June 1988
EP A-70 0/8-88-05 1cl
Hazardous Waste Ground-Water
Task Force
Evaluation of
Texaco Inc. Refinery
Casper, Wyoming
B.
mi UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

-------
UPDATE TO THE GROUNDWATER TASK FORCE REPORT
FOR
TEXACO, INC. REFINERY
EVANSVILLE, WYOMING
The Task Force report discusses conditions that were present at
the time of the August 1986 inspection. Listed below are
selected items pertaining to events which transpired after the
inspection during the period August 1986 to September 1988.
o During October 1986, Texaco began an aquifer recharge
and flushing program in an attempt to correct
contamination caused by the Chemical Evaporation Pond
(CEP). The program consisted of building a dike across
the southern third of the CEP and pumping North Platte
River water into the southern portion of the CEP for
infiltration into the aquifer below. Attached to this
report is an analysis titled "Effects of Chemical
Evaporation Pond Recharge" which is an analysis of the
aquifer recharge activities performed since October
1986. Recommendations of the analysis will be
addressed in the 3008(h) corrective action order issued
on September 30, 1988, and which is discussed later in
this update.
o On May 6, 1987, EPA issued a Land Treatment
Demonstration Permit to the Texaco Casper Refinery
pursuant to the requirements of 40 CFR 264.272.
o On June 15, 1987, Texaco submitted to EPA the "Casper
Plant North Landfarm Reconnaissance Investigation
Report" pursuant to Condition I. H. 2 of the Land
Treatment Demonstration Permit. The Report provided
soil analyses of landfarm soils which showed parts of
the landfarm to have elevated metal and oil levels.
o On December 1, 1987, Texaco submitted a letter to EPA
stating that pursuant to Condition III. D. 7. of the
Land Treatment Demonstration Permit they were reporting
a finding of contamination below the treatment zone in
their land treatment demonstration test plot.
o Further soil core investigations and analyses of the
landfarm were requested of Texaco by EPA on April 15,
1988 and May 9, 1988. These investigations were to
determine extent and rate of migration of hazardous
constituents in the landfarm soils. Texaco never
conducted the requested investigations.
1

-------
o Texaco was notified of EPA' s intent to deny an
operating RCRA permit on August 2, 1988. The action
was taken due to Texaco's failure to provide:
1) requested information, 2) permit application
information, and 3) a demonstrated ability to manage a
land treatment area in an environmentally safe manner.
o On September 29, 1988, EPA issued a unilateral RCRA
Section 3008(h) corrective.action order to Texaco for
facility wide site investigations, corrective measure
studies, and corrective measure implementation at the
Texaco Casper refinery.
o On September 30, 1988, EPA issued a final determination
on Texaco's application for a RCRA permit. Texaco's
application was denied and the facility was ordered to
cease receiving wastes.
2

-------
tconCajp
Table of Contents
Section	Page
I EXECUTIVE SUMMARY
A.	INTRODUCTION	1
1.	Task Force Effort	1
2.	Task Force Objectives	1
3.	Evaluation Procedures	1
B.	SUMMARY OF FINDINGS AND CONCLUSIONS	2
1.	Hydrogeology	2
2.	Ground-Water Monitoring System	3
a.	North Area Ground-Water Monitoring System	3
b.	South Area Ground-Water Monitoring System	8
3.	Task Force Sampling and Monitoring Data	10
4.	Compliance With Superfund Off-Site Policy	12
H TECHNICAL ASSESSMENT
A.	INVESTIGATIVE METHODS	13
1.	Records/Document Review	13
2.	On-Sitc Inspection	13
3.	Task Force Sampling Locations and Methods	13
B.	FACILITY HISTORY, OPERATIONS AND DESIGN	14
1.	Background	14
2.	Regulatory Background	18
3.	Facility Operations	20
4.	RCRA - Regulated Units	20
5.	Solid Waste Management Units	21
C.	HYDROGEOLOGY	28
1.	Regional Geologic Setting	28
2.	Regional Hydrologic Setting	28
3.	Site Geology and Hydrogeology	29
4.	Hydrogeology of the North Area	44
5.	Hydrogeology of the South Area	55
D.	GROUND-WATER MONITORING SYSTEM	61
1. Ground-Water Monitoring System under Interim Status	62
(North Area)
a.	History of Interim Status Monitoring	62
b.	Assessment Program under Interim Status	63
i

-------
ccon^asp
Table of Contents
Sect ion	Page
2.	Proposed Ground-Water Monitoring System under 40 CFR 264	96
(North Area)
a.	Detection Monitoring Program (North Land Farm)	97
b.	Corrective Action Program under 40 CFR 264.101 (CEP)	103
3.	Compliance with Applicable Regulations	105
a.	Interim Status Program	105
b.	Proposed 40 CFR 264 Ground-Water Monitoring Program	106
4.	Ground-Water Monitoring System (South Area)	108
a.	History	109
b.	Monitoring Well System Dcsign/Placement/Construction	118
(South Area)
-	Central South Area
-	Southeast Corner
c.	Adequacy of Ground-Water Monitoring System (South Area)	131
d.	Hydrocarbon Recovery System	132
E.	SAMPLING AND ANALYSIS	154
1.	Texaco	155
a.	Sampling and Analysis Plan Review	155
b.	Field Implementation - (Sampling Audit)	156
2.	Task Force	158
a.	Techniques of Sampling	158
b.	Interpretation of Data	167
3.	Data Comparison (Task Force and Texaco)	178
4.	Comparison to Past Texaco Data	187
F.	REFERENCES	189
Tables
Table
Number
1	Summary of Wastes Handled by Texaco	19
2	Hydrologic Data Arranged by Formation for Selected Water Wells	35
Within Two Miles of the Casper Texaco Refinery Vicinity
3	Hydrologic Properties, North Area Geologic Units	52
4	Vertical Potential Gradients Determined From Well Nests,	54
North Area
ii

-------
tconCajp
Table of Contents
Table
Number	Page
5	Select Physical Constants of Known Ground-Water Contaminants	66
6	Historic High, Low and Screened Interval Elevations (North Area)	67
7	Monitoring Well Specifications (North Area)	71
8	Technical Adequacy of Monitoring Wells (North Area)	79
9	Drilling Fluid Utilized (North Area Wells)	82
10	Monitoring Frequency of Wells on North Property for 1987	84
11	Organic Hazardous Constituents Detected in Groundwater, Casper	86
Plant North Property
12	Well Specifications - South Area	111
13	Water Quality Data, Casper Texaco Refinery South Area, September 1982	125
14	TOX and Priority Pollutants for the Excess Service Water Effluent	126
Ponds, Casper Texaco Refinery South Area
15	Summary of Refinery-Related Constituents Recovery Well Samples -	127
South Area
16	Oil Recovery System Design Specifications	139
17	Groundwater Quality/Dissolved Fraction Indicative of Recharge Water	152
Quality, Groundwater Task Force, August 1986
18	Task Force Analytical Parameters	159
19	Sampling Order, Bottle Type and Preservation Method, Task Force	162
20	Analytical Results, Ground-Water Task Force, August 11-15, 1986	172
21	Analytical Comparison, Ground-Water Task Force vs Texaco,	179
August 11-15, 1986
22	Analytes Reported by (Texaco) PARL Laboratory	178
iii

-------
tconOasp
Figures
Figure
Number
1	Facility Location Map
2	Facility Map
3	North Platte River Flooded Areas, Casper Texaco Refinery
4	Ages, Lithologics, Thickness, and Hydrologic Characteristics for
Sedimentary Rocks in the Casper Texaco Refinery Area
5	Diagrammatic Hydrostratigraphy of the Powder River Basin
6	Generalized Geologic Map Casper Texaco Refinery Area
7	Isopach Map of Alluvial Deposits in the South Area, Texaco
Casper Refinery
8	Bedrock Surface Contours, Unnamed Middle Member, North Property,
Casper Texaco Refinery
9	Generalized Potentiomctric Surface Contour Map and Idealized
Ground-Water Flow Directions for the Alluvial Aquifer, Casper
Texaco Refinery
10	Location of North Area Monitoring; Wells Texaco Refinery,
Casper, Wyoming
11	Potcntiometric Surface Map, Upper Aquifer, October 1982
(Approx. Historic High)
12	Potcntiometric Surface Map, Upper Aquifer, September 1985
13	Potentiometric Surface Map, Upper Aquifer, December 1985
(Approx. Historic Low)
14	Potentiometric Surface Map, Upper Aquifer, September 1987
15	Monitoring Well, Recharge Well and Recovery Well Locations,
South Area
16	Approximate Top of Bedrock Erosional Surface, Texaco Refinery
South Area, Task Force Analysis
17	Potentiometric Surface Map, South Area, 11-5-85 Recovery System
in Operation
18	Potentiometric Surface Map, Southeast Area, January 1987
15
16
17
30
31
32
39
40
41
45
47
48
49
50
56
58
59
60
iv

-------
tconCasp
Table of Contents
Figure
Number	Page
19	Location of Excess Service Water Effluent Ponds Monitoring Wells	64
(North Area)
20	Concentrations of Select Organic Constituents (ug/1) March 1984	93
(Texaco)
21	Concentrations of Select Organic Constituents (ug/1) June 1986	94
(Texaco)
22	Concentrations of Select Organic Constituents (ug/1) August 1986	95
(Task Force)
23	Location of North Landfarm Existing and Proposed Monitoring Wells	98
24	Monitoring Wells Capable of Detecting Light Phase Immiscible	119
Organics, South Area
25	Monitoring Wells Capable of Detecting Dense Phase Immiscible	121
Organics, South Area
26	Concentrations of Selected Organic Compounds in Ground-Water	130
Samples From Wells in and Near the Southeast Corner of the
Casper Texaco Refinery, October 1986
27	Anticipated Ground-Water Flow During Recovery (South Area)	135
28	As-Built Diagram of Recovery Well RW-1, Casper Texaco Refinery	136
29	As-Built Diagram of Recovery Wells RW-2, RW-3, and RW-4,	137
Casper Texaco Refinery
30	As-Built Diagram of Recharge Wells SS-46, 1-1, 1-2, 1-3, 1-4,	138
1-5, 1-6, 1-7, 1-8, Casper Texaco Refinery
31	Apparent Petroleum Thickness Contour Map, September 5-6, 1983	140
32	Apparent Petroleum Thickness Contour Map, December 9, 1983	141
33	Apparent Petroleum Thickness Contour Map, March 12, 1984	142
34	Apparent Petroleum Thickness Contour Map, September 3, 1984	143
35	Apparent Petroleum Thickness Contour Map, May 2, 1984	144
v

-------
tconoasp
Table of Contents
Figure
Number	Page
36	Apparent Petroleum Thickness Contour Map, November 1, 1984	145
37	Apparent Petroleum Thickness Contour Map, February 11, 1985	146
38	Apparent Petroleum Thickness Contour Map, May 6, 1985	J47
39	Apparent Petroleum Thickness Contour Map, August 12, 1985	148
40	Apparent Petroleum Thickness Contour Map, November 5, 1985	149
41	Task Force Sampling Locations, Texaco Refinery, Casper, Wyoming	176
Plates
Plate
Number
1 Generalized Hydrogeologic Cross Sections A-A', B-B', C-C'
Appendices
A Groundwater Task Force Analytical Data, August 11, 1986
B Geologic and Well Completion Logs North Area
C Geologic and Well Completion Logs South Area
D Field Data Sheets, Ground-Water Task Force, August 11, 1986
E Historic Water Level Elevations in North Area,
December 1986 - December 1987
F Texaco Concentration Maps, TOC, Phenol, Sulfide and
Ammonia 1983 - 1987
G Organic/Inorganic Usability Audit Report Lockheed, 11-10-86
H QA/QC Audit, PRC Engineering, 12-18-86
I Texaco Split Sample Results, August 11-15, 1986
vi

-------
eval-B
I EXECUTIVE SUMMARY
A. INTRODUCTION
1.	Task Force Effort
Operations at hazardous waste treatment, storage and disposal (TSD) facilities are
regulated by the Resource Conservation and Recovery Act (RCRA, P.L 94-850).
Regulations promulgated pursuant to RCRA (40 CFR Parts 260 through 265,
effective on November 19, 1980 and subsequently modified) address hazardous
waste site operations including monitoring of ground water to ensure that
hazardous constituents are not released to the environment. The regulations for
TSD facilities are implemented (for EPA-administercd programs) through the
hazardous waste permit program outline in 40 CFR Part 270.
The Administrator of the U.S. Environmental Protection Agency (U.S. EPA)
established a Hazardous Waste Ground-Water Task Force (Task Force) to evaluate
off-site and selected on-site TSD facilities and address the causes of non-
compliance. The Task Force is generally comprised of personnel from EPA
headquarters core team, regional offices, and the states.
2.	Task Force Objectives
The principal objectives of the investigation at the Texaco Refinery in Casper,
Wyoming were to determine the following:
a)	Compliance with the requirements of 40 CFR 265 Subpart F -
Ground-Water Monitoring
b)	Evaluate the existing information on the ground-water protection
program for potential compliance with 40 CFR Part 270
c)	Evaluate the existing and proposed ground-water protection program
for potential compliance with 40 CFR Part 264
d)	Verify the quality of the facility's ground-water monitoring data
e)	Evaluate the sampling and analytical procedures employed by the
facility
f)	Collect ground-water samples using the Task Force Protocol in order
to evaluate and compare analytical results with those collected by
Texaco in addition to determining the presence of hazardous waste
constituents.
3.	Evaluation Procedures
To meet the objectives of the task Force evaluation for the Texaco facility in
Casper, Wyoming, the following activities occurred:
a) Compilation and analysis of all relevant data, reports and
correspondence from U.S. EPA Region VIII files and files present in
the offices of Wyoming DEQ in Cheyenne, Wyoming
1

-------
b)	Sampling audit of facility's ground-water sampling procedures
conducted from June 18 to June 20, 198lf
c)	Collection and subsequent analysis of ground-water, surface water,
hydrocarbon and pond liquid samples obtained from August 11 to
August 15, 1986
d)	Site inspection and interviews with facility personnel and contractors
from September 29 to September 30, 1987.
Some of the information obtained from Texaco was acquired well after the Task
Force site visit in August 1986. These data have been utilized in this report where
required to support the Task Force's evaluation of the current ground-water
monitoring program.
B. SUMMARY OF FINDINGS AND CONCLUSIONS
The following summary of findings and conclusions is based on Task Force
interpretations of existing data, observations and findings from the sampling event at the
site on August 1 1-15, 1986, and the requirements of 40 CFR 264 and 265 Subpart F.
For simplicity, the Task Force's findings and conclusions below have been subdivided into
sections corresponding to those of the technical report (Part II).
1. Hydrogeology
Two aquifers of concern exist in the North Area. The uppermost aquifer is
composed of unconsolidated eolian sands and alluvial deposits, and the
consolidated Teapot Sandstone, subcropping in the eastern portion of the facility.
The second aquifer consists of unconsolidated alluvial deposits located within the
North Platte River floodplain. The second aquifer is tower than the uppermost
aquifer, but this difference is topographic, not stratigraphic. Even though the two
aquifers are not connected in a geologic or hydrostratigraphic sense, the uppermost
aquifer recharges the alluvial aquifer by means of seepage along an intervening
bluff. The only aquifer of concern in the South Area is the unconsolidated
alluvial aquifer. Except where the bedrock outcrops, the alluvial aquifer is present
throughout the South Area.
North Area
The major potential contaminant pathways include the North Platte River and its
associated alluvium, and possibly the Teapot Sandstone. All the above are used for
water supply east of the site. The potential for contamination of the Teapot
aquifer is undefined at the present time. Testing of downgradient Teapot wells
for contamination is recommended.
South Area
The major impacts from the contaminants would probably be to the North Platte
River. Escape of contaminants to the east, around the bedrock high and through
permeable lenses in the unnamed middle member of the Mesaverde Formation are
possible pathways to the river. While no bedrock aquifers underlie the South Area,
migration of contaminants to the northeast may impact the Teapot aquifer. This
pathway is presently undefined and conjectural. To reach the subcrop of this
2

-------
eval-B
aquifer, migration off-site to the northeast must take place. The distance to the
subcrop of the Teapot Sandstone from the eastern boundary is not defined. In
addition, the ground-water flow in the southeastern corner of the site is not fully
understood a limited number of data points (wells and/or piezometers) exist in this
area.
2. Ground-water Monitoring System
a. North Area Ground-water Monitoring Systems
The ground-water monitoring system in the North Area is currently
regulated under interim status. Two RCRA-regulated units, the North Land
Farm and the Chemical Evaporation Pond (CEP), arc located in this area.
The land farm is currently accepting and disposing waste under interim
status. A Part B Permit Application for this unit was submitted to EPA in
1985. According to Texaco, the CEP ceased to accept wastes after June
1982, and was closed under interim status in 1986. Texaco states that
degraded ground water in the North Area is emanating from the CEP. Due
to this contamination, Texaco initiated an assessment monitoring program to
delineate the.rate and extent of migration and concentration of
contaminants in the ground water. Texaco originally considered the two
regulated units as one hazardous waste management unit. Currently, as part
of the Part B Permit Application, the North Land Farm is separated from
the CEP. At no time has Texaco designated monitoring wells as part of a
detection monitoring program under interim status for the North Land
Farm, even though they maintain that contamination is from the CEP.
Because a detection system has not been designated, baseline and statistical
data are not available. This information must be presented as Texaco
intends to proceed into detection monitoring under 40 CFR 264 upon permit
approval. The findings and conclusions discussed below are further
subdivided into the following headings: Interim Status Ground-Water
Monitoring (40 CFR 265), Proposed Ground-Water Monitoring System (40
CFR 264), Corrective Action for SWMUs (40 CFR 264.101), and the South
Area Ground-Water Monitoring System.
Interim Status Ground-Water Monitoring (40 CFR 265)
The present assessment monitoring program for the North Area as
interpreted by the Task Force has several technical deficiencies that
may not allow for an evaluation of the rate and extent of
contamination in the ground water. Texaco is required by 40 CFR
265.93(d) to evaluate the extent of light and/or dense phase
imraiscibles that may be associated with the existing contaminant
plume emanating from the CEP. A thorough evaluation of the
adequacy of the existing monitoring wells to detect such phases
should be initiated. Based on the Task Force evaluation, numerous
wells in the North Area may not be capable of monitoring for light
and/or dense phases. These data are needed for a complete
evaluation of the extent and migration of contaminants in the
uppermost aquifer as required by 40 CFR 265.93(d)(4)(i).
As previously mentioned under hydrogeology, the full extent of the
uppermost aquifer and the possible extent of the CEP contaminant
plume may not be completely evaluated. This is due to the potential
3

