Superfund Record of Decision: Sharpe Army Depot, CA


          United States        Office of
          Environmental Protection   Emergency and
          Agency           Remedial Response
EPA/ROD/R09-93/089
January 1993
&EPA    Superfund
          Record of Decision:
          Sharpe Army Depot, CA

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4.
50272-101
REPORT DOCUMENTA T10N 11. REPORT NO.
PAGE EPA/ROD/R09-93/089
11tJe and Subtitle
SUPERFUND RECORD OF DECISION
Sharpe Army Depot, CA .
First Remedial Action
A~hor(l)
~
3. RaclpIent'. Ace.... No.
~
Repan Date
01/25/93
&
7.
8.
PerformIng Organization Rape. No.
9.
Performing Organization Name and Addr888
10
Proj8ct TulclWork Unit No.
11. Contrac:t(C) Of Grart(G) No.
(C)
(0)
12. Sponaorlng Organization Name and Addr881
'U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Repan .. PerIod Covar8d
Agency
800/800
14.
15. SuppJarnantary Noe..
PB94 - 9"64518
16. AbatI'lCt (UmJt: 200 words)
The 720-acre Sharpe Army Depot site is an active military installation located
northeast of Lathrop, California. Land use in the area is mixed residential,
agricultural, and light industrial. In addition, the site overlies two aquifers, which
are sometimes interconnected. In 1941, Sharpe Army Depot was established to support
supply and maintenance missions. Until 1976, the maintena~ce mission included repair
and reconditioning of both heavy equipment and aircraft. The supply mission currently
is active and includes storage, handling preservation, packaging, and shipment of
general supplies and equipment. The major waste-generating activities from these
operations were paint-stripping, metal finishing and painting, engine overhauls,
hydraulic and electric repairs, airframe body work, and the repair and conditioning of
components- Previous environmental studies by the Army indicated ground water
contamination and offpost migration of VOCs, as well as sporadic detection of metals.
Available data indicates that the primary source of this VOC contamination is
associated with onsite post-vehicle maintenance activities. The South Balloon Area was
determined to be a major source of VOC contamination; however, other individual source
areas may include former burial trenches and/or former liquid disposal areas. As a
(See Attached Page)
17. Document Analyala .. Descriptors
Record of Decision - Sharpe Army Depot, CA
First Remedial Action
Contaminated Medium: gw
Key Contaminants: VOCs (benzene, PCE, TCE, toluene, xylenes), metals (arsenic),
inorganics
b. Idantlfl8r81Opan
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EPA/ROD/R09-93/089
Sharpe A~y Depot, CA
First Remedial Action
Abstract (Continued)
. result of these investigations, two interim ground water extraction and treatment systems
were installed at the South Balloon area in 1987 and 1990, respectively. For the purpose
of remediation, the site. has been divided into two operable units. This ROD addresses
ground water contamination, as OU1. A future ROD will address site-wide contamination,
including contaminated soil and ground water. The primary contaminants of concern
affecting the ground water are VOCs, including benzene, PCE, TCE, and xylenes: metals,.
including arsenic; and other inorganics.
The selected remedial action for this site includes extracting and treating contaminated
ground water onsite using air stripping to remove VOCs: treating off-gas emissions using
gas phase carbon adsorption in the Central area only: discharging the treated ground water
onsite to surface water, into evaporation/infiltration ponds, or reusing the treated
water: and monitoring ground water. The estimated present worth cost for this remedial
action is $4,147,000, which includes an unspecified O&M cost of $2,140,000 for 16 years.
PERFORMANCE STANDARDS OR GOALS:
Chemical-specific ground water cleanup goals are based on Federal and State MCLs and risk-
based levels, and include bromodichloromethane 0.5 ug/l: bromofo~ 0.5 ug/l: carbon
tetrachloride 0.5 ug/l; chlorofo~ 0.5 ug/l; dibromochloromethane 0.5 ug/l: ortho-
dichlorobenzene 10 ug/l: para-dichlorobenzene 5 ug/l: 1,1-DCA 5 ug/l: 1,2-DCA 0.5 ug/l:
1,1-DCE 0.5 ug/l; cis-1,2-DCE 6 ug/l: trans-1,2-DCE 10 ug/l; 1,2-dichloropropane 0.5 ug/l:
1,3-dichloropropane 0.5 ug/l: methylene chloride 0.5 ug/l: PCE 0.5 ug/l: 1,1,1-TCA 200
ug/l: 1,1,2-TCA 0.5 ug/l: 1,1,2,2-TCA 0.5 ug/l: TCE 5 ug/l: and vinyl chloride 0.5 ug/l.
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Contract No. DAAA15-88-DOOO3
. Delivery Order 0002
USA T HAM A.
U.S. Army Toxic and Hazardous Materials Agency
.'
REMEDIAL INVESTIGATIONIFEASIBILITY
STUDY AT DDRW.SHARPE SITE.
RECORD OF DECISION
OPERABLE UNIT 1
. ENVIRONMENTAL SCIENCE & ENGINEERING. INC.
P.O. 8011703
Gainesville. FL 32602.1703
January 1993
Distribution Rmited 10 U.S. GoverM1ent Agencies only for
protection of privieged information evaluating another command:
January 1993. Requests for 1his doctJnent must be referred 10:
Commander, U.S. Army Toxic and Hazardous Materials ArJerq,
Aberdeen Proving Ground, MD 21010-5401; or Commander,
Sharpe Site, Lattwop, CA 95331.
u.s. ARMY TOXIC AND HAZARDOUS MATER1AlS AGENCY
Installation Restoration Division
Aberdeen Proving Ground. MD 21010.5401
Prin8ld on ~ P8per
...-:
'b
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P /SHARPElGWROD.l
01/07/93
Declaration for the Record of Decision
SITE NAME AND LOCATION
Defense Distribution Region West-Sharpe Site
Lathrop, California
SfATEMENT OF BASIS AND PURPOSE
.

This decision document presents the selected remedial action for Defense
Distribution Region West (DDRW)-Sharpe Site, in Lathrop, California, developed
in accordance with CERCLA, as amended by SARA and, to the extent practicable,
the National Contingency Plan. This decision is based on the administrative
record for this site.
The State of California concUrs on the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if not
addressed by implementing the response action selected in this ROD, may present
an imminent and substantial endangerment to public health, welfare, or the
envirorunent.
DESCRIPTION OF THE REMEDY
This operable unit is the first of two that are planned for the site. The first
operable unit .addresses VOC, arsenic, selenium, nitrate, and bromaci1
contaminated groundwater. Any additional groundwater contaminants or
compounds identified in subsequent efforts will be addressed as part of the site-
wide comprehensive ROD. The function of this operable unit is to prevent
further migration of contaminated groundwater and capture the contaminant
plumes.
The major components of the selected remedy include:
Groundwater extraction wellfield and associated piping network;
Three air stripping treatment systems consisting of countercurrent
packed towers to remove VOC contamination;
Gas-phase carbon adsorber for. treatment of offgas (for one of the three
treatment systems);
1
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PISHARPEIGWROD.2
01/11/93
- Disposition 01 treated groundwater via surface water disc:barge, water
reuse, and evaporation/infiltration ponds with connector/injection
wells.
Conceptual remedial design information is presented in this ROD. The
conceptual designs are adequate for the purpose .of evaluating potential remedies
and for selecting a remedy. Detailed remedial designs and remedial actions will
be based on a sitewide, three-dimensional groundwater now and transport model
under development by the U.S. Army Toxic and Hazardous Materials Agency
(USATHAMA) and a treatment plant design document under development by the
u.s. Army Corps of £ngineen (USACE).

STATlTTORY DETERMINA110NS
The selected remedy is protective of human health and the environment,
complies with federal and state requirements that are legally applicable or
relevant and appropriate to the. remedial action, and is cost effective. This
remedy uses pennanent solutions and alternative treatment (or resouree
recovery) technologies to the maximum extent prac:1icable and satisfies the
statutory preferenc'e for remedies that employ treatment that reduces toxicity,
mobility, or volume as a principal element.

Because this remedy will result in hazardous substances remaining onsite
above health-based levels [i.e., the contaminated soils (which will be addressed
with the second operable unit)], a review will be conducted within 5 years after
commencement of remedial action to ens\U'e that the remedy continues to
provide adequate protection of human health and the environment.

--i. :i:../S ').

Colonel James W. LaBounty
Commander, Defense Distn"bution Region West-Sharpe Site
/4I~""1f1
Date
~ .
W \4c-
Daniel W. ovem. EPA Regional Administrator. Region IX
f . "1S.1f3
Date
~lj~ .:L ,.
Anthony J. Landis,: .E, Chief Site Mitigation Branch
Region 1. Depanment of Toxic Substances Con1rOl

~'I01-«.~J~ . .
Wllliam Crooks. Executive Officer. Central Valley, RWQCB
2
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Date
i -2"- rS
Date
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P/SHARPEIGWROD.3
11/11/92
DECSION SUMMARY
1.0 SITE NAME. LOCATION. AND DESCRIP110N
SHARPE is located northeast of Lathrop, CA, in the San Joaquin Valley
approximately 9 miles south of Stockton (Fig. 1). The installation forms an
approximate rectangle O.S-mile-wide (east-west) and 2 miles long (north-south)
and encompasses approximately 720 acres (Fig. 2). The site is bordered to the
west by the Southern Pacific Railroad, to the east by the Western Pacific
Railroad, to the north by Roth Rd., and to the south by Lathrop Rd. The South
.. San Joaquin Irrigation District Canal (SSJIDC) runs parallel to the eastern
boundary of the site. Land around SHARPE is used for a variety of purposes,
including residential, agricultural, and light industry.

SHARPE lies on slightly sloping to flat land. Elevations generally vary between
16 and 23 feet above mean sea level (ft-ms!). Most of the surface water runoff
is routed into drains leading to the stormwater sewer system and then into the
SSJIDC at the east side of the site. This canal discharges into French Camp
Slough a few miles north of SHARPE. French Camp Slough discharges into the
San Joaquin River, which flows into San Francisco Bay. No surface water runoff
occurs on the west boundary of SHARPE; surface water along this boundary
. drains into sumps 5 to 15 feet (ft)deep, located along the west fence line, and is
allowed to percolate.
The subsurface hydrogeology at SHARPE can be conceptually subdivided into
aquifer zones. The A- and B-aquifer zones are sometimes interconnected and
often encountered at varying depthS and thicknesses. Both aquifers are usually 5
to 12 ft thick, and the deposits are not entirely saturated. The confining layers
of these zones consist of clay, silty clay, and sandy clay; these layers are of
varying thicknesses and are often discontinuous.

The C-series (140-ft) and D-series (270-ft) wells at SHARPE are completed in
medium to coarse quartz sand, gravel, clayey sand, and silty-gravelly sand
deposits that are semiconsolidated and less well sorted than those of the A- and
B-series wells; The C- and D-zone wells at SHARPE are probably in the upper
Laguna Formation. The CD-series aquifer zone is not seen as a unique aquifer
but as a saturated zone that is interconnected to the C- or D-aquifer zone or both
the C- and D-aquifer zones. Data from the pump test conducted at SHARPE in
~ovember 1984 indicate that a relatively high degree of interconnection betWeen
aquifer zones exists at some areas of known contamination.
3
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Figure 1
LOCATION MAP
REMEDIAL INVESTIGATION!
FEASIBILITY STUDY
Sharpe Site, Lathrop, California

U.S. Army
Toxic and Hazardous Materials Agency
Aberdeen Proving Ground, Maryland
SOURCE: MCLAREN ENVIRONMEKTAI. ENOINURING, ,tI8; ESE, '110.
/,
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Figure 2
SITE MAP
SOURCES ESC, 1988, 1990, SM*0, IB«7

~ TcflfbiM IN,* •,
MASMUt lit
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P/SHARPEIGWROD.4
11/11/92
No discernible evidence exists that faulting or geologic structures influence
groundwater flow patterns. Groundwater flow along the western boundary of
SHARPE is generally northwestward.
2.0 SITE IDSTORY
"
SHARPE was established in 1941 and consists of approximately 720 acres.
ConstrUction of the major facilities at SHARPE began during World War II and
continued into the post-war period, Additional facilities were constructed during
the Korean and Vietnam Conflicts. Construction is still in progress, with the
addition of the Western Distribution Center (WDC) in 1988. For most of its'
existence, the installation has had both supply and maintenance missions. The
supply mission remains active and includes storage, handling, preservation,
packaging, and shipment of general supplies and equipment. The ~tenance
mission included repair and reconditioning of both heavy equipment and aircraft.
The heavy-equipment mission began in the late 194Os, and the aircraft mission,
was added in 1957. These missions were discontinued in 1976. The major
waste-generating activities from these operations were paint stripping, metal
finishing, and painting. Other activities included engine overhauls, hydraulic
and electric repairs, airframe and body work, and component repair and
reconditioning. Since 1976, the maintenance mission has included only
maintenance of installation facilities and vehicles used in performing the supply
mission.
, ~
Previous environmental studies have indicated groundwater contamination with
offpost migration of volatile organic compounds (V0Cs). Base-neutral and acid
extractables (BNA) and nitrates were also investigated during the early phases of
the remedial investigation (RI) and found not to be chemicals of potential
concern. Additionally, arsenic, selenium, and bromaci1 have been detected
sporadically in groundwater samples. Available data indicate that the prinwy
source(s) of the VOC contamination is associated with past mission-related
activities (e.g., vehicle maintenance) at SHARPE. A major area of VOC
contamination is the South Balloon Area of SHARPE; however, other individual
source areas may include foniler burial ttenches and/or several former liquid
disposal areas.
As a result of early investigations conducted at SHARPE, an interim groundwater
extraction and treatment'system (refelTed to as the South Balloon Area
Groundwater Treatment System) has been installed and in operation since
March 1987 to control migration of contaminated groundwater in that portion of
the site. A separate interim RI and feasibility study (FS) was also prepared to
identify and evaluate interim rernedialaction alternatives in the North Balloon
6
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P/SHARPEIGWROD.5
11/11/92
Area. As a result of this investigation, a second interim groundwater pump-and-
tteat system was constructed in the North Balloon Area; this system began
operation in October 1990. The agencies reviewed and infonnally approved the
design and construction of the interim systems.
All studies and remedial actions are/were conducted under a Federal Facilities
Agreement among the U.S. Department of Defense (DOD), U.S. Environmental
Protection Agency (EPA), and the State of California.
3.0 IDGHLIGHTS OF COMMUNITY PARTICIPATION
The RIlFS and Proposed Plan for SHARPE were released to the public in
February 1992. These two doCuments were made available to the public in the
administrative record, located at SHARPE, and an infonnation repository
maintained at the Manteca Branch of the Stockton-San Joaquin County Public
Ubrary. The notice of availability for these two documents was published in the
Modesto Bee, Stockton Record, and" the Manteca Bulletin, Jan. 24, 1992. A
public comment period was held from Feb. 6 to Mar. 9, 1992. In addition, a
public meeting was held on Feb. 27, 1992.. At this meeting, representatives from
the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA), Defense
Distribution Region West (PDRW), the Department of Toxic Substances Control
(DTSC), Central Valley Regional Water Quality Control Board (CVRWQCB), and
EP A Region IX answered questions about problems at the site and the remedial
alternatives under consideration. A response to the comments received during
this period is included in the Responsiveness Summary, which is part of this
Record of Decision (ROD). This decision document presents the selected
remedial action for SHARPE, in Lathrop, CA, chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Uability Act
(CERCLA), as amended by the Superfund Amendments and Reauthorization Act
of 1986 (SARA) and, to the extent practicable, the National Oil and Hazardous
Substances Pollution Contingency Plan (NCP). The decision for this site is based
on the administrative record. ..
4.0 SCOPE AND ROLE OF OPERABLE UNIT
As with many Superfund sites, the problems at SHARPE are complex. As a
result, SHARPE. organized the work into two operable units (OUs):
OU One: Groundwater contaminated with VOCs, arsenic, selenium,
nitrate, and bromacil; and
7
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P/SHARPE/GWROD.6
11/11/92
OU Two: Site-wide comprehensive ROD, .to address other
groundwater contaminants, contaminants identified in future studies,
and contaminated soils.

This ROD is for OU One. OU Two will be addressed in a separate site-wide
comprehensive ROD. The VOC, arsenic, selenium, nitrate, and bromacil
contaminated groundwater is a principal threat at this site because of the
potential for direct ingestion of contaminated water acquired from domestic
water wells. Remediation of groundwater has commenced, as part of an interim
remedial action, at two of the three areas which require remedial action (the
North Balloon and South Balloon Areas). The third area (the Central Area)
requiring groundwater remediation is currently in the remedial design phase.
Actual construction is planned to begin in November 1993.

5.0 SUMMARY OF SITE CHARACTERISTICS

Groundwater contaminants identified at SHARPE include VOCs, arsenic,
selenium, nitrates, and bromacil. A discussion of the respective extent of
contamination is presented in the following paragraphs. Sec. 6.5 provides a
detailed description.

