United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R09-88/025
September 1988
SEP A
Superfund
Record of Decision
Selma Treating, CA
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30277-101
REPORT DOCUMENTATION
PAGE
TT-REPORT NO.
EPA/ROD/R09-88/025
3. Recipient's Accession No.
4. Title end Subtitle
SUPERFUND RECORD OF DECISION
Selma Pressure Treating Company, CA
Remedial Action - Final
5. Report Dete
09/24/88
Authors)
8. Performing Organization Rept. No.
9. Performing Organization Name and Address
10. Project/Task/Work Unit No.
11. Contraet(C) or Grant(G) No.
(C)
(C)
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report & Period Covered
800/000
14.
IS. Supplementary Notes
J
i
16. Abstract (Limit: 200 words)
The Selma Pressure Treating Company is located in Selma, California, 15 miles south of
the City of Fresno. The site encompasses approximately 18, acres, including a 3 to
4-acre wood treatment facility and 14 acres of adjacent vineyards that were used for
site drainage. Land use in.the vicinity of the site includes agricultural, residential,
and industrial areas, with 12 residences and businesses located within 0.25 mile. The
ground water resources in the area have been classified as a Sole-Source Aquifer and a
urrent drinking water source with other beneficial uses. Wood preserving activities
sing pentachlorophenol (PCP) were conducted at the site from 1942 until 1965 under a
series of owners. In 1965, a new facility was constructed converting operations to a
pressure treating process using chemical preservatives. Prior to 1982, wastes generated
from spent retort fluids and sludges were discharged to drainage and percolation
ditches, dry wells, and an unlined pond and sludge pit, as well as onto open ground and
the adjacent vineyards. An inspection conducted by EPA in 1981 raised concerns about
the potential for ground water contamination, and as a result the company was required
to modify its operations to minimize the potential for contamination. The total volume
of soil requiring remediation is approximately 16,100 yd^. The primary contaminants
of concern affecting the ground water and soil are organics including dioxin and
(See Attached Sheet)
17. Document Analysis .a. Descriptors
Record or Decision
Selma Pressure Treating Company, CA
First Remedial Action - Final
Contaminated Media: gw, soil
Key Contaminants: organics (dioxins/furans, phenols), metals (arsenic, chromium)
b. Identlfiars/Open-Endad Terms
c. COSATI Field/Group
Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
126
22. Price
(See ANSI-239.18)
Sae /nitructiont en Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce .
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Ei,
i
EPA/ROD/R09-88/025
elma Pressure Treating Company, CA
irst Remedial Action - Final
16. ABSTRACT (continued)
phenols, and metals including arsenic and chromium.
The selected remedial action for this site includes: ground water pump and treatment
using precipitation, coagulation, and flocculation with reinjection into the aquifer or
offsite discharge; soil excavation and solidification/stabilization with replacement in
excavated areas and capping fixed soil with a RCRA cap; ground water and soil monitoring
for approximately 30 years; and long-term access and land use restrictions for fixed
areas and short-term institutional controls for ground water use. The estimated present
worth cost for this remedial action is $11,280,000 with annual O&M of $1,300,000.
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RECORD OF DECISION
FOR THE
SELMA PRESSURE TREATING COMPANY
SUPERFUND SITE
PREPARED BY
THE U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION IX
SAN FRANCISCO, CALIFORNIA
SEPTEMBER, 1988
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TABLE OF CONTENTS
SELMA RECORD OF DECISION Page
Declaration for the Record of Decision 1
Decision Summary 3
I. Site Name, Description, and Location 3
II. Site History and Enforcement Activities.... 5
III. Community Relations .8
IV. Site Characteristics 9
A. Surface and Subsurface Soil Results 9
B. Soil Clean-up Goals and Areas
Requiring Remediation. 15
C. Groundwater Results 16
D. Groundwater Clean-up Goals 19
V. Summary of Site Risks... 20
A. Chemicals of Concern ' 20
B. Exposure Pathways ....21
C. Toxicity of Chemicals of Concern 21
D. Risk Characterization 22
E. Analytical Methods Used 24
VI. Documentation of Significant Changes/
Section 117(b)&(c) 24
VII. Description of Alternatives 24
A. Alternative 1 24
B. Alternative 2 24
C. Alternative 3 26
D. Alternative 4 30
VIII. Summary of Comparative Analysis of Alternatives 32
A. Overall Protection of Human Health and the
Environment. 32
B. Compliance with ARARS 33
C. Long-term Effectiveness and Permanence .33
D. Reduction in Toxicity, Mobility, and Volume 33
E. Short-term Effectiveness 34
F. Implementability 34
G. Estimated Capital, O&M, and Present Worth Cost 35
H. State and Community Acceptance 35
XI. The Selected Remedy 35
X. The Statutory Determinations 36
A. Protection of Human Health and the Environment 36
B. Attainment of ARARS 36
C. Cost-effectiveness 37
D. Utilization of Permanent Solutions Employing
Alternative Technologies to the Maximum Extent
Practicable 38
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-1-
DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
The Selma Pressure Treating Company (SPT) site is located in
Selma, California, 15 miles south of the City of Fresno, in
California's Central Valley.
STATEMENT OF BASIS AND PURPOSE
This decision document represents the selected remedial action
for the Selma Pressure Treating site, developed in accordance
with the Comprehensive Environmental Response, Compensation and
Liability Act of 1980, as amended, and the National Contingency
Plan. This decision is based on the administrative record for
this site. (The attached index identifies the items which
comprise the administrative record upon which the selection of
the remedial action is based). The State of California has
concurred on the selected remedy.
DESCRIPTION OF THE SELECTED REMEDY
This Record of Decision (ROD) for the Selma Pressure Treating
site includes the following actions to address contaminated
soil and groundwater for the entire site (there are no operable
units):
0 Conventional water treatment to remove chromium from the
groundwater, including:
Extraction of contaminated groundwater
Treatment of contaminated groundwater using precipitation,
coagulation, and flocculation processes to remove chromium
to meet the applicable drinking water standard
- Disposal of treated and tested groundwater by reinjection
into the aquifer or off-site disposal, as appropriate
- Groundwater monitoring to verify contaminant clean-up
0 Soil fixation with a Resource Conservation and Recovery
Act (RCRA) Cap to treat contaminated soil, including:
- Excavation of contaminated soils exceeding cleanup goals
- Mixing soils with a fixative agent to solidify and stabilize
contaminated soil
- Replacement of fixed soil into excavated areas and covering
the fixed areas with a RCRA Cap
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-2-
- Long term monitoring of fixed soils for a period of
approximately 30 years
Long-term access and land use restrictions for fixed
areas and short-term institutional controls to prevent
use of contaminated groundwater until remediation is complete
DECLARATION
The selected remedy is protective of human health and the envi-
ronment f attains federal and state requirements that are
applicable or relevant and appropriate to this remedial action
and is cost-effective. The groundwater remedy satisfies the
statutory preference for remedies that employ treatment that
reduces toxicity, mobility, or volume as a principal element and
utilizes permanent solutions to the maximum extent practicable.
The soil fixation/RCRA Cap element of this remedy is not considered
fully permanent/ due to the need for long-term monitoring. It
does employ treatment that significantly reduces mobility as a
principal element. However, toxicity is not reduced and volume
is increased due to addition of the fixative agent.
Because this remedy will result in hazardous substances remain-
ing on the site, a review will be conducted within five years after
commencement of the remedial action to ensure that the remedy con-
tinues to provide adequate protection of human health and the
environment. The State's letter of concurrence is attached.
Daniel W. McGovern Date
Regional Administrator
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-3-
DECISION SUMMARY
I. SITE NAME, DESCRIPTION, AND LOCATION
The SPT site is located about 15 miles south of Fresno and
adjacent to the southern city limits of Selma (Figure 1).
Dockery Avenue and Golden State Boulevard (old Highway 99)
mark the entrance to the site. The SPT site comprises
approximately 18 acres, including a 3-4 acre wood treatment
facility and 14 acres of adjacent vineyards that were used
for site drainage.
Zoned for heavy industrial use, SPT is located in a transition
zone between agricultural, residential, and industrial areas.
Situated in the center of the San Joaquin Valley, the area
contains many vineyards, and Selma is labeled the "Raisin
Capital of the World." Urban residential areas lie to the
north, and scattered suburban dwellings surround the site.
Approximately 12 residences and/or businesses are located
within 1/4 mile of the SPT site. Currently, a wood treating
facility, Selma Treating Company (STC), is operating at the
SPT site. STC is owned by Saw Mill Properties, Inc. STC
operations are regulated by state Waste Discharge Requirements
Order No. 78-171, which precludes discharges to areas
having hydraulic continuity with groundwater. At the time
STC began operating, the Regional Water Quality Control
Board (RWQCB) required installation of drip pads, berms
around the site, and runoff containment to prevent ongoing
contamination.
The Consolidated Irrigation District provides the majority of
the irrigation supply in the area. The surface water irriga-
tion supply is supplemented by groundwater resources in the
vicinity of the site, the groundwater resources also supply
the necessary domestic water for the surrounding communities
and the scattered county residences. The regional groundwater
gradient in the vicinity of the site is to the southwest.
The groundwater resources in the area of the SPT site have
been classified as a Sole-Source Aquifer by the U.S. Environ-
mental Protection Agency, under the Safe Drinking Water
Act, 42 U.S.C. §1424(e). Under EPA's Groundwater Protection
Strategy (1984), the aquifer in the SPT area has been classi-
fied as a Class II A current drinking water source with other
beneficial uses.
No other significant natural resources were found at SPT,
such as federal or state rare, threatened, or endangered
species, or wetlands. The site is not included on the
National Register of Historic Places under the Historic
Preservation Act of 1966, 16 U.S.C. §470 et seq.
The climate for the site consists of hot summers and mild
winters. The maximum temperatures are generally around 100°F
in July, with a minimum temperature of 35° in January.
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CALIFORNIA
"*'-'' '"'
Ban
Francisco
Selma
Project Site
Selma Pressure
Treating Site
. .._ -JLJ; -_
* /- -'*.~ .-"?
*^- ru^^Ai «%»":
4- iy-i^"**
!--
north
Ol 2343
Project No.
123-RI1
Selma Pressure Treating Site
Camp Dresser & McKee Inc.
REGIONAL LOCATION MAP
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-5-
Average annual precipitation in the area is less than 10
inches. The monthly evaporation losses range from two inches
per month during the winter to 18 inches per month during the
summer.
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
Treatment of lumber products has been ongoing at the SPT
site since 1942. The original wood treatment facility
covered approximately 3-1/2 acres. In 1961, the treatment
operation was taken over by Gerald Petery, the son of the
original owner, and his wife, Mary Ann Petery (now Schuessler).
A summary of the operating history of the Potential Responsible
Parties (PRP's) is as follows:
Dates
1961-1/1970
1/1970-12/1977
1971-Present
12/1977-late/1981
4/1981
2/1982
2/1982-Present
Owners
Gerald Petery and Mary Ann Petery operated
the facility as individuals.
Gerald Petery and Mary Ann Petery incor-
porated as Selma Pressure Treating
Company, which was responsible for
operating the facility.
Selma Leasing Company (SLC) was organ-
ized and owned by Gerald Petery. SLC
became the owner of the land upon
which SPT, and later Saw Mill Properties,
Inc., operated.
Gerald Petery sold his interest in SPT
to Mary Ann Schuessler (formerly Petery).
Mary Ann Schuessler became the sole
owner, president, and operator of SPT.
SPT filed for bankruptcy and First Inter-
state Bank or a trustee took over the
operation.
SPT's trustee sold wood treating assets
to Saw Mill Properties, Inc.
Saw Mill Properties, Inc. has operated
the facility, as Selma Treating Company.
The wood-preserving process originally employed at the site
involved dipping wood into a mixture of pentachlorophenol
and oil, and then drying the wood in open racks to let the
excess liquid drip off. A new facility was constructed
in 1965, and SPT converted to a pressure treating process
which consisted of conditioning the wood and then impregna-
ting it with chemical preservatives.
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-6-
Prior to 1982, discharge practices included: (1) runoff
into drainage and percolation ditches, (2) drainage into
dry wells, (3) spillage onto open ground, (4) placement into
an unlined pond and sludge pit, and (5) discharges to the
adjacent vineyards. These wastes were generated from spent
retort fluids and sludges. Figure 2 depicts these disposal
sites.
Between 1971 and 1981, the Regional Water Quality Control
Board (RWQCB) regulated the discharges from SPT, under a
Waste Discharge Requirements Order. An Uncontrolled
Hazardous Site Investigation was conducted on January 31, 1981
in accordance with §3007 of the Resource Conservation and
Recovery Act (RCRA), by the EPA's Field Investigation Team
(FIT), the California Department of Health Services (DHS),
and the RWQCB. This inspection raised concerns about the
potential for groundwater contamination from the site. As
a result, SPT was required to modify its operation to minimize
the potential for contamination. Initial site investigation
activities were then conducted by the state and EPA to
assess contamination problems.
Between 1981 and 1984, RWQCB, EPA, and DHS pursued efforts
to have SPT and, later, SLC investigate the site to determine
the extent of contamination. In September of 1981, the
RWQCB issued a Cleanup and Abatement Order to SPT, requiring
a geotechnical investigation and establishing a timetable for
cleanup. The timetable for cleanup was not submitted to the
RWQCB and in September of 1984, the RWQCB referred the
Order to the California Attorney General's office, for
enforcement. The Attorney General's office is pursuing a
case against SLC, SPT, Gerald Petery, and Mary Ann Schuessler,
on behalf of itself and the RWQCB. Gerald Petery has
filed a cross-claim against a number of parties, including
Mary Ann Schuessler, various chemical manufacturers of PCP,
EPA's consultant, CDM, First Interstate Bank, Koppers, and
Osmose.
In September of 1983, DHS informed SPT of violations and
transmitted an Order, Settlement Agreement, and Schedule
of Compliance, including civil penalties of $75,000. In
December of 1983, DHS found SLC's counter proposal to this
Order to be unsatisfactory. DHS referred the site to EPA
for further action in April of 1984.
In August of 1983, EPA ranked the site using the Hazardous
Ranking System (HRS) 40 C.F.R. Part 300, Appendix A, as
authorized under 42 U.S.C. §105(a)(8), to determine whether
to include the site on the Superfund National Priorities
List of hazardous waste sites. The HRS ranking for the
site indicated that releases of hazardous substances from
the site may present a danger to human health and the enviroj
ment. Based on this information the site was placed on the
Superfund National Priorities List of hazardous waste sites
in September 1983. The HRS ranking was 43.83, and the site
was listed as number 195.
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-7-
VINEYARD
Waste Sludge Pit
Treatment
Area
Unlined Waste Disposal Pond
PIPELINE
DISCHARGE AREAS
DRAINAGE DITCH
PERCOLATION DITCH
DRY WELLS
AREAS WHERE SPILLS. LEAKS
DRIPPINGS HAVE OCCURRED
WASTE DISPOSAL SITES
PIPELINE FOR
DISCHARGE OF WASTE
0 100 200
Project No
Selma Pressure Treating Site
AREAS OF
SUSPECTED CONTAMINATION
Camp Dresser & McKee Inc.
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-8-
In September 1984, EPA requested Camp Dresser & McKee Inc.
(CDM), under their REM II contract, to prepare a Work Plan
outlining the tasks required to prepare a Remedial Investi-
gation and Feasibility Study (RI/FS) for the site. CDM
submitted the Work Plan outlining the RI/FS activities to
be conducted, on June 7, 1985. The various project plans
required to support the field investigation activities
were submitted in 1985 and 1986. Field activities were
initiated in April 1986, and were conducted in various
phases through August 1987. The final RI report (CDM, 1988)
provides the results of those field activities. An Endanger-
ment Assessment (EA) was prepared to assess risks to human
health and the environment associated with the No Action
Alternative (ICF, 1988). The FS report (CDM, 1988) analyzes
alternatives based on data collected and analyzed during the
RI investigation and based on the results of the EA.
Potentially Responsible Parties (PRPs) have not been involved
in development of the RI/FS. EPA is currently in discussion
with PRPs regarding the potential for their involvement in
the Remedial Design/Remedial Action (RD/RA) phases of this
project and for recovery of past costs. Special notice
letters will be issued in the near future under §122(e) of
CERCLA. PRPs identified include Gerald Petery, Mary Ann
Schuessler, and First Interstate Bank.
At present, technical discussions with PRPs have been limited
to formal comments on the FS/Proposed Plan and related meet-
ings. This information is included in the responsiveness
summary and is part of the administrative record.
III. COMMUNITY RELATIONS
The following is a summary of community relations activities
conducted by EPA for the SPT site, in order to meet the
requirements under Sections 113(k)(2)(i-v) and 117 of CERCLA.
Dates Activities
March/April EPA community relations (CR) represent-
1985 atives conducted community assessment
interviews with interested community
members in the Selma area.
July 1985 EPA distributed a fact sheet announc-
ing the commencement of RI/FS work,
and describing the RI/FS activities
to the community.
July 1985 EPA held a community meeting in Selma
to explain RI/FS activities that EPA
was undertaking and to respond to the
community's questions and concerns.
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January 1986
March 1986
May 1986
July 1987
April 1988
June 1988
June 22, 1988
September 1988
EPA finalized the Community Relations
Plan detailing the community concerns
as expressed in the July 1985 community
assessment interviews and communitty
meeting.
EPA distributed a fact sheet describ-
ing the purpose and nature of the
monitoring wells placed in the
Selma area. EPA also distributed a
Spanish translation of this fact
sheet.
EPA Community Relations Coordinator
met informally with community members
to listen to their concerns and to
explain current site activities.
EPA distributed well sampling results
to interested community members.
EPA distributed a fact sheet detailing
the results of the RI.
CPA distributed a fact sheet explain-
ing the contents of the FS Report and
announcing the upcoming public comment
period and community meeting.
EPA-held a community meeting to explain
the FS Report and to receive public
comment on EPA's Proposed Plan for
addressing the soil and groundwater
contamination at the SPT site.
Notice of this ROD, or Final Plan,
will be published and made available
to the public before commencement of
the remedial action.
IV. SITE CHARACTERISTICS
The following discussions address contamination problems
for the entire SPT site; there are no operable units
(i.e., sub-investigations) for this site. All data were
validated by Region 9, EPA, using standard review protocols
and data quality was considered in analysis of the data
and in reaching the decision.
A. Surface And Subsurface Soil Results
A total of 48 surface soil samples were collected during
two rounds of sampling. The samples were collected
from locations where waste was suspected to have been
discharged, from known waste disposal areas, and from
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-...u-
background locations. The samples were analyzed for a
variety of constituents, including: An initial screening
for Hazardous Substance List (HSL) volatiles, semi-vol-
atiles and metals; hexavalent chromium; individual
phenols; and dibenzodioxin/dibenzofuran (dioxin/furan)
chlorinated tetra through octa homologs. A subsequent
phase to confirm earlier results was performed and
included analysis for isomer specific chlorinated
dioxin/furans and metals. The site-related contaminants
of concern found in surface soils included chromium,
arsenic/ copper, dioxin/furan, pentachlorophenol
(PCP), and trichlorophenols (TCP).
A round of subsurface soil samples was collected at 21
boring locations during the RI field program (Figure
3). Samples were generally collected at the following
depths: 1 to 2.5 feet (ft.), 2.5 to 4.0 ft., 4 to 5.5.
ft., 10 to 11.5 ft., 15 to 16.5 ft., and 20 to 21.5
ft. (e.g. to the water table). The samples were
analyzed for individual phenols, chromium, arsenic,
and copper. Selected samples were also analyzed for
the tetra through octa chlorinated dioxin/furan homologs,
without identification of isomers. Chemicals of
concern for the subsurface soils were the same as for
the surface soils.
The soil sampling results identified seven areas where
past practices resulted in levels of contamination
above background concentrations that they warranted
further evaluation. The seven soil contamination
areas are the Waste Sludge Pit, North Unlined Percolation
Ditch (Ditch A), South Unlined Percolation Ditch
(Ditch B), Unlined Waste Disposal Pond, Drainage Area,
Southeast Disposal Area, and Southwest Disposal Area.
Table 1 provides the highest level for each of the
contaminants of concern detected in each area of
concern. Figure 4 identifies the location of each of
the areas. The boundary of each area was based on the
available sampling data and geographical features
associated with each site.
These locations represent areas of concern due to the
elevated levels of site-related contaminants detected
at each of these sites. For example, high levels of
arsenic, up to 4120 ppm, were detected at the Waste
Sludge Pit. High levels of arsenic were also detected
at the Unlined Waste Disposal Pond and Southeast
Disposal Area. Elevated levels of dioxin/furan contam-
ination, in tetra chlorinated dibenzodioxin (TCDD)
equivalents, were detected at the former Unlined Waste
Disposal Pond and the Southeast Disposal Area.
TCDD equivalents are a means of comparing the levels of
dioxin/furan contamination in various locations. The
toxicity of a particular dioxin/furan compound is
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Blaine Ave.
I S23
200 400 800
P1 WELL BORING LOCATION
SOIL BORING LOCATION
Project No.
123-FS1
Selma Pressure Treating Site
SUBSURFACE SOIL
SAMPLING LOCATIONS
Camp Dresser & McKee
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-12-
TABLE I MAXIMUM CONTAMINANT CONCENTRATIONS POUND IN SOILS
Location
Waste Sludge
f'n (Sample Sites
. W04, S34-S38)
- Surface
Unlined Percolation
Ditch A (Sample Sites
SI.S2. S3)
- Surface
1 to 2.5 ft.
- 2.5 to 4 ft.
- 4 to 5.5 It
- 10 to II 5 ft.
- 15 to 16 5 It.
-20 10 21. 5 ll.
Unlined Percolation
Ditch B (Sample Sites
S4, S5)
- Surface
- 1 to 2.5 It
- 2.5 to 4 It.
- 4 to 5.5 It.
- 10 to 11.5 It.
IS to 16 5 It.
-20 to 21. 5 It.
Unlined Waste
Disposal Pond (Sample
sites W03, S29 - S3J)
- Surface
Southwest
Disposal Area
(Sample site S7)
- Surface
- 1 to 2.5 It.
- 2.5 to 4 It.
- 4 to 5.5 ft
- 10 to 11.5ft.
- 15 to 16.5 ft.
-20 to 21. 5 It.