-------
for hydraulic communication between the Teapot Sandstone, a
potential contaminant pathway, and the alluvium. The subcrop of
the Teapot lies to the east of the CEP.
Texaco must determine the rate and extent of migration and
concentration of hazardous waste in the ground water (40 CFR
265.93(d)(4)). Currently, Texaco has made the above determination
on only four parameters (TOC, phenol, sulfide and ammonia). The
rate and extent of migration and concentration of all Appendix VII
wastes must be established.
As part of defining the rate and extent of contaminant migration
under 40 CFR 265.93(d), Texaco should evaluate the effects of
dilution, attenuation, hydrogeochemical and hydrobiological
phenomena which may be affecting the extent of the CEP plume.
This is important under assessment monitoring as the dimensions of
the plume are bound to be affected by the recharge of the CEP as
part of Tcxaco's remedial action plan for this ground-water
contamination. Texaco has not proposed, as part of their interim
status assessment program, data evaluation techniques which will
fully address plume migration. This is a very important point in
that when a corrective action program is initiated under 40 CFR
264.101 for the CEP plume, these data evaluation techniques will aid
in determining the effectiveness of the remediation program, and
will aid in tracking the rate and extent of contaminant migration. A
number of possible analytic procedures could be applied to existing
data to further assess the effects of recharge of river water on the
attenuation of contaminant concentrations in ground water in the
CEP area. These could include, but not necessarily be limited to, the
following kinds of analyses:
o Trend analyses of contaminant concentrations versus time in
monitoring wells, in an effort to isolate the effects of river
water recharge from attenuation effects occurring prior to
recharge. Monitoring wells might be grouped according to
their distances downgradient from the recharge pond in an
effort to eliminate some variability in the data.
o Reassessment of trends of maximum quarterly contaminant
concentrations, to determine whether the data more probably
suggest a stabilization of maximum concentrations, rather
than a continuing decline. In addition, the wells at which
maximum quarterly concentrations are detected should be
identified, and an assessment made as to whether or not there
is an identifiable trend of distance of maximum concentration
from the CEP versus time.
o Since Texaco has suggested that changes in sulfide and sulfate
concentrations may correlate with aerobic or anaerobic
biodegradation, an examination of temporal or spatial trends
in variations of sulfide/sulfate ratios might provide useful
information. Similar geochemical studies might be possible
using other chemical species.
4

-------
o Mathematical modeling of the hydraulic effects of river water
recharge could provide useful information regarding relative
rates of recharge versus ground-water underflow, rates of
transport of recharged water within the uppermost aquifer,
and the arcal and temporal extent of the effects of river
water recharge. Furthermore, by treating the recharged water
as an ideal tracer within an appropriate mass-transport model,
it should be possible to estimate the attenuation due solely to
dilution and dispersion effects, and thus provide estimates of
the attenuation due to chemical and biological degradation
phenomena.
Texaco should expand the sampling and analysis of indicator
parameters (e.g., TOC, phenols, sulfate and ammonia) during
assessment monitoring to include organic constituents unique to the
contaminated ground water. These data can be used not only to
correlate with the indicator parameters, but to evaluate the
effectiveness of corrective action in attenuating concentrations of
organic constituents in the future. Under 40 CFR 265.93(d)(4)(ii),
Texaco is required to determine the concentrations of the hazardous
waste or hazardous waste constituents in the ground water. Once
Texaco determined that waste constituents had entered the ground
water, they were required to continue monitoring these constituents
on a quarterly basis (40 CFR 265.93(d)(7). At this time some wells
arc sampled quarterly, but then only for indicator parameters and
not the waste constituents of concern.
Construction and integrity of the existing wells are questionable due
to a lack of detailed information, the use of natural gravel pack
and/or filter pack extending far above the top of screen, and the
lack of annular seals in numerous wells (40 CFR 265.91(c)).
These construction defects may not allow for the collection of
discrete ground-water samples. Turbidity values collected by the
Task Force (up to 750 N.T.U.) seem to indicate that some of the wells
may not be adequately developed and/or constructed, and thus not
performing properly.
Table 8 in the technical report points out that all of the wells in the
North Area have one or more construction deficiencies (EPA, 1986a)
which may impact their ability to provide representative, unbiased
ground-water samples from the uppermost aquifer. The use of PVC
construction material in this area may not be appropriate due to the
presence of aqueous organic constituents which may degrade and
cause adsorption, absorption or other phenomena which may bias
analytical results.
The land farm should have a detection monitoring system which will
allow for the immediate detection of releases from this unit (40 CFR
265.90) at the same time as the rate and extent of contamination
emanating from the CEP is being evaluated (40 CFR 265.93(d)], Data
collected from this interim status program, which Texaco had not yet
implemented, could be used as baseline data in evaluating the
5

-------
eval-B
proposed detection system under 40 CFR 264.98 in Texaco's Part B
Permit Application. For example, baseline statistical data for an
upgradicnt background well do not exist for the North Land Farm.
It is clear that once Texaco determined that contamination was
emanating from the CEP and not the North Land Farm, the two
units should have been separated [i.e. originally the two units were
treated as one management area (40 CFR 265.91(b)(1)] and a
detection monitoring program should have been initiated.
Proposed Ground-Water Monitoring Svstem (40 CFR 264)
As previously discussed, Texaco has proposed in their Part B Permit
Application, a detection monitoring program for the North Land Farm for
compliance with 40 CFR 264.98. Four wells were proposed. The Task Force
has the following comments on Texaco's proposal:
Data collected and evaluated by the Task Force indicates that
something unusual is happening at well M-36 as indicated by
potcntiometric maps and contaminant concentrations. This well
should be replaced as the upgradient well for the proposed system. A
new well(s) should be installed or other existing weHs evaluated to
determine the suitability of the well(s) as upgradient monitoring
wells (40 CFR 264.97(a)).
Texaco must designate monitoring wells at the point of compliance
which will detect an immediate release of hazardous waste
constituents to the ground water (40 CFR 264.98). Based on several
factors, existing well M-lOm and proposed wells M-38 and M-39
located at the point of compliance may not be sufficient to monitor
the North Land Farm for a release. An insufficient number of wells
exist directly south of the North Land Farm. In addition, of the
three point of compliance wells, only the existing well (M-lOm)
would detect a dense phase immiscible. The two proposed wells (M-
38 and M-39) are presently designed so as to monitor the ground-
water surface only.
The Task Force recommends that the construction and design of the
wells be re-evaluated. Construction deficiencies noted in wells M-
10m and M-36 may influence the quality of samples, and may .
provide a downward potential migration pathway for contaminants
(40 CFR 264.97(c)). Again, the use of PVC well construction material
is questionable.
Because the proposed indicator parameters/waste constituents
(benzene, toluene, lead, phenol and chromium) have been detected in
the ground water emanating from the CEP, it is recommended that a
thorough evaluation or waste analysis be performed for the land
farm so that key indicator parameters can be established. If this is
not possible, Texaco should propose a sensitive statistical test which
will allow the detection of contaminants migrating from the land
farm above and beyond the concentrations of existing contamination
from the CEP [40 CFR 264.98(a) and 270.14(c)(6)(i)].
6

-------
evai-o
The detection monitoring system proposed for the North Land Farm
should be capable at all times of monitoring up- and downgradient
of the land farm. With the recent initiation of recharge to the CEP,
the effects of ground-water mounding on ground water flow should
be continually monitored. This type of water level measurement
program and schedule should be proposed as part of the detection
program to ensure that up- and downgradient wells will be monitored
at ail times (40 CFR 264.97 and .98).
Corrective Action for SWMUs (40 CFR 264.101)
Because of the regulatory status of the CEP (i.e. ceased receiving wastes in
June, 1982), it is apparent that the corrective action program which was
recently instigated will be monitored under 40 CFR 264.101. At this time,
Texaco has not proposed such a program. The Task Force recommends that
the following conditions be included in this corrective action program. In
addition, deficiencies in the ability of the current ground-water monitoring
system to address releases from SWMUs are discussed.
Texaco must implement a corrective action program which mitigates
ground-water contamination from the CEP and other SWMUs in the
North Area (40 CFR 264.101). Because 40 CFR 264.101 lacks the
specific regulatory requirements for corrective action, the Task Force
feels the following conditions should be considered at a minimum:
o The number and locations of wells to be utilized, rationale for
their selection and an evaluation of the construction details to
evaluate the integrity of each well.
o Designate those indicator parameters and waste constituents to
be used to compare to a background well which can provide
data that can accurately represent the conditions at the site.
This is essential in order to show that all waste constituent
concentrations of concern, and not just some, are decreasing.
o Design a sampling and analysis collection program and
complementary data evaluation techniques which can
ultimately show the effectiveness of restoring the quality of
ground water in the North Area.
o Data evaluation techniques should be outlined in specific
detail, so that Texaco's evaluation of the corrective action
efficiency can be monitored continuously. Data evaluation
techniques were previously discussed.
At this time, Texaco has not provided the data to evaluate the
potential impacts of other solid waste management units in the North
Area. Specifically, the Solid Waste Landfill adjacent to the CEP and
the Asphalt Landfill should be investigated to evaluate whether or
not these units have impacted ground water. This is important as
source abatement is the first step in any ground-water corrective
action program.
7

-------
eval-B
b. South Area Ground-Water Monitoring System
The ground-water monitoring system in the South Area addresses a
substantial accumulation of floating hydrocarbon in the central portion of
the site and a dissolved organic plume in the southeastern corner. A
hydrocarbon recovery system (recovery wells, recharge wells and interceptor
trenches) is currently removing and treating the floating hydrocarbons in
the central portion. Because no regulated units exist in the South Area, the
floating hydrocarbon is probably a result of past waste management
practices, specifically releases from the numerous solid waste management
units identified in this area. Corrective action currently underway in the
South Area is subject to the regulatory requirements of 40 CFR 264.101,
corrective action for SWMUs.
The Task Force review of the available data produced the following
recommendations:
The Task Force recommends the identification and abatement of all
potential sources of ground-water contamination in this area which
may continue to release contaminants into the ground water.
In the past, Texaco has only evaluated the extent of floating
hydrocarbon in the central portion of the facility. The Task Force
recommends that evaluation for the presence of dissolved and/or
dense phase immiscible organics be performed. The Task Force
sampling identified the presence of both dissolved and dense phase
immiscible organics in this area.
Texaco should initiate a sampling and analysis program to evaluate
the full extent of hydrocarbon contamination. These data will
provide a baseline for future monitoring to evaluate the
effectiveness of corrective action.
It is recommended that a thorough evaluation of construction and
design specifications be performed prior to designating wells needed
for ground-water quality analysis. An evaluation by the Task Force
has shown numerous wells to contain construction defects.
Texaco should evaluate the existing wells located between the plume
and the North Platte River to detect light, dense and dissolved
organics in order to detect a release prior to discharge to the North
Platte River, specifically in the area between the east end of the east
interceptor trench and the west end of the reported clay barrier.
Note that the Task Force identified contamination immediately
adjacent to the river within this area.
Texaco should implement a performance monitoring program to
evaluate the efficiency of the interceptor trenches and recovery wells
currently in operation.
A ground-water monitoring program used to evaluate the performance of oil
recovery operations may include, but is not limited to the following
recommendations:
8

-------
Texaco should implement a performance monitoring program for the
interceptor trenches, which at a minimum should include 1) an
evaluation of grade control to ensure that ponding in the trenches is
not occurring; 2) continued monitoring of water levels in wells
adjacent to the east interceptor trench, and wells adjacent to the west
interceptor trench and the North Platte River to ensure the trenches
are continuing to act as ground-water sinks. This is important as it
is probable that the oil recovery system (recovery and recharge wells)
plus seasonal variations in water levels will alter the performance of
the trenches. In order for the trenches to be effective, they must
operate to account for these variations. Texaco should consider
additional wells south and north of the trenches to evaluate
gradients; 3) the implementation of a monitoring program of wells
installed between the trenches and the North Platte River to ensure
that contamination is not migrating past the trenches. The wells
should be completed to monitor for floating hydrocarbons, dissolved
organics and dense immiscible phases; 4) A maintenance and
operation program to inspect the trenches to ensure proper operation.
Inspections should include an evaluation of the drains for chemical
clogging (biological slimes), excess siltation due to introduction of
fines and other mechanical failures associated with the pumps and
skimming devices in each sump.
In addition, it is apparent that the oil recovery system (recovery and
recharge wells) may be increasing contamination of the aquifer by
injecting untreated ground water back into the aquifer. As part of
performance monitoring, Texaco should sample the water being
recharged to the aquifer for organics. Based on these analyses,
Texaco should present a treatment method (if required) such as air
stripping to remove the dissolved hydrocarbons to an acceptable
level. The use of the PCS coke settling pond and the service water
ditch for discharge of skimmed water from RW-1 and the interceptor
trenches, respectively, should be evaluated as they may also be re-
introducing contaminants into the ground water through seepage. An
enclosed treatment system as opposed to open ponds would be more
appropriate. In conclusion, the treatment technologies currently in
place should be re-evaluated to determine further impacts to the
ground water and/or surface water bodies.
The Task Force recommends that Texaco address the 950 feet of
shoreline along the North Platte River which does not contain
interceptor trenches or barriers, and does not appear to be within the
influence of the recovery wells. This appears to be a prominent
pathway for potential off-site contaminant migration. This is
supported by the presence of contamination in wells SS-4 and SS-5 in
the form of a floating and/or sinking phases. Based on the location
of wells SS-4 and SS-5, it appears that discharge of contaminants to
the North Platte River may be occurring, possibly on a seasonal basis.
It is recommended that Texaco evaluate the potential for releases in
this area to the North Platte River. This may include the installation
of additional wells between SS-4 and recovery well RW-1. As part of
this evaluation, the structural integrity of the clay barrier installed
in 1957 should be investigated in order to determine the efficiency

-------
of this structure to control contaminant migration (i.e. floating,
dissolved and/or dense immiscibles). If the potential for migration is
high, which it appears to be in this area, Texaco should consider the
installation of an enhanced ground-water control system in this area
which may include French drains or barrier walls, or possible
expansion of the oil recovery system (recovery wells). As part of this
monitoring and performance evaluation for the trenches, inspection
for seeps along the south bank of the North Platte River (entire
Texaco property) should be implemented so that immediate detection
of releases can be made. The inspection schedule for seeps should
take into account seasonal fluctuations in water levels, river stages,
and operation and shutdown of the hydrocarbon recovery system.
The Task Force recommends that Texaco evaluate the quality of
ground water pumped from the recovery wells and discharged down
recharge wells. The ground water is not treated for dissolved
organics prior to recharge. It appears that this lack of.treatment
may further contribute to contamination of the uppermost aquifer.
The Task Force recommends that Texaco install additional wells in
the southeastern corner of the site to address the full extent of
contamination in this area. Task Force data indicate that
concentrations of organics were detected along the eastern property
boundary. Migration of organics off-site to the east may be of
concern. Concentration in these wells as detected by Texaco
immediately following the Task Force Evaluation (October 1986) arc
as follows: benzene (21 to 10,000 ug/1); ethylbcnzcne (<10 to 3,500
ug/1); toluene (<10 to 5,000 ug/l); and xylene (<10 to 5,800 ug/1).
3. Task Force Sampling and Monitoring Data Analysis
During the Task Force inspection, 16 ground-water samples and three surface
water samples were collected. The purpose of this sampling was to determine the
concentrations of hazardous waste constituents in the ground water at Texaco, and
to verify Texaco's past analytical performance. The Task Force review of these
data produced the following findings and recommendations:
The Task Force data from the North Area confirmed the presence of
hazardous waste or hazardous waste constituents in the ground water. In
general, the data indicate that the area near the CEP and North Land Farm
are the most contaminated, with monitoring well M-36 showing the highest
concentrations. Low levels of organic contaminants were detected in one of
the alluvial aquifer wells (M-12S) during the evaluation. The data also
indicate that surface water samples taken from the inlet of the Excess
Service Water Effluent Ponds and the Alluvial Pond were not contaminated
with any organic constituents. Inorganic constituents which exceeded
applicable standards included arsenic and selenium at wells M-lOs and M-36,
and selenium and nitrate at the inlet pond of the Excess Service Water
Effluent Pond. The secondary standards for sulfates, iron, manganese and
other parameters were also exceeded at numerous wells.
The Task Force data from the South Area (central portion ) show the
presence of several organic constituents in the four wells sampled (SS-19, SS-
49, SS-34 and SS-4). Constituents and ranges include: benzene (38-6000
10

-------
cr aru
ug/1), ethylbcnzcne (ND-310 ug/1), toluene (ND-620 ug/1), and total xylenes
(ND-3000 ug/1). The highest concentrations of the above mentioned
organics were found in well SS-49. Several other base/neutral organics were
detected in wells SS-19, SS-49 and SS-4, with SS-4 showing concentrations of
organics (chryscne, fluorene, fluoranthcne, etc.) ranging from 700 to 2800
ug/1. Organics were not detected in the upgradient well (M-41a) sampled by
the Task Force. It is recommended that concentrations of dissolved organics
and the presence of dense phase immiscible organics be evaluated by
Texaco.
Several deficiencies in Texaco's Sampling and Analysis Plan were noted.
The Task Force recommends that the plan be updated to reflect current
sampling procedures and methodologies, and include the detail required to
assure the"collection of quality data. In accordance with the TEGD (EPA,
1986), the following technical deficiencies of the written sampling and
analysis plan were noted by the Task Force:
o The air in the well head should be and was not sampled for organic
vapors using either a photoionization analyzer or an organic vapor
analyzer.
o A discussion of how static water levels will be obtained was not
included.
o The plan docs not specify how light and/or dense phase immiscibles
would be detected. A discussion on how Texaco will determine the
thicknesses of such layers should also be included.
o A step-by-step procedure for well evacuation was not included in the
plan. Specifically, the procedures used by the facility when an
appropriate volume of water cannot be evacuated, should be
discussed.
o Texaco should further discuss sample withdrawal procedures. The
plan does state the choice of materials used during sampling
withdrawal, but does not indicate how samples will be obtained for
light and/or dense phase immiscibles.
o Texaco indicates in the addendum to the sampling and analysis plan
that ground-water samples that are organically contaminated should
be filtered. This is in direct opposition to current protocols.
o A detailed QA/QC program that will be used in the field and
laboratory should be specified in the Sampling and Analysis Plan.
The Task Force data for surface water from the PCS pond, which is used
for effluent from recovery well RW-1, also showed the presence of
numerous organics, thus indicating that this pond may be a continued
source for ground-water contamination and that effluent from RW-1 may be
contaminated.
The Task Force data show concentrations of organics (benzene, toluene,
ethylbenzene and naphthalene) detected in well SS-7 located along the
11

-------
eastern property boundary. It is recommended that the source of this
contamination be identified, along with its extent.
4. Compliance With Superfund Off-Site Policy
Under current EPA policy, if an off-site TSDF is to be used for land disposal of
waste from a Supcrfund-financed cleanup of a CER_CLA site, the TSDF must be in
compliance with the applicable technical requirements of RCRA. The Texaco
facility docs not accept off-site Superfund cleanup wastes and therefore was not
evaluated with regard to the offsite policy.
12