Six different plumes (Fig. 3) of VOCs [predominantly trichloroethene (TCE)]
exist in the groundwater within the three shallowest aquifers beneath SHARPE,
as well as offsite, downgradient from the site: Plume 1 (South Balloon);
Plumes 2, 3, 4 & 5, and 6 (Central Area); and Plumes 7 & 8 [North Balloon
Area-note that Plume 8 differs from the rest of the plumes because
tetrachloroethene (PCE) is the most prevalent contaminant in this plume].
Plumes 4 and 5, and Plumes 7 and 8 were initially divided into individual
contaminant plumes. These plumes have since been consolidated into two
separate plumes, Plumes 4 & 5 (or Plume 4) and Plumes 7 & 8 (or Plume 7).
The concentrations of other VOCs are low with respect to concentrations of TCE
(with the exception of Plume 8 where PCE is the predominant contaminant).
Currently, no receptors are found for the existing contamination onsite. Risks
were evaluated for a future onsite and offsite receptor in the event the site is
used for residential purposes or contaminants migrate offpost. The maximum
contaminant level (MCL) for TCE is 5.0
Most of the site-related impacts appear to be due to the presence of arsenic and
TCE. The risks due to arsenic are mostly due to the exposure assumptions in the
risk evaluations; however, a site-related activity contributing to arsenic is not
readily identifiable. Risk from TCE varies between 1 to 100 in a million.
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P/SHARPEIGWROD.7
11/11/92
Arsenic (detected in the A-, B-, and C-zones, see Figs. 4, 5, and 6) and selenium
(detected primarily in the A-zone, see Fig. 7) have been detected in groundwater
in concentrations greater than the MCL (SO and 10 I£g/L, respectively).
Although the sources of arsenic and selenium have not been positively defined,
infonnation collected for the RI indicates that the presence of these metals in .
groundwater is not attributable to past or current activities onsire.
Nitrates in groundwater (Figs. 8, 9, and 10) have been detected in
concentrations greater than the MCL (10,000 I£g/L). Like arsenic and selenium,
the source. of nitrates has not been positively defined. Information collected for
the RI indicates the nitrates in groundwater are not attributable to past or
current activities onsite. .
Bromaci1 has been detected in groundwater in concentrations grea~er than the
certified reporting limit (CRL) (6 i£gIL). Bromaci1 is primarily confined to the
shallowest aquifer zone (A-zone). Bromaci1 contamination is the result of using '.
the herbicide onpost to control unwanted plant groWth. Fig. 11 presents
concentration isopleths for bromaci1 in the A-zone.
6.0 SUMMARY OF SITE RISKS
The baseline risk assessment for the groundwater contamination at SHARPE is
performed as part of the remedial investigation/feasibility stUdy (RI/FS) to .
determine if the chemical concentrations observed in the groundwater samples
from the site pose significant risks to human health and the environment.
Specific objectives of the process include providing:

1. An analysis of baseline risks to help detennine the need for action at
SHARPE,
2. The basis for determining onsite levels of chemicals that do not
represent a significant threat to the public health,

3. The basis for comparing the potential health impacts of various
remedial alternatives, and
4. A consistent process for evaluating and documenting public health
threats at the sites.
The baseline risk assessment is, therefore, perfonned using the Risk Assessment
Guidance for Superfund (RAGS) (EPA, 1989) and consists of the following five
primary components., each of which are described in the following sections:
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C-IONE NITRATE CONCENTRATIONS IN GROUNDWATER, 2ND QUARTER 1990
SOURCES, £S£
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'Figure 11
BROMACIL CONCENTRATIONS IN GROUNOHATER
A ZONE
MNCOIAl IMVESIIG/MIOK/
FEASIBILlIT SIUOT
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U.S. A*.,
lull •«« H»t»ftt»f n»l>rl|l« At«««»
-------
P/SHARPEIGWROD.8
11/11/92
1.
Selection of chemicals of potential concern,

Identification of significant potential exposure pathways to human and
environmental receptors,
2.
3.
Estimation of the potential risks by comparing the measured site
concentrations to health and environmental criteria, and
4.
Risk characterization associated with the potential exposure to
constituent chemicals both on- and offsite.
Potential ecological receptors in and around SHARPE include terrestrial
vegetation, soil invertebrates, small mamma1s~ birds, reptiles, and aquatic plants,
invertebrates, and vertebrates asso~ated with the drainage ditches., In a~dition,
agricultural fields and stockyards are prevalent in the areas immediately
SUlTounding the depot. A more detailed description of potential ecological
receptors and sensitive habitat is presented in the risk assessment report for soils
at this site [Environmental Science & Engineering, Inc. (ESE), 1992].
No groundwater exposure pathways to nonhuman receptors are complete at this
time. The potential exists for offsite contamination of inigation wells at a future
time. However, due to the volatile nature of the contaminants, potential risks
due to this exposure pathway would be negligible. CU1Tent concentrations in
groundwater are less than levels of these volatile compounds in surface water
which have been shown to be toxic or which have been set as protective criteria
[see Table 5-10 of Groundwater RA (ESE, 1991)]. For instance, CU1Tent levels of
TCE in groundwater do not exceed the available lowest-observed-effect level
(LOEL) for this compound in surface waters. These data support the conclusion
that evaluation of a future scenario for inigation well contamination is
unwarranted due to the low toxicity of these compounds. Concentrations in
groundwater would be significantly reduced in surface waters used in inigation
due. to the volatility of these compounds; it is not expected that toxic levels of
these compounds would be reached in surface waters even under worst-case
conditions. Therefore, no further evaluation of nonhuman receptors is warranted
at this time. .
6.1 Chemicals of Potential Concern (COCs1
More than 3,760 groundwater samples were collected as a function of time,
depth, and area from the monitor, extraction, and supply wells screened in the
A-, B-, C-, and D-aquifer zones beneath SHARPE (ESE, 1990). Samples were
analyzed for VOCs, pesticides, and metals. Earlier site characterization studies
19
-------
P/SHARPEIGWROD.9
11/11/92
had investigated the potential presence of semivolatile organic compounds,
additional metals, and inorganic constitUents such as nitrates. The primary
groundwater contaminants detected were VOCs, with TCE being the most
commonly detected analyte, and a variety of additional organic contaminantS
identified at much lower concentrations.
The following is the final list of COCs; their abbreViations (listed in parentheses)
are from the USATIiAMA database dictionary (Potomac Research, 1990). The
most common abbreviation for nichloroethene is TCE and will be used
throughout this report in lieu of the USATIiAMA abbreviation of TRCLE. The
VOCs identified at SHARPE include:
..
Benzene (C6H6),
Bromodichloromethane (BRDCLM),
Bromofonn (CHBR3), .
Carbon Tetrachloride (CCL4),
Chlorofonn (CHCI3),
cis-l,2-Dichloroethene (C12DCE),
Dibromochloromethane (DBRCLM),
Dichlorobenzene (DCLB),
1,l-Dichloroethane (11DCLE),'
l,2-Dichloroethane (12DCLE),
l,l-Dichloroethene (11 DCE),
l,2-Dichloropropane (12DCLP),
1,3-Dichloropropene (C13DCP,
T13DCP),
Methylene Chloride (CH2CL2),
ortho-Dichlorobenzene (12DCLB),
para-Dichlorobenzene (14DCLB),
1,2,2-Tetrachloroethane (TCLEA),
Tetrachloroethene (TCLEE),
Toluene (MEC6HS),
trans-l,2-Dichloroethene (T12DCE),
1,1, I-Trichloroethane (111 TCE),
l,1,2-Trichloroethane (112TCE),
Trichloroethene (TRCLE),
Vmyl Chloride (C2H3CL), and
Xylene (XYLENE).
.. .
Nonvolatile compounds found at SHARPE and addressed by this ROD include:
Arsenic (AS) *,
Bromaci1 (BRMCIL),
Selenium (SE)*, and
Nitrate (NO:J*.

*Found onsite at background levels (ESE, 1990).
6.1.1 Metal and Pesticide Contmn1nan~
One pesticide, bromacl1, and two metalloid/metals, arsenic and selenium, were
identified in the groundwater. As stated in the RI report (ESE, 1990), no
apparent spatial and temporal relationship existS between the high concentration
levels of arsenic and selenium. Bromacil, a herbicide, is still in use for weed
20
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P/SHARPF./GWROD.I0
11/11/92
control at the site, and elevated concentrations have been identified in
groundwater.
Subsequent to making the Risk Assessment (RA) report a final document,
additional contaminants such as PCB and heavy metals have been identified at
waste oil sites. These contaminants will be addressed as part of the site-wide
comprehensive ROD. .
6.1.2 VOC Plumes
Based on the groundwater TCE disnibution pattern at SHARPE, the
contaminated areas were initially divided into eight individual contaminant
plumes. Plumes 4 and 5 and 7 and 8 have since been consolidated into single
plumes 4 and 7, respectively. The plumes are shown in Fig. 3.
Plume 1
Plume 1, located in the South Balloon Area, covers a wide area of the SHARPE
site. The A-, B-, and C-aquifer zones were sampled in the region during the
environmental monitoring. The VOCs found to exceed the state MCLs, EPA
MCLs, and USATHAMA CRLs were TCE, chIorofonn, 1,2-dichloroethane,
trans-I,2-dichloroethene, and tettachloroethene.
Plume 2
Of the six wells identified within Plume 2, the only COC identified was TCE.
Plume 3
The significant (most predominant) contaminants in this plume area were TCE,
1,2-dichloroethane, and trans-l,2-dich10r0ethene.
Plume 4
The significant coes in this plume area were TCE, cblorofonn, and
tettachloroethene.
Plume 6
TCE was the only significant coe identified in this plume area.
21
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P/SHARPEIGWROD.ll
11/11/92
Plume 7
This combined phnne had TCE and tetrachloroethene as significant contaminants
in the area.
6.2 TOXICI'IY ASSESSMENT
The toxicity assessment step in risk assessment weighs the available evidence
regarding the potential for a chemical to cause toxic effects in exposed
individuals. The toxicity assessments used to develop toxicity values consist of
two steps: hazard identification and dose-response assessment. In the first step,
the potential adverse effects from exposure to the chemical are detennined along
with the type of health effect involved. In the second step, the quantitation of
the toxicity values and esrlm2tion. of reference dose values are perfonned.