Arsenic
mg/kg
4120
55
ND
22
23
3.2
3.5
ND
ND
3.7
12
6.3
5.3
ND
ND
M50
21
31
25
28
9.9
17
8.8
Chromium
mg/kg
3910
1%
13
9.7
9
8
II
12
12
15
23
19
II
13
12
879
24
31
15
II
8.9
67
7
Copper
mg/kg
1870
121
14
9.6
10
7.3
12
IM
17
II
10
12
18
8.3
12
553
9
56
ND
ND
6.3
51
ND
PCP
Hg/kg
11000
1100
32
34.9
365
21.1
ND
43
ND
ND
23.1
340
11.4
26
ND
460,000
ND
ND
ND
ND
ND
ND
234
Total
TCP
0g/kg
R
R
277
4.9
14
80
ND
3V
ND
10
ND
ND
13
ND
41
R
ND
3
ND
ND
ND
ND
8.0
Total
Dioxins
ng/g
283.8
130.2
63.2
32.9
40.3
2.5
NS
1.0
7
09
08
12.5
02
NS
ND
1228.7
1253.7
621.3
21.1
2.64
1.7
NS
O.I
Total TCDD
Furans EQUV
ng/g ng/g
56.6 .29
40.1 .31
11.5
2.7
10. 1
0.48
NS
0.18
2.5 .01
ND
O.I
2.5
ND
NS
ND
634 565
3619 .29
119.7
0.7
ND
ND
NS
ND
Total
TCDD
ng/g
ND
ND
ND
ND
ND
ND
NS
ND
ND
ND
ND
ND
ND
NS
ND
ND
ND
ND
ND
ND
ND
NS
ND
Total
TCDF
"g/g
ND
ND
ND
ND
ND
ND
NS
ND
ND
ND
ND
ND
ND
NS
ND
ND
0.12
0 19
ND
ND
ND
NS
ND
Total
PeCDD
ng/g
ND
ND
ND
ND
ND
ND
NS
ND
ND
ND
ND
ND
ND
NS
ND
ND
ND
ND
ND
ND
ND
NS
ND
Total
PeCDF
ng/g
ND
0.7
O.OS
ND
ND
ND
NS
ND
ND
ND
ND
ND
ND
NS
ND
11.9
2.8
1.0
ND
ND
ND
NS
ND
Total
HxCDD
ng/g
3.4
3.4
0.71
0.21
0.85
NA
NS
ND
ND
ND
ND
ND
ND
NS
ND
117
12.7
7.3
ND
ND
ND
NS
ND
Total
rUCDF
ng/g
6.8
5.4
1.7
I.I
1.3
0.061
NS
ND
ND
ND
0.21
0.28
NA
NS
ND
232
64.7
24.6
0.11
ND
ND
NS
ND
N/A Not Available R: Data Rejected during data validation TCDD: Tetrachlorodibenzo-p-dioxins
ND Not Detected TCDD EQUV: TCDD equivalents
yS Not Sampled TCDF: Teirachloiodibcn/.ofuran*
2 Total dio»in/furan analysis includes Teira through Ocia honiologs. of which the Octa homolo|> is considered innocuous.
TCDD Equiv. are based on both the isotner specific and homolog data.
PeCDF: Pentachlorodibenzofurans
HxCDD: Hcxachlorodibenzo-n-dioxins
HxCDF: Ifcxachforodibenzofuran
PeCDD: Pemachlorodibenzo-n-dioxins
-------
-13-
TABLE I MAXIMUM CONTAMINANT CONCENTRATIONS FOUND IN SOILS (continued)
Location
Drainage
Area (Sample site S9)
- Surface
- 1 to 2.5 ft.
- 2.5 to 4 It.
- 4 to 5.5 ft.
- 10 to II 5 h
- IS to 16.5 ft.
- 20 to 21. 5 h.
Arsenic
mg/kg
12.2
5.0
14.0
13.0
2.1
R
1.4
Chromium
mg/kg
25
21
14
10
ND
ND
1.1
Copper
mg/kg
IS
1.1
11
12
9.2
1.4
13
PCP
"g/kg
ND
ND
ND
ND
ND
ND
ND
Total1
TCP
*g/kg
ND
ND
ND
ND
ND
ND
ND
Total1
Dioxins
ng/g
28.3
0.5
13.2
11.4
0.6
NS
0.3
Total1
Furans
ng/g
6.8
O.I
2.0
.n
ND
NS
ND
TCDD2
EQUV
ng/g
.03
Total
TCDD
"g/g
ND
ND
ND
ND
ND
NS
ND
Toial
TCDF
ng/g
ND
ND
ND
ND
ND
NS
ND
Total
PeCDD
ng/g
ND
ND
ND
ND
ND
NS
ND
Tolal
PeCDF
ng/g
ND
ND
ND
ND
ND
NS
ND
Total
HxCDD
ng/g
0.38
ND
0.052
ND
ND
NS
ND
Total
HxCDF
ng/g
0.64
ND
0.16
ND
ND
NS
ND
Southeast
Disposal Area (Sample
sites WOS. S39 - S44)
- Surface
461
390
422
200.000
92
23I6.S
2214.2
1.62
ND
ND
ND
8.2
45
86.2
N/A Not Available R: Data Rejected during data validation TCDD: Teirachlorodiben*o-p-dioxins
ND Not Detected TCDD EQUV: TCDD equivalents
|)S Not Sampled TCDF: Tetrachlorodiben/olurans
2 Total dioun/luran analysis includes Tctra through Octa homologs. of which the Oci» homolog ii considered innocuous.
TCDD Equiv. are based on both the Isoiner specific and homolog data.
PcCDF: Pentachlorodibenzofurans
HxCDD: Hexachlorodibenzo-p-dioxins
HxCDF: Hcxachlorodibenzoluran
PeCDD: Peniachtorodibcnzo-p-dioxins
-------
n, *l »> PHOIO « Ml 111(1 I WilHI I RINU.
v"i no» . C» Jir*. tor
B »J I mlin« !
«» toono.
Piojecl No
123-FS1
Selma Pressure Treating Si
EXTENT OF
SOIL CONTAMINATION
I Ilimtlid AIM 01 Sof fCf |
ConlMdnallon. «.lh SwlM*
AIM ki SB. r»i >:.»i
Camp Oresser & McKee
-------
dependent upon the degree of chlorination at the 2,3,7,8,
position. The exception to this is the octa chlorinated
dioxin/furan homologs, which are considered innocuous.
The remaining tetra through hepta isomers have various
degrees of toxicity. In order to assess the potential
toxicity associated with the dioxin data/ each sample
was evaluated with respect to 2,3,7,8 TCDD equivalents.
This involves converting each dioxin/furan homolog
into TCDD equivalents based on the EPA approved method-
ology using Toxicity Equivalent Factors (TEF).
Due to the lack of vertical extent data in source areas/
an estimate of vertical extent of contamination was
made to calculate volumes of soil requiring cleanup.
The metal contamination in the soil was assumed to
extend to a depth of 20 feet/ which corresponds to the
approximate depth of the water table. This assumption
is based on the results of the groundwater sampling/
which show elevated levels of chromium in the shallow
portions of the aquifer. Dioxin/furan contamination
is assumed to extend to 10 feet in depth based on
available subsurface sampling results from various
boring locations/ which indicate that dioxin/furan
contamination reaches permissible levels within the
first 10 feet. This is evident from Table 1 which
indicates that dioxin was detected in trace levels in
only one soil sample taken from below 10 feet. Additional
soil borings will be collected during RD/RA to refine
this information on vertical extent of contamination.
The site-related surface and subsurface soil contaminants
have variable mobilities in the environment. For
example/ dioxin/furan compounds have very low solubilities
and are extremely immobile in the soil. Copper is
also not very mobile in the environment due to its
strong affinity for clays, hydrous metal oxides, and
soil organic matter. Trivalent chromium has similar
sorption characteristics to copper, and as such/ tends
not to be very mobile. Hexavalent chromium is very
soluble and highly mobile in the environment. Furthermore/
hexavalent chromium is not easily sorbed on the soil.
However/ hexavalent chromium is only stable under
oxidizing conditions and will form trivalent chromium
in a reducing environment. In regard to PCP and
arsenic/ these compounds can be relatively mobile
under high pH environments. However/ these compounds
appear to be relatively immobile at the SPT site due
to the general lack of observed levels in the groundwater.
B. Soil Clean-up Goals and Areas Requiring Remediation
Of the organic contaminants at SPT/ the site-specific
risk assessment indicated that dioxin/furan would drive
the clean-up goals. The clean-up goal selected for
dioxin/furan contaminated soil is 1.0 ng/g (ppb), in
-------
-16-
TCDD equivalents. This clean-up goal is based on a
TCDD risk study performed by Kimbrough, et al. (1984)
of the Centers For Disease Control (CDC). This study
is the basis for EPA policy and clean-up goals at
Superfund sites where there is dioxin contamination.
The 1 ppb goal is for areas where potential residential
or agricultural uses could occur. While the SPT site
is currently used for industrial purposes, the 1 ppb
goal was selected due to the proximity of residences
and agricultural activities to the site.
The heavy metals of concern at SPT are arsenic, chromium/
and copper. Based on the health risk assessment, the
metals clean-up goals were driven by arsenic. However,
the primary basis for the metals clean-up goals will
be the protection of groundwater. The selected 50 ppm
arsenic goal assumes solubility and attenuation factors
which are being verified by collecting more data.
During remedial design (RD), data to evaluate the solu-
bility of the soil contaminants and establish a site-
specific attentation factor may indicate that both the
arsenic and chromium clean-up goals need to be modified
in order to provide adequate protection of the groundwater,
A modification in the clean-up goals could result in a
change in the volume of soil requiring remediation.
The 50 ppm arsenic goal is protective of all direct
contact scenarios except new, on-site residential
development. Institutional controls are required to
prevent on-site residential development.
As stated previously, seven areas of contaminated soil
were identified at SPT (see Figure 4). The clean-up
goals indicate that four of these areas require re-
mediation. The four areas proposed for clean-up
are the Waste Sludge Pit, the Unlined Percolation Ditch
A, the Unlined Waste Disposal Pond, and the Southeast
Disposal Area.
Sampling results for three other areas indicate that
contamination levels are below clean-up goals. These
three areas are the Unlined Percolation Ditch B, the
Drainage Area, and the Southwest Disposal Area.
C. Groundwater Results
The hydrogeologic setting for the area consists of
valley-fill sequence due to the deposition of sediments
from the adjacent Sierra-Nevada highlands. The deposi-
tional environment results in discontinuous geologic
units. The exception to the discontinuous nature of the
units is a five to ten foot clay layer located at a
depth of approximately 55 to 60 feet below ground surface,,
which appears to be continuous or semicontinuous
across the site. Additional data will be collected
-------
during remedial design to verify the continuity of the
clay layer. The groundwater directly underlying the
site is an unconfined aquifer.
Three rounds of groundwater samples were conducted in
the vicinity of the SPT site. The first round of sampling
occurred in April-May 1986 and included several regional
domestic and irrigation wells, as well as five existing
EPA monitoring wells installed by the EPA Environmental
Response Team (ERT). The second round of sampling was
performed in February-March 1987. This round included
the sampling of the five existing EPA monitoring wells
and the ten newly installed plume tracking monitoring
wells. A third round of sampling occurred in July-August
1987 and included all of the monitoring wells and selected
regional wells. The analyses performed for each round
were as follows:
1. First Round, April-May 1986:
Individual phenols (Method 604)
Routine Analytical Services (RAS) Metals
General water quality parameters
2. Second Round, February-March 1987:
Individual phenols (Method 604)
RAS Metals
General water quality parameters
3. Third Round, July-August 1987:
Individual phenols (Method 604) - all wells
Dissolved chromium, arsenic, copper - all wells
Target Compound List (TCL) Volatiles - existing EPA
and plume tracking monitoring wells
TCL Semivolatiles - existing EPA and plume tracking
wells
Dioxin/furan homologs - five existing EPA monitoring
wells
While there are several contaminants at elevated levels
in the soil, chromium was the only contaminant of signi-
ficance detected in the groundwater, due to the relative
immobility of dioxin/furan, arsenic, and copper.
Organics (dioxin/furan and PCP) are being resampled as
part of remedial design .related activities, but previously
detected levels are believed to be due to sampling errors.
Sampling results indicate that a chromium contaminated
plume extends downgradient from the site to the southwest
(Figure 5). The southern boundary of this plume appears
to range approximately 1,200 feet south-southwest of
the existing wood treatment facility boundary. The
groundwater contamination is apparently confined to
-------
(ND.7.0.
Approximate
Boundary of 50 ugll
Isoc one ent ration
Contour for
Chromium
R-22
(ND.13.0,2.0 J>
R-24
(4.0.326,7. OJ)
2.0.80,5.0J)
P-4S
DATA ESTIMATED
NOT DETECTED
Project No.
123-RI1
Selma Treating Company Site
GROUNDWATER PLUME
BOUNDARY MAP
Camp Dresser & McKee Inc.
-------
the shallower portion of the aquifer (to 40'), and
does not currently affect any municipal/ private, irri-
gation, or industrial wells in the vicinity, based
on the sampling results. Contamination was not detected
in the deep monitoring wells at depths of 87-100*.
However, contamination levels in the intermediate portions
(40-60') of the aquifer have not yet been defined.
The extent of the chromium contaminated plume needs
additional definition to the west and southwest of well
R24. As part of remedial design, two well nests
west and south of R-24 are planned. A well nest will con-
sist of one shallow well (40') and one intermediate
well (601).
Additional definition of the vertical extent of contam-
ination within the groundwater plume is also planned
as part of remedial design. Three intermediate level
wells completed at depths of 60 feet will be paired
with the existing shallow wells in this .area.
Additional data will also be collected on the continuity
of the clay layer present at a depth of 55 to 60 feet.
This data will be collected during the monitoring well
installation program described above.
Other monitoring well installation plans include a
shallow monitoring well (40*) downgradient of the South-
east Disposal Area, and an intermediate level monitoring
well and two observation wells in the upgradient
background area. Other groundwater characterization
activities to be conducted as part of remedial
design include:
1. Monthly water level measurements for one year
2. Quarterly water quality sampling for one year
3. Long-term aquifer testing
4. Efforts to locate and sample the original Brown
and Caldwell monitoring wells
Based on evaluation of the data collected from the
above described activities, a decision will be made
regarding the need for any additional characterization.
D. Groundwater Cleanup Goals
The groundwater cleanup goal is the Maximum Contaminant
Level (MCL) established under both the federal and state
Safe Drinking Water Acts. Due to the fact that chromium
was the only contaminant of significance detected in the
groundwater, additive effects were not of concern. There-
fore, it was possible to select an ARAR as a clean-up
goal, rather than a risk assessment driven goal.
-------
Currently the MCL pertinent to SPT is the 50 ppb level
set for chromium. The federal MCL is proposed for
revision to 100 ppb, however, the state 50 ppb standard
will probably be in effect at the time of remedial ,
action. The most stringent of the state or federal MCL
in effect at the time of RD/RA will be used. For
analyses in the Feasibility Study and Record of Decision,
the 50 ppb MCL was assumed. The arsenic MCL of 50 ppb,
is also an applicable ARAR for the SPT site. However,
arsenic was detected only at levels well below the
existing or proposed MCL.
The boundary of the groundwater plume exceeding the
chromium clean-up goal is delineated in Figure 5. This
boundary was based on the elevated chromium values
observed in the shallow monitoring and plume tracking
wells. The western extent of contamination was estimated,
based on the observed trend of the plume in other
areas. The extent of contamination in this area will
be further defined during the RD phase, through the
installation of additional monitoring wells, as discussed
in the proceeding section.
The data collected from the deep plume tracking wells
in the site vicinity indicate that the chromium con-
tamination at a depth of 90-120 feet does not exceed
the chromium clean-up goal of 50 ppb. The exact
vertical extent of contamination that exceeds the
clean-up goal in the intermediate portions of the
aquifer will be further defined as part of the RD, as
described in the preceeding section.
V. SUMMARY OF SITE RISKS
A. Chemicals Of Concern
Data collected during the RI were reviewed to select a
subset of chemicals (chemicals of concern) for detailed
evaluation in the risk assessment. Separate subsets were
selected for surface soils, subsurface soils (soil bor-
ings), and groundwater, in order to reflect the different
exposure pathways associated with these different
media. *
A comparison of on-site and background levels of metals
in surface soils, reveals that only arsenic, chromium,
and copper appeared at elevated levels above background.
Therefore these site-related chemicals were selected as
chemicals of concern in surface soil, from among the
metals. The organics of concern in the surface soil,
identified in the risk assessment, were phenols, dioxins,
furans, bis(2-ethylhexyl) phthalate, and di-n-butylphth-
alate. An analysis of subsurface soils produces the same
subset of chemicals of concern, except that the phthalates4
-------
were not included. The levels of arsenic and dioxin/furan
contamination in the soil were the only constituents
exceeding the health based clean-up goals.
Groundwater samples were collected from domestic, indus-
trial, municipal/ and irrigation wellsf and from fifteen
monitoring wells. Site-related chemicals detected were
arsenicf chromium/ copper/ pentachlorophenol/ and two
dioxin congeners. Based on considerations of toxicity,
concentration/ and relations to site activities, arsenic,
chromium, copper, and the dioxins were selected as chem-
icals of concern. However, only chromium exceeded the
clean-up goals in groundwater.
B. Exposure Pathways
Potential human exposure pathways at the SPT site include
exposure to contaminated groundwater, exposure via direct
contact with contaminated soil (including incidental
ingestion), and inhalation of contaminated dust. Based
on data from existing private and municipal wells, risks
associated with current use of groundwater in the vicinity
of the site were evaluated. Using estimates based on .
data from monitoring wells and groundwater modeling,
potential future risks associated with use of local
groundwater as a potable supply were also evaluated. For
soil, the EA evaluated exposure of individuals working at
the site or in the vicinity of the site, local residents,
and trespassers. Direct contact (dermal absorption or
inadvertent ingestion) and inhalation were the exposure
routes used. A number of scenarios involving these types
of exposure were examined. Finally, a number of scenarios
examining the potential exposure of off-site receptors to
contaminants present in windborne dust also were evaluated
using an air dispersion model.
C. Toxicity Of Chemicals Of Concern
Both the carcinogenic and noncarcinogenic effects of
chemicals of concern used in the CA analysis are presented
below. Exposure to arsenic has been associated with an
increased incidence of cancer in humans. Chromium has
been associated with an increased incidence of lung
cancer in humans exposed via inhalation, but has not been
associated with an increased incidence of cancer when
exposure occurs via ingestion. Bis(2-ethylehexyl)phthalate
and 2,4,6 trichlorophenol are classified as probable
human carcinogens based on evidence from animal carcino-
genicity bioassays. Certain dioxins and furans are
considered to be carcinogenic by EPA and are also toxic to
the reproductive system and the immune system.
Exposure to chromium via ingestion is associated with
non-carcinogenic toxcicity, including decreased water
consumption, and at higher levels, gastrointestinal
-------
-22-
disturbances, liver damage, kidney damage, internal
hemorrage, dermatitis, and respiratory problems. Many of
these effects are thought to be due to chromium VI, not
to chromium III. Exposure to copper, chlorophenol,
cresols, di-n-butylphthalate, 2,4-dichlorophenol,
2,4-dinitrophenol, 2- and 4-nitrophenol, pentachloro-
phenol, and phenol have been associated with a variety
of systemic, noncarcinogenic effects in humans or
experimental animals.
Risk Characterization
A quantitative assessment of potential risks posed by
contaminants in the vicinity of the SPT site was performed.
The potential for endangerment of human health under a
number of current-use and future-use exposure scenarios
was evaluated. For each exposure scenario evaluated,
two exposure cases, an average and a plausible maximum
case, were considered. For the average exposure case,
mean concentrations are used together with what are
considered to be the most likely (though conservative)
exposure conditions. For the plausible maximum case,
the highest measured concentrations are used, together
with high estimates of the range of potential exposure
parameters relating to frequency and duration of exposure
and quantity of contaminated media contact.
To summarize the risk assessment, carcinogenic risks at
SPT may be associated with exposure to surface soil con-
taminants and airborne particulates under current use
scenarios. Under future use scenarios, exposure to
groundwater contamination may pose both a carcinogenic and
noncarcinogenic risk. Risk results for both the current-
use and future-use scenarios are discussed below. The
risk numbers are presented for carcinogenic risks
greater than 1 x 10~6 or where the Chronic Daily Intake
(GDI) exceeded the Reference Dose (RfD) for noncarcino-
genic risks. Generally, at SPT these risks are associated
with the plausible maximum scenario, rather than the
average case.
1. Current-use scenarios; Under current-use scenarios,
exposure of workers and residents to surface soil
contaminants in the adjacent vineyard, through
dermal adsorption and incidental ingestion, and
inhalation were considered a carcinogenic risk.
The plausible maximum risk associated primarily
with exposure to arsenic and dioxin/furans was 3 x
10~4, or the risk of three excess cancer cases dur-
ing a lifetime exposure of 10,000 individuals.
The plausible maximum cancer risk from exposure of
trespassers to surface soil contaminants at the
wood treating facility was 2 x 10~5. For workers,
the average risk was 6 x 10~6 and the plausible
-------
-23-
maximum risk was risk was 4 x 10~3. Again this
risk is associated primarily with exposure to
arsenic and dioxin/furans.
The plausible maximum risks due to inhalation of
contaminated dust are associated primarily with
exposure to arsenic and chromium. The risk ranges
from 1 x 10~5 to 5 x 10~6 for locations 250 meters
north and south of the site and 500 meters southeast
of the site.
Under current-use conditions, groundwater as a
potable supply is not expected to be a potential
health concern, since the GDI is less than the RfD.
This is based on exposure to chromium, which is a
noncarcinogen by ingestion. The reason the current-
use scenario has no risk is that no drinking water
wells are currently within the groundwater plume
boundaries. Institutional controls are needed to
ensure that no wells are drilled into the contaminated
area for drinking water purposes, until remediation
is completed.
Future-use Scenarios: Under future use conditions,
use of the shallow groundwater as a potable supply
may be a potential health concern under the plausible
maximum scenario, where the GDI levels for chromium
could be 49 times greater than the RfD.
For the deep groundwater, risk assessment based on
a mass balance model indicated that the GDIs for
several of the noncarcinogenic contaminants of
concern could exceed their corresponding RfDs under both
the average and plausible maximum scenarios. This
is due to the potential for future leaching of
contaminants, such as chromium, out of the soil
into the groundwater.
Under the mass balance model, excess cancer risks
associated with exposure to carcinogenic contaminants
(primarily background arsenic) was estimated to be 3 x
10~2. However, arsenic is not expected to be highly
mobile at SPT, based on observed levels in groundwater.
The mixing model used to derive the risk number did
not account for attenuation of contaminants in the
environment and represents a very conservative estimate
of the potential future risk associated with groundwater
use. Because of this, arsenic was not retained as a
chemical of concern in the formulation of groundwater
remediation alternatives in the FS.
Under future use scenarios, direct contact with soil
contaminants or inhalation of contaminated particulates
-------
-24-
over relatively short periods of time by on-site
construction workers, are not expected to be a
potential health concern. This is the case for
exposed individuals under either average or plausible
maximum cases.
E. Analytical Methods Used
The Bndangerment Assessment for the SPT site generally
followed the guidelines established by EPA for risk
assessments under CERCLA (EPA 1985a, 1986a) and for
health risk assessments in general (EPA 1986b,c,d).
The purpose of the assessment was to evaluate the No
Action Alternative. The assessment was based on data
generated under the EPA contract laboratory program
(CLP).
VI. DOCUMENTATION OF SIGNIFICANT CHANGES, Section 117(b)&(c)
Of CERCLA
The preferred alternative in the Proposed Plan is the same
as the remedy selected in this ROD: Soil fixation with a
RCRA cap and conventional groundwater treatment. No signif-
icant changes are proposed at this time. Additional data
collection activities that will occur as part of remedial
design could impact information contained in the ROD.
VII. DESCRIPTION OF ALTERNATIVES
A. Alternative 1 - No Action
This alternative involves taking no action to treat/
contain, or remove the contaminated groundwater and soil.
Multi-media monitoring would be performed every five
years to support a reassessment of the No Action Alterna-
tive. The costs for this alternative are as follows:
Capital cost $18,000
Operation and maintenance (O&M) cost (annual) $22,000
Present worth (life of project at 8% dis-
count and 4% inflation rates) $90,000
B. Alternative 2 - RCRA Cap with Slurry Wall
Alternative 2 is a containment alternative. The function
of the multi-layer RCRA Cap is to prevent direct contact
with soil by humans and wildlife, and to minimize the
potential for airborne contamination. In addition, the
low permeability Cap reduces infiltration and leaching
of contaminants from the soil into the groundwater. The
Cap would be constructed over the areas of contam-
inated soil that exceed the cleanup goals. Approximately
33,300 square feet of Cap would be required to cover
these areas, based on the current clean-up goals.
