SECOND FIVE-YEAR REVIEW REPORT FOR
MODESTO GROUNDWATER CONTAMINATION SUPERFUND SITE
STANISLAUS COUNTY, CALIFORNIA
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PREPARED BY
United States Environmental Protection Agency
Region 9
San Francisco, California
Approved
Date:
Kathleen Salyer
Assistant Director, Superfund Division
California Site Cleanup Branch
U.S. Environmental Protection Agency Region IX
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Executive Summary
This is the second Five-Year Review of the Modesto Groundwater Contamination Superfund Site
(Site) located Modesto, Stanislaus County, California. The purpose of this Five-Year Review is to
review information to determine if the remedy is and will continue to be protective of human health
and the environment. The triggering action for this Five-Year Review (FYR) was the signing of the
previous FYR on September 9, 2008.
The Modesto Site is related to a dry cleaning facility that leaked tetrachloroethylene (PCE) into the
soil and groundwater. The dry cleaning facility discharged wastewater containing PCE into the sewer
system for approximately 50 years, and an unknown quantity of PCE was released into the subsurface.
An interim remedy for the site was selected in 1997 and included soil vapor extraction, groundwater
extraction and treatment for containment of the source area, primarily tetrachloroethylene (PCE), from
contaminated soil and groundwater. A final remedy has not been selected for the Site. The final
remedy will address the groundwater dissolved-phase plume, the soil contamination, and soil vapor
intrusion.
The assessment of this five-year review found that the remedy was constructed in accordance with the
requirements of the Interim Record of Decision (IROD).
The interim remedy of groundwater and soil vapor extraction, treatment, and discharge is functioning
as intended by the IROD. The goals of the interim remedy were to eliminate and contain the highest
contaminant levels at the source (source control) and to prevent potential exposure of human or
environmental receptors to PCE or other organic compounds released to the soil and groundwater.
These goals have largely been achieved, and EPA has made recent steady progress and is on track to
select a final remedy that will achieve appropriate groundwater cleanup levels. The exposure
assumptions, cleanup levels, ARARs, and remedial action objectives selected at the time of the
remedy are still valid. The Federal noncancer reference dose has increased slightly and the
carcinogenicity slope factor has decreased substantially for PCE. However, the State of California's
cancer slope factor for PCE has not changed. These changes in toxicity do not result in a significant
increase in estimated risk, and therefore, do not impact protectiveness. No other information has come
to light that could call into question the protectiveness of the interim remedy.
The interim remedy at the Modesto Groundwater Contamination Superfund Site is currently protective
of human health and the environment. Soil vapor extraction (SVE) and sub-slab vapor intrusion
mitigation have reduced indoor air PCE concentrations to be within acceptable levels, and there are no
complete receptor pathways for ingestion of impacted Site groundwater. To be protective in the long
term, the vapor intrusion pathway should be re-assessed when the SVE system is shut off.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Five-Year Review Summary Form
SITE IDENTIFICATION
Site Name: Modesto Ground water Contamination Superfund Site
EPA ID: CAD981997752
Region:: 9
State: CA
City/County:
NPL Status: Final
Multiple OUs?
Has the site achieved construction completion?
Lead agency: EPA
If "Other Federal Agency" was selected above, enter Agency name: Click here to enter
Author name (Federal or State Project Manager): Marie Lacey
Author affiliation: U8IEIPA Region 9
Review period: January 2013 - September 2013
Date of site inspection: February 21, 2013
Type of review: Policy
Review number: 2
Triggering action date: September 9, 2008
Due date (five years after triggering action date): September 9, 2013
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Five-Year Review Summary Form (continued)
Issues/Recommendations
OU(s) without Issues/Recommendations Identified in the Five-Year Review:
Issues and Recommendations Identified in the Five-Year Review:
OU(s): 1
Issue Category: Monitoring
Issue: The SVE system may have reached its remedial action objectives set forth
in the IROD; however, the system may be providing protection for indoor air vapor
intrusion, an objective not originally considered in the IROD.
Recommendation: Continue to monitor sub-slab and indoor air PCE
concentrations during cessation of the SVE system to ensure protective indoor air
levels are maintained.
Affect Current
Protectiveness
Affect Future
Protectiveness
Implementing
Party
Oversight Party
Milestone Date
No
Yes
EPA
EPA
1/2015
Sitewide Protectiveness Statement (if applicable)
For sites that have achieved construction completion, enter a sitewide protectiveness determination
and statement.
Protectiveness Determination:
Addendum Due Date (if applicable):
Protectiveness Statement:
The interim remedy at the Modesto Groundwater Contamination Superfund Site is currently protective
of human health and the environment. Soil vapor extraction (SVE) and sub-slab vapor intrusion
mitigation have reduced indoor air PCE concentrations to be within acceptable levels, and there are no
complete receptor pathways for ingestion of impacted Site groundwater. To be protective in the long
term, the vapor intrusion pathway should be re-assessed when the SVE system is shut off.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Contents
Executive Summary i
List of Figures vi
List of Tables vi
List of Abbreviations vii
1. Introduction 1
2. Site Chronology 2
3. Background 3
3.1. Physical Characteristics 3
3.2. Hydrology 5
3.3. Land and Resource Use 5
3.4. History of Contamination 6
3.5. Initial Response 6
3.6. Basis for Taking Action 6
4. Remedial Actions 8
4.1. Remedy Selection 8
4.2. Remedy Implementation 9
4.2.1. Soil Vapor Extraction System 9
4.2.2. Groundwater Extraction and Treatment System 10
4.3. Operation and Maintenance (O&M) 10
5. Progress Since the Last Five-Year Review 11
5.1. Previous Five-Year Review Protectiveness Statement and Issues 11
5.2. Work Completed at the Site During the Past Five Years 12
6. Five-Year Review Process 13
6.1. Administrative Components 13
6.2. Community Involvement 13
6.3. Document Review 14
6.3.1. ARARs Review 14
6.3.2. Human Health Risk Assessment Review 16
6.3.3. Ecological Risk Review 17
6.4. Data Review 17
6.4.1. Groundwater Hydraulic Data 17
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6.4.2. Groundwater Analytical Data and Trends 20
6.4.3. Groundwater Extraction and Treatment System Operational Data 22
6.4.4. Soil Vapor Analytical Data 22
6.4.5. Soil Vapor Extraction and Treatment System Operational Data 24
6.4.6. Indoor Air 24
6.5. Site Inspection 25
6.6. Interviews 26
6.7. Institutional Controls 27
7. Technical Assessment 28
7.1. Question A: Is the remedy functioning as intended by the decision documents?...28
7.1.1. Remedial Action Performance 28
7.1.2. System Operations/O&M 29
7.1.3. Opportunities for Optimization 29
7.1.4. Early Indicators of Potential Issues 29
7.1.5. Implementation of Institutional Controls and Other Measures: 30
7.2. Question B: Are the exposure assumptions, Toxicity Data, Cleanup Levels, and
Remedial Action Objectives (RAOs) Used at the Time of Remedy Selection Still
Valid? 30
7.3. Question C: Has Any Other Information Come to Light That Could Call Into
Question the Protectiveness of the Remedy? 31
7.4. Technical Assessment Summary 31
8. Issues 31
9. Recommendations and Follow-up Actions 32
10. Protectiveness Statement 33
11. Next Review 33
Appendix A: List of Documents Reviewed 34
Appendix B: Press Notices 41
Appendix C: Site Inspection Interview Reports 45
Appendix D: Site Inspection Checklist 53
Appendix E: Technical Data Review Memorandum 81
Second Five Year Review - Modesto Groundwater Contamination Superfund Site v
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List of Figures
Figure 1. Location Map for the Modesto Groundwater Contamination Superfund Site 4
Figure 2. Detailed Map of the Modesto Groundwater Contamination Superfund Site Depicting
Site Wells and Nearby Municipal Wells 7
Figure 3. A Zone PCE Plume Map with Potentiometric Contour Map and Estimated Empirical
Capture Zone for EW-02 (August 2012) 19
List of Tables
Table 1. Chronology of Site Events 2
Table 2. Annual O&M Costs 11
Table 3. Status of Recommendations from the 2008 FYR 12
Table 4. Applicable or Relevant and Appropriate Requirements Evaluation 15
Table 5. Exposure Pathways and Associated Reasonable Maximum Exposure Risks Based
on 1997 HHRA 16
Table 6. Industrial Risk Screening Levels and Maximum Soil Vapor Exposure Values from
2012 16
Table 7 Most Recent PCE Results in Source Area Groundwater (December 2012) 21
Table 8. Most Recent PCE Results in Vadose Zone Soil Vapor (December 2012) 23
Table 9. Most Recent PCE Results in Indoor Air (February 2012) 25
Table 10. IC Summary Table 27
Table 11. Current Issues for the Modesto Groundwater Contamination Superfund Site 31
Table 12. Recommendations to Address Current Issues at the Modesto Groundwater
Contamination Superfund Site 32
Second Five Year Review - Modesto Groundwater Contamination Superfund Site vi
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List of Abbreviations
ARAR
applicable or relevant and appropriate requirement
ATSDR
Agency for Toxic Substances and Disease Registry
bgs
below ground surface
Cal/EPA
California Environmental Protection Agency
CCR
California Code of Regulations
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act
cis-DCE
cis-dichloroethylene
CPT
Cone-Penetrometer Test
COC
contaminant of concern
DNAPL
dense non-aqueous phase liquid
DTSC
Department of Toxic Substances Control
EPA
Environmental Protection Agency
Ft
feet/foot
FYR
five-year review
GAC
granular activated carbon
GWETS
groundwater extraction and treatment system
gpm
gallons per minute
HHRA
Human Health Risk Assessment
IC
institutional control
IRA
Interim Remedial Action
IRIS
Integrated Risk Information System
IROD
Interim Record of Decision
LUC
land use covenant
MCL
maximum contaminant level
MWH
Montgomery Watson Harza
NAPL
non-aqueous phase liquid
NCP
National Contingency Plan
NPL
National Priorities List
O&M
Operations and Maintenance
OSHA
Occupational Safety and Health Administration
OSWER
Office of Solid Waste and Emergency Response
PCE
tetrachloroethylene
pCi/L
picocuries per liter
POTW
Publicly Operated Treatment Works
ppbv
parts per billion by volume
RAO
remedial action objective
RCRA
Resource Conservation and Recovery Act
RI
Remedial Investigation
RSL
regional screening level
RPM
Remedial Project Manager
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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RWQCB
Regional Water Quality Control Board
SVE
soil vapor extraction
TCE
trichloroethene
TSDF
Treatment, Storage and Disposal Facility
l-lg/L
micrograms per liter
USACE
United States Army Corps of Engineers
VI
vapor intrusion
VOC
volatile organic compound
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
viii
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Second Five-Year Review Report
for
Modesto Groundwater Contamination Superfund Site
1. Introduction
The purpose of a Five-Year Review (FYR) is to evaluate the implementation and performance of a
remedy in order to determine if the remedy will continue to be protective of human health and the
environment. The methods, findings, and conclusions of FYRs are documented in five-year review
reports. In addition, FYR reports identify issues found during the review, if any, and document
recommendations to address them.
The U.S. Environmental Protection Agency (EPA) prepares FYRs pursuant to the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) Section 121 and the National
Contingency Plan (NCP). CERCLA 121 states:
"If the President selects a remedial action that results in any hazardous substances,
pollutants, or contaminants remaining at the site, the President shall review such remedial
action no less often than each five years after the initiation of such remedial action to assure
that human health and the environment are being protected by the remedial action being
implemented. In addition, if upon such review it is the judgment of the President that action is
appropriate at such site in accordance with section [104] or [106], the President shall take or
require such action. The President shall report to the Congress a list of facilities for which
such review is required, the results of all such reviews, and any actions taken as a result of
such reviews. "
EPA interpreted this requirement further in the NCP; 40 Code of Federal Regulations (CFR) Section
300.430(f)(4)(ii), which states:
"If a remedial action is selected that results in hazardous substances, pollutants, or
contaminants remaining at the site above levels that allow for unlimited use and unrestricted
exposure, the lead agency shall review such actions no less often than every five years after
the initiation of the selected remedial action."
Region 9 EPA conducted the FYR and prepared this report regarding the remedy implemented at the
Modesto Groundwater Contamination Superfund Site (the Site) in Modesto, Stanislaus County,
California. EPA Region 9 is the lead agency for developing and implementing the remedy for the Site.
The Seattle District Corps of Engineers (USACE) project delivery team provided assistance to the
EPA during the FYR process.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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This is the second FYR for the Modesto Groundwater Contamination Superfund Site (Modesto Site, or
"the Site"). The triggering action for this policy review is the previous FYR signed September 30,
2008. The FYR is required due to the fact that hazardous substances, pollutants, or contaminants
remain at the site above levels that allow for unlimited use and unrestricted exposure.
The Interim Record of Decision (IROD) prescribed remedial actions of groundwater extraction and
treatment and soil vapor extraction and treatment. Both the groundwater extraction and treatment
system (GWETS) and the soil vapor extraction (SVE) and treatment systems are current operating
remedies. The IROD also prescribed Institutional Controls (ICs) of fencing and signage installation
and maintenance around the remedial system components. This FYR addresses groundwater and
soil/soil vapor, and the related ICs implemented at the Site.
2. Site Chronology
The following table lists the dates and describes important events for the Modesto Site.
Table 1. Chronology of Site Events
Event
Date
Initial discovery of contamination:
Modesto Municipal Well 11 found to be contaminated with PCE
September 1984
Pre-NPL responses:
Investigations of soil, groundwater, and sanitary sewer lines by RWQCB and
City of Modesto confirmed Halford's Cleaners as Municipal Well 11 PCE
source.
April 1985 -
April 1990
NPL listing:
Modesto Site placed on National Priorities List
March 1989
EPA issued order to Potential Responsible Parties for treatment of
contaminated soil
September 1990
Removal actions:
Potential Responsible Parties conducted Removal Action consisting of limited
soil vapor extraction (SVE) system
February 1991
EPA took over investigation and cleanup activities from Potential Responsible
Parties
1991
Municipal Well 11 permanently deactivated due to presence of naturally
occurring uranium
October 1995
Remedial Investigation completed
December 1996
Feasibility Study completed
March 1997
Baseline Human Health Risk Assessment completed
July 1997
IROD signed
September 1997
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Event
Date
Remedial Actions:
Soil Vapor Extraction (SVE) and Treatment System installed
Groundwater Extraction and Treatment System (GWETS) installed
Start - May 2000
Start - June 2000
GWETS extraction well EW-01 permanently shut off due to operational
difficulties
November 2004
GWETS replacement extraction well EW-01R installed
June 2006
Supplemental Site Investigation completed
January 2007
EPA conducted vapor intrusion investigation at source area
February 2008 -
February 2012
EPA completed vapor intrusion mitigation in two businesses at source area
February 2008 -
April 2010
First Five-Year Review
September 2008
SVE Optimization Report completed
June 2008
SVE system expanded
October 2008
Groundwater Remediation Optimization Report completed
March 2010
New extraction well EW-02 installed, GWETS optimized through operation of
EW-02 and shut down of EW-01R
June-September
2012
GWETS operation transferred from EPA to state
July 2012
3. Background
The City of Modesto is located approximately 80 miles southeast of Sacramento, California in
Stanislaus County. In 2011, the US Census Bureau estimated the population of Modesto to be
202,751. The Modesto Site is located approximately 1.5 miles north of downtown on McHenry
Avenue, between West Fairmont Avenue and Griswold Avenue. The Site originated from Halford's
Cleaners (941 McHenry), a commercial dry cleaning business (Figure 1). The site encompasses both
the source area and the area affected by the dissolved-phase contaminant plume as discussed later in
this section.
3. 1 Physical Characteristics
Site topography is flat and ground surface elevation is about 90 feet above mean sea level. The Site
and its immediate surroundings are within an older and highly developed and populated portion of
Modesto. Nearly all the land surface above the contaminant source area is paved or covered by
buildings. The Site is not located in or near an environmentally sensitive area.
Sediments beneath the Site are composed of San Joaquin River channel and floodplain deposits, and
alluvial fan deposits from the Sierra Nevada Mountains which define the northeastern boundary of the
San Joaquin Valley. These sediments generally consist of interbedded sands, silts, sand-silt mixtures,
and clays; these beds are usually less than ten feet thick (EPA, IROD, 1997).
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Figure 1. Location Map for the Modesto Groundwater Contamination Superfund Site
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bgy
There are three relatively correlative and contiguous sandy horizons comprising the three principal
aquifer zones, separated by much lower permeability aquitards, beneath the Site. The depositional
environment was such that numerous thin, finer grained and laterally discontinuous layers are
interwoven within the three principal aquifer zones.
The uppermost saturated, sandy horizon is referred to as the aquifer A zone. This zone occurs from
near ground surface to a depth of approximately 95 to 100 feet. This zone is unconfined and contains
the greatest proportion of more transmissive fine to medium grained sands. The A zone groundwater
elevations range from approximately 47.5 ft msl to 50.5 ft msl. Groundwater horizontal hydraulic
gradient in this zone averages about 0.0018 ft/ft toward the southeast.
A grouping of fine-grained silt, very fine-grained cemented silty sands and thin clay layers forms the
A/B aquitard, which separates the A zone from the B zone below. This aquitard generally decreases in
thickness from the north (near the contaminant source area), where its thickness is about 80 feet, to the
south, where it is about 40 to 45 feet thick.
The aquifer B zone is described as the first lower level sandy horizon beneath the Site and is about 15
to 40 feet thick (thickening to the south). The B zone occurs beneath the A/B aquitard to a depth of
155 to 165 feet and is semi-confined. Sand is generally finer grained and hence less transmissive than
in the A zone. B zone groundwater elevations range from about 46 ft msl to 49 ft msl. Horizontal
hydraulic gradient for the B zone has been reported as 0.0011 ft/ft to the southeast.
The B/C aquitard is comprised of similar geologic strata as the A/B aquitard, and separates the B zone
and C zone. It is generally thinner than the A/B aquitard, and its thickness varies from 10 to 40 feet.
The aquifer C zone is the second lower level sandy horizon. The top of this unit occurs from the
bottom of the B/C aquitard and continues beyond the total depth monitored for the Modesto Site. C
zone thickness varies throughout the Site from 45 feet to 10 feet or less. C zone groundwater
elevations range from approximately 42.5 feet msl to 44 feet msl. While vertical gradients between
aquifer zones are generally downward, vertical gradients within the C zone itself are reportedly
upward. Horizontal hydraulic gradient for the C zone has been reported as approximately 0.0010 ft/ft
to the south-southeast.
3,3, Land and Resource Use
McHenry Avenue is a busy thoroughfare with a range of commercial businesses, including two motels
and a senior assisted living facility between the 800-900 blocks. The areas on either side of McHenry
are primarily single-family residential units. Future land use within the vicinity of the Site is projected
to continue to be commercial and residential. This entire portion of Modesto is on public city water
supply; there are no known active private or commercial wells for consumptive groundwater use. The
City well permitting process currently prohibits well installation for consumptive use. There are no
complete pathways for ecological receptors.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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toiy of Contamination
The Modesto Site is related to a dry cleaning facility that leaked tetrachloroethylene (PCE) into the
soil and groundwater. The dry cleaning facility discharged wastewater containing PCE into the sewer
system for approximately 50 years, and an unknown quantity of PCE was released into the subsurface.