Cancer potency factors (CPFs) have been developed by EP}:s Carcinogenic
Assessment Group for estimating excess lifetime cancer risks associated with
exposUre to potentially carcinogenic chemicals. CPFs, which are expressed in
units of milligrams per kilogram per day [(mg/kg-day)"l], are multiplied by the
estimated intake of a potential carcinogen, in mg/kg-day, to provide an upper-
bound estimate of the excess lifetime cancer risk associated with exposure at that
intake level. The term "upper bound" reflects the conservative estimate of the
risks calculated from the CPF. Use of this approach makes underestimation of
the actual cancer risk highly unlikely. Cancer potency factors are derived from
the results of human epidemiological studies or chronic animal bioassays to
which animal-to-human extrapolation and uncertainty factors have been applied.
.. ~
Reference doses (RIDs) have been developed by EPA for indicating.the potential
for adverse health effects from exposure to chemicals exhibiting noncarcinogenic
effects. RiDs, which are expressed in units of mg/kg-day, are estimates of
lifetime daily exposure levels for hum91'1S, including sensitive individuals.
Estimated intakes of chemicals from environmental media (e.g., the amount of a
chemical mgested from contaminated drinking water) can be compared to the
RiD. . RiDs are derived from human epidemiological studies or animal studies to
which uncertainty factors have been applied (e.g., to account for the use of
animal data to predict effects on humans). These uncertainty factors help ensure
that the RIDs will not underestimate the potential for adverse noncarcinogenic
effects to occur.
A list of noncarcinogens and their respective RfDs for the SHARPE groundwater
COCs and the slope factors [cancer slope factors (CSFs)], along with their
22
-------
,-
P/SHARPEIGWROD.12
11/11/92
weight-of-evidence classification for the carcinogens identified in the
groundwater at SHARPE, is presented in Table 1.
6.2.1 Uncertainties Related to Toxicity Information
The uncertainties related to the toxicity infonnation for the COCs at the site are
the same as those presented in the EP A Integrated Risk Infonnation System
(IRIS) database, in which the criteria derivation is described. Some of the RiD
values chosen by EP A were derived by extrapolating from Subchronic studies to
chronic exposures using appropriate uncertainty and modifying factors.
Additional uncertainty can become part of the site analysis process when risk
evaluation criteria, such as th~ potency factors and RiDs, are applied to
constituents at concentrations equal to the detection limits, as described in the
EPA guidance (1989). For example, presence of vinyl chloride in groundwater at
or below the detection limit [0.5 microgram per liter (JJg/L)] could pose a cancer
risk of 3.3 x 10.5, assuming that a 70-kilogram (kg) individual ingests 2 liters per
day (Llday) of water for a 70-year lifetime. This satisfies the EPA-recommended
conservative assumptions to estimate the potential risks associated with exposure
to contaminants at a site. Thus, where data are insufficient, the potential risk
estimates represent most conservative risk numbers due to lack of more site-
specific infonnation.
6.2.2 Summarv of Toxicitv Information
Most of the chemicals identified at the site are volatile organic contaminants.
Other identified contaminants include arsenic, selenium, and bromacil. The most
commonly identified VOC is TCE, which has been classified by EPA.as a B2
(probable human) carcinogen. A summary of the. toxicity criteria used for
quantitative risk evaluation is included in Table 1.
6.3 ENVIRQNMENTAL FATE AND TRANSPORT
As part of the baseline risk assessment, the potential risk to offsite receptors due
to environmental migration of the site contaminants should be evaluated. To
accomplish this, it is necessary to derive exposure point concentrations for off site
receptors.
Based on the current knowledge of plume dynamics and the understanding of
groundwater flow at SHARPE, as described in the Rl report, the greatest
potential human exposure could occur along the western boundary of the site.
Based on data from the site and reasonable technical assumptions, plume
23
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C-SHADRlFS92.3/GWROD-H.l
03/31/92
Table 1. CiU"Cinogenic and Noncarcinogenic Toxicity Criteria for Chemicals Detected in Groundwater at SHARPE
Chemical Oral RID (UP). Inhal RID (UP). Oral CSp* Oral WoE. Inhal CSP- Inhal Wo£-
Miscellaneous Semivolatile Organic OIemicals (SOC)
Chloroethylvinyl ether. 2- 9.0£-0281 nd83
Dichlorobenzenes. total (1.000) 4.0£-0281 (1.000) 2.4£-02S2 C C
Volatile Organic C21emicaIJ (VOC) 2.0£-02VI (na)
8enzene 2.9£-02 A 2.9£-02 A
8romodichloromethane 2.0£-02 (1.000) 1.3£-01 82 ndV2 82
8romofonn 2.0£-02 (1.000) 7.9£-03 82 3.9£-03 82
8romomethane 1.4£-03 (1.000) 1.1£-03 (3.000)
Carbon tetrachloride 7.0£-04 (1.000) 1.3£-01 82 1.3£-01 82
N Chlorobenzene 2.0£-02 (1.000) 5.0£-03 (10.000)
."..
Chloroethane 2.8£+00 (300)
Chlorofonn 1.0£-02 (1.000) 6.1£-03 82 8.1£-02 82
Chloromethane 1.3£-02 C 6.3£-03 C
Dibromochloromethane 2.0£-02 (1.000) 8.4£-02 C ndV3 C
Dichlorodifluoromethane 2.0£-01 (100) 5.0£-02 (10.000)
Dichloroethane. 1,1- 1\0£-01 (1.000) 1.0£-01 (1.000) 9.1£-02v4 C' 9.1£-02v4. C
Dichloroethane. 1.2- 1.0£-02vS (100) 9.1£-02 C 9.1£-02 C
Dichloroethene.l.l- 9.0£-03 (1.000) 6.0£-01 C 1.2£+00 C
Dichloroethene. cis-l.2- 1.0£-02 (3.000)
Dichloroethene. trans-l.2- 2.08-02 (1.000)
Dichloropropane. 1.2- -- 6.8£-02 82 ndV2 82
Dichloropropene, cis-l.3- 3.0£-Q4V6 (10.000) 5.1£-03v6 (30) 1.8£-Olv6 82 1.3£-01v6 82
Dichloropropene. b"anS-l.3- 3.0£-04v6 (10.000) 5.1£-03v6 (30) 1.8E-Ol V6 82 1.3£-01v6 82
£thylbenzene 1.0£-01 (1.000) 2.9£-01 (300)
Methylene chloride 6.0£-02 (100) 8.6£-01 (100) 1.5£-03 82 1.6£-03 82
Tetrachloroethane. 1.1.2,2- 2.0£-01 C 2.0£-01 C
Tetrachloroethene 1.08-02 (1,000) 5.1£-02 82 1.8£-02 82
Toluene 2.0£-01 (1.000) 5.1£-01 (100)
~,.... .
-------
C-SHADRJPS92.3/GWROD-H.2
04/01/92
Table 1. Carcinogenic and Noncarcinogenic Toxicity Criteria for Chemicals Detected in Groundwater at SHARPE (Continued, Page 2 of 3)
Chemical
Inhal WoE.
Oral RID (UP).
Inhal RID (UP).
Oral CSp.
Oral WoE.
Inhal CSp*
Trichloroethane, 1,1,1- 9.0E-02 (1,000) 3.0E-Ol (1,000)
Trichloroethane, 1,1,2- 4.0E-03 (1,000) S.7E-02 C S.7E-02 C
Trichloroethene 4.0E-OIV7 (10,000) 1.IE-02 82 1.7E-02 82
TrichloroRuoromethane 3.0E-Ol (1,000) 2.0E-Ol (10,000)
Vinyl chloride 1.9E+00 A 2.9E-Ol A
Xylenes, total ~.OE+oo (100) 8.6E-02 (100)
Note:
N
VI
RID =
UP 0:::
MF...
CSP =
WoE ...
inhal =
na =
nd 0:::
Met a
NOAEL 0:::
mg/kg/day ""
",gIL =
LIday 0:::
reference dose [mg/kg/day).
uncertainty factor.
modifying factor.
cancer slope factor [(mg/kg/dayr1).
weight of evidence for ranking as an oral human carcinogen.
inhalation.
not applicable.
not determined.
EPA Maximum Contaminant Level.
no observed adverse effect level.
milligrams per kilogram per day.
miCrograms per liter.
liters per day.
(SI) No RID is available for this SOC; the listed value is for the related isomer 1,2-dichlorobenzene.
(S2) No CSP is available for this SOC; the listed value is for 1,4-dichlorobenzene.
(S3) Although EPA has classified this SOC as a Group C suspect human carcinogen via inhalation, no CSP has been developed for this exposure
pathway. .
-------
C-SHADRIFS92.3/GWROD-H.3
03/31/92
4
Table i. Carcinogenic and Noncarcinogenic Toxicity Criteria (or Chemicals Detected in Groundwater at SHARPE (Continued, Page 3 o( 3)
(VI) RID (or benzene based on the EPA 10-day Health Advisory of 0.235 mg/L (EPA, 1987) and assumes that a healthy 10-kg child consumes
1 L./day water. . . .
(V2) Although EPA has classified this chemical as a Group 82 suspect human carcinogen via inhalation, no CSF has been developed for this
exposure pathway. .
(V3) Although EPA has classified this chemical as a Group C possible human carcinogen via inhalation, no CSF has been developed for this
exposure pathway. .
(V4) No CSF is available for this VOC; the listed value is for the related isomer l,2.dichloroethane.
(VS) RID (or l,2~dichloroethane based on a chronic oral NOAEL (or rats o( 7 mg/kg/day (ATSDR, 1988) and an uncertainty (actor o( 100 (tOX
(or sensitive subpopulations and lOX for animal-to-human eXtrapolation).
(V6) No RID or CSF is available (or individuall,3-dichloropropene isomers; listed values are (or totall,3.dichtoropropene. .
(V7) RID for .trichloroethene based on. an acute lethal inhaled concentration in humans of 15,600 mg/m3, an uncertainty (actor of 1,000 (lOX
(or sensitive subpopulations, lOX for animal-to.human eXtrapolation, and lOX (or acute-to-chronic extrapolation), and a modifying (actor
of 10 Oethality) and assumes that a healthy 70-kg adult consumes 2 L./day water.
N
0\
*All RIDs, CSFs, and WoEs are from EPA, 1991a unless otherwise noted.
Source:
ESE.
-------
P/SHARPEIGWROD.13
11/11/92
movement has been predicted" using the Random Walk model. The model results
are in good agreement with the sampling analysis data (ESE, 1990). Currently,
the available analytical data indicate that four (Plumes 3, 4, 6, and 7) of the six
TCE plumes identified at SHARPE have migrated past the site boundary, reaching
the offsite groundwater. . If no remediation of the contaminant plumes occurs, in
time all six TCE plumes could migrate offsite. .
At SHARPE, TCE is generally found at the highest concentration in soils
associated with the A-aquifer zone. The predicted fate of the TCE contamination
is to: .
1. Volatilize into the soil pore spaces and eventually be lost from the
surface,
2. Migrate downward within the saturated Zl;ne to regions that are not
permeable to water or contaminant movement,
3. Disperse with the groundwater flow,
4. Bind to the soil particles, and/or
5. Undergo metabolic and chemical degradation.
The most significant of these environmental pathways is the downward vertical
migration of the contaminants to a banier region blocking further downward
movement. The migrated contamination is then dispersed and is driven .
horizontally by the groundwater flow gradients. Based on these migration
patterns, the Random Walk model predicts sequential additions of "particles"
proportional to the mass of the contaminants in each of the overlying aquifers,
taking into account the soil binding and chemical degradation factors. Therefore,
only a part of TCE in the A-aquifer zone will migrate to the B-aquifer zone and
then into the C-aquifer zone.
Because TCE was identified as the primary contaminant onsite, the risks due to
off site migration of the contaminants are limited to the risk associated with
exposure to TCE. The available information on the other site contaminants is
not sufficient to perform similar predictions. However, the risks associated with
other contaminants may be addressed by comparing the onsite contribution of
the non-TCE contaminants with that of TCE.
Analytical data indicate that not all of the site contaminants are present in all the
aquifers. Based on the available information, the contaminants not detected
27
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P/SHARPEIGWROD.14
11/11/92
..
. onsite will likely have little effect on off site contamination and, therefore, are not
considered in the off site exposure assessment. The cancer risk contributed by
each contaminant at or above the detection limits was estimated. In accordance
with RAGS, compounds with risk below 1 x 10-6, for which the frequency of
detection was low, and with a concentration less than two times the detection
limit were removed from further consideration. Following these data
assessments, two contaminants were identified to have significant contribution:
tetrachloroethene and carbon tetrachloride. Five additional cases were identified
in which the contribution of either tetrachloroethene or carbon tetrachloride to
the offsite exposure is considered significanL These compounds were included
for further evaluation of the risks to the offpost receptors (Table 2).
6.4 EXPOSURE ASSESSMENT
The objective of the exposure assessment is to estimate the types and magnitude
of exposure to the chemicals of concern present in on- and off site groundwater.
The results of the exposure assessment are combined with the chemical-specific
toxicity information to characterize potential risks from exposure to
contaminated groundwater.
An exposure assessment is the detennination of the magnitude, frequency,
duration, and exposure route. Exposure is defined as the contact of any receptor.
(human, animal, or plant) with a chemical or physical agent. The magnitude of
exposure is determined by measuring or estimating the amount of an agent
available at' the exchange boundaries (i.e., the lungs, gut, skin) during a specified
time period. The frequency and duration of exposure are functions of the
.exposure route (EPA, 1989).
Potential onsite groundwater eXposure pathways include exposure to the
contaminated potable water supply weDs at the facility, even though the weDs
may not be currently influenced by the contaminant plumes. Although all onsite
groundwater exposure pathways are considered incomplete, current onsite data
will be used to provide a conservative estimate of the potential human health
risk. Thus, for potential off site exposures, the following two hypothetical
receptor populations have been evaluated: . . .
1. A population that uses water from each contaminant plume area, and
2. A population that uses the groundwater in the future after the
contaminants migrate offpost and reach the downgradient residential
weDs. .
28
-------
p/SHARPEIGWROD.V.1
11/11/92
Table 2. Potential Cancer Risks. Nsociated with Offsite Exposure to Tetrachloroethene and
Carbon Tetrachloride Using Onsite Data in Groundwater plumes at the Highest Risk"
Muimum Mean
Concentration Concentration Maximum Mean
Plume Aquifer (~g/L) (~g/L) Risk Risk
Tetrachloroethene
7 A 38 3.59 55.4 5.23
7 B 25.6 3.56 37.3 5.18
7 D 5.30 2.40 7.72 3.50
Carbon Tetrachloride
4 A 47 2.16 175.0 8.03
1 C 4.90 1.13 18.2 4.19
-Risks/million after a lifetime of exposure.
.. All other plumes are expected to have less risk associated with potential exposure.
Source: ESE.
29
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P/SHARPEIGWROD.15
11/11/92
Based on the results of this evaluation, the significant off site exposure pathways
are (1) oral exposure to groundwater through ingestion; and (2) inhalation'
exposure to airborne contaminants as a result of volatilization into a home
during the residential use of groundwater (showering, etc.). At this site, denna1
exposure is expected to conttibute less than 1 percent of the total intake (EP A,
1989) due to the nature of the contaminants found at the site.
6.4.1 ~ Concentrations
Two sets of data are considered for exposure point concentrations for potential
offsite exposures; the first set uses measured data to represent potential
exposure. The exposure point concentrations are assumed to be equivalent to
the concentration identified in each plume/aquifer combination; these are
summarized in Table 3. The second data set uses measured data wrich are
modified using the Random Walk model. The modeled exposure point
concentrations represent future exposure at boundary conditions and are
presented in Table 4.
i
, ~
6.4.2
tion of Pathwa -8
. c Chemical Intakes
Having identified the complete exposure pathways to be evaluated and estimated
the exposure point concentrations, these values can be combined with standard
or site-specific exposure factors to calculate the estimated dally contaminant
intake. .
Two scenarios have been selected to represent potential exposures to the
receptor. The first scenario simulates a reasonable worst case, while the second
scenario represents the best estimate or average exposure. For the worst-case
scenario, it is assumed that an individual is exposed to a reasonable maximum
concentration, which may be the maximum value observed (onsite data) or may
be the representative maximum exposure (RME), which is represented. by the
95th percentile concentration (modeled data). For the average exposure, an
individual is presumed to be exposed to the most likely exposure (MLE), or the
mean value.' .
6.4.3 In estion of
Water
Because these are tWo distinct scenarios, different values were assigned to many
. of the para.I'(1eters.
30
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P/SHARPE./GWROD.V.2
11/11/92
Table 3. Measured TCE Concentrations in Each Plume/Aquifer
AQuifer
B C D
Max ML.E Max MLE Max MLE
1,200.00 44.36 540.00 34.07
A
Plume Max MLE
1 2,600.00 127.00
2 12.80 4.5~
3 349.00 20.28
4 (4 & 5) 620.00 108.50
6 12,000.00 286.50
7 (7 & 8) 5,400.00 306.90
OVERALL VALUES
MLE 62.8
RME 695
68.80 12.78 1.00 0.53
81.60 14.72 240.00 32.07
7,260.00 200.40 160.00 12:64
377.00 14.25 136.00 13.75 13.30 2.56
Note: All concentrations are in ~g/L.
- = not detected.
Max = maximum.
Source: ESE..
31
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P/SHARPEIGWROD-V.3
11/11/92
Table 4. Modeled TCE Concentrations in E.ach Plume/Aquifer
AQuifer
A B C Total Plume
Plume RME. MLE. RME. MLE. RME. MLE RME. Ml.E
1 106 39 48 20 67 23. 78 28
.
4 (4 & 5) 131 62 109 41 70 26 101 42
.. 6 1,225 2.2S 1,221 228 428 107 1,069 267
7 (7 & 8) 918 272 249 68 228 67 684 178
Total Aquifer 1,000 195 S79 146 230 S4 637 128 '
OVERAll. VALUFS
MLE 128
RME 637
Note: All concentrations are in ~gIL.
Total Aquifer = The overall RME or M1.E at the western boundary over time for that aquifer.
Source: E.SE.
32
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P /SHARPEIGWROD.16
11/11/92
6.4.4 Dermal Contact
In general, the denna1 absorption of halogenated VOCs is very low. However,
monoaromatic compounds like benzene could be absorbed through skin quite
efficier.tly, but the concentrations of such compounds in groundwater at SHARPE
are very low and contribute little to the overall risk. Also, no existing exposure
pathway is identified for onsite contaminants, and based on the nature of the
contaminants found at the site, the denna1 exposure pathway is not considered to
be a significant additional exposure pathway when compared with potential
exposures via direct consumption and inhalation.
6.4.5 Inlut1;ation
Int8ke through the inhalation route is a potentially significant exposure pathway.
According to EPA '(1987), the amount of additional intake through inhalation is
approximately equal to the amount taken in through the oral route. This
generalization includes the consideration of the slightly different slope faCtors.
Multiplying the oral intake by a factor of tWo incorporates the inhalation
exposure.
, .
6.4.6 Identification of Uncertainties
Under the existing groundwater usage conditions, no identifiable exposure points
to. the contaminant plumes onpost exist; therefore, the exposure pathway is
incomplete. To protect human health, the conservative assumption that the
exposure point concentrations are the same as the concentrations observed in the
groundwater samples is used. To increase the conserVative nature of this
approach, the fate and transport model does not allow for the biodegradation
and volatilization processes that affect the contaminants over time. This
appro.ach, therefore, represents a worst-case scenario for exposure to
contaminants that have migrated offpost.

. .
6-5 RISK CHARACTERIZATION
The purpose of the baseline risk assessment is tWofold:

1. Identify impaCts to human health and the environment using the no-
action alternative, which assumes that no site remediation is
undernay; and
2. Provide a basis for the evaluation of potential remedial alternatives.
33
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P/SHARP£lGWROD.17
11/11/92
Excess lifetime cancer risks are determined by multiplying the intake level with
the cancer potency factor. These risks are probabilities that are generally
expressed in scientific notation (e.g., 1 x 10-6 or 1£-6). An excess lifetime cancer
risk of 1 x 10-6 indicates that, as a plausible upper bound, an individual has a
one in one million chance of developing cancer as a result of site.,re1ated
exposure to a carcinogen over a 70-year lifetime under the "specific exposure
conditions at a site. .
Potential concern for noncarcinogenic effects of a single contaminant in a single
medium is expressed as the hazard quotient (HQ) (or the ratio of the estimated
intake derived from the contaminant concentration in a given medium to the
contaminant's reference dose). By adding the HQs for all contaminants within a
mediUm or across all media to which a given population may reasonably be .
exposed, the Hazard Index (HI) can be generated. The HI provides a useful
reference point for gauging the potential significance' of multiple. contaminant
exposures within a single medium or across media.
.
i
, ~
Risk characterization, the final step in the baseline risk assessment process,
integrates and summarizes the toxicity and exposure assessment information to
produce quantitative risks associated with exposure to site contaminants. To
characterize the potential carcinogenic effects, probabilities that an individual
will develop cancer over a lifetime of exposure are estimated. Excess lifetime
cancer risks are determined by multiplying the intake level with the CPF. These
risks are probabilities that are generally expressed in scientific notation (e.g.,
1 x 10-6 or 1E-6). An excess lifetime cancer risk of 1 x 10-6 indicates that, as a
plausible upper bound, an individual has a one in one million chance of
developing cancer as a result of site-related exposure to a carcinogen over a
70-year lifetime under the specific exposure conditions at a site.
Under current conditions, no known receptors are exposed to the TCE plumes or
to the isolated areas of arsenic contamination in the groundwater. Wells found
to be contaminated with TCE in the past have been closed and new, deeper wells
installed for potable water use. Even though no exposure pathway to onsite
groundwater has been identified, the risk associated with exposure to the
contaminant levels identified in the onsite groundwater has been detennined in
the unlikely event that potable wells were installed, either onsite or off site, into
the A-, B-, or C-aquifer zones.
In addition, a hypothetical future scenario in which residential exposure results
following the offsite migration of contaminated groundwater has been evaluated.
The potential risks resulting from such exposure are presented for each plume of
34
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P/SHARP£lGWROD.18
11/11/92
contamination using both CWTent onsite data, Is described previously, and the
anticipated future contaminant levels as modeled at the site boundary.
Extensive groundwater contamination has been identified in several regions of
the SHARPE facility. It is probable that, without remedial intezvention, DOnna!
hydrogeological interactions will result in the movement of ~emi~ constituents
across the site boundaries. Once contaminants have migrated beyond the
confines of the site, it is possible for a variety of receptors .to be exposed to toxic
and carcinogenic compounds. Currently, the likelihood of .completing an
exposure pathway is remote; no human or other ~vironmental receptor is
CWTently at risk. The chemicals that have been evaluated as potential COCs in
the groundwater are arsenic, selenium, bromadl, and a suite of volatile
halogenated organic compounds. TCE is the single contaminant that is found
most frequently, occurs at high concentrations, and migrates from the site. The
associated health and environmental risks have been identified and described for
each contaminant, assuming the no-action alternative.
Extensive examination of the site has not provided evidence that arsenic and/or
selenium were associated with past site activities. Localized regions of elevated
levels of arsenic in the shallow A-aquifer zone groundwater have been identified,
both off site and onsite.
Potential carcinogenic and toxic risks to human health are associat~d with the
exposure to observed arsenic concentrations. The. arsenic levels are elevated
sufficiently to influence the use of waters that are extracted from groundwater at
the site. The distribution of selenium appears to refleCt natural occurrence and is
similar to concentrations found throughout the San Joaquin Valley [Sec. 6.0,
ESE, 1990; U.S. Geological survey (USGS), 1984-1986; 1989]. .
. .
Bromadl is a herbicide that has been regularly Used at the site and has been
identified at one shallow monitor we11location( 407 A) at concentrations that
equal or exceed the California Water Quality Goals. The concentrations of
bromacil are sufficiently high to potentially require remediation, or influence the
selected use of groundwater derived from that isolated region or well.

VOCs detected at the site are numerous. Only TCE has been found at many
locations around the site at groundwater concentrations that indicate a potential
risk to human health and the environment. The site data were presented to
describe the widespread distribution, the range of concentrations currently found
in the groundwater, and to project concentrations expected at the site boundary
under the conditions of a no-action alternative. Summary statistics were
presented in the risk assessment report (ESE, 1991b), to identify and estimate
35
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P/SHARPEIGWROD.19
11/11/92
the potential risk to human h~th and the environment. Under reasonable
worst-case scenarios, the RME concentrations of TCE in groundwater were
identified and desaibed as exceeding the upperbound limit of 100 excess cancers
per million population risk following a ~etime of exposure (Table 5).

