United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R06-89/051
September 1989
%EPA
Superfund
Record of Decision:
Sheridan Disposal Services,
A 5
f jp\?f * --v-
|f*S:.«f v
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50272-101
REPORT DOCUMENTATION 1. REPORT Na 2.
PAGE EPA/ROD/R06-89/051
4. Title and Subtitle
SUPERFUND RECORD OF DECISION
L Sheridan Disposal Services, TX
B Second Remedial Action - Final
^. Author(s)
9. Performing Organization Name and Addreaa
12. Sponaoring Organization Name and Addreee
U.S. Environmental Protection Agency
401 M Street, 's'.W.
Washington, D.C. 20460
3. Recipient* Accaaaion No.
5. Report Date
09/27/89
6.
8. Performing Organization Rept No.
10. ProiecVTaak/Work Unit No.
11. Corrtract(C) or Grant(G) No.
(C)
(G)
13. Type ol Report & Period Covered
800/000
14.
15. Supplementary Note*
16. Abetract (Limit: 200 words)
The 110-acre Sheridan Disposal Services site is approximately 9 miles northwest of< the
city of Hempstead in -Waller County, Texas. The site is located on the 100-year
floodplain of the Brazos River and is bordered by a lake to the south, farmland, and a
community of 20 residences to the north. The Evangeline aquifer, which runs under the
c: i h o ic n <5oH r-n moot- r- ho Hi-TnVinrr tja t- o T- nooH Q n •F Qotro r-a 1 ^nrmrm n-it-TOQ noa rVM/ Qho-r-iHan
Disposal Services operated as a commercial waste disposal facility from about 1958 to
984 using steam distillation, open burning, incineration, and direct disposal into a
[aste lagoon to dispose of various organic and inorganic chemical and solid wastes. The
site includes a 12 to 22-acre lagoon, a 17-acre dike surrounding the lagoon, a 42-acre
evaporation/land irrigation system, and an incinerator and 9 waste storage and treatment
tanks located on the lagoon dikes. The primary contaminants of concern affecting the
soil and sludge are VOCs including benzene and toluene, and other organics including
PCBs.
The selected remedial action for the site includes excavation of all material with PCB
concentrations greater than 25 mg/kg including 13,000 yd3 of pond and dike soil, 31,000
yd3 of pond sludge, and 300 yd3 of floating oil and emulsion in the pond and storage
tanks. This will be followed by onsite biotreatment of (Continued on next page)
17. Document Analyal* a. Descriptor*
Record of Decision - Sheridan Disposal Services, TX
Second Remedial Action - Final
Contaminated Medium: gw
Key Contaminants: VOCs (benzene, PCE, TCE), metals (arsenic)
b. Identifiera/Opan-Ended Term*
c. COSATI Field/Group
18. Availabiity Statement
1*. Seo»tty Oaee (Thi* Report)
None
20. Secutty Claaa (Thto Page)
None
21. No. ol Page*
89
22. Price
{See AHSt-Z3S.18)
See (rulructfone on Retwnae
OPTIONAL FORM 272 (4-77)
(Formerly NT1S-3S)
Department at Commerce
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EPA/ROD/RO6-89/051
Sheridan Disposal, TX
16. Abstract (Continued)
contaminated soil, sludge, and oil with stabilization and onsite disposal of residuals in
the pond. If PCB concentrations in the residuals are less than 50 mg/kg, they will be
placed under a RCRA-compliant cap. Residuals with PCB concentrations greater than 50
mg/kg PCB will be placed in a RCRA-compliant landfill in the pond area. In addition, the
remediation requires capping the entire pond and dike area; decontamination and offsite
disposal of tanks, drums, and debris; treatment to best available technology (BAT) of any
contaminated wastewater and stormwater with discharge to the river; implementation of
engineering controls tq prevent bank erosion on the river; and ground water monitoring.
The estimated present worth cost for this remedial action is $27,956,000, which includ.es
total O&M costs of $863,000.
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RECORD OF DECISION
FDR
SHERIDAN DISPOSAL SERVICES SITE
WALLER COUNTY, TEXAS
(GROUND WATER MIGRATION MANAGEMENT OPERABLE UNIT)
UN I'm; STATES ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER 1989
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DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Sheridan Disposal Services site, Waller County, Texas
STATEMENT OF PURPOSE
This decision document outlines the selected remedial action for the second
operable unit at the Sheridan Disposal Services site in accordance with the
Comprehensive Environmental Response, Compensation and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments and Reauthorization Act of
1986 (SARA), and to the extent practicable, the National Oil and Hazardous
Substance Pollution Contingency Plan, 40 CFR Part 300, November 20, 1985.
On December 29, 1988, a Record of Decision (ROD) was signed which selected the
appropriate remedial action for the Source Control Operable Unit for the
Sheridan site. The Source Control ROD addressed the risks associated with
exposure to contaminated soils and sludges on the site.
This document is the ROD for the second operable unit, hereafter referred to as
the Ground Water Migration Management, or GWMM unit. The ROD for the GWMM unit
addresses the risks associated with the potential or actual exposure to
contaminated ground water.
The State of Texas (through the Texas Water Commission) has been provided
an opportunity to comment on the technology and degree of treatment proposed
by the Record of Decision. The letter describing the State's concurrence
with the selected remedy is found in Appendix C.
STATEMENT OF BASIS
This decision is based on the administrative record for the Sheridan site.
The index found in Appendix A identifies the items which comprise this admini-
strative record.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if
not addressed by implementing the response action selected in this ROD, may
present an imminent and substantial endangerment to public health, welfare,
or the environment.
DESCRIPTION OF THE REMEDY
Upon review of the information contained in the administrative record, it
is EPA's judgment that the natural attenuation alternative best serves
both statutory and selection criteria in relation to the other solutions
evaluated. A detailed description of this remedy and an explanation of how
it meets statutory requirements is contained in the attached "Summary of
Remedial Alternative Selection."
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Implementation of the natural attenuation alternative requires the
following components:
1. The establishment of Alternate Concentration Limits (ACLs) as
the' site ground water protection standards.
2. Ground water monitoring to ensure ACLs are not exceeded.
3. Sampling and analysis of the Brazos River immediately downgradient
and upgradient of the point of entry of ground water from the site
into the river.
4. Implementation of controls to preclude potential use of contaminated
ground water.
5. In the event ACLs are exceeded at sometime in the future, the
implementation of a corrective action plan to ensure that
protective levels are met at the point of potential exposure.
Implementation of these activities addresses the principal threat posed by
the site by preventing exposure to contaminated ground water and by
maintaining safe levels in the Brazos River.
STATUTORY DETERMINATIONS
The remedy described above is protective of human health and the environment,
attains Federal and State applicable or relevant and appropriate requirements
and is cost-effective. This remedy satisfies the statutory preference for
remedies that utilizes permanent solutions and alternative technologies to
the maximum extent practicable. However, this remedy does not satisfy the
statutory preference for treatment as a principal element because treatment
of ground water contamination was found to be impracticable. Further, it
should be noted that the Source Control remedy utilizes treatment as a
principal element.
Because this remedy may result in hazardous substances remaining onsite above
health-based levels, a review will be conducted within five years after com-
mencement of the remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment.