The old leaky dry cleaning equipment was replaced with new equipment, and PCE is no longer being
discharged from the facility. The dry cleaner is located approximately 1,200 feet from a municipal
well (Municipal Well 11) (Figure 2). Municipal Well 11 was contaminated with PCE from the dry
cleaner because when the well was in operation, it pulled contaminated groundwater toward and
eventually into the well. The City of Modesto began monitoring groundwater in 1984 and Municipal
Well 11 was found to be contaminated with PCE at a concentration of 16.7 micrograms per liter
(|ig/L). The Safe Drinking Water Act Maximum Contaminant Level (MCL) for PCE is 5 |ig/L.
a/ Response
To protect the public drinking water supply, Well 11 was taken out of service by the City in 1984 as
soon as PCE above the MCL of 5 |ig/L was detected in the well. In 1987, PCE and other volatile
organic compounds (VOCs) were not detected in groundwater samples; therefore, Well 11 was
reactivated. In February 1989, Well 11 was again taken out of service after PCE again exceeded the
MCL. The well remained out of service until the City installed a wellhead granular activated carbon
(GAC) treatment system in May 1991. The GAC system effectively reduced the PCE concentration to
below the MCL prior to the water entering the public supply system. Municipal Well 11 was returned
to service in June 1991 and operated until October 1995, when the City indefinitely deactivated it
because naturally occurring uranium was detected above its MCL of 20 picocuries per liter (pCi/L)
(MWH Americas, Inc., 2007). The uranium in some Central Valley California soils is naturally
occurring and is believed to be derived from alluvial deposition of eroded uranium-containing Sierra
Nevada igneous rocks.
The Modesto Site was placed on EPA's National Priorities List (NPL) on March 31, 1989.
lis for Taking Action
The primary contaminant of concern for the Modesto Site is PCE. The presence of this contaminant in
groundwater provided the basis for taking action under CERCLA. PCE is considered likely to be
carcinogenic in humans by all routes of exposure, as well as having neurotoxic effects (EPA Integrated
Risk Information System; February 10, 2012 update). The primary threat to human health listed in the
Human Health Risk Assessment was posed by ingestion of groundwater. This potential threat was the
basis for taking initial action. A secondary threat to human health was estimated to be posed by
inhalation of indoor air vapors as a result of volatilization of PCE from groundwater and soil; this
potential threat led to additional investigation and testing as well as mitigative efforts to reduce the
threat.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Figure 2. Detailed Map of the Modesto Groundwater Contamination Superfund Site Depicting
Site Wells and Nearby Municipal Wells
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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4. Remedial Actions
4.1. Rer lion
In September 1997, EPA issued an interim Record of Decision (IROD) that selected soil vapor
extraction/treatment and groundwater extraction/treatment as the interim remedial technologies for
removal and treatment of contamination in soil and groundwater. EPA issued an interim Record of
Decision instead of a final Record of Decision due to uncertainties over whether the groundwater
cleanup standards could be met throughout the plume. The overall objective of the interim remedial
action (IRA) selected in the IROD was "to eliminate and contain the highest contaminant levels at the
source (source control) and to prevent potential exposure of human or environmental receptors to PCE
or other organic compounds (e.g., toluene) released to the soil and groundwater."
The following remedial action objectives (RAOs) are listed in the IROD:
1) Eliminate and contain the highest contaminant levels at the source (source control),
2) Prevent exposure to contaminated groundwater, above acceptable risk levels, to protect human
health and the environment (MCLs),
3) Minimize the impact of interim cleanup measures to the community,
4) Collect data to determine if Federal and State requirements can be met throughout the aquifer, and
5) Delineate more clearly the downgradient edges of the plume and prevent its further migration.
In addition, the IROD stated that the "operation of the extraction well will draw groundwater in the
most contaminated, source-area portions of the plume to the well, thus inhibiting downgradient
migration of those source area contaminants."
The primary components of the selected remedy include groundwater extraction, groundwater
treatment by air stripping with carbon adsorption, discharge of treated groundwater to the City of
Modesto's Publicly Operated Treatment Works (POTW) sanitary sewer system, and SVE followed by
carbon adsorption.
The components of the interim remedy, as stated in the ROD, are summarized as follows:
• Groundwater Extraction - A pumping rate of 50 gallons per minute (gpm), which includes
one or more extraction wells, will be used to achieve a capture zone of approximately 250 to
300 feet. This will remove the most contaminated groundwater near the source area and
hydraulically isolate this area from the surrounding aquifer. EPA will be monitoring the
downgradient edge of the plume to determine if natural attenuation is occurring since there
will be no continuing source of contamination.
• Groundwater Treatment by Air Stripping - Air stripping is a simple, straightforward
technology to transfer volatile organic compounds from a dissolved liquid phase to a vapor
phase. Air will be sparged into a packed column or shallow trays designed to maximize
interfacial surface area and shear, resulting in high mass transfer rates. The solvent-laden gas
will then pass over a bed of activated carbon to remove PCE and other organic vapors from
the off-gas stream.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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• Discharge of Treated Groundwater - Treated groundwater is discharged to the sanitary
sewer system. Although uranium is a naturally occurring, regional contaminant, additional
treatment of extracted groundwater to remove uranium is necessary to satisfy disposal
requirements.
• Soil Vapor Extraction - SVE in the vadose zone will be used to increase the rate of removal
of contaminants that are diffusing from the groundwater to the vadose zone. SVE removal
efficiency will be evaluated through the IRA. Some SVE wells will be screened near the water
table to achieve effective removal. The solvent laden gas would be extracted, and then passed
over a bed of activated carbon to remove PCE and other organic vapors from the off-gas
stream.
Based on data collected during the IRA, EPA will calculate the threat to groundwater from the
soil. EPA will also calculate the extent to which the SVE system accelerates groundwater
cleanup. EPA will cease SVE when the soil no longer poses a threat to groundwater and no
longer accelerates contaminant removal from groundwater.
• Institutional Controls - The ROD referred to the engineering controls of signing and fencing
around the treatment area as institutional controls. These engineering controls will be
maintained for the duration of treatment, and the need for institutional controls will be
included in the final remedy.
No chemical-specific cleanup standard was selected in the IROD. This was deferred until the final
groundwater remedial action decision for the Site.
olementation
Installation of the SVE and GWET systems were completed on May 16 and June 12, 2000,
respectively. The SVE and GWET systems operated intermittently between May and October 2000
due to technical operating issues that required frequent operator attention. MWH Americas, Inc.
(MWH) was contracted by the USACE Sacramento District office to operate, maintain, monitor, and
report on the progress of the remedial systems between 2000 and 2009. Since 2009, URS Group, Inc.
(URS) was contracted for these services.
4.2.1. Soil Vapor Extraction System
The implemented SVE system consists of soil vapor extraction wells, a blower, a condensate
collection drum, air filters, silencers, one 2,000-pound vapor-phase granular activated carbon vessel,
conveyance piping, control systems, and an air conditioning unit to keep the electronics from
overheating. When the system first began operation, soil gas was extracted via a single extraction
well, SVE-01. The system was optimized and expanded in 2008. Currently, vapor is extracted from
three extraction wells (SVE-02, SVE-03, and SVE-04). The system is designed to extract at a rate of
180 standard cubic feet per minute. Extracted soil vapor passes through an air-water separator; liquid
that accumulates in the condensate collection drum is pumped to the GWT system for treatment. The
SVE system has run on a continual basis since late 2000, except for minor periods of maintenance or
testing.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Additional site investigations were performed in January 2007 to address reduced effectiveness of the
single extraction well SVE system and uncertainty as to the extent of groundwater contamination. The
additional investigation identified significant residual contamination in borings adjacent to Halford's
Cleaners and was the reason for system expansion in 2008.
4.2.2. Groundwater Extraction and Treatment System
The implemented GWETS consists of extraction wells, an equalization tank, an air stripper, two
liquid-phase granular activated carbon vessels, one vapor-phase carbon vessel, and two ion exchange
units, as well as piping and control systems. The GWETS has historically operated at the design
capacity of approximately 50 gallons per minute throughout its operational history. The system uses
an air stripper and a granular activated carbon filter to capture VOCs from groundwater and an ion
exchange unit with resin to capture the naturally occurring uranium. Treated water is sent to the City
of Modesto POTW via underground sanitary sewer lines.
The GWETS ran from late 2000 to November 2004 with only minor down-time for maintenance. The
GWETS was not operational between November 2004 and June 2006, because the original extraction
well (EW-01) was inoperable due to mechanical problems and well integrity issues. A new well was
constructed (EW-01R) and the GWETS again ran with minimal downtime due to periodic
maintenance between June 2006 and August 2012. In August 2012, well EW-01R was shut down and
has not operated since that time. To better capture higher concentration dissolved PCE in groundwater
downgradient of the source area, extraction well EW-02 was installed and brought online by
September 2012. EW-02 has been in continuous operation since that time.
Additional Site and plume characterization work was conducted to further refine the implemented
interim groundwater remedy. In 1997 EPA installed six monitoring wells to delineate the vertical and
horizontal extent of the dissolved plume in the A zone (MW-10 through MW-15, now called MW-10A
through MW-15A). These wells are screened, in general, between 69 and 100 feet. Quarterly sampling
of these wells started in 1998. In 2007, EPA continued its investigation of the extent of the dissolved
plume by drilling 14 borings, collecting grab groundwater samples at various depths and performing a
Cone-Penetrometer Test (CPT) scan further downgradient from the source area. Based on the findings
of this investigation, EPA installed 16 additional downgradient monitoring wells within all three
aquifer zones in 2008 for further PCE plume delineation and characterization. A CPT and
HydroPunch™ investigation was conducted in 2011 to optimize the location of the new groundwater
extraction well, EW-02. Nine additional A zone and B zone wells were installed in 2011 to further
define the PCE plume margins in those zones.
Responsibility for operation of the GWETS was transferred from EPA to the state of California
Department of Toxic Substances Control (DTSC) on July 5, 2012.
?ration and Mc 1 . ')
Table 2 shows the combined O&M costs for the GWETS and SVE. These costs include routine
monitoring and operational costs, discharge permit fees, system performance monitoring, and
contractor management and reporting costs. Also included are extraction well replacement evaluation
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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and installation costs. Costs from 2002-2003 were highest due to work conducted pursuant to a
Remediation System Evaluation conducted jointly by EPA and USACE. Costs were lower from 2005
to 2006 as a result of the extraction well being shut off. Costs also dropped after sample analysis
shifted from private labs to the EPA Region 9 Lab.
Table 2, Annual O&M Costs
Date Range
Total Cost (rounded to the
nearest $1,000)
Average Monthly Cost
2008 IROD Alternative
Assessment Estimate
$342,000
$28,500
2008
$195,000
$16,250
2009
$321,000
$26,750
2010
$231,000
$19,250
2011
$273,000
$22,750
2012
$254,000
$21,167
Groundwater monitoring costs increased after Fall 2008 due to installation of 16 new wells. In 2009
implementation of changes to optimize the remedy occurred, which resulted in some initial expense. In
December 2009 the resin in the two ion exchange vessels had to be disposed as low-level radioactive
waste at significant additional cost. Subsequently, the operators are initiating changeout sooner.
Starting Fall 2007, sewer discharge fee increased incrementally from approximately $1,600 per month
to approximately $3,300 within about two years.
O&M costs for the GWETS were assumed by the state of California in July 2012, when responsibility
for that component of the interim remedy was transferred from EPA to the state DTSC.
5. Progress Since the Last Five-Year Review
Previo /iew Protectiveness Si les
The protectiveness statement from the 2008 FYR for the Modesto Site stated the following:
The Interim remedy at the Modesto Groundwater Contamination Superfund Site is not
protective of human health and the environment due to the vapor intrusion ofPCE into two
businesses near the source. The operating groundwater portion of the remedy is protective of
human health and the environment in the short term because there are currently no known
complete receptor pathways (i.e., no drinking water wells within or downgradient of the
plume). In order to be protective in the long-term, a final remedy for the Site must be selected
to address the dissolved phase plume.
The 2008 FYR included three issues with corresponding recommendations for their redress. Each
recommendation and the current status are discussed below.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Table 3. Status of Recommendations from the 20
Issues from
previous FYR
Recommendations
Action Taken and Outcome
Date of
Action
Indoor Air
Vapor Intrusion
Pathway
Add vapor
extraction wells to
SVE system to
reduce vapor
intrusion through
slab floors
Three wells added to SVE system
and vapor intrusion mitigation
measures carried out in source area
building. Subsequent indoor air
sampling found that PCE
decreased to levels below the EPA
Regional Screening Level (RSL).
2008-2012
High soil/soil
vapor PCE
concentrations
See above
Three wells added to SVE system.
2008
Dissolved PCE
plume not
defined or
controlled
Complete dissolved
plume investigation,
evaluate need for
expansion of the
interim remedy, and
select final remedy
for Site
Further investigation conducted;
extraction well EW-02 completed
and operating for better plume
capture; FS for final remedy in
progress. The installation of a new
groundwater extraction well in
2012 optimized the GWETS to
contain and capture higher-
concentration dissolved-phase
PCE.
2008-2013
rk Completed at the Site During the Fas! Five Years
Groundwater
Sixteen groundwater monitoring wells were installed in October-November 2008 to further define the
lateral and vertical extents of the PCE plume in downgradient areas of all three aquifer zones as part of
the groundwater optimization program. In August-September 2011, nine additional monitoring wells
were installed for further plume definition in the A and B zones. A remediation optimization study
conducted in 2010 by the remedial contractor (MWH Americas, Inc, 2010) concluded that a new
groundwater extraction well was needed to meet the interim remedial action objective for the Site. To
address this need, a cone penetrometer (CPT) and HydroPunch™ investigation consisting of 10
borings was conducted to determine the optimal placement location of a new groundwater extraction
well (EW-02) in May-June 2011. EW-02 was then installed, connected to the GWETS, and tested in
June-July 2012. A technical evaluation of Modesto Municipal Well production effects on the Site
using a series of down-well pressure transducer/data loggers was performed in 2012. The results
showed that municipal well pumping directly affects local water levels, especially in the C zone.
Eight additional groundwater monitoring wells were installed in 2013 to improve plume definition.
Finally, continued groundwater extraction and treatment, and quarterly groundwater monitoring,
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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including water elevations, VOCs, and select MNA parameter testing took place quarterly since the
last FYR was completed.
Soil/Soil Vapor
In October 2008 the SVE system was expanded through the addition of three vapor extraction wells
and two vapor monitoring wells, and conversion of previous single vapor extraction well to a vapor
monitoring well. This work was performed based on recommendations made in an October 2007 SVE
system optimization and enhancement report. During the same 2008 field mobilization, one borehole
was drilled adjacent to vapor extraction well SVE-02, within seven feet of the dry cleaning machine
inside Halford's Cleaners for a limited soils DNAPL investigation (no DNAPL was observed). Indoor
air vapor intrusion sampling in source area businesses, outdoor ambient air sampling, and sub-slab soil
vapor sampling was conducted in 2008-2012. Continued soil vapor extraction and treatment, vapor
intrusion mitigation measures, and quarterly soil vapor monitoring for VOCs at the vapor extraction
monitoring points has occurred quarterly since the last FYR.
6. Five-Year Review Process
6. 1 Administrati •mponenis
EPA Region 9 initiated the FYR in January 2013. The EPA FYR team was led by Marie Lacey, EPA
Remedial Project Manager (RPM) for the Modesto Site, and also included the EPA site attorney and
community relations personnel. The US ACE provided technical support with the FYR and reporting.
The USACE team included Cathy Martin (Seattle District chemist), Jefferey Powers (Seattle District
hydrogeologist), John Wakeman (Seattle District risk assessor), and Doug Mackenzie (Sacramento
District project lead and remedial contractor oversight). On January 3, 2013 EPA held a scoping call
with the review team to discuss the Site and items of interest as they related to the protectiveness of
the remedy currently in place. A review schedule was established that consisted of the following:
• Community notification;
• Document review;
• Data collection and review;
• Site inspection;
• Local interviews; and
• Five-Year Review Report development and review.
6. 'ement
On April 1, 2013, a public notice was published in the Modesto Bee announcing the commencement of
the Five-Year Review process for the Modesto Groundwater Contamination Superfund Site and
inviting community participation. Public notices were also published in Vida En El Valle, a Spanish
language weekly publication, on April 3, 2013, and Mundo Hispana, a Spanish language monthly, on
April 15,2013.
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The Five-Year Review report will be made available to the public when it is finalized. Copies of this
document will be placed in the designated public repository, the name and address of which is:
Stanislaus County Free Library, 1500 I Street, Modesto, California. Upon completion of the FYR, a
public notice will be placed in the same three publications that were utilized for the announcement of
the commencement of the review. A final copy of the FYR will also be placed at the designated public
repository upon completion.
On April 15, 2013, the EPA RPM visited the Stanislaus County Free Library to verify Site-related
Administrative Record documents were publicly available. She found that Site documents were
available for public viewing by making a request to see them at the library's reference desk. The
documents can also be requested on the library's website.
Quarterly monitoring reports for the Modesto Site are posted on the EPA website for public review.
:ument Review
This FYR included a review of relevant, site-related documents including the IROD, remedial action
reports, recent investigation reports, and recent monitoring data and associated reports. A complete list
of the documents reviewed can be found in Appendix A.
6.3.1. ARARs Review
Section 121 (d)(2)(A) of CERCLA specifies that Superfund RAs must meet any federal standards,
requirements, criteria, or limitations that are determined to be legally ARARs. Applicable or Relevant
and Appropriate Requirements are those standards, criteria, or limitations promulgated under federal
or state law that specifically address a hazardous substance, pollutant, contaminant, RA, location, or
other circumstance at a CERCLA site.
The IROD identified several chemical-specific potential ARARs, but stated that" Operation of this
alternative as part of the IRA would help determine whether chemical-specific ARARs could be met"
ARARs identified in the 1997 IROD that are not pertinent to the operational phase of the remedy or
chemical-specific are not included in Table 5. There have been no revisions to laws and regulations
that affect the protectiveness of the remedy.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Table 4. Applicable or Relevant and Appropriate Requirements Evaluation
Requirement
Citation
Document
Description
Effect on Protectiveness
Comments
Amendment Date
Chemical-Specific ARARs
S|>i-n 1 < .ii liuil
1 - Subtitle C, 42 USC
§6921, et seq.
1 - Requires generators to determine whether waste is
subject to land disposal restrictions
1-28 March
2013
RCRA
2 - Hazardous Waste Control
Act
1997 IROD
2 - Established the California Hazardous Waste
Control Program within DHS. California's hazardous
waste regulatory effort became the model for the
federal Resource Conservation and Recovery Act
(RCRA). California's program, however, was broader
and more comprehensive than the federal system,
regulating wastes and activities not covered by the
federal program
There have been no changes
to these law that that affect
protectiveness
Requirement to
determine whether
carbon filtration units
from treatment of
vapors are subject to
land disposal
restrictions is applicable
2 - February
2011
3 -, Cal. Health & Safety
Code §25100, et seq.