MLE of the .TCE concentrations occurring in the gro~dwater under the site were
evaluated (Table 5). The risks associated with a wide variety of exposure .
concentration levels at the site are generally betWeen the 1 to 100 excess cancer
risks in a million and the 100 in a million risk is the EPA acceptable risk at
Superfund sites [Office of Solid Waste and Emergency Response (OSWER)
Directive 9355.0-30; EPA, 1991]. The sum of the risks associated with
contaminants other than TCE represent a very small contributing factor to the .
overall risks associated with exposure to contaminated groundwater at SHARPE.
In conclusion, the potential risks associated with the exposure to the site ;
contaminants are synonymous to the exposure to the TCE at the site. Currently, ' ..
the potential for exposure to the human populations and the environment, onsite
or off site, is insignificant. The risks associated with a variety of hypothetical
exposuresc:enanos, as described, provide the potential risk infozmation upon
which the identification of the need for remediation and selection of remedial
alternatives should be made.
Actual or threatened releases of hazardous substances from this site, if not
addressed by implementing the response action in this ROD, may present an
imminent and substantial endangerment to public health or welfare or the
environment.
7.0 DESCRIP110N OF ALTERNATIVES
The groundwater FS for SHARPE was presented to EP A and the State of
California in November 1991. SHARPE, USATHAMA, DTSC, CVRWQCB,. and
EPA have evaluated five remedial alternatives: .
1. . Alternative lA--Groundwater .Extraction and Air Stripping,
2. Alternative 1 C--Groundwater Extraction and Granular Activated Carbon
(GAC) Treatment,
3. Alternative 2B--Groundwater Extraction and Ozonation with Ultraviolet
(UV) Light and Hydrogen Peroxide (H20J,
36
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C-SHADRIFS92.2/GWROD.ASC.l
03/16/92
Table 5. Potential Caricer lialta uaociatad with £qIOSUre to cq,oat Monitor Water wella
lIME tILE tk8er of
Pline Analyte Unita .. liat MLE liat Nita
All Contaminants Eaceot Arsenic
PLIICE: 1 AO: A nneE 8I/L 3_59£-04 4..-07 3.44l-04 9.68E-08 5
nDeE 8I/L ).74(-04 7.91£-06 3.55£-04 1.W-Q6 15
1meL£ 88/L 4.JOE-04 9.19£-07 4.8-04 1.m-07 27
1meLP 8I/L 4.39£-04 3.51£-07 4.15£-04 6.95£-08 10
IIDCUt 8I/L 3.64E-04 5.561-07 3.481-04 1.12£-07 5
C13DCP 88/L 3_84£-04 1.4OE-06 3-W-04 2.79£-07 2
CZIl3CL 88/L 4.09£-04 1.82£-OS 3.89£-04 3.64£-06 . 12
C6II6 88/L 3_671-04 2.5CIE-07 3_52£-04 5.CI3E-08 14
. teL4 8I/L 5_7lE-04 1.761-06 5.431-04 3.481-07 25
Cll2eL2 88/L 1.31£-03 3.61£-07 1.19£-03 6.89£-08 48
CMBR3 88/L 4.39£-04 6.- -08 4.08E-04 1.191-08 5
CNeL3 88/L 1.7IE-03 1.82£-06 1.6OE-03 3.44l-07 94
DeLI 88/L 3_81£-04 1.071-07 3.63(-04 2.15£-08 5
TeLEA 8I/L 3.53E-04 1.W-06 3.39£-04 3_34£-07 5
TeL££ 8I/L 5.5DE-04 4.4M-07 5.19£-04 l.m-08 49
TleLE 8I/L 4_62£-01 1.52E-04 3.73E-01 2.571-OS 365
TOTAL PLUME: 1 AO: A 1.UE-04 3.3OE-OS
PLUME: 1 AO: B uneE 8I/L 3.m-04 4.JOE-07 3._-04 1.65£-08 1
11DeE 8I/L 3.47F.-04 7.m-06 3.25£-04 1.44l-06 6
1meL£ 8I/L 3.oa.04 6.W-07 2.96E-04 1.DE-07 2
1meLP 8I/L 3.481-04 2.7IE-07 3.3OE-04 5.53E-08 2
lRDeLM 8I/L 3.45£-04 5.261-07 3.271-04 1.OS£-07 7
e13DCP 88/L 3.2OE-04 1.171-06 3.o6E-04 2.34£-07 1
CZIl3CL 8I/L 3.52£-04 1.571-OS 3.35£,04 3.14£-06 1
C6II6 8I/L 3.62£-04 2.4M-07 3.41£-04 4.8-08 7
teL4 8I/L 4.42£,04 1.35E-06 4.12£-04 2.64£-07 9
CN2eL2 8I/L 2.58£-03 7.11£-07 2.11£-03 1.22£-07 37
elllR3 8I/L 3.73E-04 5.161-08 3.51£-04 1-02£-08 9
CNeL3 88/L 7.071-04 7.23£-07 6.43('04 1._-07 77
DIReL" 8I/L 3.561-04 3.52£-07 3.371-04 6.971-08 5
DCLI 8I/L 3.25£-04 9.15£'08 3.10£-04 1..-08 1
Tew 8I/L 3.18£-04 1.50£-06 3.05£-04 3.01£-07 1
TCL££ 8I/L 4.2OE-04 3.4OE-07 3.95£-04 6.71£-08 24
TICL£' 88/L 4.14£-02 1.W'OS 3.22£-02 2.22£.06 245
TOTal PUlE: 1 AO: I 4.51£-OS 8.45£-06
PLIICE: 1 AD: e 11neE 8I/L 3.4M-04 4.631-07 3.03£-04 1.53E-08 1
11DCE 8I/L 2_93E-04 6.19£-06 2-771-04 1.231-06 2
1meLE 88/L 3.22£-04 6.88£-07 .3.05£-04 1.371-07 1
1meLP 8I/L 3.45£-04 2.761-07 3.25£-04 5.44£-08 1
IIDeLM 88/L 3.4OE-04 5.19£-07 3~22E-04 1.CI3E-07 6
CZH3eL 88/L 3.75£-04 1.671-OS 3.51£-04 3-29E-06 3
C6II6 81/.1, 3.2OE-04 2.18£-07 3.05E-04 4.W-08 5
teL4 88/L 1.22£-03 3.73E-06 1.05E-03 6.741-07 61
Cll2CL2 8I/L 2_171-03 5."-07 1. 7OE-03 9.13E-08 25
CIIIR3 88/L 4__-04 6.071-08 4.01E-04 1.171-08 11
CMCL3 88/L 1.91E-03 1.96E-06 1.68£-03 3.6OE-07 84
DIReL" 8I/L 3.511-04 3.4M-07 3.29E'04 6.81£-08 7
DCLI 8I/L 3.871-04 1.09£-07 3.571-04 2.11£-08 1
TCLEA 88/L 3.12£-04 1.4M-06 2."-04 2.941-07 1
TCLEE 8I/L 3.371-04 2.73E-07 3.zoe-04 5.441-08 4
TleLE 88/L 8.69£-02 2.86£-05 5.971-02 4.12£-06 174
TOTAL PLUME: 1 AO: C 6.22£-OS 1.06E-OS
PLUME: 2 AO: A CH2eL2 8I/L J.171-03 a.71,£-07 1.39£-0] 8.04£-08 1
TeLE£ ~/L 7.771-04 6.50E-07 5.35£-04 9.09£-08 2
TlelE IIII/L 5.75E-03 1.89£-06 4.34£.0] 3.00£-07 15
TOTAL PLUME: 2 1.0: A 3.39£-06 4.71£-07
37
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- -" --.-.
C-SHADRlFS92.2/GWROD.ASC.3
03/16/92
Table 5. Potential Cancer lists. Associated vlth bposure to ~t Monitor Water Wells
(Continued, Paee 3 of 4)
- ..lE ~rof
PLune Anllyte Unite IttI£ Iisk IILE Iialt Hits
PLUME: , AQ: C 112TCE 88/l 3.08E.04 4.13£-07 2._-04 1.09£-08 2
nDeE 88/l 3.01E~ 6~35E-06 2.17E-04 1.23£,06 1
12DCLE 88/L 3.571-04 7.64E'07 3~ 14E-04 1.41£-07 1
12DCLP IIIIL 3.96£-04 3. 16E,07 3.W-04 5.80£-08 1
IRDCU' 88/L 3.92£'04 5._'07 3.44E-04 1.10£.07 1
C13DCP I118/L 3.98£.04 1.45E-06 3.47(-04 2.66E-07 1
C2H3CL 88/L 3.8OE-04 1.TOE'05 3.47(-04 3.25E-06 1
C6H6 II8IL 3.6IE-04 2.51£-07 3.33E-04 4.m-08 Z
teL4 . 88/L 5.11E-04 1.W-06 4.37(-04 2.80£-07 1
CMZCL2 88/L 2.31E'0] 6.37(-07 1.57(-0] 9.09E-08 11
CMlR3 88/L 4.29£-04 5.N-08 3.65E-04 1.06£-08 1
CHCLS 88/L 4.13£-04 4.23£-07 3.69£-04 7.91E-08 2
DIRC.... 88/L 3.04E-04 3.DOE-07 2.I5E-04 5.90£-08 1
DCLI 88/L 4.16E-04 1.171-07 3.69£-04 2;,.-08 1
TCLEA 88/L. 3.22£-04 1.51E-06 3.01£-04 2.m-07 1
TCLEE 88/L 3.42£.04 2.17E-07 3.13£-04 5.W-08 1
TICLE 88/L 2.21E-01 7.26£-05 9.56£-02 6.60£-06 61
TOTAL PLUME: 4 AQ: C 1.05E-04 1.27(-05
PLUME: 6 AQ: A 11DeE 88/L 3.971-04 8.39£-06 3.26E-04 1.45E-06 1
12DCL£ 88/L 5. 9ftE -04 1.27(-06 4.67(-04 2.10£-01 1
CCL4 88/1 7. 11E-04 2.1n-06 5.55E-04 3.W-07 1
CMZCL2 88/L 2.29£-0] 6.31£-07 1.44E-0] 1.33£-08 5
CHCLS 88/L 7.26£-04 1.42£-07 5.W-04 1.19£-01 2
DCLI . 88/L 1.15E-0] 3.23£-07 7.48£-04 4.42£-08 1
TCLEE 88/L 4.91E-04 3.98£-07 3.19E-04 6.62£-08 1
TICLE 88/L 3.90£-0] 1.21£-06 2.01£-0] 1.39£-01 5
TOTAL PLUME: 6 AQ: A 1.52£-05 2.W-06
PLUME: 6 AQ: I 11DCE 88/L 4.1IE-04 8.&3E-06 3.41E-04 1.51£-06 1
CH2CLl 88/L 3.l.6E-0] 9_54£-07 1.83E-0] 1.06£-07 1
CHCL3 88/L 5.03E-04 5. 14E-07 4.11£-04 8.83E-08 1
TICLE I118/L 2.5n-01 8.43£-05 4.I4E-02 3.34E-06 14
TOTAL PLUME: 6 AQ: I 9.W-OS 5.05E-06
PLUME: 6 AQ: C CMZCLZ I118/L 2.I4E-0] 1.85E-07 1.42£-0] 8.21E-08 3
TleLE 88/L 9.36E-0] 3.08E-06 Z.91£-0] Z.05£-01 6
TOTAL PLUME: 6 AQ: C 3.86E-06 2.11£-01
PLUME: 7 AQ: A "ZTeE 88/L 4.75£-04 6.W-07 4.22£-04 1.19£-07 1
11DeE I118/L 4.23£-04 8.94E-06 3.74£-04 1.66E-06 2
12DCLE 88/L 5.15E-04 1.10£-06 4.53£-04 2.03£-07 2
12DeLP II8IL 5.73f-04 4.58£-07 5.DOE-04 1.3IE-08 1
laoCLM II8IL 6.11£-04 9.33E-07 5.29£-04 1.70(-07 3
C13DCP II8IL 5.94E-04 2. 16E-06 5.16E-04 3.95E-07 2
C2I13CL III8IL 5.81£-04' 2.62£-OS 5. 14E-04 4.I2E-06 1
C6tI6 III8IL 4.5ZE-04 3.08£-07 4.05E'04 5.79£-08 1
teL4 I118/L 8.44£-04 1.58£-06 7. 1ZE-04 4.51£-07 4
CH1CU 88/L 2.55E-0] 7.03£-07 1.92£.0] 1.11£-07 15
CHIRS 88/L 6.8OE-04 9.42£-08 . 5.8OE-04 1.69£-08 3
CHCL3 88/L 7.81£-04 1.06£-07 6.70£-04 1.44E-07 13
DIRC"" I118/L 5.14£-04 5.0n-07 4.52£-04 9.W-08 4
Deli 88/L 7.171,04 2.0ZE-07 6.04E.04 3.51£-08 1
TCLEA I118/L 5.11£-04 2.40£-06 4.53E-04 4.47(-07 3
TCLEE I118/L 4.51E-03 . 3.65E-06 3.32E-0] 5.65E-07 65
TICLE I118/L 4.32E-01 1 .42(.04 1.92£-01 1.33E-05 102
TOTAL PLUME: 7 AQ: A 1.94E-04 ' 2.27(-.05
39
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C-SHADJUFS92.21GWROD.ASC.4
03/16/92
Table 5- Potential cancer liata Aaaociuect with £xposure to ~t Monitor Water Well.
(ContiftYld, Pate I. of 4)
.. 8Il£ IYIber of
PILllle ANlyte unita lIME liak IClE liak lIita
PLiME: 7 ACI: . 11DCE IIIII/L 3.18£.-04 6.7'2£-06 2-89£-04 1.21(-06 1
1ZDCLE IIIII/L 3.60(-04 7-7OE-07 S.33f-04 1.49£-07 5
1ZDCLP IIIII/~. 3.76E-04 3.01£-07 3.4n-04 5.81E-08 1
C2H3CL IIIII/L 4.121-04 1.84E-05 3.19£-04 3.55£-06 3
eel 4 IIIII/L 5.78£-04 1.m-06 5.08E-04 3.25E-07 10
CHZCL2 IIIII/L 1.44E-03 3.m-07 1.13£-03 6.53£-08 15
CIICL3 IIIII/L 3.93£-04 4.01£-07 3.62£-04 7.78£-08 4
TCLEE IIIII/L . 4-06E-03 3.29£-06 2.95E-03 5.02E-07 65
TICLE IIIII/L 2.16E-02 7.10£.06 1.~:02 '.80£-07. 101
TOTAL PUllE: 7 ACI: . 3.91E"05 6.99£-06
PLUME: 7 ACI: C 1ZDCLE . I11III L 3.W-04 7.44£-07 . 3.21£"04 1.44E-07 4
IRDCLM lIIIIiL 4.2tE-04 6.55E-D7 3.84E-04 1.DE-07. 3
C2H3Cl IIIII/L 3.82£-04 1.71£-05 3.5a-04 3.SOE-06 1
eel' IIIII/L 4.69£-04 1.43£-06 4.15E-1)4 2.W-07 1
C112CL2 IIIII/L 1.89£-03 5.23£-07 1.39£-03 8.06E-08 15
CIIBR3 IIIII/L 5_75E-04 7.ME-08 4.W-04 1.41E-08 3
CHCL3 IIIII/L 3.82£-04 3.91£-07 3.51£-1)4 7.53£-08 4
DI.CLM IIIII/L 3.37E-1)4 3.32£-07 3.13£-1)4 6.49£-08 2
TCLEE IIIII/L 7.53E-04 6.10£-07 6.31E-1)4 1.0n-07 21
TICLE IIIII/L 2.85E-02 '.37E-06 1.65£-02 1. "£-06 76
TOTAL PUllE: 7.ACI: C 3.121-05 5.S1E-06
PLiME: 7 ACI: CD C6II6 I11III L 4.m-04 3.38E-07 3.45£-1)4 4.93£-08 2
CHZCL2 IIIII/L 4.89£-04 1.35E-07 3.S6E-04 2.06E-08 . 1
TCLEE IIIIIIL 6.06E-04 4.91E-07 3.71E-1)4 6.31E-08 1
TICLf IIIII/L 6.DOE-OJ 1.97E-06 1.72£-03 1.1Pf-07 6
TOTAL PUIIE: 7 ACI: CD 2.94E-06 2.521-07
PLiME: 7 ACI: D C6II6 IIIII/L 3.69£-04 2.51E-07 3.11£-1)4 4.44£-08 1
CHZCLZ IIIII/L 3.66£-03 1.01£-06 1.2OE-03 6.961-08 2
TCLEf IIIII/L 3.00E-03 2.43£-06 2.11E-03 3.6OE-07 10
TICLE IIIII/L 4_9OE-03 1.61£-06 2.10£-03 1.'5£-07 . 10
TOTAL PLUME: 7 ACI: D 5.3OE-06 6. '.-07
Source: ESE.
40
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4. Alternative 3D--Groundwater Extraction and Fixed-Bed Biological
Treaanent Towers, and
5. Alternative 6A--No Action.
7.1 GROUNDWATER EXTRAcnON
With the exception of the no-action alternative, all alternatives include the same
groundwater recovery system. As arsenic, selenium, and nitrates in groundwater
were not attributable to past or current site activities, capture of groundwater
contaminated with these constituents was not an objective of remediation. Given.
this infonnation, of those contaminants described in Sec. 5.0, only VOCs and
bromacil were considered for conceptual design of a groundwater extraction
system.
One significant variable in groundwater modeling is definition of the
contaminant-specific cleanup objectives. The primary objectives of the remedial
action for groundwater at SHARPE are to mitigate potential long-term .
contaminant migration and protect human health and the environment. An
evaluation of groundwater characteristics was perfonned to assess its risk to
human health. Table 6 defines those compounds in groundwater which. pose a
concern to human health and the environment. A risk assessment was perfonned
to detennine the risk that groundwater, as it currently exists, presents to human
health; the risk assessment also defined cleanup levels required to meet various
objectives related to the protection of human health. The details of the risk
assessment are presented in the risk assessment report (ESE, 1991 b) and are
summarized in Sec. 6.0.
Table 7 defines tWo different cleanup levels as they relate to cancer risks:
1.
Concentrations of TCE in groundwater required to achieve
an overall cancer risk of 1E-6, when other carcinogens are
reduced to levels below detection limits (0.5 Io'g/L); and
2.
Overall cancer risk associated with cleanup ofTCE to .
5 Io'g/L, when other carcinogens are reduced to levels below
detection limits. .
Since contaminated groundwater is not present in an area pumped for potable
water supply, Objective 1 was considered too stringent. Therefore, Objective 2
will be used as the treaanent objective for carcinogens. Objective 2, at a
minimum, is compliant with federal and state applicalbe or relevant and
41
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Table 6. Compounds in GroUndwater Which Pose a Concern to Human Health
and the Environment .
VOC~
Benzene*
Bromadl
Bromoform*
BromodicbJoromethane*
Carbon tetrachloride*
. Chloroform * . .
Dibromochloromethane*
Dichlorobenzene
l,l-Dichloroethane
1,2-Dichloroethane*
l,l-Dichloroethene (cis and trans)*
1,2-Dichloroethene (cis and trans)
1,2-Dichloropropane*
1,3-Dichloropropene (cis and trans)*
Methylene chloride*
l,l,l-Trichloroethane
1,1.2-Trichloroethane*
1,1,2,2-Tetrachloroethane*
Tetrachloroethene*
Trichloroethene*
Toluene
Vinyl chloride*
Xylene (total)
1
, .
*Carcinogen, or suspected ~arcinogen.
Source: ESE.
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Table 7. TCE Remedial Concentrations Equivalent to a Cancer Risk of 1E-6 for
all Carcinogens and the Total Cancer Risk Associated with a Reduction
of TCE to the ARAR of 5 /Jg!L
TCE Aquifer
. Remediation Goal Total Cancer
Equivalent to a 1E-6 Risk When
.Plume Cancer Risk (/Jg!L) TCE is 5 /Jg!L
1 A 1.05 4.75E-6
B 0.61 8.16E-6
C 0.49 1.03E-~
D 1.62 3.08E-6
3 A 0.33 1.50E-5
B 0.21 2.38E-5
4 A 1.15 4.34E-6
B 0.18 2.37E-5
C 0.49 1.02E-5
6 A 1.98 2.52E-6
B 1.71 2.92E-6
C 0.22 2.27E-5
7 A 1.95 2.57E-6
B 0.22 2.27E-5
C 0.21 2.41E-5
Plume/aquifer combinations 2A, 3C, 4AB, 7CD, and 7D are not included in this
table because the cancer risk for both the maximum and the mean concentrations
(TCE concentrations average less than 5 /Jg/L) are less than the lower bound of
1E-06. .
Source: ESE.
43
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PISHARPE/GWROD.21
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approprate requirements (AR!JU) for groundwater contaminants listed in
Table 6.
7.1.1
.'
Table 8 lists Aquifer Cleanup Levels (i.e., the concentrations of contaminants to
which the aquifer must be restored through remediation). Both State and
Federal applicable or relevant and appropriate requirements (ARARs) were
evaluated for selection of aquifer cleanup levels. Additionally, the Health Risk
Assessment, desaibed in Section 7.1, was utilized. '
Other contaminants found at the site, specifically bromadl, ethylbenzene, '
toluene, arid xylene, may be regulated under a Cleanup and Abatement order to
be adopted by CVRWQC8, consistent with the California Water Code. SHARPE
reserves its right to challenge an order, as allowed by the California Water Code.
Any additional groundwater contaminants or compounds identified in subsequent
efforts will be addressed as part of the sitewide comprehensive ROD.