Robert E. Layton Jr., PIF., 'Date
Regional Adm.nistrator
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SHERIDAN DISPOSAL SERVICES SITE
WALLER COUNTY, TEXAS
SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
SEPTEMBER, 1989
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TABLE OF CONTENTS
PAGE
I. SITE LOCATION 1
II. HISTORY AND ENFORCEMENT 1
III. HIGHLIGHTS OF COMMUNITY PARTICIPATION 2
IV. SCOPE AND ROLE OF OPERABLE UNIT 3
V. SITE CHARACTERIZATION 3
5.1 Geology 3
5.2 Hydrogeology 3
5.3 Sanplings Results 4
VI. SUMMARY OF SITE RISKS 4
VII. ALTERNATIVE EVALUATION 6
7.1 Evaluation Criteria 6
7.2 Description of Alternatives 8
7.3 Evaluation of Alternatives 9
VIII.SELECTED REMEDY 12
8.1 Description of Selected Remedy 12
8.2 Rationale for Selection of the Remedy 15
IX. STATUTORY DETERMINATIONS 17
9.1 Protection of Human Health and the Environment 18
9.2 Compliance with Applicable or Relevant and Appropriate
Requirements of Other Laws 18
9.3 Cost-Effectiveness 19
9.4 Utilization of Permanent Remedies and Alternative Treatment
Technologies to the Maximum Extent Practicable 19
9.5 Preference for Treatment as a Principle Element 20
X. DOCUMENTATION OF NO SIGNIFICANT CHANGES 20
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XI. APPENDICES
A. Administrative Record
B. Responsiveness Summary
C. State Response to Record of Decision
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LIST OF FIGURES
FIGURE NUMBER TITLE
1 General Site Location Map
2 Site Location Map
3 Site Plot Plan
4 General Schematic of Site Geology
5 Approximate Extent of Ground Water Contamination
6 Alternative 2: Partial Slurry Wall Alignment
7 Alternative 3: Recovery Well Configuration
8 ACL Points of Compliance
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LIST OF TABLES
TABLE NUMBER TITLE
1 Geologic Description and Water-bearing Properties
of the Geologic Units forming the Aquifers in
Waller and Austin Counties
2 Sunmary of Highest Levels of Contaminants Detected in
Shallow Ground Water
3 Summary of Alternative Costs
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I. SITE LOCATION
The Sheridan Disposal Services site is located approximately nine miles north-
northwest of the City of Hempstead in Waller County, Texas. The site covers
about 110 acres in a 700-acre tract of land which is bordered by the Brazos
River to the north and Clark Road to the South (See Figures 1 and 2).
Located at the site are a lagoon (12-22 acres depending on water levels), a
17-acre dike surrounding the lagoon, and a 42-acre evaporation/land irrigation
system. An incinerator and a group of nine storage tanks which were used
for waste storage and treatment are located on the lagoon dikes. These
site features are illustrated in Figure 3.
The predominant land-use within a four-mile radius of the site is agriculture
and range land. The only primarily residential area within this four-mile
radius is the community of Brown College. This conmunity is made up of
approximately 20 residences and is located one and one half miles north
of the site. Nearby communities primarily utilize ground water from the
Evangeline aquifer to meet their water supply needs.
The site is relatively flat, but slopes gently to the south. It lies within
the 100-year floodplain of the Brazos River. However, the lagoon dikes have
been built up to an elevation above that of the floodplain.
II. SITE HISTORY AND ENFORCEMENT
Sheridan Disposal Services operated as a commercial waste disposal facility
from about 1958 to 1984. A wide variety of organic and inorganic chemical
and solid wastes were disposed of at the site. The facility treated waste
by steam distillation, open burning and incineration. The lagoon was devel-
oped in a low-lying area of the site and was used as a holding pond, and for
the disposal of overflow wastes and waste treatment residues. In 1976,
the facility initiated use of the evaporation system for disposal of water
which accumulated on the lagoon.
The site's regulatory history began in 1963 when the Texas Water Quality
Board (now known as the Texas Water Commission) issued a permit authorizing
disposal of industrial solid waste. After permitting, the Texas Water
Quality Board (TWQB) received complaints concerning odor, runoff and
oil in the Brazos River. The State also noted increased concentrations of
contaminants in on-site monitoring wells.
In 1970, the TWQB and Waller County filed suit against the Sheridan facility.
After a series of meetings and public hearings, in 1975, a judgement was
entered by the Court which prohibited further discharge of wastes into the
lagoon. The TWQB and Sheridan Disposal Services discussed numerous closure
plans for the lagoon until the TWQB determined that the facility did not
have the economic or technical resources necessary to close the lagoon
properly. In 1984, the Texas Department of Water Resources (successor of
the TWQB) sent letters to generators and transporters of waste managed at
the site to notify them of their potential liability under the Comprehen-
sive Environmental Response, Compensation, and Liability Act (CERCIA).
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COURTNEY
GRIMES
QEERWOOO
WASHINGTON
SHEftlOAN
DISPOSAL
SEMVICI
—<* WLi^
SCALE (MILES)
FIGURE I
SITE LOCATION MAP
SHERIDAN DISPOSAL SERVICE
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In response to this notification, the Sheridan Steering Committee, which is
now known as the Sheridan Site Committee, organized and began to investigate
the extent of contamination at the site. After polychlorinated biphenyls
(PCBs) were identified in the lagoon, EPA became directly involved in site
closure through the Toxic Substances Control Act. The site was ranked
according to the Superfund Hazardous Ranking System and on June 10, 1986, the
site was proposed for inclusion on the National Priorities List. The basis
for inclusion on the NPL was primarily the volume, toxicity and mobility of
contaminants found at the site and ground water contamination resulting from
the site.
In June and July of 1986, 102 Notice/Information request letters were sent to
site Potentially Responsible Parties (PRPs). During this time, the Sheridan
Site Committee submitted a Remedial Investigation to EPA for evaluation.
After reviewing this document the Agency determined that additional field
investigations would be necessary to obtain adequate information on which to
base a ground water remedy decision. However, in order to expedite lagoon
cleanup and reduce further leaching into ground water, the site was divided
into two operable units, a Source Control unit which was addressed in a pre-
vious ROD and the Ground Water Migration Management (GWMM) unit which is
addressed in this ROD.
On February 3, 1987, 59 companies who were members of the Sheridan Site Com-
mittee entered into an Administrative Order on Consent with EPA to complete
both the Source Control and GWMM remedial investigation/feasibility studies
(RI/FSs). In 1988, EPA issued a unilateral order to site PRPs to lower the
level of water in the lagoon. This action was implemented by the Committee's
contractor with EPA oversight.
After the ROD for the Source Control operable unit was issued, additional
Notice/ Information request letters were issued and Special Notice letters
informing PRPs of the Remedial Design/Remedial Action (RD/RA) Moratorium
period were submitted to over 180 PRPs. The Sheridan Site Committee, the
Department of Justice (DCJ) and EPA have reached a tentative agreement for
Source Control remediation.
EPA will continue its enforcement activities and send Special Notice Letters
to FRPs prior to the initiation of the remedial design of the GWMM operable
unit. Should the PRPs decline to conduct future remedial activities, EPA
will either take enforcement actions or provide funding for these activities
while seeking cost recovery for all EPA-funded response actions from the PRPs.
III. HIGHLIGHTS OF COMMUNITY PARTICIPATION
In general, there has been a long history of citizen awareness of the
Sheridan Disposal Services site. In the early 1970s when incineration at
the site resulted in air emissions, people living within a 7-mile radius
complained. In 197 j. a citizens' group submitted a petition with over 500
signatures to the Texas Water Quality Board calling for its closure.
