PB97-963128
EPA/541/R-97/082
January 1998
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Teledyne Wah Chang
Albany, OR
10/8/1996
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TELEDYNE WAH CHANG ALBANY SUPERFUND SITE
ALBANY. OREGON
EXPLANATION OF SIGNIFICANT DIFFERENCES
From the June 10,1994 ROD For Final Remedial Action Of Groundwater and
Sediments Operable Unit
1.0 Introduction
1.1 Site Name and Location
Teledyne Wan Chang Albany
Millersburg, Oregon
1.2 Lead and Support Agencies
The Environmental Protection Agency (EPA) is the Lead agency on this site. The
Oregon Department of Environmental Quality (DEQ) is the Support Agency on this
site.
1.3 Explanation of Significant Difference
This document addresses significant change to the Groundwater and Sediments
Remedy described in the Final Remedial Action of Groundwater and Sediments
Operable Unit, Teledyne Wan Chang Albany. June 10,1994. The document
provides an Explanation of Significant Differences'as required under Section 117c
of CERCLA, and the National Contingency Plan (NCP) 40 C.F.R. §300.435(c)(2)(l).
1.4 Circumstances Leading to the Changes to the ROD
During Consent Decree negotiations for performance of the remedy, EPA and
Teledyne developed a Scope of Work-for performance of the remedial action. In
the development of that document Teledyne petitioned EPA to make the
modifications to the perimeter containment requirements of the groundwater. ROD
(described in Section 5). The rationale for the perimeter changes is based on
groundwater data collected subsequent to the Rl/FS. The additional changes are
the logical outgrowth of translating ROD requirements into an implementable
Scope of Work based on the newly available data.
TELEDYNE WAH CHANG ALBANY SUPERFUND STTE ESO PAGE i OF 13
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1.5 Administrative Record and Public Comment Period •
This Explanation of Significant Differences will become part of the Administrative
Record File for the site. The record is available in the EPA Region 10 Records
Center located at 1200 6th Avenue. Seattle, Washington and at the information
repository located at the Albany Public Library in Albany. Oregon.
This Explanation of Significant Differences is being made available for public
comment concurrently with the public comment period on the Consent Decree.
After evaluating the public comments, the ESD may be modified based on the
comments received.
1.6 Site Background
Site Information: • • .
The Teledyne Wan Chang Albany (TWC) site is located in Millersburg. Oregon.
adjacent to. the city of Albany. The facility covers approximately 225 acres near the
Willamette River. The TWC facility is divided into a 110-acre main plant area and
a 115-acre Farm Ponds area (Figure 1).
TWC is an active operating facility which primarily manufactures zirconium metal.
The manufacturing operation consists of numerous production facilities used for the
extraction and refining of zirconium and hafnium metals from zircon sands, with a
small amount of tantalum, columbium, titanium and vanadium metals also being
produced. The plant also has a number of waste treatment and storage facilities
and several on-site pondsthat were, t^r presently are. being used for the storage of
liquid and solid wastes.. ....', '_' :
The processing of the zircon sands generates sludge, waste water, residues and
gases as by-products; Contaminants of concern at the site include radionudides.
metals, polychlorinated biphenyls (PGBs), methyl isobuty! ketone (MIBK), and
chlorinated organic solvents such as 1,1,1-trichioroethane, carbon tetrachloride,
and tetrachloroethylene. .
Until 1978, the sludges produced from various waste water treatment processes
were stored in on-site ponds. The ponds included the Lower River Solids Pond
(LRSP) and Schmidt Lake which are located west of the Main Plant hear the banks
of the Willamette River. Chlorinator residues and magnesium chloride from the
plant process were stored in stockpiles along the eastern edge of the LRSP.
In 1978, process changes resulted in low-level radioactive materials being more
concentrated in the chtorinator residues. These residues are now disposed in a
low-level radioactive waste disposal facility in Hanford. Washington.