3 - Establish regulations and incentives which ensure
that the generators of hazardous waste employ
technology and management practices for the safe
handling, treatment, recycling, and destruction of their
hazardous wastes prior to disposal
3-2 March 1982
Action-Specific ARARs (SVE and GWET system usage) I
Clean Air Act,
42 USC §7401, et seq./
California State
Implementation Plan (SIP)
1997 IROD
The SIP describes how the State air quality programs
will be implemented to meet compliance with the
CAA standards, including ambient air standards
There have been no changes
to these law/regulations that
that affect protectiveness
Remedial actions should
comply with relevant
substantive
requirements of the SIP
5 May 2010
Clean Air Act,
42 USC §7401, et seq./ San
Joaquin Valley Unified Air
Pollution Control District,
Rule 2201
1997 IROD
Stationary sources rule requires application of best
available control technology to new or modified
emissions unit if unit would increase emissions more
than 2 pounds per day
There have been no changes
to these law/regulations that
that affect protectiveness
For controlling air
emissions from soil
vapor and groundwater
treatment units,
applicable depending on
quantity and types of air
emissions
21 April 2011
Clean Air Act,
42 USC §7401, et seq./ San
Joaquin Valley Unified Air
Pollution Control District,
Rule 4101
1997 IROD
Visible emission limits prohibit emission of more than
3 minutes/hour of certain types of visible emissions
There have been no changes
to these laws/regulations that
that affect protectiveness
For controlling air
emissions from soil
vapor and groundwater
treatment units
17 February 2005
Clean Air Act
42 USC §7401, et seq./ San
Joaquin Valley Unified Air
Pollution Control District,
Rule 4102
1997 IROD
Prohibits discharge of air contaminants that will be a
nuisance or will endanger the public
There have been no changes
to these laws/regulations that
that affect protectiveness
For controlling air
emissions from soil
vapor and groundwater
treatment units
17 December
1992
Clean Air Act
42 USC §7401, et seq./ San
Joaquin Valley Unified Air
Pollution Control District,
Rule 4201
1997 IROD
Particulate matter emission standard prohibits emission
of dust, fumes or total suspended particulate matter
greater than 0.1 grain per cubic foot of gas at dry
standard conditions. Prescribes certain EPA analytical
methods
There have been no changes
to these laws/regulations that
that affect protectiveness
For controlling air
emissions from soil
vapor and groundwater
treatment units
17 December
1992
RCRA
42 USC §6901,
et seq./ Air Emissions
Standards for Process
Vents, 40 CFR Part 264,
Subpart AA
1997 IROD
Air emissions standards for process vents associated
with air stripping operations managing hazardous
wastes with organic concentrations of at least 10 ppmv
There have been no changes
to these laws/regulations that
that affect protectiveness
Potentially applicable to
air strippers used in
groundwater
remediation, depending
on concentrations of
extracted groundwater
14 July 2006
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6.3.2.
Human Health Risk Assessment Review
In 1994, EPA conducted a baseline human health risk assessment, which was subsequently revised and
updated in 1997 to incorporate Phase 3 Remedial Investigation (RI) data. The risk assessment identified
the exposure pathways at the Modesto Site as residential groundwater ingestion (including drinking of
water and inhalation of vapors from water) and inhalation of indoor air. Current and future land and
groundwater use scenarios were evaluated using soil gas and groundwater data collected during the RI for
PCE and other VOCs.
The Reasonable Maximum Exposure (RME) results of the 1997 risk assessment indicated the then-
current and future carcinogenic risks from inhalation of indoor air potentially impacted by soil gas
ranging from 9xl0"7 to 9xl0"6, with the hazard indices ranging from 0.1 to 0.5. These risk levels were
considered in the acceptable range for cancer and non-cancer effects, respectively. Under future land use
conditions assuming consumptive use of impacted Site groundwater, carcinogenic risks ranged from
lxlO"2 to 5xl0~2 while the hazard indices ranged from 100 to 400 (Table 5). These levels were
considerably in excess of the acceptable risk range for carcinogenic and non-cancer effects; hypothetical
ingestion of untreated groundwater and inhalation of contaminants volatilizing from that water
contributed to the greatest risk.
Table 5, Exposure Pathways and Associated Reasonable Maximum Exposure Risks Based on
1997 HHRA
Kxposurc Sccnsirio »S I'silhwsiv
1 hi/;ird Index
rmi:
llii/iird Index
A\crsi»c
Csinccr Risk
rmi:
Csinccr Risk
A\cr:i»c
Current Indoor Air - Inhalation of
Soil Gas
0.5
0.1
9x10~6
9x10~7
Future Indoor Air - Inhalation of
Soil Gas
0.5
0.1
9x10~6
9x10~7
Future Ingestion and Inhalation of
Groundwater as Drinking Water
400
100
5x10~2
lxlO"2
The risk assessment and subsequent promulgated regulations were reviewed to identify any changes in
exposure or toxicity that would impact protectiveness. EPA recently reassessed PCE toxicity literature for
both cancer and non-cancer effects, and released an Integrated Risk Information System (IRIS)
toxicological review in February 2012. However, the IROD values are consistent with the current
California carcinogenic toxicity values and therefore the 1997 risk assessment conclusions are still
appropriate.
Indoor air inhalation. The cancer risk screening level for PCE at the site was developed using Cal/EPA's
cancer potency value in combination with U.S. EPA exposure assessment assumptions for
commercial/industrial workers; the resultant lxlO"6 risk screening level is 2.1 |_ig/m3 (0.3
ppbv). Screening for non-cancer hazards utilizes the revised non-cancer RSL based on adverse
neurological effects; this results in a level of concern of 180 |_ig/m3 (26.5 ppbv) for an industrial
establishment. While RSLs for indoor air are not de-facto cleanup standards for a Superfund site, they
may indicate whether additional actions or evaluations are needed. Site risks for indoor air inhalation at
the maximum 8-hour sample value collected in 2012 are below EPA's risk range. The 8-hour sampling
occurred during normal business hours and reflects the actual exposure. However, the 24-hour sampling
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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event result was greater than the 8-hour average sampling event indicating potential for vapor intrusion
when the building is closed.
Table 6. Industrial Risk Screen els and Maximum Soil Vapor Exposure Values from 2012
Exposure
Scenario »S
P:it liw :i\
I nils
RSI,: 1 lazard
Quotient (1IQ
= 1 for PCE)
Cancer Risk
(IxlO" lor
I'C 1!)
Maximum
Detected l.c\cl
at llall'ord's
Cleaners in
2012
In 1 erred
Maximum 1 IQ
Inferred
Maximum
Carcinogenic
Risk
Current
Indoor Air
ppbv
26.5
0.3
0.28 (8-hour)
0.02
9.3 x 10-7
Overnight
Indoor Air
ppbv
26.5
0.3
0.42
0.02
1.4 x 10"6
ppbv = parts per billion by volume (at 20° C and 1 atmosphere of pressure)
Hypothetical drinking water consumption. For the groundwater pathway, the PCE MCL of 5 pg/L
remains protective for both cancer and non-cancer effects, and is the legal criterion for compliance,
although the IROD did not select a clean-up level. Current groundwater results are shown in Table 7, in
Section 6.4.
6.3.3. Ecological Risk Review
An ecological risk assessment was conducted in 1994 prior to the IROD issuance and EPA determined
that there were no unacceptable ecological risks because there were no exposure pathways. There have
been no changes to exposure pathways since EPA issued the IROD, and there remain no potential
pathways to ecological receptors from the contaminants at the Site.
lew
Site-specific data collected since the last FYR were reviewed, with a focus on evaluation of progress
towards achieving the remedial action objectives set forth in the IROD. Specific groundwater data
reviewed and evaluated during this FYR included quarterly VOC data up to and including Fourth Quarter
2012, as well as groundwater gradient data from this time period. Additionally, aquifer hydraulic data and
extraction well data were reviewed from the Interim Groundwater Extraction Well Installation Report for
EW-02 published in September 2012. VOC data for soil gas were also reviewed.
The Technical Data Review Memorandum is included as Appendix E to this FYR report.
6.4.1. Groundwater Hydraulic Data
The primary goal of the hydraulic data evaluation was to determine the empirical capture zone of new
extraction well EW-02. The capture zone of this extraction well is directly applicable to the remedial
action objective of eliminating and containing the highest contaminant levels at the source beneath the dry
cleaners and beneath the former leaking sanitary sewer line near the cleaners (e.g., source control).
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Based on the December 2012 hydraulic data set, EW-02 impacts A-zone groundwater flow in the vicinity
of this well (see Figure 1 in Appendix E) since it draws water directly from this zone. There is little to no
influence of EW-02 on the deeper aquifer zones. Review of A-zone groundwater elevation differences
between EW-02 (39.75 ft) and the nearest monitoring well MW-04A (47.04 ft) located about 75 feet away
indicate a relatively steep cone of depression surrounding EW-02. Steep cones of depression correlate to
smaller radii of influence due to either low-permeability formations, inefficient extraction, or both. Recent
Site investigations determined the stratigraphy of the A zone in and around MW-04A and EW-02 to
possess finer-grained sediments which would cause the steeper cone of depression. This is also supported
by the low well efficiency of 33.5% estimated from constant-rate test data (EW-02 Installation Report,
URS September 2012).
The estimated empirical capture zone for EW-02 based on December 2012 groundwater elevation data is
depicted on Figure 3. At its maximum width in the upgradient direction, the capture zone is about 700 ft
wide. At the location of EW-02, the capture zone width perpendicular to flow is about 470 ft. The
distance between EW-02 and its downgradient stagnation point was estimated to be approximately 220 ft.
Figure 3 also shows the A zone plume map from August 2012 superimposed onto the potentiometric
contour map and the EW-02 capture zone. For comparison purposes, the capture zone determined for
EW-01R prior to shut-down is shown as well. It is evident that EW-02 is capturing more of the higher
dissolved-concentration PCE plume than EW-01R did. A portion of the higher concentration dissolved
PCE plume may be beyond the capture zone of EW-02 to the east; however, the capture zone does appear
to fully encompass the source area and thus well EW-02 achieves the source control RAO for the A zone.
Groundwater contours in the B zone indicate little to no capture of B zone groundwater and PCE from the
A zone-screened EW-02; however, since the highest PCE concentrations and the majority of contaminant
mass (e.g., the source) was contained within the A zone, and since the induced gradient from EW-02
operation acts to contain the source, the source control RAO is achieved.
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Figure 3. A Zone PCE Plume Map with Potentiometric Contour Map and Estimated Empirical Capture Zone for EW-Q2 (August 2012)
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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6.4.2.
Groundwater Analytical Data and Trends
PCE is the principal Site contaminant of concern (COC) due to its historical widespread presence in soil,
soil gas, and groundwater. The IROD noted an elevated toluene concentration of 13,200 (ig/L at well
MW-8A during the Phase III RI. However, toluene was not detected at MW-8A during the latest (August
2012) quarterly monitoring event and is below its Federal MCL of 1,000 (ig/L and California MCL of 150
ug/L at all wells. Other contaminants including trichloroethene (TCE), cis-l,2-dichloroethene (cis-DCE),
and chloroform have also been reported; however, these chemicals were either not detected above their
method detection limit or infrequently detected at concentrations below regulatory limits in Site samples.
Benzene and 1,2-dichloroethane have exceeded their respective MCLs at a fraction of the monitored wells
(6 wells and 1 well respectively during December 2012); however, the Fourth Quarter 2012 O&M Report
states that these detections are unrelated to Halford's Cleaners because these constituents have never been
detected in wells closest to the PCE source area. Uranium in groundwater is elevated at the Site, but is
naturally occurring and is not a Site COC. For these reasons, only PCE data is further evaluated herein
with respect to RAOs attainment.
Analytical groundwater data were reviewed for all on-site wells from which data were collected since the
last FYR. The nine wells installed in 2011 had only 4 sample results; two of the nine (MW-22A and MW-
27B) had no detections of PCE. There were a total of 38 monitoring wells (See Appendix E for a
complete listing). Of the 38, 20 were A zone wells, 13 were B zone wells, and 5 were C zone wells. Note
that the number of wells more than doubled between the last FYR and this review, from 15 to 40.
Additionally, data were reviewed for extraction well EW-01R, which ceased operation in August 2012.
Data from groundwater wells were statistically evaluated using the Mann-Kendall test for trend analysis.
The groundwater analytical data were divided into two areas: source area and dissolved-phase PCE
plume. The distinction was made to separately address the RAOs concerning source control and the
larger-scale, dissolved-phase groundwater contaminant plume.
The source area is considered the original location of highest soil and soil gas PCE concentrations
associated with PCE leaks from the dry cleaners and a private-to-public sanitary sewer connection behind
the cleaners. Source area groundwater wells are considered to be laterally within a loosely-defined 150
foot buffer from the soil and soil gas source areas, which consist of: MW-03A, MW-05A, MW-08A,
MW-09B, and EW-01R.
PCE trends at the source area wells between August 2008 and August 2012 generally were either stable or
decreasing. Trend test results are shown in Table 7. MW-08A showed no trend with respect to PCE
concentrations over this time period. Data from well MW-09B was determined to be stable. MW-03A and
MW-05A both showed decreasing trends. MW-03A exhibited a PCE concentration of 42 j^ig/L in August
2012, down from 1,300 (ig/L in August 2008. MW-05A exhibited a PCE concentration of 51 (ig/L in
August 2012, down from a high of 300 (ig/L in November 2009. MW-05A is the closest groundwater
monitoring location to the soil vapor extraction system that was expanded in 2008 and had a positive
impact on decreasing soil vapor PCE concentrations. Overall, PCE concentrations within source area A
zone wells are in the 5 to 50 (ig/L range. This is evidence of significant progress in the source area
through the withdrawal of source-area groundwater at former extraction well EW-01R. In the B zone
beneath the source area at well MW-9B, PCE currently fluctuates from about 4 to 14 (ig/L.
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Well II)
Aquifer /one
i»c i-: (.iiu/i )
August 2008-August 2012
TivihI Result
MW-03A
A zone
100
Decreasing
MW-05A
A zone
77
Decreasing
MW-08A
A zone
25
No Trend
EW-01R
A zone
NA
Decreasing
MW-09B
B zone
6.8
Stable
Notes:
PCE groundwater unit of measure is micrograms per liter (|ig/L)
Bold indicates value exceeds PCE MCL of 5 |ig/L
NA = not analyzed
PCE results at extraction well EW-01R showed a slow but steady, statistically significant decreasing trend
between January 2009 and August 2012. This well was sampled monthly as part of the groundwater
extraction and treatment system. PCE decreased during this period from almost 200 (ig/L to less than 100
(ig/L. EW-01R was shut off in August 2012, with A zone extraction shifting to the newly installed EW-02
located in a higher-concentration, downgradient portion of the plume.
The RAO of delineating the downgradient edges of the plume and preventing its further migration is
applicable to the dissolved-phase plume beyond the source area. Statistical trends were evaluated for
wells within the dissolved-phase PCE plume as part of this FYR to help assess plume migration. For the
dissolved-phase PCE plume, PCE was present above 5 (ig/L at 11 of 17 evaluated A zone wells not
considered source area wells. All A zone wells hydraulically upgradient of the source area had either
stable trend results (MW-07A, MW-11A, MW-15A) or decreasing trends (MW-01A, MW-02A). MW-
18A, near the downgradient extent but west of the plume axis, had a decreasing trend, although all results
were below 5 (ig/L since August 2008. Within the central to slightly distal portions of the PCE plume,
trends were variable, ranging from stable at MW-04A, no trend at MW-06A, and decreasing trend at
MW-1 OA. The A zone wells which define the PCE plumes lateral and distal extents had either stable
trend results (MW-13A), no trends (MW-16A, MW-17A, MW-19A, MW-23A), increasing trend (MW-
14A), or probably increasing trend (MW-20A). For the most part, these results demonstrate the A zone
plume is well bounded and not likely to migrate substantially beyond its current extent. One exception is
downgradient of MW-20A, which has exhibited a probably increasing trend. MW-16A and MW-21A are
positioned to further assess downgradient plume migration in the A zone.
PCE was present above 5 j^ig/L at 9 of 12 evaluated B zone wells not considered source area wells. The
Mann-Kendall trend test results indicated that all evaluated wells except MW-16B, MW-17B, and MW-
20B in the B zone were either stable or had no PCE trend over the period evaluated. MW-20B, located in
the approximate center of the B zone PCE plume, showed a decreasing trend. PCE at this well has
dropped from 160 (ig/L in November 2008 to 57 (ig/L in August 2012. PCE results at the most
downgradient B zone well (MW-25B) have been stable but have exceeded the MCL. Results showed an
increasing trend at MW-16B, located on the lateral-to-downgradient edge of the B zone PCE plume.
Recent PCE results from the last three quarters at well MW-16B have increased from about 2 to 24 j^ig/L:
therefore this is an area that should be closely watched during future sampling events. MW-17B showed a
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
21
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probably increasing trend. This well is also located in a lateral to downgradient direction from the plume
axis and should be closely watched. In light of the high concentrations experienced at MW-25B, and due
to the increasing trend at MW-16B and probably increasing trend at MW-17B, further delineation of the
B zone plume's distal extent appears warranted.
PCE was present above 5 (ig/L at only 2 of 5 evaluated C zone wells during the monitored period (MW-
04C and MW-20C), and at each of these wells only one sample was above 5 (ig/L during the period of
interest. All wells except one in the C zone showed either no trend (MW-04C, MW-16C, MW-20C) or
stable trend (MW-10C). MW-17C had a probably decreasing trend result. The limited contamination in
the C zone appears to be well delineated.
6.4.3. Groundwater Extraction and Treatment System Operational Data
EW-01R replaced EW-01 and was in operation from August 2006 to August 2012. EW-02 was installed
to more effectively capture and contain the highest concentration portion of the PCE plume, and
beginning in September 2012 EW-01R ceased operation and was replaced by operation of EW-02. Only
limited operational data exists for EW-02 due to its limited operation as reported in the Fourth Quarter
2012 monitoring report.
During this FYR reporting period (Fourth Quarter 2008 through Third Quarter 2012), the GWETS has
operated with an overall up time of 95 percent. The only significant prolonged system shutdown was
during late Second Quarter 2012 to early Third Quarter 2012, when the system was down to replace the
GWETS effluent pump. From August 2001 to September 2012, the GWETS had treated approximately
199 million gallons of water and removed approximately 518 pounds of PCE.
All GWETS effluent samples for this reporting period (Fourth Quarter 2008 through Third Quarter 2012)
met applicable discharge criteria for PCE. Discharge criteria were met for uranium except during the
Fourth Quarter 2010. At that time, resin was replaced in the primary ion exchange vessel because of a
measured increase in uranium to just above 20 pCi/L.
The groundwater extraction and treatment system is operating as designed and continues to make progress
at reducing contaminant mass within and downgradient of the source area.
6.4.4. Soil Vapor Analytical Data
All soil vapor data that has been evaluated is considered source area data, as the locations of all vapor
monitoring and extraction wells are within close proximity of the historical PCE release locations. Since
the last FYR, EPA has installed three SVE extraction wells SVE-02, SVE-03 and SVE-04, which are
currently operating. SVE-01 was disconnected from the SVE extraction system and converted to a vapor
monitoring well in 2008.
SVE data analyzed included that from the three SVE extraction wells from November 2008 to August
2012. Data evaluation also included nine vapor monitoring wells for the same period: SVE-01, DP-01A,
DP-01B, DP-05A, DP-05B, DP-06A, DP-06B, OSVE-10, and OSVE-11. Data were collected
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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approximately every quarter. Analytical results from the Fourth Quarter 2012 monitoring report are
included in Table 9.
Data from vapor monitoring wells were statistically evaluated using the Mann-Kendall test for trend.
Results from the vapor monitoring wells showed only one statistically significant trend, which occurred at
well OSVE-11. Data from OSVE-11 since March 2009 showed a decreasing trend. PCE soil vapor
concentration at OSVE-11 was exceptionally high in March 2009, with a concentration measured at
27,000 ppbv. One year later in March 2010, concentration had decreased to 130 ppbv, and by August
2012 the concentration had further declined to 21 ppbv. Four wells showed no trends (DP-01A, DP-01B,
DP-05B, and DP-06A) while two wells showed stable trends (SVE-01, OSVE-10). Two wells (DP-05A,
DP-06B), which contained more than 50% non-detects for PCE vapor, were not statistically evaluated.
Trend results are summarized in Table 8.