The Cap would meet the RCRA closure requirements under
-------
-25-
40 C.F.R. §264, Subparts F, G and N. An example of Cap
construction according to EPA closure guidance would
be: -
1. A 2 foot clay layer with hydraulic conductivity
no greater than 1 x 10~7 cm/sec.
2. A minimum 20 mil High Density Polyethylene (HOPE)
geomembrane.
3. A one-foot sand layer with a hydraulic conductivity
of 1 x 10~3 cm/sec and filter fabric.
4. A two foot top soil layer.
Capping does not eliminate the leaching of contaminants
from the untreated waste left on-site. Fluctuating
groundwater levels may cause groundwater contact with
contaminated soils. This may result in additional
contamination at levels above the MCL, particularly for
chromium.
The groundwater component of this alternative is to
install a slurry wall to isolate the contaminated
groundwater from the uncontaminated portion of the
aquifer. A 1,375 foot long wall would be keyed into a
clay layer at a depth of 55 feet. Approximately 75
million gallons of contaminaated groundwater is estimated
to need containment. Extraction wells would be placed
inside the slurry wall to maintain the hydraulic gradient
toward the contaminated groundwater being contained.
Monitoring wells would be located downgradient and
outside the slurry wall in order to evaluate the
effectiveness of the wall over time. The risks of
leaving contaminated groundwater in the aquifer would
be potential exposure of users to water that does not
meet the drinking water standards. Therefore, institu-
tional controls to prevent such use are required.
The major limitation associated with the slurry wall
is that the clay layer proposed for its base may not
be thick or continuous enough to support the wall.
Additional investigation of this clay layer would be
needed to support this alternative.
The aquifer in the Selma area is currently classified
under EPA's Groundwater Protection Strategy, as a Class
II A aquifer, which is currently used for drinking
water and other beneficial uses. Also, the Fresno area
has a designated Sole Source Aquifer under the Safe
Drinking Water Act, 42 U.S.C. §1424(e). Alternative 2
would not be consistent with protection of this groundwater
resource, due to the continued exceedences of the MCL
for chromium and the potential for continued leaching
of chromium or other constituents from the soil.
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-26-
Under Alternative 2, implementation requirements include
obtaining permission for use of private property during
Cap and slurry wall construction. The slurry wall
would require permanent easements or private property
acquisition along its alignment. Off-site treatment and
disposal options for the extracted groundwater would need
to be evaluated.
Long-term institutional controls would be implemented
to prevent access by unathorized persons to the capped
areas, including fencing/ signs and other land use
restrictions. Long-term access to capped areas, extraction
wells, and monitoring wells would be needed by government
officials or representatives to ensure O&M activities
could occur. Finally, long-term institutional controls
would be needed to prevent the use of the contaminated
portions of the aquifer as a drinking water supply.
The implementation tiraeframe for Alternative 2 would be
approximately two months for RCRA Cap construction
and seven months for slurry wall construction, after
property access agreements have been obtained.
Costs for Alternative 2 are as follows:
Capital: $2,180,000
O&M: $40,000
Present worth: $2,390,000
C. Alternative 3 - Soil Fixation with a RCRA Cap and
Conventional Groundwater Treatment
For soils, Alternative 3 has both treatment and contain-
ment components. The function of soil fixation, as
treatment, is to create a monolithic soil matrix which
inhibits leaching, using a stabilization and solidifi-
cation process. The RCRA Cap, placed on top of the
fixed soils would provide additional protection from
surface disturbance and surface water infiltration. The
waste to be treated is contained in the areas where the
soil constituents exceed cleanup goals. Also, under
this alternative, six dry wells will be evaluated and
abandoned, as appropriate.
The arsenic and chromium contamination is considered a
RCRA characteristic waste under 40 C.F.R. §261.24. The
dioxin and PCP waste is considered a RCRA K001 listed
waste under 40 C.F.R. §261.32. Once excavated, substantive
RCRA standards for treatment, storage and disposal of
these wastes under 40 C.F.R. §264 apply. In addition,
disposal of K001 waste is regulated under 40 C.F.R.
§268, Land Disposal Restrictions, since placement has
occurred. The volume of contaminated soils requiring
treatment total approximately 16,100 cubic yards of
-------
material. Volume estimates will be further refined
during remedial design/ and should be considered
estimates here.
The typical on-site fixation operation includes a batch
plant for mixing the fixative agent (cement, silicate
materials/ and additives), and conventional construction
equipment for excavating and backfilling the soil. The
batch plant and staging area for temporary storage of
contaminated soils is proposed for a 1.5 acre area in
the northwest corner of the SPT site. The staging area
will comply with RCRA regulations under 40 C.F.R. §264/
Subpart L - Waste Piles/ calling for temporary double
synthetic liners and a double leachate collection
system. The temporary waste and storage facilities
will also need to comply with the construction standards
for Class I waste piles in Title 23, Subchapter 15,
California Code of Regulations (CCR). Cap construction
will be as outlined for Alternative 2/ and will meet
the same RCRA applicable or relevant and appropriate
requirements (ARARS).
The fixed soil will meet the leachablity requirements
for the appropriate site-specific constituents under
RCRA. The maximum concentration of arsenic and chromium
characteristic wastes, using EP toxicity, is 5 mg/1
under 40 C.F.R. §261.24. It is predicted that fixation
will meet land disposal restriction level under 40
C.F.R. §268, of 37 ppm for PCP, using a total waste
analysis test.
Also, as discussed previously, soils will be tested
during remedial design to determine the soluble fraction
of the contaminants and the attenuation factor. Based
on this testing, treatment goals needed to protect ground-
water will be evaluated by EPA and the RWQCB. The
RWQCB recommends site-specific cleanup goals under the
authority of the Porter Cologne Water Quality Control
Act California Water Code §§13000 et seq.
Under Alternative 3, residual levels of arsenic, dioxin/
furan, chromium, copper, and phenols below the health
risk-based cleanup goals would remain onsite, untreated.
Based on the Endangerment Assessment for SPT it was
determined that these residuals will not pose an unacceptable
risk to public health or the environment. The solubility
testing will ensure that residual levels do not pose a
risk to groundwater.
There is a potential for the future breakdown of the
monolithic soil matrix. To reduce this potential the
fixed soils will be covered with a Cap that meets the
RCRA requirements as described under Alternative 2.
Long-term monitoring will also be performed to meet the
substantive RCRA requirements for closure under 40
C.F.R. §264, Subpart F, G and N.
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For the groundwater component of Alternative 3, a
conventional precipitation, coagulation, and floccu-
lation process is proposed to remove chromium to the
MCL level. Based on the assumption of a 50 ug/1 MCL
and a two dimensional model, the volume of extracted
groundwater requiring treatment is estimated at 2.7
billion gallons. This estimate will be further defined
during the remedial design phase of the project, based
on additional aquifer testing and monitoring well
installation.
Based on the estimate discussed above and the distribu-
tion of the plume, approximately 25, 6-inch diameter
extraction wells, 50 feet deep will be pumped at a
cumulative total of 1,040 gallons per minute for five
years. This assumes a treatment plant operating 24
hours a day, seven days a week, with an online availablity
of approximately 95%. The five year timeframe is based
on several assumptions regarding estimates of extent of
contamination, the number of extraction and injection
wells, and the volume of groundwater requiring treatment.
Specific timeframes will be further defined as part of
RD. A range of 5-10 years may be more realistic,
depending on the results of data collected during RD.
The treatment facility will consist of an influent
storage tank, a rapid mix unit, a slow mix unit, a sedi-
mentation tank, a filter, a treated effluent storage
area, and associated piping, valves, and pumps. This
facility proposed for location in the vineyard south of
the wood treating facility, will occupy approximately
1/2 acre.
Based on satisfactory treatment and testing of the ground-
water, either reinjection or off-site disposal will occur.
If reinjection is appropriate, approximately 35, 4-inch
diameter recharge wells will also be distributed throughout
the aquifer.
The treatment level to be achieved is the more stringent
of the federal or state Safe Drinking Water Act Maximum
Contaminant Levels. Currently this level is 50 ppb,
under both federal and state law. .Residual untreated
groundwater would not exceed the MCL. Residual treated
groundwater would either be reinjected or disposed of
off-site. For reinjection, substantive requirements of
the Safe Drinking Water Act 42 U.S.C. §§1421-1422,
40 C.F.R. §§144-147, would be met. For off-site disposal,
the RWQCB would establish discharge limits consistent
with requirements under the National Pollutant Discharge
Elimination System (NPDES) program. The reinjection
of treated groundwater will also be regulated by substantive
RWQCB waste discharge requirements to provide protection
of the beneficial uses of the underlying groundwater.
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The sludge generated from the treatment facility will
be dried in lagoons on two acres adjacent to the treatment
facility. The sludge will be disposed of at an approved
off-site RCRA facility or municipal landfill, depending
on sampling results. The sludge lagoons will be con-
structed to RCRA standards as set forth in 40 C.F.R. §264 -
Subpart K - Surface Impoundments, which require two or
more liners and a leachate collection system. Synthetic
liners are proposed for use at SPT. The sludge lagoons
will also need to meet the construction criteria in
Title 23, Subchapter 15 of the CCR, regulated by the
RWQCB. Other options, for sludge drying, such as
mechanical methods, will be considered during the
design phase.
Regarding implementation requirements for soil remediation
activities under Alternative 3, equipment and materials
for Cap construction are readily available. Treatability
testing is required for soil fixation, and is currently
being performed. There are numerous commercial enterprises
involved in developing and marketing fixation technology.
Sixteen companies were identified in a vendor survey as
capable of providing expertise in treating metals and
organics with solidification and stabilization processes.
Access to private property will be needed for the batch
plant and staging areas.
Short-term worker protection during soil excavation
will be required, consistent with federal and California
Occupational Safety and Health Act (OSHA and Cal OSHA)
standards. EPA currently has federal-lead jurisdication
for worker protection at wood treating facilities.
.However, EPA has adopted OSHA standards for use at
these sites. Excavation, storage, and fixation of soil
are also subject to Fresno Air Pollution Control District
(APCD) Rules 210.1, 404, 405, and 418. Discharges
during remediation could include: (1) fugitive dust con-
taining toxic metals and toxic organics, and (2) volatile
toxic organics. Requirements of the Clean Air Act, 42
U.S.C. §7401 et seq, are incorporated into APCD Rules,
per Section 110 of the Clean Air Act.
For the groundwater component, implementation requirements
include disposal of treatment residuals, utility require-
ments, access to private property for the treatment
plant and sludge lagoons, treatability studies for waste
stream characteristics, and disposal of treated water.
Significant implementation obstacles are not foreseen.
The main uncertainty regarding Alternative 3 is the
implementability of soil fixation based on treatability
testing. If this test is not successful, it will be
necessary to select a different alternative to remediate
SPT site soils.
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The groundwater classification is Class II A, and
implementation of Alternative 3 would be consistent
with maintaining the use of the aquifer for drinking
water and other purposes.
Short-term institutional controls include limiting
access to the staging area, treatment areas, and sludge
drying beds, through use of fencing, signs and security.
Until remediation of groundwater is achieved, institu-
tional controls over the use of the contaminated portions
of the aquifer will be required. Long-term institutional
controls include access restrictions to capped and
fixed areas, and long-term access for monitoring and
maintenance activities.
The implementation timeframe for Alternative 3 is
approximately 12-18 months for the soil component and
5-10 years for groundwater treatment.
Costs associated with Alternative 3 are estimated as
follows:
Capital: $ 6,500,000
O&M: $ 1,300,000
Present Worth: $11,280,000
D. Alternative 4 - On-site Rotary Kiln with Off-site
Disposal and Conventional Groundwater Treatment
This alternative has both treatment and containment
(disposal) components. The groundwater components are
the same as described in Alternative 3 and will not be
discussed further here. The soil treatment component
applies to the organic constituents in the soil. An
on-site rotary kiln would be used to incinerate dioxin/
furan and pentachlorophenol wastes totalling 7800 cubic
yards. Included with the organic wastes are metal
constituents that would not be destroyed during inciner-
ation. In addition, there is another 8300 cubic yards
of metals contaminated soil with no organic contamination.
All of the soils, treated and untreated (a total of
16,100 cubic yards), would be disposed of at an off-site
RCRA facility. The SPT wastes containing pentachlorophenol
would require treatment (e.g., incineration) prior to
disposal to meet the present RCRA Best Demonstrated
Available Technology (BOAT) requirements of 37 ppm,
under 40 C.F.R. §268. The untreated arsenic and chromium
contaminated wastes are RCRA characteristic wastes and
therefore require disposal at an approved RCRA Class I
facility.
The mobile unit assumed for SPT is rated at 15 million
BTU/hour and treats 4.50 tons/hour of dry solids.
The primary (i.e., rotary kiln) and secondary (i.e.,
afterburner) combustion chambers are generally mounted
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on concrete slabs. Approximately .5 acres is expected
to be required for stockpiling excavated soil, locating
feed handling and preparation equipment, and temporary
storage of decontaminated soil. Sufficient area for
processing exists on the storage yard being used by
the present wood treating operation.
For organics, treatment levels achieved would be the
BOAT treatment level requirements for PCP of 37 ppm
and the 1 ppb clean-up goal for dioxin/furan contamination.
For the incinerator, 99.99% destruction and removal
efficiency (DRE) is required under 40 C.F.R. §264,
Subpart O, for the principal organic hazardous constituents
(POHCs). The metals would remain untreated, and would
either be captured in the air pollution control equipment
or remain in the incinerated soil residuals.
If BOAT for metals under 40 C.F.R. §268 is in effect at
the time of project implementation, then these levels
would need to be met as well. For this ROD it is
assumed that the incinerator soil residuals would
require disposal at a RCRA Class I facility due to the
metals content of the residue.
Under the California Air Resources Act, California
Health and Safety Code §39650 et seq, the Air Pollution
Control District (APCD) will set emission limits for
discharges associated with use of the incinerator under
APCD Rule 210.1, New Source Review. Rules 404, 405, 418
and 417 also apply to excavation and incinerator activ-
ities. Discharges associated with soil excavation may
consist of: (1) fugitive dust containing toxic metals
and/or toxic organics, and (2) volatile toxic organics.
Compliance with APCD Rules includes Clean Air Act
requirements.
Implementation requirements include access to a mobile
rotary kiln, of which there may be a limited supply.
Acceptance of SPT wastes at an off-site RCRA facility
would be determined based on waste characteristics and
BDAT requirements in effect at the time of waste disposal.
Access to private property is required for the inciner-
ator, groundwater treatment systems, and monitoring
well installation activities. Pilot work would be
necessary to aid in addressing materials handling
requirements and to assess air emissions.
Alternative 4 would be consistent with the area's Class
II A aquifer classification. The contaminated groundwater
would be treated and contaminated soils would be removed.
The removal of the contaminated soil would prevent the
possibility of continuing migration of the contaminants
to the groundwater. As stated previously, soil clean-up
goals will be evaluated after solubility testing to
ensure protection of groundwater quality.
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Institutional controls include short-term access restric-
tions to the soil and groundwater treatment areas, and
restrictions over the use of the contaminated portions
of the aquifer for drinking water purposes. Long-term
institutional controls are not needed for this alternative,
The soils remediation implementation timeframe for
Alternative 4 would be 7-10 months at an incinerator
unit operating 24 hours a day, seven days a week, with
online availability of 80%. An additional 1-2 months
would be required to demobilize equipment. Groundwater
treatment is estimated to take 5-10 years.
Costs estimated for Alternative 4 include:
Capital: $15,630,000
O&M: $1,290,000
Present worth: $20,360,000
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
A. Overall Protection of Human Health and the Environment
1. No Action; No protection is provided, although
monitoring would provide a warning indicator of
contaminant transport.
2. RCRA Cap with Slurry Wall; Partial protection is
provided, with ongoing maintenance. The migration
of contaminated groundwater is restricted from
reaching uncontaminated portions of the aquifer.
Direct contact with soils and generation of contam-
inated airborne dust is prevented. The Cap also
limits infiltration of surface water and contaminant
mobility. Institutional controls are necessary to
prevent the use of contaminated groundwater exceeding
primary drinking water standards. Continued leaching
of capped soils due to groundwater fluctuations
could exacerbate the chromium contamination problem.
3. Soil Fixation with RCRA Cap and Conventional Ground-
water Treatment; For soil, protection is provided
with ongoing maintenance. Cap protection features
are the same as for Alternative 2. Addition of the
fixative agent greatly reduces continued leaching
of contaminants to groundwater, protecting potable
water supplies from a continuing source of contamina-
tion. Groundwater treatment provides complete
protection to the MCL cleanup level.
4. On-site Rotary Kiln and Off-site Disposal with
Conventional Groundwater Treatment; For soil,
complete protection is provided on-site. No contam-
inants exceeding the cleanup goals remain at SPT.
Careful short-term incinerator operation would be
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required to assure that significant adverse air
quality impacts do not occur. For groundwater, the
same complete level of protection is provided as
for Alternative 3.
B. Compliance with ARARS
1. Alternative It Does not comply with MCLs for ground-
water. No action would be taken to meet ARARS.
2. Alternative 2; Does not comply with MCL for chromium
or Porter Cologne Water Quality Act cleanup goals
for soils (a requirement "to be considered," rather
than an ARAR). Would comply with RCRA requirements
under 40 C.F.R. §264, Subparts F, G, and N.
3. Alternative 3t Will comply with all ARARS, including
MCLs, RCRA BOAT for K001 listed waste, and RCRA
closure requirements.
4. Alternative 4; Would comply with all ARARS identified
at this stage, including MCLs, RCRA BOAT for K001
listed waste, and RCRA requirements for off-site dis-
posal of waste.
C. Long-term Effectiveness and Permanence
1. Alternative 1; Not a permanent solution.
2. Alternative 2; Not a permanent solution. Long-term
monitoring and maintenance activities are associated
with the Cap. Groundwater is not treated. Long-
term institutional controls would be required to
ensure that drinking water wells are not located in
the contaminated portions of the aquifer.
3. Alternative 3; For soil, full permanence cannot be
assured due to limited experience with the fixation
technology. Long-term maintenance and monitoring
is required. Depending on the monitoring results,
additional work could be required in the future if
the monolithic soil matrix breaks down. For ground-
water, a permanent solution.
4. Alternative 4: For soil, a permanent solution for
organics (dioxin/furans and PCP); but not permanent
for metals. Off-site disposal requires long-term
O&M at the RCRA facility. For groundwater, a
permanent solution.
D. Reduction in Toxicity, Mobility and Volume (TMV)
1. Alternative 1; Does not reduce TMV.
2. Alternative 2: Reduces mobility but not toxicity or
volume.
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3. Alternative 3; For soil, mobility significantly
reduced, toxicity is not reduced, and volume is in-
creased due to the addition of the fixative agent.
For groundwater, TMV reduced.
4. Alternative 4; For soil, near complete reduction of
toxicity and mobility for organics. For metals,
reduces mobility only by removing contaminants from
the site and containing them in a Class I RCRA facil-
ity. For groundwater, TMV reduced.
E. Short-term Effectiveness
1. Alternative 1: There would be no short-term impacts.
2. Alternative 2; Short-term impacts to workers
associated with slurry wall and Cap construction
would be minimal.
3. Alternative 3; Short-term exposure to workers during
soil excavation and treatment, and groundwater well
installation could occur. Worker safety precau-
tions and dust suppression needed to protect workers
and others onsite and in site vicinity.
4. Alternative 4; Short-terra impacts would be comparable
to Alternative 3. Differences include short-term
potential for accidental spillage during off-site
transport of wastes and exposure to incinerator
emissions. Air pollution control equipment and
careful transport required in addition to measures
outlined in item 3, above.
F. Implementability
1. Alternative 1: No implementability factors are
relevant.
2. Alternative 2: The technology for both the RCRA Cap
and slurry wall are readily available. The technical
feasibility of the slurry wall is questionable due
to potential problems with inadequate thickness and
continuity of the clay layer. Access problems assoc-
iated with the slurry wall alignment may also arise.
3. Alternative 3; The RCRA Cap and conventional ground-
water treatment technologies are readily available
and proven. Property access/acquisition problems
may arise for the well installation and treatment
areas. Fixation technology requires site-specific
treatability testing to verify effectiveness prior
to use.
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4. Alternative 4; Conventional groundwater treatment
issues are the same as under Alternative 3, above.
Use of incinerator requires prior on-site treat-
ability testing in coordination with the local
APCD. Off-site disposal of wastes requires acceptance
by the receiving facility depending on actual waste
characteristics analysis. Regulatory status governing
off-site disposal of land ban wastes may influence
disposal options at time of remedial action.
G. Estimated Capital, O&M, and Present Worth Cost
CAPITAL
O&M
PRESENT WORTH
Alt 1 No Action
Alt 2 Slurry Wall/
RCRA Cap
Alt 3 GW Treatment/
Fixation
Alt 4 GW Treatment/
Rotary-Kiln/
Off-Site Disposal
$18,000
2,180,000
6,500,000
15,630,000
22,000
40,000
1,300,000
1,290,000
90,000
2,390,000
11,280,000
20,360,000
H. State and Community Acceptance
1. Alternative It Not acceptable to the state; no
input was received from the community.
2. Alternative 2; Not acceptable to the state due to
potential insufficiency of clay layer to key slurry
wall into and because chromium remaining in soils
under the Cap could leach to groundwater. No
community input received.
3. Alternative 3r Acceptable to the state. Additional
remedial design-related groundwater and soil sampling
and treatability testing will be reviewed by the state
for continued acceptance of remedy. No community
comments received.
4. Alternative 4; State concerned about potential
incinerator emissions-related public perception and
regulatory approval problems. Incinerator pilot
testing and remedial design-related sampling results
would be reviewed by the state. No community
issues raised at this time.
IX. THE SELECTED REMEDY
Alternative 3 - Conventional Water Treatment and Soil Fixation
with a RCRA Cap, has been selected as the remedy for the
SPT site. Remediation of the chromium contaminated groundwater
under this alternative consists of pumping the groundwater
from the aquifer, treating it in an on-site facility utilizing
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a conventional water treatment method/ and disposing of the
treated effluent through reinjection into the aquifer, or
off-site, as appropriate.
The soil remediation component of this alternative consists of
excavating the contaminated soil, transporting it to a pro-
cessing plant onsite; "fixing" the soil with cement, silicate
and other bonding agents; and then backfilling and compacting
the fixed material on-site. Fixed areas of soil will then be
covered with a RCRA Cap.
X. THE STATUTORY DETERMINATIONS
A. Protection of Human Health and the Environment
The selected remedy will eliminate risk of exposure to
groundwater contaminated with chromium above MCL levels.
The remedy will eliminate exposure to contaminated soil
that exceeds groundwater and health based cleanup
goals. In the case of soils, the contaminants will not
be removed or destroyed. Long term O&M is required to
ensure that the soil remedy is effective.