The aquifer cleanup levels are protective of human health and the environment
and will protect beneficial uses of the groundwater. SHARPE will design;
construct; operate; and, if necessary, modify the groundwater extraction
netWorks to comply with the aquifer cleanup levels. If at some later date (i.e.,
during a S-year review) it is detennined that ,it is infeasible to achieve the aquifer
cleanup lev~s specified in Table 8, the aquifer cleanup levels will be reevaluated
by SHARPE, EPA, DTSC, and CVRWQCB.
,
.. ~
7.1.2
reatmentPlant Effluent Dischar e Standards
Table 9 lists the effluent discharge standards that apply to the onsite discharges
to land from the treatment plants. These discharges include reinjection and
disposal using ponds. Off site discharges (i.e., surface water disposal) are
regulated by a National Pollutant Discharge Elimination System (NPDES) pennit
issued by CVRWQC8. The effluent discharge stand~ds were negotiated betWeen
SHARPE and CVRWQC8 and are consistent with the Eftluent Limitations in the
Substantive Waste Discharge Requirements (WDRs), which are included in this
ROD as an attachment. The effluent discharge standards were established for the
major contaminants of concern: trichloroethylene (TeE) and tetrachloroethylene
(PCE), as well' as for other groundwater contaminants, including bromaci1,
benzene, and total BTXE (benzene, toluene, xylene, and ethylbenzene). The
"total VOCs" effluent discharge standard specified in Table 9 will generally
include the volatile compounds listed individually in Table 8. The effluent
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Table 8. Remedial Perl'ormance Standards - Aquifer Remediation Levels
Aquifer Cleanup
Constituent Level (~g/L) Comments.
Benzene .. Human Risk Assessment CHRA:I
Bromacfi ..
Bromodichloromethane 0.5 HRA
Bromoform 0.5 HRA
Carbon Tetrachloride 0.5 liRA
Chloroform 0.5 HRA
Dibromochlorometi)ane 0.5 HRA
Ortho-Dichlorobenzene 10 California DHS Action Level
Para-Dichlorobenzene 5 California Primary Me.
l,2-Dichloroethane 0.5 HRA
l,l-Dichloroethene o.s liRA
Cis-1,2-Dichloroethene 6 California Primary Me.
Trans-1,2-Dichloroethene 10 California Primary Me.
l,l-Dichloroethane 5 California Primary Me.
l,2-Dichloropropane 0.5 liRA
l,3-Dichloropropene 0.5 HRA
Ethylbenzene "
Methylene Chloride 0.5 HRA
l,l,l-Trichloroe~e 200 California Primary Me.
l,l,2-Trichloroethane 0.5 HRA
1,1,2,2- Tetrachloroethane 0.5 liRA
Tetrachloroethene (PCE) 0.5 HRA
Trichloroethene (TCE) 5 EPA and California Primary Me.
Toluene ..
Vmyl Chloride 0.5 liRA
Xylene ..
"Aquifer remediation levels for these constituents will be regulated under a separate order
adopted by the Regional Board because the constituents are not CERCLA hazardous $ubstances
as determined by EPA and the state.
Source: EPA, 1992.
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Table 9. Remedial Action Performance Standards - Effluent Discharge Standards*
Constituent
Effluent Dischanze Standards (usz/L)
Maximum Daily Monthly Median
Concenttation Concenttanon
Tettachloroethanet
Tric:h1oroethenet
Total Volarlle Organic Constituents (VOCS)**
Arsenic
Selenium
Nittate
Bromadl
Benzene
BTXEtt
"1.0
1.0
5
5 or background***
5 or background***
10 or background***
90
1
5
0.5
0.5
1
90
0.5
0.5
*This table applies to land disposal methods, including reinjection and discharge to ponds.
The offsite surface water discharge is regulated under an NPDES permit issued by the .
Regional Board.' .
tEPA Method 502.2 with a detection limit of 0.01 ~gIL or less. If the daily maximum is
exceeded, an additional sample(s) must be collected and analyzed within the same month to
demonstrate that the monthly median has not been exceeded.
**Total VOCs will be the sum of all EPA Method 502.2 (detection limit of 0.01 ~gIL)
constituents and generally include all of the halogenated volatile compounds individually
listed in Table 8.
ttBenzene, toluene, xylene, and ethylbenzene.
***Background limit applies when background groundwater quality for referenced constituent
exceeds referenced numeric value.
Source: ESE, 1992.
46
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discharge standards for those contaminants (arsenic, selenium, and nitrate) not
considered to be attributable to past or current activities are also listed in Table 9.

These effluent discliarge standards were established in compliance with the State
Water Resources Control Board Resolution No. 68-16. SHARPE will employ the
best available technology (air stripping) in compliance with this Resolution for
removal" of the halogenated volatile organic constituents (VOCs J from
groundwater. SHARPE believes that the effluent dis~arge standards specified in
Table 9 can be achieved with proper plant design and operation.
1.2 GROUNDWATER TREATMENT
i .
With respect to Alternatives lA, lC, 2B, and 3D (all of which are treatment
alternatives), the 9-point evaluation criteria indicated only mipinta1 differences
betWeen the four treantlent alternatives in each of the criteria addressed.
Evaluation of Short- and Long-Term Effectiveness, Protection of Human Health
and Environment, State Acceptance, and" Community Acceptance indicated that
Alternatives lA, 1 C, 2B, and 3D were nearly identical. Notable differences in
Reduction of Toxicity, Mobility, and Volume (TMV); Implementability;
Compliance with ARARs; and Cost are highlighted in the description of
groundwater treatJ:nent alternatives presented in the following paragraphs.

1.2.1 Alternative lA
Alternative lA, air stripping, consists of the technologies to pump and treat
groundwater (North and South Balloon and Central Areas) and treat air
emissions from the air stripper (Central Area only). The time to achieve aquifer
cleanup goals has been estimated as 16 years. The air stripper will be designed
to reduce VOC concentrations to acceptable levels. Air stripping is a mass-
tranSfer process in which a liquid (for example, groundwater) containing volatile
compounds is brought into contact with air, and an exchange of gases takes
place between the air and the liquid. The major components include:

Extraction we1lfie1d and associated piping network;
Equalization tank to stabilize groundwater flow and VOC "
concentrations in the influent (Central Area. only);
Air stripping system consisting of two countercurrent packed towers to
remove VOC contamination; "
47
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Gas-phase carbon adsorber for tteattnent of offgas (Central Area only);
and
Groundwater discharge via surface water discharge, water reuse, and
evaporation/infiltration ponds with connector wells.

This alternative is fully compliant with ARARs. Because air stripping is already a
proven and effective technology in the North and South Balloon Areas at
SHARPE, no treatability testing will be required. Therefore, this technology
can be implemented sooner than Alternatives IC, 2B, and 3D. Unlike
Alternatives 1 C, 2B, and 3D, this alternative has an additional ARAR
requirement--compliance with standards set forth by the San Joaquin Air
Pollution Control District (SJCAPCD). This ARAR is relevant due to TCE
emissions from the air stripper. However, if suCh treattnent is found to be
necessary to comply with ARARs, SHARPE agrees to provide the appropriate
treatment measures.
The total present-worth cost for this alternative is estimated as $4,147,000 for
an estimated 16-year groundwater remediation project.
7.2.2 Alternative IC
Alternative 1 C, GAC tteattnent, involves pumping contaminated groundwater
through a bed of GAC which is capable of removing contaminants from
groundwater through adsorption. The time to achieve aquifer cleanup goals has
been estimated as 16 years. The major components of Alternative 1 C are the
same as for Alternative 1 withGAC treatment substituted for the air stripping
system.
This alternative is fully compliant with ARMs. Prior to implementation of this
alternative, a treatability study would be required. Therefore, the time to
implement this alternative would be greater than the time to implement
Alternative"lA. The total present-worth cost for this alternative is estimated as
$6,264,000 for an estimat~ 16-year groundwater remediation project.
7.2.3 Alternative 2B
Alternative 2B, ozonation with H101 and UV light, converts contaminants in the
groundwater to innocuous compounds (such as water, carbon dioxide, and
chloride ion) which remain in the water. The time to achieve aquifer cleanup
goals has been estimated as 16 years. The major components of Alternative 2B
48
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P/SHARPE/GWROD.24
01/11/93
are the same as for Alternative 1A with an ozonation unit with UV light and
secondary H202 treatment substituted for the air stripping system.
This alternative is fully compliant "with ARARs. Prior to implementation of this
alternative, a treatability study would be required. Therefore, the time to
implement this alternative would be greater than the time to ~plement .
Alternative 1A. Unlike Alternatives lA, 1 C, and 3D, this alternative would not
produce a residual which required offsite management. Therefore, waSte
management ARARs do not apply to this alternative. The total present-worth
cost for this alternative is estimated as $6,976,000 for an estimated 16-year
groundwater remediation project.
7.2.4 Alternative 3D
Alternative 3D, fixed-bed biological towers, uses microbial bacteria', which are
supported on media in a tower, to remove contaminants from the groundwater
biologically. The time to achieve the aquifer cleanup goals has been estimated as
16 years. Alternative 3D would alSo reduce VOC concentrations in the
groundwater to acceptable levels. The major components include:
, ;
Extraction wellfie1d and associated piping network;
Equalization tank to stabilize organics and groundwater flow in the
iz?t1uent;
Nutrient feed to enhance groWth of microorganisms;
Air source to provide oxygen to the. aerobic microorganisms;
Three fixed-bed biological towers to reduce organics in groundwater;
Effluent clarifier to provide solids/liquid separation prior to effluent
discharge; and .
Groundwater discharge via sunace water discharge, water reuse, and
evaporation ponds with connector wells.
This alternative is fully compliant with ARARs. Prior to implementation of this
alternative, a treatability study would be required. Therefore, the time to
implement this alternative would be greater than the time to implement
Alternative 1A. The total present-worth cost for. this alternative is estimated as
$9,655,000 for an estimated 16-year groundwater remediation project.
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7.2.5 Alternative 6A
. Alternative 6A, tenned the no-action alternative, involves monitoring only. The
NCP requires that the no-action alternative be considered at every Superfund site
for comparison to other alternatives. Use of this alternative would leave the site
in its current condition; however, groundwater monitoring would be conducted
so that contaminant migration pathways could be evaluated. Quarterly
monitoring would be ongoing using the existing network of wells onsite for
approximately 4 years until site-wide cleanup is implement~d.

This alternative does not provide community protection, reduce risk, reduce TMV
through treatment, comply with ARARs, or provide protection to human health 0
and the environment. The total present-worth cost for this alternative is
$1,228,000.
7.3 DISCHARGE OF TREATED GROUNDWATER
All of the remaining treatment alternatives, with the exception of the no-action
alternative, would use multiple discharge alternatives for the treated
groundwater.. Discharge would consist of pumping treated groundwater to:
Swface water,
Water users Oocal industry and agriculture), and
Evaporation/infiltration pond with connector/injection wells.
Currently, discharge of the treated groundwater from the interim treatment
systems at the North and South Balloon Areas is to surface water and through
reuse. The only discharge alternative capable of IrnUlaging the entire final
volume of treated groundwater (from the North and South Balloon and Centtal
Area treatment systems) is to surface water. Discharge through reuse and a
pond with connector wells are not capable of accepting the total final volume of
treated groundwater. However, ~use and recycling of the treated groundwater
are preferable because of the benefits to the water resource. Therefore,
discharge to surface water will be minimized. SHARPE is committed to the
productive reuse/recycling of the treated groundwater.
Because water extracted from the A-zone of the Central Area is expected to
contain higher concentrations of arsenic (as well as nittates), water extracted
from this zone, and treated, will be returned to the same zone.
50
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P/SHARPE/GWROD.26
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Treatment is not required for specific compounds (e:g., arsenic, selenium,
nitrates) which are naturally occurring and/or not a result of activities at
SHARPE to comply with specific discharge criteria.
8.0 SUMMARY OF COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES
Evaluation of nine criteria is required under the NCP and Sec. 121 of CERCLA
for use in evaJuation of remedial alternatives: The. nine criteria are as follows:
1. Overall protection of human health and the environment; .
2. Compliance with applicable and relevant and appropriate requirements;
3. Long-term effectiveness;
4. Reduction of toxicity, mobility, or volume through treatment; .
5. Short-term effectiveness;
6. Implementability; .
7. Cost;
8. State acceptance; and
9. Community acceptance.
A comparative analysis was conducted to evaluate the relative perfonnance of
each of the five alternatives for groundwater in relation to each of nine specific
evaluation criteria. The alternatives include:
1. Alternative 1A--Air Stripping,
2. Alternative 1 C--GAC Treatment,
3. Alternative 2B--Ozonation with UV Light and H202J
4. Alternative 3D--Fixed-bed Biological Treatment Towers, and
S. Alternative 6A-No Action.
The advantages and disadvantages of the five alternatives are compared in the
following paragraphs.
A complete detailed evaluation is presented in the groundwater FS (ESE, 1991a).
8.1 PROTECTION OF HUMAN HEALTIi AND TIiE ENVIRONMENT
Each treatment alternative provides full compliance with cleanup requirements, is
fully protective for the long-term Period, but does not ensure complete protection
in the short-tenn period. Alternative 1A differs from the other three treatment
alternatives in that offgases from the North and South Balloon Area Groundwater
Treatment Systems will be emitted. However, the risks associated with exposure
to off gases are not significant. The no-action alternative does not comply with
51
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P/SHARPEIGWROD.27
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cleanup requirements, does not provide protection in the short-term period, and
does not provide protection in the long-term period.
8.2 COMPUANCE Wl1H ARARs
Based on previous descriptions, the four groundwater treatment alternatives
comply equally with ARLs and EDSs. The no-action alternative does not meet
the cleanup requirement. However, treatability testing will be required to
evaluate the effectiveness of Alternatives 1 C, 2B, and 3D ARLs and EDSs and for
determining the characteristics of residues from the treatment processes. It is not
necessary to perform treatability testing with Alternative lA, air snipping,
because this alternative is currently achieving ARARs at the site.
8.3 LONG-TERM EFFECTIVENESS
Compared to the no-action alternative, each treatment alternative offers 'greater
long-term effectiveness and permanence by providing extraction and treatment of '
the contaminated groundwater. However, each treatment alternative provides
less operational reliability than the no-action alternative due to the large number
of technical components and greater operation and maintenance (O&M)
requirements. Based on this information, all four VOC treatment alternatives are
considered equivalent with respect to long-term effectiveness.
;
.
The following is a summary of the evaluation for long-term effectiveness for each
treatment alternative:
1.
Alt~ative lA--Air Snipping: Magnitude of residual risks due to
offgas treatment is minimal, no uncertainties or difficulties associated
with long-term O&M, minimal uncertainties associated with long-term
reliability. Spent carbon, generated from treatment of offgases, will be
transported offsite by a licensed hazardous waste transporter to an
approved carbon reactivation facility, where VOCs will be incinerated
and the carbon either reused or disposed of in a suitable waste
disposal facility.
2. Alternative 1 C--GAC Treatment: Magnjtude of residual risks due to
sperit carbon is minimal, no uncertainties or difficulties associated with
long-term O&M, minimal uncertainties associated with long-term
reliability. Spent carbon will be transponed by a licensed hazardous
waste transporter to an approved carbon reactivation facility, where
VOCs will be incinerated and the carbon either reused or disposed of in
a suitable waste disposal facility.
52
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3. Alternative 2B--Ozonation with UV Light and H202: No risk associated
with treatment residuals exists for this alternative, minimal
uncertainties or difficulties associated with long-term O&M, no
uncertainties associated with long-tenn reliability.
4. Alternative 3D--Fixed-bed Biological Towers: No risk associated with
treatment residuals, minimal uncertaintieS or difficulties associated
with long-tenn O&M, minimal uncertainties associated with long-tenn
reliability. Waste sludge will be transported by a licensed hazardous
waste transporter to an approved waste facility for disposal.
... 8.4 REDUCTION OF TMV
Comparison of the five alternatives indicates that the no-action alternative
provides the least reduction in TMV through treattnent. All of the treattnent
alternatives provide equal reduction of TMV in the groundwater. The GAC and
fixed-bed biological tower systems, .however, produce substantial quantities of
treatment residuals that must be disposed of at an offsite facility.
8.5 SHORT-TERM EFFECTIVENESS
Compared to the no-action alternative, the four treattnent alternatives provide a
greater measure of shon-term effectiveness. Although Alternatiye 6A (no action)
provides greater protection for workers during implementation, it does not
incorporate recovery and treatment for contaminated groundwater. Comparisons
made among the four treatment alternatives provided no significant difference in
short-term effectiveness. Because extraction well installation required for each of
the treatment alternatives is identical, no difference exists in the protection
offered for workers during construction of each alternative. Although the
treatment alternatives would not ensure protection of the community during the
short-tenn period, they would perform equally well as migration control
measures by reducing groundwater contaminant levels. Alternative lA was
different from the remaining three treattnent alternatives in that treatment
systems in the North and South Balloon Areas will emit an offgas. However, the
health risks associated with a lifetime exposure to this. source were not
considered significant. Based on this infonnation, all four VOC treatment
alternatives are considered equivalent with respect to short-term effectiveness.
8.6 IMPLEMENTABIL1TY
All five treatment alternatives for groundwater are judged to be equally
implemeritable based on technical and administrative feasibility. Furthermore, all
53
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required materials and services to implement the five alternatives are readily
available. However, Alternatives 2B and 3D may require pretreatment for
metals, and Alternative 3D will require the longest startup time.
With regard to treated groundwater discharge options, the evaporation pond
with connector/injector wells is the most implement~ble due to administrative
acceptance. The water reuse option could be difficult to implement due to no
clearly identified large quantity user in the area with an interest in entering an
agreement with SHARPE to accept water. The surface water discharge will be
difficult to implement due to limitations on discharge concentrations of specific
parameters.
Because remediation of groundwater at SHARPE is pan of a CERCLA action,
SHARPE will not be required to apply for pennits for the onsite cOnlponents of
the remediation. However, off site components, such as discharge to the SSJIDC
and offsite extraction wells, will have to comply with appropriate permit
application requirements. Even though the onsite components of the remedial
action do not .have to follow appropriate permit application processes, they do
have to comply with the substantive requirements of appropriate pennits.
,
, ...
8.7 COSTS
Capital, O&M, and present-worth costs for Alternatives IA, IC, 2B, 3D, and 6A
are presented in Table IO.
The present-worth cost is the least expensive for the no-action alternative. The
least expensive treatment alternative is Alternative IA; Alternatives 1 C and 28
have comparable capital and O&M costs. The capital and O&M costs for
Alternative 3D are significantly higher than the estimated costs for the other
treatment alternatives. Testing may be required to define the disposal
characteristics of the residues from Alternative 3D. This information is necessary
to evaluate. alternatives for management of treatment residue.
8.8 STATE ACCEPTANCE
The selected remedy for groundwater remediation is Alternative IA, which
includes groundwater extraction, tteatrnent by air stripping, and discharge to:
Surface water,
Water user Oocal industry and agriculture), and
Evaporation/infiltration pond with connector/injection wells.
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Table 10. Capital, O&M, and Present-Worth Costs for the Groundwater Remedial
Alternatives (Includes Costs for Groundwater Extraction, VOC
Treatment, and Disposal)
Total Present-
Capital Costs O&M Costs Worth Costs
Alternative ($1,000) ($1,000) ($1,000)
1A. Physical Treatment* -- 2,007 2,140 4,147
Well Extraction, Air
Snipping, Disposal
1C. Physical Treatment* -- 3,209 3,055 6,264
Well Extraction, GAC
Treatment, Disposal
2B. Chemical Treatment-- 3,982 2,994 6,976
Well Extraction,
Ozonation with H202
and UV Light, Disposal
3D. Biological Treatment- 5,080 4,575 9,655
Well Extraction,
Fixed-Bed Biological
Towers, Disposal
6A. No Action- 0 1,228 1,228
Monitoring Only
*Includes costs for carbon regeneration.
Source: ESE..
55
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The state has accepted the FS and endorses implementation of Alternative lA to
remediate groundwater.
8.9 COMMUNITY ACCEPTANCE
Based on the public review and comment on the Proposed Plan, the community
has no significant concerns regarding selection andl or implementation of any of
the alternatives investigated by DDRW to remediate contaminated groundwater.
9.0 THE SELECTED REMEDY
Based on consideration of the requirements of CERCLA, the detailed analysis of
alternatives, and public comments, DDRW, SHARPE, EPA, and the State of
California have detennined that Alternative 1A, Groundwater Extraction and Air
Stripping, is the most appropriate remedy for SHARPE. This alternative consists
of groundwater extraction and' air stripping using packed towers to achieve the
ARLs and EDSs defined in Tables 8 and 9. Alternative lA includes the following
components for each of the three treatment areas (i.e., North Balloon, South
Balloon, and Central Areas):
, "
1. Extraction wellfield and associated piping network to remove
groundwater from the contaminated aquifer zones;
2. Equalization tank designed to stabilize groundwater flow and VOC
concentrations in the influent (in Central Area only);
3. Air stripping systems consisting of countercurrent packed towers
designed to remove VOC contamination from groundwater (includes
treannent of air stripper offgases with carbon adsorption in the Central
Are13); and
4. Groundwater discharge via surface water discharge, water
reuse-, and evaporation ponds with connector/injection wells.
The goal of this remedial action is to restore groundwater to its beneficial reuse.
Based on information obtained during the Rl (ESE, 1990) and on a careful
analysis of all remedial alternatives, EPA and the State of California believe that
the selected remedy will achieve this goal. However, studies suggest that
groundwater extraction and treatment are not, in all cases, completely successful
in reducing contaminants to health-based levels in the aquifer. EPA and the
State of California recognize that operation of the selected extraction and
treatment system may indicate the technical impracticality of reaching health-
56
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.P/SHARPEIGWROD.31
01/11/93
based groundwater quality standards using this approach. If it becomes
apparent, during implementation or operation of the system, that contanUn~nt
levels have ceased to decline and are remaining conStant at levels higher than the
levels required by this ROD, the goal and remedy may be re-evaluated.
The selected remedy will include groundwater extraction for a period of
16 years. During thiS period, system perfonnance will be carefully and regularly
monitored and adjusted as warranted by the perfomlance data collected during
operation. Modifications will include the following:
1. Discontinuing operation of extraction wells in areas where cleanup
goals have been attained,
2. Alternating pumping at wells to eliminate stagnation points, and