TELEOYNE WAH CHANG ALBANY SUPERFUNO SITE ESO PAGE 2 OF 13
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Past Cleanup Actions:
Because of concerns regarding the ponds being a possible source of groundwater
contamination, the site-was listed on the Superfund National Priorities List in
December 1982. The National Priorities List is a list of sites which are targeted for
further study and possible cleanup under Superfund authority.
In February 1991, EPA ordered TA/VC to clean up the sludges in the LRSP and
Schmidt Lake. Under the Order. TWC submitted the necessary work plans to EPA
and DEQ for review and approval.
After completion of the investigation, under an EPA order, TWC began the cleanup
of the sludges in June 1991. Approximately 100,000 cubic yards of sludge were
partially solidified with cement for easier handling. The solidified sludge was
placed in the Finley Buttes Landfill in Boardman. Oregon. Transportation of the
sludges was completed in November. 1991. TWC is currently monitoring the
monocell to ensure its effectiveness in containing the waste and protecting human
health and the environmenL The monocell monitoring data is submitted to EPA for
review.
In 1992. TWC conducted additional field investigations in and around Schmidt
Lake. These field investigations confirmed the presence of materials containing
zircon sands with moderate levels;of thorium and uranium.. In December 1992,
2016 cubic yards of materials were removed from Schmidt. Lake and transported to
an off-site low-level radioactive waste facility. .
Summary of Remedial Investigation: .
The RI/FS, completed by TWC, presents results of the site-wide field
investigations.
•
Groundwater Contamination
Groundwater contamination beneath the Main Plant is contaminated with volatile
• organic compounds (VOCs), ammonium, metals, RGBs, and low levels of
radionudides. Specific VOCs include: perchloroethene (PCE), trichloroethene
(TCE), 1.2-dichloroethane(1,2-pCA). 1,t-dichloroethene(1.1-OCE). and vinyl
chloride. Eight wells in the Main Plant had detectable concentrations of vinyl
chloride ranging from. 10 parts per billion (ppb) to 50 ppb. Some of the main areas
of groundwater contamination include the areas below the Feed Makeup Building
(metals and radionudides), the chemical unloading area (VOCs), and the Spill
Treatment Plant (ammonium and VOCs).
TELEOYNE WAH CHANG ALBANY SUPERFUND SITE ESO PAGE 4 OF 13
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Soil Contamination: -
A number of locations in the Main Plant area were found to have contaminants in
soils:
Soils in the Extraction Area are contaminated with semi-volatile organic
compounds, polychlorinated biphenyls polyaromatic hydrocarbons, and
radionuclides. Areas of identified soil contamination include the chemical
unloading area (semi-volatile organic compounds. PCBs, PAHs and
radionuclides), and the V2 Pond (radionuclides).
The fill material along Truax Creek's northern bank, known as Truax Fill.
contains undocumented quantities of construction debris and other solid
wastes that were placed in the fill from 1958 to 1978. Contamination in
Truax Fill includes radionuclides, PAHs, PCBs, and metals.
Soil sampling conducted in a portion of the Solids Area near the former
Chlorinator Residue Pile revealed the presence of barium sulfate and
residual chlorinator solids in the area.
PCBs were detected in soil samples taken during the Rl from the slopes
along Truax and Murder Creeks.
Within the Farm Ponds Area, the soil amendment area is a 47.8-acre agricultural
tract located directly north of the Farm Ponds (Figure 1). In 1976 TWC placed
solids from their wastewater treatment plant in this area to be used experimentally
as a soil amendment The solids were similar in composition to that of the LRSP
and Schmidt Lake. Surface.soil samples taken from the soil .amendment area
during the Rl contained PCBs, SVOCs, and radionuclides.
Sediment Contamination
PCBs were detected in sediment samples throughout the Surface Water Remedial
Sector. PCBs. SVOCs. and radionuclides were detected in sediments in Truax
Creek,
2.0 Description of the Remedy in the ROD
The Record of Decision for Final Remedial Action of Groundwater and Sediments
Operable Unit. June 10.1994 called for the following actions:
For Contaminated Groundwater.
