from a west to northwest direction. The average hydraulic gradient for the second aquifer was calculated to be 0.003 ft/ft (0.3%), as measured between MW-14D and MW-6D. I
Ground water elevation data was also collected February 6, 1991 concurrently from thei on-Site Phase 2, Step 1 monitor wells (Table 3-2) and USGS wells screened in the equivalent elevation as that of the second aquifer (Appendix 3-B). The data confirm that the
3-7
I
I
I
I
I
I
I
I
I
I
I
I
I
D
I
I
I
I
I
overall direction of flow in the second aquifer is generally in a
northwesterly direction.
Because the seconk uppermost aquifer is located between two
confining layers, 1[ground water in the second aquifer would be
expected to occur under confined conditions. Under normal
conditions, saturated deposits within a confined aquifer would be
expected to occur immediately below the base of the upper confining
layer. In addition I, the water level elevation, as determined from
an observation welli in the confined aquifer, would be expected to
rise above the base1 of the confining layer overlying the confined
aquifer. This is due to the existence of overlying impermeable
strata creating hydrostatic pressure within the aquifer which is
greater than atmospheric pressure. As noted previously, however,
saturated deposits and the water level elevation within the second
aquifer were determined to be at a depth of approximately 15 feet
below the base of the overlying confining layer. This condition
may be attributed td several factors or a combination of factors as
discussed below. I
First, Winner and Coble (9), in their study of the hydrogeologic
framework of the North Carolina Coastal Plain, indicate that this
condition exists throughout the Sand Hills region. They note that,
because of the dissected nature of the Sand Hills, the Middendorf
clays that serve a~ the confining unit are cut through in many
places by stream channels. Where this occurs, the Black Creek
aquifer discharges Ito the streams and, therefore, may only be
confined beneath hilltops. The inferred outcrop area of the second
uppermost aquifer, I based upon the elevations of the aquifer
boundaries beneath the Site, is presented in Figure 3-8. As
depicted in Figure ,3-8, the valley through which Aberdeen Creek
flows cuts through [ the second uppermost aquifer at a distance
approximately 2,000-3,000 feet west of the Site. At this point,
the second uppermos~ aquifer beneath the Site would become a water
table aquifer. The~efore, it is probable that the second aquifer
is exhibiting unconfined conditions beneath the Site due to its
proximity to the outcrop of the aquifer to the west.
Secondly, the aquif~r may have been dewatered due to ground water
withdrawal by pumping from municipal and private wells screened in
this aquifer. Dewatering would cause a decline in the piezometric
surface in the aquifl3r as the ground water storage in the aquifer
was depleted.
As noted previously, based upon the elevations of the boundaries of
the second uppermost aquifer beneath the Site, the valley through
which Aberdeen Creek flows cuts through the entire thickness of the
second aquifer. The projected outcrop area of the second aquifer
west of the Site is depicted in Figure 3-8. As seen in.Figure 3-8,
the base of the s~cond aquifer is located at an elevation
approximately 40 feet above the elevation of Aberdeen Creek, and,
therefore, is not dlirectly hydraulically connected to Aberdeen
Creek. Rather, grouhd water from the second aquifer beneath the
Site apparently discharges to small streams to the west which then
3-8
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
flow in a westerly direction toward Aberdeen Creek.
Based upon the reported screen elevations of MUW-04 (see Figure 3-
3) and other City of Aberdeen municipal supply wells, the Site's
second uppermost aquifer is utilized as a local source of potable
water. Construction details (i.e., screen intervals) of private
water supply wells] in the vicinity of the Site are not known.
However, the total depth of the private wells in the area indicate
that the second aquifer is the primary production zone for the
private wells. Thel Site uppermost aquifer is not considered to be
an important source due to its limited saturated thickness and low
yield. In addition, none of the municipal wells are known to be
screened in the uppermost aquifer.
I Beneath the site, the second aquifer is underlain by the second
uppermost confining1 layer, as depicted in Figure 3-3 and Figure 3-
4. The second confining layer was encountered at MW-4D, MW-6D and
EB-1. As indicated] in the Site drilling logs and geophysical logs
of USGS well cluster GS-02 (Appendix 3-B), the second confining
layer is interprete1d to be continuous beneath the Site, extending
to at least Aberdeen City Well MUW-04. In addition, an analysis of
the geophysical logs of other USGS well clusters in the vicinity of
the Site (Appendix 3-B) indicates that the second confining layer
• I • • is present throughout the region near the Site.
The second confiniJg layer is generally composed of very stiff,
mottled gray, tan and red silty clay. Some minor sand clay zones
with approximately 10% fine to medium sand were noted in the upper
portion of the confining layer. The confining layer apparently
coarsens downward with sandy clay being present at the base of the
confining layer. An attempt was made to collect soil samples from
borings MW-4D and MW-6D for permeability testing. However, due to
the extreme hardness of the confining layer, the Shelby tube could
not be pushed to ah adequate depth into the layer to collect a
sample. I
Based upon the drill,ing and sampling of exploratory boring EB-1 and
monitor well PZ-1, the thickness of the second confining layer was
determined to be approximately 10 to 13 feet beneath the Site. In
addition, an analyi;is of the geophysical logs from USGS well
cluster GS-02, ind~cates the thickness of the second confining
layer near MUW-04 is approximately 10 feet.
3.2.3 Third Uppermlst Aquifer
The third uppermost\aquifer at the Site extends from the base of
the second confining layer to the top of the third uppermost
confining layer (see Figure 3-3). The third aquifer beneath the
Site is approximate:ly 60 feet in thickness as indicated by the
drilling log of EB-1.
Based on the drilliJg and sampling of PZ-1 and EB-1, the upper 30
feet of the aquifer lis generally composed of compact, multi-color
(tan, white, red and purple) silty sand. The sand in the upper
3-9
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
zone is primarily medium to coarse-grained and subrounded in shape.
Thin seams of sillty and sandy clay were noted to be present
throughout this upp1er zone. The lower 30 feet of the third aquifer
was drilled and elampled at EB-1 only, where it is generally
I • • • composed of compact, multi-color (tan, white, rust and purple)
gravelly sand. San1d within this lower zone is primarily medium to
coarse-grained with' the gravel size ranging up to 1/2" in diameter.
Some thin clay and silt seams are present in this lower zone.
Ground water in the third aquifer occurs under confined conditions.
Saturated deposits were noted immediately below the base of the
second confining layer and the piezometric head in the only monitor
well screened in this aquifer, PZ-1, rose approximately 40 feet
above the base of the second confining layer. The depth to ground
water in monitor well PZ-1 was determined to be approximately 68
feet below ground 11evel. Water level measurements completed from
monitor well PZ-1 alre presented in Table 3-2. The single monitor
well screened in th~ third aquifer did not allow for determination
of ground water flow direction or hydraulic gradient in this
aquifer. However, I water level data collected February 6, 1991
concurrently from PZ-1 (Table 3-2) and USGS cluster wells screened
at the approximate equivalent elevation as the third aquifer
(Appendix 3-B) indicate that the overall direction of flow is
I generally toward the northwest.
I It should be noted that, based upon the screen intervals of
Aberdeen City Well 1MUW-04, the third aquifer beneath the site is
interpreted to be the equivalent of the primary production zone
(screened interval)lof MUW-04. The screen interval elevations of
MUW-04 are presente~ in Figure 3-3. In addition, it is believed
that the on-Site water supply well (WSW), located at the east end
of former Warehouse A (see Figures 3-1 and 3-3), may also be
screened in the third aquifer. This interpretation is based upon
a knowledge of the depth of the on-Site water well (determined to
be approximately 140 feet below ground level) and the level of the
pump setting in the. well (approximately 126 feet below ground
level). The exact sbreen interval or other construction details of
the on-site water supply well, however, are not known. The pump
within the on-Site ~ater supply well was pulled during the RI and
the well is no longer active.
The depth to water i!n the on-Site water supply well was determined
to be approximately 80 feet below ground level, corresponding to an
approximate elevation of 396 ft. msl (See Table 3-2). The ground
water elevation at the WSW does not correspond with the
potentiometric datal collected from wells screened in the Site
second uppermost aquifer but does correspond with the ground
elevation data coll~cted from well PZ-1, which is screened in the
third aquifer beneath the Site. This provides further evidence
that the on-Site wat'er supply well is solely screened in the third
aquifer beneath the !Site.
The third uppermost confining layer beneath the Site directly
underlies the third aquifer (see Figure 3-3). The upper portion of
3-10
I
I
I
I
I
I
I
I
I
I
I
I
I
g
I
I
I
I
I
the third confining layer was encountered during the drilling of
the exploratory boring only, as no other borings at the Site were
advanced to a suffi!cient depth to encounter this layer. The third
confining layer wa!s found to consist of very stiff, gray-brown
silty clay to clay~y silt with minor (approximately 10%) very fine
sand. The thickness of this layer beneath the site is not known.
Based upon an amhysis of the USGS geophysical logs of well
clusters in the vic'inity of the Site, the third confining layer is
apparently present throughout the region. This is consistent with
the interpretation of this layer as the Upper Cape Fear confining
unit.
3.3 Monitor Well rnstallation
I 3.3.1 Drilling Methods
All monitor wells\ constructed at the Site were drilled in
accordance with the procedures outlined in Section 12. 2 of the
approved RI/FS Work\Plan. All of the monitor wells screened in the
uppermost aquifer at the Site (MW-lS through MW-6S) were completed
by the hollow stem ~auger method. An initial attempt was made to
drill monitor well MW-lD by the hollow stem auger method. However,
geologic conditions1\ prevented the successful completion of this
monitor well. As a result, it was decided to complete the
remaining monitor wells screened in the intermediate aquifer (MW-
lD, MW-4D, MW-6D, MW1-14D and MW-15D) by the mud rotary method. The
EPA approved the use of mud rotary to drill these monitor wells.
Monitor well number\MW-llD was originally intended to be screened
in the uppermost aquifer, and was therefore installed using hollow
stem augers. Howev~r, the saturated zone of the uppermost aquifer
was less than two fe'.et thick at MW-llD, and did not yield water to
a temporary well which was completed in the uppermost aquifer at
this location. Therefore, MW-llD was not screened in the uppermost
aquifer, but was completed as an intermediate monitoring well into
the second aquifer. I
3.3.2 Well Construction
The nineteen monitbr wells at the Site were constructed in
accordance with the !materials and methods prescribed in Sections
2.3.2.2 and 2.3.2.3 of the POP and/or in accordance with approved
modifications as det~iled in correspondence to the USEPA (16). A
summary of the construction details for each of the nineteen
monitor wells is presented in Table 3-3. Construction diagrams for
each of the monitor ~ells installed are presented in Appendix 3-C.
During the monitor Jell drilling program conducted at the site,
samples of the drilling mud, tap water, sand pack and bentonite
pellets utilized to complete the monitor wells were collected and
analyzed for quality
1
assurance purposes. In addition, rinseate
blanks were collected from decontaminated drilling and sampling
equipment to documJnt proper decontamination procedures. A
description of each of these samples, the analytical parameters for
3-11
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
which they were analyzed, and the results of the analyses are
presented in Appendix 3-D.
I 3.3.3 Well Development
Following the inst~llation of the ground water monitoring wells,
the wells were deve~oped to the fullest extent practical to remove
drill cuttings or other materials introduced during the drilling
operation. The process also developed the sandpack and borehole of
the well to minimiz:e pumping of fine-grained formation materials.
Development of the Phase 1, Step 2 wells began on September 7, 1990
and continued untillNovember 5, 1990. Development of the Phase 4,
Step 2 wells began on June 25, 1991 and was completed by July 10,
1991. Development! was accomplished by both hand bailing and
pumping methods.
Well development by bailing was accomplished using Teflon™, two-
inch diameter bailers. Well development was also accomplished
using Teflon TM and stainless steel bladder pump systems. Table 3-4
shows the well numbJr, the total volume of water evacuated from the
borehole and the cl~rity of the water after development and prior
to sampling. I
In addition to bailing and pumping, air surging was performed on
the deeper Site moniltoring wells (MW-lD, MW-4D, MW-6D, MW-llD, MW-
14D, MW-15D and PZ-1) to set the sand pack and to remove the fine-
grained material from the sediment trap. Following surging, the
wells were pumped to remove the suspended fine grained material.