-------
eval-B
II TECHNICAL ASSESSMENT
A. INVESTIGATIVE METHODS
The Hazardous Waste Ground-Water Task Force (Task Force) investigation consisted of
the following:
o Reviewing and evaluating records and documents from U.S. EPA Region VIII files,
Wyoming Department of Environmental Quality (DEQ) files, and Texaco Refinery
files.
o Conducting an on-site facility inspection during the week of August 11, 1986.
o Sampling and analyzing data from 16 ground-water monitoring wells and three
surface water locations.
1.	Records/Document Review
Records and documents obtained from EPA Region VIII, Wyoming DEQ and
Texaco were compiled and reviewed prior to, and following, the on-site inspection.
The purpose of this review was to obtain information regarding past and present
facility operations, details of the waste management units and the facility's
ground-water monitoring program.
The complete list of documents used during the evaluation is presented in Section
F. Documents which were of significant importance included: Part B Permit
Application*(November 5, 1985),.CEP Closure Plan (October 5, 1984), Casper Plant
North Land Farm Reconnaissance Investigation Report (June 15, 1987) and the
series of Annual Reports (1983-1987) of the Ground-Water Pollution Abatement
Program.
2.	On-Site Inspection
A facility inspection was performed at the Texaco Refinery during the week of
August 11, 1986. The objective of this inspection was to determine compliance
with federal regulations, in particular, those regarding the ground-water
monitoring system.
3.	Task Force Sampling Locations and Methods
A total of 16 ground-water monitoring wells and three surface water locations
were sampled by the Task Force. A detailed discussion of the monitoring wells is
presented in Section D of this report.
Each sample was analyzed for the 40 CFR 265.92(b)(1), (2) and (3) parameters,
volatile organics and the base neutral/acid extractable organics. Field analyses
included pH, temperature and specific conductance. Data from sample analyses
were reviewed to further evaluate Texaco's ground-water monitoring program and
to identify ground-water contamination. Summary tables of analytical results for
the samples collected by the Task Force are presented and discussed in Section E of
this report. The raw data are presented in Appendix A.
13

-------
eval-B
B. FACILITY HISTORY, OPERATIONS AND DESIGN
1. Background
Texaco owns and operates a crude oil refinery located in the municipality of
Evansville, Natrona County, Wyoming. The refinery was operational from 1921
until August 1982, when it temporarily ceased production for economic reasons
(A.T. Kearney, 1986). The facility currently remains inactive. During its
operational life, the facility processed crude oil into gasoline, dicscl and other
fuels. Texaco owns property on both sides of the North Platte River (Figure 1).
The property located north of the North Platte River (North Area) contains crude
oil tankage areas and several waste management areas, including two RCRA-
regulated hazardous waste management units. These arc the Chemical Evaporation
Pond (CEP) and the North Land Farm. The property south of"thc North Platte
River (South Area) contains the process units, product tankage areas, several solid
waste management units (SWMUs), and office buildings (Figure 2).
The primary surface water feature in the area is the North Platte River which
flows through the Texaco site. The river is perennial and a prominent regional
drainage feature which encompasses a wide area of influence. There are no
naturally occurring perennial or intermittent streams on either the North or the
South Areas.
On the North Area, runoff is controlled, for the most part, within the various
facilities found there. The primary method is the retention and evaporation of the
small quantities of precipitation which fall on the area. Locally, in the area
around the Excess Service Water Effluent Ponds, runoff is directed through sheet
flow into the ponds adding only minor amounts to their water inventory (A.T.
Kearney, 1986).
The South Area is managed somewhat differently. A series of ponds adjacent to
the river are designed to, among other things, collect runoff from the facility. In
these ponds, runoff water from process areas is kept separate from that originating
in non-process areas. During operation, much of the runoff eventually ends up in
the facility's service water system and from there, is either discharged to the
Excess Service Water Effluent Ponds (North Area) or used as process water in the
refinery operations in the past. All runoff now is collected and allowed to
evaporate within the ponds. If the runoff exceeds the pond's capacity, the water is
pumped to the Excess Service Water Effluent Ponds (A.T. Kearney, 1986).
The facility is partially located in the 100-year flood plain. Figure 3 depicts the
50 and 100-year flood potential. As may be seen from Figure 3, the North Area
waste management units all lie outside the 100-year flood plain. Approximately
one-third of the South Area lies within the 100-year flood plain.
The climate of Casper, located approximately three miles west of the facility, is
temperate and dry. The average temperatures range from a maximum of 83F in
the summer months to a minimum of 16F in the winter months. Mean monthly
temperatures exceed freezing in all months except December through March. The
average date of the last freezing temperature is May 22 and of the first freezing
temperature is September 22 (A.T. Kearney, 1986).
14

-------
R 79 W	|	R 78 W
TEXACO
REFINERY
EVANSVILLE
CASPER
R78W
R79W

i mAas
B kdomstars
10
Figure 1 Facility Location Map
Source: Modified from WWC, 1982a
15

-------
nONO
EXCESS SERVICE WATCR
|	EFFLUENT PONDS
TEXACO PROPERTY BOUNDARY
i\~^r\ i
tOOO *!
UNO'Ul
OUTIC r
If TTLIH9
PONOl
TEXACO PROPERTrl
BOUNDARY	|
NO* T H
|A*0( I 
LtOOk
HA I 		I
ua

lOAOIh
scalc in recr
FIGURE 2
Foe i 111 y Map
Te*oco Refinery, Casper, Wyoming
 OfcO Oil 	'
TANK FAItM
kC*tO TO
C* CAT L*I 1
CARBON CO*' '
Source : ModUltd Irom Wtiltrn WoUr Coniullonu, 1987.

-------
ip
4
CHEMICAL
EVAPCfl AT INC

r~

:r
fi'a +*4 *
. Ml
o
0
O
O [,
[
. 0
O
0 ^
!
0
>V
o
0
IP
o
-p*v
G
o!
a
o
		a/
I,'
d
2=Sy.Ti=
, 77h / 1 :
tzfsrp^
CHEMICALS U
:5W_-EsiJr3j:n
-:^i^.^1 y- *

ii !!: : llfejjfcg"
//!! ] ^v-i' p.l:	[g~1 j J
/JJ	1 f
| ^ /c.r^^:,-.-.. tvu/iu.-- ,
S^ESSf e!
-- - " - V&a *L*JF^Sn
Ir Y  irOiG^ * ,-Jj
EXPLANATION
INTERMEDIATE (50 Yr.l
REGiONAL rLCOO
STANOARO (ICO Yr.)
PROJECT FLCOO

-------
eval-B
Precipitation averages 11.4 inches per year with approximately half of the total
occurring as rain and wet snow during the spring. Precipitation occurs principally
in low-intensity small events. Evaporation in Casper averages 46 inches per year.
The average evaporation rate exceeds the average precipitation rate in all months
of the year (A.T. Kearney, 1986).
The wind rose for the Casper area shows that winds are moderately strong and
predominantly southwesterly during all months of the year. The mean wind speed
is 13.3 miles per hour with stronger winds occurring during the winter months
(A.T. Kearney, 1986).
Adjacent land use information is minimal. The property bordering Tcxaco's North
Area is privately owned, except for a small parcel of state-owned land in Section
36 near the North Platte River. The private land is used for grazing of horses.
The land contiguous with the South Area is more varied. To the west lies the town
of Evansvillc. South of the refinery lies Burlington Northern Railroad, various
industrial properties, a frontage road and U.S. Highways #20, 26 and 87.
Immediately cast of the facility is Sinclair Oil Corporation's Little America
Refinery (Texaco, 1985).
2. Regulatory Background
On November 14, 1980, Texaco submitted a Part A Permit Application and
identified itself as a generator, trcatcr and disposer of hazardous waste. Revised
Part A applications were submitted on the following dates: March 2, 1982, August
2, 1982 and June 16, 1983. Table 1 lists the regulated hazardous waste codes and
descriptions, the estimated annual quantity of waste, and the associated treatment,
storage or disposal units as taken from the June 16, 1983 Part A Application.
On June 13, 1983 Texaco submitted a RCRA Closure Plan for the CEP. EPA
disapproved this closure plan and Texaco submitted a revised plan on October 5,
1984. EPA modified and approved this closure plan and a public notice was held
regarding the plan in March 1985. During June 1985, Texaco entered a lawsuit
against EPA in the U.S. Court of Appeals, 10th Circuit, challenging EPA
modifications to the closure plan and also requesting a stay of the modified plan.
The court granted Texaco's request for a stay. During August 1986, Texaco and
EPA entered into a consent agreement concerning the CEP closure plan. On
September 26, 1986 Texaco notified EPA pursuant to 40 CFR section 265.115 that
the CEP had been closed according to the approved closure plan and that closure
occurred pursuant to 40 CFR 265.228(b), clean closure.
On November 5, 1985, Texaco submitted a Part B Permit Application for the North
Land Farm. This was revised in July 1986. On May 6, 1987, EPA issued a Land
Treatment Demonstration Permit pursuant to the requirements of 40 CFR section
264.272. On June 15, 1987, Texaco submitted a reconnaissance report of the North
Land Farm identifying 11 hazardous constituents in the soil. A letter dated
December 1, 1987 was submitted to EPA stating that six hazardous constituents
were detected below the treatment zone (vadose zone) of the North Land Farm.
Although this information was presented after the Task Force investigation, it is
relevant to the proposed 40 CFR 264 Subpart F ground-water monitoring system
discussion later in this report.
18

-------
slh
Waste Code	Waste Description
K049	Slop oil emulsion solids
K050	Heat exchanger bundle cI'
K051	API Separator sludge
K052	Leaded tank bottoms
D001	Ignitable wastes
0002	Corrosive wastes
0003	Reactive wastes
0008	EP toxic wastes - lead
Table 1
Surmary of Wastes Handled by Texaco
Estimated Annual
Duali ty of Uaste
2583 T
ng sludges	5 T
2 T
1542 T
7741 T
575 T
870 T
1358 T
Unste Management Unit
Tank storage, land application
Land applicat i on
Land application
Tank storage, land application
Tank storage, land application
Surface impoundment
Tank storage, land application
Tank storage, land application
Source: Texaco Part A Permit Application, June 16, 1983

-------
eval-B
3.	Facility Operations
The Texaco facility generates, treats, stores and disposes of hazardous waste during
normal operations. Since its closure in 1982, the majority of the waste applied to
the North Land Farm has been wastes generated at the refinery during cleanup
operations.
Twenty-one solid waste management units (SWMUs) have been identified at the
Texaco facility. Two of these, the CEP and the North Land Farm, arc considered
HWMUs, and arc RCRA-regulated. A brief description of the SWMUs follows, as
most of these units have a potential to contribute to the degraded ground water at
the facility. The information on the SWMUs is taken from the A.T. Kearney
RCRA Facility Assessment Report dated October 1986 (A.T. Kearney, 1986).
During the Task Force investigation, it was confirmed that all of the SWMUs at
the site met the regulatory definition of a SWMU. In the past, Texaco maintained
that several SWMUs were process units and did not meet the definition. The
locations of all SWMUs and HWMUs arc presented on Figure 2.
4.	RCR A-Regulated Units
North Land Farm This unit is located in the North Area as shown on Figure 2.
The North Land Farm consists of 13.5 acres on a bluff, adjacent to the CEP. The
North Land Farm received refinery wastes until plant shutdown in 1982.
Landfarming continues at present with wastes generated from both tank and pond
closure activities. Both listed wastes and non-listed wastes arc land farmed. The
listed hazardous wastes as identified in 40 CFR 261 Subparts C and D include:
Slop oil emulsion solids (K049)
Heat exchanger bundle cleaning sludge (K050)
API separator sludge (K051)
Leaded tank bottoms (K052)
Possibly ignitablc wastes (D001)
Possibly reactive wastes (D003)
Possibly EP-toxic wastes (D008)
CEP This unit is also located in the North Area, contiguous to the North Land
Farm (Figure 2). The 6.6-acre surface impoundment had a maximum operating
capacity of 16,000,000 gallons. The depth of the unit was nine feet. The pond was
built on the site of an old tank farm and occupies the area within two of the
abandoned tank levees. Four levee raisings were done to provide additional
storage capacity. These raisings added approximately four feet to the original
levee.
The pond received wastewater from the plant which was pumped intermittently
through a four-inch pressurized pipeline. Flow into the pond averaged 42 gallons
per minute.
None of the waste streams which contributed to the CEP were classed as RCRA
hazardous wastes based on being listed or characteristic wastes. However, the
waste streams did contain a number of hazardous constituents found in Appendix
VIII. Organic analyses of the pond wastewaters and sludge were performed in
1982 and 1983. In these analyses, nine organic constituents from Appendix VIII
were found as follows:
20

-------
eval-B
Chemical Evaporation Pond Wastewater Analysis
1982/1983
Toluene
2,4-dimcthylphcnol
Phenol
Naphthalene
Diphenylamine
Benzencthiol
Chemical Evaporation Pond Sludge Analysis
1982/1983
Toluene
2,4-dimethylphenol
Phenol
Naphthalene
Chryscnc
Benz(a)anthracene
BenzO(a)pyrene
5. Solid Waste Management Units
Asphalt Landfill This landfill is located within the North Tank Farm (Figure 2).
The area of the landfill is unknown; however, visually, the area affected appears
to be approximately 150 feet wide by 300 feet long. The waste management
technique was apparently to back trucks to the edge of the bank and dump loads
down the slope,
There was only one waste stream reported for this landfill, that being loads of off-
specification asphalt. Asphalt was dumped from the top of the slope and
flowed/moved downslope. The more liquid portion, present within the waste or
generated by radiant heating of the asphalt, flowed downslope and collected in a
"pool." This "pool" is approximately 30 feet by 50 feet and of unknown depth. The
entire downslope is covered with asphalt in varying stages of decomposition.
Solid Waste Landfill This unit is often referred to as the North Landfill.
According to Texaco, it occupies 3.2 acres west of the CEP (Figure 2). About 2.5
acres have an incorporation depth of four feet, and the remaining 0.7 acre has an
incorporation depth of about 12 feet.
There are three topographic "benches" which should be included (instead of only
the uppermost). The lower "benches" appear to have been used for the random
disposal of asphalt and coke.
Approximately 24 tons of solid wastes were placed in the landfill each year from
1957 until shutdown of the refinery in mid-1982. The reported waste stream
included:
Scrap lumber
Lime pit sludge
Oily wipers
Office waste paper
21

-------
eval-B
Limited amounts of scrap metal
As indicated earlier, large areas both in and adjacent to the landfill have been
used for the disposal of asphalt, coke and in at least one area, empty drums.
Dumped loads of asphalt, coke and pooled tar-like material were observed
randomly across the surface.
Excess Service Water Effluent Ponds This unit is comprised of eight separate
ponds located approximately 4,500 feet north of the North Platte River (Figure 2).
Water is pumped from the refinery into the first three ponds, which operate in
scries. The water from these ponds discharges into pond 1, which is connected to
four subsequent ponds via a ditch. The total area covered by the ponds is
approximately 160 acres with an average water depth of four feet and an
estimated volume of 200,000,000 gallons. All the ponds arc unlincd and non-
discharging to other surface water bodies (the ponds arc approximately 110 feet
above the North Platte River). Water levels are managed through evaporation.
Presently, and since refinery shutdown, the ponds are essentially not being used
since the plant requires no cooling water. The water levels arc now quite
depressed with alkali flats developing around the perimeter of the various ponds.
The Excess Service Water Effluent Ponds received overflow from the service water
system of the refinery. The following six wastewater streams discharged to the
service water system and hence to the Excess Service Water Effluent Ponds:
Process unit drainage system
PCS coke drum blowdown system
VPS barometric condensate system
Water treating plant blowdown system
Storm water system
Interceptor system
The water from these systems was temporarily stored on the south refinery
property and then pumped to the ponds through a 12-inch pipeline. All water
initially entered three small ponds (the pretreatmcnt ponds) which arc connected in
scries. In these ponds, any oil present in the water collects at the surface. When
sufficient quantities are collected, the ponds arc skimmed using a vacuum truck.
Water from the pretreatment ponds enters the remaining ponds (also in series) as
the flow from the refinery dictates.
Flow into these ponds has been limited to water produced from the underground
hydrocarbon recovery system since the refinery shutdown in 1982.
Wastewaters were analyzed for organic priority pollutants during refinery
operations. At that time, three hazardous constituents were identified. These
were:
Endosulfan
1,1,1-trichloroethane
Chrysene
Subsequent pond water analyses were performed that indicated there were no
organic priority pollutants present in the retained water.
22

-------
eval-B
East Land Farm The East Land Farm is located near the eastern boundary of the
plant's South Area as shown on Figure 2. Only an access road separates this unit
from Little America's refinery property limits. The Land Farm occupies an area
of approximately nine acres.
The Land Farm is reported to have received tank bottoms, oily wastes, and .
weathered leaded sludge. The East Land Farm primarily treated the lighter
petroleum fraction wastes, with the heavier petroleum wastes going to the North
Land Farm. Among the RCRA listed wastes which were applied to the Land Farm
(disposal was prior to RCRA regulations) arc:
Slop emulsion solids (K.049)
Heat exchanger bundle cleaning sludge (K050)
API separator sludge (K.051)
Leaded tank bottoms (K.052)
Also included in the waste stream were not otherwise specified (NOS) tank sludges.
Asphalt Landfill This area, located in the South Area, was used for the disposal
of truck loads of off-specification asphalt. The area in which loads were dumped
is fairly widespread; however, the entire area has not been "covered" with asphalt.
Tar-like liquids either in the off-specification product, or those developed by the
radiant heating of the material, flowed to low points and collected. The active
area affected by waste disposal was not provided; however, visually, the area
appears to be approximately 200 feet by 400 feet.
The only waste stream reported for this unit is off-specification loads of asphalt.
In the early history of the unit, asphalt was burned. Generally, waste thickness
averages approximately three to four inches with the pooled material areas
(mentioned above) reaching three to four feet in depth.
Chemical Evaporation Pond Sump This unit consists of a concrete-lined sump,
approximately 20 feet square, that was used to collect the various waste streams
prior to their final disposal in the chemical evaporation pond. Minimal
information regarding the construction or operational details of the unit was
provided.
Details of the wastes managed in this unit were not provided. Since the unit
collected all the various waste streams prior to their being pumped into the
chemical evaporation pond, it can be inferred that the wastes reported for the
pond are essentially the same as the sump. These waste streams include
wastewaters from the following:
Hydro Treater Unit (HTU)
Catalytic Polymerization Unit (Poly)
Fluid Catalytic Cracking Unit (FCCU)
Pressure Coke Stills (PCS)
Catalytic Reforming Unit (CRU)
Stabilizers
In addition, the unit apparently received oily wastes, based on the fact that the
sump is equipped with a skimming type oil removal system.
23