Remediation of groundwater via groundwater extraction in the Feed
Makeup area and at areas on Site where contaminant concentrations
exceed lifetime cancer risk levels of 10"* and/or substantially exceed
noncancer HI of 1 for worker exposure. Extraction shall continue until
TELEOYN6 WAH CHANG ALBANY SUPERFUNO STTE ESO PAGE 5 OF 13
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contaminant concentrations in groundwater throughout the Site are
reduced to below SDWA MCLs, non-zero MCLGs. or cancer risk
levels of K)"6 and noncancer risk HI < 1 for worker exposure, or until
EPA in consultation with DEQ determines that continued groundwater
extraction would not be expected to result in additional cost effective
reduction in contaminant concentrations at the Site. Contaminated
groundwater in exceedance of SDWA MCLs. non-zero MCLs. or
cancer risk levels of 10* and noncancer risk HI > 1 for residential use
shall be prevented from migrating off the plant site, or beyond the
current boundary of the groundwater contaminant plume at the Farm
Ponds Area. • ~
Discharge of extracted groundwater to Teledyne Wan Chang Albany's
wastewater treatment plant Pretreatment of groundwater to comply
with CWA requirements prior to discharge to the wastewater
treatment plant
Treatment or removal of subsurface source material near the Feed
Makeup Building on the main plant
For Contaminated Sediments:
Slope erosion protection consisting of a geotextile covered by riprap
placed along the banks of Truax Creek to prevent contaminated fill
material from entering the treek.
Removal of approximately 3,600 cubic yards of contaminated
sediments from the surface water .bodies adjacent to, or flowing
through the Site. Additional ecological •characterization prior to ..
removal to determine potential impacts of sediment removal to the
local ecosystem and to provide mechanisms to mitigate those .<' • -
impacts. .
Site-Wide Actions: •''.-..
Deed restrictions and institutional controls on land and groundwater
use for both the main plant and Farm Ponds area. The objective of
this component of the remedy is to ensure that the property and
groundwater are used only for purposes appropriate to the cleanup
levels achieved .
Environmental evaluations of currently uncharacterized potential
contaminant source areas, as needed to ensure achievement of
groundwater RAOs. The objective of this component of the remedy is
to ensure that contaminant source areas do not adversely impact the
remedy.
TELEDYNE WAH CHANG ALBANY SUPERFUNO StTE ESO PAGE 6 OF 13
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Long-term orvSite and off-Site groundwater, surface water, and
sediment monitoring which shall include at a minimum the monitoring
of on-Site wells which are in exceedance of MCLs and non-zero
MCLGs, cancer risk levels of 10*, and noncancer risk HI > 1 for
residential exposure.
Review of selected remedy at least once every five years to ensure
protection of human health and the environment
The Record of Decision for Final. Remedial Action for Surface and Subsurface Soil.
September 27, 1995 called for the following actions:
Excavation of material exceeding the gamma radiation action level of
20 urem/nour above background, measured at one meter above the
surface and averaged over 100 square meters (40CFR192.12).
Transportation of excavated material to aaappropriate offsite facility
for disposal.
For areas of the site where modeling indicates that radon
concentrations in future buildings could exceed 4 pCi/Iiter, implement
institutional controls requiring that future buildings be constructed
using radon resistant construction methods.
Information on areas of subsurface PCB and radionudide
contamination that do not pose a risk if they are not disturbed shall be
incorporated into the TWC facilities maintenance plan. This
information will be made available to future site purchasers or
regulatory agencies.
The determination that action is. not required for certain areas of the
site is based oh.scenarios that do hot allow unrestricted use. Proper
handling and disposal of excavated material in accordance with
federal-and state laws is required should excavation occur as part of
future development of the TWC main plant or the soil amendment
area.