I 3.3.4 Abandonment of Hollow stem Augers
I Three separate attempts were made to remove the 90 feet of augers
locked in the origirtal MW-lD borehole. On May 30, 1991 a Failing
Speedstar 200 drill \rig attempted to remove the augers by rotating
them before attemptilng to pull them out. The auger head adapter,
however, broke several times while attempting to turn the augers.
The augers were thi:refore abandoned by pumping bentonite/neat
cement grout insideithe augers. Ninety feet of tremie pipe was
used to pump approximately 300 gallons of grout inside the augers.
Grout was observed r
1
ising in the annular space between the augers
flights and the surface casing before rising inside the hollow stem
augers themselves. I
3.4 Physical Laboratory Tests
. . 11 . 3.4.1 Grain Size Ana ysis
. I . In accordance with Section 12.9 of the approved RI/FS Work Plan, a
I total of 15 samples were selected from the saturated zones of the
exploratory boring a~d monitor well borings for grain size analysis
(ASTM Method D422-63). The results of grain size analyses of
samples collected from the exploratory boring were utilized to
assist in the determilnation of sand pack grain size and screen slot
size for the monitor wells.
3-12
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
A table indicating the location, site aquifer designation,
classification and! percent fine material of each soil sample
selected for grain size analysis is presented as Table 3-5. The
individual grains size distribution graphs for each selected soil
sample are present~d in Appendix 3-E.
The results of the\ grain size analyses indicate that the three
aquifers beneath t,he Site are composed primarily of fine to
medium-grained sands containing between 10% to 30% by weight fine
material (clay and silt sized particles). Up to 5% fine gravel by
weight was noted in several of the selected soil samples.
3.4.2 Permeability: Tests
Laboratory permeability tests were conducted on two undisturbed
Shelby tube samples]collected from the uppermost confining layer at
the Site. The two samples were collected from the upper portion of
the first confining layer during the drilling of monitor well
borings MW-1D (65 to 66 feet) and MW-5S (49.5 to 50.5 ft.). The
permeabilities of] the samples collected from the uppermost
confining layer at MW-1D and MW-5S were determined to be 5.2 x 10·8
cm/sec and 4.14 x 110·8 cm/sec, respectively. The laboratory data
sheets for the perm~ability tests are presented in Appendix 3-E.
An attempt was made\ to collect undisturbed soil samples from the
second confining layer at monitor well borings MW-4D and MW-6D for
permeability testing. However, due to the extreme hardness of the
confining layer, the Shelby tube samples could not be pushed to an
adequate depth into the layer, and, therefore, no sample was
retrieved.
3.5 Aquifer Tests
In accordance with Section 12.8 of the approved RI/FS Work Plan,
I slug tests were performed at each Phase 2, Step 1 ground water
monitor well location. Rising head slug tests were performed at
those monitor wells\ in which the top of the screen was located
above the water table (MW-2S through MW-6S). Falling head slug
tests were performe1d at those monitor wells in which the water
level was above the ~
1
op of well screen interval (MW-lS, MW-4D, MW-
6D, and PZ-1). The slug tests were performed by instantaneously
removing (rising head test) or introducing (falling head test) a
slug into the monitor well and incrementally measuring water levels
with time. I
Values of hydraulic conductivity (Kl were determined from an
analysis of the collected slug test data at each Phase 2, Step 1
monitor well location. The calculated hydraulic conductivity
values are presented in Table 3-6. Slug test data sheets may be
referenced in Appendix 3-F. Values of hydraulic conductivity could
' ' not be calculated for wells MW-4S, MW-5S, or MW-4D since the water
levels recovered almost immediately following introduction or
removal of the slug 'volume.
3-13
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The calculated hydraulic conductivity values for those monitor
wells screened in the uppermost aquifer ranged from 3 x 10·4 cm/sec
to 6 x 10·3 cm/sec! with a geometric mean hydraulic conductivity
value of 1 x 10·3 cm/sec. Using the range of calculated hydraulic
conductivity values and the average hydraulic gradient for the
eastern portion of the site of 0.026 ft/ft (July 1991) and assuming
an effective porosi'.ty of 38% (mean of range in porosity values for
unconsolidated sands; Freeze and Cherry (17), the range of average
linear ground waterlvelocities in the uppermost aquifer beneath the
eastern portion of the Site is computed to be 0.06 to 1 ft/day.
Similarily, utilizing the calculated range of hydraulic
conductivities for ~he uppermost aquifer, an effective porosity of
38%, and the hydrauiic gradient calculated for the western portion
of the Site of 0.017 ft/ft (July 1991), the range of average linear
ground water velocities in the uppermost aquifer beneath the
western portion of 'ithe Site is computed to be 0.04 to 0.8 ft/day.
For the convegence zone, the range of average linear ground water
velocities is calcJlated to be 0.02 to 0.3 ft/day. These values
were calculated using the computed range of hydraulic
conductivities for the uppermost aquifer, an assumed effective
porosity of 38% and the August 1991 calculated hydraulic gradient
within the covergedce zone of 0.0076 ft/ft.
The calculated val!es of hydraulic conductivity determined from
those monitor wells screened in the second aquifer at the Site
ranged from 2 x 10·3 cm/sec to 3 x 10·3 cm/sec, with a geometric mean
value of hydraulic conductivity of 2 x 10·3 cm/sec. Using the
calculated range of hydraulic conductivity values and the average
hydraulic gradient (July 1991) for the second aquifer of 0.003
ft/ft, and, assuming an effective porosity of 38%, the range of
average linear grotind water velocities for the second aquifer is
' calculated to be 0.04 to 0.07 ft/day.
The calculated geombtric mean value of hydraulic conductivity for
those monitor we11J screened in both the second and third Site
aquifers of 2 x 10"3 lcm/sec is similar to that reported in NRCD (11)
for Middendorf sediments in the Sand Hills region of 19 ft/day (7
x 10·3 cm/sec). The balculated values of hydraulic conductivity for
those monitor wellslscreened in the uppermost Site aquifer are less
than the average va1lue of 29 ft/day (1 x 10·2 cm/sec) reported in
Winner and Coble (9)1 for the surficial aquifer in the Coastal Plain
region of North Carolina.
3.6 Ground Water S~mpling and Analysis
1 . I 3.6.1 Samp 1ng Procedures . I
Phase 2, step 1 ground water samples were collected on November 13-
16, 1990 from the ten on-site monitor wells and the on-Site water
supply well. Phasei4, Step 2 ground water samples were collected
July 10-12, 1991 from the on-Site intermediate wells and off-Site
wells including twolprivate wells and a USGS well. Sampling was
conducted in accordance with the procedures outlined in the RI/FS
Work Plan· and QAPP (~). A brief summary of the sampling procedures
3-14
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
is presented below.
3.6.1.1 Monitor Wells and On-Site Water Supply Well
I The depth to ground water at each well was determined pr~or to
purging. The wate!r level measurements were collected using an
electric water level indicator and recorded to the nearest 0.01
foot. The water level meter, as well as all ground water sampling
equipment, was decbntaminated prior to initial use and between
wells in accordance with the procedures outlined in the RI/FS Work
Plan (1).
Following the determination of water elevation measurements, each
well was purged cif a minimum equivalent to three times the
calculated casing v'olume of standing water in the well. With the
exception of MW-4S ,I wells sampled during Phase 2, Step 1 of the
investigation were purged using the QED Well Wizard TM pump system.
The system consists, of a Teflon TM bladder pump and tubing housed
in a stainless steel casing. Due to the limited volume of standin~
water in the well, MW-4S was purged using a closed top Teflon
bailer.
With the exception of MW-14D and MW-15D, wells sampled during Phase
4, Step 2 of the investigation were purged with Teflon TM bailers
Wells MW-14D and MWll5D were purged using a Teflon TM bladder pump.
Field measurements !of temperature, pH, and specific conductivity
were made after each well bore volume of water was purged, or more
frequently, to determine whether the parameters had stabilized.
The stabilization I criteria for the field parameters were:
Temperature± 0.5°C, pH± 0.1 unit and specific conductance± 10
umhos/cm. If the parameters had not stabilized after three well
casing volumes of water were removed, purging continued until a
maximum of five volumes of water were removed.
Ground water samplel for Pha.se 1, Step 2 were collected using the
same pump (or in the1 case of MW-4S, the same bailer). During Phase
4, Step 2, shallow ~ells and MW-llD were sampled with the bailer
used to purge them. I A Teflon TM bladder pump was used to rurge MW-
14D and MW-15 before they were sampled with a Teflon T bailer.
Ground water samples were placed in clean, laboratory supplied
containers and preserved in accordance with procedures outlined in
Table B-2 of the (QAPP) (1). Each sample was sealed, labeled,
placed on ice, and shipped for overnight delivery to the designated
laboratory. Phase! 2, Step 1 samples were analyzed by IEA
Laboratory of Cary, INC; and, Phase 4, Step 2 samples were analyzed
by PACE, Inc. of •Minneapolis, MN. Proper chain-of-custody
documentation accompanied the samples. All sampling activities
were recorded in field log books.
I 3.6.1.2 Sampling of Off-Site Wells
As part of the Phasel4, Step 2 remedial investigation, two off-site
water supply wells were sampled during the first week of July 1991.
3-15
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
These wells are located east of the site at the Powdered Metal
Products facility a:nd Allred residence (see Figure 1-5). Because
the wells are in current use, and are equipped with submersible
pumps, the wells could not be sampled in the same manner as the
site monitoring wells. The following briefly describes information
obtained from interyiewing the owner/operator of the wells and the
procedure used to sample each well.
The first water supJly well sampled was the Powdered Metal Products
(PMP) well. Accord!ing to the plant manager, water from the well
is used to replenish water lost to evaporation from their cooling
system. The water is also used in the plant's rest rooms. Bottled
water is used for drinking at the facility.
The PMP well is locJted in a well house outside the plant building.
It is constructed 0 1f a six-inch casing and is 130 feet deep. The
screened zone was not known by plant personnel. A submersible pump
serves the well. The plant manager indicated that this was the
seventh pump in the well because of electrical damage to the
previous pumps. A discarded Grundfos TM submersible pump was
located inside the !plant building a few feet from two air tanks
which pressurize the system. A hose was connected to the system
and allowed to flush approximately 15 minutes. Temperature, pH and
specific conductivfty stabilized after an estimated 105 gallons
I were purged and had values of 18.5°C, 4.0 and 24 umhos/cm
respectively beforeisampling. The hose was removed and the sample
collected in VOA vials. Because the faucet was located too close
to the plant floor to permit the VOA vial from being held upright
while being filled!, another VOA container had to be used to
transfer water to the containers. The PMP plant manager observed
the sampling of thelwell.
The second water supply well which was sampled was the Allred well.
The well is used bylthe residents for irrigating a garden and for
household use although bottled water is used for drinking. The
well is located in al well house adjacent to the residence. A four-
inch galvanized ste~l casing is visible at the surface. The well
contains a submersible pump and according to the home owner, is
either 80 or 100 feet deep. The screened zone was not known by the
home owner. I
The well was sampled from a faucet located at the well house.
Seventy-five gallon's of water were purged before the well was
sampled. Indicator: parameters were stable after 40 gallons and at
sampling had the following values: temperature of 18.2°C, pH of
4.9 and conductivit~ of 28.7 umhos/cm. VOA containers were filled
directly from the faucet. Mr. Allred was present during sampling.
3.6.2 Phase 2, SteJ 1 Analytical Results
The ground water sam~les were analyzed in accordance with the USEPA
Contract Laboratory[ Program (CLP) for the Target Compound List/
Target Analyte List (TCL/TAL) parameters. T.he analytical results
are discussed in the following sections and a summary of the
3-16
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
analyses for the field parameters and each fraction (i.e.,
volatiles, semi-volatiles, pesticides and metals) is provided in
Tables 3-7 through :3-11. In addition, a graphic representation of
the constituents detected at or above the detection limit is
presented in Figur~s 3-9 through 3-11.
3.6.2.1 Field ParJmeters
.. dtl dt t t Specific con uc a~ce, pH an empera ure measuremen s are
summarized in Table 3-7 and illustrated on Figure 3-9. As
indicated, specifid conductivity in the shallow wells ranged from
50 umhos/cm at upgradient well MW-lS to 600 umhos/cm at MW-6S. The
pH measurements in the shallow wells ranged from 6.9 in upgradient
MW-lS to 3. 8 in MWJl6S.