3. Pulse pumping to allow aquifer equilibration and encourage adsorbed
contaminants to partition into groundwater.
, ~
. .
The following sections describe the major components of the selected alternative.
Engineering variables presented in the following sections, however, are subject to
change based on the remedial design engineering process to be implemented
following signature of the ROD by EP A and the State of California.
Since initiation of regulatory review of this ROD, DDRW has proceeded with the
design of the groundwater extraction and injection system. Remedial design
infonnation presented in the report entitled Remedial Well-Field Design Using
Three-Dimensional Groundwater Flow and Transport Modeling supersedes
wonnation presented. in this ROD. Specific areas impacted are details of the
extraction and injection networks Oocations of wells and flow rates) and
estimated time needed to achieve aquifer cleanup levels. The number of
treatment plants needed in the Central Area may also change. Infonnation
presented in this ROD is adequate for evaluating potential remedies and for
selecting a remedy but will not be used as a basis for remedial design. Remedial
designs will be based on the three-dimensional modeling work and on future
design efforts.

9.1 GROUNDWATER EXTRAcnON (RECOVERY)
9.1.1 Groundwater RecoveIy in North and South Balloon Areas
Groundwater recovery systems implemented as interim response actions are
currently in operation in the North and South Balloon Areas. Additional
57
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01/07/93
upgrades to the extta!=tion systems have been implemented to captUre the
groundwater in excess of ARLs. If necessary, further upgrades to these.
groundwater remediation systems will be made in the future. At a minimum,
upgrades will be evaluated during the remedial design process and subsequent
5-year reviews. Figs. 12 and 13 identify the existing locations of the recovery
wells for the Nonh and South Balloon recovery systems, respectively.
9.1.2 Groundwater Extraction in the Central Area
Proposed locations for the 15 extraction wells in the Central Area (5 in A-zone,
6 in B-zone, and 4 in C-zone) are shown in Fig. 14. The selection of these
locations was based on (1) proximity to confirmed groundwater contamination
source areas; (2) proximity to a contaminated monitor well, thereby increasing
the likelihood of intercepting contaminated groundwater; and (3) sufficient
spacing between wells to ensure adequate coverage of the contaminated areas.
Based on the results of field tests, the total number of wells and well locations
may vary. The exact design of groundwater extraction wells will be based on
future field work and modeling efforts.
The contaminant transport Random Walk model was used to detennine
approximate flow rates, well locations (plume and zone), and treatment times for
the plumes identified in the Central AIea. Table 11 presents proposed locations,
depths, and anticipated flow rates (i.e., pumping rates) for each extraction well.
Aquifer pump tests will be conducted prior to implementation of the
groundwater extraction system in the Central AIea.
The estimated flow rate to be delivered to the Central Area treatment system is
approximately 570 gallons per minute (gpm). This flow rate was derived from
an estimation of the flow rates required for each extraction well necessary to
recover the groundwater plumes. Table 12 presents the estimated total influent
concentrations versus recovery time, as well as the estimated influent flow rates
anticipated for treatment based on Random Walk output. The approximate time
for TCE recovery is estimated as 16 years. Therefore, based on groundwater
modeling in the Central Area, it was assumed that the time for groundwater
remediation in the North and South Balloon Areas also would be approximately
16 years. .
Table 13 summarizes the initial operating conditions of each of the three
treatment systems.
58
-------
'N
--
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PLANT
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o 275 550
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Rgure 12 REMEDIAL INVESTIGA TIDN/f'EASIBnlTY STUDY
Shorpe SIta La~ ~
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.... ... ''''IIIUD 1181. 1M. 841. PNvIng ~ I4ary\8IIIi
59
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Ffgur'8 13 REMEDIAL INVESTIGA TIDNIFEASIB1UTY STUDY
Shorpe SIt80 Lo~ ~
SOUTH BAUDON EXTRACTION WElJ.S SYSTDf
us. IrPr:I T~ QNII ....---. MD.'t8rtIU Ag8nc:y
--. -. ,.""" ,..,.. ~r...811 PI'ovIIg ~ MD.ry\AIId
60
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C-DNI (It)
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KEY

A-Z~ IJA)- PROPOSED EXTRACTION ww.
a - PROPOSED TRUlNEHT SYSTEM
-- - - - PROPOS£D PIPING
o DO lIIIO
SCALE fEET
~
~~
-
FIgure 1. REMEDIAL INVESTlGATlDN/FEASIBILITY STUDY
- SIte. LothroD. CR'"''''''
PROPOSED EXTRACTION WELLS AND CENTRAL AREA TREATMENT SYSTEN LOCATION u.s. -y ToxIC cand tIIo.~. tIIoterICI'. ....,y
IIUIC[o ESE. /\IIe,.- ,,"omg c;..0un4 """ylo'"''
-
61
, '"'' . .' .,... ad
-
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P/SHARPEIGWROD.V.8
11/11/92
Table 11. Proposed Extraction Well Locations and Descriptions for Central Area
,
Extraction
Well" Plume Zone Flow Rate
Number Number (Depth) (gpm)
1A 3 A 20
2A 4 A 30
3A 4 A 30
4A 4 A 30
5A 6 A 20
1B 3 B '20
2B 4 B 30
3B 4 B 30
4B 4 B 30
5B 6 B 30
6B 6 B 30
IC 4 C 70
2C 4 C 70
3C 4 C 70
4C 6 C 60
Source: ESE.
62
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11/11/92
Table 12. Recovery System Anticipated Influent Co~centrations and Flow Versus
Time
TCE Flow
Days (~g/L) (gpm)
1 2,635 570
11 2,473 570
31 997 570
61 333 570
161 243 570
361 172 570
661 111 490 ' .
1,061 . 50 430
1,561 31 220
2,561 17 200
4,561 9 90
6,561 3 90
Note: Linear extrapolation of last two data points indicates that 5 ~g/L will be
achieved at 5,884 days. Therefore, assume treatment period of 16 years.
Source: ESE.
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Table 13. Groundwater Treatment Variables for NOM Balloon, South Balloon,
and Central Area Treatment Systems
North South . Central
Balloon Balloon Area
Flow Rate (gpm) 400 300 570
Influent TCE Concentration 400 100 2,600
(#Lg/L)
Other VOCs (#Lg/L) <5* <5* <5*
*Per compound.
Source: ESE.
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9.2 GROUNDWATER TREATMENT
Fig. 15 shows. the proposed layout for Alternative 1A for the Central Area. The
configuration of the systems in the North and South Balloon Areas is similar with
the exception that gas-phase carbon. adsorption is not used. The following
description addresses the Central Area treatment system. .
Air snipping is a mass-transfer process by which a liquid containing volatile
compounds is brought into contact with air and an exchange of gases takes place
between the air and water. Generally, the most efficient type of air stripping is
accomplished in packed towers equipped with an air blower. Each stripping.
. tower consists of a cylindrical structural shell or tower filled with inert packing
material that increases the surface area for gas-liquid contact. Packed tower air
snippers are generally operated in. a countercurrent mode in which the air flow
enters at the base of the tower, and water enters at the top of the tower, flowing
down through the packing material, countercurrent to the air flow.
- .
The assumed initial flow rate to be delivered to the Central Area treatment
system is 570 gpm. However, as noted previously, the groundwater recovery
rate will decrease over time. Groundwater pumped from the extraction wells
will be piped to the treatment unit via the belowgrade piping. From the
extraction weUfield, groundwater will be pumped to one of two equalization
tanks designed to stabilize influent flows and VOC concentrations. The specific
equalization tank to which the extracted water is pumped will depend on the
aquifer zone from which the water was extracted. Separating water at the
extraction field will allow the water from selected aquifer zones to be isolated
Uu'ough the treatment process so that it can be preferentially injected back into
the zone from which it was withdrawn (see Sec. 9.3). The piping system will
include instrUmentation. to provide water-level control in the wells and the
equalization tank, as well as shutoff controls in the event of pump failures.
From the equalization tanks, water will be pumped to the top of an air stripper
by a horizontal, base-mounted centrifugal pump. Four air strippers are expected
to be required to treat groundwater in the Central Area. VOCS removed from
water during treatment will be vented through the top of the column. The VOC
offgases from the Central Area system will require an emission control system to
comply with the SJCAPCD, County Rule 209.1. It is expected that the systems in
the North and South Balloon Areas will be able to continue to operate without
emission control systems. The emission control system proposed for the Central
Area consists of a vapor-phase carbon treatment unit. Preheating of the
vapor-phase emissions prior to carbon treatment will be necessary to reduce the
relative humidity of the offgases, thereby increasing carbon recovery efficiency.
65
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WMDOWIUOIMKM
KEY
PUMP

OF M1AS COLLECTION PIPE
WATER PIPING
CHECKVALVE

BLOWER
OFF-OA8TO
ATMOSPHERE
CARBON
ADSORBER TO EFFLUENT
» DISPOSAL
EXTRACTION
WELLFIELD
TO EFFLUENT
DISPOSAL
Figure 15
SCHEMATIC OF PROPOSED AIR STRIPPING
TREATMENT SYSTEM
BOUHCI: IM.
REMEDIAL INVESTIGATION/
FEASIBILITY STUDY
Sharp* SHe, Lalhrop, California
U.S. Army
Toxic and Hazardous Materials Agency
Aberdeen Proving Ground, Maryland
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P/SHARPEIGWROD.34
01/07/93
Offgases from each air stripper will be passed through a vapor-phase carbon
adsorption unit. One vapor-phase carbon adsorber, with a capacity of
10,000 pounds of activated carbon, will be used to remove volatiles from the
offgases prior to discharge of air to the atmosphere. Carbon change-out will be
perfonned by a vendor who will supply all materials and equipment for the
change-out. Considering the lower carbon usage rates associated with this .
application, offsite reactivation of carbon would be more economical than onsite
regeneration.
Construction of the Central Area treatment system will require mobilization and
site preparation including installation of a power pole for 3-phase, 240-volt
electricity and clearing; excavation; and construction of a concrete pad
approximately 40 ft by 40 ft for the four towers and the vapor-phase carbon
adsorber, blower, and equalization tanks. The proposed location of the
treatment system, as shown in Fig. 14, is central with respect to the proposed
extraction wellfield and clear of the runway.

Projected annual O&M costs of Alternative 1A for the assumed 16-year treatment
period include periodic replacement of pumps and packing material, periodic acid
wash of the packing material, maintenance of the treatment system equipment,
energy requirements for the extraction well pumps and treatment system pumps
and blower, labor and expenses for operating the system, vapor-phase carbon
replacement, and treatment system monitoring costS.
Weekly analysis of the tteatment system will be perfonned and will include one
influent sample collected betWeen the equalization tank and the air strippers, and
one sample collected at the effluent from each air stripper. Monthly sampling of
groundwater recovery wells may be required. '.However, during system startup,
the frequency of sample collection may be greater. Specific monitoring
requirements will be developed during the remedial design phase and approved
by EP A and the State of California. All water samples will be analyzed by the
USAGE-certified methods for VOCs to monitor the perfonnance of the treatment
system and to ensure that the treatment objective is achieved. .
9.3 GROUNDWATER DISCHARGE
Three discharge alternatives are anticipated for groundwater treated at SHARPE:
1. Water reuse,
2. Evaporation ponds with connector/injection wells, and
3. Surface water discharge.
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Alternatives 1 and 3 are currently being used for discharge of treated
groundwater from the North and South Balloon Area Groundwater Treatment
Systems. It is anti~pated that water from these treatment systems will continue
to be discharged via these options. Based on the limited flow which can be
discharged to SSJIDC, the additional flow generated in the Central Area will not
likely be transmined via surface water discharge to the canal.
Alternative 2 consists of excavating a retention pond and using injection wells
around the perimeter of the pond. To hold approximately 6 weeks of flow from
the treatment system, the pond must be approximately 1,foo ft in length, 700 ft
in width, and 6 ft in depth. Water stored in the pond, to a large extent, can be
used to supplement the water which would nonnally be obtained from off site
agricultural wells, which may be taken out of service to prevent pumpage of
contaminated groundwater. To a lesser extent, the water can also be used
onpost for irrigation and vehicle cleaning. The pond will be divide(i into tWo
cells. The specific cell into which treated water is discharged will depend on the ;
zone from which the water was initially extracted. Separation of water based on' i.
the zone from which it was extracted will pennit water with higher background
levels of constituents (e.g., arsenic, nitrates) to be discharged into the same zone
from which it was withdrawn and prevent deterioration of a lower aquifer zone
which has lower background levels of specific constituents.
An analysis was performed to determine if the connector wells (i.e., injection
well screened in multiple zones) in the pond would be adequate to deliver
treated groundwater back to the aquifer. Sixteen wells, each screened in the A-,
B-, or C-zones, should be adequate for groundwater discharge. All flow through
the wells will be via gravity. The wells will be placed around the perimeter of
the pond.
Treated groundwater volume will also be reduced via evaporation, but the
amount will vary from season to season.
System cons~ction will require" pond excavation and connector/injection well
installation. The proposed pond location was selected because the space is
available, and it is near the proposed location of the Central Area treatment
system. Projected annual O&M costs for this alternative are low. Only periodic
removal of growth, such as algae blooms, in the pond will be necessaIY. Water
flowing into the wells will be passed through a screen to prevent suspended
maner from entering; therefore, periodic maintenance of the screen will be
required.
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01/07/93
The connector/injection well system will be designed as a multifunctional system.
The wells are located on the outside of the pond perimeter rather than inside to
facilitate monitoring and well maintenance. Water from the pond could be
collected by a common intake structure and conveyed to the wells by a header
piping system. To control flows to individual wells a valve should be located at
each wellhe~d. This system will allow for the retrofitting of a pumping unit if
the groundwater levels rise enough to significantly decrease the injection
capacity of the system. .
This system could receive flows from either the treatment units or the pond
depending on the availability of water at either location. In addition, the flow
from the treatment unit could be allowed to flow directly into the pond for later
injection into the wells.
The proposed location of the connector/injection wells is partially upgradient of
the North Balloon extraction system. . At this location, the effects of the injection '.
will be only to increase the groundwater gradient. The direction of the
groundwater flow should not be significantly altered. Treated water which is.
injected into the wells should flow to one of the tWo eXtraction systems and be
withdrawn from the aquifer system. This scenario creates a closed system wbich
should promote the highest level of remediation.
10.0 STAnITORY DETERMINATIONS
The selected remedy satisfies the statutory requirement of Sec. 121 of CERCLA,
as amended by SARA, in that the following four mandates are attained:

1. The selected remedy is protective of human health and the
environment, will decrease site risks, and will not create short-term
risks nor have cross-media consequences.
2. The selected remedy complies with federal and more stringent state
requirements that are applicable or relevant and appropriate to the
remedial action such as chemical-specific ARARs.
3. The selected remedy is cost effective in its fulfillment of the nine
CERCLA evaluation criteria through remediation of the contaminated
groundwater in a reasonable period of time.