-------
eval-B
Landfill/Burning Ground This unit was located in the South Area. Relatively
little information exists regarding this unit as it has not been used for
approximately 30 years.
The waste stream to this landfill is reported to have contained:
Drums, bricks
Scrap lumber
Oily wipers
Office waste paper
Scrap metal
Plant Trap The Plant Trap (oil trap) is located south of the Trap S. Pond and the
Service Water Return Ditch as shown on Figure 2. This unit is an early model API
Separator designed to remove oil from the incoming wastewaters. The trap has a
number of cells from which oil was skimmed. Construction of the unit is of
concrete which extends approximately one foot above ground surface and six to
seven feet below ground surface.
This unit was operated to remove oil from the water produced in process area
washdown. The recovered oil was pumped to nearby tanks for storage (tank area
is bermed). The stored oil was eventually returned to the process inflow.
Service Water Return Ditch/Trap S. Pond This unit includes the Trap S. Pond and
the Service Water Return Ditch as shown on Figure 2. The ditch appears to be
approximately 10 feet in width and four feet deep. Both units arc unlincd.
Water enters this system from the refinery into the Plant Trap which separates the
oil from the water. Discharge from the trap goes into, the Trap S. Pond. From the
pond, water enters the Service Water Return Ditch which flows northwestward to
the pump. Water from the system is cither returned to the process areas for reuse
or is pumped across the river to the Excess Service Water Effluent Ponds where it
is allowed to evaporate.
There are six refinery water and wastewater systems discharged to the service
water system during refinery operations. These waste streams are:
Process unit drainage system
PCS coke drum blowdown system
VPS barometric condensate system
Water treating plant blowdown system
Storm water system
Interceptor system (currently uses Service Water Return Ditch)
Storm Water Surge Pond and Spare Storm Pond This unit is comprised of two
interconnected ponds which retain the same wastewaters. The units arc located on
Texaco's South Area along the North Platte River as shown on Figure 2. The units
are unlined and below grade.
Texaco has indicated that only runoff from the non-process areas of the refinery
flow into this unit and therefore, there are no hazardous constituents present.
Texaco did not define what they considered a "non-process" area.
24

-------
eval-B
Indications that the Plant S. Trap Pond (and possibly others known or strongly
suspected of containing hazardous constituents) can flow into the storm water
surge pond (and by connection to the spare storm pond) through overflow pipes
located near the top edge of the pond.
In addition, it is suspected (based upon the information provided) that these ponds,
as well as the PCS pond, the precipitator and accelerator ponds and the Trap S.
Pond, are in connection with one another via the ground water.
PCS Coke Settling Pond This surface impoundment is located east of and adjacent
to the Trap S. Pond as shown on Figure 2. The pond is unlined and below grade.
The pond was apparently used for coke process cooling water make-up and
blowdown. As such, coke dust accumulated in the water which settled out into the
pond.
Presently, the pond receives waste water from the ground-water recovery well (RW-
1) located approximately 300 feet cast northeast of the pond. In the recovery well,
a skimmer pump suctions the oil off the ground water. A lower submersible pump
is used to constantly pump ground water to create an artificial gradient towards
the well. The ground water itself is very oily and the pond has a scum of floating
oil on it as a result. The pond area has a very heavy hydrocarbon odor.
Precipitator and Accelerator Ponds This unit is comprised of two ponds which
receive the identical waste stream. The eastern pond is located as shown on Figure
2. The western pond is not shown on the figure, but is located directly north of
the precipitator and west of the eastern pond and the cooling tower. The
capacities and design information for these ponds was not provided.
The two ponds received clarificr solids and blowdown from the water treatment
plant. The purpose of the ponds was to allow the lime sludge to settle out of the
water. Water from the ponds was directed to the service water system after the
solids were removed. Periodically, solids were dredged from the pond and disposed
either in the North Land Farm or placed on the levees of Excess Service Water
Effluent Pond #1.
Texaco states "No known hazardous wastes or hazardous constituents were managed
at the precipitator and accelator ponds (A.T. Kearney, 1986)."
Barometric Separator This unit is constructed of concrete and is completely below
ground. The depth of the structure was not provided although it was stated to be
similar in construction to the plant oil trap previously described. The unit is
located immediately north of the West Tank Farm (Figure 2).
The separator is essentially an early model API Separator. Oily wastewaters
originating in the Vacuum Tower Still are processed in this unit to remove the oil.
The oil is skimmed/suctioned off the water in a series of individual compartments.
The recovered oil is pumped to tankage and eventually returned to the process
stream. Sludges are periodically removed from the unit and stored in tanks as a
listed hazardous waste (K.049 and K052).
25

-------
eval-B
Barometric Skimming Pond This unit consists of a single unlincd pond which is
approximately 1200 feet long by 50 feet wide. The pond is located between the
precipitator and the barometric oil trap. No other details of the construction of
the pond were provided.
This unit receives the outflow from the barometric separator. The separator
removes a quantity of oil although some remains in the water and is present in this
pond. The pond drains by gravity to the barometric ponds through an oil
skimming device. The oil collected by this equipment was eventually returned to
the process stream.
Barometric Ponds and Sprav Field (referred to as barometric lagoon on Figure 2).
This unit is comprised of two large ponds which arc interconnected through a
narrow neck. Details of the ponds' construction were not provided.
These ponds arc located on the northwest portion of the South Area as shown on
Figure 2. The southernmost portion of the pond is equipped with three spray lines.
The spray lines were used to cool the water during warm weather.
These ponds received the wastewater from the Vacuum Tower Still after the oil
had been removed in both the barometric separator and the barometric skimming
pond. Water was occasionally pumped through the spray lines as the process and
ambient heat loads dictated. Water from these ponds eventually discharges to the
service water system where it is either returned to the process for reuse or pumped
for final disposition into the Excess Service Water Effluent Ponds in the North
Area.
Leaded Sludge Disposal Areas Texaco has identified four areas in which leaded
sludge was disposed within tank farm containment areas. Since all these areas arc
similar, they have been grouped together. These areas are located within the cast
and west tank farms on the south property (Figure 2).
The four areas included in this description arc immediately adjacent to Tanks
#142, #147, #157 (west tank farm), and #307 (cast tank farm). It should be noted
that tank bottom disposal may have occurred near any of the storage tanks but
these are the only ones which have been identified as containing leaded tank
bottoms.
The waste managed in these areas consisted of leaded tank bottoms which are now
a listed RCRA hazardous waste (K.052). Management practice consisted of digging
a pit adjacent to the tank door sheet or manway, opening the access, dumping the
collected sludge into the pit, and finally covering the pit.
Unknown N.O.S. Tank Bottom Disposal Areas Disposal practices similar to those
used for the leaded tank bottoms may have been employed at practically any other
tanks which were cleaned prior to about 1970. The general locations of the tank
farms which may have been affected are shown on Figure 2 as the east, central
and west tank farms on the southern property.
The wastes which would have been placed in these pits include any non-leaded
tank bottom sludges (N.O.S. [not otherwise specified] tank bottoms).
26

-------
eval-B
Tankage These are 38 tanks at the Texaco facility which contain stored hazardous
waste. The wastes are classified as hazardous based upon being either listed or
characteristic wastes.
The tankage is divided into three groups based on the waste type stored. The first
group of five tanks store leaded tank bottoms which is a listed hazardous waste
(K052). Six tanks store slop oil emulsion solids which are also a listed hazardous
waste (K.049). The remaining 27 tanks store residual wastes generated from crude
oil or products. These tanks arc included since the wastes may be characteristic
wastes based on ignitability, reactivity, or possible EP-toxicity. Each group is
discussed in more detail below.
Leaded Tank Bottoms - These five tanks have been taken out of service and
all recoverable material has been removed. There arc currently 8,810
barrels of water and wastes in the tanks which corresponds to
approximately 1,500 tons.
Slop Oil Emulsion Solids - These six tanks currently contain 4,067 barrels of
water and waste, which corresponds to approximately 700 tons.
Not Otherwise Specified (N.O.S.) Tank Bottoms - These tanks arc included
in the Part A Application and the closure plan since the waste contained in
the tanks may exhibit one or more of the characteristics of a hazardous
waste. Texaco intends to perform, or has performed, testing of the wastes
to determine the need for continued management as hazardous.
Recovery Yard/Junk Yard This area is adjacent to and behind the maintenance
facilities. Only a small portion of the area is used as a junk yard which is located
directly behind the shop.
This area is used as a salvage yard for pipes, metal wastes and other equipment.
Here, valves are taken off pipes for reuse, wire is salvaged for the copper, parts
are saved from scrapped machinery, etc. The salvaged parts are stored in various
areas according to their type. Waste material is sent to the junk yard.
Periodically, a local scrap hauler is called to the plant to remove the recyclable
material. Anything remaining is landfi 1 led.
Oilv Dump (South Area) According to Texaco (WWC, 1982c), the source of a
floating hydrocarbon phase in the groundwater adjacent to the North Platte River
is a result of an oily dump. This dump (Figure 2) reportedly was used to lay
sample oil and waste oil barrels over the edge to drain them. Texaco refers to this
area as the refinery dump and shows it as being active in 1973 (WWC, 1982c). No
further details were included.
Interceptor Trench Svstem/Recharge Groundwater Recovery System Technically
the Interceptor Trench System and the recharge wells installed as part of a
hydrocarbon recovery system in the South Area meet the definition of a SWMU.
The trench system (two trenches) contains two perforated culverts which intersect
the water table and recover floating hydrocarbons. These trenches are drained to a
sump which pumps the oil water phase to a separator and excess wastewater is
pumped to the service water return ditch which is also considered a SWMU.
27

-------
eva)-B
The recharge wells and surface water bodies used to recharge the aquifer with
wastewater pumped from the recovery wells all meet the definition of a SWMU.
This waste water pumped from the water table depressant pump (i.e. not the oil
recovery pump) probably contains dissolved concentrations of organics such as
benzene, toluene and total xylenes. In addition to recharge wells, the wastewater is
also pumped to the PCS coke settling basin for recharge, thus this unit as
previously mentioned meets the definition of a SWMU.
Both the interceptor trenches, service water ditch and the PCS coke settling basin
are presented on Figure 2 while the recharge wells arc discussed in detail in the
hydrocarbon recovery system South Area discussion.
C. HYDROGEOLOGY
1.	Regional Geologic Setting
The study area is located on the southwestern flank of the Powder River Basin, a
structural and topographic basin. Approximately 17,000 feet of sedimentary rocks
fill the basin. Several of these sedimentary rock units, of Late Cretaceous age,
outcrop in the area of the refinery. Here, along the outcrop belt, the units are
erosionally truncated at the surface. In the vicinity of the refinery, the rocks have
a structural strike of about north 35 degrees west, and a dip to the northeast of 5
degrees to 8 degrees (WWC, 1981).
The sedimentary rocks in this portion of the basin were deposited in marine,
marginal marine, and continental depositional settings during the last stages of the
interior seaway. Thick marine shales, ncarshorc sandstones and interbedded
sandstones, coals, and shales were deposited. The eroded edge of these lithificd
rocks is unconformably overlain by unconsolidated sediments of Quaternary age.
These consist of eolian deposits of fine sand and silt, and alluvial sand and gravel
deposited by the North Platte River at various stages of its history.
2.	Regional Hydrologic Setting
The hydrology of the southwestern Powder River Basin is influenced by several
factors. Climate, surface water hydrology and geology all influence the occurrence
and nature of ground water.
Mean annual precipitation at Casper is 11.80 inches (Hodson, et al, 1973).
Evaporation is very high, up to several times the precipitation.
Surface water hydrology consists of perennial and ephemeral streams and is
dominated by the North Platte River drainage.
Mean annual discharge of the North Platte is given at 1,194 cfs (Crist and Lowry,
1972) for the river below Alcova Dam during the years 1933 to 1966. During the
years 1929 through 1959, the mean annual discharge below Casper (and near the
site) is given as 1,321 cfs (Hodson, et al, 1973).
There are several geologic influences on the availability, quality, recharge, and
flow components of the ground-water system. The unconsolidated, recent alluvium
along the present course of the North Platte is directly influenced by the river
stage. Recharge and discharge to the alluvial aquifer are directly tied to the
surface water hydrology.
28

-------
eval-B
The bedrock hydrologic system in this area is more complex. Partial recharge is
provided by infiltration of precipitation over permeable units. Due to the large
evaporation rate, the recharge from precipitation is probably only significant
during storms with enough rainfall to infiltrate below the depth of soil moisture
evaporation. Recharge from the North Platte River and other streams occurs
where the surface water crosses outcrops permeable enough for infiltration
(Hodson, et al, 1973). Movement of water between formations also occurs, but is
poorly documented in published literature.
Discharge is primarily from evaporation, seepage to springs, lakes, and streams,
plant transpiration and well pumpage (Hodson, et al, 1973). Regional flow
components arc poorly documented and mapped in the published literature.
Water quality is generally good for the surface water and alluvial aquifers. Eolian
and bedrock aquifers produce water of lesser quality due to soluble salts in the
Mesozoic aged rocks, principally the shales and coal beds. Waters found in
Cretaceous rocks of the Mesaverde Formation are dilute waters of calcium or
sodium bicarbonate type (less than 600 mg/1 TDS) or sodium sulfate waters with
TDS concentrations of 1,360 to 3,980 mg/1 (Feathers, et al, 1981). Recharge by
fresh surface water and precipitation probably further dilutes these concentrations
near the outcrops of these aquifers.
3. Site Geology and Hydrogeology
The Casper Texaco Refinery area is underlain by Late Cretaceous sedimentary
rocks as previously stated. Stratigraphic. units present in the site area arc shown in
Figures 4 and 5. The stratigraphic nomenclature is from the work of Wiloth
(1961), and Crist and Lowry (1972). Geologic units of interest in the site vicinity,
in ascending stratigraphic order, arc the Mesaverde Formation, Lewis Shale, Fox
Hills Sandstone, Quaternary eolian sand, and the Quaternary alluvium.
The Late Cretaceous Mesaverde Formation is approximately 1,000 to 1,150 feet
thick in the area of the Texaco Refinery. Here, the unit has an outcrop width of
nearly two miles due to its gentle dip toward the center of the basin. The members
of the Mesaverde arc the bedrock units underlying all of the facility, both north
and south of the North Platte River (Figure 6). The Mesaverde Formation is
divided into three members in this area. These members in ascending stratigraphic
order are the Parkman Sandstone Member, the unnamed middle member, and the
Teapot Sandstone Member. The geologic and hydrogeologic properties of these
units are as follows:
Parkman Sandstone Member - The Parkman is the basal member of the Mesaverde
Formation in this area. The Parkman is composed of fine to very fine grained,
micaceous, glauconitic, and calcareous sandstones (Purccll, 1961) with interbedded
carbonaceous shale and coal (Headley, 1958). The sand grains are angular and
moderately well sorted. Bedding is discontinuous with lensing and lateral pinch
out of individual beds common. Bedding ranges from thin to massive. Net
thickness of porous sandstone units is up to 250 feet in Natrona County (Headley,
1958) or about 50 percent of the unit's total thickness. Total thickness of the
member is given as 470 feet (Hodson, et al, 1973), 500 feet (Crist and Lowry, 1972),
and 600 feet (WWC, 1981).
29

-------
AGS
UTHCLCGY
GcCLQGIC
UNIT
7 ri IC X -
N53(ft!
HYCSCLCGiC
CHASACTIHISTIC
alluvium	0 ~ &0 I J
-------
H-
OQ
C
i-i
0>
Ol
<
cc
LlI
in
>-
in
(/)
UJ

Sussex Ss.
Shonon Ss.
Steele Sh.
Niobrara Sh.
Carlile Sh.
Wall Ck. Ss.
Cody
Sh.
Frontier Fm.
Pierre Sh.
Niobrara Sh.
PRINCIPAL
REGIONAL
AQUITARO
Turner Ss.
Carlile Sh.
Greenhorn Ls.
Belle Fourche Sh.
Quaternary aquifers
Middle Tertiary aquifers
Wasatch aquifers
upper Fori Union aquifers
leoky confining layer
lower Fori Union aquifers
Foi Hills and Lance oqulfers
Mesaverde
aquifer


aquifers
>

oquitord
Frontier aquifer

-------
R.79 W
R. 80 W.
v,,,, A^vOTKlMfSSis,
^v'VvXt\;Vt?OaIjiA.. \|'  "rt-^^Vy:.;-.'..; .
EXPLANATION
Qol '.'*  Alluvium
Ktp	Teapot Sandstone Member
' "*'' (MESAVEROE FORMATION)
Kfh	Fox Hills Sandstone
Kle Z~
Lewis Shale
MILES
Ku
Kpa
Kc
=3 Unnamed Middle Member
( MESAVERDE FORMATION)
Texaco
Property
Casper
SU.Y&W. k ....:0\V^\>.V^\,- ':. V. '
\ Yiv.;o ':*
locol dip
5-8
ParVman Sandstone Member
(MESAVEROE FORMATION )
Cody Shale
Figure 6
Generalized Geologic Map
Casper Texaco Refinery Area
( After Crist and Lowry, 1972 I
(Modified from Western Water Consultants, 1982 )
32

-------
eval-B
The Parkman functions as a confined aquifer in the subsurface to the east of the
outcrop belt. In this area, it is underlain by the Cody Shale and overlain by the
unnamed middle member of the Mcsavcrdc Formation, both shaly, low permeability
units. Published values (Feathers, et al, 198IJ give a porosity of 15 to 21 percent, a
hydraulic conductivity of less than 5 gpd/ft , and a calculated transmissivity of
120 gpd/ft. Expected well yields arc 10 to 20 gpm, although one well north of
Casper had a reported yield of 100 gpm (Crist and Lowry, 1972).
The Parkman Sandstone aquifer is in probable hydraulic isolation from the
potential sources of contaminants at the Texaco Refinery. This is due to the
overlying unnamed middle member of the Mcsavcrde Formation which is
approximately 350 to 400 feet thick and considered a confining unit. The
outcrop/recharge area of the Parkman is upgradicnt and up dip from the Texaco
facility.
Unnamed Middle Member - The unnamed middle member of the Mcsaverdc
Formation is composed of interbedded carbonaceous shale, thin to massive siltstonc,
sandy shale, bcntonitic shale, thinly bedded low rank coals, and lenticular beds of
fine grained dirty sandstone. Documentation is poor, but it appears the shaly
lithologies comprise 60 to 80 percent of the unit. Net thickness of permeable
sandstones and siltstones is unknown. Hydraulic conductivities of sandstone and
siltstone beds are comparable to the "uppermost aquifer" (WWC, 1983a); however,
the probable depositional environment would indicate the likelihood of these
permeable units being lenticular and laterally discontinuous. The total thickness
of the middle member could be considered as saturated below the water tabic,
however the low hydraulic conductivity and low specific capacity, high sulfate and
total dissolved solids (TDS) make the unit unfit for water supply. The literature
(Hodson, ct al, 1973; Crist and Lowry, 1972) describe the unnamed middle member
as a regional confining unit. There arc no water supply wells completed in the
unnamed middle member in the refinery area.
The middle member is the bedrock unit underlying all of the regulated units on-
site and the primary refinery area except for the portion of the Texaco property
extending northeast of the evaporation pond on the north property (Figure 6). In
the site vicinity, the unnamed middle member is approximately 350 to 400 feet in
maximum thickness. The unit probably functions as an effective barrier to
downward flow of possible contaminants to the Parkman Sandstone member
aquifer below. Lateral migration of contaminants above low permeability beds
occurring at the interface of the unnamed middle member with the overlying
alluvium or eolian sands is possible, however. The possibility also exists of lateral
migration of contaminants within any of the member's permeable beds lying at or
below this interface or the contact with the stratigraphically overlying Teapot
Sandstone aquifer. Given a basinward hydraulic potential in the Mesaverde
members, down dip and down gradient transport of contaminants could occur, with
resultant possibility of contaminant introduction to the Teapot Sandstone aquifer.
Teapot Sandstone Member - The Teapot Sandstone is the uppermost member of the
Mesaverde Formation in this area. The member is approximately 100 to 150 feet
thick based on electric logs from oil wells and logs from water wells (WWC, 1983a).
The unit conformably overlies the unnamed middle member of the Mesaverde.
Lithologically, the Teapot consists of fine to coarse grained sandstone with thin
interbeds of lignitic coal and bentonitic shale. The sandstone is thin to medium
33