The specific conductivity and pH measurements for the intermediate
wells and the deep well were less variable across the Site.
Specific conductivity ranged from 20 umhos/cm in the water supply
well to 40 umhos/cm in MW-4D. Well PZ-1, screened in the third
uppermost aquifer, had a specific conductance of 90 umhos/cm and a
pH of 6.8. The pHlvalues for the intermediate wells ranged from
5.6 in the water supply well to 6.8 in MW-4D. Temperature values
for all of the wells ranged from 16.5°C at upgradient well MW-lS to
20.1°c at MW-2S.
3.6.2.2. TCL Volatiles
Analytical result~ for the volatile organic parameters are
summarized on Tabl~ 3-8. Figure 3-10 provides an illustration of
the constituents identified above the detection limit.
Trichloroethene wa1 not detected in the shallow wells or the
upgradient wells at the Site and has not been previously detected
in the Site soils.
1
Trichloroethene was, however, detected in wells
MW-4D and MW-6D at concentrations of 200 ug/1 and 11 ug/1,
respectively. TriChloroethene has previously been detected in
other wells aroundl the Aberdeen area, as evidenced in samples
collected in October 1989 by EPA Region IV ESD (Reference Appendix
3-G). The October 1989 samples indicated trichloroethene in
private wells ownediby Allred (GC-PW-03) and Powder Metals (AP-PW-
02) at concentrations of 34 ug/1 and 330 ug/1, respectively. Both
properties are upgr'adient of the Site.
3.6.2.3 TCL Semi-Jolatiles
Results of the semi~volatile analyses are summarized in Table 3-9.
Semi-volatile constituents were not detected above the detection
limit.
3.6.2.4 Pesticides
The analytical resullts for pesticides are presented in Table 3-10
and the constituent's detected above the detection limit are shown
on Figure 3-11. As indicated, pest-icides were detected in all on-
3-17
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
site shallow wells except the upgradient well MW-ls. Pesticides
were not detected :Ln the intermediate and deep wells.
The BHC isomers (tdtal) ranged from 2.2 ug/1 in MW-3S to 107 ug/1
in MW-6S. The Max.i!mum Contaminant Level for gamma-BHC (0.2 ug/1)
(18) was exceeded .i!n all shallow wells. Aldrin and Dieldrin were
detected in wells MW-4S (0.1 ug/1 and 0.2 ug/1, respectively).
Endrin ketone was dltected in wells MW-2S (0.4 ug/1) and MW-4S {0.2
' . ug/1). Toxaphene was found in MW-2S (610 ug/1) and MW-4S (4.5
ug/1). The primary drinking water standard for toxaphene is 3 ug/1
( 19) .
3.6.2.5 TAL Metals
I Results of the metals analyses are summarized in Table 3-11.
Arsenic, barium, dadmium, chromium, mercury, nickel, selenium,
silver and zinc w.kre either not detected or were detected at
concentrations below the Federal Drinking Water Criteria (20). The
secondary drinking water standard for iron (300 ug/1) was exceeded
in six wells including both upgradient wells (MW-lS and MW-1D).
The concentrations 'of iron ranged from not detected at wells MW-5S
and MW-6S to 4,790 iug/1 at the on-Site water supply well. Copper
was detected in the water supply well at a concentration of 1,180
ug/1 which is slightly above the Secondary Maximum Contaminant
Level (MCL) of 1,000 ug/1 (20). Lead was not detected above the
I MCL of 50 ug/1 or the CERCLA/EPA cleanup level of 15 ug/1.
Continued monitorihg of the TAL metals was determined to be
unwarranted. I
3.6.3 Phase 4 Step 2 Analytical Results
The Phase 4, Ste! 2 ground water samples were analyzed in
accordance with the Contract Laboratory Program (CLP) for the TCL
pesticides and/or ~olatile organics. The samples were analyzed
' . . under the March 199I0 Statement of Work (SOW) which took effect 1n
July 1991. Monitor Wells MW-7S through MW-l0S, MW-12S, MW-13S, MW-
11D, MW-14D and MW-15D were analyzed for TCL pesticides and
volatile organics. I USGS-02-03 was analyzed for pesticides only.
Wells MW-1D, MW-4D, PZ-1, the Allred well and the PMP well were
analyzed for TCL v'olatiles only. Based on the Phase 2, step 1
analytical result~, metals analyses were determined to be
I unwarranted for the Phase 4 step 2 program. The Phase 4, step 2
analytical results lare discussed in the following sections.
3.6.3.1 Field Parameters
Specific conductande, pH, temperature and turbidity measurements
are summarized in Table 3-12 and illustrated on Figure 3-12. As
indicated, specifiq conductivity in the shallow wells ranged from
14 umhos/cm at MW-8S to 84 umhos/cm in MW-10S. The pH measurements
ranged from 4.3 in MW-13 to 6.9 in MW-l0S. Turbidity ranged from
8.9 NTUs in MW-l0S to 78 NTUs in MW-7S.
I
I
I
I
I
I
I
I
I
I
u
I
I
I
I
I
I
I
I
The specific conductivity in the intermediate wells ranged from 24
• I • • umhos/cm in the PMP\ Well to 81 umhos/cm in the upgradient MW-14D.
The values for pH ranged from 4. O in the PMP Well to 7. 1 in
upgradient well MW-14D. Turbidity ranged from 80 NTUs at MW-6D to
600 NTUs at MW-15D1. Temperature measurements of all the wells
' ranged between 17.0rC and 19.1°C.
3.6.3.2 TCL Volatiies
The primary purposelof sampling for volatile organic constituents
was to confirm that trichloroethene indicated in on-Site
intermediate wells\ during the Phase 2, Step 1 ground water
investigation was originating from an off-Site source. Three deep
wells, MW-1D, MW-140 and MW-15D, installed upgradient of the Site,
were sampled. Two upgradient private wells (i.e., Allred and PMP)
were also sampled. 1The analytical results are summarized in Table
3-13 and illustrated on Figure 3-13.
Trichloroethene was\detected in both private wells. The PMP Well
indicated trichloroethene at 360 ug/1 and the Allred well at 72
ug/1. Trichloroethene was also detected in Site wells MW-4D and
MW-6D at concentratibns of 160 ug/1 and 47 ug/1, respectively. The
Phase 4, Step 2 trichloroethene results for MW-4D and MW-6D were in
the same range as those detected in the Phase 2, Step 1 study
(i.e., 200 ug/1 in MW-4D and 11 ug/1 in MW-6D).
3. 6. 3. 3 TCL Pestici\des
The Phase 4, Step 2 p\esticide results are summarized on Table 3.-14.
Pesticides were not detected in the shallow wells north of the Site
(i.e., MW-7S, MW-8S and MW-9S) or in the USGS well downgradient of
the Site. Pesticide~ were detected in two wells: MW-lOS and MW-
11D. Both wells are\located south of the Site and appear to be on
a hydraulic gradien,t parallel to the Site. Total pesticide
concentrations in MW-lOS were 36.3 ug/1 and in MW-11D were 39.7
ug/1.
3-19
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
a
I
4.0 SOIL INVESTIGATIONS
4.1 General
An investigation of surface and subsurface soils was conducted in
accordance with the procedures outlined in Task 11 of the approved
RI/FS Work Plan (1)1 The investigation consisted of four sampling
phases to delineate the vertical and horizontal extent of
contamination. Phase 1 provided a definition of Site specific
parameters; Phase 2 ~efined the horizontal extent of contamination;
Phase 3 delineated the vertical extent of contamination; and, Phase
4 provided additional information to fill in gaps in the data. The
following sections !provide a description of soil types, sample
locations and analytical results for each sampling phase.
· 1 · t· I 4.2 Soi Descrip ion
Surface soils incltde soils occurring from ground level to a
maximum depth of one foot. Surface soils at the Site are composed
primarily of loose to medium compact, gray to light and dark brown
sand and silty sands. The total silt content in the surface soils
ranges from. 20% to I 30%. Sands are generally well-sorted and
medium-to fine-grained. Natural material is present throughout the
surface soils. I
Subsurface soils, encountered at a depth of one to ten feet below
grade, are primarily composed of medium-compact to stiff,
multicolor (i.e., brbwn, white~tan, orange-brown, rust, red-brown),
• I • • silty sands and clayey sands. The total silt and clay content in
the subsurface soilsl ranges from 10% to 50%. The sand is generally
poorly sorted and fine-to coarse-grained. Pebbles, up to 0.25
inches in thickness, occur locally throughout the subsurface soils.
4.3 Soil Sampling
4.3.1 Phase 1 Soil Sampling and Analysis
Eleven surface soil samples were originally collected and analyzed
in accordance with the CLP for the TCL/TAL parameters. The purpose
of this phase of sampling was to define the constituents of concern
(i.e., site specific parameters) to be analyzed in the remaining
phases. . I ,
The surface soil samples were collected from ground level to a
maximum depth of one foot. Sample locations were staked and . . ' located by engineering survey methods for future reference. Sample
collection and anal~ses and equipment decontamination procedures
were in accordance with the procedures outlined in the RI/FS Work
Plan and Project Operations Plan.
I The analytical results for the Phase 1 soil samples are presented
in Table 4-1 and are !illustrated in Figure 4-1. Volatile and semi-
4-1
I
I
I
I
I
I
I
I
I
I
I
I
I
B
I
I
I
volatile constituents were not detected in concentrations above the
detection limit. M6st of the metals concentrations were within the
range of the concentrations detected in the background sample (SS-
04). Pesticides ~ere detected in all samples including the
background sample (SS-04). The BHC isomers, total DDT and
toxaphene were the most prevalent pesticide compounds detected.
Two samples (SS-03 and SS-06) also contained aldrin and dieldrin.
The concentrations I of total BHC, total DDT and toxaphene are
depicted on Figure 4-1. Aroclor compounds were not detected in any
sample. I
Based on the results of the Phase 1 soils investigation, pesticides
were selected as the Site specific parameters for analysis. In
addition, EPA requested that copper and zinc, which were used as
micronutrients in fJrtilizer, and lead, which had been indicated as
a parameter of conci:irn in regional ground water, be included in the
site specific sampling parameters.
4.3.2 Phase 2 soil sampling and Analysis
In order to obtain a representative picture of potential Site
contamination, a forty-foot grid was established over the Site as
shown in Figure 4.!.2. Samples on the grid were located by
engineering survey \methods for future reference. Ninety-four
surface soil samples were originally collected in accordance with
the procedures outli'ned in the approved RI\FS Work Plan and POP and
were analyzed for th'e Site specific parameters (i.e., pesticides,
copper, lead and zinc).
A summary of the PhJse 2 soils analytical results is presented in
Table 4-2. In addition to the grid samples, two background soil
samples (SS-121 and I SS-122) were obtained north and east of the
Site as shown in Figure 4-2 and a sample was collected from the
scale pit (SS-110). iThe sample from the scale pit was analyzed for
the Site specific parameters. The background soil samples were
I analyzed for the full TCL/TAL parameters. A summary of the
pesticides and metals results for the background samples is
presented in Table 4f-3. DDT, as well as toxaphene, were detected
in the background samples at less than 500 ug/kg total pesticides.
No volatile or semi1-volatile constituents were detected in the
background samples.
The analytical data was reviewed to determine which sample
locations contained !significant concentrations of Site specific
parameters. The term significant was defined in the RI/FS work
plan as a soil concentration level of 10 mg/kg or greater total
BHC, total DDT or to~aphene. Table 4-4 provides a summary of the
sample locations exhibiting significant concentrations of
pesticides. Figure 14-3 indicates the locations of samples with
concentrations between 10 mg/kg and 100 mg/kg. Only two samples,
SS-63 and ss-110 exhlibited pesticide concentrations greater than
100 mg/kg. I
Lead concentrations generally ranged from the Phase 2 background
4-2
I
I
I
I
I
I
I
I
I
I
I
g
I
I
I
I
I
I
I
concentrations (7. 6 at SS-121 mg/kg and 20 mg/kg at SS-122) to
approximately 100 ~g/kg. The lead concentration at the Phase 1
background location (SS-04) was 74 mg/kg. Phase 2 samples with
lead concentrations1 greater than 100 mg/kg are as follows:
Location /Lead Conclntrationl Location (Lead Concentration)
SS-20 (207 mg/kg)
SS-82 (336 mg/kg)
SS-37 (120 mg/kg)
SS-107(188 mg/kg)
SS-25 (113 mg/kg)
SS-83 (222 mg/kg)
SS-84 (125 mg/kg)
SS-103(198 mg/kg)
All of the samples listed above are located along State Highway
211.