Results from the vapor extraction wells showed one decreasing trend (SVE-04), one probably decreasing
trend (SVE-02) and one well, SVE-03, with no trend. PCE concentrations in vapor from SVE-04 showed
a steady decline from 890 ppbv in November 2008 to 35 ppbv in August 2012. At SVE-02, PCE
concentration at the start of the data set was 14,000 ppbv. Concentration declined drastically between
2008 and 2009. In August 2012 the concentration was 380 ppbv. The initial high PCE concentrations
coupled with the decreasing and probably decreasing trends are evidence that the newly installed soil
vapor extraction wells removed the bulk of contaminant mass soon after they became operational. The
current low levels are associated with the continued operation of the SVE system.
Table 8. Most Recent PCE Results in Vaclc e Soil Vapor {December 2012)
Well II)
i»c i:
(pph\)
August 2008-August 2012
Trend Result
SVE-01
9.6
Stable
SVE-02 (extraction well, screened 7-12 ft bgs)
180
Probably Decreasing
SVE-03 (extraction well, screened 13-23 ft bgs)
130
No Trend
SVE-04 (extraction well, screened 28-38 ft bgs)
23
Decreasing
DP-01A
ND
No Trend
DP-01B
32
No Trend
DP-05A
ND
Insufficient Data
DP-05B
2.7
No Trend
DP-06A
43
No Trend
DP-06B
ND
Insufficient Data
OSVE-10
5.3
Stable
OSVE-11
19
Decreasing
Notes:
PCE soil vapor unit of measure is parts per billion by volume (ppbv)
ND = not detected at detection limits of 0.32 - 2.2 ppbv
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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6.4.5. Soil Vapor Extraction and Treatment System Operational Data
During this FYR reporting period (Fourth Quarter 2008 through Third Quarter 2012), the SVE system has
operated with an overall up time of greater than 99 percent. From June 2001 to September 2012, total
cumulative PCE mass removed through the SVE system was approximately 3,465 pounds. This amount
continues to be significantly greater than the total mass removed via the groundwater treatment system.
There was a transient spike in SVE system influent PCE concentration after new SVE wells SVE-02,
SVE-03, and SVE-04 came online in November 2008. Prior to system redesign, December 2007 data
revealed influent concentration of 54 ppbv, although measurements were as low as 4.4 ppbv in September
2007. In November 2008, after new wells were brought online, influent concentration was measured at
4,100 ppbv. This showed the new wells to be effective, at least initially, at extracting contaminant mass
from soil via the vapor pathway. Latest sampling results show treatment system influent PCE
concentrations ranging from 190 to 650 ppbv during Third Quarter 2012.
All SVE system effluent samples for this FYR reporting period (Fourth Quarter 2008 through Third
Quarter 2012) met applicable discharge criteria for PCE with the exception of Fourth Quarter 2009, and
First and Second Quarters 2010, when effluent concentrations ranged from 4 to 130 ppbv PCE. Vapor
phase GAC was changed out prior to Third Quarter 2010, and discharge criteria have been met since that
time.
Overall, more than 85% of PCE mass removed from the subsurface has been via the SVE system, while
less than 15% has been as a result of removal via the GWETS (about 3,500 lbs versus 520 pounds for
SVE and GWETS systems, respectively). Since about 2005, however, the percentage rates have been
reversed, with the bulk of mass removed via the GWETS. This is due to changes in extraction wells EW-
01R and EW-02 coming on line, and due to the quick path to asymptotic PCE vapor concentrations
resulting from the optimized SVE system.
6.4.6. Indoor Air
Indoor air sampling was conducted at source area businesses in February 2008 prior to optimization and
enhancement of the SVE system. PCE levels exceeding the RSL were found in two businesses, Halford's
Cleaners and The Parts House, closest to the PCE source. Concentrations ranged from 420 ppbv to 990
ppbv. Following SVE optimization, which added three extraction wells to the SVE system in immediate
proximity to the Halford's Cleaners building, indoor air sampling in August 2009 found marked
improvement in PCE concentrations (up to 90% reduction at some sample locations). However,
concentrations remained at unacceptable levels; in August 2009 results for PCE ranged from 7.5 ppbv to
500ppbv. Beginning in 2008, EPA carried out a series of vapor intrusion mitigation actions at the two
businesses. These preliminary actions included sealing floor cracks and closing off the old SVE system
indoor piping. A sub-slab depressurization system was installed in The Parts House in April 2010. In July
2010, PCE was discontinued as the dry cleaning agent in Halford's Cleaners. Subsequent indoor air
samples have been either non-detect (at most locations) to low for PCE (no greater than 1.4 ppbv PCE,
September 2011 at Halford's 941-IA-02 sample sub-location). The primary objective of the SVE system
is to eliminate the source for groundwater contamination by removing contaminant mass in the vadose
zone. A secondary objective of the SVE system - to remove contaminant mass in the upper vadose zone
(above 15 feet bgs) - has the added benefit of reducing human health risk due to shallow soil gas and
indoor air vapor intrusion. Table 9 shows the most recent PCE indoor air results.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Siimple l.ociilion
Suh-I.ociilion
I'C'K (pph\) 8-hr
I'C I! (ppb\) 24-hr
1 lalford's
941-IA-01
0.26
0.37
Halford's
941-IA-02
0.28
0.42
Parts House
939-IA-01
ND (<0.34)
0.30
Parts House
939-IA-02
ND (<0.34)
0.25
Parts House
939-IA-03
ND (<0.34)
0.25
Outdoors
OA-01
Not sampled
0.27
Notes:
RSL = 0.3 ppbv
PCE soil vapor unit of measure is parts per billion by volume (ppbv)
ND = not detected; (Detection limit shown in parentheses)
The combined actions of SVE optimization and enhancement, continued SVE operation (which
suppresses vapor intrusion into buildings), and vapor intrusion mitigation have reduced PCE indoor air
risk to acceptable levels based on recent monitoring.
spection
The FYR Site Inspection was conducted on February 21, 2013 and was led by USEPA and USACE
Sacramento District personnel (Marie Lacey, USEPA RMP, and Doug Mackenzie, respectively). Others
in attendance at the Site Inspection included Tamrah Headrick, lead operator of the treatment plant, Tim
Mathein, project engineer, Scott Dressier, project engineer, all with URS, the remedial contractor, and Jim
Rohrer, engineering geologist with California DTSC.
The scope of the site inspection included a site walk encompassing the various groundwater and soil
vapor treatment plant components (piping, sampling ports, tanks, vaults, storage vessels, air strippers,
carbon adsorbers, control panels, blower, moisture knockout drum, steel containers housing various
components, etc.), numerous site wells including monitoring wells, groundwater extraction wells, and soil
vapor extraction wells. On-site written documentation such as safety and health documentation, O&M
documents, and labeling were also reviewed. The condition of implemented physical ICs such as fencing
and signage were also observed.
Site inspection results indicated overall good condition of most aspects of the operating GWETS and SVE
remedial systems. CONEX containers, pumps, wellhead plumbing, electrical systems, pipelines, valves
and valve boxes were found to be generally in good condition. Monitoring wells observed during the Site
Inspection were found to be in good condition. Fencing and signage around the treatment plant systems
was found to be intact and in good condition. Minor deficiencies needing attention included adjustment of
a float valve inside the EW-02 well vault and missing locks to secure Wells MW-4A, MW-4B, and MW-
4C. These minor deficiencies have been repaired.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Based on observations and results from the Site Inspection, the Site Inspection team concluded that the
operational procedures in place are adequate to maintain the interim remediation systems in good working
order. Opportunities for optimization of groundwater/soil vapor monitoring are being implemented
including use of passive diffusion bag samplers for VOC samples, to be conducted during the First
Quarter 2013 monitoring event. Due to marked increase in expense to dispose of treated groundwater via
the city POTW, a recommendation was made in the checklist to consider alternate endpoints for treated
water such as injection back into the aquifer. Additionally, soil vapor rebound testing is being planned to
determine if shut-down or reduced or intermittent operation of the SVE system is appropriate.
A complete and comprehensive FYR Site Inspection Checklist is included as Appendix D.
•rviews
During the FYR process, interviews were conducted with parties involved with or impacted by the Site.
Interviews were conducted with Jeff Taylor, owner of The Parts House, and Jim Rohrer, Remedial Project
Manager for California DTSC, during the Site Inspection on February 21, 2013, and with City of Modesto
officials on April 15, 2013. The purpose of the interviews was to document the perceived status of the
Site and any perceived problems or successes with the phases of the remedy that have been implemented
to date. Interviews are summarized below and complete interviews are included in Appendix C.
Although Mr. Taylor had a good overall impression of the Site and remediation project, he expressed
concern that the process was taking longer than expected. He does not own the property his business
operates from and he was not aware of any future property ownership changes; he did indicate his
business has been there a long time. He indicated his business has been inconvenienced at times by after-
hours access to his building, and several Site-related activities including indoor air sampling and sub-slab
sampling as well as installation of two sub-slab depressurization systems. He is being reimbursed for
costs related to power consumption associated with the sub-slab depressurization system.
Mr. Rohrer indicated that he is the DTSC Project Manager for the Site, and that his role includes State
review of quarterly monitoring reports and other Site documentation. He also reviews O&M of the
groundwater treatment system since that component of the remedy has become the responsibility of the
State. Overall, Mr. Rohrer is unaware of any effluent discharge permit violations, and he believes he is
kept well informed about activities and progress at the Site. He inquired about soil vapor monitoring
procedures and recommended a California guidance document dealing with the subject.
As a whole, officials representing the City of Modesto had a positive impression of the Site, although the
interviewees indicated they had no routine communications or activities related to the Site. It was noted
on the interview form (Appendix C) that there was not a representative of the wastewater department
present - this department manages the permit for treated effluent to the sanitary sewer system. The City
of Modesto officials interviewed indicated the Modesto Site was not a high-profile issue for them, and
hence they felt they did not have the most up-to-date information on the Site. They were appreciative of
the interview meeting as a forum to learn more about recent happenings at the Site and to establish lines
of communication between the EPA and the City.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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itutional Controls
The Institutional Controls portion of the remedy selected in the IROD stated the following:
Institutional controls will include signing and fencing around the treatment area. These
institutional controls will be maintained for the duration of treatment, and the need for additional
institutional controls will be evaluated in the final remedy.
The Site Inspection checklist documents that the fencing surrounding the groundwater and SVE treatment
system components remains intact and in good condition. Photo documentation taken during the Site
Inspection (Appendix E) shows Site-related signage remains in place and in good condition.
In September 2012, a Land Use Environmental Restrictive Covenant (Land Use Covenant, or LUC) was
drafted. The LUC is to be placed on the properties of 939 & 941 McHenry Street, the locations of the
Parts House and Halford's Cleaners businesses. Once signed and recorded, the property owners and the
California Department of Toxic Substances Control will be the LUC signator parties. The provisions of
the Covenant will be enforceable by the EPA as a third party beneficiary. The LUC is necessary to
preclude residential use of the property given that hazardous substances will remain at the property
following completion of the interim remedial actions. The LUC also is necessary to preclude disruption of
the selected constructed remedies. The LUC is considered a proprietary IC.
Additionally, City of Modesto ordinance prohibits wells within city limits served by their public water
supply system for purposes other than groundwater monitoring or remedial treatment. This is considered a
governmental IC. The entire Modesto Superfund Site falls within city limits and therefore within this
provision. Well drilling permits for locations within Modesto city limits, normally obtained through the
Stanislaus County Department of Environmental Resources, are referred to and denied by the City of
Modesto.
The following table lists the ICs associated with areas of interest at the Site.
Table 10. IC Sumnu ble
Mcilisi
ICs ( ;illed lor in
(ho Decision
Doc ii moil (s
Impacted
I'a rcol(s)
IC Objects o
Instrument in
Place
Notes
Treatment
system water
and air
Yes (ROD refers to
these engineering
controls as IC's)
Not
applicable
Restrict public
access to treatment
facilities
Warning signs
and fencing
Remains in
place and is
maintained
Soil and
groundwater
No (Will be
included in final
ROD)
113-006-
036
Preclude
residential land
use and disruption
of remedies
LUC
In process of
being
finalized and
recorded
Groundwater
No (Will be
included in final
ROD)
Multiple
Prohibit private or
commercial wells
at Site
Governmental
IC
Remains in
place
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7. Technical Assessment
7,1 ?stion A: Is the remedy functioning as intended by the decision
documents?
In summary, the interim remedy is functioning as intended by the IROD. The following paragraphs
explain the rationale behind this conclusion.
7.1.1. Remedial Action Performance
New extraction well EW-02, operating continuously at 46 gpm, is near the maximum GWETS capacity of
50 gpm. This well is capturing more of the high-concentration PCE remaining in the A zone than was
captured by EW-01R, because it is more centrally located over the bulk of remaining dissolved phase
mass. Future quarterly groundwater monitoring results should further evaluate EW-02 effectiveness both
for hydraulic source control and reductions in concentrations throughout the plume.
It appears the PCE plume has been adequately characterized, with possible minor data gap areas
remaining within the A and B zones. The Fourth Quarter 2012 monitoring report recommends two wells
be installed and sampled in the A zone and 5 in the B zone to fully define the PCE plume extents.
Twenty-five groundwater monitoring wells have been installed since the last FYR, and the number of
wells now totals 40. In addition to the A zone, B and C aquifer zones have been characterized and
delineated with respect to the PCE plume. Much progress has also been made in investigating monitored
natural attenuation applicability.
Within the A zone, recent data demonstrate decreasing trends generally upgradient and within the source
area. Two locations show decreasing trends downgradient of the source area; however, a third location
(MW-20A) downgradient of the source area is probably increasing. Trends may vary in the immediate
future, as impacts from operation of EW-02 have yet to be realized in groundwater data. In monitoring of
B zone groundwater, careful observation of future quarterly data should be given to wells MW-16B and
MW-17B, where PCE concentrations have risen.
Optimization of the SVE system, by installing three new SVE extraction wells, has removed contaminant
mass from the soil in the source area and in lowered soil vapor concentrations. Based on Fourth Quarter
2012 data, PCE soil vapor exceeds 100 ppbv in just two active extraction wells, SVE-02 and SVE-03.
The operating SVE system contributes to vapor intrusion mitigation along with the sub-slab
depressurization system. The latest sampling indicates that indoor air PCE concentrations are at
protective for the current commercial use and operation. However, there is indication that vapor intrusion
may be occurring due to the low level of PCE detected in the overnight (24-hour) sample results. Future
actions will include monitoring of SVE operation, sub-slab pressures and concentrations, and indoor air
concentrations in affected structures.
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Both the GWETS and SVE system are currently operating and meeting applicable discharge requirements
with respect to VOCs, including PCE, and uranium.
While PCE remains above potentially applicable cleanup levels, the interim RAOs have been largely
achieved based on actions taken at the Site prior to and since the last FYR. Operation of the interim
remedy and associated monitoring will continue. The final Record of Decision will set new RAOs to
achieve applicable cleanup levels through a selected final remedy for the Site.
7.1.2. System Operations/O&M
Review of available documentation in the quarterly reports and information obtained during the Site
Inspection indicates that both the GWETS and SVE systems operate in an effective manner, with
necessary controls, routine performance monitoring, and preventative maintenance conducted to keep the
systems operating effectively in the future.
While there have been at times somewhat large variations in O&M costs in recent years, these variances
have been the result of additional plume investigations and characterization and corresponding additional
plume monitoring and interpretation efforts. For example, the number of wells sampled since the last
FYR has increased from 15 to 40, resulting in at least 100 extra samples for laboratory VOCs analysis per
year. Increased costs for this example would include not only sampling and analytical costs, but data
validation, interpretation, and reporting costs as well.
7.1.3. Opportunities for Optimization
Several opportunities exist to improve the performance and/or reduce costs of monitoring, sampling, and
treatment systems. First, a soil vapor rebound test is recommended and is currently being planned. Such a
test would evaluate whether shut-down of the SVE system, now showing asymptotically-low vapor
extraction levels, would be possible while still maintaining the protectiveness of the remedy with respect
to vapor intrusion risks. If the SVE system cannot be fully shut down, then lower vapor extraction rates or
operation of the SVE system in a pulsed mode might be effective, while reducing operating costs.
Secondly, after the PCE plumes in the A zone and B zone have been fully characterized, future
opportunities for monitoring network optimization by reducing the total number of wells for sampling
could be evaluated. Lastly, costs for discharge of treated groundwater to the city sanitary sewer have
considerably increased. Consideration and feasibility of discharging treated water back into the aquifer
should be evaluated as a cost-savings measure to the project.
7.1.4. Early Indicators of Potential Issues
At this time, there are no known early indicators of potential issues at this time that would affect
protectiveness.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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7.1.5.
Implementation of Institutional Controls and Other Measures:
Site signage and fencing are considered Site ICs and they remain in place and in good condition. They are
maintained at the Site as remediation treatment continues.
A Land Use Covenant was drafted in September 2012 to be placed on the properties of 939 & 941
McHenry Street, the locations of the Parts House and Halford's Cleaners businesses. The LUC was
necessary to preclude residential use of the property given that hazardous substances will remain at the
property following completion of the interim remedial actions. The LUC also was deemed necessary to
preclude disruption of the selected constructed remedies. The LUC is in draft form and has not received
final signature or recording.
Additionally, the City of Modesto has their own IC prohibiting wells within city limits served by their
public water supply system for purposes other than groundwater monitoring or remedial treatment.
These three ICs are adequate for the current Site conditions.
he expos ptk icit 1 i ( .
ion Objects ¦ ¦ ¦. T
net lection Still I/a
No ARARs or To-Be-Considered requirements have been revised, and there have been no changes in risk
assessment methodologies. PCE toxicity was revised in 2012 by EPA's IRIS, and is regarded as less toxic
than reflected in the Human Health Risk Assessment, IROD, or first FYR. (See Section 6.3.2 for details
of changes.) This change has not yet been reflected in a revised MCL, however.
In addition to the City of Modesto IC cited above, a land use covenant to be filed by the property owners
prohibits residential use and disruption of the selected remedy. No human health routes of exposures have
changed or new exposure pathways identified. Vapor intrusion is effectively being addressed at the site
because additional SVE wells have been installed and vapor intrusion mitigation has been implemented.
While PCE in groundwater remains above MCLs, the interim RAOs have been largely achieved based on
actions taken at the Site prior to and since the last FYR.
In consideration of the above, exposure assumptions, cleanup levels, ARARs, and Remedial Action
Objectives selected at the time of the remedy are still valid. As noted, PCE toxicity has been revised
downward and so has decreased the EPA indoor air screening level, but for groundwater the MCL
continues to guide cleanup.
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7,3, Question 1 her Information ight Thai Could
Call estion the Protectiveness of the Remedy?
No other information is known at this time that could call into question the protectiveness of the interim
remedy.
¦finical Assess .
The interim remedy of groundwater and soil vapor extraction, treatment, and discharge is functioning as
intended by the IROD. The goals of the interim remedy were to eliminate and contain the highest
contaminant levels at the source (source control) and to prevent potential exposure of human or
environmental receptors to PCE or other organic compounds released to the soil and groundwater. These
goals have largely been achieved, and EPA has made recent steady progress and is on track to select a
final remedy that will achieve appropriate groundwater cleanup levels. The operating SVE system may
contribute to vapor intrusion mitigation along with the sub-slab depressurization system. The current
assessment indicates that SVE may no longer be efficient in removing mass. The exposure assumptions,
cleanup levels, ARARs, and remedial action objectives selected at the time of the remedy are still valid
However, the toxicity reference dose has increased and carcinogenicity slope factors have decreased for
PCE. The changes in toxicity would not result in an increase in estimated risk, and therefore, would not
impact protectiveness. No other information has come to light that could call into question the
protectiveness of the interim remedy.