Adequate safety precautions will be used during construc-
tion and treatment activities. Therefore, unacceptable
short-term impacts are not expected. Cross media
impacts are also not foreseen associated with this
remedy. Careful attention to drilling techniques will
be paid to ensure that drilling will not contaminate
the deeper, unaffected portions of the aquifer. Cleanup
goals will take into account the potential leaching of
soil contaminants into the groundwater. Careful dust
suppression methods during all remedial activities will
ensure that contaminants are not transmitted into the
air at unacceptable levels during construction. The
RCRA Cap will provide long-term protection agaist trans-
mission of contaminated particulates into the air.
B. Attainment of ARARS
The selected remedy will attain the applicable or relevant
and appropriate requirements determined to date; no
ARARS waiver is necessary. The following are the main
ARARS that have been determined to apply to the remedy:
Statute
Safe Drinking Water Act
42 U.S.C. §300A e_t seq;
40 C.F.R Part 141.
Safe Drinking Water Act
42 O.S.C. §300A et seq;
40 C.F.R. Parts 144-147,
Standard
Maximum contaminant levels
for chromium and arsenic
in groundwater.
Underground injection
control requirements for
Class V Wells, including
dry wells.
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Safe Drinking Water Act
42 U.S.C. §1424(e).
Resource Conservation
and Recovery Act
42 U.S.C. §6901 e_t seq;
40 C.F.R. Parts 257, 261,
262, 263, 264, 265, 268.
California Safe Drinking
Water and Toxic Enforcement
Act. California Health and
Safety Code §252.5 et seq.
California Air Resources
Act. California Health and
Safety Code §39650 et seq.
Porter Cologne Water
Quality Control Act.
California Water Code
§13000 et seq.
California "Superfund"
Law - Hazardous
Substances Account Act/
Hazardous Substances
Cleanup Bond Act.
California Health and Safety
Code §25300 et seq.
California Occupational
Safety and Health Act.
California Laboratory
Code §6300 et seq.
Occupational Safety and
Health Act. 29 U.S.C.
§651 et seq.
C. Cost-Effectiveness
Prohibits any project with
federal financial assistance
from contaminating a Sole
Source Aquifer.
Practices to be followed by
generators, transporters,
owners and operators of
hazardous waste. Standards
for land disposal of certain
restricted hazardous wastes.
The state MCL for
chromium.
Discharge limits for
activities conducted
during the remedial
action. Includes Clean
Air Act requirements.
Waste discharge requirements,
NPDES discharges, specific
cleanup standards estab-
lished on a site specific
basis.
Substantive requirements
of a Remedial Action Plan
(RAP).
Standards for worker
protection during remed-
iation.
Under 40 C.F.R. §300.38,
OHSA requirements apply to
all activities conducted
under the NCP.
The selected remedy estimated at $11,280,000 is the
least expensive of the remedies that meet the statutory
criteria of protection of public health and the environ-
ment, and attainment of ARARS. For example, alternative
4, Conventional Water Treatment/Incineration and Off-site
Disposal is estimated at $20,360,000; almost double the
selected remedy. Alternative 2, slurry wall/RCRA Cap,
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is much less costly than the selected remedy at an esti-
mated $2,390/000; but would not be protective of public
health or meet ARARs.
D. Utilization of Permanent Solutions Employing Alternative
Technologies to the Maximum Extent Practicable (MEP)
The selected remedy is an appropriate solution for the
site. It will effectively treat groundwater contaminants/
prevent contact with soil contaminants, and prevent leach-
ing of contaminants to the groundwater at levels above
the MCL. The remedy provides protection of public
health, achieves ARARS compliance and is cost-effective.
In comparison, on-site and off-site RCRA disposal options
are more problematic for soils at SPT than the chosen
method of fixation. An on-site RCRA landfill would not
meet RCRA or CCR siting criteria due to the site geology
and presence of a Sole Source Aquifer. Since BOAT was
not established for the dioxin K001 waste, it could con-
ceivably be disposed of off-site, along with the metal
contamination, without treatment. The PCP wastes would
require treatment to the 37 ppm BDAT standard. However,
straight off-site disposal of wastes does not comply
with the intent of CERCLA for remedies that use permanent
solutions and treatment to the maximum extent practicable.
Finally, the regulatory status governing land disposal
of SPT waste is in a state of development. It is not
certain whether RCRA disposal facilities would accept
SPT wastes at the time of remediation; and if so, what
Best Demonstrated Available Technology (BDAT) would be
required (BDAT may be promulgated for arsenic).
In regard to soil treatment methods, fixation and inciner-
ation were the only two that were deemed technically
feasible in the FS screening process. Incineration,
however, treats only the organic contents of the SPT
waste, resulting in untreated metals requiring disposal.
Fixation has been identified as a feasible technology
for the low organic/high metals ratio in the SPT wastes.
(Treatability testing will be performed to ensure that
this method will effectively treat SPT wastes). The
sandy-silty soil composition at SPT is also amenable to
fixation.
Several nonthermal treatment process for removing soil
contaminants at SPT were examined, including physical,
chemical, and biological. Of the physical methods, (fix-
ation and soil washing), soil washing was found not to
be effective for removing the relatively low arsenic and
chromium concentrations in the waste, and is not an
effective remedy for organic wastes. For chemical methods,
nucleophilic substitution, or KPEG, only applies to the
organics and has not been demonstrated effective in removing
the dioxin/furan concentrations to the 1 ppb level.
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Biological treatment processes, both on-site and in-situ,
were examined for soil treatment. Biological treatment
applies only to the organic contaminants in the waste, and
does not treat the metals. However/ laboratory tests did
not show reduction of dioxins to the 1 ppb level and no
large scale pilot studies have been conducted on use of
biodegradation for dioxin wastes.
For groundwater treatment, the metals-precipitation
chromium removal technology selected for groundwater
cleanup is a conventional and effective method commonly
used in industrial processes. The other groundwater
treatment method evaluated in detail was ion exchange.
However, ion exchange processes would not be effective
in treating site groundwater due to the potential for
clogging of the resins. Clogging occurs as the trivalent
chromium in the water will readily precipitate out of
solution as chromium hydroxide. In addition, large
quantities of brine are generated, increasing costs over
conventional treatment without greater protection.
Therefore, in comparison to other possible technologies,
soil fixation with a RCRA Cap and conventional groundwater
treatment have been determined to be the most appropriate
technologies for the SPT site.
For groundwater, the remedy selected is considered the
maximum extent to which a permanent solution and treatment
can be practicably utilized. For soil, full permanence
cannot be assured due to limited experience with the
fixation technology. Therefore, long-term monitoring is
required. In terms of treatment, the contaminants are
rendered immobile by application of the fixative agent.
However, this form of treatment does not reduce contaminant
volume or significantly reduce toxicity.
A fully permanent treatment solution for the combination
of wastes present in the SPT soil was not determined to
be feasible at this time. Therefore, the selected remedy
represents the maximum extent to which permanent solutions
and treatment can be practicably utilized.
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RESPONSIVENESS SUMMARY
FOR TOR
FEASIBILITY STUDY
SELMA PRESSURE TREATING COMPANY
INTRCOOCTIGN
From June 3, 1988 through July 2, 1988, the U.S. Environmental Protection
Agency (EPA) held a public comment period on EPA's draft Feasibility Study
(FS) for the Selma Pressure Treating Company Superfund Site in Selma,
California. The PS evaluates four alternatives for addressing soil and
groundwater contamination. The purpose of the public comment period was to
give interested parties the opportunity to comment on the FS. For this
purpose, EPA held a community meeting in Selma on June 22, 1988.
EPA's purpose in conducting the FS was to evaluate relevant remedial action
alternatives for selecting a remedy that is protective of human health and
the environment for the soil and groundwater contamination identified at
the site. The selected remedy also must attain Federal and State
requirements that are applicable or relevant and appropriate, and be cost
effective.
A responsiveness summary is required under EPA Superfund policy guidelines
for the purpose of providing a summary of the issues of concern raised
during the public comment period about the remedial alternatives contained
in the FS. In addition to summarizing the concerns and questions raised by
interested parties, the responsiveness summary presents EPA's responses to
those concerns.
The responsiveness summary for the FS conducted at the Selma Pressure
Treating Company site is divided into three sections:
I. Background on Community Involvement and Concerns. This
section provides a brief history of community interest in and
concerns about the Selma Pressure Treating Company site.
123.17:5
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II. Overview of the FS. This section provides a brief history of
the soil and groundwater contamination, summarizes the
contents of the draft FS, and identifies EPA's preferred
alternative.
III. Summary of Comments Received and EPA Responses. This section
categorizes and summarizes written and oral comments received
during the public comment period and provides EPA's responses
to these comments.
Appendix A contains an index of comments received during the formal comment
period, as well as a copy of these comments. These comments include issues
raised at the public hearing and all written comments received by EPA
during the public comment period on- the FS.
I. BACKGROUND ON COMMUNITY INVOLVEMENT AND CONCERNS
This section presents a summary of community awareness about the site,
community concerns expressed at the recent community meeting about the
site, media coverage of site activities, and EPA community relations
activities conducted to date.
A. History Of Community Awareness About The Site
General community awareness and concern about the Selma Pressure Treating
Company (SPT) site first surfaced when two local newspapers focused media
attention on groundwater contamination from the site. The Selma Enterprise
and the Fresno Bee published articles about EPA's preliminary site
investigation in early 1982 and the results of Selma Leasing Company's
geotechnical study of the site in mid-1983. When Regional Water Quality
Control Board (RWQCB) officials announced that the geotechnical study
indicated that the plume of contamination was moving in a southwesterly
direction, towards agricultural land and away from the City of Selma,
general community interest in the groundwater contamination issue subsided.
Complaints about air and groundwater quality problems from at least three
immediate neighbors of the site property began in 1981 and were directed to
officials of the Fresno County Health Department (FCHD), RWQCB, and the
123.17:5
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California Air Quality Management District. One resident indicated that he
had complained to the Selma City Manager and had been referred to County
Health officials, because the site is located outside Selna city limits.
Another resident attended a Fresno County Resources and Development
Department (FCRDD) hearing on a Conditional Use Permit for the site
property in November 1983 and expressed concern that operating the wood
treatment plant would result in additional soil and groundwater
contamination. FCRDD officials responded that the permit required the
operators to adhere to environmental controls that mitigated the threat of
additional contamination.
An Uncontrolled Hazardous Waste Site Investigation was conducted by EPA
DHS, and RWQCB in January 1981. In August of 1983, EPA ranked the site
using the Hazardous Ranking System, (HRS) to determine whether to include
the site on the Superfund-National Priorities List of hazardous waste
sites. The HRS ranking for the site was 48.83, indicating that releases of
hazardous substances from the site may present an endangerment to the human
health and welfare or the environment. Based on this information, the site
was listed as 195 on the Superfund National Priorites List in September
1983.
Considerable concern about area groundwater contamination was expressed by
the General Manager of the California Water Company (CWC) to EPA at the
time of EPA's preliminary site investigation. CWC, a private company
supplying water to the City of Selma, has two relatively shallow wells
located within one-half mile to the northwest of the site. When the
geotechnical investigation revealed the extent of the contamination
problem, CWC began to monitor its wells regularly for heavy metals and
organic compounds. To date, however, no contamination of its wells from
the SPT site has been detected. The General Manager received several calls
prior to 1986 from residents in the vicinity of the site expressing concern
about contamination of their private wells. The General Manager explained
to residents that tests of CWC's water indicated that no contamination was
present, and suggested they call the California Department of Health
Services (DHS) or have their well water tested by a private laboratory if
they were concerned about well water quality.
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In July 1985, EPA held a community meeting to discuss EPA's plans to
perform a Remedial Investigation (RI) and Feasibility Study (FS) at the
site. Approximately 50 residents from Selroa and other parts of Fresno
County attended the meeting. Several newspaper and television reporters
also attended. A number of the residents expressed concern at the meeting
that no action was being taken at the site to correct contamination
problems. Several individuals suggested that air emissions from the wood
treating operations may pose a health hazard to plant workers and nearby
residents. Others were concerned about local groundwater contamination
beyond the SPT boundaries. EPA indicated that 25 wells within one mile of
the site would be sampled during the RI as a part of the effort to
determine the nature and extent of contamination.
B. Community Concerns From The June 22, 1988 Public Meeting
All of the community concerns related to groundwater contamination found at
the SPT site are influenced by the area's dependence on groundwater
resources, which are used for drinking and agricultural purposes. The
major concerns, as expressed at the June 22, 1988 community meeting on the
draft FS, were as follows.
Groundwater Contaminant Migration and Potential Well Impacts
Several meeting attendees raised questions during the June 22, 1988
community meeting about the groundwater contaminant plume migration.
Questions were raised regarding rate of plume movement, depth of plume and
whether additional monitoring of the lateral and vertical extent of
contamination was planned. Other questions focused on relation of the
plume to the city limits, whether any private wells were located within the
plume and whether continuous monitoring of private wells would occur.
Finally, a questioner asked about what the impacts would be to the water
table if the deeper agricultural wells were contaminated.
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c.
Media Coverage Of Site Activities
Media coverage of SPT site activities has come primarily from two local
newspapers, the Selma Enterprise and the Fresno Bee. Media coverage began
in early 1982 when these two newspapers published articles about EPA's
preliminary investigation. Media coverage followed with articles about the
Selma Leasing Company's geotechnical investigation in mid-1983. The media
attended EPA's July 1985 community meeting that explained EPA's upcoming
RI/FS activities. EPA's initiation of RI field activities in April 1986
also gained media coverage. EPA's release of the FS for public review was
also covered in news articles by the Fresno Bee and Selma Enterprise.
Finally, media were present at EPA's recent June 22, 1988 community meeting
held to elicit public comment on the FS and preferred remedial alternative.
D. Community Relations Activities Conducted By EPA
The following is a list of community relations activities conducted by EPA
at the Selma Pressure Treating Company Superfund site:
March/April
1985
July 1985
July 1985
January 1986
March 1986
EPA community relations (CR) representatives
conduct community assessment interviews with
interested community members in the Selma area.
EPA distributes a fact sheet announcing the
commencement of RI/FS work, and describing the
RI/FS activities to the community.
EPA holds a community meeting in Selma to explain
the RI/FS activities that EPA will be undertaking
to respond to the community's questions and
concerns.
EPA finalizes the Community Relations Plan
detailing the community concerns as expressed in
the July 1985 community assessment interviews and
the CR activities that EPA will conduct throughout
the RI/FS process for the Selma site.
EPA distributes a fact sheet describing the purpose
and nature of the monitoring wells placed in the
vicinity of the SPT site. EPA also distributes a
Spanish translation of this fact sheet to aid in
informing the Hispanic community of site
activities.
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May 1986 EPA Community Relations Coordinator meets
informally with community members to listen to
their concerns and to explain current site
activities.
July 1987 EPA distributes well sampling results to interested
community members.
April 1988 EPA distributes a fact sheet detailing the results
of the Rl. Also a newspaper ad was placed
announcing public review period and meeting.
May 1988 EPA issued a one page notice announcing community
meeting, public comment period and upcoming FS fact
sheet and FS report.
June 1988 EPA distributes a fact sheet explaining the
contents of the FS Report and announcing the
upcoming public comment period and community
meeting.
June 22, 1988 EPA holds a community meeting to explain the FS
Report and to receive public comment on EPA's
preferred alternative for addressing the soil and
groundwater contamination at the SPT site.
II. OVERVIEW OF THE FEASIBILITY STUDY
The Feasibility Study for the SPT site, released by EPA in June 1988,
evaluates various alternatives for cleaning up contamination at the site.
EPA will use the FS and public comment received and summarized in this
Responsiveness Summary to select the remedy for the site.
A. Description of the Contamination Problem
Soil and groundwater contamination at the Selroa site resulted from spills,
waste disposal, and waste discharges from wood treating operations. EPA
performed soil and groundwater sampling at the site as part of its RI to
determine the nature and extent of the contamination. Sampling revealed
the contaminants associated with the site to include arsenic, chromium,
copper, pentachlorophenol, and dioxin/furans. The RI also determined that
a chromium plume extended to the south and southwest of the site, away from
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the City of Selma. Sampling did not indicate contamination of any domestic
drinking water wells, irrigation wells, or municipal water supply wells.
Based on the Rl data, EPA conducted an Endangerment Assessment (EA) to
evaluate the level of public health and environmental risk posed by site
contamination. The EA concluded that the primary contaminants of concern
at the SPT site are arsenic and dioxin/furans in the soil and chromium in
the groundwater. EPA used the EA results to establish site clean-up goals
in the FS that provide adequate public health protection.
B. Summary of Remedial Alternatives
The FS for the SPT site evaluates potential remedial action technologies
for addressing the soil and groundwater contamination. Section 121 of the
Comprehensive Environmental Response, Compensation and Liability Act, as
amended, 42 U.S.C. 9621 requires EPA to select a remedy that is, among
other things, protective of human health and the environment, is
cost-effective, attains federal and state requirements, and utilizes
permanent solutions and alternative treatment technologies or resource
recovery technologies to the maximum extent practical. Additionally, EPA
is required to give preference to treatment remedies that permanently and
significantly reduce the toxicity, mobility, or volume of hazardous
substances, pollutants, or contaminants associated with the site.
The FS evaluated a wide range of clean-up alternatives and narrowed these
to four potentially implementable alternatives to address the soil and
groundwater contamination at the site. The four alternatives evaluated
include no action, containment, treatment, and treatment with disposal.
t
Alternative 1 - No Action: Under this alternative, EPA would
take no additional remedial action at the site. EPA's
objective in evaluating this alternative is to provide a
baseline against which to compare other remedial alternatives
under consideration.
Alternative 2 - Containment: This alternative would use
physical barriers to prevent further movement of the chromium
plume and to prevent exposure to soil contaminants. A slurry
wall that acts as an underground dam would be constructed to
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prevent contaminated groundwater from migrating into
unaffected portions of the aquifer. A cap designed according
to the criteria of the Resource Conservation and Recovery Act
(RCRA), would be constructed to cover the contaminated soil
areas to prevent direct exposure to the contaminated soil and
to prevent airborne participate release.
Alternative 3 - Treatment: This alternative would treat both
the soil and groundwater. Groundwater would be pumped
through lime (calcium carbonate) to remove the chromium. The
treated water would be reinjected into the ground and the
solid sludge containing the chromium would be disposed at an
appropriate disposal facility. Soil would be excavated and
treated with a fixative agent that immobilizes the
contaminants in the soil. The treated soil would be replaced
in the excavated areas, and covered with a RCRA cap.
Alternative 4 - Treatment With Disposal: This alternative
would use the same treatment method for contaminated
groundwater as the previous alternative. Dioxin contaminated
soil would be excavated and incinerated on-site.
Incineration residue and untreated metals contaminated soil
would be disposed of at a RCRA permitted disposal facility.
Based on an analysis of each alternative with respect to several evaluative
criteria, such as protecting human health and the environment, reducing the
toxicity, mobility and volume of contaminants, and cost, EPA has selected
alternative 3, soil fixation with a RCRA cap and conventional groundwater
treatment, as its preferred alternative. The cost of implementing this
alternative is estimated at $11,280,000.
III. SUMMARY OF COMMENTS RECEIVED AND EPA RESPONSES
For purposes of simplification, EPA has categorized the comments, as well
as responses to those comments, as follows:
1. Comments made by members of the interested public;
2. Comments made by State agencies; and
3. Comments made by potentially responsible parties (PRPs).
Potentially responsible parties under the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA
or Superfund) include current and past facility owners or
operators, persons who generated hazardous substances, and
persons who transported, treated, or disposed of hazardous
substances at site.
Each of these categories is presented, in turn, below.
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III.l COMMENTS MADE BY MEMBERS OF THE INTERESTED PUBLIC
No comments were received in writing from members of the public.
III.2 COMMENTS MADE BY STATE AGENCIES
EPA received comments from three state agencies. All of these comments are
summarized below.
Comments from a letter to EPA from the California Department of Health
Services (DBS) dated July 6, 1988. Comments provided below, are
derived from the memorandum attached to the letter which contained the
DBS staff comments.
Comment 1; Additional soil sampling - The extent of soil contamination has
not been fully characterized. Surface and subsurface soil sampling needs
to be performed at several locations. The subsurface soil samples below
the three to five foot depth should be selected based on grain size.
EPA Response:
EPA will be conducting additional characterization activities during the
Remedial Design (RD) Phase. These activities will include the collection
of additional surface and subsurface soil samples from the four source
areas proposed to be remedied (i.e., waste sludge pit, unlined waste
disposal pond, percolation ditch A, and the southeast disposal area) and
along the percolation ditch B. Additional soil sampling activities will
also be conducted in the retort area and along a drainage ditch located
along the north side of Highway 99. The additional sampling activities
will include collecting continuous subsurface soil samples down to the
water table at selected locations. This approach will allow for a
determination of the vertical extent of soil contamination.
The samples will be analyzed for site-specific contaminents. The analysis
will also include both the total and soluble fraction for chromium,
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hexavalerit chromium, copper, arsenic, and PCP. The analytical results will
allow for the development of a relationship between the total and soluble
fractions of the contaminants. This relationship will allow for the
determination of which other areas of contamination may represent a
potential problem from the standpoint of leaching contaminants into the
groundwater. If other areas appear to represent a problem, then additional
characterization activities will be performed in these areas or these areas
will be included in the remediation plan for the site.
Comment 2; Subsurface characterization - The lateral extent and thickness
of subsurface geologic strata needs to be more fully investigated and
defined in areas impacted by groundwater contamination. This is
particularly important for the clay that is described in the RI report as
being locally continuous at a depth of approximately 50 feet below ground
surface in the vicinity of the SPT site. The geologic characteristic
should be accomplished by continuously cored boreholes at selected
locations at a depth of at least 125 feet. Continuously cored boreholes
should also be geophysically logged, which would require that the boreholes
be installed using mud rotary drilling techniques.
EPA Response:
Six plume tracking wells to a depth of 110 to 120 feet below ground surface
were drilled during the RI. The wells were drilled using a dual-tube
percussion hammer rig, which provides excellent subsurface sample recovery.
Continuous samples were collected in the field by an on-site geologist. In
addition, four of the wells were geophysically logged using natural gamma.
The lithologic information collected during the RI was adequate to
characterize the subsurface geology in the area. As such, additional
geologic investigations to depths of 125 feet will not be performed during
the RD. EPA does recognize that additional subsurface data is required to
more fully characterize the clay layer present at a depth of 55 to 60 feet.
In order to obtain this information, lithologic data will be collected
during the installation of the monitoring wells to be performed during the
RD. The data will include the collection of continuous subsurface soil
samples from the clay layer interval. As stated in the ROD, six
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iatermediate monitoring wells will be installed to determine both the
vertical extent of contamination and background conditions for the interval
from 40 to 60 feet, which is expected to be directly above the clay unit.
The well installation program will also include a determination of the
lateral continuity and integrity of the clay unit. This will be
accomplished by drilling to a maximum depth of 75 feet, in order to verify
both the presence and thickness of the clay unit. The drilling technique
to be utilized during this program will consist of dual-tube percussion
hammer, or equivalent, such as air rotary with casing driver. Mud rotary
drilling will not be used due to the disposal problems associated with the
drilling mud. Geophysical logging of the boreholes will not be performed
since detailed lithologic information will be obtained during the well
installation program. Furthermore, the drilling methods include the use of
temporary steel casing, which limits the use of geophysical logs.
Comment 3: Additional Monitoring Wells - The present network of monitoring
wells needs to be expanded. Additional monitoring wells should be
installed at a depth of approximately 50 feet BSG to further characterize
the ground water plume. These wells should probably be screened at the top
of the clay that is identified as being locally continuous in the RI
report.