Zinc concentrations ranged from background concentrations ( 15. 3
mg/kg at SS-121 and 20.5 mg/kg at SS-122) to 732 mg/kg at SS-122.
The zinc concentration at the Phase 1 background soil location (SS-
04) was 38. 3 mg/kg. I
Concentrations of copper generally ranged from not detected to less
than 40 mg/kg. Background copper concentrations were at or below
the detection limit.I
4.3.3 Phase 3 Soil Sampling and Analysis
The approved RI/FS Work Plan required that an extended sampling
program be conducted at those grid point locations identified in
the Phase 2 sampling[ effort as containing concentrations of total
BHC, total DDT and toxaphene at concentrations greater than 10
mg/kg (Table 4-4). ,rn order to meet schedule compressions in the
RI/FS schedule, Phases 3 and 4 of the soil sampling effort, as
defined in the RI/FSI Work Plan, were modified.
The revised Phase 3 sampling program, as approved by EPA, included
two components. Sa~ple grid locations exhibiting concentrations
between 10 ppm and 100 ppm (Table 4-4) were resampled at two-foot
and five-foot depth intervals. Sample grid locations with
concentrations great~r than 100 mg/kg (Table 4-4) were sampled at
two, five and ten-fo6t depth intervals. The samples were analyzed
for the Site specific parameters (pesticides, copper, lead and
zinc). In addition, !EPA requested that ten percent of the samples
be analyzed for the TCL/TAL parameters and, one location, SS-82, be
analyzed for lead at[the two and five-foot depth intervals. Lead
analysis at SS-82 was requested by EPA to assess the potential
vertical migration ofi lead found in surface soils near the highway.
Table 4-5 provides a list of the samples collected and analyzed for I the TCL/TAL parameters. Samples were collected as close as
possible to the original surface sample locations; however, some
locations were moved five to ten feet to accommodate the drill rig.
Soil borings were drllled with hollow stem augers in accordance
with the procedures dutlined in the RI/FS Work Plan. Sample SS-
4-3
I
I
I
I
I
I
I
I
I
I
I
n
I
I
I
I
I
I
I
110, which was inaccessible to the drill rig, was collected with a
hand auger. Sampl~ collection was achieved with a large diameter
(i.e., three-inch) I split spoon sampler to allow recovery of a
sufficient sample volume for laboratory analysis in accordance with
CLP criteria. Samples, with the exception of those split with EPA,
were collected at one-foot depth intervals (i.e., zero to one foot,
two to three foot, ietc.). Samples split with EPA were collected
and composited over
1
a two foot depth interval (i.e., one to three
feet, four to six f~et, etc.) to ensure collection of an adequate
sample volume. Decontamination of the augers and sampling
equipment was in acbordance with procedures outlined in the RI/FS
Work Plan. I
The two, five and ten-foot depth samples were sent to Compuchem
Laboratories for CLP analysis. The CLP laboratory analytical
results for the Site specific parameters are presented in Table 4-
6. The TCL/TAL vo1latile, semi-volatile and metals results are
presented in Table 4-7. No volatile or semi-volatile constituents
were detected in concentrations above the detection limit.
In addition, select \samples were analyzed for Total Organic Carbon
(TOC) and Cation Exchange Capacity (CEC). This data, presented on
Table 4-8, is to be used to assess contaminant migration and
mobility.
Twenty samples at the two-foot depth interval indicated the
presence of pesticide constituents. Of those samples, only three
indicated total pestlicide constituents greater than 10 mg/kg: ss-
51-2 (50 mg/kg), ssJi5s-2 (32 mg/kg), and ss-100-2 (24 mg/kg).
Pesticides were detected in ten samples (Table 4-9) at a depth of
five feet; however, [only one sample (SS-73-5) exhibited a total
pesticide concentration greater than 10 mg/kg. Four samples
indicated concentrations of pesticides at the ten-foot sample
interval. As shownion Table 4-10, constituents detected in the
ten-foot sample interval were well below 10 mg/kg.
. I Concentrations of copper ranged from 1.1 mg/kg (SS-92-2) to 27.5
mg/kg (SS-81-5). Zinc concentrations ranged from 1.6 mg/kg (SS-73-
10) to 76. 2 (SS-109-2'); and, concentrations of lead ranged from 1. 2
mg/kg (SS-92-2) to 68.9 mg/kg (SS-109-2). Lead concentrations in
sample SS-82 were 3 ·\so mg/kg at the two foot depth interval and
1.80 mg/kg at the ten foot interval. The concentrations of lead in
the subsurface soils1 were two orders of magnitude less than the
surface soil lead cohcentrations indicated in the Phase 2 sample
(i.e., 336 mg/kg). I
4.3.4 Phase 4 Samples -Additional Information
Additional samples w1re collected and analyzed at various stages
during the RI study. I The purpose of these sampling efforts was to
obtain more information on Site characteristics and to further
delineate the extentl of contamination. A description of these
additional samples is provided below.
4-4
I
I
I
I
I
I
I
I
I
I
I
I
I
u
I
I
I
I
I
4.3.4.1 Off-Site Soil Boring
. h 't ' I t' t' d t db ' ( ) ·1 During t e Si e in~es iga ion con uc e y NUS in 1988 7 , soi
samples were collected near an old foundation located south of the
Geigy Chemical Corporation (Reference Figure 4-4). The previous
use of the foundatil:m Site and the original purpose of the former
foundation are not \known. The results of the NUS study indicate
isomers of BHC and toxaphene at a depth of 22 feet below ground
surface.
Although the foundation is not located on the Geigy Chemical
• • I • Corporation Site property and the USEPA and NUS could not specify
the exact location of the sample point, the PRPs agreed to collect
samples from a soillboring near the old foundation. Samples were
collected using spl:i!t spoon samplers and a truck-mounted drill rig.
The samples were collected at the following depth intervals: 0-1
foot, 5-7 feet, 10-12 · feet, 15-17 feet and 20-22 feet. The
analytical results, [presented on Table 4-11, indicate 0.057 mg/kg
total DDT in the surface sample. Endosulfan sulfate was detected . ' in the 5-7 foot, lp-12 foot and 15-17 foot samples. However,
endosulfan sulfate has not been detected in on-Site soils at the
Geigy Chemical Corporation Site.
I 4.3.4.2 Semi-Volatile Samples
I EPA requested that the PRPs collect soil samples in the vicinity of
the former concrete[pad and railroad track for analysis of semi-
volatile constituents. The PRPs agreed to collect two surface soil
samples and a sampl~ of wood chips collected from a railroad tie.
As indicated on Figure 4-4, one sample, SV-1, was a surface sample
located between ss-1110 and ss-10; sample SV-2 was located between
SS-71 and SS-72; and) sample SV-3 was located approximately 20 feet
south of SV-2 on the' railroad tie. Sample SV-3 consisted of wood
chips collected by boring through a railroad tie with a drill.
Soils at these sample locations were subsequently removed during
the March through April 1991 removal action.
4.3.4.3. Horizontal Delineation of Contamination
The PRPs elected to collect additional surface samples to further
define the horizontal1 extent of pesticide concentrations greater
than 10 mg/kg. Alis~ of the sample locations is provided as Table
4-12 and shown on Figure 4-4. The samples were collected in
accordance with the procedures outlined in the approved RI/FS Work
Plan. A summary of the analytical results is presented on Table
4-13. Three samples indicated total pesticide concentrations I greater than 10 mg/kg. These samples are: SS-58-20S (290 mg/kg),
SS-63-20S (73 mg/kg)) SS-91-l0N (32 mg/kg).
4-5
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I I
s.o Ditch Sediment Investigation
5.1 General
An investigation of ditch sediments was conducted in accordance
with the procedures\outlined in Task 13 of the approved RI/FS Work
Plan (1). The ditches convey stormwater runoff from the highway,
railroad and Site, I and are normally dry. There are no surface
water bodies on-site. The nearest perennial surface water body is
Aberdeen Creek located approximately 4,000-5,000 feet west of the
Site.
The ditch sediment investigation consisted of three phases to
delineate the horizontal and vertical extent of contamination. The
first step, Phase 2, included the collection of on-Site surface
samples of ditch sbdiments to define the horizontal extent of
contamination. Phase 3 included the collection of samples at one
and two-foot depth intervals as well as samples downgradient of
Phase· 2 samples containing significant concentrations of
pesticides. Phase 4
1
ditch sediment samples were collected at two,
five and ten foot depth intervals at locations exhibiting
significant concentrations of pesticides in the surface soils. All
samples were analyzJd for the Site specific parameters.
5.2 Ditch Sediment \Description
I Sediments, as described in this section, refer to materials that
have settled out of lstormwater occurring from the ground level to
a maximum depth of one-foot. Sediments at the Site are composed of
primarily tan to bro~n silty sands to sandy silts. The total silt
content in the sedim1ents ranges from <1 to 53 percent. Sands are
generally well sorted and are usually medium-to fine or coarse-to
fine-grained. Natur~l organic material is present in the upper 0 1 -
0. 2 5 feet of the sedliments. Also, rock fragments are not unusual
in the sediments. I
5.3 Ditch Sediment Sampling
5.3.1 Phase 2 Ditch Sediment Samples
Twelve on-Site ditch sediment samples and nine off-Site ditch
sediment samples wer~ collected for analysis. Sample locations are
shown on Figure 5-1·. \ The samples were analyzed in accordance with
the CLP procedures for pesticides, copper, lead and zinc.
The ditch sediment slmples, with the exception of OSD-28/29, were
collected from the ground surface to a maximum depth of one-foot.
Sample OSD-28 was coliected from the surface to a depth of 1.5-feet
and sample OSD-29 was collected from the same location at a depth
of 1.5 to 3 feet. The increased depth sampling was due to the
presence of sediments deposited at these locations. Sample
collection, analysis[, and decontamination procedures were in
accordance with the procedures outlined in the RI/FS Work Plan and
Project Operations P:Uan.
5-1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The analytical results are summarized in Tables 5-1 and 5-2 and are
illustrated on Figure 5-2. Pesticides were detected in all samples
both on-Site and 'off-Site. The BHC isomers, total DDT and
toxaphene were the lmost prevalent pesticides detected in on-Site
ditch sediments. Total DDT and toxaphene were also detected in
off-Site ditch sediments.
Total BHC concentrktions were less than 1 mg/kg in all ditch
sediment samples. I Concentrations of total DDT ranged from o. 1
mg/kg (SD-4) to 77 mg/kg in OSD-27. Toxaphene ranged from not
detected in six of the samples to 40 mg/kg in SD-6. Copper, lead
and zinc concentrations were within the ranges indicated across the
Site. Copper ranged from not detected to 19.4 mg/kg in SD-19.
Lead ranged from n'ot detected to 90. 2 . mg/kg in 0SD-21. Zinc
concentrations ranged from not detected to 68.3 mg/kg at 0SD-26.
I 5.3.2 Phase 3 Ditch Sediment Samples
I In accordance with the RI/FS Work Plan, additional sediment depth
samples were collected from sample locations identified in Phase 2
as containing concerttrations of total BHC, total DDT and Toxaphene
at concentrations greater than 10 mg/kg. In Phase 3, ditch
sediments were collected from those locations at depths of one and
two feet below thei surface to assess the vertical extent of
contamination. In[ addition, samples were collected 50 feet
downgradient of af
1
fected areas. Samples were collected in
accordance with procedures outlined in the RI/FS Work Plan.
The Phase 3 sediment\analytical results are presented in Table 5-3.
Isomers of BHC, total DDT and toxaphene were the most prevalent
pesticides detected.] Of the 33 samples collected, nine samples had
total pesticide concentrations greater than 10 mg/kg. The samples
and the detected cohcentrations are listed on Table 5-4. Total
pesticide concentratlions ranged from approximately 12 mg/kg in SD-
1-1. 5 to approximately 145 mg/kg in SD-9-2.5 (Sample location SD-9-
1.5 was removed during the March-April 1991 removal. Reference
Figure 1-4 for loca~ion of SD-9).