-------
eval-B
bedded. Sandstone beds arc white to gray and friable. Interstitial cements are
primarily calcareous, although argillaceous cementing material has been noted
(Purccll, 1961).
The Teapot outcrops as a bluff along the North Platte River downstream from the
Texaco Refinery. The Teapot subcrops the unconformably overlying eolian and
old alluvial deposits north and south of the North Platte River. The subcrop belt
is not well defined in the area. Projections on published geologic maps (Crist and
Lowry, 1972; Hodson, ct al, 1973) indicate the subcrop belt to lie within
approximately one quarter mile east of the CEP and North Land Farm on the
north property. Due to the strike of the Mesaverde Formation, the subcrop of the
Teapot Sandstone lies about the same distance east of the easternmost tank farm in
the South Area. Borings arc not known to penetrate the Teapot on the south
property. No borings have definitely penetrated the Teapot Sandstone on the north
property; however, the boring for well M-31m encountered "interbedded gray shale
and fine to coarse grained gray sandstone" at approximately 5,102 feet above mean
sea level (WWC, 1982a). Geologic logs for borings in the North Area and South
Area arc presented in Appendices B and C, respectively.
Based on nearby borings which encountered carbonaceous shale and si I tstone (M-29
and M-20, respectively. Appendix B) the contact of the Teapot Sandstone with the
underlying unnamed middle member can only be vaguely defined in the
subsurface. The nature of this contact is not documented in the literature,
although it is probably gradational and interbedded because of the environment of
deposition.
Hydrologically, the Teapot Sandstone is considered an aquifer in the western
Powder River Basin (Feathers, ct al, 1981; Crist and Lowry, 1972; Hodson ct al,
1973). Tabulations of data from the Wyoming State Engineer's Office water well
permit files (WWC, 1982d) indicate substantial use of water from the Teapot
Sandstone within a two mile radius of the site. Because the outcrop/subcrop of the
Teapot is east of the site, the structural dip is to the east, and most importantly,
the probable potentiomctric surface decreases in elevation to the northeast
(northeastward flow), the Teapot water supply wells are all across or downgradicnt
from the Texaco Refinery. These wells arc primarily for domestic or livestock use.
Regionally, the aquifer is considered confined in the subsurface, with the
underlying unnamed middle member of the Mesaverde and the thick, overlying
Lewis Shale acting as confining units (Crist and Lowry, 1972; Hodson, et al, 1973;
Feathers, et al, 1981). This is discussed in further detail under Hydrogeology of
the North Area.
Thin interbeds of shale and bentonite probably act as confining layers to create "a
series of semi-confined to confined subaquifcrs within the Teapot aquifer" (WWC,
1981). The producing aquifer is characterized as "about 50 feet thick, although the
formation [sic] is 100 to 150 feet thick" (WWC, 1981). This has not been
substantiated during this study. Net thickness of Teapot porosity, based on oil well
data, indicates as much as 100 feet (Hcadley, 1958). Well yields from the Teapot
are generally five to 45 gpm. Hydrologic data for local water wells completed in
the Teapot aquifer are presented in Table 2.
34

-------
Table 2 llydrnloglc data arranged l> y formation for selected water well* within two wiles of I lie Casper Texaco Refinery vicinity.4
Well Owner
Well Manic
oca tIon
Hell Reported
Depth Production Orawdown
(feet) (r.PH)	(feet)
SaIn raled
TIckress
or We 11
Comple tIon
Interwa1
(feet)
EstIniated
TransmlssIvIty
(gpd/ft)
Sped f Ic
Capac1ty
(ai'm/ft)
Estimated Puni|> Tes t
Pernieali^ I I ty duration
(opd/ft )
(hours)
Hesaverde format ton ( Teaiiot Sandstone
enilier)
Tank Service Inc.
Pittman, J.
Forsbery, I.,
nirkle, V.
Miller, n.
Miller, It.
Slonck iiic
60
15
S
10
6 x 10^
3
3.3x10?
Votli 1
33-70-5l>c
60
15
45
20
6. 7x |0f
0.3
3 x 10,
Ornokliurst 10
33- 7fl-5lid
60
15
1
20
3 x 10?
15
1 .5x10,
Orookliurs I 16
33-70-51.d
60
IS
I
20
3 x 10,
15
1.5x10,
Eve Star 1
33- 7fl-5ac
60
10
30
10
2.7x10,
1.3
2.7x10,
Gall Ion t
33-7fl-5lic
60
16
12
25
2.7x|0^
1.3
1 x 10,
Latlirnp feed
33-7fl-6db
55
20
1
17
1 x IO?
20
2.4x10
Carnlyn 1
33-79-1cc
57?
22.5
330
510
I .4x10,
15
I
Green 1
33-79-2cc
51
5
11
30
2.3x10,
0.1
6
Sandy <1 7 -A
31-7(l-2Jcb
700
12
23
200
1 * l()i
0.5
5 3
Mystery 1
31-70-3Jca
775
15
)
75
9 x 10,
45
1 .2x10
Strand 10
31-7tl-34aa
300
10
70
70
2.9*10,
0.1
1 -
K-13
31-79-1Dca
120
5
40
20
2.5x10'
0.1
l x 10
II. A.
36
I
1
.5
N.A.
H.A.
21
U
2
2
2
2
3
r>
i
con
i
i
.5
Sources for data are Wyoming State Engineers Office tom , Crist I97-1. Ifodson and olliers 1973. Crist and Lowry 1972;
Dana 1962; Welti and others 1051.
Township-north, range-west, section, quarter section; quarter-quarter section; U.S. Geological Survey well numbering
sys lent.
Transmlss I v I ly estimated using T  2000 f)/5. where T  transmlssIvlty (gal/day/f t). f)  yield (gallons/minute) and
S  drawdown (feet).
Permeability estimated using K  (2000 Q/5)/l>, where K  permeability (gal/day/fI2), 0  yield (gallons/minute).
S * drawdown (feet), and 0  saturated thickness or completion Interval.
modified from; Western Water Consultants, Inc., 1981

-------
eval-B
The characterization of on-site hydrologic parameters of the Teapot Sandstone is
slightly more complex than the regional characterization. The eolian and older or
"palco" alluvial deposits overlying the Teapot subcrop arc similar in composition,
texture, and hydrologic properties. Pumping tests conducted in the North Area
"proved that the two geologic strata are in hydraulic connection and have similar
permeabilities" (WWC, 1983a). Based on this interpretation, these two units have
been defined as one aquifer and designated the uppermost aquifer in conformity
with the definition of 40 CFR section 260.10. Five single well pumping tests
conducted in 1982 indicate the uppermost aquifer has ranges of hydraulic
conductivity and transmissivity of two to 1,000 gpd/ft and 2.2 x 10^ feet to 1.6 x
10 gpd/ft, respectively (WWC, 1983a).
Recharge to the Teapot Sandstone aquifer takes place along the outcrop belt, and
possibly by leakage from the adjacent bedrock units. The leakage, if any, is
undefined. Primary outcrop recharge is probably from precipitation directly on
outcrops and infiltration from overlying unconsolidated eolian and alluvial
deposits. Infiltration of water from the North Platte River where it flows across
the outcrop belt is another possible primary source of recharge, although this is
undefined. During this study, a preliminary assessment of potcntiomctric data
from local water supply wells was made. These data, compiled from Wyoming
State Engineer files, Crist and Lowry, 1972, and several other sources, indicate a
decreasing potential toward the basin axis. This basinward gradient would create
flow towards the basin center, and consequently could conceivably introduce
contaminants into the Teapot aquifer.
Lewis Shale The Lewis Shale conformably overlies the Teapot Sandstone member
of the Mesaverde Formation. The Lewis is primarily a gray shale to sandy shale
with lenticular bodies of fine-grained sandstone. The formation intcrfingcrs with
continental deposits west of the study area. Near the Texaco Refinery, the lower
300 feet of the Lewis Shale is a thick-bedded shale which grades upward into
interbedded sandstone with decreasing amounts of shale. The unit is
approximately 470 feet thick in this area (Crist and Lowry, 1972), however the
Lewis is truncated by erosion to zero feet at its westernmost outcrop.
Hydrologically, the Lewis Shale acts as a confining layer for the underlying Teapot
Sandstone. The lower shaly portion of the unit has generally low permeability, and
is recognized in the literature as a regional confining aquitard (Crist and Lowry,
1972; Hodson, et al, 1973; Feathers, ct al, 1981). Discontinuous saturated lenses of
siltstone and sandstone yield small amounts of water (generally <10 gpm) locally.
One well in this area reportedly yielded 50 gpm, however sustained yield in the
Lewis Shale is probably much lower.
The unit outcrops or subcrops the unconsolidated surficial deposits about 6,000 feet
northeast of the refinery proper, and underlies the Excess Service Water Effluent
Ponds.
Logs for boreholes M-l through M-6b indicate the Lewis Shale is overlain by from
five to 34 feet of old alluvial deposits consisting of fine through coarse sand with
some clay and fine gravel. These deposits are overlain in turn by eolian deposits
one to greater than 55 feet thick, composed of silt and fine sand. Potentiometric
surface maps for the area indicate a southward ground water flow direction in the
deposits overlying the Lewis Shale. Three local private water supply wells located
in section 28, south of the easternmost Texaco ponds, possibly indicate a lower
potential surface in the Lewis Shale than in the overlying deposits. These three
36

-------
eval-B
wells reach total depths of 380, 460, and 480 feet below ground surface, and
produce from the Lewis Shale, presumably from lenticular sandstones within the
shale. The potential difference between these units indicates a probable poor
hydraulic connection between permeable beds in the Lewis Shale and the overlying
deposits. Borehole M-5 was drilled 40 feet into dark gray shale and abandoned as
a dry hole at a total depth of 100 feet (Appendix B). These data indicate the
saturated eolian and old alluvial deposits constitute a perched zone above the shale.
Data presented for potentiometric elevations in Lewis Shale wells (Crist and
Lowry, 1972, Plate 1) and well records from the Wyoming State Engineer's files
indicate a basinward gradient in the formation. This potentiometric surface is
poorly defined due to sparse well control.
Potential for contamination of the formation is considered low. The presence of
the lowest permeability beds in the stratigraphically lowest portion of the
formation, which is closest to the facility, would retard migration into the
permeable sandstone lenses which produce potable water from a stratigraphically
higher portion of the formation.
Fox Hills Sandstone The last bedrock unit of possible concern is the Fox Hills
Sandstone. The Fox Hills outcrops approximately two miles northeast of the
Texaco Refinery. It is considered a regional and local aquifer (Feathers, et a 1.,
1981).
The Fox Hills is a fine-to-mcdium-graincd sandstone with intcrbcddcd sandy shale
to carbonaceous shale, especially in the upper half of the unit. The sandstone is
thin to massive bedded, poorly cemented, and friable. The sandstone is about 700
feet thick in Natrona County (Crist and Lowry, 1972).
Well yields arc generally less than 20 gpm. Although the sands arc porous, Fox
Hills conductivity is estimated at 34 gpd/ft (Crist and Lowry, 1972).
Transmissivity values range from 100 to 2,000 gpd/ft, although there is some
uncertainty in these values (Feathers, et a 1, 1981). The Fox Hills forms a regional
scale aquifer system with the overlying Lance Formation (continental sandstones).
An extensive discussion of the Fox Hills/Lance aquifer system is presented in
Feathers, et al. (1981).
Potential effects on the Fox Hills aquifer from the Texaco Refinery are considered
very small. The aquifer's outcrop area lies well to the northeast of the facility.
Flow in the unconsolidated materials in the intervening area is generally to the
south. The low permeability, thick Lewis Shale is the intervening bedrock unit
and serves as an effective aquitard.
Quaternary Alluvial Deposits The alluvial aquifers in the vicinity of the Casper
Texaco Refinery are composed of unconsolidated clay, silt, sand and gravel
ranging up to cobble size. The sediments occur as discontinuous bars and lenses
along streams, with the largest deposits along the North Platte River. The deposits
underlie the floodplains and bordering terraces. Deposits along the Platte form a
blanket of irregular width and thickness which conforms to the erosional surface
cut by the Platte through time.
The alluvium consists of poorly to moderately sorted deposits of clay through
cobble size rocks. The deposits exhibit a generally fining-upward point bar
37

-------
eval-B
sequence, with coarser sands and gravels near the bottom of the alluvium and fine
gravels to sands in the uppermost portions of the deposits. Clay lenses and
moderately sorted sand lenses occur in places.
The South Area is nearly completely underlain by recent alluvium, except for two
exposed outcrops of bedrock. The outcrops are of the unnamed middle member of
the Mesavcrdc Formation. The unnamed middle member underlies all of the
alluvium in the South Area. Alluvial thickness is zero to 55 feet (Figure 7) thick.
The North Area has two separate alluvial deposits. The "lower aquifer" forms a
deposit along the inside of a major bend in the North Platte River. This alluvium
is about 700 feet wide at its widest point (WWC, 1983a), and occurs from nearly the
cast property boundary to beyond the west property boundary. The bedrock bluffs
of the exposed unnamed middle member and the Teapot Sandstone member of the
Mesaverde Formation bound the alluvium on the north.' These bedrock units also
underlie the alluvium. The deposit is bounded on the south by the North Platte
River. The alluvium here is approximately zero to 15 feet thick. Composition is
similar to the alluvium south of the river.
The second deposit of alluvium, in the North Area, occurs as a now elevated
channel fill, deposited during an earlier river stage before erosion of the North
Platte produced the elevation of the present river channel. This alluvium fills a
"horseshoe" shaped depression eroded by the "palco" North Platte. This "horseshoe"
wraps around the bedrock high (erosional remnant) which underlies the land farm.
The apparent axis of the channel lies just north of the CEP. The palco channel
was cut into the bedrock from approximately 5,110 feet above sea level to 5,080
feet above seal level. This is well illustrated by the bedrock surface contour map
(Figure 8).
This downcut channel was filled by alluvium consisting of clay to medium gravel
sized material. The sediment is moderately sorted and contains well sorted sand,
silt, and clay lenses. Clay lenses arc more common in this older alluvium than in
the more recent alluvium, based on borehole descriptions. Grain size and possibly
the composition of this deposit also differs from the more recent alluvium,
probably due to changes in sediment source areas. The older alluvium ranges in
thickness up to about 30 feet. The deposit is overlain by an irregular veneer of
eolian sand. Previous reports have designated all these materials as "eolian"
deposits. For simplicity in nomenclature, description, and hydraulic calculations,
this is probably an acceptable practice. However, the hydraulic conductivity and
other hydrodynamic parameters, including such properties as cation exchange
capacity, may be affected differently by these older alluvial deposits than by the
overlying eolian silts and sands. It should be noted that due to variable screened
intervals and other factors, results of pump/bailer tests and other tests performed
provide an "average" of this system and are not indicative of any possible
differences between the older alluvium and the overlying eolian material.
Ground water in the South Area alluvial aquifer has a general flow direction to
the north and east. The potentiometric contours are affected by the presence of
the bedrock shale outcrop near the river which apparently acts as an "island" in
diverting subsurface flow around it (Figure 9). The natural flow system is also
affected by the Refinery's hydrocarbon recovery wells and interceptor system,
which is a French drain designed to induce flow from the alluvium near the North
38

-------
OJ
vo
tout
. .iPS7A5-.:n-
^ o 7)'
OMfl
&*&
VS.*S
I :,r. 4)t* 
C-^ir.'jV
MOO
ICQlt
tXPL A HA TfON
J0
'*H4r
ISOPACH CONTOUR
*i IN FEET CONTOUR
INTERVAL 13 TEN
FEET
TEXACO PROPER T T
BOUNDARY
L'.lilVt?<>:^M.tviy.Vm >''Jjs
FIGURE 7 ISOPACHOUS MAP FOR THE ALLUVIUM,
CASPER TEXACO REFINERY
modified trom; Western Water Consultants, Inc., 1962

-------
.e>
o

5093
3090
3090
300 3
cTTirnri^; -
SOLID
WASTE
VAPOfUTION
M - 30
rorJD
7)U-3I
0
PAR M
*S-bO*3
Q*2-"tovy
U-CO
G"-'7
EJ"'91
_q r-1
	5100
EXPLANATION
LOCATION OF 3III0LI MONITOA WILL
LOCATION OF NC3TC0 WELL lITt
srep onivt point
CONTOUR ( r . . I o b o v i U.S.L.I
o	too 400 r>!
ICALI
CONTOUR IHTIAVAL 0 flft
N

FIGURE 8 : BEDROCK SURFACE CONTOURS, UNNAMED MIDDLE MEMBER
NORTH PROPERTY, CASPER TEXACO REFINERY.
modified from; Western Water Consultants. Inc.; 1982

-------

rrv*.
vV
r. 1; k/ .\T;se)'jr it ^
F * 1 / rv *... #	A
jo
o
O	.q
o-.-./ JS'
.
1400
 call
EXPLANA TtON
POTENTIOMETRIC
j)j|' CONTOUR IN fEET
CONTROL POINT! IHOfN
ON FLATf 
OROUND - WATER
FLOW DIRECTION
TEXACO PROPERTY
BOUNDARY
FIGURE 9 : GENERALIZED POTENTIOMETRIC SURFACE CONTOUR MAP AND
IDEALIZED GROUND-WATER FLOW DIRECTIONS FOR THE
ALLUVIAL AQUIFER, CASPER TEXACO REFINERY.
modified Irom; Western Water Consultants, Inc., 1982