However, community concerns of either the area residents or local officials
are now very low, probably because the site has been inactive since 1984.
Also the site is relatively remote and there are no residences within a mile.
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The proposed plan fact sheet announcing the public comment period and opportunity
for a public meeting for the ground water portion of the site was distributed on
July 31, 1989. The comment period began on August 14, 1989 and ended on Septerber
11, 1989. No one responded to the offer of a public meeting and none was held. No
written comments or questions were received by EPA.
IV. SCOPE AND ROI£ OF OPERABLE UNIT
This ROD describes the remedy selection process for the second operable unit,
which is known as the Ground Water Migration Management (GWMM) unit. The
function of this operable unit is to 'prevent potential exposure to contaminated
ground water and ensure protective levels are maintained in the Brazos River.
The FDD for the Source Control Operable unit at the site was issued in Deceirber
1988. The Source Control ROD addressed the risks associated with exposure to
contaminated soils and sludges from the site.
V. SITE CHARACTERIZATION
5.1 GEOLOGY
The Sheridan site lies on the Brazos River Alluvium of recent age, which is
comprised of gravel, sard, silt and clay deposited by the meandering river.
The Brazos River Alluvium unconformably overlies the Miocene-aged Fleming
formation. The Fleming is made up of interbedded sand and clay layers.
Table 1 provides a general description of the hydrogeologic units present in
Waller and Austin counties. However, all formations from the Goliad sand to
the Beaumont clay are not present beneath the site.
According to the Austin sheet of the Geologic Atlas of Texas, no faults with
surface expression occur in the vicinity of the site. Field investigations
conducted by the responsible parties' contractor verified this conclusion.
The Hockley escarpment and salt dome are found about 18 miles south of the
site and the Millican fault zone lies approximately 20 miles to the north.
However, there is no evidence that these features influence the hydrogeology
of the site.
5.2 HYDROGBOIDGY
The alluvium of the Brazos River forms the first Regional aquifer beneath the
site. The Evangeline and Jasper aquifers underlie the alluvium. Most wells
in the vicinity of the site tap the Evangeline aquifer, which is about 450
feet thick beneath the site.
Figure 4 describes a general cross-section of site hydrogeology. The first
water-bearing unit, which is referred to as the shallow aquifer, is identi-
fied in the cross-section as Stratum B. This aquifer is part of the sediments
of the Brazos River Alluvium. The second water-bearing unit, know as the
deep aquifer, is identified as Stratum D. This unit is part of the Evangeline
aquifer. The clay layer know as Stratum E lies beneath the confined aquifer
at about 100 feet in depth and was the deepest unit investigated at the site.
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Geologic
Table 1
IpUon and netar-beulng prop*rti« of the geologic eniU forming the equtftri in Aia*in and lUUar Oantlee
Aquifer
Alluvial
Bring
•uiki
Aquie
-
tliim
rlllt
ludt
r
Strtti graphic
unit
Tributary alluriue
•id flood-plain
•llwiu* al tM
Iraoi U*tt
i Miami, day
•bnt gentry
Focaatlon
•entiiy
ronatlen
MUlii Send
Oil lad Sand
n«ing
formation
Otahoula
0«difftr«nti«t*d
Ctxinaud
trtickneii
in araa
(feet!
0- •
0- 7i
0- «?
0- SO?
o- :«?
0- 140?
»-l,7W
t
—
Central eoBcotiUcn in
Atartln and tUller OxnUai
decanal id»t*d grey, team, and
reddiah-bcam day, silt, and
•ndy clay, oamovly overlying
llght-oolored amnd ot oneratr-
ortlned aand and gravel.
tetUed red. radaiaVeram. brown
and gray, denat clay with «hitt
ctlcareaui nodulea. »*y oanfcaln
Imei of fin* *n) wdlil*-
oralnrd a>nd ot avtd and •?•*•!
in Dtaoia.
U^it gray to li^it team. lUf-
fralnrd amnd, ailt, and clay,
prctably oradinj vlUi drpth to
ferk*r-eolac*d onaracr Bind and
in (iaott t»«U amnd 4nd ojawl.
MU rnatinq bnh e< t»ill*-biam
to yellow and oray, (DtUad
Clay Intcrtcddtd «iUi ajayijti,
fir»- to oDaiac-oralntd nnd
•nd o^avcl l«nai>. tattaiad
lantili ot llpa i»»ar»ii1
aandrtora. Qay, amdy clay,
•nd lirm and prtAslnU in
the u&xt ptrt, dtrMr-colorad
coarair aand and yavel in tnt
lane {art.
Wttmatinj b»di of aptUad r«d«
yclla>, tecwn, and ojray clay
and atnd vith aatt>r*d Imaci
iniortcd aand and qtartx qcavcl.
rvrru^iroui nodulaa ooaoou
•acttd and hud in freah «qx>-
aurc*. hatl pin It uaxally
* hard, •r*v*lly *v«d and clay.
Whitt to 9tay, aticky, calartoui
clay vith intcrbcdM IIMCI of
liojit-colorad, gravelly mnt
and lln-oa»0it*d atnditont.
Uact chart o^aina in tM
vhitiah aand O^T« a a>lt and
papptr aftact.
Inurbeddni clay and aandi clay
pi«da>inanUy in tiw
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lA
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irt
(O
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FIGURE 4
GENERAL SCHEMATIC SITE GEOLOGY
SHERIDAN DISPOSAL SERVICE
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Ground water in the water table and confined aquifers generally flews towards
the river, in a northwestern direction. However, during high river stage
conditions (less than about one third of the time) ground water flow in the
water table aquifer may shift to the west and south. The predominant vertical
hydraulic gradient is upwards from the confined aquifer towards the water
table aquifer.
5.3 SAMPT.TNG RESULTS
A. Soil and Sludge
The results of the soil and sludge sainpling may be found in the site Source
Control RI/FS and risk assessment. Both organic and inorganic (metal) contar.-
inants were detected at the site. The most significant contaminants in terns
of toxicity and mobility are PCBs, benzene, toluene and trichloroethylene.
A summary of this information is found in EPA's ROD dated December, 1988.
B. Surface Water
Sampling of the Brazos River downstream and upstream of the site indi-
cated that there was no measureable difference in water quality between
the downstream and upstream samples. Sediment samples were also obtained
from the river bottom at locations downstream and upstream of the site.
Concentrations of organic constituents indicated that the site had not
impacted the sediment however, concentrations of metals were slightly
higher in the downstream sample than the upstream sample. Analyses of
Clark Lake water and sediments do not exhibit elevated levels of site
contaminants.
C. Ground Water
Over thirty wells have been installed at the site in both the shallow and
deep aquifers to determine the extent of contamination and evaluate site
hydrogeology. Table 2 shows the highest levels of contaminants detected
in the shallow wells to date and Figure 5 illustrates the extent of con-
tamination in the shallow aquifer. No contamination has been detected in
the deep aquifer. The only significant group of contaminants identified
in the shallow ground water are volatile organics. However, the Maximum
Contaminant Level (MCL) for arsenic was exceeded in one well by .01 ppm
during one sampling period. The highest concentration of contaminants
detected during recent sampling was benzene, at 130 ppb.
D. Air
Extensive air sampling has been completed at the site. No priority pollu-
tant constituents were detected at concentrations above ambient background
levels.