8. Issues
Table 11 summarizes current issues at the Modesto Groundwater Contamination Site that affect
current or future protectiveness of the remedy.
Table rrent Issues for the Modesto Groundwater Contamination Superfund Site
Issue
Affects Current
Protectiveness
(Yes or No)
Affects Future
Protectiveness
(Yes or No)
The SVE system may have reached its
remedial action objectives set forth in the
IROD; however, the system may be providing
protection for indoor air vapor intrusion, an
objective not originally considered in the
IROD.
No
Yes
The following minor issues do not affect protectiveness, but are included as items to be considered
for remedy improvement:
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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• The GWETS is not fully optimized.
• From an engineering perspective, the optimized and expanded (in 2008) SVE system has
reached a point of diminished returns on PCE mass extraction.
9. Recommendations and Follow-up Actions
Table 12 provides recommendations to address the current issues at the Modesto Groundwater
Contamination Superfund Site.
Table 12, Recommendations to Address Current Issues at the Modesto Groundwater
Contamination Superfund Site
Issiio
Kccommciuliilions/
hollow-I p Actions
Psirlj
Responsible
(hcrsighl
Aiicno
Milcsloni-
Diilc
AITecls
Proieclheness?
(Yes or No)
( II ITCH 1
I 'll III IV
The SVE system may
have reached its
remedial action
objectives set forth in the
IROD; however, the
system may be providing
protection for indoor air
vapor intrusion, an
objective not originally
considered in the IROD.
Continue to
monitor sub-slab
and indoor air PCE
concentrations
during cessation of
the SVE system to
ensure protective
indoor air levels are
maintained.
EPA
EPA
1/2015
No
Yes
The following are considerations that could reduce costs or potentially reduce costs while maintaining an
adequate level of Site monitoring:
• Evaluate returning treated water to the aquifer instead of discharging to the city POTW
• Evaluate whether a reduction in the number of sampled wells would be warranted once plumes are
fully characterized
In addition, the Land Use Covenant should be completed and recorded. Institutional controls should be
included in the final ROD. EPA will continue to monitor indoor air at the Halford's property.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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10. Protectiveness Statement
The interim remedy at the Modesto Groundwater Contamination Superfund Site is currently protective of
human health and the environment. Soil vapor extraction (SVE) and sub-slab vapor intrusion mitigation
have reduced indoor air PCE concentrations to be within acceptable levels, and there are no complete
receptor pathways for ingestion of impacted Site groundwater. To be protective in the long term, the
vapor intrusion pathway should be re-assessed when the SVE system is shut off.
11. Next Review
This Site requires ongoing FYRs as long as hazardous substances, pollutants, or contaminants are left on
site that do not allow for unrestricted use and unlimited exposure. PCE remains in Site groundwater above
its cleanup level, preventing unlimited use and unrestricted exposure. PCE in soil remains at
concentrations that are currently controlled by the SVE system and sub-slab vapor intrusion mitigation
system. The next Five-Year Review is required by September 2018, five years from the date of this
review.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Appendix A: List of Documents Reviewed
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
35
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Second Five Year Review - Modesto Groundwater Contamination Superfund Site
36
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List of Documents Reviewed
AMEC Geomatrix, Inc., (date unknown). Wall Repair Completion Report, Halford's Cleaner's
Modesto. (Based on reference in report, the date this report was published was no earlier than
May 4, 2009).
Innovative Technical Solutions, Inc., 2010. Testing and Analysis of Vapor Intrusion, Modesto
Groundwater Contamination Superfund Site, Modesto, California - Final Report December 2010.
MWH Americas, Inc. (MWH), 2010. Final Groundwater Remediation Optimization Methods,
Modesto Superfund Site, Modesto, California. March 26, 2010.
MWH, 2010. Quarterly Operations and Monitoring Report, Modesto Superfund Site, Modesto,
California, Fourth Quarter 2009. February 2010.
MWH, 2009. Quarterly Operations and Monitoring Report, Modesto Superfund Site, Modesto,
California, Third Quarter 2009. November 2009.
MWH, 2009. Quarterly Operations and Monitoring Report, Modesto Superfund Site, Modesto,
California, Second Quarter 2009. August 2009.
MWH, 2009. Quarterly Operations and Monitoring Report, Modesto Superfund Site, Modesto,
California, First Quarter 2009. May 2009.
MWH, 2009. Quarterly Operations and Monitoring Report, Modesto Superfund Site, Modesto,
California, Fourth Quarter 2008. March 2009.
MWH, 2008. Soil Vapor Extraction System Optimization and Enhancement Methods, Modesto
Superfund Site, Modesto, California. June 2008.
URS Group, Inc., 2013. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Fourth Quarter 2012, Modesto Groundwater
Superfund Site, Modesto, California. March 2013.
URS Group, Inc., 2012. Technical Memorandum - Updated Conceptual Site Model, Modesto
Groundwater Superfund Site. December 2012.
URS Group, Inc., 2012. Technical Memorandum - Draft EW-02 Installation and Aquifer Testing
Summary, Modesto Superfund Site, Modesto, California. September 20, 2012.
URS Group, Inc., 2012. Interim Groundwater Extraction Well Installation Report (Draft),
Modesto Groundwater Contamination Superfund Site, Modesto, California. September 2012.
URS Group, Inc., 2012. Technical Memorandum - Interpretation of Local Groundwater Level
Changes and Influences from City of Modesto Municipal Water Supply Wells Nos. 6 and 7. March
21,2012.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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URS Group, Inc., 2012. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Third Quarter 2012, Modesto Groundwater
Superfund Site, Modesto, California. November 2012.
URS Group, Inc., 2012. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Second Quarter 2012, Modesto Groundwater
Superfund Site, Modesto, California. August 2012.
URS Group, Inc., 2012. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, First Quarter 2012, Modesto Groundwater
Superfund Site, Modesto, California. May 2012.
URS Group, Inc., 2012. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Fourth Quarter 2011, Modesto Groundwater
Superfund Site, Modesto, California. February 2012.
URS Group, Inc., 2011. Letter Report, Groundwater Monitoring Well Installations, Modesto
Groundwater Superfund Site, Contract W91238-07-D-0006, Task Order 0004. December 5,
2011.
URS Group, Inc., 2011. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Third Quarter 2011, Modesto Groundwater
Superfund Site, Modesto, California. November 2011.
URS Group, Inc., 2011. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Second Quarter 2011, Modesto Groundwater
Superfund Site, Modesto, California. August 2011.
URS Group, Inc., 2011. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, First Quarter 2011, Modesto Groundwater
Superfund Site, Modesto, California. May 2011.
URS Group, Inc., 2011. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Fourth Quarter 2010, Modesto Groundwater
Superfund Site, Modesto, California. February 2011.
URS Group, Inc., 2010. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Third Quarter 2010, Modesto Groundwater
Superfund Site, Modesto, California. November 2010.
URS Group, Inc., 2010. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, Second Quarter 2010, Modesto Groundwater
Superfund Site, Modesto, California. August 2010.
URS Group, Inc., 2010. Quarterly Operations and Monitoring Report, Groundwater Treatment
and Soil Vapor Extraction Remediation Systems, First Quarter 2010, Modesto Groundwater
Superfund Site, Modesto, California. May 2010.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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US Army Corps of Engineers, Sacramento District, 2012. Data table summarizing groundwater
elevations at site monitoring wells collected on December 10, 2012 for Fourth Quarter 2012
monitoring. January 8, 2013.
US Environmental Protection Agency, 2012. Data table summarizing vapor intrusion data for
Halford's and Parts House, August 2009, June 2010, September 2010, November 2010,
September 2011, and February 2012, for Modesto Groundwater Contamination Superfund Site.
US Environmental Protection Agency, 2011. Modesto Groundwater NPL Site Vapor Intrusion
Removal Pollution/Situation Report #2 - Final. September 9, 2011.
US Environmental Protection Agency, 2008. First Five-Year Review Report for Modesto
Groundwater Contamination Superfund Site, Modesto California. September 2008.
US Environmental Protection Agency, 1997. Interim Record of Decision for the Modesto
Groundwater Contamination Site, Modesto, Stanislaus County, California. September 1997.
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Appendix B: Press Notices
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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rhynaa-Abriuais
/V[ IMtyU* -//) £$ /ufl
^sr"%
| A
\
liPfKpfr
La Agencia de Proteccldn Ambtental de los Estados Unldos (EPA)
ha comenzado !a segunda revisi6n de cinco aftos de acetones de
limpieza en el srtio de Superfondo de Agua Subterr&nea de Modesto
(sitio) en Modesto, California. La revisi6n evaiuarS si las acetones
de limpieza provisional para e! sitio protegen a la salud humana y
el medio arnbiente.
EL PROCESO DE REVISION
Le ley del Superfondo requlere at EPA evaluar la proteeddn de los
si stem as de rernediaci6n cada cinoo aflos hasta que el sitio sea
llmplado sufldentemente para permitir acceso sin restrlcclones.
Esta reviston de cinco afios, el segundo para e! sitio, evaluard la
proteccldn de !ss acdones de limpieza provisional en el sitio. Se
evsluard los plazos corto y largo de proteiccS6n a la saiud humana y
el medio amblente. Al finallzar la revision (30 de Septfembre, 20t 3),
una copla del reporte final senS puesta en el repositorlode Informadfin
local a continuackSn, y un aviso anurtciando la termtnscton de
!a revision de cinco a Acs se pubiscarS en el periddioo local. El
sitio continual slendo monltorizado y exSmertes quinquenates
contlnuarSn hasta que el sitio se ha llmplado sufldentemente para
permitir uso sin restricdones. Porque esto es un nemedto provisional.
EPA contlnuarS estudiando el sitio y svaluando otros posibtes
m^todos de limpieza. EPA planes publicar un Plan Propuesto pars
el comentario del publico en pocos aftos para sefeccfortar una
soluci6n final pars la limpieza de la contamlrtacldn y para msotver
todas las vlas posibtes de riesgo.
HISTORIA DEL SITIO
Una facifldad de ilmpieza en seco descargd aguas residuafes
conteniendo tetrachloroethylene (tamb!6n conocido como PCE
o "perc") en el agua subterranea por muchos aflos. Una cantidad
indeterminada de PCE fue lanzada en a! subsuelo y las aguas
subterr&neas. El sitio de Superfondo de Agua Subterrdnea de
Modesto fue colocado en la lista nacionsl de prioridades (NPL)
en 1989 para dlriglr la contamlnaci6n. Un Reglstro de Decision
provisional fue firmado en el afio 2000 que inlcid las acciones
de limpieza.
OBJETJVO DE LA LIMPIEZA
El objettvo de limpieza provisional establecldo para el sitio por ©!
Reglstro de Decision es limplar el PCE en el sgua subterranea.
Para lograr este objetivo, la EPA Instato un slstema de extraccidn
y tratamiento de las aguas subterrdneas y una extracd6n de
vapor del suelo (SVE) / slstema de tratamiento para tratar a los
contamlnado suetos.
PARTICIPAClON de la comunidad
Como parte de este proceso de revisldn qulnquenal, EPA realized
entrevistas en Modesto. Si usted conoce de cualquier problema o
tiene alguna preocupacidn con el remedto y desea partidpar en las
entre vistas, por favor contacts a Marie Lacey en EPA (infbrmacidn
de contacto mits aba jo). SI desea ser induido en nuestra lista de
correo y redbir futuras hojas de informaddn, por favor contacts a
Jackie Lane en EPA (informadon de contacto m&s abajo).
Pobreza infa
entre las m
tniin#l a
¦ ¦¦¦ ¦ ¦ ¦¦ lEJI l|K
os en Esta-
pakrezo pare
; mij efrcta-
rre las tta-
reveian
da en un
idn catiadi-
¦:j.Je toma
del Fondo de
,in> la In'i'rv
vela un
pobreza m-
ssarroliado".
a ser el pais
itemo bnno
I no de c
Jos Vme 5
trfi/ar af "*n
das por t 3
ciones di —
informed.
La siwac "™
articulo i ~
ense Oto
como ha
las Nacu
cis (Unit "
asorobro ~
fsntil en =
Estados
con may
del mundo. aparfce a! final de la
Usfa tomando en cuersta ima $erie
de ir.dicadores como et bienestar
materia!, la etfucacidrs. la saiud y la
seguridad, comportamiertos y ries-
go«. y is vivierda y ci medio ambi-
cnte.
El docurMTito inlCTnaafmf.l sefisla
que Washington orapa el h-igsr 26
entre las 20 naciones seleccitmadas,
por detris de Crrecia y justo por
encima de l itaania, Lelorris y Ru-
mania.
Precisa que en educaci6n los esta-
dounidetsses ocitpan el Uigar 27,
micntras en !o refererte a3 bieneslar
material csti en la plaw 26.
En este ultimo acipite, le investi-
gaci6ii se centra en las taws de po-
breza de cada pais y la brecha
reiativa entre el ingreso medio y los
mfk» ciaiificado-s como pobtw, lo
tjue evidencis que un 36 por ciento
de los nirios cstsjdoiuridenses se en-
c-ucntrai por debajo la if oca oficial
dc pobreza.
Aclara e! estudio que los paises con
los niveles mis altos de bienestar
infantit son los paises ndrdices y
Europa Occi pobreza infaritil.
Aunque en 2013 en bu discurso
sobre el Estado de la Uni6n, el
president? Bgreek Obama pmrno-
cion6 program as de edsicaciftn.
Global Research plantea que eso es
"demagogia vacia".
De hecho, la Casa Blanea encabera
un artaque hist6rico en la educaci6n
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
43
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sol His-
toric itfffftrvit.i&ft"'
What'# unfolding is bum®
titan a story about the 6*8
ofn raw# mining camp to
ih# .hottest, driest corner of
America. It to pan of a wid-
er debate about how lies! to
protect historic resources
•eras* a» Went lii an era of
limited and declinine eov-
•rnmenl resnurera.
that's mi mmu Prewar
Chiaro. president of the
Death Valley CoUSCTVimcy.
cited in i'Sptetlittt! why l»
believes Ryan should w
main private.
-The fact that it's ten in
private hand* rnlher than
part of the national mtrk
has tan er» or ih# things
thai has helped to prtMrve
it," said Cltiaro, Rut Tintn"s
Much has been lost ai-
ready. Out pxantDlc lis In-
side Death Valley National
Park, where someone lias
ctasete! Into t iwl wall in
in 'Tt"ni, i i., \m-ri-
em Indian petroglyphs. d*.
(iieteg she area fetirer.
In one of the most brazen
casts, thieves used power
saws. ladders and genera-
tors to steal centuries-old
petroflfplii fretti federal
land north of Bishop last
yew, Although the rock art
has teen recover*!, no ar-
rests have been made,
"It's akin to someone de-
facing part<*the Vatican «•
t* ,5 j»j-r vi i'n{, i^tant ar-
Hi< i j»t»u like the "Mona
tisa,'" s»ii Greg Haver-
iiie tl.S, Bureau of Land
Management. "A few
g»*iR.s»i-M«iefi Individ-
uals 4e#tr©yt• caretaker, • pnotlw
iiei fey U.S. B«»
•1 Tlnto. At I bough
jiMiftls are a-e-terio-
i.,,.* others are to gieas
shape. Kvwi the train en-
em* that onee carried tour-
ists is te-pt In working or-
der, though tt ts no longer
used.
"It's just like- going back
tn time," said UndaCreene-
swit.il, fotmsr chief of re-
sources management at
Death Valley' National
Fart, "Tilts place iiasream
ixstn tositttiy cared lor, 1ft
Two Piclllc Coast 8ona
executives, Steptim llaiMfir
Joined lilts National* Park
Service. As us nrsi two at-
rectors from HIT to- 1*33.
'hey called for protection of
D« ft Valley, which was de-
clared i- national monu-
ment by Pmident Herbert
Hoover in 1933. Itttecajmsa.
national park m im
Albright's datsghtt-r.
«]-year>old Marian
Seietiek, saM that Before
her fcllitf dittl ill 1887, he
told htr be -felt Ryan be-
toneed to the park.
"It wouM be rtileuliws
b* to bring it to." Seheaek
aaid. Hie whale (park) con-
cept came from borax.
When you don't inclaat
%»i>, ifs tliialuattag a big
pail of it,"
t muiiiK tjit- ittlAS i\(u « »>»»
to. wodwd a long time to get
8j-a« tn U»# park ttrvte.*
Since tlii-n, B» pel aiirt
Bte Tinto ti»-» rei«#lo«i
quiet, kindling interest,
sperulatlon *nd numerous
retjueats tor infentmttoii
from ttse tmmmm*
"If you go to tbiiti asking
for details, «Mn.g for foct>
- one of my (uastmns U,
where is lh#ir motif y actual-
ly raining twin! — their re-
sponse Is we don't hi* the
tin* ta dot Wtfc fou,"* said
Bruce of the Save Ryan
group.
L",
neat little mining town
thouSd be part of the
park service,**
it F1 ¦ ¦ y
¦* Au ni.'.-.u' 4" / i i:' (1 ii*Nst
, * r rc.'f - 1.7; (ji v-4- i ,-.i
1 ocnllv < ivju.-fl K-. <
. V T&i-v
(209) b38 8552
Owt»Isgnsl • Rapdr • 5*1
FREE IJTiMATLS 576-3171
GROUT
I
i§)
PU8UC NOTICE
Ur4!^ Sy
jnO*W»? C,"'>U'",T i'tWt rt»" """s Mori#""*c
psfl * mm mm®®' mm wmm&m ta mm Ft»vnr mmrn*
a 1
S*s iw« Sf0 >
knnwn « PC k V
m mktmm <»»**** ft# f»C£ was
M# wis m 8N» Umtmm Pf
m into »m MiK tto
IM (NPL) te 18» to A*
1 mmtrn %smm of Oacftior
-------
Appendix C: Site Inspection Interview
Reports
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
45
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Second Five Year Review - Modesto Groundwater Contamination Superfund Site
46
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INTERVIEW RECORD
Site Name: Modesto Groundwater Superfund Site
EPA ID No: CAD981997752
Subject: Second 5-yr review
Time:
Date:
Type: ~ Telephone
Location of Visit:
I I Visit O Other
On -Site, 941 McHenry Avenue, Modesto, CA
~ Incoming ~ Outgoing
Interviewer(s)
Name: Doug Mackenzie
Marie Lacey
Title: Environmental Engineer
Remedial Project Manager
Organization: Corps of Engineers
USEPA
Interviewee
Name: Jeff Taylor
Title: Business Owner
Organization: The Parts House
Telephone No: (209) 524-8800
Fax No:
E-Mail Address:
Street Address: 939 McHenry Avenue
Modesto, CA 95350
Summary Of Conversation
Interview Questions
1. What is your overall impression of the work conducted at the site to date? (general sentiment)
Mr. Taylor expressed that it was taking a long time. Other than that he had a good impression of the
project
2. What is the current and projected future ownership status of the site (Is the property for sale, has it
been sold, or subject to pending sale?)? What is the current zoning status of the property, and has that
changed in the last five years?
Mr. Taylor does not own the property, and he was not able to answer directly to the questions. He
has not heard anything about any change in ownership. He has operated the business for a long
time and the property has always been in the same use.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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3. What business impacts have you experienced related to the site within the past five years? How
many full-time and part time employees work in the building in which your business operates?
There have been several events of indoor air and sub-slab sampling as well as installation of two sub-
slab depressurization systems. Things go pretty well usually, but there was a time when the
contractor had requested some after-hours time which meant that he had to be there. Mr Taylor
would prefer that did not happen in the future.