TELEOYNE WAH CHANG ALBANY SUPERFUNO SITE ESD PAGE 7 OF 13
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4.0 CHANGES TO THE GROUNDWATER AND SEDIMENTS REMEDY -
REQUIREMENTS™ THE ROD
I. Conditional Changes In The Western And Northern Perimeter
Containment Requirements;
H. Clarification In Requirements For the Farm Ponds Area;
III. Correction In Identification Of Sediment Areas Exceeding The
Action Level
4.1 Change I - Conditional Change in the Western and Northern Perimeter
Containment Requirements
ROD Requirement:
Contaminated groundwater in exceedance of SDWA MCLs. non-zero MCLs.
or cancer risk levels of 10"6 and noncancer risk HI > 1 for residential use
shall be prevented from migrating off the plant site [the compliance point is
the site boundary]. At and outside the compliance points, the PRPs shall
initiate groundwater extraction anywhere the cleanup levels are exceeded,
or as needed to meet RAOs.
Change: ..-•'• "..'•'
EPA has dropped the requirement for groundwater extraction at and outside the
plant boundaries on the northern and western perimeters. EPA believes that
groundwater will be reduced to the ROD cleanup levels at and outside these
compliance points through onsite groundwater remediation and natural attenuation.
The public will be protected from exposure to groundwater in exceedance of the
^cleanup standards through restrictions on groundwater use. Dropping the
perimeter requirements is contingent on meeting the conditions described below for
each perimeter. In addition, the site cleanup levels must still be met within the
ROD's time frame, the groundwater discharge into adjacent water bodies-must not
violate Federal and State water quality standards, and the remedy must still be
protective of both public health and the environment
The ROD focused only on meeting water quality standards for protection of human
health in areas beyond the TWC property boundary. This change to the ROD adds
the requirement that groundwater discharge to surface water bodies must be at
levels that will not impact the water body as described in the conditions for each
change.
Basis for Change:
During the development of the Scope of Work for the implementation of the
Remedial Actions in the groundwater ROD, TWC provided EPA with groundwater
TELEDYNE WAH CHANG ALBANY SUPERFUND SITE ESO PAGE 6 OF 13
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sampling results obtained subsequent to the Rl/FS sampling events. The
groundwater sampling results presented in the Rl/FS were for sampling events
ending in September 1991. The new data are from January and June 1994 and
1995 sampling events (attached as Appendix 1) These additional rounds of
groundwater sampling indicate that groundwater concentrations at the perimeter
wells and some of the site interior wells have decreased significantly since the
Rl/FS samples were taken.
EPA's decision to conditionally modify the perimeter requirements was based on
the following:
Groundwater concentrations are decreasing at the site perimeter. When
groundwater remediation via extraction commences onsite. there should be
additional decreases in concentration, therefore, the areas offsite should
reach the cleanup levels without additional offsite extraction.
The groundwater in offsite areas to the west of the plant is not currently
used, and is unlikely to be used as drinking water in the foreseeable future.
If there are no groundwater wells placed in this area until the groundwater
reaches the cleanup levels, human health will be protected.
On the northern perimeter, the groundwater discharges directly into Murder
Creek which forms the northern boundary of the plant Therefore,
potentially contaminated groundwater is not available for drinking water
offsite, and so does-not impact human health.
.•••.•-.. r • •
To the.west, groundwater discharges into Second Lake, and to the north, into
Murder Creek. Because water discharges into adjacent water bodies, water quality
for both Second Lake and Murder Creek could be a concern, and therefore surface
water protection is addressed in this ESQ.
Conditions Set for Each Perimeter.
Western Perimeter "•.-. • .