VI. SUMMARY OF SITE RISKS
The assessment of risk posed by the Sheridan site was evaluated in the
Sheridan Risk Assessment. This assessment examined the amount, concentra-
tion, properties, and environmental fate and transport of chemical found at
the site; the populations and environments potentially at risk; exposure
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pathways; and potential exposure events. The document described the risks
associated with current and future (probable and worst-case) exposure scena-
rios. The numerical cancer risk values discussed below are theoretical
quantifications of the excess lifetime cancer risk, that is, the increased
probability of contracting cancer as a result of exposure to wastes, canpared
to the probability if no exposure occurred. For example, a 10~° excess
cancer risk represents an exposure that could result in one extra cancer
case per million people exposed.
Three scenarios were developed in the site risk assessment. The first scenario
evaluated is for current conditions which assume restricted site access and
maintenance of the site. The second scenario addresses the risks associated
with the most probable future land use conditions. These conditions assume
continued agricultural (rangeland) use and unrestricted access to wastes. The
third scenario describes the risks associated with the worst-case future
scenario of residential development adjacent to the waste areas.
Under current conditions which assume restricted site access and maintenance
of the site, the only potentially significant pathway is migration of contam-
inants into the Brazos River. This pathway was modelled using very conserv-
ative assumptions, resulting in an upper bound excess cancer risk from the
ingestion of PCEs in fish of 1.5 X 10~5 (1.5 excess cancer cases per 100,000
people exposed). Modelling using less conservative assumptions indicated that
the 1 X 10~6 excess cancer risk would not be exceeded. However, it should
be noted that both models assume essentially all of the source will leach
into the ground water over time; This is not expected to occur since the
majority of contamination will be" addressed by the Source Control remedy.
The second scenario evaluated was the most probable future land use which
assumed continued agricultural (rangeland) land use and unrestricted access to
the waste disposal area. This scenario differs from the first only with
regard to exposure to lagoon sludges which is addressed in the Source Control
ROD. Therefore, the risks associated with this scenario are identical to the
first.
The last scenario evaluated in the Risk Assessment is the worst-case scenario
of residential development adjacent to the waste areas. The pathway pre-
viously described for the current-use scenario of migration of contaminants
into the Brazos River would be similar in the residential scenario. However,
an additional exposure pathway of ingestion of contaminated ground water
would result in a total excess cancer risk greater than 1 x 10~3 as well
as a significant non-carcinogenic risk posed by phenol (Hazard Risk 1 of 15).
Phenol is potentially the most significant non-carcinogenic contaminant which
could could impact ground water.
The preceding paragraphs describe potential impacts to human health.
Analyses of water and sediments in the Brazos River indicate that the
ground water is not adversely impacting potential environmental receptors
in the Brazos River.
1 The risk for a non-carcinogenic compound is described by a Hazard Index.
A hazard index is the ratio of the contaminant concentration to EPA's reference
dose for the contaminant. A value greater than one indicates that the ambient
concentration of a contaminant is higher than the acceptable reference dose,
and may be significant.
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The actual or threatened releases of hazardous substances from the site
described above, if not addressed by implementing the response action
selected in this ROD, may present an imminent and substantial endangerment
to public health, welfare, or the environment.
VII.
7.1 EVALUATION CR
In accordance with Section 121 (a) , (b) , and (d) of the Comprehensive
Environmental Response, Condensation, and Liability Act (CERCIA) , 42 USC
Section 9621 (a) (b) and (d) , EPA has determined that nine factors must be
considered in selecting a remedy for a Superfund site. Two of the criteria,
Protection of Human Health and the Environment and Consistency with Other
Laws, are known as Threshold Criteria which must be met. Long-term Effec-
tiveness and Permanence, Reduction of Toxicity, Mobility, or Volume, Short-
term Effectiveness, Implementability and Cost are considered to be Primary
Balancing Criteria. Modifying Criteria include State Acceptance and
Community Acceptance. These criteria are summarized below:
A. Overall Protection of Human Health and the Environment
Following the analysis of the remedial options against individual
evaluation criteria, the alternatives are assessed from the standpoint
of whether they provide adequate protection of human health and the
environment.
B. Consistency with Other Environmental Laws
In determining appropriate remedial actions at Superfund sites, considera-
tion must be given to the requirements of other Federal and State environ-
mental laws, in addition to CERCLA as amended by SARA. Primary considera-
tion is given to attaining applicable or relevant and appropriate Federal
and State public health and environmental laws and regulations and stan-
dards. Not all Federal and State environmental laws and regulations are
applicable to each Superfund response action. The compliance of each
remedial alternative with all applicable or relevant and appropriate
environmental laws is discussed in Appendix C.
C. Long-term Effectiveness and Permanence
Alternatives are assessed for the long-term effectiveness and permanence
they afford along with the degree of certainty that the remedy will
prove successful. Factors considered are:
o Magnitude of residual risks in terms of amounts and concentrations of
wastes remaining following implementation of a remedial action, consider-
ing the persistence, toxicity, mobility, and propensity for bioaccumula-
tion of such hazardous substances and their constituents;
o type and degree of long-term management required, including monitoring
and operation and maintenance;
o potential for exposure of human and environmental receptors to remaining
waste considering the potential threat to human health and the environ-
ment associated with excavation, transportation, redisposal, or contain-
ment;
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o long-term reliability of the engineering and institutional controls,
including uncertainties associated with the land disposal of untreated
wastes and residuals; and
o potential need for replacement of the remedy.
D. Reduction of Toxicity, Mobility or Volume
The degree to which alternatives employ treatment that reduces toxicity,
mobility or volume must be assessed. Relevant factors include:
o the treatment processes the proposed solutions employed and materials
they treat;
o the amount of contaminated materials that will be destroyed or treated;
o the degree of expected reduction in toxicity, mobility, or volume;
o the residuals that will remain following treatment, considering the
persistence, toxicity, mobility, and propensity for bioaccumulation
of such hazardous substances and their constituents.
E. Short-term Effectiveness
The short-term effectiveness of an alternative must be assessed consider-
ing the following:
o Magnitude of reduction of existing risks; and
o short-term risks that might be posed to the cctnmunity, workers, or
the environment during the implementation of an alternative including
potential threats to human health or the environment associated with
excavation, transportation, and redisposal or containment.
F. Implementability
The ease or difficulty of implementing the alternatives are assessed by
considering the following factors;
o Degree of difficulty associated with constructing the solution;
o expected operational reliability of the treatment technology;
o need to coordinate with and obtain nrcessary approvals and permits
(or meet the intent of any permit in the case of Superfund actions) ;
o availability of necessary equipment and specialists; and
o available capacity and location of needed treatment, storage, and
disposal services.
G. Cost
The types of costs that should be assessed include the following:
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o Capital costs;
o operation and maintenance costs;
o net present value of capital and operation and maintenance cost; and
o potential future remedial action costs.
H. State Acceptance (through the Texas Water Commission)
Evaluation includes assessment of:
o Ccrrponents of remedial alternatives that the State supports;
o features of the alternatives about which the State has reservations; and
o elements of the alternatives which the State strongly opposes.
# k
I. Community Acceptance
This assessment should evaluate:
o Conponents of remedial alternatives that the connunity supports;
o features of the alternatives about which the community has
reservations; and
o elements of the alternatives which the canmunity strongly opposes.
EPA is also directed by SARA to give preference to solutions that utilize
treatment to remove contaminants from the environment. Offsite transport
and disposal without treatment is the least preferred option where prac-
ticable treatment technologies are available.