-------
eval-B
Platte River bank to the alluvium under the South Area. The upgradicnt end of
the French drain is located near the intersection of the western boundary of the
south property and the North Platte.
Recharge to the aquifer primarily comes from the hydraulic connection with the
North Platte, infiltration of precipitation and perched water flowing overland in
the uppermost unnamed middle member of the Mcsavcrdc Formation plus possible
leakage from the middle member. Recharge has also taken place by artificial
infiltration of water through recharge wells and ponds in addition to product from
the refinery. No specific source at the refinery is known, but the presence of free
hydrocarbons in the aquifer substantiates this source.
Alluvium thickness ranges from zero to greater than 55 feet (Figure 7). Saturated
thickness of the alluvium ranges from 5 to 30 feet, with an approximately 20 foot
average thickness (WWC, 1982b). Aquifer tests were performed by Western Water
Consultants, Inc. between March 9 and April 6, 1982. "One multiple well pump and
recovery test, four single well pump and recovery tests and one bailer recovery test
were conducted at the Casper Texaco Refinery" at this time (WWC, 1982b). Based
on these tests, hydraulic conductivity was estimated to range from 2 x 10J to 8 x.
104 gallons/day/foot . Estimated transmissivitics ranged from 8 x 10^ to 6 x 10^
gallons/day/foot. Calculated average storage coefficient was 0.1 and estimated
specific capacity ranged from 30 to 100 gallons/minutc/foot of drawdown.
Gradient in the alluvial aquifer is approximately 1 foot/500 feet. Maximum
probable flow rate is approximately 22 feet/day.
Ground water in the alluvial aquifer of the north property has a generalized flow
direction to the southeast to cast toward the North Platte. Potcntiomctric contours
are relatively uncomplicated. The potcntiomctric surface is responsive to changes
in the stage of the North Platte, with which it is in direct hydraulic
communication. Recharge to this alluvium is accomplished through several sources.
Recharge from the North Platte, which is variable (and is probably mostly
discharge into the Platte at low river stage), recharge from infiltration of
precipitation, and ponded seepage emerging from the bluffs bordering the north
side of the alluvium arc all primary sources. These seeps emerge where the
relatively high permeability "upper aquifer" contacts the underlying and relatively
low permeability unnamed middle member of the Mcsavcrdc Formation at the
bluff face (Plate 1, Section C-C'). Another possible source of recharge is discharge
from the unnamed middle member into the alluvium. This recharge is undefined
in quantity and quality.
The seeps at the bluff face are the major obvious pathways for introducing
contaminants from the chemical evaporation pond and land farm areas on the
bluffs above to the alluvial aquifer. Potential for migration of contaminants
through the unnamed middle member and their introduction by discharge into the
alluvium is undetermined. Sampling by Texaco in the past has indicated the
presence of organic contaminants seeping from the bluffs into the alluvial aquifer.
Saturated thickness for the north alluvial aquifer probably averages about 10 feet.
The alluvium ranges from zero to about 15 feet thick based on boring logs.
Pumping or bailer tests were not conducted in the alluvium on the north property.
42

-------
eval-B
Several tests were conducted in the alluvium south of the river, and due to the
close similarity in composition and grain size between these two deposits, these
south property data should be applicable to the north property alluvium. As in the
south property alluvium, hydraulic conductivity in the north alluvium probably
ranges from 2 x 10"^ to 8 x 10 gpd/ft^. Due to the saturated thickness in the
north alluvium being approximately half of the saturated thickness of the south
alluvium, the transmissivity of the north alluvium should be approximately half of
the transmissivity of the south property alluvium. Gradient in the north property
alluvium and flow rates should also be approximately the same as the south
alluvium or one foot/500 feet and about 22 feet/day, respectively. Although not
stated by Texaco in their data evaluation, porosity is assumed to be 0.25.
Baseline water quality data indicate generally poor drinking water quality as
ammonia, sulfate, and TDS exceeded domestic use standards. Due to probable
introduction of contaminants from the evaporation pond/land farm area at the
upgradicnt end of the alluvial aquifer, the background water quality is poorly
defined.
Quaternary Eolian Deposits Eolian sand and silt deposits of Quaternary age
blanket the surface over a large area near the Texaco Refinery. These
unconsolidated sediments form a variably thick veneer which unconformably
overlies major portions of the bedrock units in this area. The eolian deposits occur
over much of the north property, but arc not well documented on the south
property. Several borehole logs from the south property indicate there is one to
two feet of eolian sediment overlying portions of the alluvium. Grading, filling,
and other surface disturbances in the South Area probably mask this eolian
material.
The eolian sediments are composed of well sorted silt and fine sand. These are
typically rounded and the sand grains arc "frosted." Source material for the
sediments may be primarily from Teapot Sandstone outcrops. This would explain
the tcxtural similarity of these units. The eolian sands in the local area arc
typically less than 50 feet thick (Hodson, ct al, 1973). The sands arc present as
active and inactive dunes. Deposits on the north property of the Texaco Refinery
range from generally less than eight feet thick near the chemical evaporation pond
and land farm, to about 40 to 50 feet thick in areas near the excess service water
effluent ponds (borehole log M-5, Appendix B). Some of the sediments previously
interpreted as eolian arc probably best classified genetically as older alluvium.
This interpretation is based on presence of gravels and plastic clay lenses, moderate
to poor sorting, oxidation differences (color changes), deposit geometry and
bedrock surface contours. This interpretation is made from reexamination of
various data, especially the borehole logs.
This genetic distinction may have low importance in terms of the hydrologic
system. The eolian sediments do possess high porosity and permeability. This aids
infiltration and subsequent recharge to underlying bedrock units which have much
slower infiltration rates. If precipitation events are heavy enough, the water can
infiltrate to depths below the depth of effective evaporative discharge, thereby
protecting loss of the moisture to the atmosphere. Retention of moisture by the
eolian materials is generally poor as indicated by the ineffectiveness of the four
lysimeter locations. There may be a possibility the lysimeters were not properly
used. The tubes were left open to equilibrate with atmospheric pressure rather
than applying a vacuum and sealing the tubes at the conclusion of a sampling
event.
43

-------
"eval-B
Ground water flow in the colian deposits is defined in the potentiometric maps for
the north property presented under the Hydrogeology of the North Area Section.
Subsurface flow in the colian deposits north and cast of the evaporation pond and
land farm is generally to the south, toward the North Platte River. This is
presented in several reports as the "regional flow direction," however this is only
true for the ground water in the colian deposits. The underlying bedrock units
have a flow direction to the northeast, towards the basin axis. The ground water
in the eolian deposits north and cast of the chemical evaporation pond, in the area
of the excess service water effluent ponds, is in a perched condition due to the
underlying, low permeability Lewis Shale. Where the colian deposits overlie the
Teapot Sandstone, the direct hydraulic communication probably causes the ground
water from the colian deposits to infiltrate the Teapot Sandstone.
Hydraulic parameters for the eolian deposits were not truly measured directly, as
the aquifer tests were conducted in wells screened in the older alluvium previously
described. However, in practical usage, the same values for hydraulic conductivity
previously ascribed to the "colian'/older alluvium can be considered adequate.
Contamination migration in the eolian deposits is probably rapid and relatively
unattenuatcd. The sand and silt has a low potential for sorption or cation
exchange. Filtration and possible biodegradation are the only expected
contaminant mitigation effects.
4. Hydrogeology of the North Area
The North Area of the Casper Texaco Refinery has two regulated units, the
Chemical Evaporation Pond and the North Land Farm. These units arc sited on a
topographic high overlooking the North Platte River. Figure 10 presents the
location of monitoring wells completed in the North Area. As previously stated,
geologic and well completion logs are presented in Appendix B. The topographic
high is. underlain by a bedrock high of the unnamed middle member of the
Mesaverdc Formation. The bedrock high represents an erosional feature, which
was left when the ancestral North Platte River eroded a channel to the immediate
north of the bedrock high. The contour map of the bedrock surface, Figure 8,
shows the bedrock low mapped from borings and a seismic refraction geophysical
survey (WWC, 1982d). The axis of this bedrock low lies approximately 100 feet
north of the regulated units. From this area, the axis of the palcochanncl bends
southward, towards the North Platte River where it intersects the face of the
bluffs along the river approximately 600 feet southeast of the regulated units.
Plate 1 presents Cross Sections A-A', B-B' and C-C' which are referenced hereafter
in the following sections.
The paleochannel is filled with an alluvial deposit consisting of medium to coarse
sand with fine to medium gravel common in the lower portions of the deposit. The
alluvium also contains lenses of clay. This deposit is overlain by eolian fine sand
and silt deposits of variable thickness. The eolian sediments are typically less than
eight feet thick. These sediments, both paleo alluvium and eolian, were all
described as eolian in previous works.
The bedrock low is eroded into the unnamed middle member of the Mesaverde
Formation. The Teapot Sandstone Member also underlies the eastern portion of the
bedrock low, but the location of the lower contact of the Teapot with the middle
44

-------
TEXACO PROPERTY
-BOUNDARY
M -20
M-2 J
M- 25
M - 22
M-24
L  7	M-7
~ 12
SOLID WASTE
LAND FIL L 
M-8
M - 21
CHEMICAL EVAPORATION POND
u-si
n
M- 34
M- 30
M - 52
M-33
P-24
SP-I

y  49 A

M- 36
 H
""26 M - 51 A
O
M-27
B
M-lf
L-ll
~
0
o
o
0
0
0
o
B
u- is	co	
NORTH LAND FARM
a
M -9
H
M- 29
M- 16
M - 15
M- 35
CLIFF
EAST
SPOSAL

-ASPHA
NORTH
TA N K FA R M
LEGEND
FEET
O Monitoring Well in Unnamed
Middle Member
 Monitoring Well in Uppermost
Aquifer
9 Monitoring Well in Alluvial
Aquifer
IS Nested Monitoring Wells in
Uppermost Aquifer
H Nested Monitoring Wells in Uppermost Aquifer
and Unnamed Middle Member
T Lysimeter
Monitoring Well in Seep Area
Q^Seep Area
FIGURE 10
Location of North Area Monitoring Wells
Texoco Refinery, Casper, Wyoming
Source : Modified from Western Water Consultants, I987.
45

-------
eval-B
member is conjectural to date (Plate 1, Section A-A'). The contacts were not
mapped on the bluffs along the river, and borehole data arc poorly documented
and inconclusive. Two wells which may have penetrated this contact and the
lowermost portions of the Teapot Sandstone arc M-31m and M-14d (Figure 10,
Appendix B). These boreholes intercepted sandstone with a similar description as
the Teapot. Borehole M-3 to the northeast, Figure 10, also may have intercepted
the Teapot in a stratigraphically higher portion of the unit based on the presence
of coal in the borehole. Based on these sparse data, the subcrop of the Teapot can
be considered to lie within 750 to 1000 feet cast of the regulated units. The thick
blanket of palco alluvium and colian sand overlying the Teapot are in direct
hydraulic contact with the Teapot Sandstone, as previously stated (WWC, 1982d).
Stratigraphic position, topographic position, and pumping test data substantiate
that the Teapot Sandstone and overlying unconsolidated alluvium and eolian
deposit can all be considered hydraulically interconnected. Therefore these units
collectively constitute the "upper aquifer" as defined in 40 CFR Section 260.10.
Exact relationships in the subsurface are presently undefined by borings and
geophysics. The borehole logs presented by the facility arc insufficient in
lithologic description and lack information such as penetration rates, fluid loss, etc.
which could help clarify the subsurface contacts.
The Chemical Evaporation Pond and Land Farm overlie colian sand and palco
alluvium from 21 feet thick in M-9d to 50 feet thick in M-8d. Recharge to this
deposit is taking place by infiltration from the Chemical Evaporation Pond, which
has been "refilled" with water from the North Platte by Texaco.
The infiltration of river water produced recharge to the ground-water system of
the upper aquifer underneath the Chemical Evaporation Pond, which has created a
ground-water mound. This mounding effect has fluctuated in magnitude through
time depending on the volume of water introduced to the pond. The mounding of
the water table creates an increase of gradient, and radial flow away from the
pond in all directions except south where the shale bedrock high blocks the flow
path. Flow paths diverge radially with water flowing towards the river on the
west and cast. Flow northward probably responds to change in gradient and splits
to flow southeast or southwest towards the river. The potcntiometric maps
produced by the Task Force (Figures 11, 12, 13 and 14) substantiate earlier
potcntiometric mapping. Flows to the west infiltrate the alluvium of the "lower
aquifer" which lies along the North Platte. Flows to the southeast surface as seeps
at the shale/alluvium-colian interface. Flow volumes of the seeps are not
documented.
Radial flows to the cast and north encounter the bedrock low, which would act as
a preferentially permeable "channel" compared to the confining shaly middle
member. This bedrock low may also act as a "sink" for any dense immiscible
phases present ("sinkers"). If a dense immiscible phase were present, it may tend to
collect in the bedrock low. Due to the probable subcrop of the Teapot Sandstone
along this bedrock low (see Plate 1, cross section B-B') and the probability of
recharge to the Teapot at the subcrop/outcrop, dense phases could migrate into the
Teapot aquifer. Dissolved phases may also be introduced to the Teapot through
recharge at the subcrop.
Potentiometric maps of the North Area plotted by Western Water Consultants, Inc.
are accurate for the eolian sand and paleo alluvium north of the river. However,
published data. (Crist and Lowry, 1972, Plate 1) on the Teapot Sandstone indicate a
46

-------
TEXACO PROPERTY
^BOUNDARY
 *-20
H-7
O 5 /2 /. 5
5f 21. 7
SI 21.0
CHEM
flPOTTATION POND
5/20.3
3/2/. /
  31
 - 34
 5/20. 2
5/20
#5/2/
ORTH
5 f/0. 4
CL IFF
5/24
094.
5/24.3
50 9 7. J
PSA)
5076.3
M-l8o
SP-0
/
M - 50A
5079. 6
SP-26 S
SP-9
SP-31
asphalt disposal
SITE
NORTH
TANK FARM
BRIDGE
LEGEND
FEET
O Monitoring Well in Unnomed
Middle Memtier
 Monitoring Well in Uppermost
Aquifer
Q Monitoring Well in Alluvial
Agui fer
SI Nested Monitoring Wells in
Uppermost Aquifer
B Nested Monitoring Wells in Uppermost Aquifer
and Unnamed Middle Member
~ Lysimeter
Monitoring Well in Seep Area
Seep Areo	CONTOUR INTERVAL = I foot
FIGURE 11
Potentiometric Surface Map
Upper Aquifer
October, I982
Texaco Refinery Casper, Wyoming
(Approx. Hj^torlc High)

-------
TEXACO PROPERTY
-BOUNDARY
 M-20
5/20. 8
5(21. i
U-21
# 5117.3
5120. J
HEMICAL EVAPORATIO
5/19. 6
SOLID WASTE
LANDFILL
M-21
 5U9. 7
M - 3 1
M- 13	SI
5119. 7	5118.7
NORTH LAND FARM
M- 34
 5118. 9
5119. 8
M-29
 5 118. 4
5119
M-14
511 7 4
SP-
5UI. 5
M- 16
5UQ. 2
5U7. 4
CLIFF
5120
H *26
5095. 9
5 P - 29
SP-4
5103.2
5110
* .M-I2S
SP-28
SP-8	Q
9	
SP-7	SP-23
SP-IO

SP- 26
SP-5
SP- 9
3CS/. I
O
7) Oj3
o
S P* 3 I
asphalt disposal
SITE
NORTH
TA N K FA R M
BRIOGE
500
LEGEND
FEET
O Monitoring Well in Unnamed
Middle Member
 Monitoring Well in Uppermost
Aqui fer
Q Monitoring Well in Alluvial
Aqui fer
SI Nested Monitoring Wells in
Uppermost Aquifer
8 Nested Monitoring Wells in Uppermost Aquifer
ond Unnomed Middle Member
~ Lysimeter
Monitoring Well in Seep Areo
Seep
Area
CONTOUR INTERVAL = 5 feet
FIGUR E 12
Potentiometric Surface Map
Upper Aquifer
September, I985
Texaco Refinery, Casper, Wyoming
48

-------
TEXACO PROPERTY
-BOUNDARY
 M - 20
5120.6
S// " - 22
<9/ 5120. I
3120. 8
POND
3/19.4
U-21
 5/J9.5	, _
u-;3	a,/
3//9.^N0RTH land farm
M - 23
m 5118.1
LAN D F1C
5H9. 4
m- e
5//4.0
 5/18. 6
5II4>
51/7.0
5/17. \
X
5/18
CLIFF
&io
M- 19
5096 6
092. S
5/14
5///. 5""3

SP-2A
5 /14 0
SP-iO
SP-8 Q
	 ~/9P
SP-7	SP-22
0 Q
SP-5 wSP-9
/
[S0 79.0
m - 50 a
SP - 260
SP-JI
asphalt disposal
SITE
NORTH
TA N K FA R M
LEGEND
BRIDGE
O Monitoring Well in Unnamed
Middle Member
o Monitoring Well in Uppermost
Aquifer
O Monitoring Well in Alluvial
Aqui fer
H Nested Monitoring Wells in
Uppermost Aquifer
8 Nested Monitoring Wells in Uppermost Aquifer
qnd Unnamed Middle Member
~ Lysimeter
Monitoring Well in Seep Area
FEET
Seep Area
FIGURE 13
CONTOUR INTERVAL" I foot
Potentiometric Surface Map
Upper Aquifer
December, I985
(Approx. Historic Low )
Texaco Refinery, Casper, Wyoming
49

-------
TEXACO PROPERTY
-BOUNDARY
121. 0
5121. 6
SH7. S
CHEMICAL EVAKTRZTn^^p^ND
3/20. 6
WAST7E
F I
n-21
 5/20.a
5^
J	M- J
a	 5119.5
5II9.B
5124.3
M- 8
M- i
 5121. S
ORTH LAND FAR
//9 ^M-29
 5119.8
5117. 9
5120.8
M-l<
5(18.7
5118.0
509 6.8
5085.&
M- 33
UB. b U /
?k

V
asphalt disposal
NORTH
TA N K FA R M
BRIOGE
500
LEGEND
FEET
O Monitoring Wall in Unnomed
Middle Member
 Monitoring Well in Uppermost
Aquifer
O Monitoring Well in Alluvial
Aqui fer
O Nested Monitoring Wells in
Uppermost Aquifer
8 Nested Monitoring Wells in Uppermost Aquifer
ond Unnamed Middle MemBer
~ Lysimeter
l Monitoring Well in Seep Area
Q^Seep Areo
CONTOUR INTERVAL = I foot
FIGURE 14
Potentiometric Surface Map
Upper Aquifer
September, I987
Texaco Refinery, Casper, Wyoming
50