4. The selected remedy uses pennanent solutions and alternative
treatment technologies or resource recovery technologies) to the
maximum extent practicable) while concurrently satisfying the
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01/07/93
statutory preference for remedies that employ treattnents which
pennanently reduce toxicity, mobility, and/or volume through
treatment.
The following sections describe how the selected remedy satiSfies each of the
statutory reqUirements and the preference for treatment.
10.1 BE PROTECTIVE OF HUMAN HEALTH AND ENVIRONMENT .
Risks to human health and the environment from groundwater contamination
would be significantly reduced by implementation of the selected remedy.
Table 14 presents residual risks of treated groundwater. VOCs in groundwater
would be reduced to levels below the ARLs by air stripping with packed towers
prior to discharge. As described for Alternative 1A, the treatment system
proposed would permanently reduce the levels of VOCs in groundwater (provided
the soUrce of contamination is removed prior to implementation of this
alternative) to levels below the ARLs. This remedial action provides long-term
effectiveness because it would redu'ce the existing health risks to offpost users
caused by VOCs in groundwater migrating offsite. Risks associated with
exposure to 'offgases from the North and South Balloon Area Groundwater
Treatment Systems are not estimated to be significant.
, ~
10.2 COMPLY wrm ARARs
The selected remedy, when complete, will have reduced concentrations of COCs
in the groundwater to cleanup standards, thereby satisfying the chemical-specific
ARARs (federal or state MCLs, whichever are the more stringent for the site). In
addition, during remediation, this remedy will meet action-specific ARARs for
discharging the treated water into the aquifer by injection, reuse, or surface
water discharge. For any waste carbon that is generated during .air emission
control by activated carbon, the applicable Resource Conservation and Recovery
Act (ReM) and more stringent California Hazardous Waste Control Law
requirements will be met. No ARAR waivers will be necessary.
10.2.1 Chemical-S
. c: ARARs
Alternative 1A, air stripping, has been designed for removal of VOCs to
concentrations below the cleanup levels. The selected remedy, when complete,
will have reduced concentrations of COCs in the groundwater to ARL, thereby
satisfying the chemical-specific ARARs (federal or state MCLs, whichever is more
stringent for the site). .
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11/16/92
Table 14. Residual Cancer Risks After Groundwater Treatment to ARLs
Water Source
Plume
Zone Residual Risk of Treated Water'"
A 4.75E-6
B 8.16E-6
C 1.03E-5
D 3.08E-6
A 1.5E-05
B 2.38E-05
A* 4.34E-6
B 2.37£-5
C 1.02£-5
A 2.52£-6
C 2.92£-6
C 2.27£-5
A 2.57£-6
B 2.27£-5
C 2.41E-5
1
.
3
4
6
7
*Total cancer risk when TCE is treated to 5 ~g/L and all other carcinogens are reduced to
0.5 ~g/L.
Source: ESE.
71
. . .
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P/SHARPE./GWROD.38
01/11/93
10.2.2 Action-Specific ARARs
With proper pl~g and implementati~n, the remedial action which implements
this alternative would comply with the following federal action-specific ARARs:

1. Standards for Owners and Operators of Hazardous Waste Treatment,
. Storage, and Disposal Facilities (40 CPR 264.190- 264.192).
2. Guidelines Establishing Test Procedures for the Analysis of Pollutants
(40 CPR 136.1). .
3. For any waste carbon that is generated during air emission control by
activated carbon, the applicable RCRA and more stringent California
Hazardous Waste Control Law will be met. No ARAR waivers will be
necessary.
4. It is anticipated that a portion of the treated groundwater would be
discharged using injection wells (i.e., connector wells). The
requirements for Class V injection wells (40 CPR 144.12) would be the
most appropriate for discharge of treated groundwater. Water
extracted from the same formation that it was withdrawn will meet
MCLs (with the exception of arsenic, selenium, and nitrate--this
contamination is not attributable to activities at SHARPE).
, .
S. Iriventory infonnation reporting for injection of groundwater will be
complied with (40 CPR 144.26).
6. The DTSC has approved a negative declaration and the California
Environmental Quality Act (CEQA) requirements have been satisfied.
7. Treated groundwater will not be used as a potable source of water;
therefore, requirements set forth by ODW will be satisfied.
8. SHARPE has recognized that, with few specific exceptions, all surface
waters and groundwaters of the state are to be considered existing or
potential sources of drinking water. The Basin Plan, Porter-Cologne
Water Quality Act, and Resolution 68-16 all protect the beneficial uses
of groundwater. All of these standards will be complied with,
including standards with respect to VOC contamination. Because
arsenic, selenium, and nitrate are present at background levels in
groundwater, it is not necessary to consider remediation of these
compounds. To the extent that all other constituents in the
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P/SHARPEIGWROD.39
01/11/93
groundwater are also representative of background water quality,
discharge of treated groundwater to groundwater or the same aquifer
from which it was withdrawn will not take away from the beneficial
uses of the water or degrade the quality of water of the receiving
body.
9. Requirements of the Lathrop County Water Disnict/City of Lathrop
will be achieved because water discharged by injection will be into the
same area from which the groundwater was recovered.
10. The Central Area Treatment System will employ a best available
control technology (BAcr) (i.e., carbon adsorption) for offgas
treatment and will emit less than 2 tons ofVOCs per year. The North
and South Balloon Area Groundwater Treatment Systems have been
pennitted without BACT for offgas emissions but emit leSs than 2 tons
per year of VOCs. As such, the requirements of County Rule 209.1 for, .
SJCAPCD can be achieve4 with no difficulty.
10.2.3 Location-Specific ARARs
A qualified scientist has investigated the site and determined that none of the
following resource areas exist onsite: wetlands, riparian areas, federally listed
endangered species habitats, and other resource areas that would invoke
location:,sp~dfic ARARs. The state-listed burrowing owl does inhabit the site,
but investigations to date have not identified the potential for significant impact
to this species. These same resources would not be disturbed by off site
construction activities that would take place for the groundwater discharge
option. No location-specific ARARs were id~tified which would exclude this
alternative from consideration.
10.3 BE COST EFFECTIVE
The selected remedy, as compared to the alternatives evaluated, achieved an
equal or bener level of treatment at the least cost (see Table 10).
10.4 um.IZATION OF PERMANENT SOLunONS AND ALTERNA11VE
TREATMENT (OR RESOURCE RECOVERY) TECHNOLOGIES TO 1HE
MAXIMUM EXTENT PRAC11CABLE
The selected remedy provides the best balance of tradeoff's among the
alternatives evaluated with respect to the evaluation criteria. A comparison of
the alternatives relative to one another is presented in Sec. 8.0. Whencompared
73
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P/SHARPEIGWROD.40
01/11/93
to Alternatives IC, 2B, and 3D, on the basis of short-tenn effectiveness, long-
tenn effectiveness, reduction of TMV, implementapility, compliance with cleanup
guidelines, and protection of human health and the environment, Alternative lA
was evaluated to be an equivalent or better alternative for groundwater
remediation. On the basis of cost, Alternative lA was estimated to be the most
cost-efficient means of achieving the remedial objectives for the site groundwater
contamination. Alternative lA is the only alternative which does not require
treatability testing prior to implementation. All four treatment alternatives
comply with the threshold criteria of being protective of human health and the
environment and ARAR compliant. .
Based on the previous information, and because existing systems similar to
Alternative IA are currently achieving the cleanup levels at SHARPE, the
preferred remedial action recommended for the groundwater is Alternative lA.
This alternative provides protection of human health and the environment by
lowering the contaminant concentr;itions in the groundwater, which should also
be reflected in a progressive decline in the groundwater concentrations off site.
TMV of the groundwater contaminantS will be permanently and significantly
reduced as a result of the implementation of this alternative. Also,
implementation of this alternative should be well received by governmental
agencies and the c.ommunity because the sources of potential risk, including .
offgases, will be controlled or pose no significant threat to human health and the
environment. This alternative can achieve and comply with chemical- and
action-specific ARARs. No location-specific ARARs were identified which would
prevent implementation of this alternative. The system will be operated and
monitored to maintain compliance.
.
,
, =..
The selected remedy for groundwater remediation is Alternative IA, which
includes groundwater extraction, treatment by air stripping, and discharge to:
--Surface water,
-Water user Ooca1 indusny and agriculture), and
-Evaporation/infiltration pond with connector/injection wells.
The state has accepted the FS and endorses implementation of Alternative IA to
remediate groundwater.
Based on the public review and comment on the Proposed Plan, the community
has no significant concerns regarding the selection and/or implementation of any
of the alternatives investigated by DDRW to remediate groundwater.
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10.S PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The selected remedy satisfies the statutory preference for treatment as a principal
element because it involves extraction and treatment .of contaminated
groundwater. This treatment will permanently reduce the TMV of the COCs.
75
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ARAR
ARL
BACf
BNA
CEQA
CERCLA
CFR
COC
CPF
CRL
CSF
CVRWQCB
DDRW
DOD
DTSC
EDS
EPA
ESE
ft
ft-msl
FS
GAC
gpm
HI
H202
LIST OF ACRONYMS AND ABBREVIATIONS
P/SHARPF.lGWRODLOA.l
11/16/92
applicable or relevant and appropriate requirement
aquifer remediation level
best available control technology
base-neutral and acid extractable
California Environmental Quality Act
Comprehensive Environmental Response, Compensation, and
Liability Act
Code of Fed~ RegulationS
chemical of potential concern
cancer potency fact OJ'
certified reporting limit
. cancer slope factor
Central Valley Regional Water Quality Control Board
Defense Distribution Region West
U.S. Department of Defense
Department of Toxic Substances Control
effluent discharge standard
U.S. Environmental Protection Agency
Environmental Science & Engineering, Inc.
feet
feet above mean sea level
feasibility study.
granular activated carbon
gallons per minute
hazard index
hydrogen peroxide
76
, .
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HQ
IRIS
kg
l./day
LOEL
MCL
mg/kg-day
MLE
.NCP
O&M
OSWER
OU
PCE
ppb
RAGS
RCRA
RID
RI
RIIFS
RME
ROD
SARA
SHARPE
SJCAPCD
SSJIDC
SWDR
TBC
TCE
P/SHARPEIGWRODLOA2
11/16/92
hazard quotient
Integrated Risk Information System
kilogram
liters per day
lowest-observed-effect level
maximum contaminant level
milligrams per kilogram per day
most likely exposure
Nation Oil and Hazardous Substances Pollution Contingency Act
operation and maintenance
Office of Solid Waste and Emergency Response
operable unit
tetrach1oroethene
part per billion
Risk Assessment Guidance for Superfund
Resource ConseIVation and Recovery Act
reference dose
remedial investigation
remedial investigation/feasibility study
representative maximum exposure
Record of Decision
Superfund Amendments and Reauthorization Act of 1986
Sharpe Site
San Joaquin Air Pollution Control District
South San Joaquin Irrigation District Canal
Substantive Waste Discharge Requirements
to be considered
trich1oroethene
77
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IllTCE
TMV

~g/L
USACE
USATHAMA
. USGS
UV
VOC
WDC
P/SHARPE/GWRODLOA.3
11/16/92
1,1,1-tri~o~ethene
toxicity, mobility, and volume
micrograms per liter
U.S. Army Corps of Engineers
U.S. Army Toxic and Hazardous Materials Agency
U.S. Geological Survey
ultraviolet
. volatile organic compound
Western Distribution Center
, ,
78
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P/SHARPElRESPSUM.1
11/16/92
Defense Distn"butiOD Region West-Sharpe Site
Lathrop, Califomia
Responsiveness SnTnTnmy
1.0 OVERVIEW
At the time of the public comment period, Defense Distribution Region West
(DDRW) recommended a preferred alternative in the Proposed Plan for
remediation of groundwater at SHARPE in Lathrop, CA. DDRWs recommended
alternative addressed the groundwater contamination problems at the site. The
preferred alternative in the Proposed Plan for groundwater involved extraction of
contaminated groundwater, treatment using air stripping, and disposal to the
following:
I .,
1. Surface water,
2. Water users (i.e., local industry and agriculture), and
3. Evaporation/infiltration pond with connector/injection wells.
, .
Based on comments received during the public comment period, DDRW
concluded that residents near SHARPE ~ve no significant concerns regarding the
selection and/or implementation of any of the alternatives investigated by DDRW
to remediate contaminated groundwater.
2.0 BACKGROuND ON COMMUNITY INVOLVEMENT
Community interest in the SHARPE site dates to 1990 when SHARPE conducted
the first technical review committee (TRC) meeting, at which representatives of
the community were present. The TRC meenng was part of the Public
Involvement Response Plan (PIRP), which was completed in June 1989. The
TRC Charter was finalized in June 1990,. the same month as the first TRC
meeting. The last TRC meeting was held in December 1990. There bas been no
significant interest expressed by the community regarding the activities
conducted at SHARPE.
3.0 SUMMARY OF PUBUC COMMENTS AND AGENCY RESPONSES
Comments raised during the SHARPE public comment period for groUndwater
remediation are summarized below. The comment period was from February 6
to March 9, 1992.
1
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P /SHARPEJRESPSUM.2
11/11/92
1. Mrs. Eleanor Ramos, of French Camp, CA, called SHARPE to express
concern about the potential for her groundwater to be contaminated as
a result of activities conducted by SHARPE.
DDRW ResDonse: The commentor was notified by the SHARPE
Environmental Protection Specialist that contamination was not moving in
her immediate direction.
2. Ms. Karen Duke, of Lathrop, CA, questioned the need to extract
groundwater and why affected residents could not use bottled water.
She also questioned the approach of using air stripping as a treatm~t
alternative when contaminants were transferred from the water to the
air. In addition, she asked what the difference was betWeen
contaminants ingested with water or inhaled by brea~g.

DDRW ReSJ'onse: The EPA requires that the contaminated groundwater be
remediated to levels which ar.e protective of human health and environment
and that are compliant with applicable or relevant and appropriate
requirements (ARARs). The remediation of groundwater to reduce levels of
volatile organic compounds (VOCs) in the groundwater is necessary to
lower the site risks associated with ingestion of groundwater.
;
, ~
Air modeling was performed to assess risks associated with TCE emissions
and concluded that no significant risks were associated with the treatment
systems. The syStem to be installed in the Central Area will have an offgas
treatment system to remove TCE from air emissions prior to releasing them
to the atmosphere. Additionally, previous studies conducted at the site
were unable to detect TCE in air downwind of the air strippers.
3. During the public meeting, Mr. John Bingham, City Manager, City of
Lathrop, CA, expressed concerns regarding the disposition of treated
groundwater. He asked if the u.s. Government could cooperate with
the City of Lathrop, which will be in critical need of water within the
next few years. He also asked if the water could be used for irrigation.
DDRW Re5J'onse: In the meeting, Tracie Billington of the California
Department of Toxic Substance Control, stated that The Department of
Health Services Office of Drinking Water has specific restrictions on the
reuse of treated groundwater for consumption. However, they may allow
consumption in cases wh~ no other reasonable alternatives exist. If the
water were to be reused for consumption, additional regulations would
have to be complied with. Camilla Wi]liamc; of the Central Valley Regional
2
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P/SHARPElRESPSUM.3
01/11/93
Water Quality Control Board (CVRWQCB) stated that the board has a
preference for water being reused/recycled. The project team is actively
investigating potential opportunities for using treated water for irrigation.
4. Mr. Rick Reilla, a land owner east of SHARPE, expressed concern
about TCE emissions from the air stripper and the added impacts of
the new system being installed in the Cetttra1 Area. .
DDRW Resnonse: Air modeling was perfonned to assess risks associated
with TCE emissions and concluded that no significant risks were associated
with the treatment systems. The system to be installed in the Central Area
will have an offgas treatment system to remove TCE from air emissions
prior to releasing them to the atmosphere. Additionally, previous studies
conducted at the site were unable to detect TCE in air downwind of the air
strippers.

5. In a March 6, 1992 letter, CVRWQCB provided written comments
regarding an outstanding. concern about cleanup levels.
DDRW ResDonse: That concern has been addressed and incorporated into
this ROD. DDRW addressed CVRWQCB's concern during the regulatory
agency negotiation of the ROD and is reflected in Tables 8 and 9 in the
Substantive Waste Discharge Requirements and in the text of the ROD.
4.0 REMAINING CONCERNS
None.
3
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P/SHARPEIRESPSUM.4
11/11/92
ATIACHMENT
. COMMUNfIY RElATION ACI1VlTIES
AT SHARPE
Conununity relations activities conducted at SHARPE to date include the
following: .
1. Preparation of a PIRP,
2. Establishment of a TRC chatter,
3. TRC meeting held in June 1990, and
4. TRC meeting held in December 1990.
4
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.
ADDENDUM TO ROD
SUBSTANTIVE WASTE DISCHARGE REQUIREMENTS
FOR LAND DISPOSAL
DEFENSE DISTRIBUTION REGION WEST, SHARPE
6 NOVEMBER 1992
The United States Defense Logistics Agency, Defense Distribution Region West
(DDRW), Sharpe, hereafter referred to as Di scharger, in order to meet the
provisions contained in Division 7 of the California Water Code and regulations
adopted thereunder, shall comply with the following:

A. Discharge Prohibitions:
1. Bypass or overflow of untreated or partially treated waste is.
prohibited.
2~ Discharge of waste classified as 'hazardous' or 'designated', as defined
in Sections 2521(a) and 2522(a) of Chapter 15, Division 3, Title 23,
California Code of Regulations, is prohibited.
3. Discharge in violation of State Board Resolution 68-16 (Antt-Degradation
Policy) is prohibited.
4. Discharge shall occur only to the following:
a. Approved industrial or municipal reuse.
b. Approved on-site land disposal using:
i. Injection Wells. .
ii. Percolation Pond.
c. South San Joaquin Irrigation District Canal (National Pollutant
Discharge Elimination System permit).