In conformance with the National Contingency Plan (NCP), initial remedial
approaches were screened to determine which might be appropriate for this
site (see the Sheridan Disposal Services GWMM Feasibility Study for details
of this evaluation). Fran these possible remedies, three were chosen for
more detailed evaluation and comparison with the remedy selection criteria
outlined above. In addition, "No Action" was evaluated to cctrply with the
requirements of the NCP. Each remedy is summarized below.
All of the alternatives have some parts in common. They all require ground
water monitoring to track the position of the plume of contamination.
Additionally, all alternatives include the use of institutional controls to
prevent the use of contaminated ground water. Finally, in the two alterna-
tives which involve ground water treatment, ground water will be treated to
meet ARARs and discharged into the Brazos River.
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Alternative 1 - Natural Attenuation
This alternative relies on lowering contaminant concentration through natural
processes such as sorption, dispersion and biodegradation. Surface water mon-
itoring in the Brazos River will also be conducted to ensure that protective
levels are maintained in the river. It will require a minimum of thirty
years for contaminants at the upgradient edge of the plume to move through
the hydrcgeologic system. The cost of this alternative is approximately
$326,000.
Alternative 2 - Partial Slurry Wall with Ground Water Treatment
This alternative involves the construction of a 65 foot deep low permeability
slurry wall at the dcwngradient edge of the contamination plume (Figure 6).
The slurry wall will intercept contaminated ground water and channel it
towards extraction wells located at the center and ends of the slurry wall.
Contaminants in the extracted ground water will be treated onsite by passage
through a granulated activated carbon (GAG). It is expected to take approxi-
mately 25 years for ground water at the upgradient edge of the plume to reach
the slurry wall for recovery and treatment. The cost of this alternative
is approximately $4.2 million dollars.
Alternative 3 - Recovery Wells with Ground Water Treatment
This alternative involves placement of a line of wells near the downgradient
edge of the contamination plume (Figure 7). Ground water will be extracted
by these wells and treated onsite by passage through GAG. It is expected
to take about 25 years for contaminated ground water at the far edge of the
plume to be recovered by the wells and treated. The cost of this alternative
is estimated to be about $5.3 million dollars.
It should be noted that the cleanup timeframes described for the alternatives
described above are based on the time necessary to move one pore volume of
contaminated ground water through the aquifer and do not account for desorp-
tion of contaminants bound to the aquifer. These tiroeframes will be consider-
able longer (i.e., 90 years) since additional pore volumes of ground water
are expected to be necessary to remove contaminants bound to the aquifer.
Alternative 4 - No Action
The No Action alternative does not provide for any capital improvements or
other activities to address the ground water contamination. With no action,
potential exposure to contaminated ground water is not prevented and poten-
tial impacts on the river not controlled. However, Superfund regulations
require that this alternative be evaluated as a basis for comparison to
other alternatives.
7.3 EVALUATION OF ALTERNATIVES
The following values were assigned to compare remedial selection criteria:
"+" Alternative should exceed a criterion in conparison to other
alternatives.
"." Alternative should meet the selection criterion.
"-" Alternative will not meet a criterion, or will not meet a
criterion as well as other alternatives.
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10
The rationale for the ratings assigned each alternative is presented in the
following subsections.
A. Compliance with Applicable or Relevant Appropriate Requirements f ARARs) of
Oth^r Tays
The No Action Alternative is accorded a rating of "-" due to the inability to
monitor the ground water and determine whether ARARs are continuing to be met
for the long term. The Alternatives 1, 2, and 3 all meet ARARs and are rated
it n
• •
B. Reduction of Mobility. Toxicity and Volume
The processes of natural attenuation such as bicdegradation, sorption and
dispersion, may reduce the toxicity, mobility and volume of waste constituents
For this reason, Alternatives 1 and 4 are ranked ".". The alternatives
which involve ground water recovery (Alternatives 2 and 3) include ground
water treatment and thus reduce the mobility, toxicity and volume of the
ground water. These alternatives are given a rating of "+". However, it
should be noted that at the design flow rate and composition of the treatment
scheme proposed for Alternatives 2 and 3, less than eight pounds of total
contaminants would be removed in the first year and this quantity would
very likely decrease with time.
C. long-Term Effectiveness and Permanence
The No Action alternative is ranked "-" due to the inability to monitor
whether ARARs are continuing to be met or prevent the use of contaminated
ground water for the long term. In the long-term, the concentrations of
constituents will be reduced by natural processes, therefore Alternative 1
is accorded a ranking of ".". Alternatives 2 and 3 will be slightly more
effective at reducing the concentrations of constituents in the long-term.
Therefore, both 2 and 3 are rated "+".
D. Short-Term Effectiveness
The No Action alternative is ranked "-" due to the inability to prevent
ground water use before attenuation takes place. The Natural Attenuation
Alternative, for the short-term, is equally effective as Alternatives 2 and
3 since the institution of controls will prevent exposure to contaminated
ground water. For this reason, Alternative 1 is ranked ".". However,
alternatives 2 and 3 will cause onsite workers to be exposed to additional
potential risk since these alternatives include active construction and
operation activities. Therefore, Alternatives 2 and 3 are ranked "-".
E. Implementability
Alternative 1 and 4 would be the roost easily implemented and are rated "+".
Between the remaining alternatives, Alternative 3 is more easily implemented
than 2. Alternative 3 is rated ".", since it requires construction of wells
and a treatment plant. Alternative 2, partial slurry wall with ground water
treatment, is rated "-" due to the difficulties in constructing a slurry
wall considering the site constraints. Site constraints include a narrow
strip of land for access, the fact that a trench of 65' depth is beyond the
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11
reach of normal trenching equipment and a new working "bench" would need to
be constructed.
F. Cost
Table 3 summarizes the cost of the alternatives as developed in detail in
Section 6.3 and Appendix C of the feasibility study. Costs are presented
as capital, operation and maintenance, present value and total cost. The No
Action and Natural Attenuation alternatives (4 and 1) are the least costly alternat
and are both ranked "+". Alternative 2 is intermediate in terms of cost and
is rated ".". Alternative 3 is the most costly alternative and is therefore
rated "-".
G. Overall Protection of Human Health and the Environment
The No Action alternative is ranked "-" due to the inability to prevent
potential use of affected ground water and lack of monitoring. Alternative 1
is ranked "." since the seepage of ground water into the Brazos River under
current and projected future conditions will result in concentration levels
which are protective of human health and the environment. In addition,
institutional controls would effectively prevent use of the affected ground
water. Alternatives 2 and 3 are equivalent to Alternative 1 in terms of
overall protection of human health and the environment 'and are therefore
rated ".". The reasons for this ranking are discussed below:
The shallow ground water recovery rate is relatively low, therefore with-
drawal of one pore volume of ground water will require about 25 years.
Since extraction of multiple pore volumes would probably be necessary to
achieve drinking water criteria (MCLs), it is anticipated that treatment
would continue for some multiple of 25 years. During this relatively long
time period, the shallow ground water would not meet drinking water criteria
and could not be used as such. Institutional controls would be maintained
for this period to prevent potable use of the shallow aquifer. Therefore,
Alternatives 1, 2 and 3 all require long-term institutional controls to
prevent use of the shallow aquifer.