Copper, lead and z in]c concentrations were within the ranges found
in background soils.[ Copper ranged from 1.1 mg/kg in OSD-42-05 to
17.5 mg/kg in SD-21-1.5. Lead ranged from 1.6 mg/kg in 0SD-27-2.5
to 202 mg/kg in SD-21-1.5. Zinc concentrations ranged from not
detected to 269 mg/kg in SD-21-1.5.
5.3.3 Phase 4 Ditch Sediment Samples
In order to assess whether contaminants had migrated vertically,
two, five and ten fbot samples were collected from four sample
locations SD-10, SD-~l, SD-12 and SD-14, which exhibited surface
pesticide concentrations greater than 500 mg/kg prior to the March-
April 1991 removal (Reference Figure 1-4).
Soil borings were djilled with hollow stem augers in accordance
5-2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
with the procedures outlined in the RI/FS Work Plan. Sample
collection was achieved with a large diameter (i.e., three-inch)
split spoon samplerlto allow recovery of a sufficient sample volume
for laboratory analysis in accordance with CLP criteria.
Decontamination ofl the augers and sampling equipment was in
accordance with the Work Plan procedures.
The samples were anllyzed for the Site specific parameters and the
results are presented in Table 5-5. The total pesticide
concentrations werel less than 10 mg/kg in each sample analyzed.
5-3
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
6.0 NATURE AND EXTENT OF CONTAMINATION
6.1 Ground Water
6.1.1 Pesticides
Pesticides were dete,cted in seven of the eighteen monitor wells at
the Site. Five of the monitor wells (MW-2S, MW-3S, MW-4S, MW-5S
and MW-6S) are shallow wells (uppermost aquifer) located within the
Site property boundaries. The other two monitor wells were located
off-Site: MW-l0S, a: shallow well, and MW-110, a well screened in
the second uppermost[ aquifer. Pesticides were not detected in the
upgradient shallow well (MW-lS) or the five other off-Site shallow
wells (MW-7S, MW-8s,[MW-9S, MW-12S or MW-13S). No pesticides were
detected in any of the on-Site deeper wells, including the three
second-aquifer monitor wells (MW-10, MW-40 and MW-60), the third
aquifer monitor well[ (PZ-1) and the former water supply well (WSW-
1). The areal dis~ribution of pesticides in ground water is
illustrated in Figures 3-11 and 3-13.
The BHC isomers (alJha-BHC, beta-BHC, delta-BHC, gamma-BHC) were.
detected at all se),en of the monitor wells where pesticides
occurred. Except for beta-BHC, the highest concentrations of BHC
isomers occurred at MW-6S (total BHC = 107 ug/1). MW-6S is located
west ( and generally dbwngradient) of the former warehouse locations
where pesticide-affected soils had been detected and removed. The
other four shallow mdnitor wells where pesticides were detected are
I generally located south (MW-4S, MW-5S and MW-l0S) or west (MW-2S
and MW-3S) of the forker pesticide-affected soil areas. The lowest
detected levels of pJsticides in the shallow ground water occurred
at MW-3S, located weJt-northwest of the former affected soil areas
and MW-6S. The Maximum Contaminant Level (MCL) for gamma-BHC (0.2
ug/1) was exceeded a~ MW-2S (2.8 ug/1), MW-3S (0.37 ug/1), MW-4S
(0.5 ug/1), MW-5S (4.6 ug/1), MW-6S (30 ug/1), and MW-110 (11
ug/ 1) . I
Toxaphene was detected at MW-2S (9.6 ug/1) and MW-4S (4.6 ug/1) at
levels exceeding the :primary drinking water standard for toxaphene
( 3 ug 11) . I
The apparent lateral extent of pesticide contamination in the
uppermost aquifer is !indicated by the lack of detectable pesticide
levels in the shallow[monitor wells to the north (MW-7S, MW-8S, and
MW-9S), to the west (MW-13S), and to the southwest (MW-12S) of the
Site. No pesticides[ were detected at the USGS observation well
(GS-02-3) located within 130 feet east of Aberdeen Municipal supply
well Number 4.
Detectable levels of pesticides occurred in shallow well MW-l0S
located approximately 120 feet south of the Site. The lateral
extent of pesticide contamination to the south and east of MW-l0S
is undetermined. No :pesticides were detected in shallow well MW-
12S, which is approxfmately 480 feet west of MW-l0S.
6-1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The vertical extent of pesticide contamination is limited to the
uppermost aquifer at the Site. No pesticides were detected in the
second aquifer bene~th the Site or in the monitor wells screened in
the third aquifer beneath the Site. Pesticides were detected off-
Site in the secbnd uppermost aquifer at MW-11D located
approximately 375 feet south of the Site.
The aquitard which lseparates the uppermost and second uppermost
aquifers at the Site is present at MW-11D. The aquitard thickness
decreases from ten f:eet thick beneath the Site to one foot thick at
MW-11D. However, the water level elevation at MW-11D indicates
that the aquitard remains an effective barrier to preventing a
• • I • hydraulic connection between the uppermost aquifer and the second
aquifer. I
There is no definitive evidence that the pesticides detected at MW-
11D represent Site riklated contamination. No migration pathway can
be postulated to the Site. In previous investigations (Reference
Table 1-4), pesticides were reported in a private domestic well
(Booth well) located! approximately 825 feet southeast (upgradient)
of MW-11D (Figure 175). In addition, the potentiometric contours-
of the second aquifer (Figure 3-7) indicate that ground water flow
in the vicinity of MW-11D (Reference Table 1-4) is northwestward
and there is little potential for contamination transport in the
second aquifer from the site to MW-11D.
Below are several conceptual models which were evaluated in an
attempt to determinJ whether or not pesticide occurrences at the
site are related tb pesticides detected at MW-11D. In each
hypothesis formulat~d below, however, a casual relationship could
I not be adequately developed.
1,
1. Hypothesis: site contamination in the uppermost aquifer
migrates to the second aquifer by leakage through the
uppermost aquit'ard in the vicinity of MW-11D.
Discussion: Wh[ile the aquitard thins to approximately one-
foot at MW-11D, I.the soils immediately beneath the aquitard 1;1re
unsaturated (Figure 3-4). Ground water at MW-11D is,
therefore, not! directly hydraulically connected to the
uppermost aquifer thereby demonstrating that the aquitard
ramains a competent barrier to vertical contaminant migration
at the site. I
Conclusion: Ground water at MW-11D is not directly
hydraulically cbnnected to the uppermost aquifer beneath the
site. I
2. Hypothesis: The uppermost aquitard thins out to the south of
MW-11D, allowing recharge to the second uppermost aquifer.
6-2
I
I
I
I
I
I
I
I
I
I
I
I
H
I
I
I
I
I
3 •
Discussion: Groundwater gradients in the uppermost and second
uppermost aquifer beneath the site are to the west and
northwest, resBectively. Well MW-llD is 300 feet south and
appears to be ~irectly side-gradient to the nearest shallow
well, MW-l0S. Based on the hydraulics of the second uppermost
aquifer, conta~ination indicated in MW-llD must originate to
the southeast (1i.e., upgradient) of MW-llD.
1 . C It . t' . . . Cone us1on: on amina ion in MW-llD appears to originate from
an upgradient Source.
Hypothesis: I Groundwater at MW-llD contains the same
pesticides as found in Site groundwater and, therefore, is
site-related. I
Discussion: While the BHC-isomers detected at MW-llD are the
same as those detected in on-site wells, the concentrations
are higher thanl at the nearest side-gradient wells, MW-4S and
MW-l0S. Since MW-llD is approximately 400 and 300 feet,
respectively, fhrther south of the former warehouse than MW-4S
and MW-6S, pesticide concentrations should have been lower at.
MW-llD if the s'ite was the source of contamination.
1 · I t · · 1 · Cone us1on: Con aminant concentration evels in MW-llD are
not consistent I with what would be expected from a plume
migrating from the Site.
A factor to be consi~ered in determining the source of pesticides
found in MW-llD is that the BHC-isomers were formulated for local
use and have been de'.tected as disparate locations in the Aberdeen
area. In prevous investigations (Table 1-4), BHC-isomers were
detected at a privat~ domestic well (Booth) located approximately
825 feet southeast fupgradient) of MW-llD (Figure 1-5). Further
support for the potential of an off-site source is the presence of
methoxychlor in MWJllD, which was not detected in any other
monitoring well.
Pesticides were not detected in the
beneath the site. I The preponderance
presence of pesticides at Mw-llD is due
second uppermost aquifer
of evidence is that the
to an upgradient, off-site
source. I
Pesticides were not detected in the third uppermost aquifer.
6.1.2 TCL Volatiles
Trichloroethene (TCE) was detected in the second uppermost aquifer
in two of the on-Site monitor wells (MW-4D and MW-6D). TCE was
also detected (south1east) upgradient of the Site in two off-Site
private domestic wells; the PMP well and the Allred well (Figure 1-
5). The highest TCE concentration occurred in the PMP well (360
ug/ 1). It should also be noted that the TCE concentrations
6-3
I
I
I
I
I
I
I
I
g
I
I
I
I
I
I
I
I
I
I
reported for the pr~vate wells may be higher than reported due to
potential volatization during sampling (Reference Section 3.6.1.2
for private well sampling procedures).
I TCE was not detected in the soils or in the shallow ground water at
the Site. Considering_ the absence of a potential source area at
the Site and the presence of trichloroethene in the off-Site
private wells located upgradient, it is apparent that the source of
the trichloroethenelis upgradient (east) of the Site.
6.1.3 TCL Semi-Volatiles
Semi-volat~le compohnds were detected in three shallow monitor
wells but at concentrations below the method detection limit of 10
ug/ 1. The occurrense of these compounds at a few monitor wells at
levels below the method detection limits did not warrant inclusion
of semi-volatiles ih the Phase 4, Step 2 ground water sampling. No
further action is war' ranted concerning semi-volatile constituents.
6.1.4 TAL Metals
Arsenic, barium, yadmium, chromium, lead, mercury, nickel,.
selenium, silver and zinc were either not detected or were below
the Federal Drinking, Water Criteria. The secondary drinking water
standard for iron (~00 ug/1) was exceeded in six wells including
both upgradient wells (MW-lS and MW-1D). Copper was detected iri
the on-site water supply well at a concentration of 1180 ug/1 which
is slightly above tne secondary MCL of 1000 ug/1.
Continued monitoring! of TAL metals was determined to be unwarranted
and no metals analyses were conducted in the Phase 4, Step 2 ground . ' water sampling event.
6.1.5 Field ParameJers
The specific condudtance in the shallow aquifer at upgradient
monitor well MW-ls \.as 20 umhos/cm. The other shallow monitor
wells indicated simillar or slightly elevated specific conductance
' levels (14 to 84 umhos/cm) except at MW-2S (1,080 umhos/cm), MW-3S
(600 umhos/cm), and MW-6S (1,740 umhos/cm). The elevated specific
conductance values are in the vicinity of the former concrete tank
pad area. I
The specific conductance levels in the second aquifer at MW-4D and
MW-6D were both below the upgradient levels measured at MW-1D, MW-
14D and MW-15D. I
The pH values were variable across the Site in both the shallow
aquifer and second aquifer. Relative to the pH value of 5.8 in the
upgradient shallow monitor well MW-lS, the pH values were generally
lower in the other st/allow monitor wells except at MW-l0S ( 6. 9 std.
units). The lowest pH values were measured near the former
concrete tank pad area at MW-6S (3.8 std. units) and MW-2S (4.0
std. units).
6-4
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
g
I
I
6.2 Soils
Volatile and semi-volatile constituents (including TCE) were not
detected in concentrations above the detection limit in any soil
samples, including s'amples collected at the five and ten-foot depth
intervals. I
Pesticide concentrations in on-Site soils are generally less than
100 mg/kg. The exc~ptions are at SS-63 (150 mg/kg), SS-110 (190
mg/kg), SS-58-20S (290 mg/kg), and SS-73-5 (300 mg/kg). All
samples with the exception of SS-73-5 indicated the pesticide
concentrations in subsurface soils were not present or were below
10 mg/kg total pesti~cides. Through the extensive grid sampling of
surface soils and the depth sampling of subsurface soils, the
extent of pesticidelcontamination in soils has been defined.