The requirement for perimeter containment and extraction will be dropped on the
western perimeter subject to the following conditions to ensure prbtectiveness:
\
1. Existing groundwater data, and data collected pursuant to the performance of
the remedial action, confirm that contaminant levels (and total excess cancer risk
and/or hazard indices) are declining at perimeter monitoring wells along the
property boundary (the compliance points) or reached an asymptotic
concentration acceptable to EPA and DEQ, and/or other site data or information
indicate that natural attenuation is effectively reducing contaminant levels in offsite
areas. If sufficient data is not available to make a statistical determination; EPA in
TELEOYNE WAH CHANG ALBANY SUPERFUNO SITE ESO PAGE 9 OF U
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consultation with DEQ may use best professional judgement in making this
determination. The current baseline for reaching the cleanup levels for the site is
15 years. "~
2) Existing and new surface water data, indicate that discharge of groundwater to
surface water bodies is not exceeding AWQCs. EPA in consultation with DEQ
may require that the discharge not exceed other protective criteria for pollutants or
contaminants, determined in accordance with risk assessment methodology, or
contained in promulgated rules, laws or standards. Therefore, depending on the
concentrations of contaminants remaining in the perimeter wells, TWC may have to
demonstrate through sampling or modeling that sediment contamination.
bioaccumulation, and contaminant loading will not be an environmental concern.
Surface water samples will be taken at locations where the groundwater enters the
surface water body for evaluation against applicable standards.
3) Within one year of initiation of the RD/RA. EPA/DEQ-approved deed restrictions
or other institutional controls acceptable to EPA and DEQ shall be in place for all
off-site properties where groundwater containing contaminants above cleanup
levels is present- These deed restrictions or other institutional controls shall notify
future potential buyers of site conditions/ prevent the installation of water supply
wells (and/or require proper abandonment of-existing wells), and shall run with the
land until groundwater contaminated above cleanup levels does not leave the site
boundary, and offsite cleanup levels are achieved.-: -
If the required deed restrictions or other institutional controls acceptable to EPA .
and DEQ are not in place within the .one year time period, EPA may require that
TWC begin design of an acceptable groundwater containment and/or off-site
extraction system, and the system shall be installed and operating within 2 years of
initiation of the RD/RA. If criteria 1 and 2 are not met. EPA in consultation with
DEQ may require that TWC implement groundwater containment and/or offsite
groundwater extraction as described in the groundwater ROD.
Implementation of this change to the ROD is dependant on the offsite property.^
owners voluntarily agreeing to have restrictions placed on their property. Obtaining
these restrictions will be at the initiative of TWC. EPA will not provide regulatory
assistance to TWC in obtaining the restrictions. If the institutional controls are hot
complied with, the requirement will not have been met and containment may be
required.
Northern Perimeter . •
The requirement for perimeter containment and extraction will be dropped oh the
northern perimeter subject to the following conditions:
No groundwater discharge to surface water will occur that causes exceedances of
TEUEDYNE WAH CHANG ALBANY SUPERFUNO SfTE ESO PAGE 10 OF 13
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AWQC in the receiving-water body or active remediation or containment will be
required. EPA in consultation with DEQ may require that the discharge not exceed
other protective criteria for pollutants or contaminants, determined in accordance
with risk assessment methodology, or contained in promulgated rules, laws or
standards. Therefore, depending on the concentrations of contaminants remaining
m the perimeter wells, TWC may need to demonstrate through sampling or
modeling that sediment contamination, bioaccumulation. and contaminant loading
will not be an environmental concern.
Surface water samples will be taken at locations where the groundwater enters the
surface water body for evaluation against applicable standards. In addition.
existing groundwater data, and data collected pursuant to the remedial action, must
indicate that contaminant levels (and total excess cancer risk and/or hazard
indices) are declining at perimeter monitoring wells along the property boundary
(the compliance points), or reached an asymptotic concentration acceptable to
EPA and DEQ. and/or other site data or information indicate that remediation is
effectively reducing contaminant levels. If sufficient data are not available to make
a statistical determination, EPA in consultation with DEQ may use best professional
judgement in making this determination. If this criterion is not met, active
remediation or-containment may be required. .