There are two full-time employees.
4. Do you have any comments¦, suggestions; or recommendations regarding any aspects of the
Modesto GW Contamination Superfund Site?
Sometimes Mr. Taylor receives mail from vendors to the O&M contractor. He suggested that the
contractor might find a way to receive that correspondence directly.
EPA is having Mr. Taylor reimbursed for power cost associated with the sub-slab depressurization
system. In order for the funding to get to him in an accountable manner, Mr. Taylor has to submit a bill
to the O&M contractor. He requested more clarity on the process, and exactly what he needs to do.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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INTERVIEW RECORD
Site Name: Modesto Groundwater Superfund Site
EPA ID No: CAD981997752
Subject: Second 5-yr review
Time:
Date:
Type: ~ Telephone
Location of Visit:
I I Visit O Other
On -Site, 941 McHenry Avenue, Modesto, CA
~ Incoming ~ Outgoing
Interviewer(s)
Name: Doug Mackenzie
Marie Lacey
Title: Environmental Engineer
Remedial Project Manager
Organization: Corps of Engineers
USEPA
Interviewee
Name: James Rohrer
Title: Project Manager
Organization: California Dept. of
Toxic Substance Control
Telephone No: (916) 255-3709
Fax No:
E-Mail Address: jim.rohrer@dtsc.ca.gov
Street Address: 8800 Cal Center Drive
Sacramento, CA 95826
Summary Of Conversation
Interview Questions
3. What isyour current role as it relates to the site? What is your overall impression of the work
conducted at the site to date? (general sentiment)
Mr. Rohrer is the DTSC Project Manager for the Site. His role includes providing State review and
input to the project In addition, since O&M of the groundwater treatment system has become State
responsibility, he reviews that activity.
His overall impression of the project is favorable.
4. Have there been routine communications or activities (site visits¦, inspections, reporting activities; etc.)
conducted by your office regarding the site? If so, give purpose and results.
The State's contractor for O&M of the groundwater system performs weekly site visits and provides
quarterly reports to DTSC.
5. Are you aware if the site has been in compliance with permitting or reporting requirements?
Mr. Rohrer was not aware of any non-compliance with permitting and reporting associated with
effluent discharge.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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3. Have there been any complaints, violations¦, or other incidents related to the site requiring a
response by your office? If so, please give details of the events and results of the responses.
Mr. Rohrer has not heard of any complaints, violations, or other incidents.
6. Has any individual contacted you voicing questions or concerns about the site?
Mr. Rohrer did not recall any inquiries.
7. Do you feel well informed about the site's activities and progress?
Yes
8. Are you aware of any changes in State/County/Local laws and regulations that may impact the
protectiveness of the site?
No changes affecting operation of the remedy were recalled.
5. Do you have any comments; suggestions; or recommendations regarding the site's management,
operation, or any other aspects of the site
During the site visit Mr. Rohrer inquired about the procedures for sampling soil vapor monitoring wells.
California has a guidance document for sampling soil vapor, and it includes procedures for leak
detection that he recommended.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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INTERVIEW RECORD
Site Name: Modesto Groundwater Superfund Site
EPA ID No: CAD981997752
Subject: Second 5-yr review
Time:
Date:
Type: ~ Telephone Q Visit
Location of Visit:
City Office, 1010 Tenth Street, Modesto, CA
I I Other
~ Incoming ~ Outgoing
Interviewer(s)
Name: Doug Mackenzie
Marie Lacey
Title: Environmental Engineer
Remedial Project Manager
Organization: Corps of Engineers
USEPA
Interviewee
Name: Dennis Turner
Robert Christensen
Jesse Franco
Title: -Director of Public Works
- Senior Civil Engineer
-Assoc Civil Engineer
Organization: -City of Modesto
Dept of Public Works
-Utility Planning & Projects
- Utility Planning & Projects
Telephone No: (209)m577-5404
Fax No:
E-Mail Address: gnyhoff@modestogov.com
Street Address: lOlOTenth Street
Modesto, CA
Summary Of Conversation
Interview Questions
Note:_The interview was held in conjunction with a meeting with several City officials.
9. What isyour current role as it relates to the site? What is your overall impression of the work
conducted at the site to date? (general sentiment)
Business cards were handed out to clarify the positions of each attendee. The roles of the various
officials involved coordination of project activities that had impacts on their various organizations' area
of responsibility. In addition, they provide and receive information in regard to any issues of concern.
The overall impression of the site is positive.
10. Have there been routine communications or activities (site visits¦, inspections, reporting activities; etc.)
conducted by your office regarding the site? If so, give purpose and results.
None of the interviewees had routine communications or activities related to the site.
Note: There was not a representative of the wastewater organization at the interview. That
organization manages the permit for discharge of treated water to the sewer.
11. Are you aware if the site has been in compliance with permitting or reporting requirements?
Mr. Turner was not up to date on permit compliance. He will be checking with a point of contact.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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4. Have there been any complaints; violations; or other incidents related to the site requiring a response by
your office? If so, please give details of the events and results of the responses.
No complaints, violations, or other incidents were known.
5.Has any individual contacted you voicing questions or concerns about the site?
There had been an inquiry from a contractor working for another agency about collecting vapor
samples in the area. No specific detail of that inquiry was recalled.
6.D0you feel well informed about the site's activities and progress?
This site had not been a high profile issue for MPW, so there had not been a lot of information exchange.
The meeting was held to present information coming to light from recent investigations, and to
generally open lines of communication. The interviewees expressed appreciation for the meeting and
will be following up on information requests arising from the meeting. EPA provided the web site
where the City can access the reports generated through the project, including the quarterly monitoring
reports that they expressed interest in.
7.Areyou aware of any changes in State/County/Local laws and regulations that may impact the
protectiveness of the site?
No.
8.Doyou have any comments; suggestions; or recommendations regarding the site's management,
operation, or any other aspects of the site
Not at this time. The City representatives appreciated receiving point of contact information, which will
facilitate more communication.
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Appendix D:
Site Inspection Checklist
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Site Inspection Checklist
I. SITE INFORMATION
Site name: Modesto Groundwater Superfund
Date of inspection: 21 February 2013
Site
Location and Region: Modesto, CA, Region IX
EPA ID:
Agency, office, or company leading the five-year
Weather/temperature: Clear/ temperature in
review: US Army Corps of Engineers - Seattle
60's
District
Remedy Includes: (Check all that apply)
Landfill cover/containment Monitored natural attenuation
Access controls Groundwater containment
Institutional controls Vertical barrier walls
(irouiulwalcT pump and I real men I
Surface wilier colk-clion ;nul Irealment
Oilier Soil vapor exlraclion
Attachments: Inspection team roster attached
Silo map allachcd
II. INTERVIEWS (Check all that apply)
1. O&M site manager Tamrah Headrick
_Lead Operator _21 February 2013
Name
Title Date
Interviewed at site at office bv phone Phone no. (916)869-0043
Problems, suggestions: Report attached
2. O&M staff
Name
Title Date
Interviewed at site at office by phone Phone no.
Problems, suggestions: Report attached
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Local regulatory authorities and response agencies (i.e., State and Tribal offices, emergency
response office, police department, office of public health or environmental health, zoning office,
recorder of deeds, or other city and county offices, etc.) Fill in all that apply.
Agency California Dept. of Toxic Substances Control (DTSC)
Contact Jim Rohrer Engineering Geologist 2/21/2013 (916)
Name Title Date Phone no.
Problems; suggestions; Report attached:
Agency
Contact
Name
Problems; suggestions; Report attached:.
Title
Date
Phone no.
Agency
Contact
Name
Problems; suggestions; Report attached
Title
Date Phone no.
Agency
Contact
Name
Problems; suggestions; Report attached
Title
Date Phone no.
Other interviews (optional) Report attached.
Mr Jeff Taylor - Business Owner - Parts House . Interviewed on the same day as the site inspection.
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III. ON-SITE DOCUMENTS & RECORDS VERIFIED (Check all that apply)
1.
O&M Documents
O&Mmanual l\eadily available Up lo dale N/A
As-built drawings Kcntlilv available Up lo dale N/A
Maintenance logs Keadilv available Up lo dale N/A
Remarks: Maintenance logs are kept in possession of the lead operator. Copies are provided in
quarterly reports.
2.
Site-Specific Health and Safety Plan Keadily available Up lo dale N/A
Contingency plan/emergency response plan Keadilv available Up lo dale N/A
Remarks Last update on site, dated 2010.
3.
O&M and OSHA Training Records Readily available
Remarks: Training records kept at home office.
Up lo dale
N/A
4.
Permits and Service Agreements
Air discharge permit Readily available Up to date N/A
Effluent discharge Readily available Up to date N/A
Waste disposal, POTW Readily available Up lo dale N/A
Other permits Readilv available Up to date N/A
Remarks: Effluent discharged to Citv POTW. Report provided to Citv monthlv.
5.
Gas Generation Records Readily available Up to date N/A
Remarks
6.
Settlement Monument Records Readily available
Remarks
Up to date
N/A
7.
Groundwater Monitoring Records Readily available
Remark: Provided to EPA in quarterly reports.
Up lo dale
N/A
8.
Leachate Extraction Records Readily available
Remarks
Up to date
N/A
9.
Discharge Compliance Records
Air Readily available Up to date N/A
Water (effluent) Readily available Up to date N/A
Remarks_There is no air discharge permit, though substantive requirements are observed. SVE
discharge is sampled and system flow is logged. This information as well as water discharge
information is provided to EPA in quarterly reports.
10.
Daily Access/Security Logs Readily available Up to date N/A
Remarks: Contractor's routine site presence is one day per week The facility is locked all other
davs.
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IV. O&M COSTS
1.
O&M Organization
State in-house Contractor for State
PRP in-house Contractor for PRP
Federal Facility in-house Contractor for Federal Facility
Other_Facility is operated by a contractor under a Corps of Engineers contract. The Corps
provides the service to EPA through an interagency agreement.
2.
O&M Cost Records
Readily available Up to date
Funding mechanism/agreement in place
Original O&M cost estimate Breakdown attached
Total annual cost by (fiscal) year for review period if available
For 2008 $195,000
Date Total cost
For 2009 $321,000
Date Total cost
For 2010 $231,000
Date Total cost
For 2011 $273,000
Date Total cost
For 2012 $254,000
Date Total cost
3.
Unanticipated or Unusually High O&M Costs During Review Period
Describe costs and reasons: Groundwater monitoring costs increased after Fall 2008 due to
installation of 16 new wells. In 2009 implementation of changes to optimize the remedy occurred,
which resulted in some initial expense. In December 2009 the resin in the two ion exchange
vessels had to be disposed as low-level radioactive waste at significant additional cost.
Subsequently, the operators are initiating changeout sooner. Starting Fall 2007, sewer discharge
fee increased incrementally from approximately $1,600 per month to approximately $3,300 within
about two years. In January 2010 a new contract was awarded to a different contractor in a
competitive bid process.
V. ACCESS AND INSTITUTIONAL CONTROLS Applicable N/A
A.
Fencing
1.
Fencing Location shown on site maps (Inlcs secured N/A
Remarks: Fencing surrounds the GWTP and SVE sytems. It is intact and in good condition.
B.
Other Access Restrictions
1.
Signs and other security measures Location shown on site map N/A
Remarks: _There are signs on the fence around the treatment systems.
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c.
Institutional Controls (ICs)
1.
Implementation and enforcement
Site conditions imply ICs properly implemented Yes No
Site conditions imply ICs being fully enforced Yes No N/A
Tvpe of monitoring: fe.g.. self-reporting, drive bvl
Frequency
Responsible partv/agencv
Contact
Name Title Date Phone
N/A
Reporting is up-to-date Yes No N/A
Reports are verified by the lead agency Yes No N/A
Specific requirements in deed or decision documents have been met Yes No N/A
Violations have been reported Yes No N/A
Other problems or suggestions:
A land use covenant is currently in development. It restricts groundwater usage and what can be
built on the orooertv.
2.
Adequacy ICs are adequate ICs are inadequate N/A
Remarks:
D. General
1.
Vandalism/trespassing Location shown on site map No vnndnlism evident
Remarks: _Approximately 1-2 years ago a portable generator was stolen from within the locked
fence. There have been times when homeless people go over the fence, but no damage resulted.
Last time that was noticed was about 8 months aso.
2.
Land use changes on site N/A
Remarks: _The site is in suburban older commercial and residential area. That condition is
expected to continue into the foreseeable future.
3.
Land use changes off site N/A
Remarks:
VI. GENERAL SITE CONDITIONS
A.
Roads Applicable N/A
1.
Roads damaged Location shown on site map Konds adequate N/A
Remarksjnstallation of new SVE wells in 2008 resulted in re-paving of the alley on the north side
of Halford's. The previous paving was severely "alligatored" and had potholes.
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B.
Other Site Conditions
Remarks:
There is a low spot in the paving at the entrance to the GWTP. This leaves a pond that the
operators must deal with when entering.
VII. LANDFILL COVERS Applicable N/A
A.
Landfill Surface
1.
Settlement
Location shown on site map Settlement not evident
Areal extent
Depth
Remarks
2.
Cracks
Location shown on site map Cracking not evident
Lengths
Widths Depths
Remarks
3.
Erosion
Location shown on site map Erosion not evident
Areal extent
Depth
Remarks
4.
Holes
Location shown on site map Holes not evident
Areal extent
Depth
Remarks
5.
Vegetative Cove
Grass Cover properly established No signs of stress
NoTrees/Shrubs (indicate size and locations on a diagram)
Remarks
6.
Alternative Cover (armored rock, concrete, etc.) N/A
Remarks
7.
Bulges
Location shown on site map Bulges not evident
Areal extent
Height
Remarks
8.
Wet Areas/Water Damage Wet areas/water damage not evident
Wet areas
Location shown on site map Areal extent
Ponding
Location shown on site map Areal extent
Seeps
Location shown on site map Areal extent
Soft subgrade
Location shown on site map Areal extent
Remarks
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9. Slope Instability
Areal extent
Remarks
Slides
Location shown on site map No evidence of slope instability
B. Benches Applicable N/A
(Horizontally constructed mounds of earth placed across a steep landfill side slope to interrupt the
slope in order to slow down the velocity of surface runoff and intercept and convey the runoff to a
lined channel.)
1. Flows Bypass Bench
Remarks
Location shown on site map
N/A or okay
2.
Bench Breached
Remarks
Location shown on site map
N/A or
okay
Bench Overtopped
Remarks
Location shown on site map
N/A or okay
C. Letdown Channels Applicable N/A
(Channel lined with erosion control mats, riprap, grout bags, or gabions that descend down the
steep side slope of the cover and will allow the runoff water collected by the benches to move off of
the landfill cover without creating erosion gullies.)
Settlement
Areal extent_
Remarks
Location shown on site map
D epth
No evidence of settlement
Material Degradation Location shown on site map
Material type Areal extent
Remarks
No evidence of degradation
Erosion
Areal extent_
Remarks
Location shown on site map
D epth
No evidence of erosion
Undercutting
Areal extent
Remarks
Location shown on site map
D epth
No evidence of undercutting
Obstructions Type
Location shown on site map
Size
Remarks
No obstructions
Areal extent
Excessive Vegetative Growth Type
No evidence of excessive growth
Vegetation in channels does not obstruct flow
Location shown on site map Areal extent_
Remarks
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D. Cover Penetrations Applicable N/A
1.
Gas Vents Active Passive
Properly secured/locked Functioning Routinely sampled
Good condition
Evidence of leakage at penetration Needs Maintenance
N/A
Remarks
2.
Gas Monitoring Probes
Properly secured/locked Functioning Routinely sampled
Good condition
Evidence of leakage at penetration Needs Maintenance
N/A
Remarks
3.
Monitoring Wells (within surface area of landfill)
Properly secured/locked Functioning Routinely sampled
Good condition
Evidence of leakage at penetration Needs Maintenance N/A
Remarks
4.
Leachate Extraction Wells
Properly secured/locked Functioning Routinely sampled
Good condition
Evidence of leakage at penetration Needs Maintenance
N/A
Remarks
5.
Settlement Monuments Located Routinely surveyed
N/A
Remarks
E.
Gas Collection and Treatment Applicable N/A
1.
Gas Treatment Facilities
Flaring Thermal destruction Collection for reuse
Good condition Needs Maintenance
Remarks
2.
Gas Collection Wells, Manifolds and Piping
Good condition Needs Maintenance
Remarks
3.
Gas Monitoring Facilities [e.g., gas monitoring of adjacent homes
3i" buildings)
Good condition Needs Maintenance N/A
Remarks
F.
Cover Drainage Layer Applicable N/A
1.
Outlet Pipes Inspected Functioning N/A
Remarks
2.
Outlet Rock Inspected Functioning N/A
Remarks
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G. Detention/Sedimentation Ponds Applicable N/A
1. Siltation Areal extent
Depth N/A
Siltation not evident
Remarks
2. Erosion Areal extent
Depth
Erosion not evident
Remarks
3. Outlet Works
Functioning
N/A
Remarks
4. Dam
Functioning
N/A
Remarks
H. Retaining Walls
Applicable
N/A
1. Deformations
Location shown on site map Deformation not evident
Horizontal displacement
Vertical displacement
Rotational displacement
Remarks
2. Degradation
Location shown on site map Degradation not evident
Remarks
I. Perimeter Ditches/Off-Site Discharge
Applicable N/A
1. Siltation
Location shown on site map Siltation not evident
Areal extent
Depth
Remarks
2. Vegetative Growth
Location shown on site map N/A
Vegetation does not impede flow
Areal extent
Type
Remarks
3. Erosion
Location shown on site map Erosion not evident
Areal extent
Depth
Remarks
4. Discharge Structure
Functioning
N/A
Remarks
VIII. VERTICAL BARRIER WALLS Applicable N/A
1. Settlement
Location shown on site map Settlement not evident
Areal extent
Depth
Remarks
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2.
Performance MonitoringTvpe of monitoring
Performance not monitored
Frequency Evidence of breaching
Head differential
Remarks
IX. GROUNDWATER/SURFACE WATER REMEDIES Applicable N/A
A.
Groundwater Extraction Wells, Pumps, and Pipelines Applicable N/A
1.
Pumps, Wellhead Plumbing, and Electrical
Good condition All requiredwells properly operation Needs Maintenance N/A
Remarks_EW-2 was installed in summer 2012. The float valve that senses water level in the well
vault needs adjustment. It is currently set too low, and will trigger nuisance shut-downs in the
event there is even minor leakage of rain water into the vault.
2.
Extraction System Pipelines, Valves, Valve Boxes, and Other Appurtenances
Good condition Needs Maintenance
Remarks
3.
Spare Parts and Equipment
Readily available Good condition Requires upgrade Needs to be provided
Remarks_The systems are contained in CONEX freight containers. There is not much room for a lot
of spare parts and equipment. The operators carry a lot of what they need in the utility vehicle
they drive to the site. There have not been significant impacts due to lack of spare
parts.
B. Surface Water Collection Structures, Pumps, and Pipelines Applicable N/A
1.
Collection Structures, Pumps, and Electrical
Good condition Needs maintenance
Remarks
2.
Surface Water Collection System Pipelines, Valves, Valve Boxes, and Other Appurtenances
Good condition Needs maintenance
Remarks
3.
Spare Parts and Equipment
Readily available Good condition Requires upgrade Needs to be provided
Remarks
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c.
Treatment System Applicable N/A
1.