-------
eval-B
basinward (northeast) gradient and flow direction for this aquifer east of the site.
The existing monitor wells do not substantiate this because few are probably
completed in the Teapot and none arc completed in the Teapot to the cast where it
is overlain by the confining Lewis Shale. Local water supply wells completed in
the Teapot Sandstone cast of the site, and tabulated by Western Water Consultants,
Inc. (WWC, 1982d) from data held by the Wyoming State Engineer's Office, also
substantiates a probable northeastward decline in the Teapot's potentiometric
surface. Due to poor elevation and screened interval control, these data are
difficult to obtain accurate potential elevations from. Careful re-evaluation of the
data from water supply wells in this area may possibly allow accurate potential
maps to be drawn for the Teapot Sandstone. An evaluation of the ground-water
monitoring system in the North Area is discussed in detail in Section D.
Potentiometric contour maps were constructed by the Task Force for the
approximate average historic high water levels in the uppermost aquifer in
October, 1982 and the approximate historic low in December, 1985. These arc
presented in Figures 1 1 and 13, respectively. Both maps show approximately the
same configuration with a prominent mound at the Chemical Evaporation Pond.
Flow directions and gradients arc approximately the same for both maps.
Fluctuations of the water level for individual wells range from about five to six
feet in monitor wells close to the Evaporation Pond to only one tenth of a foot in
monitor well M-23 cross gradient and located several hundred feet from the pond
(Figure 10).
One anomalous feature, a potentiometric "low", shows up on the map constructed
for the September, 1987 water level measurement event (Figure 14). This low is
also indicated in a potentiometric map constructed by Texaco for June, 1987 (WWC,
1988). These lows arc unexplained. Review of the data docs not indicate a
transcription or measurement correction error.
The hydraulic properties of the geologic units of the North Area are tabulated in
Table 3. These data were compiled from various reports by Western Water
Consultants, Inc., who performed single well pumping tests and bailer tests at nine
wells. Laboratory permeamcter tests were also conducted on two cores from the
unnamed middle member. The Dcrmcamctcr tests measured vertical hydraulic
conductivity at 2 x 10 gpd/ft and 8 x 10*4 gpd/ft . No description or other
analysis of the cores was provided, and it is assumed they were from the shaly
lithology portions of the member. Data for tests of two wells (M-51Am and M-
51Ad) completed in shale gave hydraulic conductivity values of 0.2 gpd/ft . The
unnamed middle member is predominantly a shaly lithology and can generally be
considered a confining unit, especially because of its thickness of 350 to 400 feet.
Sandy siltstone lenses however have a conductivity comparable in magnitude to the
"uppermost aquifer." Tests in wells M-8d and M-lOd, which are screened in shale
and silty sandstone lenses, respectively, had hydraulic conductivities of
approximately 100 gpd/ft . It is unknown how much communication the relatively
permeable lenses have with the overlying unconsolidated deposits of the uppermost
aquifer. The vertical gradient between nested wells M-51Am and M-51Ad, screened
seven feet and 27 feet into the shale of the middle member, respectively, showed a
0.05 downward gradient in the unit. Lateral continuity of the permeable lenses
within the unnamed middle member is probably restricted. Due to this, the long
distance lateral transport of potential contaminants would be confined to the
permeable lenses only. Leakage to other units is possible. No documented water
supply wells are completed in this unit in the vicinity of the Texaco Refinery.
51

-------
tab- f
slh
Geologic Unit
Eolian Sand
Paleo Alluvium
Recent Alluvium
Teapot Sandstone
Unnamed Middle Member
-	shale
-	si Itstone/sandstone
-	permeameter tests
Vertical permeability
(2 tests)
Est imated
Hydraulic Conductivity
2 to 1000 gpd/ft2
2 to 1000 gpd/ft2
2 x 103 to B x 104 gpd/f
-2 to 1000 gpd/ft2
0.2 gpd/ft2
100 gpd/ft2
2 x 10"2 gpd/ft2
8 x 10 * gpd/ft2
Table 3
Hydrologic Properties
Worth Area Geologic Units
Estimated Transmissivity
2.2 x 102 to 1.6 x 104 gpd/ft
2.2 x 102 to 1.6 x 10* gpd/ft
1.2 x 10"1 to 3.3 x 105 gpd/ft
7.5 x 102 to 1.6 x 10^ gpd/ft
Gradient Range
-1 foot/100 feet
-1 foot/100 feet
-1 foot/500 feet
-1 foot/100 feet
undef ined
-1 foot/100 feet
-1 foot/100 feet
Calculated
Hax imun
Flow Veloci ty
1.5 ft/day
1.5 ft/day
22 ft/day
1.5 ft/day
0.01 ft/day
0.2 ft/day
Data compiled from:
Western Uater Consultants, Inc., 1982 and 1983

-------
eval-B
Vertical gradients at the North Area were calculated for well nests. All water
level data are from 1987. These data are presented in Table 4. Downward
gradients were observed at seven well nests. Upward gradients were observed at
three well nests. The largest downward gradient, 0.56, was observed at the M-6
well nest (Figure 10). This probably represents the downward flow component into
the Teapot Sandstone from the water in the eolian deposits south of the Excess
Service Water Effluent Ponds. The borehole logs for holes near these ponds
indicate a variable thickness of eolian sand overlying shale. The borehole log for
M-5 encountered 40 feet of shale near the M-6 well nest. Borehole M-5 was
abandoned as dry. It is probable the water in the eolian deposits is perched over
this shale and rapidly infiltrates the Teapot Sandstone wherever erosion has
exposed the Teapot through the shale or where the shale tapers to an crosional zero
thickness knife edge at the shale/Teapot contact. This shale may be the Lewis
Shale which stratigraphically overlies the Teapot Sandstone.
The next larger downward gradients were observed in well nests M-9, M-10, and M-
1 1 southeast of the Chemical Evaporation Pond (Figure 10). The effect of the
ground-water mound under the pond is probably responsible for determining the
magnitude of these gradients.
Well nests at M-7 and M-14 both exhibited upward gradients of 0.02. Well nest M-
31, between M-7 and M-14 nests, has a downward gradient of 0.03. Explanation for
this distribution is lacking, however it may be associated with the configuration of
the bedrock low as these well nests arc all located along the bedrock depression
(Figure 8).
Hydraulic connection of.the uppermost aquifer to the alluvium along the North
Platte River (lower aquifer) occurs through the seeps along the bluffs southeast of
the Chemical Evaporation Pond, by probable direct connection of the uppermost
aquifer adjacent or overlying the alluvium west of the pond, and possibly by
downward leakage into permeable siltstone lenses in the middle member of the
Mesaverde which could migrate laterally to the bluff face for discharge or
subsurface leakage to the alluvium.
The alluvium of the lower aquifer is situated between the bluffs and the North
Platte River. No pump or bailer tests were conducted in this alluvium. Five tests
conducted in the correlative alluvium south of the river indicated hydraulic
conductivities of 2 x 10^ to 8 x 10 gpd/ft (WWC, 1982d). This aquifer is zero to
greater than 15 feet thick with a saturated thickness of about 10 feet, depending
on river stage. The direct hydraulic connection of the alluvium to the river is
responsible for primary recharge, with recharge also coming from the uppermost
aquifer. Discharge is also primarily into the North Platte. The gradient is low,
approximately 1 foot per 500 feet. Estimated maximum flow rates are about 22
feet per day (WWC, 1982d). Attenuation of pollutants from the uppermost aquifer
is probably by discharge to the North Platte and dilution. The North Platte creates
a hydraulic barrier (discharge point) to any migration further southward.
In summary of the potential contaminant pathways in the North Area, the
principle potential water supplies affected are the North Platte River and its
adjacent alluvium, and possibly the Teapot Sandstone aquifer northeast (down dip
and probably down gradient) of the site. Both of these aquifers and the surface
water are used for water supply east of the site.
53

-------
tab-g
slh
Table 4
Vertical Potential Gradients Determined from Well Nests, North Area
Uell #
Screened Interval
Midpoint
of Screen
Static
Water Level
Date of
Measurement
Screen
Elevation
Di f ference
Stat ic
EIcvat i on
Di fference
Gradient
D i rect ion
of Gradient

M-6a
H-6b
H-7s
M-7d
H-8s
H-8d
M-9s
H-9d
H- 10s
H- 10m
H-11 s
H-11d
H-Ks
H-Ud
M-31s
H-31m
M-50AS
M-50Ad
H-51As
H-51Am
H-51Ad
27.0
19.0
23.5
49.0
14.0
67.0
18.0
34.0
19.5
29.0
18.0
44.0
22.0
44.3
27.1
41.8
18.0
52.0
10.0
40.0
61.0
-	30.0
-	24.0
-	26.5
-	52.0
-	17.0
-	70.0
-	21.0
-	37.0
-	22.5
-	32.0
-	21.0
-	47.0
-	28.0
-	50.3
-	33.1
-	47.8
-	21.0
-	55.0
-	13.0
-	43.0
-	64.0
28.5
21.5
25.0
50.5
15.5
68.5
19.5
35.5
21.0
30.5
19.5
45.5
25.0
47.3
30.1
44.8
19.5
53.5
11.5
41.5
62.5
5152.8
5156.7
5121.4
5121.8
5123.8
5120.7
5124.9
5122.2
5121.8
5120.7
5125.7
5122.0
5118.9
5119.4
5119.8
5119.3
Ho Data
5121.8
5116.0
5117.0
5116.0
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
12/14/87
9/14/87
9/14/87
12/14/87
12/14/87
12/14/87
12/14/87
7.0'
25.5'
53.0'
16.0'
9.5'
26.0'
22.3'
14.7'
34.0'
30.0'
21.0'
3.9'
0.4'
3.1'
2.7'
1.1'
3.7'
0.5'
0.05'
3.9
7.0	= 0:56
0.4
25.5 = 0.02
3.1 =
53.0 0.06
2.7
16.0 = 0.17
1.1
9.5 = 0.12
3.7
26.0 = 0.14
0.5
22.3 = 0.02
0.5
14.7 = 0.03
Downward
Upward
Downward
Downward
Downward
Downward
Upward
Downward
1.0'
1.0'
1.0
30.0 = 0.03
1.0
21.0 = 0.05
Upward
Downward
1 Uater Level Data; Uestern Water Consultants, Inc., 2/29/88

-------
eval-B
The potential for contamination of the Teapot aquifer is undefined at the present
time. Testing of down gradient Teapot wells for contaminants is recommended, as
is additional characterization of this aquifer on-site.
Potential for contamination of the paleo alluvium/colian deposits and the unnamed
middle member of the Mesaverde also exists and has been documented locally.
This is not considered to be as great a concern for contaminant ingestion by people
or livestock as these units are not used for water supply. The primary concern for
these units is their documented and possibly some still undocumented effects on
the Teapot and alluvial aquifers which they recharge to a greater or lesser degree.
5. Hydrogeology of the South Area
The South Area of the Casper Texaco refinery is located on the floodplain along
the south side of the North Platte River. Covering the floodplain is a blanket of
alluvium deposited by the North Platte River. Figure 15 presents the location of
monitoring wells completed on the South Area. Geologic and well completion logs
for the South Area arc presented in Appendix C. The alluvium consists of
unconsolidated fine to coarse sand with variable amounts of fine to coarse gravel.
Underlying the alluvial deposits is the bedrock subcrop of the unnamed middle
member of the Mesaverde Formation. The unnamed middle member of the
Mesaverde consists primarily of shale with minor amounts of siltstonc occurring as
discontinuous lenses.
The unnamed middle member of the Mesaverde Formation is defined as a
confining unit in the literature (Hodson, et al., 1973; Feathers, et al., 1981; Crist
and Lowry, 1972). The member is predominantly shale as previously discussed.
Descriptions of the outcrop along the North Platte River indicate the unit here
consists of bentonitic siltstonc and claystone. One well, SS-8, was "located within
30 feet of the North Platte River and drilled to a depth approximately 35 feet
below the surface elevation of the river" (WWC, 1982b) and was dry at depth.
A bailer recovery test on well SS-5 gave an estimated hydraulic conductivity of 8.9
x 10"^ to 1.4 x 10 gpd/ft^. Transmissivity for this unit based on 13.5 feet of
saturated thickness was calculated at 1.2 x 10*' to 1.9 x 10 gpjl/ft. Core samples
from three wells gave vertical conductivity values of 2.2 x 10 to 1.1 x 10"4
gpd/ft . The vertical conductivity is two or three orders of magnitude lower than
horizontal conductivity as pointed out by Western Water Consultants, Inc. (WWC,
1982b. This is the normal case in most stratified sedimentary rocks. The dip of
the strata does however expose the eroded horizontal "edges" of the strata to
infiltration. Therefore the horizontal conductivity would be regarded as the "best"
estimate for indicating fluid flow.
As in the North Area, there are no known water supply wells producing from the
middle member in this area. Thicknesses of the member are probably in excess of
250 feet under the site. Published values of 350 to 400 feet thickness are for a
maximum section. The Texaco Refinery is located in the middle of the outcrop
belt where the dipping strata are erosionally truncated, therefore they are not at
full thickness. All these properties indicate the validity of designating the
unnamed middle member a confining unit.
The alluvium is the only aquifer present in the South Area. Extensive alluvial
deposits equivalent to this alluvium lie east and west of the site. Thickness of
55

-------
INTERCEPTOR
TEXACO PROPERTY "est"
BOUNDARY
BRIOGE
ApproilnOl Locution qi
Clor Ooi r tr
Intlo 1 ltd Olln i9i t
PREClP. a ACCEL
BLOW DOWN PONO
INT  NCtPTOR SYST tU
EAST
1972
SPARC
STORM PONO
BAROMETRIC
LAGOON
*-
li-toi f
STORM
WAT  R
SURGE
ik  it
PCS COKE
SETTLING
PONO
ll-t'- *li
WEST TANK FARM
S W N
""."'T H...,
o oo o oo
ii-ir
LAND
lit' CENTRAL tank farm
AREA
LEASED TO
GREAT LAKES
CARBON CORP.
OFFICE
MAIN PROCESS AREA
LAST
TANK FARM
TRUCK
MAINTENANCE
,.10 PLANT RECOVERY &
STORAGE YARO
LOADING
AREA
ROAD OIL
TANK FARM
LtCLNU
 Munifor Wei I
o Reihurqe Well
a Hecoweii Wei I
j beep Location
^ 6 Number
  Prope'ly Houndary
F IGUR E IS
FEE T
Monitoring Well, Recharge Well
and Recovery Well Locations
Soulfi Amu
Teioco Refinery, Casper, Wyoming

-------
eval-B
alluvium ranges from zero to greater than 55 feet (Figure 7). The deposit covers
the entire site except for bedrock outcrops in the northeast and southwest portions
of the area. The alluvium is underlain by, and fills, a palco channel cut into the
underlying bedrock by the North Platte River. Figure 16 presents a bedrock
contour map constructed by the Task Force which shows evidence of this palco
channel. Saturated thickness of the alluvium ranges from approximately five feet
to 30 feet. An average saturated thickness for the alluvial aquifer has been given
as about 20 feet. The Task Force evaluation supports this as approximately
correct.
During March and April, 1982, pumping and bailer recovery tests were performed
on four wells and single well pumping tests were performed on three wells in the
alluvial aquifer. These data have been tabulated by Western Water Consultants,
Inc. (WWC, 1982b). Hydraulic conductivyics for the alluvium were calculated to
range from 8.3 x 10 to 2.1 x 104 gpd/ft~. Estimated transmissivitics ranged from
7.6 x 103 to 3.3 x 105 gpd/ft.
Gradients for the alluvial aquifer vary due to the bedrock high, man-made
structures, pumping, and natural slope. Calculations on "local" scale maps by
Western Water Consultants, Inc. (WWC, 1982b) give a gradient of 50 feet/mile.
Task Force measurements of potentiomctric maps of the site indicate gradients
ranging from approximately one to two feet per 600 feet. The gradients near
pumped wells would be much steeper but available map scales and data do not
allow quantification of this.
Flow directions arc generally cast and north for the central portion of the site
(Figure 17), while flow for the southeastern corner is to the northeast/east (Figure
18). The bedrock high of low conductivity shale in the northeast portion of the
area creates a diversion of flow around it. Perched water is documented to occur
along the east side of the high. This is an inconsequential differentiation,
however, as the entire aquifer overlies the shaly bedrock. The potcntiometric
surface map for the southeast corner of the facility (Figure 18) shows a flat
gradient at the corner with general flow to the east towards the Little America
Refinery. Insufficient data exist to evaluate seasonal fluctuations.
A potential for mistakes in contouring of the potentiomctric surfaces and in
prediction of flow directions in the central portion of the South Area is possible
due to the presence of an immiscible hydrocarbon phase on the water table.
Hydrocarbons are documented to occur in a relatively large part of the South Area.
Water level data measured before May 8, 1985 are not corrected for depression of
the water table by the hydrocarbon phase. This can have a significant effect on
potentiomctric contour maps. If these uncorrected data are used, anomalous or
incorrect potentials and flow directions may result.
Flow directions and gradients are also modified by several man-made features. An
interceptor trench enters the area from the northwest. This trench induces flow to
the alluvium. Other interceptor trenches parallel the North Platte River. These
trenches arc excavated to a depth below the water table. They function as a cut-
off or open drain where hydrocarbon accumulations can be removed from the
water table. During pumping, the gradient near these trenches would steepen.
A 'clay barrier' (ground-water barrier) was installed during the 1950's. This
barrier parallels the North Platte and is located just south of the river. It extends
57

-------
INlLHCff TON
iT S I I M
WtSI
1*72
TEXACO PROPERTY
/^BO^DARY
/ <=> ^ "o	/
pptjiiiiijit
hhtc ir* a Acct l
OlOa OOWM HO NO
IN 1 L HC I *' K)N
bloNU PONU
BAHOMtT RlC
^vA-AGOOK.
^orth p. ^7
	IT
O
,|
--MCS CO>
SWR
O I f C M
west tank
MAIN .}
OFF IC
M.,n p lor Wcl I
MAIN P\0Ct S
0ti
CARfaof>sCOHP
Ki-i >nir g e We I I
e if Well
IRUC K 
loading
AH E A
IN I l\ANC t
,PLAfJ^
V; ton
ROAD OIL
TAN K FARM
U fJu ruber
mHj teei mSl
FIGUHE 16
60
65
70
Appro* nno le Top of
Bedrock Erosionul Surface
Texaco Refinery, South Area
Task, Force Analysis