H. Community Acceptance
The community has voiced limited support for the Natural Attenuation alterna-
tive and has not expressed any concerns about the alternative. Therefore
natural attenuation is rated "+" and all other alternatives are rated ".".
I. State Acceptance
The State of Texas, through the Texas Water Commission, has indicated that
they have no objection to the selected alternative. Therefore, Natural
Attenuation is rated "+" and all remaining alternatives are rated "0".
Analysis
As described above, alternatives 1, 2 and 3 are fully protective of public
health and the environment. All of the alternatives except No Action could
also be implemented to comply with all ARARs. With regard to the balancing
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criteria, alternatives 2 and 3, make a slight reduction of toxicity of the
affected ground water, but the reduction is very small, and the resulting
decrease in surface water concentrations would not be detectable. Further-
more, these alternatives concentrate waste constituents on GAC, which must
eventually be disposed of. The more costly alternatives (Alternatives 2
and 3) , are generally more difficult to implement and may pose more short-
term risks to onsite workers. Finally, Alternatives 2 and 3 will not appre-
ciably decrease the time necessary to achieve MCLs.
VIII.
Based on the information provided in the administrative record and the results
of the evaluation of alternatives (Section 5.3) , the "final" remedy has been
selected. It is EPA's judgement that Alternative 1, Natural Attenuation,
best satisfies both the statutory and selection criteria in comparison to
the other alternatives evaluated in this document. This remedy is consistent
with the remedy selected for the Source Control operable unit.
8.1 DESCRIPTION OF SELECTED REMEDY
A. Establish Alternate Concentration Limits (ACLs) as -the Ground Water
Protection Standard
EPA has selected ACLs as the apprpriate ground water standard for the site
as long as the conditions set forth below remain valid. ACLs are ground
water protection standards that are used to assure that hazardous
constituents found in the ground water do not pose a risk to human
health or the environment. To ensure that Ads remain protective,
the following conditions must continue to be met at the site:
a. The Brazos River must remain the discharge point for ground water from
the site.
b. The Brazos River cannot be adversely impacted by the discharge of
contaminated ground water into the river. Presently, no adverse
impacts to the river from the site have been observed. To ensure
that future adverse impacts from the site do not occur at the point
of exposure for environmental receptors in the river, river water
will be sampled to ensure that there is no statistically significant
increase in contamination, as compared to upgradient locations.
c. The ground water use restrictions outlined below must be implemented
and continued to ensure that affected ground water is not consumed
and the integrity of the Brazos River as a hydraulic barrier to
ground water flow is maintained.
If any of these conditions change, the situation will be reevaluated and
appropriate action taken. The specific provisions for setting the ACLs are
outlined below.
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13
ACL Contaminants and Concentrations
EPA has set Ads for the contaminants detected in the ground water in order
meet drinking water criteria in the Brazos river. These values were calculated
by determining the volume of affected water entering the river at any time and
factoring in the dilution which would occur in the river at historical low
flow conditions.
These Ads are listed below:
Caiipuund Ad (pan)
Benzene 26
Tetrachloroethylene 41
Trans-1,2 dichloroethylene 26
Trichloroethylene 26
Arsenic 260
If additional contaminants are detected in the ground water in the future,
Ads will be developed for them using the methodology described in the F.S.
Point of Compliance
The point of conpliance is the location where Ads mist be met and is also
the well location where ACLs are monitored. At the point of compliance, Ads
will be met at concentrations that ensure that human health and the environment
are protected at the point of exposure and that no statistically significant
increase in contamination occurs in the river.
The specific locations for the point of carpliance monitoring, based on the
existing position of the ground water plume, are around the boundary of the
lagoon and are designated as well numbers 34 and 35 as illustrated in Figure 8.
If the plume position changes additional conpliance points may be identified.
Point of Exposure
A point of exposure is a location where environmental or human receptors may
be exposed to or use ground water. Exposure to ground water at that point
cannot result in an endangernent to human health or the environment. At the
Sheridan site, the point of exposure will be the interface of ground water
and the Brazos River (i.e., where offered ground water comes into contact with
the river). It will be monitored by the collection of water samples from the
Brazos River at the projected point, or points of entry of affected ground
water from the site.
Ground Water Use Restrictions
Ground water use at the site will be restricted to ensure that contaminated
ground water is not consumed and that the hydraulic barrier that the Brazos
River provides is not affected. Ground water use onsite will be restricted
within a minimum of 100 feet from the edge of the plume of contaminated
ground water. In addition, the use of any well (other than that employed as
part of a corrective action) which could potentially affect the size or
position of the plume of ground water contamination is prohibited.
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14
The ground water use restrictions which will be implemented are deed notices
recorded in the county clerks office. These restrictions are expected to
be reliable and effective for the following reasons.
1. The area of attainment (ground water contamination plume exclusive of the
area beneath the lagoon) is limited to a narrow strip of land between the
waste lagoon and the river, and is located entirely onsite, on the land
owner/former operator's property.
2. The yield of the aquifer is too low to be of agricultural use, which is
the most likely potential use.
3. The land owner/former operator is a signatory to a proposed Consent Decree
which states that he will not take any actions at the site without getting
prior written Consent from EPA. In addition, the terms of any sale of
the site property must contain a provision requiring compliance with the
consent decree.
4. There will be, at the minimum, annual monitoring of site conditions to
verify that the restrictions are effective.
EPA has enforcement authority to ensure that the remedy selections for the
source control and GWMM operable units are implemented and that no one
interferes with remedy implementation. If any of the conditions listed above
should change, the existing situation will be evaluated and appropriate action
will be taken to prevent potential use of contaminated ground water.
Ground Water Monitoring
Ground water will be monitored to ensure compliance with Ads and the three
conditions listed at the beginning of Section 8.1. Compliance monitoring will
be conducted quarterly for the first year. The frequency of monitoring may
then be modified by EPA.
The first time an ACL for a particular contaminant is exceeded, the well will
be resampled. If the second analysis confirms that the Ads are being exceeded,
EPA will determine whether the corrective action program outlined below will
be implemented.
Finally, additional wells will be monitored quarterly to ensure that the Brazos
River continues to act as a discharge point and hydrological barrier to ground
water flow. The monitoring frequency of these wells may be modified by EPA.
Surface Water Monitoring
The surface water from the Brazos River will be monitored to ensure that
there i- no statistically significant increase in contamination due to the
ground water recharge to the River. Samples will be obtained in the river
immediately adjacent of the point of projected entry of effected ground water
and upgradient of the site.
B. Corrective Action and Contingency Planning
In. the event Ads are exceeded, if any of the three conditions outlined
at the beginning of section 8.1.A. are not met, or if changes in receptors
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15
40 C.F.R. §264.100 will be implemented. As part of the design of the
remedial action, a corrective action contingency plan will be developed.
Under the corrective action program, contaminated ground water will be
extracted and treated, or other necessary and appropriate action will be
undertaken, to reduce contaminant levels to ensure that Ads are not exceeded
at the compliance point and that the remedy is protective of human health
and the environment at the point of exposure.
If ground water needs to be treated at the site, different process options,
including a combination of treatment technologies, will be considered during
the design of the treatment system. The process presented in the FS for the
pump and treat alternatives is one possible process configuration that could
be utilized. During design of the treatment system, the particular tecology
or technologies will be chosen on the basis of performance goals that EPA
sets for the treatment system.
C. Monitoring, Operation and Maintenance (MCM)
1. The site will be secured to meet the requirements of 40 C.F.R. §264.14
during post-closure.