Treatment Train (Check components that apply)
Mclals removal Oil/water separation Bioremediation
Air stripping Carbon adsorbers
Fillers Bap filters for solids removal
Additive (e.g.. chelation agent, flocculent] Scale control
Others: Metals removal is ion exchange to remove uranium fnaturallv occurring]
(iood condition Needs Maintenance
Sampling pol ls properly marked and lunclional
Sampling/maintenance log displayed and up to date
l-tiuipmcnl properly identified
Ouantitv of groundwater treated annuallv: 25 MG
Ouantitv of surface water treated annuallv:
Remarks: Svstem treats 50 gpm. and uptime is approximately 95%
2.
Electrical Enclosures and Panels (properly rated and functional)
N/A (iood condition Needs Maintenance
Remarks
3.
Tanks, Vaults, Storage Vessels
N/A (iood condition I'roper secondary conlainmenl Needs
Maintenance
Remarks_The CONEX container housing the system is on top of a containment structure. The floor
of the system has several holes that allow any leakage from system to drain into the containment.
Level controllers in the containment trigger pumping of the captured water to the system for
treatment.
4.
Discharge Structure and Appurtenances
N/A (iood condition Needs Maintenance
Remarks
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5. Treatment Building(s)
N/A Good coiulilion (esp. rool and doorways) Needs repair
Chemicals and equipment properly stored
Remarks_CONEX has been recently painted. De-scalant chemical is the only chemical product on
site. It is within the system containment.
6. Monitoring Wells (pump and treatment remedy)
Properly secured/locked I'unclioning Koulindy sampled Good coiulilion
All required wells located Needs Maintenance N/A
Remarks: _The wells are sampled quarterly. To date, 15 of the 40 wells have dedicated purge
pumps and the remainder have been sampled by standard purge-and-bail. Next quarter will begin
sampling with passive diffusion bags. New well caps have recently been installed. Wells 4a,b,c
were found without locks. Steel traffic lids were securely
bolted.
D. Monitoring Data
1. Monitoring Data
Is routinely submilU'd on lime Is ol acceptable qualily
2. Monitoring data suggests:
This discussion is provided in five-year review report text.
D. Monitored Natural Attenuation N/A
Monitoring Wells (natural attenuation remedy)
Properly secured/locked Functioning Routinely sampled Good condition
All required wells located Needs Maintenance N/A
Remarks
X. OTHER REMEDIES
Soil Vapor Extraction
The SVE treatment system is located adjacent to the groundwater treatment system, also within the
fence. A separate CONEX container houses the blower, moisture knockout drum, piping, and system
control panel. The vapor is treated through a carbon filter located outside the CONEX. Spare parts,
materials, and some documents are located in this system container. The system was running, and
no issues were noted. Three extraction wells, screened at different depths, are located at the
northwest corner of Halford's. These wells were all on line. The single original extraction well is
located approximately 50 feet to the west and it is currently off-line. No issues noted with the
extraction wells.
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XI. OVERALL OBSERVATIONS
A.
Implementation of the Remedy
Describe issues and observations relating to whether the remedy is effective and functioning as
designed. Begin with a brief statement of what the remedy is to accomplish (i.e., to contain
contaminant plume, minimize infiltration and gas emission, etc.).
The interim remedy was intended to eliminate and contain the highest contaminant levels at the
source, while preventing exposure to contaminated groundwater. The interim remedy has
significantly reduced PCE concentrations in the vicinity of extraction wells 1 and 1R, where
concentrations were highest. Monitoring wells 8a,5a,3a located near Halford's have all shown
significantly decreased_PCE concentrations. Concentrations at well 4a further downgradient have
varied widely, but have continued to show values at approximately l,000ug/L. Extraction well 2
was installed in that area in Summer 2012. The single sampling event at MW-4a since the startup
of extraction well 2 shows a result of 130 ug/L. There is no evidence of current exposure to
contaminated water from the
site.
B.
Adequacy of O&M
Describe issues and observations related to the implementation and scope of O&M procedures. In
particular, discuss their relationship to the current and long-term protectiveness of the remedy.
_The interim remedy is effective at reducing concentrations at source areas, which is the
intent of the interim ROD. The operational procedures are adequate to maintain the
sytems in good working order. For long term protectiveness, the final remedy must cover
a broader scope. The PCE plume in groundwater is too large to remediate by source area
control alone. As identified in the previous 5-year review, the interim ROD did not
address the vapor intrusion pathway. The vapor intrusion pathway has been undergoing
investigation and mitigation in the last 5 years. The final ROD must clarify whether the
vapor intrusion pathway requires further mitigation, and if so, establish the remedial
action.
C.
Early Indicators of Potential Remedy Problems
Describe issues and observations such as unexpected changes in the cost or scope of O&M or a high
frequency of unscheduled repairs that suggest that the protectiveness of the remedy may be compromised in
the future.
There have been no early indicators of problems with the interim remedy that affect protectiveness.
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D. Opportunities for Optimization
Describe possible opportunities for optimization in monitoring tasks or the operation of the remedy.
Use of passive diffusion bags for groundwater sampling has been identified and will be implemented in the
next monitoring event.
A soil vapor rebound test is in planning stages to determine whether shut-down of the SVE system is viable.
If it is shown that the SVE system provides control on vapor intrusion in Halford's, A reduced level of
extraction should be considered to reduce O&M cost.
As the site characterization is finalized, the groundwater sampling program could be optimized through
reducing the number of wells sampled as well as the frequency of sampling.
Discharge of treated groundwater to sewer has become considerably more expensive. Discharge back into
the aquifer would eliminate discharge fees and could potentially eliminate the need for removal of uranium,
another significant O&M cost. This is being considered in the feasibility study.
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GWTP CONEX container inside fence. Warning signs on fence.
Doorway to GWTP. Vapor Phase GAG unit located outside.
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U.S. EPA
Modesto Groundwater Superfund Site
CAUTION UNAUTHORIZED PERSONS KEEP OUT
This property contains hazardous materials which may be harmful to your
health. Do not trespass.
For further information call the U.S. Environmental
Protection Agency; 1-800-231-3075.
PRECAUCJON - PROHIBIDA LA ENTRADA
Esta propiedad contiene materials contaminados que pueden causar dano a su salud.
Para mas intormacinn Name a la Agencia para la Proteccion
a nhiaotal tfe los Eslados Unidos de Norte America al teletono; 1-800-231-3075
U.S. Environmental Protection Anericy
Region IX
75 Hawthorne Street
San Francisco, CA 94105
O
02-21.2013 11:44
Information posted on fence.
Looking east toward McHenry Avenue. Halford's Cleaners on the right
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Ion Exchange vessels
Air Stripper. Gaskets between trays had recently been replaced. No leaks observed.
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Bag filters pre-air stripper
Influent tank. Sequestering agent in yellow container.
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GWTP Control system panels
Analytix AN-310H
^ _ t Water
Scale Control In
Remediation of Ground Water
tlaiArd Statement:
s\, Handling SI "lament . we-oll* KWl
ntei* gloves iiiul al";" * **,^1 IW
vulBfeehmsd wbeo «H ta *'
Sequestering agent to control scale.
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rarn
Sample tap - post GAC, pre ion exchange
Inside the GWTP CONEX container.
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¦i
,' WMMjtatefal and Raw Matgrials listings
ListaiJ
^l"2Ud,nB liqu,ds' slut^es °r mM9 9«»»ted antf m
^9ed ,n|0 the City Sewer Collection System
Manifest or
ftscept'' i^.m
!i?r". ?*** ?w<*
-***ory locmed InThl r ?Va 5lt® ^ dCtacf1 a <*
I County Hazardous Materials Business Plan
^gtg_pf_Ma}eriai
itaSbd,'* AN-310H
Quantity
,26 gallons
Inventory of materials posted
Emergency contacts posted
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Vapor Phase GAC
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Influent structure on left Separate power meters for GWTP and SVE
Inside SVE container. Manometer for vacuum readings. Air conditioner to protect control system
from summer heat
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SVE blower and moisture knock-out vessel
GWTP on the right, SVE on the left.
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Original SVE well under metal plate in foreground. New SVE wells off the corner of Halford's in the
background.
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New SVE wells
SVE extraction well #2
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Appendix E: Technical Data Review
Memorandum
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MEMORANDUM FOR RECORD
SUBJECT: Technical Data Review, Modesto Groundwater Contamination Superfund Site, Second Five-
Year Review
PREPARED BY: Jefferey Powers, U.S. Army Corps of Engineers, Seattle District
DATE: 22 February 2013 (Revised 1 July 2013)
Introduction, Purpose, and Background
The U.S. Army Corps of Engineers, Seattle District (USACE) is assisting the U.S. Environmental Protection
Agency, Region 9 (USEPA) with the completion of the Second Five-Year Review (FYR) for the Modesto
Groundwater Contamination Site (e.g., the Site). This technical data review memorandum documents
the review and evaluation of groundwater, soil vapor, groundwater extraction and treatment system,
and soil vapor extraction and treatment system operational data in support of the protectiveness
determination to be made in the FYR report.
In 1997 an interim, rather than final, Record of Decision (IROD) was established for the Site because of
uncertainties in remediation technology capabilities, and because further delineation of the
downgradient and vertical extent of the contaminant plume was needed. The interim remedial action
objectives (RAOs) of the IROD were:
• Eliminate and contain the highest contaminant levels at the source (source control),
• Prevent exposure to contaminated groundwater, above acceptable risk levels, to protect human
health and environment,
• Minimize the impact of interim cleanup measures to the community,
• Collect data to determine if Federal and State requirements can be met throughout the aquifer,
and
• To delineate more clearly the downgradient edges of the plume and to prevent its further
migration.
Subsequent to the First FYR in 2008, and in part to address issues brought forward both prior to and
during the First FYR, additional characterization and interim remedy work took place. With respect to
groundwater, further characterization was conducted to better define the lateral and vertical dissolved-
phase groundwater plume extents. The groundwater monitoring well network was expanded in 2008
and again in 2011 by the addition of 16 and 9 wells, respectively. A new groundwater extraction well
(EW-02) was installed and brought online in September 2012 to better address the source control RAO
by capturing not only source area groundwater but also the plume's highest concentration area located
farther downgradient than that being captured by EW-01R. With respect to soil vapor, a soil vapor
extraction (SVE) optimization plan was implemented in November 2008, which included installation of
three new SVE wells SVE-02, SVE-03, and SVE-04 in the source area to replace SVE-01 previously
converted from a vapor extraction well to a vapor monitoring well.
This memorandum addresses the interim RAOs dealing with Site subsurface data collected to date, with
an emphasis on data collected between the First FYR and this, the Second FYR. The applicable interim
RAOs are the first, second, fourth, and fifth bulleted items listed above. Note that the interim remedial
actions were intended as a source control/containment measure to prevent unacceptable health risks to
human receptors in the short term, and were not designed to clean up the Site to levels allowing for
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unlimited use/unrestricted exposure. The data was reviewed in this context. The memorandum also
assesses operational data associated with the interim remedial systems to ensure they are operating as
intended.
Data Utilized
The period of time for which data were evaluated as part of this review was August 2008 through
August 2012 for analytical data, and December 2012 for groundwater hydraulic data. August 2012 and
December 2012 correspond to the latest quarterly Site monitoring data available for analytical and
water level data, respectively.
Data were obtained from the following sources in support of the evaluation:
• Fourth Quarter 2009 Quarterly Operations and Monitoring Report for Modesto Superfund Site
(Montgomery Watson Harza; February 2010) - Note this report contains all historical analytical
and hydraulic data up to and including November 2009 monitoring event,
• First, Second, Third, and Fourth Quarter 2010 Quarterly Operations and Monitoring Reports for
Modesto Superfund Site (URS; May, August, November 2010 and February 2011),
• First, Second, Third, and Fourth Quarter 2011 Quarterly Operations and Monitoring Reports for
Modesto Superfund Site (URS; May, August, November 2011 and February 2012),
• First, Second, and Third Quarter 2012 Quarterly Operations and Monitoring Reports for
Modesto Superfund Site (URS; May, August, and November 2012),
• Spreadsheet containing unpublished groundwater elevation data for Fourth Quarter 2012,
Modesto Site (USACE Sacramento District, January 2013), and
• Interim Groundwater Extraction Well Installation Report (Draft), Modesto Groundwater
Superfund Site, Modesto, California (URS, September 2012).
PCE is the Site contaminant of potential concern (COPC) due to its historical widespread presence in soil,
soil gas, and groundwater. The IROD noted an elevated toluene concentration of 13,200 ug/L at well
MW-8A during the Phase III Rl, and this chemical is listed as a "Site contaminant of concern" in Table B1
of the latest quarterly O&M report (URS 2012). However, toluene was not detected at MW-8A during
the latest (August 2012) quarterly monitoring event. Other contaminants including trichloroethene
(TCE), cis-l,2-dichloroethene (cis-DCE), and chloroform have also been reported; however, these
chemicals were either not detected above their method detection limit or infrequently detected at
concentrations below regulatory limits in Site samples. Uranium in groundwater is elevated at the Site
but is naturally occurring and is not a Site COPC. For these reasons, only PCE is further evaluated as a
COPC in this memorandum.
Trend Evaluation Method
Trends in analytical monitoring data were evaluated using the Mann-Kendall test, a non-parametric
statistical procedure that is well suited for analyzing trends in data over time. This test does not require
any assumptions as to the type of statistical distribution of the data (e.g. normal, lognormal, etc.) and
can be used with data sets which include irregular sample intervals and missing data. Trend results are
reported as one of six possibilities: increasing, probably increasing, no trend, stable, probably
decreasing, or decreasing.
Increasing trends are the result of the Mann-Kendall Statistic (s) being greater than 0 and >95%
confidence in trend. Probably increasing trends result when s>0 and the confidence in trend is between
90-95%, while no trend is the result of when s>0 and confidence in trend is <90% or s<0, confidence in
trend is <90%, and the coefficient of variation (COV) is >1. Trends are determined to be stable when
s<0, confidence is <90%, and COV
-------
95%, while they are determined as decreasing when s<0 and confidence is >95%. Note that trend
analysis summary tables are included at the end of this memorandum for groundwater and soil vapor
well data.
The resultant trend assignment is summarized in the following table.
Trend Status
Mann-Kendall
Confidence (1
Coefficient of Variation
Statistic (s)
minus P-value)
(COV)
Increasing
>0
>95%
Value not relevant
Probably Increasing
>0
90-95%
Value not relevant
No Trend
>0
<90%
Value not relevant
No Trend
<0
<90%
>1
Stable
<0
<90%
<1
Probably Decreasing
<0
90-95%
Value not relevant
Decreasing
<0
>95%
Value not relevant
Groundwater
Hydraulic Data
The primary goal of the hydraulic data evaluation was to attempt to determine the empirical capture
zone of new extraction well EW-02 and to compare to the most recent plume map to see how well the
plume is being captured. To conduct such an evaluation, the latest published results of the remedial
contractor, from the Third Quarter 2012 monitoring event in August 2012, was not adequate because
equilibrium groundwater flow conditions had yet to be established for EW-02. This is because EW-02
was installed in June 2012, but not brought online until September 2012. Approximately three months
later in December 2012, the first groundwater elevation measurements were collected subsequent to
full-time operation of EW-02. The groundwater potentiometric map was expected to change to show
capture associated with EW-02 as opposed to EW-01R based on the published results from August 2012.
Modesto municipal wells currently operating in the vicinity of the Site continue to impart an effect on
the Site's hydraulic gradient. There are reportedly as many as 26 municipal wells within a one mile
radius of the Site. Modesto Municipal Wells 06 and 07 are located approximately 900 and 600 feet
southeast and southwest, respectively, from the downgradient plume extent.
Based on the December 2012 hydraulic data set, the horizontal groundwater gradient computed for the
A-zone away from the direct influence of EW-02, and considering municipal well influences, was 0.0017
ft/ft to the southeast, and is consistent with previously measured gradient conditions. For the B-zone it
was 0.0011 ft/ft to the southeast. Since EW-02 had little to no influence on B-zone conditions as
evidenced by the lack of deflection of the groundwater elevation contours around this well, C-zone
gradients were not determined for this evaluation.
EW-02 impacts A-zone groundwater flow in the vicinity of this well, as shown in Figure 1, since it draws
water directly from this zone. It has been assumed EW-02 was continuously pumped at 46 gallons per
minute (gpm) based on recommendations in the EW-02 installation and testing report (URS, September
2012). Figure 2 shows that there is little to no influence of EW-02 on the deeper aquifer zones. Review
of A-zone groundwater elevation differences between EW-02 (39.75 ft) and the nearest monitoring well
MW-04A (47.04 ft) located about 75 feet away indicate a relatively steep cone of depression
surrounding EW-02. Steep cones of depression correlate to smaller radii of influence due to either low-
permeability formations, inefficient extraction, or both. Recent Site investigations determined the
stratigraphy of the A zone in and around MW-04A and EW-02 to possess finer-grained sediments which
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
85
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would cause the steeper cone of depression. This is also supported by the low well efficiency of 33.5%
estimated from constant-rate test data (EW-02 Installation Report, URS September 2012).
If the water table were flat, an extraction well's capture zone would be circular and would be equal to its
cone of depression. Because the water table slopes downward to the southeast, the capture zone of
EW-02 is elongated, extending slightly downgradient of the pumping well and extending to the nearest
groundwater divide (assuming steady-state conditions) in the upgradient direction. The estimated
empirical capture zone for EW-02 based on December 2012 groundwater elevation data is depicted on
Figure 1. At its maximum width in the upgradient direction, the capture zone is about 700 ft wide. At
the location of EW-02, the capture zone width perpendicular to flow is about 470 ft. The distance
between EW-02 and its downgradient stagnation point was estimated to be approximately 220 ft.
Figure 1 also shows the latest plume map (August 2012) superimposed onto the potentiometric contour
map and the EW-02 capture zone. For comparison purposes, the capture zone determined for EW-01R
prior to shut-down is shown on the figure as well. It is evident that EW-02 is capturing more of the
higher dissolved-concentration PCE plume than EW-01R did; however, the easternmost portion of PCE
greater than 1,000 ug/L may still not be captured. The EW-02 capture zone extends approximately 175
feet east of EW-02, while the 1,000 ug/L PCE contour extends about 475 feet east of this well. However,
the capture zone does appear to fully encompass the source area and thus well EW-02 achieves the
source control RAO for the A zone.
Analytical Data
Analytical groundwater data were reviewed for all on-site wells from which data were collected during
the period of review. The nine wells installed in 2011 had only 4 sample results; two of the nine (MW-
22A and MW-27B) had no detections of PCE. The 38 monitoring wells for which data were evaluated
were: monitoring wells MW-01A, MW-02A, MW-03A, MW-04A, MW-05A, MW-06A, MW-07A, MW-
08A,MW-10A, MW-11A, MW-12A, MW-13A, MW-14A, MW-15A, MW-16A, MW-17A, MW-18A, MW-
19A, MW-20A, MW-23A, MW-04B, MW-09B, MW-10B, MW-16B, MW-17B, MW-19B1, MW-20B, MW-
24B, MW-25B, MW-26B, MW-27B, MW-28B, MW-29B, MW-04C, MW-10C, MW-16C, MW-17C, and
MW-20C. Of the 38, 20 were A zone wells, 13 were B zone wells, and 5 were C zone wells. Note that
the number of wells more than doubled between the last FYR and this review, from 15 to 40.
Additionally, data were reviewed for extraction well EW-01R, which ceased operation in August 2012.
The groundwater analytical data were divided into two areas, that of source area and dissolved-phase
PCE plume. The distinction was made to separately address the RAOs concerning source control and the
larger-scale, dissolved-phase groundwater contaminant plume.