B. Effluent Limitations:
1. The discharge of effluent in excess of the following limits is
prohibited:
Maximum Monthly
Da il y Median
Compound Units Concentration Concentration
Tetrachloroethylene (PCE)1 ~g/l 1 0.5
Trichloroethylene (TCE)1 ~g/l 1 0.5
Total Volatile Organic
Constituents (VOCs)Z ~g/l 5 1.0
Arsenic ~g/l 5 or background
1 EPA Method 502.2 with a detection limit of 0.01 ~g/l or less. If the
Daily Maximum is exceeded, an additional sample(s) must be collected and
analyzed within the same month to demonstrate that the monthly median has not
been exceeded.
Z Total VOCs will be the sum of all halogenated EPA Method 502.2
(detection limit of 0.01 ~g/l) constituents, including PCE and TCE.
A-I
. .
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Substantive Waste Discharg~ Requirements
DDRW, Sharpe
-2-
Compound

Selenium
Nitrate
Bromacil
Benzene
BTXE'
Units
10' g /l
mg/1
10' g /l
Io'g/l
10' g /l
Maximum
Da i 1 y
Concentration
Monthly
Median
Concentration
5 or background
10 or background
90
1.0
5
90
0.5
0.5
2. The pH of the treated ground water shall be between a pH of 6.5 and 8.5
or equivalent to the pH of the receiving ground water.

3. Additional effluent limitations may be required based upon analysis
results obtained after commencement of the full scale operation. These
analyses may be necessary to assure the protection of the receiving
ground water from the disposal of the treated ground water, in
compliance with the Anti-Degradation Policy.
4. The best available technology (BAT) for removal of VOCs shall be
employed. Air stripping has been determined to be the BAT for VOCs in'
ground water at DDRW, Sharpe.

C. Discharge Specifications
1. The Discharger's ground water treatment system (GWTS) in the North and
South Balloon and Central Areas consists of ground water extraction from
the A, B and C Zones and treatment with air stripping column(s). In the
Central Area, the treated ground water from the A Zone, which contains
elevated levels of arsenic, selenium and nitrates, will be discharged by
reinjection into the A Zone and by on-site ponding. The treated ground
water from the Band C Zones will be discharged by reinjection into the
Band C Zones and by ponding.

Prior to beginning full scale operation of the Central Area GWTS, the
Discharger shall perform the following:
2.
a. Potable Water start-up Phase (PWSP)
b. Treatment Performance Evaluation (TPE)
c. Prove-Out Phase (POP) of System
d. Full Scale Operation (FSO)

3. During all phases of operations, the Discharger shall comply with the
following:
3 Benzene, Toluene, Xylene and Ethy1benzene (STXE)
A-2
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Substantive Waste Discharg~ Requirements
DDRW, Sharpe
-3-
Neither the treatment nor the discharge shall. cause a nuisance or
condition of pollution as defined by the California Water Code,
Section 13050.

b. The discharge shall not cause degradation of any water supply.
a.
..
c. Any collected screenings, sludges, and other solids removed from
liquid wastes shall be disposed of in a manner consistent with
Chapter 15.

4. The discharge of treated ground water from the Central Area GWTS shall
not exceed the design capacity determined during the POP of the System
without prior approval from the Board, Department, and the US EPA.
5. During the initial period, not to exceed three months, of the FSO, the
Discharger will employ operational procedures to prevent excursions from
the effluent limits listed in .paragraph B.1. Operational procedures may
include the following: .

a. Blending of waste streams from the North and South Balloon Treatment
Plants with the Central Area Treatment Plant.
b. Aeration of the waters prior to discharge to or in the percolation
pond for the Central Area treated ground water.
c.
Industrial or municipal reuse.
D. Provisions:

1. The Discharger is require to report on all phases of operation to the
Board, Department, and the US EPA. All phases of operation must be
described in detail in the Remedial Design/Remedial Act ion (RD/RA)
Report(s) for the ground water remedial action. .
2. The Discharger shall comply with the attached Monitoring Program, which
is part of these substantive waste discharge requirements, and any
revisions thereto as ordered by the Board~ Department~ and the US EPA.

3. The Discharger shall notify the Board, the Department and the US EPA
within 24 hours of any unscheduled shutdown of the Sharpe GWTS. This
notification shall include the cause of the shutdown and the corrective
action taken (or proposed to be taken) to restart the system.
4. The Discharger shall noti.fy the Board, the Department and the US EPA
immediately, during normal working hours via telephone, and at least
within 24 hours of any spill of untreated water. This notification
shall include the size and cause of the spHl, any inmediate damage to
the environment, any corrective/cleanup actions taken and/or additional
monitoring proposed. .
A-3
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Substantive Waste Discharge Requirements
DDRW, Sharpe
-4-
5. The Discharger shall submit to the Board, the Department and the US EPA
quarterly operation reports by the 15th day of the second month
following the quarter. These. operational reports shall contain a
summary of the operating parameters, operation and maintenance (O&M)
activities, and a summary of any shutdown or spill events that occurred
during the quarter.

The system evaluation shall be described in the Quarterly Ground Water
Monitoring Report(s). The evaluation shall cons~der:
a.
Water levels and water quality data from the performance monitor
wells for the extraction system to demonstrate that the capture
zones of the extraction system maintains hydraul ic control, to the
maximum extent feasible, of the VOC plume exceeding the aquifer
cleanup level.

Water levels.and water quality data from the performance monitor,
wells for the injection system to monitor the hydraulic effects' ,
on the ground water flow patterns and to demonstrate whether or
not the discharge of treated ground water degrades the receiving
water quality. .
b.
Operational procedures for optimization of the ground water
extraction and injection systems.

6. The Discharger shall submit to the Board, the Department and the US
EPA, an Annual Report which summarizes the findings of the previous
four quarters and shall make recommendations for optimization of the
extraction and treatment systems, including changes in O&H and ground
water monitoring, if necessary.
c.
7. The Discharger shall comply with the RMonitoring ProgramD, dated
6 November 1992, which are attached hereto and by reference a part of
these substantive requirements. The Monitoring Program will be
incorporated into the comprehensive site-wide ground water monitoring
program for the North and.South Balloon and Central Areas.

8. The Discharger shall report promptly to the Board, the Department and
the US EPA any material change or proposed change in the character,
location, or volume of the discharge.
9.
In the event of any change in ownersh i p of 1 and or waste discharge
facilities presently owned or controlled by DDRW, Sharpe and associated
with the ground water cleanup of the DDRW, Sharpe site, the Discharger
shall submit, within 180 days prior to transfer of land, a formal
application for Waste Discharge Requirements to the Regional Board~ In
addition, the Discharger shall notify at that time the succeeding owner
or operator of the existence of these substantive requirements by
letter, a copy of which shall be forwarded to this office.
A-4
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Substantive Waste Discharge' Requirements
DDRW, Sharpe
-5-
10. A copy of these substantive waste discharge requirements shall be kept
at the discharge facility for reference by operating personnel. Key
operating personnel shall be familiar with its contents.
11.
Both the Board and the Discharger will periodically review these
substantive waste discharge requirements. ~nd may propose revisions
prior to the five year Record of Decision' (ROD) review. However,
should significant changes be required.to any of the treatment systems,
then these changes may be done through a ROD amendment.
CKW:cw
A-S
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A-6
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ADDENDUM TO ROD
MONITORING PROGRAM
FOR LAND DISPOSAL
DEFENSE DISTRIBUTION REGION WEST, SHARPE
6 NOVEMBER 1992
The following Monitoring Program contains the minimum monitoring requirements
necessary .to determine compliance with the Substantive Waste Discharge
Requirements. Monitoring requirements are established for four (4) different
phases of the ground water treatment system (GWTS): the potable water start-up
phase (PWSP), treatment performance evaluation (TPE) phase, prove-out (POP)
phase, and full-scale. operation (FSO) phase. In addition, monitoring
requirements are established to determine if reinjection of the treated ground
water will degrade the receiving water.
..
All monitoring samples will be 'grab' type samples, except for extraction and
injection rates and total volume, which will be continuous, and water level
measurements, which will be instantaneous at the time of measurement. Samples
will be collected at one of the following frequency schedules or as agreed upon
through the Remedial Design approval process:
- ,
Sampling Frequency
A
Definition
At initiation of start-up and once every hour to end of
test.
B
A minimum-of three shall be collected throughout the test,
including a baseline, if appropriate, and at the mid-point
and at the end of the test.

At start-up and at end of POP.
C
D
E
F
A minimum of four throughout the test, including at the
beginning and at the end of the test, however the total
collected shall not exceed eight.

Weekly for first month and twice a month thereafter.
Monthly for the first quarter and quarterly thereafter.
POTABLE WATER START-UP PHASE (PWSP) MONITORING
The objectives of this phase are to determine if the system components are
operating correctly, if the system leaks and to determine the injection capacity
of the injection well using potable water.

Injectio.n We11s
During the injection of potable water into the injection well, the following
monitoring programshal.l be conducted on the injection wells:
A-7
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Substantive. WDRs Monitoring-Program
DDRW, Sharpe
-2-
Constituents
Injection Rate
Units
Sampling Frequency
D
Volume of Injected Water (Cumulative)
Performance Monitor Wells for Injection System
gpm
ga 11 ons
End of Test
The performance monitor wells for the injection system shall be monitored during
the injection of the potable water as follows:
Constituents
Units
Ground Water Elevation
ft (msl)
Sampling Frequency
A
TREATMENT PERFORMANCE EVALUATION (TPE)
, .
The objectives of this phase are to monitor the extraction welles) performance
and to determine the effectiveness of the treatment system to meet the treatment
objectives. Injection of the treated ground water during the TPE is prohibited.
The following sampling frequency schedules will be used for the various
monitoring locations:
Treatment System

During the TPE phase of the GWTS, the following analyses shall be conducted at
both the influent and effluent points of the treatment system:
Constituents

Volatile Organics
(Method 601/602 for the influent and
Method 502.2 for the effluent)
Units
Sampling Frequency
B
ll9/l
pH
mg/l B
I£IIIhos/cm B
pH units B
of or °C B
gpm B
ga110ns End of Test
Total Dissolved Solids
Electrical Conductivity
Temperature
Flow Rate
Volume of Treated Water (Cumulative)
A-8
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Substantive WDRs Monitoring-Program
DDRW, Sharpe
-3-
Extraction Wells
Each of the extraction well(s) shall be monitored for the following during the
TPE:
Constituents
Extraction Rate
Units
Sampling Frequency
gpm
B
Performance Monitor Wells for Extraction System

The performance monitor wells for the extraction system shall be monitored for
the following during the TPE:
Ground Water Elevation
ft (msl)
Sampling Frequency
B
Constituents
Units
PROVE-OUT PHASE (POP) MONITORING
The objectives of this phase are to characterize the influent and effluent
streams, determine the. treatment efficiencies of the treatment system, and
monitor the performance of the extraction and injection wells. The Discharger
shall provide a letter report after completing the POP which provides the
analytical results from samples collected during the pop and describes any
actions taken ~uring the POP to improve the performance of the treatment system.
The following sampling frequency schedules will be used for the various
monitoring locations:

Treatment System
. .
VOC analyses shall be conducted on influent and effluent water samples from the
air stripping tower.
Constituents

Volatile Organic
(Method 601/602 for the influent and
Method 502.2 for the effluent)
Units
I£g/l
Sampling Frequency
C
Electrical Conductivity
pH
"""hos/cm C
pH units C
of or °C C
gpm C
Temperature
F1 ow Rate
A-9
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Substantive WDRs Monitoring .Program
DDRW, Sharpe
Constituents
Units ...
gal/day
Volume of Treated Water (Cumulative)
Extraction Wells and Extraction Performance Monitor Wells
-4-
Sampling Frequency
C
During ground water extraction, each of the extraction wells .and performance
monitor wells for the extraction system shall be monitored as follows:
~hos/cm C
pH units C ,
of or °C C
gpm End of Test
ga 11 ons End of Test
Constituents

Volatile Organics
(Method 601/602 for the influent and
Method 502.2 for the effluent)
Units
1£9/1
Electrical Conductivity
pH
Temperature

Extraction Rate
(Extraction Wells Only)
Volume of Extracted Water (Cumulative)
(Extraction Wells Only)

Injection Wells
. Sampling Frequency
C
During the injection of treated ground water into the injection well, the
following monitoring program shall be conducted at each injection well:
Constituents
Units
Injection Rate
Volume of Injected Water (Cumulative)
gpm
gallons
Sampling Frequency
o
End of Test
Injection Performance Monitoring Wells

The following shall be monitored in all of the performance monitor wells for the
injection system:
Constituent
Units
1£9/1
Volatile Organics (Method 601)
Electrical Conductivity
,unhos/cm
A-IO
Sampling Frequency
D
o
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I
I
, '
..
" " .,- ' ," ,Substant i ve WDRs Mon i tori ng Program
,:',' ",: .:~ ~DDRW, Sharpe
-5-
Constituent Units Sampling Frequency
pH pH units D
Temperature, of or °C D
Ground Water El~vation ft' (msl) D
FULL SCALE OPERATIONAL (FSO) PHASE ~ONITORING
The objective of this phase is to operate the Central Area ground water treatment'
system in the most optimal manner and to comply with the effluent limits in the
waste discharge requirements. The following sampling frequency schedules will
be used for the various monitoring locations:

Treatment System
During the FSO, the following analyses shall be conducted at the influent and
effluent points of the GWTS. Each interruption of the GWTS, greater than 72
hours in duration, shall, require that the Discharger begin monitoring weekly for
the first month prior to resuming sampling twice a month.
Constituent
Volatile Organics
(Method 601/602 for the influent and
Method 502.2 for the effluent)
Units
Sampling Frequency
E
~jl
Electrical Conductivity
IWhosjcm E
pH units E
of or °C E
gpm E
gall ons E
pH
Temperature
Flow Rate
Volume of Treated Water (Cumulative)
Extraction Wells

The extraction wells for the GWTS shall include all present and future monitoring
as designated in the RD/RA Report(s). These wells shall be incorporated into the
quarterly ground water monitoring program and shall be monitored as follows:
Constituents
Units
~/l
Sampling Frequency
F
Volatile Organics
(Method 601)
A-ll
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Substantive WDRs Monitoring-Program
DDRW, Sharpe .
-6-
Constituents Units Sampling Frequency
Total Dissolved Solids mg/l Baseline Only
Electrical Conductivity ~hos/cm Quarterly
pH pH units Quarterly
Temperature of or.C Quarterly
Flow Rate gpm F
Volume of Extracted Water (Cumulative) gallons F
Performance Monitor Wells for Extraction and Injection Systems
. '.
The performance monitor wells for the extraction and injection sY$tems shall be
incorporated into the quarterly ground water monitoring program and shall be
monitored as follows:
, ~
Constituents Units Sampling'Frequency
Volatile Organics JS9/1 F
(Method 601)
Total Dissolved Solids DIg/l Baseline Only
El ectri ca 1 Conductivity _os Ie. Quarterly
pH pH units Quarterly
Temperature .F or .C Quarterly
Ground Water Elevation ft (msl) F
Injection V.11s
During the FSO-t the fpllowing monitoring progru shan be implemented at each
injection wen:
Constituents
Injection Rate,
Units
Sampling ~requ.ncy
Weekly
Volume of Injected Water (Cumulative)
gPII
gall ons
Weekly'
In addition, the RD/RA Report(s) shall include I table of the background
concentrations for the generll mineral Ind specific metll constituents in the
A-12
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,-
"t'
"..~
Substantive WDRs Monitoring Program
DDRW, Sharpe
-7-
North and South Balloon Areas and in the Central Area. This table shall be
prepared using the existing site-wide data from the Remedial Investigation and
shall be prepared fo~ the injection area after collecting ground water samples
from the performance monitoring wells for the injection well field. These data
are required to develop a baseline for the minerals and metals concentrations in
each of the water bearing zones and are needed to determine if injection of the
treated ground water degrades water quality. The Discharger must also collect
and analyze for VOCs (Methods 601/602), as a baseline, at each injection well and
performance monitor well for the injection system prior to start up of the
injection.

The Discharger shall collect samples from the influent and effluent at the North
and South Balloon and Central Area Treatment Plants for a minimum of ,two
quartlrs. These samples shall be analyzed for general mineral and specific metal
constituents. The analytical results from the treatment systems are needed to
determine if treatment has an impact on water quality.
...,
The Discharger shall analyze the above samples for dissolved minerals and metals.
Ranges of background concentrations for each of the following constituents shall
be listed in the table: '
, "
Chloride
Sulfate
Nitrate
Total Dissolved
Solids
Carbonate
Bicarbonate
Alkalinity
Hardness
(as CaCOJ)
Arsenic Z
CalciUII 1
Copper 1
Iron 1
MagnesiUII 1
Manganese 1
PotassiUID ,1
Selenium Z
Sodium 1
Zinc 1
.....
1 Inductively Coupled Argon Plasma Atomic Emission Spectroscopy (ICAP) may be
used for analysis of these constituents (Method 6010)
Z Atomic Absorption (Method 20&.3 for Arsenic and Method 270.3 for Seleniua)
The ground water surface elevation (in feet, 811) in all wells shall be measured
on a quarterly basis and used to determine the magnitude and direction of ground
water f1~. Th1~ information shall be displayed on a water table contour map.
QUALITY CONTROL SMPLES

For quality control purposes the Discharger shall collect and have analyzed one
sampling blank and one duplicate for every twenty samples or for every group,
whichever is less, collected and'analyzed. Each of these quality control samples
shall be analyzed for the same'parameters as the other samples collected.
CKW
A-I3
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