2. The ground water monitoring system will be monitored and maintained to
comply with the requirements of 40 C.F.R. Part 264, Subpart F.
3. A written MCM plan will be developed to define the activities which
will be necessary to ensure the remedy will continue to be effective.
Additionally, because hazardous substances will remain on-site, EPA will re-
evaluate this site at least once every five years after the commencement of the
remedial action to assure that human health and the environment continue to be
protected.
8.2. RATIONALE FOR SELECTION OF THE REMEDY
In accordance with Section 121 of CERCLA, to be considered as a candidate for
selection, an alternative must be protective of human health and the environment
and attain ARARs. For ground water, attainment of ARARs requires that a ground
water protection standard be set at either Maximum Contaminant Dsvels (MCLs),
ACLs or at background levels. To meet the ground water protection standards,
both pump and treat and natural attenuation alternatives were evaluated.
Because Alternative #4, No-action, is not protective and does not attain ARARs,
it was rejected from further consideration.
The remaining three alternatives, which utilize natural attenuation or ground
water recovery and treatment, all meet the statutory threshold criteria of
protectiveness and attainment of ARARs. To select among them, EPA focused on
other criteria, including: short-term effectiveness, long-term effectiveness,
implementability, reduction of mobility, toxicity or volume of waste, community
acceptance and State acceptance.
The advantages of the ground water recovery and treatment alternatives is that
they will achieve safe levels more quickly and utilize treatment to permanently
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16
reduce the toxicity of contaminants. However, the magnitude of these potential
benefits is quite small; the cleanup timeframes are estimated to be about 10-15%
(i.e., 15 vs. 90 years) faster than for natural attenuation, and a maximum of
eight pounds per year of total contaminants will be treated annually by sorption
onto GAC.
The first disadvantage of the ground water recovery and treatment alternatives
(Alternatives 2 and 3) is that their operation and maintenance poses greater
potential short-term risk to on-site workers during construction and operation
of the extraction and treatment systems. Second, Alternative 3 (recovery wells),
and to an even greater extent alternative 2 (partial slurry wall), are more
difficult to implement than natural attenuation. Third, the costs of alterna-
tives 2 and 3 are between ten and twenty times greater than the costs of natural
attenuation. Finally, the State and the coununity have expressed limited support
of the natural attenuation alternative. In light of these considerations, EPA
has determined that Alternative 1, Natural Attenuation, best satisfies
the nine criteria for remedy selection.
As discussed in the description of the Selected Remedy, the natural attenuation
alternative requires the implementation and enforcement of Ads as the appropriate
ground water protection standard for ground water in the area of attainment.
The rationale for selection of this standard is described in the paragraphs
which follow.
Under RCRA regulations, the ground water protection standard establishes a safe
level of contamination in ground water in the vicinity of a waste disposal
site. Under these regulations, the protection standard can be set at Mds,
ACLs, or at background levels. Ads are based on the premise that, although
ground water is contaminated around a waste disposal site, at a point where a
potential receptor may come into contact with ground water, levels of contami-
nants are not found at unsafe levels. At locations where exposure to ground
water may not be safe, enforceable controls to prevent exposure may be imple-
mented. At the Sheridan site, that basic premise is satisfied. Ground water
around the site is contaminated, however, the river and other site features
contain and attenuate contamination in the ground water to protective levels
and enforceable controls can be implemented.
In addition to the RCRA requirements, under Section 121(d)(2)(B)(ii) of CERCIA,
42 U.S.C. §9612(d)(2)(ii), EPA may not establish ACLs as the ground water
protection standard for a Superfund site if human exposure to hazardous consti-
tuents will occur beyond the site boundary (as that boundary is defined in the
RI/FS), unless EPA had determined that:
a. there are known or projected points where the ground water will enter
into the surface water;
b. there is or will be no statistically significant increase in the level
of hazardous constituents in the surface water at the points of entry
of contaminated ground water into the river.
c. the remedial action includes enforceable remedial measures to preclude
human exposure to ground water between the site boundary and all known
or projected points of entry.
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The RCRA requirements and the CERCLA prerequisites for an ACL are met at the
Sheridan site because of the following reasons:
1. The ground water characterization study completed in the RI concluded the
Brazos River is a hydraulic barrier. Contaminated ground water from the
site discharges into the river. Thus, there are known or projected points
where site ground water will enter into the river.
2. Sampling and analysis conducted by EPA indicates that the Brazos River acts
as a hydrologic barrier that will tend to dilute and disperse contaminants.
Sampling also indicates that there is no statistically significant increase
in hazardous constituents in the river which can be attributed to the site.
3. Ground water that is contaminated by the site is not currently used as a
source of drinking water. Deed recording, when applied in conjunction with
the assumptions described in Subsection 6.1.A., will be used to ensure that
contaminated ground water is not consumed.
4. Because the impermeable cap required by the Source Control ROD will prevent
infiltration of rainwater into the waste lagoon, flushing of lagoon contami-
nants into ground water will be significantly decreased in the long-term.
5. The setting of ACLs for individual contaminants at the points of compliance
will ensure that human and environmental receptors are not exposed to unsafe
levels of contaminants at the points of exposure. In the event an ACL for
an individual contaminant is exceeded, corrective action at the site will
be implemented consistent with Section 6.1. Thus, setting ACLs provides
EPA with an enforceable mechanism that sets into motion corrective action.
ACLs will be effective and protective of human health and the environment in
the long-term. Although the development of ACLs as the ground water protection
standard will not reduce contaminants in ground water, their enforcement will
ensure protection of public health and the environment at each and every point
of exposure. Further, the corrective action program will ensure that the
remedy continues to be effective.
Alternatives 2 and 3 which call for pumping and treating ground water, are no
more protective than the selected remedy because they will still require the
implementation of controls to prevent the use of ground water until safe levels
are met. Furthermore, site conditions may prevent the attainment of MCLs within
a reasonable timeframe. These conditions include 1) the potential for continued
leaching of contaminants sorbed to the aquifer (particularly clay layers) 2)
the low hydraulic gradient across the site and the potential that capping the
lagoon area as required by the Source Control ROD may further reduce these
gradients, and 3) the low yield and small radii of influence of pumping wells
in the affected aquifer. In view of these conditions, EPA has determined that
cleanup to MCLs is not practicable. Therefore, the development and enforcement
of ACLs is necessary. However, pumping and treating ground water may be imple-
mented under the corrective action plan to ensure that ACLs are not exceeded.
DC. STATUTORY DETERMINATIONS
Under its legal authorities, EPA's primary responsibility at Superfund sites is
to undertake remedial actions which are protective of human health and the
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environment. In addition, Section 121 of CERCLA established several other
statutory requirements and preferences. These specify that when complete, the
selected remedial action for this site must comply with applicable or relevant
and appropriate environmental standards established under Federal and State
environmental laws unless a statutory waiver is justified. The selected remedy
also must be cost-effective and utilize permanent solutions and alternative
treatment technologies or resource recovery technologies to the maximum extent
practicable. Finally, the statute includes a preference for remedies that
employ treatment that permanently and significantly reduce the volume, tenacity,
or mobility of hazardous wastes as their principal element.
9.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy protects human health and the environment through the
implementation of ground water use restrictions on-site and the enforcement of
ACLs to ensure safe levels are maintained at the first point of potential
exposure in the Brazos River. The implementation of the selected remedy will
effectively reduce any potential excess cancer risk associated with ingestion
of contaminated ground water.