Source Area
The source area is considered the original location of highest soil and soil gas PCE concentrations
associated with PCE leaks from the dry cleaners and private-to-public sanitary sewer connection behind
the cleaners. Source area groundwater wells are considered to be laterally within a loosely-defined 150
foot buffer from the soil and soil gas source areas, which consist of: MW-03A, MW-05A, MW-08A, MW-
09B, and EW-01R.
PCE trends at the source area wells between August 2008 and August 2012 generally were either stable
or decreasing. MW-08A showed no trend with respect to PCE concentrations over this time period.
Data from well MW-09B was determined to be stable. MW-03A and MW-05A both showed decreasing
trends. MW-03A exhibited a PCE concentration of 42 ug/L in August 2012, down from 1,300 ug/L in
August 2008. MW-05A exhibited a PCE concentration of 51 ug/L in August 2012, down from a high of
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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300 ug/L in November 2009. MW-05A is the closest groundwater monitoring location to the soil vapor
extraction system that was expanded in 2008 and had a positive impact on decreasing soil vapor PCE
concentrations. Overall, PCE concentrations within source area A zone wells are in the 5 to 50 ug/L
range. This is evidence of significant progress in the source area through the withdrawal of source-area
groundwater at EW-01R. Decreases in PCE in source area groundwater may also be attributed to
advective and dispersive processes transporting the contaminant with groundwater in the downgradient
direction. In the B zone beneath the source area at well MW-9B, PCE currently fluctuates from about 4
to 14 ug/L.
PCE results at extraction well EW-01R showed a slow but steady, statistically significant decreasing trend
between January 2009 and August 2012. This well was sampled monthly as part of the groundwater
extraction and treatment system. PCE decreased during this period from almost 200 ug/L to under 100
ug/L. EW-01R was shut off in August 2012, with A zone extraction shifting to the newly installed EW-02
located in a higher-concentration, downgradient portion of the plume.
Dissolved-Phase Plume
PCE was present above 5 ug/L at 11 of 17 evaluated A zone wells not considered source area wells. All A
zone wells hydraulically upgradient of the source area had either stable trends results (MW-07A, MW-
11A, MW-15A) or decreasing trends (MW-01A, MW-02A). MW-18A, near the downgradient extent but
west of the plume axis, had a decreasing trend, although all results were below 5 ug/L since August
2008. Within the central to slightly distal portions of the PCE plume, trends were variable, ranging from
stable at MW-04A, no trend at MW-06A, and decreasing trend at MW-10A. The A zone wells which
define the PCE plumes lateral and distal extents, for the most part, had either stable trend results (MW-
13A) or no trends (MW-16A, MW-17A, MW-19A, MW-23A). There were two exceptions - MW-14A and
MW-20A.
In the Third Quarter 2012 monitoring report, the A zone PCE plume is depicted to bifurcate, with a small,
disconnected PCE lobe centered on well MW-23A to the west of the main plume (Figure 1). The well
defining the lower concentration point within the two lobes is MW-14A. This well had an increasing
trend. PCE has fluctuated between lows of around 2 ug/L to highs upwards of 25 ug/L at MW-14A, with
the highs primarily in the second and third quarters (May and August) each year. The seasonal
variability is likely related to on/off cycles of nearby municipal wells. MW-20A, located on the distal
downgradient edge of the plume, had a probably increasing trend.
PCE was present above 5 ug/L at 9 of 12 evaluated B zone wells not considered source area wells. The
Mann-Kendall trend test results indicated that all evaluated wells except MW-16B, MW-17B, and MW-
20B in the B zone were either stable or had no PCE trend over the period evaluated. MW-20B, located
in the approximate center of the B zone PCE plume, showed a decreasing trend. PCE at this well has
dropped from 160 ug/L in November 2008 to 57 ug/L in August 2012. Results showed an increasing
trend at MW-16B, located on the lateral-to-downgradient edge of the B zone PCE plume. Recent PCE
results from the last three quarters at well MW-16B have increased from about 2 to 24 ug/L; therefore
this is an area that should be closely watched during future sampling events. MW-17B showed a
probably increasing trend. This well is also located in a lateral to downgradient direction from the
plume axis and should be closely watched.
PCE was present above 5 ug/L at only 2 of 5 evaluated C zone wells during the monitored period (MW-
04C and MW-20C), and at each of these wells only one sample was above 5 ug/L during the period of
interest. All wells except one in the C zone showed either no trend (MW-04C, MW-16C, MW-20C) or
stable trend (MW-10C). MW-17C had a probably decreasing trend result.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Groundwater Extraction and Treatment System Operational Data
EW-01R replaced EW-01 and was in operation from August 2006 to August 2012. EW-02 was installed
to more effectively capture and contain the highest concentration portion of the PCE plume, and
beginning in September 2012 EW-01R ceased operation and was replaced by operation of EW-02. Since
the Third Quarter 2012 O&M Report only describes sampling and Site operations up to September 2012,
no operational data has been reported for EW-02.
During this FYR reporting period (Fourth Quarter 2008 through Third Quarter 2012), the groundwater
treatment system (GWTS) has operated with an overall up time of 95 percent. The only significant
prolonged system shutdown was during late Second Quarter 2012 to early Third Quarter 2012, when the
system was down to replace the GWTS effluent pump. From August 2001 to September 2012, the
GWTS had treated approximately 199 million gallons of water and removed approximately 518 pounds
of PCE.
All GWTS effluent samples for this reporting period (Fourth Quarter 2008 through Third Quarter 2012)
met applicable discharge criteria for PCE. Discharge criteria were met for uranium except during the
Fourth Quarter 2010. At that time, resin was replaced in the primary ion exchange vessel because of a
measured increase in uranium to just above 20 pCi/L.
Soil Vapor
Analytical Data
All soil vapor data that has been evaluated is considered source area data since the locations of all vapor
monitoring and extraction wells are within close proximity of the historical PCE release locations. Since
the last FYR, EPA has installed three SVE extraction wells SVE-02, SVE-03 and SVE-04, which are currently
operating. SVE-01 was disconnected from the SVE extraction system and converted to a vapor
monitoring well in 2008.
SVE data analyzed included that from the three SVE extraction wells from November 2008 to August
2012. Data evaluation also included nine vapor monitoring wells for the same period: SVE-01, DP-01A,
DP-01B, DP-05A, DP-05B, DP-06A, DP-06B, OSVE-10, and OSVE-11. Data were collected approximately
every quarter.
Data from vapor monitoring wells were statistically evaluated using the Mann-Kendall test for trend.
Results from the vapor monitoring wells showed only one statistically significant trend, which occurred
at well OSVE-11. Data from OSVE-11 since March 2009 showed a decreasing trend. PCE soil vapor
concentration at OSVE-11 was exceptionally high in March 2009, with a concentration measured at
27,000 ppbv. One year later in March 2010, concentration had decreased to 130 ppbv, and by August
2012 the concentration had further declined to 21 ppbv. Four wells showed no trends (DP-01A, DP-01B,
DP-05B, and DP-06A) while two wells showed stable trends (SVE-01, OSVE-10). Two wells (DP-05A, DP-
06B) contained more than 50% non-detects for PCE vapor hence were not statistically evaluated.
Results from the vapor extraction wells showed one decreasing trend (SVE-04), one probably decreasing
trend (SVE-02) and one well, SVE-03, with no trend. PCE concentrations in vapor from SVE-04 showed a
steady decline from 890 ppbv in November 2008 to 35 ppbv in August 2012. At SVE-02, PCE
concentration at the start of the data set was 14,000 ppbv. Concentration declined drastically between
2008 and 2009. In August 2012 the concentration was 380 ppbv. The initial high PCE concentrations
coupled with the decreasing and probably decreasing trends are evidence that the newly installed soil
vapor extraction wells removed the bulk of contaminant mass soon after they became operational.
Soil Vapor Extraction and Treatment System Operational Data
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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During this FYR reporting period (Fourth Quarter 2008 through Third Quarter 2012), the SVE system has
operated with an overall up time of greater than 99 percent. From June 2001 to September 2012, total
cumulative PCE mass removed through the SVE system was approximately 3,465 pounds. This amount
continues to be significantly greater than the total mass removed via the groundwater treatment
system.
There was a transient spike in SVE system influent PCE concentration after new SVE wells SVE-02, SVE-
03, and SVE-04 came online in November 2008. Prior to system redesign, December 2007 data revealed
influent concentration of 54 ppbv, although measurements were as low as 4.4 ppbv in September 2007.
In November 2008, after new wells were brought online, influent concentration was measured at 4,100
ppbv. This showed the new wells to be effective at extracting contaminant mass from soil via the vapor
pathway. Latest sampling results show treatment system influent PCE concentrations ranging from 190
to 650 ppbv during Third Quarter 2012.
All SVE system effluent samples for this FYR reporting period (Fourth Quarter 2008 through Third
Quarter 2012) met applicable discharge criteria for PCE with the exception of Fourth Quarter 2009, and
First and Second Quarters 2010, when effluent concentrations ranged from 4 to 130 ppbv PCE. Vapor
phase GAC was changed out prior to Third Quarter 2010, and discharge criteria have been met since
that time.
Conclusions
With respect to progress towards meeting the RAOs established in the IROD, the following conclusions
are made regarding the evaluation of groundwater, soil vapor, groundwater extraction and treatment
system, and soil vapor extraction and treatment system operational data in support of the Second FYR:
• New extraction well EW-02, assumed to be operating continuously at 46 gpm which is near the
maximum GWTS capacity of 50 gpm, is capturing more of the high concentration PCE remaining
in groundwater than EW-01R did because it is more centrally located over the bulk of remaining
dissolved phase mass. The capture zone of EW-02 appears to fully encompass the former PCE
source area. Future quarterly groundwater monitoring results may be used to further evaluate
EW-02 effectiveness both for hydraulic source control and reductions in concentrations
throughout the plume.
• It appears the PCE plume has been adequately characterized, with possibly minor data gap
areas remaining. 25 groundwater monitoring wells have been installed since the last FYR, and
the number of wells now totals 40. In addition to the A zone, B and C aquifer zones have been
characterized and delineated with respect to the PCE plume. .
• Within the A zone, recent data demonstrate decreasing trends generally upgradient and within
the source area. Two locations show decreasing trends downgradient of the source area;
however, a third location downgradient of the source area is probably increasing. Trends in
data are likely to be in flux in the immediate future as impacts from operation of EW-02 have
yet to be realized in groundwater data.
• In monitoring of B zone groundwater, careful observation of future quarterly data should be
given to wells MW-16B and MW-17B, where PCE concentrations have been on the rise.
• Optimization of the SVE system by installing three new SVE extraction wells has had some
positive effect on removing contaminant mass from the soil in the source area and in lowering
soil vapor concentrations. Soil vapor in several wells still exceeds 200 ppbv. Other mitigating
measures conducted, such as the response action at the Parts House, and Halford's cessation of
using PCE, have contributed to mitigate risk to acceptable levels in indoor air within Halford's
Cleaners and the Parts House.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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• Both SVE and GWT systems are currently meeting applicable discharge requirements with
respect to VOCs, including PCE, and uranium.
• While PCE remains above the MCL of 5 ug/L, the interim RAOs pertaining to source control and
plume delineation and migration assessment have been largely achieved based on actions taken
at the Site prior to and since the last FYR. Operation of the interim remedy and associated
monitoring will continue. The final ROD will set new RAOs to achieve applicable cleanup levels
through a selected final remedy for the Site.
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
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Project: Modesto Superfund Site
Location: Modesto
Time Period: 8/19/2008 to 8/10/2012
Consolidation Period: Quarterly
Consolidation Type: Geometric Mean
Duplicate Consolidation: Maximum
ND Values: Detection Limit
J Flag Values : Actual Value
Number
Number
Mann-
All
Source/
of
of
Coefficient
Kendall
Confidence
Samples
Concentration
Well
Tail
Samples
Detects
of Variation
Statistic
in Trend
"ND" ?
Trend
TFT RAC H I. OROFT HYL E N Fj PC F)
MW-01A
T
17
17
0.25
-55
98.8%
No
D
MW-02A
T
17
17
0.16
-54
98.6%
No
D
MW-03A
S
17
17
0.55
-43
95.8%
No
D
MW-04A
S
17
17
0.54
-24
82.6%
No
S
MW-04B
S
16
16
0.72
4
55.3%
No
NT
MW-04C
S
16
8
2.10
-26
86.7%
No
NT
MW-05A
T
17
17
0.49
-51
98.1%
No
D
MW-06A
T
16
16
1.17
8
62.2%
No
NT
MW-07A
T
16
3
0.54
-10
65.5%
No
S
MW-08A
T
17
17
0.47
16
72.9%
No
NT
MW-09B
T
17
17
0.83
-27
85.6%
No
S
MW-10A
T
17
17
0.61
-95
100.0%
No
D
MW-10B
T
16
16
0.26
-7
60.5%
No
S
MW-10C
T
16
3
0.80
-28
88.6%
No
S
MW-11A
T
17
17
0.45
-1
50.0%
No
S
MW-12A
T
17
17
0.21
-84
100.0%
No
D
MW-13A
T
17
17
0.82
-20
78.0%
No
S
MW-14A
T
17
17
0.87
56
98.9%
No
1
MW-15A
T
17
4
0.24
-20
78.0%
No
S
MW-16A
T
16
2
1.27
-2
51.8%
No
NT
MW-16B
T
16
16
1.11
38
95.2%
No
1
MW-16C
T
16
6
1.71
17
76.1%
No
NT
MW-17A
T
16
14
1.28
7
60.5%
No
NT
MW-17B
T
16
16
0.37
30
90.3%
No
PI
MW-17C
T
16
5
1.25
-36
94.2%
No
PD
MW-18A
T
16
16
0.22
-39
95.7%
No
D
MAROS Version 3.0 Tuesday, February 19, 2013
Release 352, September 2012 ^aSe 1 of 2
Second Five Year Review - Modesto Groundwater Contamination Superfund Site 91
I
User Name: Blair C. Kinser
State: California
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I
vlodesto Superfund Site
User Name: Blair C. Kinser
State; California
! TETRACIILOROETI lYLENE(PCE)
Number
Number
Mann-
All
Source/
of
of
Coefficient
Kendall
Confidence
Samples
Concentration
Well
Tail
Samples
Detects
of Variation
Statistic
in Trend
"ND" ?
Trend
MW-19A
T
16
6
2.96
-22
82.5%
No
NT
MW-19B1
T
16
12
1.21
-24
84.7%
No
NT
MW-20A
T
16
16
0.41
35
93.6%
No
PI
MW-20B
T
16
15
0.42
-66
99.9%
No
D
MW-20C
T
16
4
3.88
-10
65.5%
No
NT
MW-21A
T
4
4
0.22
-2
62.5%
No
S
MW-22A
T
4
0
0.00
0
37.5%
Yes
ND
MW-23A
T
4
4
0.20
3
72.9%
No
NT
MW-24B
T
4
4
0.31
-2
62.5%
No
S
MW-25B
T
4
4
0.17
-1
50.0%
No
S
MW-26B
T
4
2
0.22
5
89.6%
No
NT
MW-27B
T
4
0
0.00
0
37.5%
Yes
ND
MW-28B
T
4
4
0.11
-4
83.3%
No
S
MW-29B
T
4
4
0.39
-5
89.6%
No
S
Note: Increasing (I); Probably Increasing (PI): Stable (5); Probably Decreasing (PD); Decreasing (D); No Trend (NT); Not
Applicable (N/A)-Due to insufficient Data (< 4 sampling events); Source/Tail (S/T)
The Number of Samples and Number of Detects shown above are post-consolidation values.
MAROS Version 3.0
Release 352, September 2012
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
Tuesday, February 19, 2013
Page 2 of 2
92
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Project; Modesto Superfund Site
Location: Modesto
Time Period: 8/19/2008 to 8/10/2012
Consolidation Period: Quarterly-
Consolidation Type: Geometric Mean
Duplicate Consolidation: Maximum
ND Values: Detection Limit
J Flag Values : Actual Value
Number
Number
Mann-
All
Source/ of
of
Coefficient
Kendall
Confidence
Samples
Concentration
Well
Tail Samples
Detects
of Variation
Statistic
in Trend
"ND" ?
Trend
T ET RACH LOROET HYL.E N E( PCE)
SVE-01
T 11
11
0.73
2
53.0%
No
S
SVE-02
T 16
16
1.71
36
94.2%
No
PD
SVE-03
S 16
16
1.35
9
63.9%
No
NT
SVE-04
T 16
14
1.43
-69
99.9%
No
D
Note: Increasing (I); Probably Increasing (PI); Stable (S); Probsbiy Decreasing (PD); Decreasing (D); No Trend (NT); Not Applicable
(N/A)-Due to insufficient Data (< 4 sampling events); Source/Tail (S/T)
The Number of Samples and Number of Detects shown above are post-consolidation values.
I
User Name: Blair C. Kinser
State; California
MAROS Version 3.0
Release 352, September 2012
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
Tuesday, February 19, 2013
Page 1 of 1
93
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sties Sum
I
Project: Modesto Groundwater Superfund Site, Modesto, California
Time Period: 1/30/2009 to 8/8/2012
Analyte: PCE
Non-detect Values: Use Detection Limit
J Flag Values: Use Actual Value
Groundwater
#
n
Coefficient
Mann-
Confidence
All
Concentration
Well ID
Samples
Detects
of
Variation
Kendall
Statistic
in Trend
Samples
"ND"?
Trend
EW-01R
45
45
0.17
-447
>95%
No
Decreasing
SVE
n
#
Coefficient
Mann-
Confidence
All
Concentration
Monitoring
Samples
Detects
of
Kendall
in Trend
Samples
Trend
Well ID
Variation
Statistic
"ND"?
DP-01A
11
11
1.08
10
<90%
No
No Trend
DP-01B
11
9
1.25
-6
<90%
No
No Trend
DP-05A
9
3
n/a
n/a
n/a
No
Not evaluated
DP-05B
9
5
1.13
-14
<90%
No
No Trend
DP-06A
11
11
1.02
2
<90%
No
No Trend
DP-06B
11
2
n/a
n/a
n/a
No
Not evaluated
OSVE-10
12
12
0.91
-4
<90%
No
Stable
OSVE-11
12
12
3.40
-32
>95%
No
Decreasing
February 14,2013
Page 1 of 1
Second Five Year Review - Modesto Groundwater Contamination Superfund Site 94
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Halford's
Cleaners
Basemap and plume depiction from Third Quarter 2012 O&M Report (URS 2012)
LEGEND
3rd Quarter 2012 PCE Plume Depicted
EW-02 (Dec 2012) Empirical Capture Zone
EW-01R (Aug 2012) Empirical Capture Zone
Groundwater Elevation Contours. Dec 2012
~ Groundwater Monitoring Well
X Groundwater Extraction Well
« Groundwater Extraction Well (Offline)
Figure 1
Groundwater Data Evaluation (A-zone)
February 2013
Modesto Groundwater Superfund Site
2nd Five-Year Review
- MW-8UO»
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
95
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LEGEND
y Groundwater Elevation Contours, Dec 2012
~ Groundwater Monitoring Well
X Groundwater Extraction Well
& Groundwater Extraction Well {Offline)
Figure 2
Groundwater Data Evaluation (B-zone)
February 2013
Modesto Groundwater Superfund Site
2nd Five-Year Review
A
0 " 300
1 I I
Scale in f-ect
Detail Area
~
EW-01R\
~ MW-03A
EW-01
MW-09B + ®
MW-08A ~
HalfoTtl'3
Cleaners
~ MW-05A '
t-iH
Basemap from Third Quarter 2012 O&M Report (URS 2012)
Second Five Year Review - Modesto Groundwater Contamination Superfund Site
96
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