EPA Response:
Six additional intermediate monitoring wells designed to determine both the
vertical extent of contamination and background conditions will be
installed during the RD. These wells will be screened from 40 to 60 feet,
which is anticipated to be the just above the clay unit.
Comment 4; Water Quality Monitoring - All monitoring wells need to be
placed on a schedule for water quality monitoring. This schedule should be
at least quarterly for a period of one year. Also the levels of chromium
VI contamination need to be determined to design for site clean-up.
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EPA Response:
The monitoring wells, including the newly installed wells, will be sampled
quarterly for a period of one year during the RD. Hexavalent chromium data
will also be collected during the RD.
Comment 5; Water Level Monitoring - All monitoring wells in the network
should have their respective water levels measured monthly for at least a
one year period. The water level data should be tabulated, interpreted,
and plotted into flow nets (grid of equipotential and flow lines);
individual flow nets should be constructed respective to well completion
depths.
EPA Response:
Water level data for the monitoring well network will be collected on a
monthly basis for a period of one year. The data will be retabulated and
appropriate water level maps will be compiled.
Comment 6; Wells R-21 to R-25 - The RI report indicates the wells R-21 to
R-25 are monitoring wells. However, the RJ report does not provide
construction criteria or completion depths for these wells. This
information needs .to be made available in order to better interpret ground
water quality and equipotential data from these wells.
EPA Response:
EPA is currently trying to obtain additional information on these wells.
Comment 7; Dry Wells - The RI report indicates the existence of six dry
wells in the near center of the SPT site. However, no description was
provided for historical use of these dry wells. If possible, a description
explaining when the dry wells were installed, the purpose for installation,
time periods of use, and a listing of the substances, compounds, etc. and
quantities that were placed in the wells should be provided. If
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information as to the types of substances that were placed into the dry
wells cannot be determined, it may be necessary to initiate subsurface
investigations in proximity to the respective wells to check for
site-associated contaminants.
EPA Response:
It is EPA's understanding that the dry wells were installed to facilitate
drainage in the percolation ditches located along the boundary of the
storage yard. The date of the installation of the dry wells is not known
at this time. In regard to a listing of substances, compounds, and
quantity of contaminants placed in the wells, it is unlikely that this
information is available since the objective of the dry wells was to
facilitate stormwater percolation.
The dry wells in the north percolation ditch (Ditch A) will be properly
abandoned as a part of the remediation of the ditch. Additional borings
will be conducted in the south percolation ditch (Ditch B) during the RD.
The objective of the borings is to evaluate the contamination associated
with the ditch and the dry wells. The data collected during the boring
program will be evaluated and a decision regarding the appropriate remedial
measures to be taken will be made at that time. However, these activities
are predicated to some extent, on EPA being able to locate the dry wells.
Comment 8; Extraction Wells - Twenty-five extraction wells are recommended
for withdrawal of the contaminant plume at the SPT site. However, a
technical analysis to document that proposed extraction wells provide an
effective capture zone for the postulated contaminant plume is not provided
in RI/FS documents. In addition, the extraction barrier is recommended
without complete plume characterization. Present uncertainties as to the
full extent of the plume may require a more expanded network of extraction
wells and a subsequently larger ground water treatment facility.
EPA Response:
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The extraction well field discussed in the F5 was based on the data
obtained from a preliminary two-dimensional groundwater model. The intent
of the modeling effort was to design a conceptual extraction and
reinjection system for the purposes of developing the costs for the
conventional water treatment system. A detailed design of an extraction
and reinjection system will be performed during the RD following the
collection of the additional data. The data obtained from, the design of
the extraction and reinjection system will also be considered during the
design of the water treatment facility.
Comment 9; Injection Wells - The FS document recommends "approximately" 35
four-inch diameter recharge wells to inject treated groundwater back into
the aquifer. This recommendation is provided without a complete and
thorough subsurface geologic characterization of the site. Injection of
treated groundwater without detailed subsurface geologic characterization
may severely exacerbate the clean-up effort by generating unforeseen
changes in migration of the contaminant plume.
EPA Response:
As stated in the response to comment number 8 above, a detailed design of
the extraction and reinjection system will be performed during the RD
following the collection of the additional data.
Comment 10: RCRA Cap - The FS report describes several construction
criteria for the RCRA caps recommended for areas of high surface
contamination. A two percent (2%) minimum slope is recommended for the
surface of the cap. Increasing the slope angle to five percent (5%) for
tops of caps and soil liners is recommended. In addition, the permeability
of cap liners should be checked in the "field" to verify that construction
standards are achieved.
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EPA Response:
The optimum slope of the cap and the appropriate quality control/quality
assurance measures to be performed (e.g., field permeability tests) will be
determined during the RD.
Comment 11; Clean-up Goals - The possibility of leaving contaminants in
the soil which exceeds the Total Threshold Limit Concentration (TTLC)
values exists. It is recommended that confirmation samples be analyzed for
copper, arsenic, chromium and chromium VI to ensure the TTLC values are not
exceeded. Waste extraction tests should be performed where applicable.
These results should be compared to Soluble Threshold Limit Concentrations
(STLC) values which are stated in the California Code of Regulations, Title
22.
EPA Response:
As stated in the response to comment number-1, the soil samples collected
during the additional activities will be analyzed for both the total and
soluble fraction for chromium, hexavalent chromium, copper, arsenic, and
PCP. These same constituents and analyses will be performed during the
confirmation sampling.
Comment 12; Costs - The alternative screening process used in preparation
of the FS considers cost as a criteria to evaluate the various
alternatives. This includes both capital and operation and maintenance
costs. The capital costs include expenses associated with the purchase of
land. In the implementability section of the FS report, the purchase of
privately owned land to construct the slurry wall for Alternative 2, the
extraction well field, and sludge evaporation lagoons for Alternatives 3
and 4 is discussed. However, the cost estimates in Appendix F do not
include estimates for the purchase of land and vineyards.
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EPA Response:
EPA felt that easements could be obtained from landowners. As such, the
capital costs for purchasing the land were not included in the
alternatives.
Comment 13; ARARS - DBS is withdrawing the Safe Drinking Water and Toxic
Enforcement Act (Proposition 65) from consideration as an ARAR. This is
based on an interpretation of the statue indicating that the intent of
Proposition 65 was not to restrict environmental remediation activities.
EPA Response:
This comment is noted.
Conments from a letter to EPA from the California Regional
Water Quality Control Board - Central Valley Region
dated July 9, 1988.
Comment 1; The investigations which have been conducted at the site to
date are not sufficient to adequately characterize the extent of ground
water or soil contamination. The FS indicates that additional groundwater
monitoring wells and soil borings are proposed during the RD phase of the
investigation. The extent of contamination at the site should have been
determined prior to proposing the remediation alternative. The results of
the additional investigations may have a bearing on the remedial action
alternative chosen.
EPA Response:
EPA felt that there was sufficient information to develop, screen, and
select appropriate remedial alternatives. However, EPA does recognize that
additional investigation activities are required to define the extent of
the contamination. These activities have been described in the response to
comment numbers 1, 2, and 3 of the DOHS letter. Depending on the
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analytical results for the soluble fraction of the contaminants, to be
collected during these initial activities, additional characterization
activities may be conducted in other areas or these areas may be included
in the remediation plan for the site.
Comment 2; The clean-up goals developed for this site are based on human
health risk, risk associated with dermal contact and incidental ingestion
of the contaminated soils by workers, trespassers and residents. These
clean-up goals do not provide for the protection of groundwater quality.
As such, these clean-up goals are not acceptable. More appropriate clean
up levels for the constituents of concern are listed in the Table above.
An attenuation factor of 10 or less may be appropriate for the site
specific conditions (shallow groundwater, sandy soils, etc.) at this site.
The clean-up goal for groundwater (chromium) clean-up is acceptable.
EPA Response:
EPA recognizes that the soil clean-up levels for total chromium and total
arsenic may not result in groundwater protection if the soluble fraction
for these metals is high. However, data on the soluble fraction of these
metals has not been collected to date. Data sufficient to determine the
soluble fraction for chromium, hexavalent chromium, copper, arsenic, and
pentachlorophenol will be collected during the additional characterization
activities to be conducted during the RD. Following the analysis of the
additional data, the clean-up goals for these parameters will be
re-evaluated to assure that the groundwater resource will be protected and
the appropriate MCLs are obtained.
Comment 3; COM has made assumptions as to the volume of soil and
groundwater contaminated at the site without substantiating data to support
their assumptions. Before the volume of soil and ground water can be
determined, the areal and vertical extent of soil and ground water
contamination will have to be defined.
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EPA Response:
The data for determining the volume estimation consisted of both the
extensive surface soil sampling results and the general trend in the
vertical extent of contamination observed at various borings conducted at
the site. This data provided the basis for the assumptions used to
estimate the volume of soil to be remediated. However, EPA does recognize
that additional data is required to fully define the extent of soil
contamination. This additional data vail be collected during the
characterization activities to be conducted during the RD. These
activities are described in the response to comment numbers 1, 2, and 3 of
the DOHS letter.
Comment 4; Section 1.3.3, page 1-29. Surface samples were collected and
analyzed for benzene, toluene, and xylene (BTX), as well as the polycyclic
aromatic hydrocarbons (PAH), such as naphthalene and pyrene. These
constituents should also be analyzed for in subsurface soil samples,
especially in those areas where operational spillage of the PCP solvent
(diesel fuel) occurred. BTX constituents are volatile and would not
necessarily show up in surface samples, but may be present in the
subsurface.
EPA Response:
Selected subsurface soil samples collected during the additional
characterization activities to be conducted during the RD will be analyzed
for BTX and PAHs.
Comment 5; Section 1.3.4, Figures 18 and 19. Much of the data presented
in these Figures are in terms of "J" (data estimated) and "R" (data
rejected). This type of data is of little use. Additional samples should
have been collected and analyzed prior to submittal of the RI. A routine
sampling program of the monitoring wells should have been implemented to
aid in determining whether or not any trends or patterns of contaminant
migration was evident.
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EPA Response:
The data qualified by a J (Data Estimated) is consistently used by EPA to
define trends in contamination. As such, this data is extremely useful,
contrary to the statement in the comment. In regard to a routine sampling
program for the monitoring wells, EPA will conduct a quarterly water
quality sampling and monthly water level measurement program for a period
of one year during the RD.
Comment 6; Section 1.3.4, page 1-42, and Section 2.3.2, page 2-10. Since
PCP and dioxins have been detected in previous sampling rounds in wells R23
and R24, additional PCP, dioxin/furan analysis should be performed during
the RD phase in conjunction with the chromium analyses already planned.
EPA Response:
These parameters will be included in the quarterly sampling program for the
monitoring wells.
Comment 7; Section 1.3.5, Table 1-3. Seven areas of concern have been
identified due to elevated levels of site specific contaminants. A total
of five soil borings were drilled in the two unlined percolation ditches
(A&B). Additional investigations are necessary in these areas to determine
the location of the dry wells and to eliminate them as a conduit for
contaminant migration. Contamination around these dry wells is likely
since these wells were used for disposal of contaminated storm water runoff
in the past.
Three of the seven areas of concern had only surface samples collected.
The assumption was made that the vertical contamination for these areas
would have a similar pattern to those that had soil borings drilled to
ground water. They assumed contamination was present down to groundwater
for these locations. This assumption is not appropriate. Borings should
have been drilled at these sites for subsurface soil characterization as
well as determination of contaminant concentrations. Two of the seven
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areas of concern had one soil boring drilled. This is not sufficient to
characterize the lateral extent of contaminant concentrations. Additional
borings are necessary.
EPA Response:
The dry veils will be investigated during the RD. In addition, soil
borings to further define the extent of contamination will be conducted in
the areas proposed to be remediated. Both of the items are discussed in
more depth in the response to comment numbers 1 and 7 of the DOHS letter.
Comment 8; Section 2.4.4.1, Table 2-2. The 16,000 yd3 of soil to be
excavated was based on the human risk clean-up goals developed. These are
not sufficient to provide for the protection of the beneficial uses of
areal groundwater. It is likely that substantially more soil would require
remediation to meet our concerns. All seven areas may require remediation
along with some other areas of concern that have been proposed for
investigation during the RD phase.
The fourth location identified in Table 2-2 should be the "Southeast
Disposal Area" instead of the indicated "Southwest Disposal Area."
EPA Response:
As described in the response to comment number 2 above, and comment number
1 of the DOTS letter, additional solubility data will be collected during
the RD. This data will be analyzed and the clean-up goals re-evaluated as
appropriate. This re-evaluation could include additional characterization
activities in other areas presently not included in the initial phase of
investigations to be conducted during the RD. The comment concerning Table
2-2 is correct and noted.
Comment 9: Section 2.4.4.2, page 2-17. As adequate long-term pump tests
were not performed during the RI, long-term operation of the groundwater
extraction system cannot be adequately determined from data presented.
Once the extent of the plume had been defined by the installation and
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analysis of additional monitoring veils (six wells are currently proposed),
long-term pump studies should be conducted. This information is required
to adequately design the extraction and reinjection systems. It will have
to be demonstrated that the reinjection system designed will aid the
extraction system rather than work against it by changing the migration
route of the contaminant plume.
The hydrogeologic cross-sections presented on Plates 1 and 2 for P-1D,
P-2D, P-3D, P-4D, and P-5D are not sufficient to demonstrate a continuous
clay strata 5 to 10 feet thick and at a depth of 55 feet. It is assumed
that this strata has impeded the downward migration of contamination. The
additional plume tracking wells proposed during the RD phase should not be
limited to this depth when investigating the plumes vertical migration.
EPA Response:
As described in the response to comment number 8 of the DOHS letter, a
detailed design of the extraction and reinjection system will be performed
during the RD following an evaluation of the data collected during the
additional investigation activities. These activities will also include
conducting long-term constant discharge aquifier tests.
In regard to the second portion of this comment, EPA proposes to use a
phased approach to the investigation on the vertical extent of groundwater
contamination. This initial phase will include an investigation of the
integrity of the clay unit and a determination of the degree of
contamination present directly above this unit.
Additional details regarding this investigation are presented in the
response to comment number 2 of the DOHS letter. If it is determined that
the interval directly above the clay unit has significant contamination, an
additional phase will be conducted to determine the extent of contamination
below the clay unit.
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Comment 10; Section 4.2.2, page 4-6. Field permeability test must be
conducted on the clay liners to verify that the construction standards for
the caps are achieved.
EPA Response:
See the response to comment number 10 for the DOHS letter.
Comment 11; Section 4.2.2, page 4-10. Since the chromium plume has not
been adequately defined and due to a lack of sufficient aquifer
characterization (see Comment 9), it may be premature to propose a water
treatment system designed with a treatment flow rate of 1,040 gpm and give
a remediation period of five years.
The reinjection of treated groundwater, as well as the sludge lagoons and
temporary waste piles, will be regulated by waste discharge requirements
(WDRs) in order to provide for the protection of the beneficial uses of the
underlying groundwater.
EPA Response:
As discussed in the response to comment numbers 8 and 9 of the DHS letter,
the treatment flow rate was based on a preliminary two-dimensional
groundwater model. The purpose of the modeling effort was to design a
conceptual extraction and reinjection system for the purposes of the FS. A
detailed design of an appropriate well field and treatment system will be
performed during the RD following the collection of the additional data.
The substantive requirements of the WDR will be met for the reinjection of
the treated groundwater, as well as the design of the waste lagoons and
temporary waste piles.
Comment 12; Section 4.2.2, page 4-11. The surface impoundments to be
utilized for sludge drying will need to meet the construction criteria in
Title 23. Subchapter 15 of the California Code of Regulations (CCR). The
surface impoundments cannot be classified without a characterization of the
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sludge. Characterization of the sludge is also required before choosing a
final disposal option. A clay liner should be considered in the design of
the lagoons. There are no discussions concerning the removal of sludge and
what precautions will be taken to prevent the sludge removal equipment from
damaging the liners. This needs to be addressed.
EPA Response:
The design of the surface impoundments will meet the substantive
requirements of the CCR. In addition, the sludge will be characterized
prior to selection of the proper disposal option. The use of the clay
liner, as well as the procedure to remove the sludge, will be addressed
during the RD. The second portion of this comment regarding the additional
excavation is addressed in the response to comment number 2 above.
Comment 13; Section 4.2.2, page 4-12. Construction of the temporary waste
and storage facilities in the staging area will need to comply with the
construction standards for Class I waste piles in Title 23, Subchapter 15,
CCR.
The contaminated areas are to be excavated down to groundwater. Prior to
backfilling these excavated areas with the mixed soil and fixating agents,
precautions should be taken to guarantee that the fixed soil will be
backfilled in such a condition and manner that will prevent leaching of
contaminants to the groundwater. A containment system should be considered
for installation into the excavated areas to segregate the backfilled
contaminated mixture from the ground water.
EPA Response:
The substantive requirements of the-CCR for the construction of the
temporary waste and storage facilities will be met. The design details for
backfilling the fixed soil in a manner which protects the groundwater
quality will be performed during the RD.
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Comments from a letter to EPA from California State Clearing House
Office of Planning and Research
Dated July 8, 1988
Comment It An encroachment permit from the Department of Transportation
will be required for any work performed within the State right-of-way. Any
proposed mitigative measures within the right-of-way should be coordinated
with CalTrans, and the Department will be informed of proposed disposal
sites.
EPA Response:
EPA will obtain an encroachment permit from CalTrans. In addition, EPA
will coordinate any mitigative measures with CalTrans and inform CalTrans
of the proposed disposal sites.
III.3 COMMENTS MADE BY POTENTIALLY RESPONSIBLE PARTIES
EPA received written comments from three potentially responsible parties.
All of these comments are summarized below.
Comments from Letter to EPA from Bergman and Wedner, Inc.,
Dated June 30, 1988
Comment It A major conclusion of the RI report is the chromium has
contaminated the soil at several locations to depths within 5 feet of
surface, as well as shallow groundwater. Yet, most of the chromium
analyses appear to have been invalidated during the quality control
process. (See, for example, p. 4-36, RI report.) How then can this
conclusion be drawn from unverified data?
EPA Response:
Some of the data in question was qualified during data validation as
"usable for limited purposes" indicating that the data did not meet all of
the quality control/quality assurance (QA/QC) criteria under the EPA
24 123.17:5
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Contract Laboratory Program (CLP). However, the data was of sufficient
quality to utilize in defining the contamination trends. Therefore, these
data were utilized in estimating the extent of contamination at the site.
Comment 2; Chromium contamination of soil and water is analyzed in terms
of total chromium. Previous work has indicated the presence of at least
two chromium species, trivalent and hexavalent. Hexavalent chromium is a
known carcinogen, while trivalent chromium is considerably less hazardous
in the environment. Why weren't these two species of chromium quantified
individually in the RI study, and why is all the chromium in the FS report
considered to be hexavalent, when certainly it is not?
EPA Response:
Hexavalent chromium contamination was analyzed in both groundwater and soil
samples collected during the RI. However, a majority of the data was
rejected during the data validation process due to sample holding time
problems. In addition, groundwater samples were analyzed for hexavalent
chromium using field instruments. Hexavalent chromium was detected using
the field instruments, although this procedure is considered to be a
method. Due to the data validation problems associated with the hexavalent
chromium data, additional data will be collected during the Remedial Design
(RD) phase.
Any reference in the FS to the effect that all of the chromium is in the
hexavalent form was unintentional. The semi-quantitative data collected
during the RI indicates that hexavalent chromium is present but does not
constitute all of the chromium detected. Due to the presence of the
hexavalent chromium, the process options and treatment technologies
presented in the FS need to consider this constituent, as well as trivalent
chromium. As such, both hexavalent and trivalent chromium are discussed in
the FS.
Comment 3; Additional groundwater background data needs to be collected.
This data collection activity should include the installation of two
additional shallow upgradient wells.
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EPA Response:
The present upgradient wells include R-21, P-1S, and P-lD. Monitoring
wells R-21 and P-1S are completed in the shallow portions of the aquifer.
Well P-lD is completed at a depth comparable to the 5 deep monitoring wells
located downgradient of the site. The deep monitoring wells are also
completed at a depth similar to the domestic wells in the area.
The present locations of wells R-21, P-1S, and P-lD are directly upgradient
of the site. As such, these well locations provide sufficient data on
background water quality. Therefore, additional upgradient shallow or deep
monitoring wells will not be installed.
Comment 4; The FS and RI reports do not discuss the potential
contributions from other industrial activities in the area to the
groundwater and soil contamination.
EPA Response:
EPA performed preliminary assessments (PA) on several sites in the vicinity
of the SPT site. The objective of the PAs was to determine whether the
waste disposal practices at the site under investigation could result in
potential releases of contamination to the environment. The sites selected
for PAs were the Selma Nursery, Golden State Auto Body, Upright Harvester,
Pacific Gas & Electric's former Selma Gas Plant, Selma Turkey, West Coast
Growers & Packers Inc., Selma Ag Supply Inc., and Selma Electroplating.
With the exception of Selma Ag Supply and Selma Electroplating, EPA
recommended that no further action be taken at the other sites. EPA has
performed site Investigations (SI) at both the Selma Ag Supply and Selma
Electroplating. The results of the Sis for each site are summarized below.
The Selma Ag Supply site is an active agricultural chemical retail outlet
for the Selma area. The chemicals sold at the site include bulk solid and
liquid insecticides, herbicides, fungicides, and fertilizers. No blending
26 123.17:5
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or formulating of chemicals takes place on site. Selma Ag Supply is
located approxiamtely 300 feet to the northwest of the SPT site.
As a part of the SI for Selma Ag Supply, several surface soil samples were
collected. The samples demonstrated that surface soils are contaminated
with metals and pesticides. Elevated chromium values, up to 90 mgAg/ were
detected in the samples. However, the source of the chromium contamination
in the soil is not known. The SI recommends that additional investigations
are conducted at the Selma Ag Supply site to determine the lateral and
vertical extent of soil contamination and obtain data on nearby groundwater
quality.
Selma Electroplating is located approximately 1.5 miles to the northwest of
the SPT site. Chrome, copper, nickel, brass, gold, and silver plating
operations have taken place on site on an intermittent basis. In the past,
untreated wastewater and runoff form washing the floor has been drained
onto the facility soils.
Several soil samples from depths ranging from 0 to 3 feet were collected as
a part of the SI. The area selected for the collection of samples,
consisted of the waste discharge points around the facility. The samples
were analyzed for the full suite of metals. The results showed elevated
levels of several metals, inlcuding arsenic, chromium, and copper. The
levels of chromium contamination ranged from 21 to 765 mgAg. The SI
recommends that the groundwater be investigated to determine whether
contamination from the site is present.
Comment 5; Additional wells are required to further delineate the western
extent of the groundwater contamination plume.
EPA Response:
EPA recognizes that additional monitoring wells are required to further
delineate the southwestern plume boundary. To address this additional data
requirement, EPA has proposed the installation of two shallow monitoring
wells in the area to the west and south of well R-24 (FS Report, pg. 1-36).
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Comment 6; There appears to be an error in either FS Figure 1-13 or FS
Figure 1-14 (see also RI Figures 3-3 and 3-4). These figures depict
elevations of shallow and deep groundwater levels, which should differ by
some 100 feet or more, but which are shown as nearly identical.
EPA Response:
There is not an error in the referenced figures. There may be some degree
of interconnection between the shallow and deep zones which are being
monitored by the wells at the site, which would result in similar levels.