9.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARs)
The selected remedy will attain all applicable or relevant and appropriate
federal and state environmental requirements at the site. Federal environmental
laws that are applicable or relevant and appropriate to the selected remedial
action at the site include the:
- Resource Conservation and Recovery Act (RCRA);
- Clean Water Act (CWA) ;
- Safe Drinking Water Act (SDWA); and
- Executive Order 11988 (Floodplain Management)
State environmental laws that are applicable or relevant and appropriate to the
selected remedial action at the site are:
- Texas Clean Air Act; and
- Texas Administrative Code Relating to State Water QAiality Standard
A discussion of how the selected remedy meets those requirements follows.
Ground Water
RCRA ground water protection standards (GWPS), 40 C.F.R. Part 264, Subpart F,
are established for constituents entering ground water from a regulated hazardous
waste unit. Although RCRA is not applicable to the Sheridan site, the waste
lagoon presents problems that are similar to those ^hat the requirements address,
and thus, the requirements are relevant and appropriate. Ground water protection
standards under the RCRA regulations are set at MCLs, ACLs, or at background
levels. Because the Brazos River acts as a hydrologic barrier for site ground
water, EPA has determined that ACLs are the relevant and appropriate standards
at the site. If hydrogeologic conditions at the site change significantly and
contaminated ground water was to no longer discharge to the Brazos then MCLs,
promulgated pursuant to the Safe Drinking Water Act, are ARARs. These standards
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are relevant and appropriate for ground water at the point where exposure to
ground water may occur.
Surface Water
The reach of the Brazos River adjacent to the site is classified by the State
as suitable for public water supply and recreational use. Therefore, Mds and
State and Federal Water Quality Criteria pronulgated pursuant to the Clean Water
Act are relevant and appropriate in the Brazos River. Further, all actions
will meet the applicable requirements of 31 Texas Administrative Code Sections
329, 21-29, 307.1 to 307.10. Finally, if corrective action is required, all
discharges will be treated to satisfy the requirements of the Clean Water Act
application of best available technology (BAT) and best conventional technology
(BCT).
Air
If a corrective action is required, the treatment facility will be designed to
meet the requirements of Section 4.01 of the Texas Clean Air Act.
Post-Closure Care
Monitoring of ground water will be conducted in accordance with the relevant
and appropriate RCRA ground water monitoring requirements under 40 CFR Part
264, Subpart F. In addition, site reviews will be conducted at least once every
five years to ensure that the remedy is continuing to be protective of human
health and the environment.
Corrective Action and Contingency Planning
If a ground water corrective action becomes necessary then these activities
will be conducted in accordance with the corrective action regulations 40 CFR
Section 264.100. Such action will also be conducted in accordance with any
relevant and appropriate requirements of the general facility standards in 40
CFR part 264, Subpart B.
9.3 ODST-EFFECJL'IVENESS
The selected remedy is cost-effective because it has been determined to provide
overall effectiveness proportional to its costs, the net present worth value
being $194,000. It is the least costly alternative which is fully protective
of human health and the environment and attains ARARs.
9.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE TREATMENT TECHNOLOGIES
(OR RESOURCE RECOVERY TECHNOLOGIES) TO THE MAXIMUM EXTENT PRACTICABLE
EPA has determined that the selected remedy represents the maximum extent to
which permanent solutions and treatment technologies can be utilized in a cost-
effective manner for the GWMM operable unit at the site. Of those alternatives
that are protective of human health and the environment and comply with ARARs,
EPA has determined that the natural attenuation alternative provides the best
balance of tradeoffs in terms of balancing and modifying criteria for remedy
selection. As described in section 6.2, it is not practicable to treat ground
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water because pumping and treating the ground water will not appreciably decrease
the cleanup timeframes compared to natural attenuation. Further, attaining
drinking water standards in, for exanple, 75 years, is highly unlikely due to
site-specific hydrogeological conditions which include low ground water flow
velocities and the presence of numerous clay strata which may act as a continu-
ing source of contaminants to ground water.
9.5 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The operable unit does not utilize treatment to address the principal threat
posed by the contaminated water because the implementation of treatment alter-
natives was found to not be practicable, due to site-specific constraints.
However, the Source Control POD utilizes treatment to address contaminated
soils and sludges which act as a source of contaminants to ground water. The
quantity of contaminants which could potentially be treated in ground water
(a maximum of 8 pounds per year) is very small when corpared to approximately
500,000 pounds of contaminants which will be treated as part of the source
control remedy.
X. DOCUMENTATION OF NO SIGNIFICANT CHANGES
EPA issued a Proposed Plan (preferred alternative) for remediation of the
site on July 31, 1989. The selected remedy does not differ from the Proposed
Plan.
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(Available upon request!
APPENDIX A
ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME: SHERIDAN DISPOSAL SERVICE
SITE NUMBER: TXD 062132147
INDEX DATE: 09/29/89
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APPENDIX B
SHERIDAN DISPOSAL SERVICES
cm-ram RELATIONS RESPONSIVENESS SUMMARY
This Community Relations Responsiveness Summary has been prepared to provide
written responses to comments submitted regarding the proposed plan of action for
the ground- water portion of the Sheridan Disposal Services hazardous waste site.
The Summary is divided into two sections:
Section I. Background of Ccnmunitv Involvement and Concerns. This section
provides a brief history of cotimunity interest and concerns raised during
the remedial planning activities at the Sheridan site.
Section II. Summary of Major Conments Received. Any written or oral comments
are summarized and EPA's responses are provided.
I. Background
In general, there has been a long history of citizen awareness of the
Sheridan Disposal Services site. In the early 1970s when incineration at
the site resulted in air emissions, people living within a 7-mile radius
complained. In 1971 a citizens' group submitted a petition with over 500
signatures to the Texas Water Duality Board calling for its closure.
However, community concerns of either the area residents or local officials
are now very low, probably because the site has been inactive since 1984.
Also the site is relatively remote and there are no residences within a mile.
II. Summary of Maior Comments Received
The proposed plan fact sheet announcing the public comment period and opportunity
for a public meeting for the ground water portion of the site was distributed on
July 31, 1989. The comment period began on August 14, 1989 and ended on September
11, 1989. No one responded to the offer of a public meeting and none was held. No
written comments or questions were received by EPA.
p»
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APPENDIX C
Garcia
Tipple
Feeley
Ferguson
Eden
Beinks
1400GG04.LTR
Septerrber 22, 1989
Allyn M. Davis, Ph.D., Director
Hazardous Waste Management Division
U.S. Environmental Protection Agency
Region VI
1445 Ross Avenue
Dallas, Texas 75202-2733
Re: Sheridan Disposal Service Superfund Site
Draft Record of Decision
Ground Water Migration Management Operable Unit
Dear Dr. Davis:
We have reviewed the proposed Record of Decision (ROD) for the
Sheridan Disposal Service Superfund site. We have no objection
to the selected remedy for the Ground Water Migration Management
Operable Unit as described in the draft ROD of September 15,
1989. The selected remedy described as the natural attenuation
alternative requires the establishment of Alternate Concentration
Limits (ACLs), ground water monitoring, sampling and analysis of
the Brazos River, implementation of controls to preclude the use
of contaminated ground water, and implementation of a corrective
action plan in the event that ACLs are exceeded at some tiae in
the future.
Sincerely,
Allen Beinke
Executive Director
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