Concentrations of copper and zinc in soils were within the ranges
indicated in the background soils. Lead concentrations were
elevated in surfaceisoils located adjacent to Highway 211. Depth
sampling at SS-82 indicated that the lead concentrations in the
surface soils are !not migrating vertically. Considering the
detection of lead in surface soils along the highway only, it is
apparent that the le1ad concentrations in surface soils are related·
to traffic along Highway 211.
6.3 Ditch Sedimentlsamples
I Ditches located on-Site convey stormwater runoff from Highway 211,
from the railroad artd from the Site to off-Site locations. After
the stormwater leaves the Site, it dissipates as it infiltrates.
Sediments are carried along with the stormwater and settle out as
they are transported.
I Total BHC, total DDT and toxaphene were detected in the ditch
sediments. BHC condentrations were detected at less than 1 mg/kg
in ditch sediments -I The highest concentration of total DDT was
detected at 77 mg/kg in OSD-27. Toxaphene was detected in the
highest concentration at SD-9-2.5 (130 mg/kg).
Concentrations of tdtal pesticides in off-Site sediments exceeded
10 mg/kg in six samp~es (OSD-21, OSD-24, OSD-27, OSD-28, OSD-29/30
and OSD-43). The c:oncentrations were less than 100 mg/kg total
pesticides in the off-Site soils.
The extent of contkmination of ditch sediments appears to be
limited horizontallylto areas immediately downgradient of the Site.
Vertical migration of constituents is limited to the upper two to
three feet of sediments in the ditches.
6.4 Air
Airborne particulates.were investigated in February, 1989 prior to
the initial soil re~oval. Airborne pesticide particulates were
found to be below action levels prior to removal of the
6-5
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
concentrated surface deposits. The action levels were based on the
Threshold Limit Value -Time Weighted Average (TLV/TWA) for gamma-
BHC of 0.5 mg/m3 • I There is no TLV/TWA for alpha-BHC (22). A
description of the sampling and analysis of airborne particulates
at the Site is provi1ded in Attachment B of the RI/FS Work Plan (1).
Existing conditions, as described in Section 6. 2 above, have
significantly lower!soil contaminant concentrations and therefore
could only produce lower results than those generated under
original Site condi tlions. Therefore, airborne particulates are not
considered a migration pathway at the site.
6-6
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
7.0 CONTAMINANT FATE AND TRANSPORT
This section diJcusses the environmental migration and
transformation of ]pesticides found at the Geigy Site. All
available and appropriate technical literature was utilized in this
section to maximize] the quantitative evaluation of migration and
transformation potential.
7.1 Summary of Sitl Conditions
d . d . I . . th . . As iscusse in previous sections, e chemical constituents of
concern at the Site hre pesticides. Other chemicals were not found
to be significant at the site and therefore are not discussed in
this section. Reviews of other detected chemicals are presented in
sections 3,4 and 5 and have been determined to be not significant
or are not associated with the Site, and therefore, are not
discussed in this section.
Specific pesticides kere selected for discussion based on detection
in both.the soil (inbluding sediment) and groundwater at the Geigy
Site. The pesticides discussed in this section are listed in Table
7-1: aldrin; alpha, beta, gamma, and delta isomers of benzene
hexachloride (BHC); DDT; DDE; DDD; dieldrin; endrin ketone; and,
toxaphene.
Environmental matrices with pesticides are primarily soil and
groundwater. Maximum soil and groundwater concentrations for Site
pesticides are pro,;,ided in Table 7-2. Current maximum soil . ' concentrations were found at the surface and up to 2 feet below the
ground surface. These concentrations are orders of magnitude lower
than original site conditions as a result of removal actions in
1989 and 1991. I
The BHC isomers are the primary pesticides that have been detected
in the groundwater. The maximum pesticide concentration found in
groundwater beneath the Site was 36 ug/1 alpha-BHC in monitoring
well MW-6S. The highest concentrations of pesticides in
groundwater were foui;id in the following wells, located primarily in
the vicinity of the former warehouse: MW-2S, MW-5S, MW-6S, and MW-
1hos. · d f [h · t · d · · f Te remain er o tis sec ion iscusses potential routes o
migration (Section 1.11), contaminant persistence (Section 7.2), and
finally a summary of! contaminant fate (Section 7.3).
7.2 Potential Routes of Migration
· 1 · ·t h I · t b d' 'd d · · For simp ici y, t e environmen can e ivi e into three matrices:
air, soil, and watkr. Each of these environmental matrices
contains gases, soli~s, and liquids. For example, soil contains
interstitial air sphces, solid particles such as minerals and
organic matter, and] water. All chemicals can migrate in the
environment. The amount or degree of migration or the limitation
of migration depend 'upon the chemical/physical properties, their
7-1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
persistence in the environment, and their participating in the
biota.
Chemicals released into the environment (e.g., pesticides) will
partition to each of the three environmental matrices, and within
each matrix, betweeri the gas, solid, and liquid phases. The degree
of partitioning between phases and environmental matrices depends
on chemical-specific parameters such as water solubility, vapor
pressure, and equillibrium partitioning coefficients (e.g., Koc).
In addition, envirohmental partitioning depends on site-specific
parameters such as soil type, precipitation, and groundwater flow
rate. · · d · I · f · f · t f · ' t' 'th Following is a iscussion o speci ic rou es o migra ion wi
respect to air, soi:U, and water. Included are chemical-and site-
specific factors th~t may influence migration at the Geigy Site.
' . ti' 7.2.1 Air Migra ion
Pesticides may migJate to the air either by volatilization or
through adsorption Ito particulate matter that becomes airborne
(fugitive dusts). Volatilization of pesticides may also occur from
fugitive dust while ~irborne. All the pesticides of concern can be
categorized as chlorinated organic types. As such, they are not
normally consideredlvolatile compounds. Nevertheless, all such
compounds have a cerltain volatility.
7.2.1.1 Volatilization
Volatilization from \water and wet soils is generally rapid and a
significant fate process for compounds with a Henry's law constant
greater than o.001latm-cu m/mole (Lyman et al., 1982). The low
vapor pressures and ~enry•s law constants (Table 7-1) for all Site
pesticides, except toxaphene, indicate that volatilization from
soil will be insigni~icant.
Toxaphene is the onl~ pesticide that has significant potential to
volatilize from soil]. The relatively high vapor pressure (0.2 to
0.4 mm Hg) for toxaphene compared to other pesticides indicates
that volatilization !from dry soil may occur to a limited degree.
Toxaphene has the lpotential to volatilize from wet soil as
indicated by its relatively high Henry's law constant (0.436 atm-cu
m/mole) . I
7.2.1.2 Fugitive Dust
Chlorinated organic\ pesticides may also be adsorbed to soil
particles and then be transported by fugitive dust. Pesticide
adsorption to soil is primarily a function of its Koc value and the
organic matter fraction of the soil. Higher Koc values or higher
organic fractions re~ult in more adsorption potential between the
soil and the pesticide.
7-2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
The high Koc values (Table 7-1) and organic content of the soil
(approximately 0. 00:1 organic carbon fraction) indicate that the
pesticides currentl¥ at the site will strongly adsorb to soil.
Therefore, if soil becomes airborne as fugitive dust, it is likely
that adsorbed pesticides will also become airborne. While
airborne, volatilization of the pesticide from its substrate (i.e.,
particulate matter) will not be significant, with the exception of
toxaphene.
The fate of the portion of the chemicals which remain adsorbed
(i.e., not volatized) will be dependent on the fate of the airborne
soil. Compounds on airborne soil may return to the ground either
by dry deposition (i.e., gravity) or wet deposition (i.e.,
rainfall).
The higher concentrations of pesticides (i.e., 100 mg/kg gamma-BHC
and 500 mg/kg toxpahene) have been removed and replaced with clean
fill. The potential! for fugitive emissions is minimal, considering
current levels at the Site.
7.2.2 Soil Migrltion (Surface Run-off and Vadose Zone)
Prior to removal lctions, relatively high concentrations of
pesticides were fourtd on or in the soil, primarily a silty sand, at
the Site. Data disbussed in Section 4 indicate that in spite of
relatively high concentrations of pesticides in the surface soil,
pesticides did not migrate to any significant extent. This could
be predicted and · eixplained by examining the physical/chemical
properties in Tabl~ 7-1. Following is a discussion of the
potential for pesticides to migrate with surface soil and to
migrate through vadose zone soils.
7.2.2.1 Surface sJi1 Runoff
As discussed above, the pesticides will tend to adsorb to organic
matter and clay in the surface soil. Therefore, surface runoff
that transports soil particles would also transport adsorbed
pesticides. Howevgr, as discussed in Sections 2. 4. 3 and 5. 0,
surface runoff at I the Site is limited areally by the high
permeability of Site soils; that is, stormwater runoff is quickly
adsorbed into the sdils instead of flowing long distance or being
I spread over large areas.
Drainage ditches atlthe Site are dry except during storm events.
During rainfall, Site soils may be transported to the ditches as
runoff and become sgdiment since the water is rapidly absorbed by
the soil. Areally-limited migration of pesticides to ditch
sediments has occuried. Maximum concentrations of pesticides are
found in the upper two feet of ditch sediment (Section 5).
7-3
I
I
I
I
I
I
I
I
I
I
I
I
I
I
1.
I
I
I
I
7.2.2.2 Migration Through Vadose Zone Soil
At least three natural mechanisms control the migration of
pesticides through
1
vadose zone (unsaturated zone) soil: gaseous
diffusion, bulk flow with a carrier, and adsorption to solid
surfaces. I
Gaseous diffusion is a function of a compound's vapor pressure (dry
soils) and Henry's law constant (moist soils). Toxaphene, with a
relatively high vapor pressure and high Henry's law constant (Table
7-1) has the potential to migrate in the vapor phase. Significant
amounts of toxaphene that were present in the vadose zone may have
migrated to the soi] surface and then into the atmosphere. The low
vapor pressures an1d low Henry's law constants for the other
pesticides indicate that gaseous diffusion would not be a
significant transpdrt mechanism in the interstitial air spaces
within soil. I
Bulk flow with a carrier is limited at the Site to percolation of
precipitation into the soil. The infiltrated water may transfer
pesticides downward :within the vadose zone. In spite of relatively
high annual precipitation (approximately 45 inches per year),
pesticide mobility through the vadose zone is greatly slowed by the
third factor that irifluences contaminant migration in the vadose
zone: equilibrium adsorption coefficients.
An equilibrium adsoJption coefficient (Kd) can be approximated for
pesticides in the aqheous phase of soil by multiplying the fraction
of organic carbon (ifoc; mass per mass basis) by the pesticide's
equilibrium organiclcarbon partitioning coefficient (Koc):
Kd (pesticide)= Koc (pesticide) x foe (soil).
The soil at the Site has an organic carbon fraction of
approximately 0.001 (Table 4-8). Estimated Kd values are provided
in Table 7-2. Actual Kd values for Site pesticides will most
likely be higher sin1ce Kd, primarily a function of organic content
of the soil and the Koc of the pesticide, is also a function of the
soil texture. Site soil is primarily a silty sand that will
contain significantladsorption sites. Adsorption sites on silt
particles will contribute to a higher Kd value for a pesticide than
if only organic content is considered.
The high Koc valuels (and resultant Kd values) and low water
solubilities indicat1e that dissolution and transport of pesticides
by infiltration through the soil would be minimal. This is
supported by examining the depth profiles of maximum concentrations
versus depth for Site pesticides (Table 7-2).
However, low concent~ations (ug/1) of pesticides were found in the
groundwater (Table 7r2). These data indicate that in spite of high
Koc values for Site pesticides, limited migration through the
vadose zone has occurred. Quantitative predictions about the
7-4
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
g
I
I
I
future transport of ti he remaining, low levels of pesticide residues
in the soil vadose zone to the groundwater will be made using
unsaturated transpqrt modeling in the Feasibility Study (FS).
Qualitative predictions based on chemical and physical properties
of the pesticides and the soil, as discussed above, indicate that
transport of pesticides through the vadose zone will be slow.
I 7.2.3 Ground Water Migration
Following is a di~cussion of (1) migration of pesticides to
groundwater and (2) migration within groundwater.