4.2 Change U - Clarification In Requirements For The Farm Ponds Area
ROD Requirement:
The ROD provides apparently inconsistent requirements for groundwater in the
Farm Ponds Area. The ROD defines the point of compliance in the Farm Ponds
Area as the edge of the Farm Ponds. • The ROD requires that at and outside the :
point of compliance, -groundwater extraction is required anywhere that the cleanup
levels are exceeded. Therefore, by defining the point of compliance as the edge
of the Farm Ponds, the ROD requires extraction to take place throughout the plume
in the Farm Ponds Area. This is inconsistent with the RODs proposed groundwater
action of pumping "hot spots" (high concentration areas) as a means of reaching
the groundwater cleanup levels. ••••'.'.
Change and Basis for Change: .
EPA has made the remediation requirements for the Farm Ponds Area consistent
with the rest of the site. Within the.Farm Ponds Area, remediation will take place
through extraction of hot spots. However, the plume in the Farm Ponds must be
kept from significantly expanding. Compliance with this requirement will be
demonstrated by existing groundwater data, and data collected pursuant to the
remedial action indicating that contaminant levels (and total excess cancer risk
and/or hazard indices) in wells in the Farm Ponds area are not increasing, or are
declining, and /or other site data or information indicate that natural attenuation is
effectively reducing contaminant levels. For consistency wrth the rest of the site.
TELEOYNE WAH CHANG ALBANY SUPERFUNO SfTE ESO PAGE 11 OF 13
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EPA has changed the point of compliance to the property boundaries in the Farm
Ponds Area.
4.3 Change 111 - Correction In Identification Of Sediment Areas Exceeding
The Action Level
ROD requirement.
The ROD requires the removal of PCS contaminated sediments exceeding 1 ppm
total PCBs from the surface water bodies adjacent to, or flowing through the Site.
The ROD identified areas on the Main Plant where sediment concentrations.
exceeded the site action level of 1 ppm total PCBs. In addition. Conser Slough was
identified as exceeding the action level of 1 ppm total PCBs.
Change and Basis for Change:
A review of the Rl/FS sediment data indicated that not all of the areas identified in
the ROD exceeded the sediment action level. Areas not exceeding the 1 ppm total
PCBs action level will not be remediated.
The areas not exceeding the sediment action which will not be remediated are the
following:
Conser Slough: The highest concentration was 0.5 ppm total PCBs.
Murder Creek at MTC-2: The highest concentration was 0.79 ppm total
PCBs. .
The areas exceeding the action level which were correctly-identified in the ROD
and will be remediated are the following: . .
The Murder Truax confluence at sample location MTC-2. The highest
concentration was 1.14 ppm total PCBs.
Truax Creek at the confluence with Second Lake overflow (sample location TC-
6 at 1.16 ppm total PCBs).
The portion of Tmax Creek that passes along the toe of the Truax Fill (locations
TO3.3 to TC-5 showed concentrations up to 20.8 ppm total PCBs). ;
5.0 Statutory. Determinations
Considering the new information that has been developed and the changes that
have been made to the selected remedy, the EPA and DEQ believe that the
remedy remains protective of human health and the environment, .complies with
federal and state requirements that were identified in the ROD as applicable or
relevant and appropriate to this remedial action at the time the original ROD
was .signed, and is cost effective.
TELEOYNE WAH CHANG ALBANY SUPERFUNO SITE ESO PAGE 12 OF 13
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6.0 Support Agency Comments
Consistent with EPA guidance, the Oregon Department of Environmental
Quality (DEQ) reviewed the ESD. Suggested changes were incorporated into
the text. OEQ supports this action and the implementation of the changes to the
Record of Decision.
7.0 Public Participation Activities:
EPA will hold a public comment period on the Explanation of Significant
Differences. The public comment period will be held concurrently with the
public comment period for the Consent Decree. Implementation of the ROD
changes will be subsequent to and subject to EPA addressing the public
comments.