Comment 7; Chromium, nickel, arsenic and copper were all used in the wood
preservative compounds at the site, yet the FS and RI reports appear to
conclude that chromium is the only element transported downward to
contaminate the groundwater. The reports do not appear to discuss
chemistry, chemical compounds, or solubility data on these elements to
buttress this apparent conclusion.
EPA Response:
The referenced reports conclude that chromium is the only metal-related,
site-specific compound to be transported downward to the groundwater table
because chromium was the only compound observed in the groundwater at
elevated levels above background. The other metals have not been detected
at levels significantly above background.
Comment 8; Metal ratioing is a standard and acceptable method of
evaluating chemical data, metal source regions, and transport phenomena.
This method was apparently not used to any useful extent in the RI or FS
studies. Metal ratioing would be a useful tool in detecting possible
contributions by off-site sources of chromium, arsenic, copper, and other
metals to the groundwater underlying the site.
28 123.17:5
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EPA Response:
Metal ratioing was not used at the site because of the high degree of
variability in the geochemical characteristics between the metals. For
example, the solubility of the metals in both the soil and groundwater can
vary dramatically; resulting in significant variations in the mobilities of
the different metals. In fact, the mobilities of the different metals can
vary so much that the ratio of the metals in the groundwater will not be
constant across the plume. As such, metals ratioing is not a very
effective means of determining source areas.
Comment 9; The FS and RI reports appear to be silent as to the rate of
groundwater flow in the area of the site.
EPA Response:
Based on the data presented in the RI report, the effective groundwater
flow velocity varies from 100 to 830 feet/year, with an approximate average
velocity of 250 feet/year.
Comment 10; Much of the analytical data appear to be inconsistent. In
shallow groundwater analyses, arsenic is undetected in samples adjacent to
the site (Wells R-21, R-22, and R-23), yet it is detected in wells up to
2,400 feet from the site (Wells R-24, P-6S, and P-3S). If the metals have
a common source, as the report claims, this fact should be reflected in
metal ratios, which should be consistent from sample to sample,
particularly in water analyses. This does not appear to be the case for
the values of chromium, copperr and arsenic detected in FS Figures 1-18,
19, and 21 (attached).
EPA Response:
Low background levels of arsenic appear to occur in the groundwater system
at the site. This is consistent with the fact that arsenic in the amount
of 3.6 />g/L was detected at upgradient monitoring well P-1S during the
29 123.17:5
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February 1987 sampling effort. Therefore, the low levels detected at wells
R-24, P-6S, and P-3S appear to be consistent with background concentrations
of arsenic in the area.
Comments from Letter to EPA from Gerald Petery dated June 30, 1988.
For convenience, the source of the comment in the letter is referenced
under each of the comments below.
Comment 1: The RI scope of work was too broad and what is needed is
closely spaced sampling to define the extent of soil and groundwater
contamination in the identified source areas (Page 4, 3rd para.).
EPA Response:
As described in the Draft FS and ROD, additional monitoring well
installation and groundwater sampling activities will be conducted during
the Remedial Design (RD) phase. The intent of these activities is to
further define the lateral and vertical extent of groundwater
contamination. This information will further define the groundwater
contamination plume and assist in the design of the remediation program for
the site.
Additional soil sample collection activities will also be conducted during
the RD, as proposed in the Draft FS. These activities include the
collection of additional samples in the source areas recently identified to
the EPA. These areas include both the retort area and the drainage ditch
along the Highway 99 right-of-way^ Additional soil borings will also be
conducted in the source areas identified during the RI (e.g., waste
disposal pond, southeast disposal area, etc.). The intent of the boring
program will be to further define the vertical extent of site-related
contamination.
Comment 2; The approach of CDM does not provide the detailed definition of
the extent of soil and groundwater contamination, which are needed to
design a cost-effective remediation program (Page 4, 4th para.).
30 123.17:5
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EPA Response:
As discussed in the response to the previous comment, several sampling
activities to further define the extent of groundwater and soil
contamination will be conducted during the RD phase.
The volume estimates for the soil, which were utilized to generate the
costs for the remedial alternatives, were based on extensive surface soil
sampling and the general trend of contamination observed at the various
borings conducted at the site during the RI. The volume of groundwater
contamination was based on the general trend of the plume, which was
derived from the data collected during the RI. EPA felt that there was
sufficient data to estimate the volume of contaminated soil and groundwater
for the purposes of defining appropriate remedial alternatives to be
conducted at the site. However, the additional data to be collected during
the RD will be utilized to refine the development of the proposed remedial
plan for the site.
Comment 3; The lateral extent of the site-specific chemicals in the
surface soils was not defined sufficiently to form a basis of a FS of soil
remedial options (Page 5, 1st and 2nd paras.).
EPA Response:
Extensive sampling of surface soils was conducted during the RI. These
results provided data on both the levels of contamination and general
trends in the extent of contamination, particularly in the suspected source
areas. Although the lateral extent of contamination is not thoroughly
defined, EPA felt that there was sufficient data to proceed with the
remedial alternative analysis in the FS, particularly since the sampling
activities defined both the levels of contamination and general trend of
contamination. Additional data on the lateral extent of contamination in
the source areas will be collected during the RD phase.
31 123.17:5
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Comment 4; The volume of chemically-affected soil cannot be estimated
based on the results of the RI report, and this estimate is necessary to
assess the feasibility of alternative remedial actions (Pg. 5, 3rd para.).
EPA Response:
As discussed in the response to comment number 2, the volume estimation was
based on both the extensive surface soil sampling data and the general
trend in vertical extent of contamination observed at other soil borings
conducted at the site. EPA felt that this approach was sufficient to
define the volume of contaminated soil for the purposes of developing
remedial alternatives in the FS. As mentioned in several locations above,
additional sampling will be performed during the RD. The intent of this
sampling is to further define the vertical and lateral extent of
contamination.
Comment 5; The vertical distribution of the chemical concentrations in
source areas i-s undefined because subsurface samples were not taken beneath
the source areas. We contend that these areas could have and should have
been drilled and sampled (Page 6, 2nd para.).
EPA Response:
See response under comment numbers 2 and 4 above.
Comment 6; All hexavalent chromium analyses for subsurface soil samples
were rejected during data validation. Accordingly, the current evaluation
concerning chromium and the appropriateness of its proposed clean-up are
substantially lacking in foundation (Page 6, 4th para.).
EPA Response:
The clean-up level derived for chromium was based on total chromium, not
hexavalent chromium. Furthermore, a large majority of the total chromium
data was considered usable following the data validation process. However,
EPA recognizes the data validation problems associated with the hexavalent
32 123.17:5
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chromium database and will perform additional sampling for hexavalent
chromium analysis during the RD phase.
Comment 7; The existing Brown and Caldwell wells could have added
significant information to the definition of the groundwater contamination
plume (Page 1, 3rd para.)'
EPA Response:
EPA recognizes that the wells could have added significant information on
the groundwater plume. However, the wells could not be located in the
field and, as such, the status of the wells was unknown. Therefore, the
wells were not incorporated into the RI.
It has recently been pointed out to EPA that the wells may still be present
and suitable for sample collection. If this is the case, these wells will
be considered for inclusion in the sampling activities to be conducted
during the RD phase.
Comment 8; There apparently is no documentation for the EPA "R" series
monitoring wells ... It is unusual that there is no documentation for
these wells, and its absence detracts from the reliability of the samples
obtained from these wells (Page 7, 5th para.).
EPA Response:
The depth of these wells is known from measurements performed in the field.
The wells are shallow completions and are presumably screened at the water
table. In addition, the wells were installed by an EPA Emergency Response
Team (ERT) contractor following EPA approved protocol. Therefore, the
wells should provide reliable groundwater information. However, EPA is
trying to obtain additional documentation on these wells.
Comment 9: The status of the existing Brown and Caldwell monitoring wells
should have been determined and, if not usable, properly abandoned. (Page
7, last para.; Page 8, Paras. 1 and 2).
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EPA Response:
EPA is presently attempting to determine the status of the Brown and
Caldwell wells. If the wells are usable, appropriate wells will be
included in an on-going sampling program to be performed during the RD.
If the wells are not usable, appropriate measures will be taken to minimize
aggravation of the existing problem.
Comment 10; Analysis reported by Brown and Caldwell suggest that there is
a possibility of two overlapping plumes originating from separate sources
near wells R-23 and R-24. Additional wells should have been installed
between these wells to test the hypothesis of multiple source areas. The
monitoring well locations sampled by CDM do not allow the lateral extent of
the plume to be well defined (Page 8, 3rd para.).
EPA Response:
EPA recognizes that there are different sources contributing to the
groundwater contamination at the site arid that there is a potential of
multiple plumes. In order to assess this potential, EPA will attempt to
sample the existing Brown and Caldwell wells W-7 and W-8, which are located
in intermittent positions between wells R-23 and R-24. The inclusion of
these wells into the sampling program will be dependent upon the status of
the wells, as discussed in the response to comment number 9.
Comment 11; The distribution and speciation of chromium within the plume
area is unknown. This information should be determined prior to
formulating a clean-up plan' (Page 8, last para.).
EPA Response:
Semi-quantitative data on the speciation and distribution of chromium was
collected during the RI. This data indicated the presence of both trivalent
and hexavalent chromium. This information was incorporated into the FS and
the treatment of both chromium species was considered during the
34 123.17:5
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development of the remedial alternatives. Therefore, for the purposes of
the FS, there was sufficient chromium data to develop the remedial
alternatives. However, EPA will collect data on the speciation and
distribution of the chromium within the groundwater plume during the RD
sampling program. This information will be incorporated into the RD for
the conventional groundwater treatment system.
Comment 12; A potential source of groundwater contamination is the
drainage discharge area located near the intersection of Dockery Avenue and
Highway 99. No monitoring wells have been installed to test the hypothesis
of a plume of chemical concentrations in the groundwater in this area (Page
9, 1st para.).
EPA Response:
A shallow monitoring well will be installed downgradient of this potential
source area.
Comment 13; Other potential sources of groundwater contamination,
including the Consolidated Irrigation Ditch, may exist in the area (Page 9,
2nd, 3rd paras.).
EPA Response:
See response to comment number 4 under the letter from Bergman and Wedner,
Inc.
Comment 14; The percent of hexavalent chromium to total chromium for wells
R-23 and R-24 was not expressed a determinative of great importance
(Page 9, last para.).
EPA Response:
This information was not reported due to the semi-quantitative nature of
the hexavalent chromium data. This information will be reported for future
sampling activities.
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Comment 15; Screen testing for PCP was conducted using EPA Method 625,
which is very expensive. A less costly approach should have been used (EPA
Method 420.1). (Page 10, 1st para.).
EPA Response:
It is not clear which screen testing the comment is referencing. However,
Method 625 is the standard gas chromatograph/mass spectrometry (GC/MS)
method used under Routine Analytical Services for the Contract Laboratory
Program (CLP). The advantage of using method 625 is that there are a
number of parameters which are included in the analysis. As such, the
method can be a cost-effective analysis when there are a number of
parameters of interest.
Comment 16; Slug tests are not appropriate method for testing the
transmissivity of highly permeable aquifers. Even short term
constant-discharge tests would allow a more meaningful calculation of
aquifer transmissivity. There is no quantitative on-site information about
hydraulic properties of the saturated sediments underlying the SPT site
(Section II.B.4, pgs. 10 and 11).
EPA Response:
The advantages and disadvantages of the slug test- method have been well
documented in the literature. Despite the limitations discussed in the
comment, the method is a widely accepted and useful technique for
estimating aquifer transmissivity. Results can be obtained easily and
inexpensively, and a large number of wells can be tested in a short period
of time. There is no risk of artificially inducing contaminant flow within
the aquifer, and no discharge of contaminated water. In addition, the
areal variability in hydrologic characteristics of the aquifer can be
evaluated; this is not possible with one or two single well pump tests.
Both slug in and slug out tests were performed at each well at the site and
the results for both tests were presented in the RI report. In some cases,
36 123.17:5
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a better solution was obtained for either the slug in or slug out portion
of the test. This results primarily from the experience of the operator
and is one of the advantages of the method, since data can be reviewed in
the field and additional tests performed immediately as is necessary. For
example, the comment states that the initial change in water level was too
small (0.09 feet) to calculate the aquifer permeability in well P-2D.
However, if the slug out data had been examined it would be apparent that
an initial change in head of 0.9 feet was observed during this test and
that a good curve fit was obtained. In addition, it should be noted that
the instrumentation used collects the first ten readings at an interval of
0.2 seconds, not one second.
The slug test data for the deep wells are in good agreement. There is less
than one order of magnitude difference among the six wells that were
tested. This variation is within the expected accuracy of the method.
The comment indicates that the results of the slug test are nearly useless
because they do not show a difference in the hydraulic conductivity between
the shallow and.deep aquifers. Since both aquifers are composed of similar
materials, a large difference would not be expected.
EPA does plan to conduct a long-term constant discharge aquifer test during
the RD. This test will be performed utilizing an observation well
installed adjacent to a selected upgradient well at the site.
Comment 17: The precise volume of affected soils is not known, since there
are not enough soil borings near hot-spot source areas. As such, it is
difficult to predict the final cost of the various soil remedial actions,
and the validity of the FS is substantially diminished by the assertions of
conclusions without supporting data.
EPA Response:
The approach utilized to estimate the volume of contaminated soil and the
additional activities to be conducted to further characterize the source
areas are discussed in the responses to comments 1, 2 and 4 above. The
37 123.17:5
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final cost of the soil fixation will be determined following the collection
of the additional data.
Comment 18; Because of the inadequate initial evaluation of hot spots, it
may be that the actual cost of conducting the soil remedial actions may be
much higher than estimated and that other options become more favorable in
light of such costs. It is possible that less than the estimated 16,000
cubic yards were affected, resulting in lower remedial costs for this and
other technologies (Page 12, 1st para:).
EPA Response:
As mentioned in the response to comments 1, 2 and 4 above, additional
characterization activities will be conducted during the BD phase.
Depending on the results of the investigations, the remedial costs will be
adjusted accordingly. If other options for remediating the site are more
favorable, then the Record of Decision (ROD) will be amended and the
appropriate option selected.
Comment 19t CDM states that soil removal actions would remove elevated
concentrations of chromium, copper, and pentachlorophenol, even though
these chemicals are not present in soils at concentrations that would cause
significant health concerns. As such, it is difficult to estimate how much
soil is being removed to remedy arsenic and dioxin problems and how much
soil is being removed for other chemicals (Page 9, 2nd para.).
EPA Response:
The volumes of soils to be remediated were based on both dioxin and arsenic
contamination (see Table 2-2, FS Report). However, other chemicals are
associated with the dioxin and arsenic contamination due to the similar
disposal practices used for all of the chemicals at the site. Since the
site-related chemicals are associated with each other, any remediation of a
particular source area would effect all of the chemicals present.
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Comment 20; CDM did not perform any FS work to determine whether such soil
treatment would actually decrease the mobility of all constituents in the
soil matrix. Specifically, it is our concern that raising the pH may
increase the solubility of pentachlorophenol, chromium, and arsenic (Page
12, 3rd para.).
EPA Response:
EPA will perform a soil fixation treatability study during the RD which
will address this concern.
Comment 21; Arsenic is relatively immobile and currently does not appear
to pose a threat to groundwater. Hence, arsenic remediation may be
restricted to reduction of human-contact with arsenic containing soil (Page
12, 4th para.).
EPA Response:
Chromium is fairly mobile and will continue to degrade the groundwater
resource in the area. In that chromium is associated with the arsenic, the
fixation will also reduce the mobility of both chromium and arsenic. This
will prevent the leaching of chromium out of the soil and into the
groundwater. Therefore, fixation and capping of the contaminated areas
will both reduce the mobility and the potential for human contact.
Comment 22; The vertical distribution of chromium in the source areas is
still undefined. Although chromium levels in the soil are below
health-based clean-up concentrations, residual chromium in the soil may
leach downward to recharge the chromium in groundwater (page 12, last
para.).
EPA Response:
The vertical distribution of chromium will be defined during the RD (see
response to comments 1, 2 and 4). In addition, soluble levels of chromium
in the soil will be determined through sampling during the RD. If it is
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RA_Lette rs/Meroo/325
DRAF
jy
MEMORANDUM
TO: Kevin Kelly (San Francisco)
FROM: Gordon McCurry (Denver)
DATE: April 5, 1988
PROJECT: EPA Contract No.: 68-01-6939
DOCUMENT NO.: 123-FSl-IO-FZQX
SUBJECT: Preliminary Analyses of No Action and Ground Water
Extraction Alternatives at the Selma RI/FS Site
INTRODUCTION
A preliminary analysis was undertaken for two of the alternatives to be
evaluated in the Selma, California RI/FS site Feasibility Study. The first
alternative that was modeled, the No Action Alternative, involved
estimating the time required for chromium to migrate in ground water under
natural flow conditions to off-site wells. A second alternative involved
modeling a ground water extraction system that would remove contaminated
ground water under two and five year time scenarios.
The following discussion presents the background, assumptions, methodology,
and results for both the no action and ground water extraction
alternatives. The results derived from these preliminary analyses should
be considered as estimates only. Additional on-site hydrogeologic and
geochemical data combined with more sophisticated modeling techniques would
be required to refine the results obtained in the present analyses. The
calculation brief for the analyses presented in this memo is document No.
123-FS1-IO-GAEH.
ASSUMPTIONS USED IN THE ANALYSES
(A) HYDROGEOLOGIC ASSUMPTIONS
1. Aquifer is unconfined, homogeneous, isotropic, and infinite in
areal extent.
2. The base of the aquifer (clay at approximately 50 feet below
surface) is impermeable.
3. Aquifer saturated thickness = 25 feet; (derived from RI Table 2-8
and Plates 4 and 5, discounting clay intervals; CDM, 1988).
PROJ: 7777-123 FILE: 10 DEN 634
DOC NO: 123-FSl-IO-FZQX
DOC:DATE: 04/O5/88 ENTRY DATE: 07/12/E
DESC-MEMO: PRELIMINARY ANALYSIS OF G
ROUNDWATER EXTRACTION ALTERNATIVES.
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April 5, 1988
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4. Local hydraulic gradient - 0.0011 to 0.0017 ft/ft - I; (Page 3-8
and Figures 3-3 to 3-7 of RI). Average gradient assumed to be
0.0014 ft/ft.
5. Specific yield - effective porosity - 0.30 - n; (average value for
fine sane; McWhorter and Sunada, 1977, p. 31).
6. Total porosity -0.40 (derived from page 3-6 of RI).
7. Aquifer media dry weight soil bulk density 1.6 gram/cm3 - p;
(average value for fine sand; Walton, 1984).
8. Hydraulic conductivity - 100 to 400 ft/day » K; (representative
range from slug tests conducted in vicinity of plume, 3/88, and
from Freeze and Cherry, 1979). Average assumed to be 150 ft/day.
9. Effective ground water flow velocity - 100 to 830 feet/year - v -
(K/n)(I). Average flow velocity assumed to be 250 ft/yr.
10. Dispersion coefficient - 10,000 to 83,000 ft2/yr - D - (
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8. Distribution coefficient for chromium - Kd - 3.5 mL/gram; (see
section (D) below for calculations).
9. Retardation Factor - R - 1 + (p/n)(Kd) - 20.
(C) ESTIMATION OF SOURCE CONCENTRATION
1. The range in possible dissolved chromium concentration falls
between 800,000 0g/L, an average pore water concentration taken
from surface soil/sludge samples near the presumed source area
(Figure 4-3 of RI), and 8,710 //g/L, the maximum aqueous
concentration detected in well R-23.
2. The solubility of various chromium compounds as a function of Eh
and chromium concentration was modeled using the program WATEQ.
The results were used to estimate dissolved chromium concentra-
tions under Eh conditions anticipated for the aquifer.
Temperature, pH, and the concentrations of major ions were taken
from sampling results of well R-23, the well closest to the
presumed source. Iron concentration was unknown but was assumed
to be 0.05 mg/L. The above parameters were held constant as
several chromium concentrations, within above the range, were run
over a series of Eh conditions.
The WATEQ model outputs yield a saturation index (SI - log (ion
activity product/equilibrium constant) for various minerals under
equilibrium conditions for the geochemical conditions that are
input. A positive SI indicates a mineral phase will precipitate;
a negative SI indicates mineral solubility under the given
conditions. A SI of zero indicates equilibrium between dissolved
and solid mineral phases. The model also indicates which ion
species will be dominant under the stated conditions.
The model results indicated that, for a given chromium
concentration, as the Eh increased the SI decreased (chromium
mineral species became more soluble) and that the dominant ion
species changed from trivalent to hexavalent chromium.
Conversely, for a given EH, as chromium concentration increased
the SI increased (mineral species precipitated) and the dominant
ion species tended toward the trivalent forms of chromium. The
goal of the WATEQ runs was to maximize chromium concentrations,
have the dominant chromium ion species be in the hexavalent form,
maintain a.SI near zero and minimize the Eh.
Natural ground water is generally under reducing (negative Eh)
conditions. The chromium-rich source water is presumably derived
from recharge water from an unlined pond, so the ground water
below the pond was assumed to be slightly oxidizing. It was
assumed that, since chromium is probably not under equilibrium
conditions in ground water below the source, the Eh at which
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MEMORANDUM
April 5, 1988
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equilibrium conditions prevail in the WATEQ outputs will probably
be artificially elevated. Eh inputs to the WATEQ model thus
ranged from 350 to 650 millivolts.
The above modeling efforts indicated that at an Eh of 550 to 600
millivolts, hexavalent chromium ion species are dominant and
various chromium mineral species are approximately in equilibrium
between dissolved and solid phases when the chromium concentration
is approximately 16,000 //g/L. This was assumed to be the likely
maximum concentration of dissolved hexavalent chromium in ground
water immediately below the presumed surface source areas.
3. A plot of chromium concentration observed in wells downgradient of
the presumed source was evaluated to determine what the
extrapolated concentration at the source would be. The chromium
concentrations from wells R-23, R-24, R-25, and P-65 were found to
follow a log normal probability density function. The
log-transformed concentrations were plotted against distance. A
linear relationship between log transformed concentration and
distance appears to exist if the results from well R-25 are
ignored. An extrapolation of the linear trend amongst wells P-65,
R-244, and R-23 to distance » 0 yields a chromium concentration of
approximately 15,850 //g/L, which agrees well with the dissolved
chromium value derived from the WATEQ mineral solubility
calculations.
(D) CALCULATION OF CHROMIUM DISTRIBUTION COEFFICIENT (Kd)
1. Literature search:
Kd values of 2.3 and 2.4 were obtained from a column experiment
with initial Cr(VI) concentration of 50,000 //g/L, pH » 6.8, p «
1.6 g/cm and n - 0.40 (Stollenwerk and Grove, 1985).
2. Based on Retardation Factor (R):
distance traveled by conservative solute
R -
distance traveled by C/Co - 0.5 concentration of Cr
Assuming the conservative solute is the average effective ground
water flow velocity (200 ft/yr) and the duration of chromium
contamination is 10 to 30 years, the distance traveled by ground
water ranges from 2,000 to 6,000 ft. Further assuming an initial
concentration of 16,00 //g/L, the distance that half this
concentration (8,000 //g/L) has traveled is approximately 200 ft.
R therefore ranges from 10 to 30. The equation relating R to Kd
is:
R - 1 + (p/n) (Kd)
Therefore, Kd ranges from 1.7 to 5.4.
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MEMORANDUM
April 5, 1988
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3. Current data indicate that the chromium in the ground water at the
site is predominately in the Cr(VZ) state. This is consistent
with a fairly oxidizing ground water at neutral pH values.