7.2.3.1 Migration to Ground Water
Pesticides may migrate from a source area, through the vadose zone,
and then to groundwater. Data indicate that pesticides at the Site
have migrated to grdundwater (Table 7-2). The BHC isomers are the
primary pesticides !that have migrated to the groundwater. As
discussed., the maximum pesticide concentration found in groundwater
beneath the Site is ~6 ug/1 of alpha-BHC in monitoring well MW-6S.
Maximum concentrat~ons in groundwater were limited to four
monitoring wells (MW-2S, MW-5S, MW-6S, and MW-l0S), indicating a
limited areal extent of contamination.
7.2.3.2 Migration in Ground Water
One method to approximate the potential for a pesticide to migrate
through the groundwdter is the retardation coefficient (Rd). Rd
can be estimated usilng the following equation:
Rd = 1 + Kd X (d/n) 11= Vw/Vc
where:
Rd is the retardation coefficient (dimensionless)
Kd is the 'equilibrium distribution coefficient (ml/g)
dis the sbil bulk density (g/ml)
n is the elffective soil porosity (decimal fraction)
Vw is the bulk groundwater rate (ft/year)
Ve is the bontaminant rate (ft/year) for
surfibial/intermediate aquifers
The Rd provides an ebtimate for attenuation of a pesticide in the
groundwater via advective flow. The Rd also estimates the velocity
of a pesticide relative to the velocity of the groundwater:
Rd values clos~ to one indicate little tendency to bind to
soils and hencelthe contaminant moves freely with groundwater
Larger Rd values indicate a greater tendency for a contaminant
to bind to soil and hence slower transport with groundwater.
Table 7-3 shows Rd values for the pesticides at the Site. Using Kd
values from Table 7-1 and assuming a soil bulk density of 1.5 g/ml
and an effective porosity of 0.38, Rd values range from 5 for
7-5
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
ganuna-BHC and toxaphene to 17,000 for DDE. These Rd values
indicate that pesticides will not be very mobile in the
groundwater. Grourid water data presented in Section 3 indicate
limited lateral extent of groundwater contamination. More detailed
groundwater modeling will be conducted in the FS.
I 7.3 Environmental Transformations
I Environmental transformation of chlorinated organic pesticides in
environmental media [can occur by biological and chemical processes.
The overall transformation of a pesticide in a specific
environmental medial (e.g. surficial soils) may be a factor of
several transformation processes.
A summary of transfolmation processes for the pesticides of concern
are provided in Table 7-4. The terms "significant" and
"insignificant" are[ used in the table for identifying important
transformation processes for each pesticide. These terms are not
being used for comparing one pesticide to another but for
identifying dominant transformation processes for each pesticide.
7.3.1 Biological
Transformations of organic chemicals in the environment can occur
through the action I of microorganisms attached to the soil or
existing in surface and ground water. Bacteria are ubiquitous in
subsurface soils. Even at low numbers, subsurface microbes can
possess adequate metabolic activity to significantly reduce the
levels of organic compounds migrating through the subsurface soil
profiles. I
Biodegradation occur,ring in oxygen rich environments are referred
to as aerobic while[transformations in the absence of oxygen are
referred to as anaerobic. The biodegradation requirements for
oxygen are pesticide\specific. Some pesticides will biodegrade in
both oxygen-rich and oxygen-free environments; however, the rates
of degradation in eabh environment are typically very dissimilar.
Discussions follow I for the Site pesticides excluding those
classified as "insignificant", in Table 7-4 with respect to
biodegradation. I
Lichtenstein et al. (11959) performed an incubation of aldrin for 56
days at 6, 26, and 46 degrees C and observed 84, 56, and 14% of the
initial amount reco\.rl erable. After 2 months incubation at 30
degrees c; 44, 58, and 33% of about 15 ppm of aldrin applied
remained in the Maahas, Luisiana, and Casiguran soils under upland
(80% water saturatioh), respectively. Lichtenstein et al. (1970)
treated aldrin to the! soil at 5 lb/acre from 1958-62. Dieldrin was
formed from aldrin in the soil and constituted 50 and 90% of the
aldrin plus dieldrin residues recovered in 1959 and 1963,
respectively, Although slow, biodegradation of aldrin in soil may
be significant.
7-6
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Fifteen years following the application of alpha-BHC to a sandy
loam soil in Nova lscotia, Canada, 4% of the applied alpha-BHC
remained in the soi11 (Stewart, 1971). Of this amount, about 92%
was found between 6-20 cm indicating minimal leaching (Stewart,
1971). Incubation bf aerobic and anaerobic soil suspensions for
three weeks resulted in disappearance of 11% to 26% of the added
compound, respectively (MacRae et al., 1984).
Gamma-BHC has been lfound to support the growth of microorganisms
isolated from loam~ sand. Chloride ion formation was noted in
these cultures. The extent of gamma-BHC biodegradation by these
pure cultures was nbt given (Tu, 1976). From moist aerated soil,
62% of the gamma-BHC applied was recovered. The loss of gamma-BHC
from submerged anaerobic soil was nearly quantitative with only 4%
of the applied gamma-BHC recoverable (Kohnen et al., 1975). Six . ' . weeks following treatment of soil, a number of chlorobenzene and ' chlorocyclohexene compounds were detected. The absence of these
products from sterilized soil treated with gamma-BHC was cited as
evidence that the gamma-BHC metabolites resulted from
biodegradation (Mathur et al., 1975).
I Incubation of aerobic and anaerobic soil suspensions of gamma-BHC
for three weeks resulted in the disappearance of o and 64% of the
applied gamma-BHC, respectively (MacRae et al., 1984). The result
was said to indicate that anaerobic degradation of ganima-BHC is
more extensive than ~erobic degradation (MacRae et al., 1984). One
anaerobic biodegradation product of gamma-BHC is alpha-BHC
' (Montgomery and Welkom, 1990).
DDT is biodegraded b~ microorganisms in water, sediments, and soils
(Johnson, 1976 and ~anborn et al., 1977). Biodegradation under
environmental condi~ions has been shown to be quite variable,
however, with a numrer of factors playing a role, especially the
presence of anaerobic conditions and high populations of the
required microorganisms (Johnson, 1976 and Sanborn et al., 1977).
significant degradaltion has been demonstrated in soils under
anaerobic conditions, while little or no degradation was observed
under aerobic conditions (Johnson, 1976; Sanborn et al., 1977; and
Pan et al., 1970). Reported half-lives for DDT in soils range from
2 years to greater than 15 years (Lichtenstein et al., 1959; Tu,
1976; Jury et al., 1983; and Stewart et al., 1983). No change in
DDT concentration was found in raw river water over a period of 8
weeks (Eichelberger let al., 1959).
The biotransformations of DDT and its derivatives DDD and ODE.has
been extensively studied in a number of biological systems. No
data are availabl~ to reliably assess the rate of DDT
transformation in water. Vast literature as well as the widespread
occurrence of DDT !clearly indicates that DDT is not readily
metabolized in water. Biotransformations of DDT occurs more
readily under anaerobic conditions than in aerobic systems;
transformations of DDT to DDE is favored in aerobic systems,
whereas DDD is the major metabolite in anaerobic environments
(Callahan, 1979).
7-7
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Aerobic biodegradation of toxaphene is limited. Half-lives in
soils may range from 1 to 14 years (HSDB, 1991). Anaerobic
biodegradation may be a significant transformation process (HSDB,
1991).
7.3.2 Chemical
The chemical transformation of an organic pesticide in a specific
environmental medial (e.g. air, water, and soil) at the Geigy Site
is primarily a function of photolysis and hydrolysis processes.
These processes ar~ defined and described for the pesticides of
concern in the follbwing sections.
7.3.2.1 Photolysis
Photolysis is the decomposition or chemical action due to the
action of light oli a substance. The rate of a photochemical
process is determined by the rate of light absorption and the yield
of the process. The net rate of photochemical transformations is
the sum of the rate$ of all direct and indirect processes. Direct
and indirect photop\:-ocesses can be described by first-order rate
expressions. I
Direct photolysis is due to the absorption of electromagnetic
energy by a compou1d. In this direct process, absorption of a
photon promotes a molecule from its ground state to a
electronically exci:i:ed state. The excited molecule then either
reacts to yield a photoproduct or decays to its ground state.
Indirect photolysjs, sometimes referred to as sensitized
photolysis, occurs iln the simultaneous presence of humic materials,
dissolved oxygen, artd sunlight. This combination often results in
an acceleration of the rate of transformation of organic compounds.
Indirect photolysis can be subdivided into two classes of
reactions. First, sensitized photolysis involves excitation of a
humic sensitizer by sunlight, followed by direct chemical
interaction between! the sensitizer and a compound. The second
class of indirect photolysis involves the formation of chemical
oxidants, primarily via the interaction of sunlight, humic
materials, and diss'olved oxygen. The primary oxidants known to
occur in natural \<iaters are hydroxyl and peroxy radicals and
singlet oxygen. I
Photolysis transformations occur in the atmosphere, water, and
soil. For the purpose of this investigations, photolysis occurring
in the atmosphere I and surface water is not important. The
atmosphere serves a~ a removal pathway from the Site and there are
no surface waters in the vicinity of the Site. Photolysis in
surficial soils as !discussed above is often accelerated by the
presence of humic materials in the surficial soils. Photolysis
involving humic materials occur primarily via indirect processes.
Photolysis in soil occurs predominantly in the uppermost layer of
soil which is in corttact with sensitizers and oxidizers, products
of indirect photoly$is.
7-8
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
In reference to Table 7-4, pesticides in soils undergoing indirect
photolysis include I ODD and toxaphene. Callahan et al. (1979)
reported that indirect photolysis of DOD may be substantial.
Indirect photolysis\ of toxaphene with photochemically produced
hydroxyl radicals was observed by Durkin et al. (1979). Half-life
of approximately 4: to 5 days for the indirect photolysis of
toxaphene was estimated.
Photolysis, howeverl will be significant only on the upper surface
of soil that is exposed to sunlight. Since the significant
contaminated soils lhas been excavated, photolysis will not be a
significant transformation process at the Site.
7.3.2.2 Hydrolysis
Hydrolysis is a decomposition reaction caused by chemical contact
with water. The chemical of concern reacts with water or with the
hydronium or hydro~ide ions associated with water. The typical
reaction usually r~sults in the introduction of a hydroxyl group
into the chemical compound with the loss of a functional group,
typically a halide !(e.g., chlorine). In reference to Table 7-4,
the only pesticide that may be subject to significant hydrolysis is
gamma-BHC.
Gamma-BHC rel.eased to acidic or neutral water is not expected to
hydrolyze significantly, but in basic water, significant hydrolysis
may occur with a h~lf-life of 95 hours at pH 9.3. The hydrolysis
half-lives are 936 land 433 hours at pH of 5 and 7, respectively.
The reactions were conducted at 25 degrees c (Saleh et al., 1982).
pH values for Site igroundwater range from 4 to 7.
7.4 Summary of Contaminant Fate
I Essentially, migration and natural transformation of the Site
pesticides will bel limited. Toxaphene appears to be the most
environmentally mobile pesticide .found at the Site since it will
volatilize to and degrade in the atmosphere and will anaerobically
biodegrade in soil I and groundwater. The other pesticides will
migrate and degrade slowly, such that current concentrations of
pesticides in Site soil and groundwater will slowly decrease
primarily by dilutlion in soil and groundwater· and to a lesser
extent through trahsformation. Potential transformations of Site
pesticides are sumnlarized in Table 7-4.
7-9
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
8.0
1.
2.
3.
4.
5.
6.
SUMMARY AND CONCLUSIONS
A remedial !investigation (RI) was conducted at the Geigy
Chemical Corporation Site by three PRP's (Olin Corporation,
CIBA-GEIGY :corporation and Kaiser Aluminum and Chemical
Corporation) in accordance with an AOC signed in December
1988. I
Two removal! actions (February 1989 \ October 1989 and
March-Aprill1991) were conducted during the time of the RI.
The removals greatly reduced the volume and concentration
of contamihants remaining in on-site soils, thereby
minimizing the potential for contaminant migration.
The hydrogJologic investigation at the Site identified
three aquif;ers beneath the site. The uppermost aquifer
extends from the surface to a depth of approximately 63
feet at the eastern end of the site and thins with the
topographiclslope to approximately 40 feet near the western
end of the site. Ground water within the uppermost aquifer
occurs under water table conditions. Saturated soils were
encountered! at approximate depths of 35 to 45 feet below
ground level.