Randall Smith, Director Date
Office of Environmental Cleanup
TELEOYNE WAH CHANG ALBANY SUPERFUND SUE ESO PAGE 13 OF 13
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Appendix: Groundwater Concentration Trends
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41
5 50
i IS-
5 10
flQUlO 10
Conconliallon liondi ol 1,1,1-TCA
• f obricolloo Atoo •
loiodyno Wah Chang
Flguio Ic
ConconlioiloA tiondi ol PCE
• Fabrication Aroo •
loiodynoWoh Chang •
Flguio Ib
Conconiiolion liondl ol 1,1-OCt
• fobilcollon Aioo •
lolodyno V/oh Chung
flguio Id
Conccnliollon tiondi ol ICf
• fobilcallon Aioo •
lolodyno Woh Chang
-------
90000
00000
70000
60000
50000
40000
30000
20000
(0000
0 <
Jin
-OG
Flguro lo
Conconliqllon TiandJ ol MIBK
• Fabrication Atoa •
toledynq Woh Chang
: • durtnj Ivnt t4, January 'V end >""
n«Mil(wei««i«cUdln ^r»«n •
obo«* lh« mtlhod diUcnnn Rmlt el IQug/ll
|-«-PW-OIA]
-90 Jin-JI Jtn-92 Jin-93 Jin-8« Jin-55 Jon-OO
Figure II
Conccniiailon 1(ona> ol v,nyi Cutout;;
• Fobricolion AIOQ •
lolodyno V/oh Chong
Jtn-06 Jan-87 Jin-00 Jan-03 Jin-fiO Jlfi-91 Jgn-92
-------
figure Ig
Conconlt ollon tiondfat Well PV/-12
• Fabrication Atoa •
lolodyno Wan Chang
0-0—.
Jon-8? jon-flj Jon-89 Jon-90 Jon-91 Jon-9? Jon-9J Jort-04 Jon-Oi Jon-96
•I.1.MCA
•I.I-OCA
•I.I-DCC
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llou'-l "i
Conconliollon Iiond» ol Won PW-4M
• Fobrtcallon Aioa •
lolodyno Woh Chang
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wan
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0
flguio II
Conconliollon Tiondt ol Wall PW-01A
• fooilcollon A(oa •
Toledyno Wan Chang
I lltUI«ll><
JOft-86 Jon-07
Jon-89
Jon^l Jon-9J JOn-Pl Jon-9
-------
flguio 2a
Conconliollon Iiondi ol 1,1,MCA
• Exliaclion Aroa •
tolodyno Wah Chang
f^«-pw.
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jciv6» Jor.4? JOA-OQ Jon-09 ;on-90' Jon-f I Jcxv»J Jon-91
;on-9$ Jon-96
flguio 2b
Conconliaiion liondi ol 1,7-OCE
• Eiliacllon'Aioa •
tolodyno Woh Cuong
Jon-46 Jon.4? Jon.88 Jon-49 JOn-W
:i
Figuio 2c •
Ccnconliotlon Trendt ol PCE
• ExifQdion Aroa •
Tolodyno Wah Chang
figuio 2o
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-------
Figure 2o
Concenlrallon Trends of MIBK
- Extracllon Area
Telodyne Wan Chang
8000 T
7000 ••
6000 •
< 5000 •
£
o
B 4000
."c
u
o
3000
2000
1000
nolo»i • no MIBK wo« doloclod In PW-24A
.• MIBK wa» dolocled once ol 5 ug/L
In PW-25A (Januciry 94), and onco
al 6 ug/L In PW-49A (April 90)
,-0-PW-22A
izX'.'.iGKO'j '•''•'<•
0/15/3J
-------
' iO
jj 30
flguio 21
Concenliollon liondi ol Woll PW-25A
• Exliocilon Aioo •
lolodyno Wah Chang
Jcn-04 JOA'J? Joft-90 Jon-91
i
joo-9) Jan-94 JaV?5 Jon-96
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• Exlioclion Aica •
Tolodyno Woh Chang
Jon-48 Jon-fl?
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