Thennodynamic modeling under these conditions indicate that the
predominate species is Cr042~ (chromate ion). Based on this
analysis, literature was reviewed for appropriate data on
adsorption of chromate. The most consistent data were found in an
article by R.A. Griffin, A.K. Au, and R.R. Fist (J. Environ. Sci.
Health, A12(8), 431-449, 1977). Analyses of the data from this
article yield distribution coefficients ranging from 0.42 to 3.2
for pH values between 7 and 7.5.
4. Based on optimization calculations for R;
Using site-specific data, the difference between observed and
calculated concentrations of chromium in ground water was
calculated for varying R values at 10, 20, 30, and 40 year time
periods. The following equation was used in the optimization:
- 2 +
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Based on the various methods used to assess Kd and R for chromium
at the Selma site, a value of 3.5 mL/gram was selected for the
distribution coefficient Kd. A retardation factor of 20 was
assigned based on the above Kd. These values each have a
significant effect on the solute travel time and ground water
extraction rate calculations which follow, but can only be
considered as estimated quantities. More rigorous methods to
calculate Kd and R, based on additional field data, are highly
recommended.
NO ACTION ALTERNATIVE CALCULATIONS
(A) BACKGROUND
The objective was to determine how long it would take for chromium
to migrate from an on-site source area, presumably located near the
overflow ponds (Figure 4-1 of RI), to a downgradient off-site well located
south-southwest of the Selma site. The effects of advection solute
dispersion and solute adsorption onto aquifer materials were incorporated
into the travel time calculations.
(B) METHODS
A one-dimensional analytical solution (Van Genuchten and Alves, 1982) was
used in the travel time calculations. The advection-dispersion equation
with adsorption given below is the governing equation:
where c - concentration, t time, x « distance, other variables previously
defined. The initial and boundary conditions are as follows:
c(x, 0) - CA
c(o.t, - C0 for 0 t
O
(, t ) o
Initial concentrations (Ct ) were assumed to be zero. Source concentration
(C0), constant throughout the modeling period, was assumed to be 16,000
//g/L based on Assumptions, Section C above. The resulting analytical
solution (Van Genuchten and Alves, 1982) is as follows:
c«x.t, - ci * t0
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April 5, 1988
Page 7
*"" - "" * * "
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GROUND WATER EXTRACTION CALCULATIONS
(A) BACKGROUND
A preliminary analysis was undertaken to estimate both the total volume and
the rate at which chromium contaminated ground water needs to be extracted
to reduce ground water concentrations down to 50 i/g/L chromium. Two year
and five year ground water cleanup time periods were evaluated. Well field
designs involving both extraction and recharge wells were modeled.
Approximate capital costs for both designs are summarized.
(B) METHODOLOGY
The volume of water required to be pumped out of the aquifer was estimated
using a mixing cell model, which calculates the number of pore volumes
(based on total porosity of the aquifer) that need to be removed. The
mixing cell model incorporates compound adsorption and desorption between
the aquifer soil and water. Each iteration in the mixing cell model
involves replacing the contaminated ground water in a unit volume of
aquifer media with clean water. The volume of ground water which is
replaced in each iteration is determined by the effective porosity of the
aquifer media. The contaminant of interest is then desorbed from the
aquifer media into the clean ground water, causing a corresponding decrease
in concentration of the compound present in the aquifer media. Desorption
from the aquifer media into the aquifer fluid is dependent upon the
distribution coefficient (Kd) of the compound being modeled. It is assumed
that compound adsorption/desorption is reversible and follows a linear
isotherm. The mixing cell model continues until ground water
concentrations from desorbed aquifer media compounds are below the desired
concentration value. The number of iterations required to attain the
desired ground water concentration value represents the number of pore
volumes required to clean up the aquifer being modeled.
The mixing cell model was run assuming an initial concentration of 16,000
//g/L chromium, Kd of 3.5, p and n previously defined. The number of pore
volumes required for cleanup varies as a function of concentration, so the
estimated plume area was broken into five zones of assumed equal chromium
concentration (as derived from the analytical solute transport solution).
Given an initial estimated area in which chromium exceeds 50 //g/L of
1,001,500 ft2, the area and volume of each of the five zones was
calculated. Although compound adsorption was assumed to follow a linear
isotherm and be completely reversible, the findings of Stollenwerk and
Grove (1985) suggest that at low chromium concentrations the Kd increases.
To account for this phenomena, the maximum estimated concentration present
in each of the five zones was assumed to be the chromium concentration for
the entire zone. The mixing cell model results were then used to determine
how many pore volumes of water had to be removed from each zone, based on
the concentration assigned to each zone, to achieve cleanup. The following
table summarizes the area, volume, estimated Cr concentration, number of
pore volumes, and total volume required for cleanup in each of the five
zones.
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MEMORANDUM
April 5, 1988
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Zone
1
2
3
4
5
Maximum
Concentration
90
330
1,200
8,710
16,000
Area (ft2) Volume (gal)
400,000
333,000
151,500
85,200
32,800
29,920,000
24,908,400
11,332,200
6,373,000
2,453,400
Number
of Pore
Volumes
11
35
58
94
105
Totals
1,002,500 ft* 74,987,000 gal
Total
Volume
(gal)
329,120,000
871,800,000
657,270,000
599,060,000
257,610,000
2,714,860,000 gal
The total volumes required for each zone, presented above, provided the
basis for the veil field designs. A net ground water extraction rate was
calculated for each zone for both the two and five year cleanup scenarios.
A minimum number of wells were placed in each zone such that total
discharge rates met the calculated extraction rate for each zone and
the aquifer was stressed sufficiently without causing dewatering. Effects
of the regional hydrauic gradient on capture zones of individual wells was
not considered in the calculations.
The model used in the well field designs is General Aquifer Analysis (Koch
& Associates, 1986). This two-dimensional program assumes Theis conditions
in the aquifer and adjusts drawdowns for an unconfined aquifer via the
Jacob correction factor, for decreasing saturated thickness. The model
further assumes that each well is fully penetrating, has a constant
discharge and well casing storage is negligible. Aquifer hydraulic
conductivity (150 ft/day), specific yield and saturated thickness
(previously defined) were assumed constant throughout the model area. Due
to the variable pump rates required for each zone within the chromium plume
and access limitations associated with U.S. Highway 93, a uniform well
field grid was not attempted.
(C) RESULTS
The two year ground water cleanup scenario was achieved via 35 extraction
wells and 45 recharge wells. The extraction wells pumped at rates of 55 to
100 gallons per minute (gpm) with systemwide average pumping rates of
approximately 74 gpm. The modeled extraction system would deliver
approximately 2,580 gpm to an assumed on-site treatment system. The
recharge wells would inject treated water via gravity drainage at rates
varying between 40 and 75 gpm. Passive recharge is not expected to be as
efficient as well-induced discharge, so a greater number of recharge wells
are required to replace the water removed by the extraction wells. Well
efficiencies, however, were not considered in the modeled well field
system. Drawdowns after two years ranged from approximately 24 feet near
the highest-yield wells to approximately 3 feet near the recharge wells.
It is assumed that any treated water which is not reinjected into the
aquifer can be discharged into an existing municipal sewer system.
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MEMORANDUM
April 5, 1988
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The design assumes that the extraction wells will be 6 inch ID steel wells
completed under Level D health and safety conditions in 12 inch holes
drilled via air hammer or rotary techniques. Twenty feet of galvanized
steel screen and 30 feet of steel casing would be installed in each well.
Well development water will be treated at the on-site treatment system.
Piping systems to convey extracted and recharge water to and from the
wellheads are approximate; however, the well field design assumed that
wells installed southwest of U.S. Highway 93 had water routed along South
Avenue under the highway. Each extraction well would have an automatic
water level sensor and cutoff device to regulate discharge and minimize
pump motor maintenance. The recharge wells would be installed in 10-inch
holes drilled with hollow stem auger techniques. Twenty-five feet of high
efficiency 4-inch PVC screen and 25 feet of 4-inch schedule 40 PVC casing
would be installed in each hole under Level D conditions.
Capital costs are summarized in Table 1. The cost summary does not include
costs associated with land acquisition, right-of-ways, pipe distribution
system burial, or the treatment system. Operations and maintenance costs,
including power, recharge well cleaning and maintenance, and equipment
replacement were also not developed for the alternatives.
The five year cleanup scenario is similar to the two year design, except
that fewer wells are required to remove the required volume of ground
water. The five year design involves 25 extraction wells, which pump at
rates between 20 and 60 gpm, and 35 recharge wells which have design
recharge rates of 10 to 30 gpm. The system flux is approximately 1,040
gpm. After five years, drawdowns range from approximately 17 feet near
extraction wells to 7 feet near recharge wells. All other aspects are
similar to the two year design. Capital costs are summarized in Table 1,
excluding operations, maintenance, and other costs discussed above.
It should be noted that both well field designs and their associated costs
are preliminary. The final well field designs will probably contain fewer
wells that are spaced further apart and pump at higher rates. The exact
spacing of wells and pump rates for individual wells cannot be determined
without the use of more sophisticated modeling techniques and additional
site aquifer tests and contaminant distribution data. The suggestion that
Kd, and thus R, increases with decreasing chromium concentration
(Stollenwerk and Grove, 1985) could mean that chromium cannot be completely
removed (below the 50 //g/1 action level) in either a two-year or five-year
scenario. Methods to accelerate chromium desorption as concentrations
decrease should be evaluated. Potential methods may include a pulsed
ground water extraction scenario, oxygenating recharge water to increase
aquifer Eh and raise chromium solubility or adding a chromium ion exchange
medium such as amonium acetate to the recharge water.
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MEMORANDUM
April 5, 1988
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REFERENCES
Con. 1988. Draft Remedial Investigation Report, Selma Pressure Treating
Site. Selma, CA. Document No. 123-RI1-RT-FNKW-1
Freeze, R.A., and J.A. Cherry. 1979. Ground Water. Prentice-Hall, Inc.,
Englewood Cliffs, NJ.
Koch and Associates. 1986. General Aquifer Analysis, Version 3.
Engineering Technology Assoc. Ellicott City, MD.
McWhorter, D.B. and D.K. Sunada. 1977. Ground Water Hydrology and
Hydraulics. Water Resources Publications. Fort Collins, CO.
Stollenwerk, K.G. and D.B. Grove. 1985. Adsorption and desorption of
hexavalent chromium in an alluvial aquifer near Telluride, Colorado.
J. Environ. Qual. 14:150-155.
Van Genuchten, M.Th., and W.J. Alves. 1982. Analytical Solutions of the
One-Dimensional Convective-Dispersive Solute Transport Equation.
Technical Bulletin No. 1661, Agricultural Research Service, U.S.
Department of Agriculture.
Walton, W.C. 1984. Practical Aspects of Ground Water Modeling. National
Water Well Association. Columbus, OH.
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RA. Letters/Meno/326
TABLE 1
CAPITAL GOST SUMMARY FOR WELL SYSTEM
Component
Two-Year Scenario
Estimated Total
Unit Cost Quantity Cost
Five-Year Scenario
Estimated Total
Unit Cost Quantity Cost
EXTRACTION WELLS
$175/hr
Drilling Mobilization
Drilling Completion and
Development Tine (10 hr/Well) $175/hr
6" Steel Casing (30 ftAell) $ 10/ft
6" Galv. Steel Screen (20 ft/tell)$ 40/ft
Misc. Materials (sand, cement, etc$ 4/ft
3 50 ft well)
Pump (4" pump @ 60 gpm) $680/ea.
Pump Set Up (4 hr/tell) $ 50/hr
Protective Clothing & Materials Fe$ 50/crew-hr
Cuttings Disposal (8/hole) $250/drum
RECHARGE WELLS
Drilling Mobilization
Drilling Completion and
Development (8/hr well)
4" PVC Casing (25 ft/tell)
4" PVC Screen (25 ft/well)
Misc. Materials (50 ft/well)
Protective Clothing & Materials
Cuttings Disposal (6/hole)
Well Installation Totals
$140/hr
$140/hr
$4.50/ft
$36.00/ft
$4.00/ft
Fe$50/crew-hr
$250/drum
16
350
,050
700
,750
35
140
350
280
16
360
,125
,125
,250
360
270
$ 2,800
61,200
10,500
28,000
7,000
23,800
7,000
17,500
70,000
$ 228,000
$ 2,200
50,400
5,100
40,500
9,000
18,000
67,500
$ 193,000
$ 421,000
16
250
750
500
,250
25
100
250
200
16
280
875
875
,750
280
210
$ 2,800
43,750
7,500
20,000
5,000
17,000
5,000
12,500
50,000
$ 163,600
$ 2,240
39,200
3,950
31,500
7,000
14,000
52,500
$ 150,400
$ 314,000
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TABLE 1 (cent.)
CAPITAL COST SUMMARY FOR WELL SYSTEM
Component
DISTRIBUTION SYSTEM
SW of Hwy. 93
2" Steel Pipe
6" Steel Pipe
4" PVC Pipe
2" Poly Ethylene Pipe
NE of Hwy. 93
2" Steel Pipe
12" Steel Pipe
8" PVC Pipe
2" Polyethylene Pipe
Miscellaneous
Control Valves (Automatic
Water Level Sensor & Cutoff)
Holding Tank
Two-Year
Estimated
Unit Cost Quantity
$17.00/ft
$38.00/ft
$10.00/ft
$7.50/ft
$17.00/ft
$76.00/ft
24.00/ft
$ 7.50/ft
$570
$25,000
1,300 $
900
900
1,300
5,600 $
400
400
5,600
35 $
25,000
Scenario
Total
Cost
22,100
34,200
9,000
9,750
95,200
30,400
9,600
42,000
19,950
Five-Year Scenario
Estimated Total
Unit Cost Quantity Cost
Distribution System Totals
$ 297,200
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TABLE 1 (cent.)
CAPITAL COST SWIARY FOR WELL SYSTEM
Two-Year Scenario
Five-Year Scenario
Estinated Total Estimated Total
Component Unit Cost Quantity Cost Unit Cost Quantity Cost
SW of Hwy. 93
IV Steel Pipe
4" Steel Pipe
4" PVC Pipe
IV PVC Pipe
ME of Hwy. 93
iy Steel Pipe
8" Steel Pipe
6" PVC Pipe
iy Polyethylene Pipe
Miscellaneous
Control Valves (Automatic)
Holding Tank
Distribution System Totals
SUBTOTAL COST
Engineering, Contingency,
Construction Management (0.3)
TOTAL COST
$16.50/ft
$25.00/ft
$10.00/ft
$ 3.00/ft
$16.50/ft
$57.00/ft
$19.50/ft
$ 3.00/ft
$570
$25,000
$ 718,200
$ 215,500
$ 933,700
1,100
900
900
1,100
3,800
400
400
3,800
25
1
$ 18,150
22,500
9,000
3,300
$ 62,700
22,800
7,800
11,400
$ 14,250
25,000
$ 196,900
$ 510,900
$ 153,300
$ 664,200
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determined that the soluble levels of chromium are below the clean-up goal
but potentially pose a threat to groundwater quality, then additional
chromium contaminated soil below the clean-up goal will be evacuated and
treated.
Comment 23; Dioxin in the soil is not addressed by fixation (Page 13, 1st
para.)
EPA Response:
EPA's preferred treatment method, Alternative 3, consists of solidifying
and fixating (stabilizing) the contaminants in the soil. The organic soil
contaminants, including dioxin, are remediated by encapsulating them in a
high strength, low permeability monolith. However, vendors are also
marketing fixative reagents which immobilizes the toxic organic soil
contaminants, as well as the inorganic contaminants. The organic compounds
are stabilized by adsorption to the fixative agent. The required leach
tests would be performed on the treated soil to assure that, through a
combination of solidification and fixation processes, the dioxin is
remediated to acceptable levels.
Comment 24; The definition of the lateral extent of chromium-affected
groundwater and the number of plumes have not been defined. The possibility
of a plume originating in the vicinity of drainage discharge area at the
intersection of Dockery Avenue and Highway 99 has not been evaluated (Page
13, 3rd para.).
EPA Response:
See responses to comment numbers 1, 2, 10 and 12.
Comment 25; We have some concerns as to the estimated groundwater
extraction rates, number of extraction wells, the treatment process
proposed, the years of operation, and the estimated annual operating cost.
We strongly question CDM's estimate of 25 extraction wells with a resultant
flow rate of over 1,000 gpm. In the absence of quantitative data for the
40 123.17:5
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hydraulic properties, the number and location of required extraction and
recharge wells cannot be properly determined (Page 13, 4th and 5th paras.,
Page 14, 2nd para.)
EPA Response:
The flow rates, treatment period, and O&M costs were based on a
two-dimensional modeling effort conducted for the site. The modeling is
preliminary in nature and was performed to determine the relative costs of
the water treatment system. A more detailed modeling effort to accurately
design an extraction and recharge well field will be performed during the
RD following the collection of the additional data. The groundwater
treatment process proposed in the FS is a very common and widely accepted
process. In regard to the quantitative data, an additional constant
discharge aquifer test will be performed. This test will supplement the
existing quantitative data obtained from the slug tests.
Comment 26; Our concern over the CDM treatment process is that CDM has
assumed the bulk of chromium is trivalent chromium rather than hexavalent
chromium (Page 14, 3rd para.).
EPA Response:
EPA recognizes that hexavalent chromium is present in the groundwater. The
FS indicates that the treatment system will be flexible enough to include
hexavalent chromium treatment (e.g., pages 3-50 and 3-51). The exact
configuration of the treatment system will be determined during the RD
following the collection of the additional data.
Comment 27; We question the use of sludge lagoons for sludge handling
(Page 14, para. 4).
41 123.17:5
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EPA Response:
Sludge lagoons were included as the sludge dewatering component of the
water treatment alternatives to take advantage of Selma's hot and dry
climate. High evaporation rates during large portions of the year are
conducive to lagoon implementation. Lagoon design included a double liner
system and leachate collection measures to protect against possible
leakages.
It was recognized in the FS report that other sludge handling measures
should be evaluated and compared with sludge lagoons. On page 3-53 the
following statement is made: "Alternative sludge dewatering processes,
such as centrifuges or rotary drum filters, will be evaluated, and compared
to sludge lagoons during the remedial design stage of the project."
Comment 28; CDM has consistently taken an overly broad and costly approach
to the RI/FS. The current series of investigations should have more
closely defined the lateral and vertical extent of chemical concentrations.
Treatability studies should have been conducted. The results of the site
investigation are therefore inadequate for the final selection of
remediation techniques and the estimation of performance and cost (Section
III, pgs. 14 and 15).
EPA Response:
This comment is addressed in the response to comment numbers 1, 2, 3, 4, 5,
17, 18, 20, and 24.
Comments to EPA in a Letter from Mr. James D. Wilson
of Barding-Lawson Associates dated July 12, 1988.
Comment 1; The lateral extent of the chromium plume (including
concentrations greater than 50 micrograms per liter) in groundwater has not
been defined and other potential upgradient sources of contamination have
not been evaluated.
42 123.17:5
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EPA Response:
EPA will be installing additional wells to define the extent of
contamination during the RD phase. EPA is also investigating additional
potential sources in the area. These aspects are further discussed under
the response to comments 1, 2, and 13 from Mr. Petery's letter.
Comment 2; No monitoring wells have been installed downgradient of two of
the four soil contamination areas identified as warranting remediation (the
Waste Sludge Pit and the Southeast Disposal Area depicted on Figure 1-22).
EPA Response:
An additional shallow monitoring well will be installed downgradient of the
southeast disposal area (see comment no. 12, Mr. Petery's letter). In
regard to the waste sludge pit, existing well R-22 is located approximately
downgradient. An additional shallow monitoring well to be installed during
the RD will be located approximately 400 feet due west of existing well
R-24. This well will be installed to define the extent of groundwater
contamination and will be located downgradient of the waste sludge pit.
These additional wells, in combination with the existing wells, will be
sufficient to determine the potential contribution to the groundwater
contamination from these two sources.
Comment 3; The hydraulic parameters that control groundwater flow and
contaminant transport at the site have not been adequately evaluated (no
aquifer tests).
EPA Response:
This comment has been addressed under the response to comment number 16
from Mr. Petery's letter.
Comment 4; Insufficient temporal water-level fluctuation data are present.
43 123.17:5
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EPA Response:
EPA will collect monthly water level data for a period of one year during
the RD. This data will be sufficient to define the temporal water-level
fluctuations.
Comment 5; Because of data validation problems, no valence-specific
chromium data (hexavalent versus trivalent chromium) are available for soil
or groundwater.
EPA Response:
EPA will collect additional valence-specific chromium data for both soil
and groundwater during the RD. Additional information is presented in the
responses to comment numbers 6 and 11 of Mr. Petery's letter.
Comment 6; No characterization data are available for the ditch along
Highway 99 or the reported "effluent pond" within the treatment area.
EPA Response:
Additional surface and subsurface soil samples will be collected along
Highway 99 ditch during the RD. These samples will be analyzed for
site-specific contaminants. It is not clear to which "effluent pond" the
commentor is referring. However, characterization data has been collected
for the unlined waste disposal pond and additional data will be collected
in this source area as well as the adjacent retort area.
Comment 7; Insufficient soil data are available for the isomer-specific
dioxin and furan analyses needed to evaluate whether there is in fact
sufficient risk associated with site conditions to warrant remediation.
EPA Response:
The existing isomer-specific dioxin and furan data clearly show a risk
associated with the unlined waste disposal pond and the southeast disposal
44 . 123.17:5
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area. Both of these areas exceed the health-based Center for Disease
Control (CDC) clean-up level of 1.0 parts per billion (ppb) for
dioxin/furan in tetra-chlorinated dibenzodioxin (TCDD) equivalents.
However, additional isomer-specific dioxin/furan data will be collected
during the characterization activities to be conducted during the RD.
These activities are described in the response to comment numbers 1, 2, 4
and 5 of Mr. Petery's letter.
Comment 8; Insufficient soil data are available for evaluating the lateral
and vertical extent of soil contamination (metals and organics) in the four
areas identified in the FS report that will be subject to excavation and
treatment.
EPA Response:
Additional characterization activities for these four areas will be
conducted during the RD. These activities are described in the response to
comment numbers 1, 4, and 5 in Mr. Petery's letter.
Comment 9; No data collected prior to 1986 were used for the FS.
EPA Response:
The data collected prior to 1986 was utilized to design the approach to the
RI. In regard to the FS, the quality of the pre-1986 data was questionable
and, as such, the data was not used to evaluate appropriate remedial
alternatives for the site. For example, all of the data collected during
EPA's RI was subjected to stringent quality assurance/quality control
(QA/QC) evaluation during data validation. In addition, EPA's Contract
Laboratory Program (CLP) follows established QA/QC criteria to assure the
highest data quality can be achieved. The data collected prior to 1986 did
not follow these protocols or procedures. In addition, as stated in the
Work Plan for the SPT site (June 1985), several of the samples taken are
not identified as to location and depth. Others do not have complete
records as to the sample results, sampling protocols, or analysis
procedures. However, the pre-1986 data will be used during the RD to
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define general trends in contamination and identify areas which warrant
further characterization.
Comment 10; No data have been developed to assess the potential transport
mechanisms of site contaminants based on total versus soluble
concentrations of any of the chemicals of concern.
EPA Response:
Solubility data for the appropriate, contaminants in the soil will be
collected during the characterization activities to be conducted during the
RD.