The limitedlsaturated thickness of the uppermost aquifer in
the vicinity of the Site makes it an unlikely source for
usable ground water due to low yields.
Ground watJr flow in the uppermost aquifer appears to be
controlled jby recharge areas located at the eastern and
western ends of the Site and by moderate topographic slopes
on the northern and southern sides of the Site.
Potentiometlric data from the shallow monitor wells indicate
ground wate~ flow from the eastern and western portions of
the Site me~t in an elongated zone of convergence. East of
I the convergence zone, ground water flows west and northwest
with a hydraulic gradient of approximately 0.026 ft/ft.
West of the convergence zone, ground water flow is
predominan~ly to the east-southeast with a hydraulic
gradient of 0.017 ft/ft.
The uppermdst aquifer beneath the Site is underlain by the
uppermost donfining layer. The uppermost confining layer
is continuous across the Site with an indicated laboratory
permeability on the order of 10·8 cm/sec. The thickness of
the upperm9st confining layer beneath the Site ranges from
6 to 20 feet. No hydraulic connection between the
uppermost aquifer and the second uppermost aquifer was
indicated.
8-1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
7.
8.
9.
10.
11.
12.
13.
14.
15.
The second uppermost aquifer beneath the Site extends from
the base of the uppermost confining layer and is
approximately 40 feet thick. Ground water in the second
aquifer occurs at a depth of approximately 15 feet below
the base of lthe uppermost confining layer. The unconfined
conditions indicated in the second uppermost aquifer may be
due to it~ proximity to the outcrop of the aquifer
approximately 2,000-3,0000 feet west of the Site or may be
the result iof dewatering due to ground water withdrawal
from this aquifer in the region.
Ground wateJ elevation data indicate the ground water flow
direction i:n the second uppermost aquifer is generally
northwesterly. The average hydraulic gradient for the
second aquifer was calculated to be 0.004 ft/ft.
The second laquifer is underlain by the second uppermost
confining l~yer which was determined to be approximately 10
to 13 feet thick beneath the Site.
The third ulppermost aquifer at the Site extends from the
base of the second confining layer to approximately 60
feet. Grohnd water in the third aquifer occurs under
confined conditions. The single monitor well screened in
the third aquifer did not allow for determination of flow
direction or hydraulic gradient.
t . t'I . d' t d . h . Con amina ion in ica e int e uppermost aquifer beneath
the Site wJs limited to the pesticide constituents. No
volatile constituents, including TCE, or semi-volatile
constituents were detected in the uppermost aquifer.
Pesticide clntamination in the shallow aquifer is migrating
toward the [ center of the Site, away from the municipal
wells, due to the convergence of ground water flow from the
east and west. Pesticides were not detected in the shallow
USGS well l(GS-02-3) located 130 feet east of Aberdeen
Municipal Supply Well Number 4.
Pesticides !were not detected in off-Site shallow wells
located to the north (MW-7S, MW-BS and MW-9S), to the west
(MW-13S and USGS-02-3), or to the southwest (MW-12S) of the
Site.
Detectable levels of pesticides were indicated in shallow
well MW-l0S located approximately 120 feet south of the
:~:e~erticjl extent of pesticide contamination is limited
to the uppermost aquifer beneath the site. No pesticides
were detected in the second aquifer or the third aquifer
beneath the Site.
8-2
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
16.
17.
18.
19.
20.
21.
22.
23.
Pesticides were detected off-Site in the second uppermost
aquifer at MW-11D located approximately 375 feet south of
the Site. The aquitard which separates the uppermost and
second uppermost aquifer beneath the Site is present at MW-
11D. The water level elevation at MW-11D indicates that
the aquitard remains an effective barrier to preventing a
hydraulic connection between the uppermost and second
uppermost aquifers.
Previous inlestigations conducted by EPA of private wells
in the area indicated the presence of· pesticides in a
private domestic well (Booth well) located upgradient
(southeast)! of MW-11D. Potentiometric contours of the
second uppermost aquifer also indicate that ground water
flow in th~ vicinity of MW-11D is northwestward and there
is little pbtential for contaminant transport in the second
aquifer from the Site to MW-11D.
TrichloroeJhene (TCE) was detected in the second uppermost
aquifer in I two on-Site monitor wells (MW-6D and MW-4D).
TCE was also detected upgradient (southeast) of the site in
two off-Site private domestic wells (i.e., PMP and Allred).
TCE was not detected in the soils or shallow ground water
at the Site. Given the absence of a potential source at
the Site, and the presence of TCE in upgradient wells, it
• I • ' is apparent that the source of TCE is upgradient from the
Site. I
The lead concentration in the monitor wells was below the
MCL. I
Volatile and semi-volatile constituents were not detected
in concent!rations above the detection limit in any soil
samples.
Pesticide concentrations in on-Site soils are generally
less than 100 mg/kg. Four samples had concentrations
greater than 100 mg/kg, with the highest concentration of
I 300 mg/kg at SS-73-5.
All soil skmples, with the exception of SS-73-5, indicated
pesticide !concentrations in subsurface soils were not
present or/ were below 10 mg/kg total pesticides.
Concentrations of copper and zinc in on-Site soils were
within the1 ranges indicated in the background soils. Lead
concentrations were elevated in surface soils located
adjacent to Highway 211. Depth sampling at SS-82 (located
adjacent tb the highway) indicated that lead concentrations
in the sur!face soils are not migrating vertically. Lead is
believed to be associated with highway traffic.
8-3
I
I
I
I
I
I
I
I
I
I
I
I
0
I
I
I
24.
25.
Total BHC, 1total DDT and toxaphene were detected in the
ditch sediments. BHC concentrations were detected at less
than 1 mg/kg in ditch sediments. The highest concentration
of total DDT was detected in off-Site sediment OSD-27 at 77
mg/kg. Toxaphene was detected in the highest concentration
at SD-9-2.51 (130 mg/kg).
Airborne pesticide particulates were found to be below
action levels (i.e., TLV /TWA) prior to removal of the
concentrat~d surface deposits. The removal actions
conducted at the Site have further reduced the potential
sources of !airborne particulates at the Site. Therefore,
airborne particulates are not considered a migration
pathway at the Site.
8-4
I
I
I
(1)
I
I (2)
I
(3)
I (4)
I ( 5)
I (6)
( 7)
I
I ( 8)
I ( 9)
0
g (10)
I
I ( 11)
I
I (12)
I
References
ERM-Southeast, November 1989; Remedial Investigation/
Feasib1ility Study Work Plan, Geigy Chemical
corpor1ation Site.
ERM-sJutheast, April 1990; Project Operations Plan,
Geigy /Chemical Corporation Site.
ERM-Southeast, May 1989; Field Activities Report,
InitiJl Soil Removal; and, ERM-Southeast, May 1990;
Phase/2 of Initial Soil Removal.
ERM-Southeast, August 1990; Warehouse Removal Work
Plan I
ERM-Southeast, September 1990; Work Plan for Soils
Removal Associated with the Warehouse and Railroad
Spur.I
Olin Corporation, March-April, 1991; Removal Report
NUS Corporation Superfund Division, March 1988;
Samp]ing Investigation Report, Geigy Chemical
Corpdration site.
SchiJf, R.G., 1961, Geology and Groundwater Resources
of ttie Fayetteville Area; Ground Water Bulletin No. 3,
North Carolina Department of Water Resources, Division
I of Ground water, 99p.
Winnir, M. and Coble, R. 1989, Hydrogeologic Framework
of the North Carolina Coastal Plain Aquifer System;
u.s.f Geologic Survey Open-File Report 87-690, United
~~atrs Geological Survey, Raleigh, North Carolina, 155
Giese, G.L., Eimers, J .L. and Coble , R.W. 1991.
SimJlation of Ground Water Flow in the Coastal Plain
Agui!fer System of North Carolina. United States
Geological Survey Open File Report 90-372, United
States Geological Survey, Raleigh, North Carolina, 178
p. I
North Carolina Department of Natural Resources and
Community Development, Office of Water Resources,
1980, Groundwater Resources of the Southern Pines area
-Af supplement to the Sand Hills capacity use study,
41 p.
Sir~ine, May 1991; Addendum to the RI/FS Work Plan
I
I
I
I
I
I
I
I
I
u
I
I
I
I
I
I
I
I
I
(13)
(14)
(15)
(16)
(17)
(18)
(19)
( 2 0)
( 21)
(22)
(23)
Coble, Ron
Hydrologist,
I
w., 1991, personal communication,
United States Geological Survey, Raleigh,
NC, 27607.
Toth, H., 1962, A Theory of Groundwater Motion in
Small Drainage Basins in Central Alberta, Canada;
Journal of Geophysical Research. Vol, 67, No. 11, pp.
4375-4387.
Toth, /J., 1963, A theoretical Analysis of Groundwater
Flow in Small Drainage Basins: Journal of Geophysical
I Research. Vol. 68, No. 16, pp. 4795-4810.
Corre~pondence from the Geigy Chemical Corporation
Site ;PRPs to the USEPA Regional Program Manager:
May J5, 1991 Revisions to deep borehole and surface
casing sizes.
June 4, 1991
June 27, 1991
Freeze, R.
Groundwater.
Jersey. 604
I 40 tFR 141.12
56 'FR 3526
Completion of MW-llD as a deep well.
Use of Volclay Pure Gold grout as an
annular sealant in deep wells.
Elimination of sediment traps in
shallow wells as needed.
Reduction
intervals
MW-14D.
of split spoon ample
to 5 foot centers for Well
Allen and Cherry, John
Prentice-Hall, Englewood
p.
A. 1979.
Cliffs, New
40 CFR 141 and 40 CFR 143
Bouwer, H. 1989. Bouwer and Rice slug test -an
update. Ground Water. v. 27, pp. 304-309.
Amiri can Conference of Governmental Industrial
Hygienists. TLVs, Threshold Limit Value and Biological
Exposure Indices for 1988-1989. Cincinnati, OH, 1988.
I d . Bouwer, H. an Rice, R.C. 1976. A slug test for
deitermining hydraulic conductivity of unconfined
aquifers with completely or partially penetrating
wells. Water Resources Research. v. 12, pp. 423-428.
I
I
I
I
I
I
n
I
I
I
I
I
I
I
I
I
I
I
I
Chapter 7
Callahan, Water-Rel Environ Fate Priority Pollut Vol
I, 197/9 25-13
Durkin, PR et al; Reviews of the Env. Effects of
Pollutants: x. Toxaphene p. 8-1 USEPA-600/1-79-044
(1979)
I Eicheiberger JW, Lichtenberg JJ; Environ Sci Technol
5. I
541-4 (1971)
I Harris CR, Miles JRW; Pesticide Residues in the Great
Lakes Region of Canada, Residue Reviews, Residue of
Pesticides and Other Contaminants in the Total
Environment (1975)
I Johnson RE; Res Rev. 61: 1-28 (1976) I Jur~ WA et al: Hazard Assessment of Chemicals, Saxena
Jed.2: 1-43 (1983).
I Kohne R et al:
22316 (1975).
Env Qual Safety Suppl Vol. III pp.
Lichtenstien EP, Schults KR; J Econ Entom 52: 124-31
( 19'59)
Lidhtenstein EP et al:
(1984)
J Agr Food Chem 18: 100-6
LJan, W.J. et al, Handbook of Chemical Property
Estimation Methods (1982).
Mabrae IC et al; Soi: Biol Boichem 16: 285-6 (1984).
Mjthur SP, Saha JG; Soil Sci 120:301-7
MJnzie CM, Metabolish of Pesticide, An Update Special
Scientific Report Wildlife No. 184 (1974).
I
Miles JRW et al: J Econ Entomol 62: 1334-8 (1969)
I Pan JF et al; Soil Sci 110: 306-12 (1970)
I Salem F.Y. et al; env. Toxicol Chem 1: 289-97 (1982)
I . 9anborn FR et al; The Degradation of Selected
Pesticides in Soil: A Review of Published Literature, pp. 616 USEPA-600/9-77-022 (1977).
I Stewart DKR, Chishol D, Can J. Soil Sci 61: 379-83
(1971).
Tu Cm, Miles JRW; Res Rev 64: 17-65 (1976).