Comment 11; No treatability studies have been performed to assess the
actual reduction in mobility of site contaminants achievable by the
remedial alternatives.
EPA Response:
A treatability study for soil fixation will be conducted during the RD.
Comment 12; pi "... would remediate the potential for exposure to . .
." should read "... would reduce exposure to . . ."
EPA Response:
The FS does evaluate alternatives which would both remediate the potential,
as well as reduce the potential, for exposure to contamination.
Comment 13; pi There is no mention of SARA or the incorporation of ARARs
into the evaluation process. Recent guidances from Winston Porter,
Assistant Administrator, U.S. EPA, on preparing of FS documents should also
be referenced. Full references could be presented in the introduction.
Comments on appropriate guidances are presented in the introduction section
review.
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EPA Response:
Both SARA and ARARs are referenced on page 1-2 of the FS.
Comment 14; pl-1 "The RI data indicate . . . treating operations pose a
potential threat ..."
This statement is not true for two reasons: 1) there was no assessment of
risk or threat in the RI report; the Endangerment Assessment was a separate
report, and 2) the "potential threat to human health and the environment"
was not posed by "previous wood treating operations" but by the results of
waste management and disposal activities at the site prior to 1981.
EPA Response:
This statement was eluding to the fact that the risks presented in the
Endangerment Assessment were based on the data collected during the RI.
Comment 15; pl-1 "A significant portion of the plume is above the
clean-up goal and will require remediation."
The definition of significant needs to be quantified.
EPA Response:
Significant in the context of the statement refers to the portion of the
plume which is above the clean-up goal, which represents a large portion of
the total plume.
Comment 16; pl-1 "The Feasibility Study (FS) evaluated . . . alternatives
based on the data in the RI Report."
This statement is not entirely true. The evaluation is largely based on
the Endangerment Assessment, which was not a part of the final RI report.
The Endangerment Assessment is particularly relevant in developing an
understanding of what remedial actions are appropriate to protect human
47 123.17:5
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health and the environment, since only in the Endangerroent Assessment are
the threats to human health and the environment investigated. Raw data
developed in the RI are an inadequate basis for drawing conclusions that
the existing conditions pose a threat to human health and the environment.
Evaluation criteria stated in this section are inconsistent with the March
1988 draft RI/FS guidance from EPA on evaluation procedures; furthermore
they are inconsistent with procedures stated in the Executive Summary where
the appropriate nine criteria were stated (see page 7-3 of the 1988 RI/FS
guidance for the listing of the criteria).
EPA Response:
The first portion of this comment is addressed in the response to comment
number 14 above. In regard to the evaluation criteria, the criteria used
in the FS were consistent with relevant EPA guidance but were not all
presented in the referenced citation.
Comment 17; pl-2 "The FS has been prepared in accordance with ..."
The FS should also be in accordance with the following SARA interpretive
memoranda from J. Winston Porter, Assistant Administrator, U.S. EPA:
o Implementation Strategy for Reauthorized Superfund; Short Term
Priorities for Action, October 24, 1986
o Interim Guidance on Superfund Selection Remedy, December 24,
1986;
o Interim Guidance on Compliance with Applicable or Relevant and
Appropriate Requirements, July 10, 1987.
EPA Response:
The draft RI/FS guidance dated March, 1988 supercedes the first two items
identified above. The ARARs guidance was utilized during the development
of the FS.
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Comment 18; pl-4 "The groundwater resources . . . have been classified as
a beneficial use, sole source aquifer by the California Regional water
Quality Control Board."
What is the specific reference for this classification; we are not aware of
such a designation under the Safe Drinking Water Act or any other federal
or state law?
What aquifer was classified? Does this classification apply to the depths
found to contain chemicals?
The statement is confusing because groundwater resources are not a
beneficial use. What are beneficial uses of water that has been found to
contain chemicals?
EPA Response:
The groundwater resources in the area have been classified as a sole-source
aquifer by the EPA under Section 1424(e) of the Safe Drinking Water Act.
EPA has also classified the aquifer as a Class IIA current drinking water
source with other beneficial uses under the Groundwater Protection Strategy
(1984).
Comment 19: pl-5 In the third paragraph, references and/or methodology
for identifying disposal areas should be included in the description of
site activities.
EPA Response:
These disposal areas and practices were observed by or identified to the
CRWQCB and DOHS.
Comment 20; pl-10 Why were no previous data used, either from the EPA's
Field Investigation Team or the Brown & Caldwell report?
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EPA Response:
This comment has been addressed under the response to comment number 9.
Comment 21: .pl-11 Quality Assurance problems related to analyses for
trichlorophenols are noted, but no reference is made to the near complete
loss of hexavalent chromium data during data validation.
EPA Response:
This comment is accurate in that most of the hexavalent chromium data was
rejected during data validation.
Comment 22; pl-19 The discussion of dioxin contamination and Toxicity
Equivalent Factors fails to point out that no site-specific samples had
2,3,7,8 TCDD detected in them and there is still no direct documentation of
2,3,7,8 TCDD contamination. All risk evaluations were therefore based on
equivalents and using these calculated values, the three worst-case samples
were just barely above the clean-up goal. Therefore, it is not clear or
demonstrated that a risk-based dioxin problem exists at the site.
EPA Response:
The dioxin/furan sample results, including the results for 2,3,7,8-TCDD,
are clearly shown in tables 1-1 and 1-2 of the FS. The results also
clearly show that dioxin/furan contamination exceeds the CDC clean-up goal
at two locations as discussed in the response to comment number 7 above.
Comment 23; pl-25 The first paragraph concludes that volatile organic
chemicals were not found because they had volatilized. Could it be that
they were never released? The statement implies EPA has evidence of their
release. If so, it should be given.
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EPA Response:
Diesel fuel was used as the carrier for the pentachlorophenol. In that
volatile components are present in diesel fuel, and pentachlorophenol
contamination is present at the site, there is justification to expect
volatile contamination at the site. In order to evaluate this potential,
samples from the soil borings to be conducted during the RD will be
analyzed for benzene, toluene, xylene, and polycyclic aromatic
hydrocarbons. These results will determine whether volatile, or diesel
fuel-related contamination, is present at the site.
Comment 24; pl-25 Of the 21 borings installed to evaluate subsurface soil
conditions, only 4 (S6, 7, 9, and 11) were drilled in potential source
areas. This has led to a deficiency in soil data on the lateral and
vertical extent of chemicals in the source areas targeted for remediation.
EPA Response:
This comment is addressed in the response to comments number 1 and 4 of Mr.
Petery's letter.
Comment 25; pl-27 Why were no analyses performed to evaluate the
potential soluble fraction of contaminants in any of the soil samples?
This has resulted in insufficient data for evaluating potential migration
of chemicals through the soil and into groundwater.
EPA Response:
Additional solubility data will be collected during the characterization
activities to be conducted during the RD.
Comment 26; pl-36 The eastern boundary of the chromium plume has not been
defined contrary to the statement on Page 1-36. The location of Well P-4S
is south of the site, not east. Additional monitoring wells will be
required to adequately assess the areal and vertical extent of groundwater
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contamination resulting f-rom the SPT operations. The SPT RI .report has not
characterized the areal and vertical extent of groundwater contamination in
the vicinity of the site and therefore the technical adequacy of the FS
appears to be incomplete.
EPA Response:
Well P-4S is located southeast of both the treatment and past-disposal
areas located on the wood treatment facility. Furthermore, well P-4S is
located to the east of the plume emanating from these areas, particularly
when considering the southwestern groundwater gradients present at the
site. Given this information, EPA feels that there is sufficient
information to define the eastern boundary of the plume in this area.
However, EPA does recognize that additional information on the lateral and
vertical distribution of the plume is required in other areas, such as the
southwestern boundary of the plume. This information will be collected
during the additional characterization activities planned for the RD.
Comment 27; pl-42 We point out that the lack of groundwater monitoring
data is confirmed by CDM based on their recommendation that 4 additional
wells be installed and sampled. These wells are designed to monitor a zone
that is vertically between existing shallow and deep wells.
EPA Response:
As pointed out above, EPA recognizes that additional monitoring data is
required.
Comment 28; p2-5 The clean-up goal for arsenic in soil is based on the
plausible maximum exposure of dermal exposure and ingestion. The
assumptions for these exposures are not justified in Appendix E. This
comment also applies to all calculations of health-based risk of arsenic in
Appendix E.
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EPA Response:
The clean-up goal for the SPT site was based on the average exposure,
whereas the vineyard clean-up goal was based on plausible maximum exposure.
However, it is not clear why the assumptions are not justified. As such,
EPA cannot respond to the comment.
Comment 29; p2-6 Regarding the discussion of the soluble portion of
chromium being a problem that was not addressed in the RI or EA, why wasn't
it addressed in either document? If this soluble portion is significant
enough to qualify the clean-up goals developed in the EA, it suggests that
the EA and RI are inadequate with respect to chromium contamination. It
also implies that the current FS is based on inadequately documented and/or
faulty assumptions.
EPA Response:
EPA recognizes that additional data on the soluble portions of the chromium
contaminated soil is required. This data will be collected as a part of
the additional characterization activities associated with the RD.
Comment 30; p2-9 Same comments as above, but with regards to the
discussion of TTLC and STLC data for PCP.
EPA Response:
See the response to the above comment.
Comment 31; p2-10 No assumptions are stated to justify that 75 million
gallons of water beneath the site have chromium concentrations above the
clean-up level. All assumptions and methodologies used to calculate this
volume should be stated to allow assessment of their validity.
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EPA Response:
A two-dimensional groundwater model was utilized to estimate the quantity
of groundwater requiring treatment. The assumptions for the model are
described in a memorandum, which attached to the Responsiveness Summary.
Comment 32; p2-13 The areas considered for excavation are bounded at best
on only two sides with analytical results for surface samples used to
define the extent of contamination. In general, the definition of the
extent of soil contamination is wholly inadequate for estimating volumes of
soil requiring remediation, regardless of clean-up goals.
The proposed depth of excavation is apparently based on no physical or
chemical data, which implies that the pursuant remediation scheme analysis
may be based on faulty assumptions and misrepresent the appropriate
remediate program for the level of contamination truly present.
EPA Response:
Additional soil borings, with associated surface soil sampling, will be
performed as a part of the characterization activities performed during the
RD. These activities will further define the extent of contamination in
the disposal areas to be remediated. The second portion of this comment is
addressed in the response to comment numbers 2 and 4 of Mr. Petery's
letter.
Comment 33; p2-15 In the second paragraph, reference^to chromium and
copper is irrelevant since all detected concentrations are below clean-up
goals as stated no page 2-5. This reference should be struck.
EPA Response:
The levels of these constituents relative to the clean-up goals are
discussed in order to demonstrate that the high levels of total copper and
chromium detected at the site are below the clean-up goals. These
constituents are also discussed to demonstrate that the arsenic clean-up
54 123.17:5
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goal is driving the remediation at the site. Furthermore, the other
constituents, particularly chromium, need to be considered from the
groundwater protection standpoint. These aspects are relevant points and
should have been included in the FS.
Comment 34; p2-17 Discussion of how the wells will be completed to
determine the vertical extent of contamination should be present.
EPA Response:
As stated in the ROD, the six intermediate wells will be installed during
the RD to define the vertical extent of contamination. These wells will be
completed in the interval directly above the clay layer. It is expected
that these wells will be completed from 40 to approximately 60 feet.
Comment 35; p2-17 Porosity of 40% is high for coarse-grained soils. What
"site-specific lithologic data" was this estimate based on? A reduction of
the porosity to 30% (a 25 percent reduction) could account for a reduction
of 675 million gallons of water to be treated. A more explicit
presentation of the basis for the assumption should be stated.
There is no presentation of the assumptions on which the "mixing cell
model" is based. Earlier on page 2-17 it is stated that the
hydrostratigraphy is poorly defined; nevertheless, a solute transport
modeling effort was undertaken. The assumptions and limitations of this
model effort should be clearly stated.
The assumptions used to calculate 2.7 billion gallons of water to be
remediated are not clear, therefore there is no basis for assessing the
validity of this number.
EPA Response:
The assumptions used for these determinations are presented in the
memorandum for the groundwater modeling effort performed at the site. This
memorandum is attached to the Responsiveness Summary.
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Comment 36; p3-2 The FS states that the greatest risk at the SPT site is
associated with contact with carcinogens in the soil. No basis for this
statement is given. Assumptions should be stated.
EPA Response:
The statement on page 3-2 of the FS is not entirely correct in that there
are various risks associated with exposure to both the soil and groundwater
at the site. A summary of the risks for both media is presented in Table
6-1 of the Final Endangerment Assessment.
Comment 37; p3-10 On the basis of the hydrogeologic cross sections of
borings completed at the site (presented in RI report), it appears that the
"confining layer" beneath the site is of variable thickness, absent at
locations, and comprised of materials which include "silty sand", "silt",
and "clayey sand". Because of these factors, the effectiveness of a slurry
wall "keyed" into the reported "confining layer" is questionable as leakage
through this layer seems likely. Therefore, inclusion of the slurry wall
as a technically viable alternative is questionable.
The cost estimate for the slurry wall option is $1,730,000 which includes
14 extraction wells. However, no technical data is presented in the RI or
FS report to substantiate extraction rates available at the site or the
number of extraction wells required to achieve hydraulic containment. This
data is basic hydrogeologic information which can be obtained from pump
tests or aquifer tests but is not available for the SPT site. The basis
for the installation of the 14 extraction wells is required before an
assessment of cost for the slurry wall option can be made.
EPA Response:
The existence of a confining layer beneath the site was based on an
evaluation of the stratigraphy represented by two cross-sections presented
in the FS report (Plates 1 and 2). The plates depict a clay layer
approximately 55 feet deep and 5 to 10 feet thick underlying the site. The
56 123.17:5
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lack of significant levels of contamination detected at depths between 90
and 120 feet also suggests the presence of this low permeability clay lens
is impeding downward groundwater movement.
A subsurface investigation along the proposed slurry wall alignment would
be performed during the remedial design phase of the project if this
technology was selected for implementation. The investigation consists of
a series of borings which would be evaluated to locate and define the
confining layer utilized for keying in the slurry wall.
The installation of 14 extraction wells to control the hydraulic gradient
in the vicinity of the slurry wall was estimated based on the data
available. The accuracy of the cost estimate to construct the slurry wall
system is within the range required by EPA guidance for conducting
feasibility studies.
Comment 38; p3-50 It is stated that treated wastewater may be used to
recharge the aquifer. However, no consideration is given for assessing
either the hydraulic, geochemical, or institutional constraints of
reinjection.
EPA Response:
Three disposal options for the treated wastewater were listed in the
section referenced by the comments. In addition to aquifer reinjection,
use as an irrigation water supply and discharge to the local sewer system
were mentioned. The objective of this section of the report is to describe
potential remedial action technologies. Assessment of hydraulic,
geochemical, or institutional constraints would be performed during the RD.
Aquifer remediation is achieved by extracting the chromium plume and
thereby allowing clean water to enter the aquifer. The chromium
contaminant is desorbed from the aquifer media, into the clean groundwater.
This flushing action is aided by the reinjection of the treated wastewater,
ultimately resulting in the chromium concentration decreasing to acceptable
levels. The theoretical results of the pumping and recharging of the
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aquifer in terms of water level (hydraulic) impacts is presented in the
memorandum on the modeling effort attached to this Responsiveness Summary.
Aquifer reinjection would need to meet the substantive requirements of the
Regional Water Quality Control Board, and the Safe Drinking Water Act, 42
USC 1421-1422, and the underground injection control requirements of 40 CFR
Part 144 - 147.
Comment 39; p4-l Alternative 2 does not meet the criterion presented on
page 4-1 for an alternative that relies on containment with little or no
treatment. As presented in Section 3.3.4, the slurry wall as proposed
includes continuously operating ground-water extraction wells (14
extraction wells are shown on Plate 3-1). All ground water thereby
extracted will require treatment in a manner identical to the presented for
Alternative 4. It appears that no alternative has been presented that
addresses containment with little or no treatment.
EPA Response:
Alternative 2 does meet the criterion at a remedial alternative which
relies on containment with a minor treatment component. Soil remediation
is addressed by constructing a cap over the top of the areas of soil
contamination. This does not utilize treatment technologies or process
options. The control of contaminated groundwater migration is provided by
the slurry wall containing the chromium plume, proundwater extraction
rates necessary to establish a hydraulic gradient towards the plume would
be much less than those proposed in Alternative 4. Therefore the quantity
of groundwater to be treated under Alternative 2 is significantly less than
under Alternative 4.
Comment 40; p4-2 Conclusions are being drawn from a "model," yet details
on the assumptions that went into the model are not provided. All
assumptions should be stated. An appendix with the details of the modeling
analyses must be supplied to enable review of these assumptions.
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EPA Response:
The assumptions that went into the model are presented in the attached
memorandum. The memorandum includes the details of the modeling analysis.
Comment 41; p4-3 Why was an open slurry wall selected? Why not close the
site with a four-sided slurry wall and eliminate the need for pumping since
a RCRA cap that would prohibit infiltration is being used? Because the
treatment costs for the extracted ground water associated with the slurry
wall are not included, serious doubt is thrown on the costs presented for
this alternative.
EPA Response:
Closing the site with a four-sided slurry wall would not eliminate the need
for pumping. The chromium plume requiring containment has an areal extent
of approximately 20 acres. The proposed areas to be capped encompass only
3/4 of an acre of this 20 acre parcel. In order to prohibit infiltration
inside the area contained by the slurry wall, the entire 20 acres would
require coverage by an impermeable cap. Large areas of existing vineyards,
both on site and off-site, would then no longer be available for
agricultural applications. Unless the entire site was capped, pumping
would be required to control the buildup of hydrostatic pressure on the
inside of slurry wall created by stormwater infiltration.
The four-sided slurry wall would be approximately 2,500 feet longer than
the wall described in the FS. In addition, portions of the wall would
cross Highway 99 in two locations and cut through the existing wood
treatment facility.
Comment 42; p4-6 Without a good understanding of the local
hydrostratigraphy, it is impossible to understand the potential
effectiveness of a slurry wall. Without a continuous competent aquitard to
key the base of the wall into, the contaminants can simply flow under the
wall as if it were not there. If extraction wells are necessary to make
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the wall a viable option, then the utility of the wall is in serious
question, particularly at a cost of $1,730,000which does not include
costs for a water treatment system, which will be required. Costs
presented later suggest an additional $1,770,000 just in capital costs
alone will be required for the water treatment system (page 4-35).
EPA Response:
The existence of a confining layer beneath the site was based on an
evaluation of the stratigraphy represented by two cross-sections presented
in the feasibility study report. A subsurface investigation along the
proposed slurry wall alignment would be performed during the design phase
of the project if the alternative was selected for implementation. The
results of the investigation would be evaluated to define the extent of the
aquitard to key the base of the wall into.
Extraction wells would be necessary to make the wall a viable option.
Capital costs, to construct an on-site water treatment plant, presented
under Alternatives 3 and 4, represent a much greater treatment flow rate
than would be required utilizing the slurry wall proposed under Alternative
2. Therefore, capital water treatment costs associated with Alternative 2
would be significantly less than $1,770,000.
Comment 43; The entire detailed evaluation of Alternative 3 is based on a
"mixing cell model" that is not justified, described, or explained. It is
impossible to evaluate the validity of the detailed analysis for
Alternative 3 without explicit details on the modeling effort that is
referenced. If the model were improperly formulated, all conclusions for
Alternative 3 could be based on faulty assumptions.
EPA Response:
The "mixing cell model" utilized in formulating groundwater treatment rates
and quantities for Alternative 3 is described and explained in the attached
memorandum on the groundwater modeling effort.
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Comment 44; p4-10 Modeling comments presented for Alternative 3 apply to
Alternative 4 as well.
The estimated costs presented for each alternative may vary greatly from
those stated because the source areas and extent of contamination have been
inadequately defined. See comments on Section 2.0.
EPA Response:
The "mixing cell model" utilized in formulating groundwater treatment rates
and quantities for Alternative 4 is described and explained in the attached
memorandum on the groundwater modeling effort. The estimated costs for the
proposed plan (Alternative 3), will be revised following the additional
source characterization activities, which will be conducted during the RD.
Comment 45; p4-43 The State of California appears correct to insist that
the site be adequately characterized prior to remedy selection. As stated
previously, the data collected thus far are inadequate to define the
hydrostratigraphy and volumes of soil and ground water requiring
remediation, and therefore the same data are inadequate to support a proper
FS or selection of a remedy.
EPA Response;
As stated in various responses to previous comments, EPA feels that there
is sufficient data to select a remedy for the site. However, EPA does
recognize that additional data will be required to fully define the extent
of the remediation. As such, additional characterization activities for
both the soil and groundwater contamination will be conducted during the
RD.
Comment 46; p5-l Alternative 1 disadvantages: "The lack of control of
contamination migration creates a high potential for the spread of
exposure."
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"High potential" was not assessed. It should be qualified or the statement
struck.
EPA Response:
Under Alternative 1, the transport mechanisms which caused contaminant
migration to occur initially would remain in place. Specifically source
areas of soil contamination would still be vulnerable to leaching of the
contaminants by stormwater runoff and conveyance to groundwater supplies.
As the areal extent of aquifer contamination increases, the potential for
exposure through groundwater ingestion increases. The longer contaminated
surface soils remain vulnerable to wind dispersion, the greater the
potential for exposure due to dermal contact, inhalation, and ingestion.
For these reasons the EPA states that a high potential for the spread of
exposure would exist under the no action alternative.
Comment 47; Alternative 2 advantage: "It has relatively low capital and
O&M costs."
Potential costs to treat extracted groundwater were omitted from this
alternative. These capital costs would be $1,770,000 and O&M costs could
be $1,280,000 per year (see page 4-35). These costs appear to contradict
the statement.
EPA Response:
The stated capital costs of $1,777,000 and O&M costs of $1,280,000 per year
for the water treatment component of Alternatives 3 and 4 are based upon
constructing and operating a 1,040 gpm capacity treatment facility. The
rate of groundwater extracted under Alternative 2 would be significantly
less than 1,040 gpm, therefore, the costs to construct and operate would be
much less.
Comment 48; p5-3 Alternative 2 disadvantage: "The ability of the clay
layer to provide adequate foundation to key the slurry wall into may be a
limiting factor..."
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We agree; further more, this points up the inadequacy of the site
characterization to provide sufficient data to evaluate alternatives in the
FS.
EPA Response:
There is sufficient data to propose the slurry wall as a component of the
containment alternative. If Alternative 2 was selected as the remedial
action for the site, a subsurface investigation along the slurry wall
alignment would be performed. The results of the investigation would be
evaluated to define the extent of the clay layers and determine its ability
to provide an adequate foundation to key the slurry wall.
Comment 49; p5-3 Alternative 3 advantage: "It provides for near complete
removal of groundwater."
This statement is unjustified and unfounded based on data presented in this
FS. An 'undocumented model was used in the evaluation and no details on its
formulation, calibration or sensitivity analyses are provided in the FS.
EPA Response:
The statement referenced in the comment misquotes the FS report. Under
advantages for Alternative 3 on page 5-3 the following statement is made:
"It provides for near complete removal of the groundwater contaminants."
The attached technical memorandum presents a description of the model
employed in the FS.
Comment 50; p5-4 Alternative 4 advantage: "complete removal of
groundwater".
See comment for Alternative 3.
EPA Response:
See EPA response to comment number 49 above.
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ATTACHMENT
Groundwater Modeling Memorandum
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