-------
INTERCEPTOR
TEXACO PROPERTY *IrVsi"
^-BOl^OARY ^^4
19 72
Ti
BRIDGE
A p p! Q 11 nt0"
Clo.
InitOiltd olll' ilJ t) /
PREC iP a ACC t L
BLOW OOWN POND
091. J
ACCC
IN I I MC( PION
IAS T
19/2
SPARC
SIOHU POhO
BAHO
COON
(I '201 
IUHH
Mil. t
WEST TANK FARM
A 
U4I
CENTRAL TANK FARM
I. AND
FARM
AREA
I. L i. L N [)
 ii- rMII
CESS AREA'
LE as I U TO
GREAT I AKt
I AS I
f"A N f ^ AH
CARBON CON
A
Kb . f()i g e We I I
FOUO fl MSL Io contour
F IG U R t 17
PolentionieIr ic Map
U-5-85
Recovery Syslen) In Operation
Task Force Analysis
South Area
Texaco Refinery, Copper, Wyoming

-------
IN I t HCCP10N
TEXACO PROPERTY ".is'"
 BOUNDARY
b Wi DGE
A Pl>f 0 *  I  lvK.OIiUft ul
C Ij i (j
I A  f 0 I t  >1 Q f I  ' t lJ S /
phtc ip a Accti
MlO* DO*N PC no
n i l wet m oh	11
L *!> I
i 'Jfi
SP AH
STONM POND
8AR0MC T HIC
LAGOON
 s
P/Of/e
ft-4
ir*oi 
SlOnM
* A T I R
SU C t
POkO
%"
n 
sail n	so*) } u ii
i04 > }i
legend
	Monitor Wot I
o Recharge ' Well
*	Recovery Well
c} Se . ? Lcc .t *or
S dumber
_ Qirection of Groundcolor Flo*#
CD
O
FIGURE 18
Poleni lometr ic Surface
Southeast Area
January, 1987
Task Force Anolysis
Texoco Relmcry, Cojper, WyominQ

-------
eval-B
from the bedrock high to the west about 400 feet. This presumably acts as a dam
to hydrocarbons migrating toward the Platte. Some of the effect of these
structures on the local flow paths is unknown although Figure 18 appears to
indicate an effect. The probability of leaks or breaches in the containment
structures is suggested by the presence of hydrocarbon seeps along the bank of the
North Platte.
Pathways for potential migration of contaminants off-site arc limited. The palco-
channel appears to direct flow around the bedrock high in the northeast corner of
the property. This pathway may allow contaminants to flow eastward around the
bedrock high and the interceptor system, although insufficient data exist to
document this. The lowest areas of the paleo channel may act as 'sinks' for dense
phase immiscibles. These could conceivably infiltrate siltstone lenses in the
unnamed middle member and migrate laterally, however the effects from this
possible pathway arc considered to be minor on water supply aquifers.
The major impacts from the contaminants would probably be to the North Platte
River. Continuing seepage around the barriers and interceptor system allows
contaminants to reach the river. Escape of contaminants to the cast, around the
bedrock high and through permeable lenses in the middle member arc possible
pathways to the river. While no bedrock aquifers underlie the South Area,
migration to the northeast of contaminants may impact the Teapot aquifer. This
pathway is presently undefined and conjectural. To reach the subcrop of this
aquifer, migration off-site to the northeast must take place. The distance to the
subcrop of the Teapot Sandstone from the eastern boundary of the waste
management area is not defined. Characterization of the uppermost aquifer
including the Teapot Sandstone is required under 40 CFR 265.90(a).
D. ground-water monitoring system
Ground-water monitoring at the Texaco facility began in the 1940's. Dozens of wells
were installed in the South Area between 1947 and 1957 to define the hydrogcology of the
area, and to define the thickness and arcal extent of oil contamination existing at that
time. In the early 1980's numerous wells were installed in both the South and North
Areas in an attempt to bring the system into compliance with State and Federal
regulations. A minor number of wells have been installed since 1982 in both areas. As of
August, 1986, at least 208 wells exist at the facility. Most are still in use today for water
quality and/or water level measurements. A minor number of wells were and are used for
production, oil recovery, injection and pumping and observation purposes.
Most monitoring wells at the Texaco facility have a unique alpha-numeric designation. In
general, the M- and SP- series wells are located in the North Area, designed to monitor the
uppermost aquifer and unnamed middle member, and the alluvial aquifer, respectively.
Some of the wells located in the North Area are nested. The alpha-numeric sequence in
these wells is followed by an "s, m or d," indicating shallow, medium, or deep. In
addition, some well designations are followed by an "A", indicating alternate. The South
Area predominantly consists of simple numeric and SS- series wells. The numeric series
wells were installed in the 40's and 50's, with the SS series installed since 1981.
For clarification purposes, the remainder of this Section is subdivided into four major
Subsections. Subsection 1 assesses the current ground-water monitoring system under
interim status in the North Area. The second Subsection assesses the proposed ground-
water monitoring system of the North Area for permitting purposes. Subsection three
61

-------
evai-o
details the regulatory adequacy of both the interim status and the proposed ground-water
monitoring systems mentioned above. Finally, Subsection 4 assesses the South Area
ground-water monitoring system, including a discussion of the oil recovery system
currently in place. Tcxaco's Sampling and Analysis Plan, and past water quality data will
be assessed in Section E of this report.
1. Ground-water Monitoring System under Interim Status (North Area)
Two units are currently subject to the regulatory requirements of 40 CFR 265
Subpart F. These arc the North Land Farm, currently operating under interim
status, and the CEP, a former interim status unit which, according to Texaco,
ceased excepting waste in June 1982. A Part B Permit Application has been
developed by Texaco and was received by U.S. EPA Region VIII in 1985. The land
farm will be operated under interim status until such time as a decision on
whether to grant or deny a permit is issued. The CEP was operated under interim
status until September, 1986, when the pond was clean closed under 40 CFR 265.
Because wastes were not disposed of in the CEP after July 26, 1982, ground-water
monitoring pursuant to 40 CFR 264 is not required.
a. History of Interim Status Monitoring
As part of the ground-water monitoring requirements of 40 CFR 265,
Texaco installed four monitoring wells near the CEP in early 1982 (WWC,
1984b). One well was designated as an upgradient well (M-7s), and three as
downgradient (M-8s, M-lOs and M-5IAs) (Figure 10). These four wells
served as the detection monitoring system for the CEP. Detection
monitoring wells specific to the North Land Farm have not been designated
by Texaco under the interim status program. It should be noted that 25
monitoring wells existed in the North Area prior to the first round of
sampling during March 1982. Analytical results of this sampling event
indicated that ground water was degraded below and downgradient of the
CEP and North Land Farm. During the remainder of 1982 and again in
1984, a total of 52 additional monitoring wells were installed in the North
Area.
Because of the degraded ground water known to have existed in early 1982,
Texaco implemented what they state is a "voluntary" ground-water
assessment program. The Task Force considers this to be an assessment
monitoring program under 40 CFR 265.93(d). This program consisted of
monitoring 23 wells in the vicinity of the CEP and North Land Farm.
These wells were used to obtain water level and ground-water quality data
on a quarterly basis. Data have been collected semi-annually or annually
for the other wells in the North Area. This program remains virtually
unchanged presently, with the exception of eight additional wells which arc
monitored on a quarterly basis.
Texaco has maintained that since the inception of the assessment program,
the degraded ground water is due to leakage from the CEP, and not the
North Land Farm. According to Texaco, "unsaturated zone monitoring data
collected under the pond and North Land Farm during interim status
confirm that the pond, and not the North Land Farm, is the source of the
groundwater quality degradation" (Texaco, 1985). Texaco further maintains
that because contamination has not migrated from the land farm.
62

-------
compliance monitoring (40 CFR 264.99) or corrective action monitoring (40
CFR 264.100) is not appropriate under operating standards regulations, and
that detection monitoring (40 CFR 264.98) is the alternative. The detection
monitoring program proposed by Texaco in their Part B Application is
assessed in Subsection 2.
The chemical evaporation pond ground-water monitoring system, although
currently operating under 40 CFR 265.93(d) assessment monitoring, will be
subject to 40 CFR 264.101 which addresses correction action from SWMUs as
this unit docs not meet the regulatory definition of a regulated unit under
40 CFR 264.90 (i.e. ceased receiving wastes in June, 1982).
b. Assessment Program Under Interim Status
The assessment program implemented in 1982 was designed to determine the
rate, extent and concentrations of contaminants in the ground water in the
North Area. As was introduced earlier in this report, two HWMUs and four
SWMUs exist in the North Area. They include the North Land Farm and
CEP (HWMUs), and the Asphalt Landfill, North Tank Farm, Solid Waste
Landfill and the Excess Service Water Effluent Ponds (SWMUs). All the
above units have at least some potential to contribute to the degraded
ground water. With the exception of the wells designed to monitor ground
water near the Excess Service Water Effluent Pond (Figure 19), the
assessment program cannot differentiate between the remaining units in
terms of detecting a release from a single unit.
According to Texaco, monitoring frequency for each well is defined as
follows: If contamination has been detected, that well will be monitored
quarterly [40 CFR 265.93(d)(7)(i)]. The monitoring frequency of wells with
contamination will continue on a quarterly basis until that well achieves
water quality objectives (as set forth by Texaco) for four consecutive
quarters. If contamination has not been detected, that well will be
monitored yearly. Because a potential exists for most wells located in the
North Area to exhibit contamination, all wells were assessed for design,
placement, and construction deficiencies.
According to well inventory sheets and well completion details, 77 ground-
water monitoring wells were installed within the North Area between 1981
and 1984. Locations of all wells in the North Area arc presented in Figures
10 and 19. The majority of wells installed in 1981 and 1982 were to define
the geology and hydrogeology near the North Land Farm and CEP (Texaco,
1983). Two additional wells were installed on March 29, 1984 (M-36 and SP-
28). Four more were installed in September of 1984 (SP-29 - SP-32) to
characterize water quality in the alluvial aquifer near the North Platte
River (WWC, 1984b).
Currently, 65 weils are monitored for ground water quality. Of the 77 wells
in the North Area, 12 records of well completions were not provided to the
Task Force. Of these 12, six wells are currently used for monitoring
purposes. These are SP-1 and SP-31 (uppermost aquifer), SP-2 and SP-4A
(unnamed middle member), and M-12s and SP-26 (alluvial aquifer). An
assessment of these wells is obviously limited. It should be noted that wells
SP-31, SP-1 and M-12s are currently monitored on a quarterly basis as part
of the assessment program.
63

-------
POND1
a/
CT\
4^
INLET
TEXACO PROPERTY
BOUNDARY
EXCESS SERVICE WATER
EFFLUENT PONDS
POND
/y POND
LEGEND
OUTLET
SETTLINO m
PONOS	^
M-6
El Nested Monitoring Well
n Uppermost Aquifer
Monitoring Well In
Uppermost Aquifer
FIGURE 19
Location of Excess Service Water Effluent Ponds Monitoring Wells
Texaco Refinery, Casper, Wyoming
Source : Modified, from Western Woter Consultants, 1987.

-------
eval-B
Monitoring Well Svstcm Design/Placement/Construction The ground-water
monitoring system was originally implemented to define the geology and
hydrogeologv in the North Area. Subsequently, the system was and is used
to define water quality under the assessment program and provide hydraulic
properties of the two aquifers and the confining unit.
Horizontal locations of these wells were based on regional and local ground-
water flow. The vertical locations of the screened intervals were designed
to provide ground-water samples from the upper and alluvial aquifers, in
addition to the unnamed middle member.
Based on the refinery waste constituents (Table 5), the monitoring system
should be capable of monitoring the water table during high and low water
level stages for light phase immisciblcs. The system should also be capable
of detecting dense phase immiscible components. Table 6 presents historic
high and low water elevations of all monitoring wells located in the North
Area between 1982 and 1987, and compares these with the screened
elevations. Table 6 also presents the adequacy of the intervals to detect
light phase immiscibles during both historic high and low water level
periods. Finally, the table addresses the adequacy of the monitoring system
to detect any dense phase immisciblcs. The criterion used by the Task Force
to verify the latter was that a well had a portion of the screened interval
located at the aquifer/unnamed middle member (aquitard) interface.
As indicated in Table 6, only seven wells are capable of detecting light
phase layers for all previous water level elevations. Based on potentiomctric
maps and water quality data, these wells arc located hydraulically up or
cross gradient, or so far away from the HWMUs so that dilution or other
natural factors affect the ability to obtain a sample representative of any
potential floating layers being transported from the units. Wells M-6b and
M-23 are located near the Excess Service Water Effluent Pond No. 1 and
approximately 1200 feet northwest of the CEP, respectively (Figures 19 and
10). Wells M-17 and M-37 are both located at least 400 feet cast of the
North Land Farm, and wells SP-29, SP-30 and SP-31 arc located in the
alluvial aquifer near the North Platte River (Figure 10).
Tabic 6 also indicates that 35 wells arc unable to detect a light phase
immiscible during any past water level. However, many of these are
designed and constructed to monitor other sections of the uppermost
aquifer, in addition to other stratigraphic units. Examples of the latter
include the m and d- series wells, and the wells screened in the unnamed
middle member.
Finally, Table 6 presents the wells whose screens are capable of detecting
potential dense phase immiscibles. Discounting most of the SP- series wells
located at the alluvial aquifer/unnamed middle member contact, 12 wells
are screened such that dense phase immiscibles could be detected.
The horizontal locations of all monitoring wells in the North Area are
shown on Figures 10 and 19. Based on the local geology and hydrogeology,
in addition to past analytical results, complete characterization of the
uppermost aquifer is not possible. Two areas of concern were noted by the
65

-------
tab-e
slh
Table 5
Select Physical Constants of Known Groundwater Contaminants
CHEMICAL
DENSITY (g/m!
Anthracene
1.25
Benzene
0.8787
Benzenethiol
1.0766
Chlorodane
1.59-1.63
Chrysene
1.274
Cresols
1.030-1.038
1-2 Dibromoethane
1.5389
2,4-Dimethylphenol
1.0276
2,4-Dini trophenol
1.683
Ethyl benzene
0.8672
Fluoranthene
1.252
F1uorene
1.203
Heptachlor
1.5050
Methyl Ethyl Ketone
1.3814
(2-butanone)

1-Methyl-Napthalene
1.025
2-Methyl-Napthalene
1.0058
2-Methyl phenol
1.047
4-Methylphenol
1.5395
Naphthalene
1.145
4-Nitrophenol
1.495
Phenanthrene
1.179
Phenol
1.0722
Pyrene
1.271
Toluene
0.8669
Xylene
0.8968
WATER SOLUBILITY (g/m3)
in HoO
in H2O
h2o
0.075
1780
Insoluble
Insoluble
.002
Soluble in about 50 parts
4.310
SIightly soluble
Very sparingly soluble in H?0
1780
0.260
1.98
Insoluble
61.4
27
Soluble in about 40 parts
100 ml HoO dissolves about
2.5 g at 50F
34.4
Moderately soluble in H?0
1.18
93.0
0.148
515
185
References
CRC Handbook of Chemistry and Physics, The Chemical Rubber Co., 1969.
Dangerous Properties of Industrial Materials, Van Nostrand
Reinhold Co., 1984.
The Merck Index, Merck & Co., Inc., 1976.
Soil Gas Sensing for Detecting and Mapping of Volatile Organics, National
Water Well Association, 1987.
66

-------
tab-a
slh	Tabic 6
Historic High, Low and Screened Interval Elevations
(North Area)
(Elevations in feet above mean sea level)
WELL I.D.
HISTORIC HIGH
ELEVATION
HISTORIC LOU
ELEVATION
SCREENED INTERVAL
ELEVATIONS
ADEQUATE TO DETECT
LIGHT IHHISCIBLE
COMPONENTS AT
HISTORIC HIGH
ELEVATIONS?
ADEQUATE TO DETECT
LIGHT IHHISCIBLE
COMPONENTS AT
HISTORIC LOW
ELEVATIONS?
ADEQUATE TO
DETECT DENSE
PHASE IHHISCIBLE
COMPONENTS?
H-1
5210.9
5208.5
5183 - 5188
No
No
No
H-2
5163.8
5180.0
5175 - 5180
No
Yes
No
H-J
5187.6
5185.3
5186 - 5191
Yes
No
No
H-4
5187.9
5186.2
5177 - 5182
No
No
No
H-6a
5154.1
5153.0
5149 - 5152
No
No
No
M-6b
5158.9
5156.2
5154 - 5159
Yes
Yes
No
H-7s
5121.9
5120.6
5115.5-5118.5
No
No
No
N-7d
5121.9
5120.0
5090 - 5093
.No
No
No
H-Bs
5124.9
5121.8
5121 - 5124
No.
Yes
No
H-fisa
5124.9
5119.4
5115 - 5118
No
NO
NO
M-Bd
5120.8
5119.1
5070 - 5073
No
NO
No
M-9s
5127.3
5123.3
5123 - 5126
No
Yes
No
H-9d
5122.9
5118.6
5107 - 5110
NO
NO
NO
M- 10s
5122.3
5118.1
5121.5-5124.5
Yes
No
No
M-IOra
5121.7
5117.2
5112 - 5115
No
No
Yes
M-IOd
5120.7
5116.3
5096 - 5099
No
No
NO
H-lls
5128.5
5121.1
5120 - 5123
No
Yes
No
H-11d
5122.8
5117.6
5094 - 5097
No
NO
No
M-12s
5080.3
5076.9
*1



M-13
5121.8
5119.1
5113.25-5119.25
No
Yes
No
H-Hs
5119.3
5117.4
5107 - 5113
No
No
No
H-Ud
5119.6
5117.3
5084.7-5090.7
No
No
Yes
M-15
5118.4
5117.0
5104.5-5110.5
No
No
No
H-16
5118.9
5116.9
5107.5-5113.5
No
No
No
M-17
5114.7
5112.0
5105 - 5115
Yes
Yes
No
H-18d
5108.6
5105.4
5075.5-5081.5
No
No
Yes
H-19
5116.1
5114.2
5108 - 5114
No
NO
No
M-20
5121.7
5120.6
*1


No
H-21
5121.1
5119.5
5090.5-5096.5
No
Ho
No
*1 No log available.

-------
tab-a
slh
HISTORIC HIGH	HISTORIC LOU	SCREENED INTERVAL
WELL I.D.	ELEVATION	ELEVATION	ELEVATIONS
H-22	5121.1	5120.1	*1
H-23	5117.6	5116.8	5112.7-5117.7
M-24	5120.7	5119.4	5096.5-5102.5
M-25	5114.5	5113.5	5093.5-5099.5
H-26	5098.9	5095.3	5086.5-5094.5
H-27	5110.9	5108.5	5083.2-5089.2
M-29	5119.7	5118.0	5109 - 5119
M-30	5095.8	5093.3	5085.4-5091.5
M-3U	5120.4	5118.4	5106.5-5112.5
H-31m	5119.5	5118.1	5091.7-5097.7
H-32	5094.7	5092.2	5082 - 5092
M-33	5089.1	5085.5	5077 - 5087
H-34	5120.2	5118.5	5100.4-5110.4
H-35	5115.3	5112.2	5099.9-5109.9
M-36	5120.8	5118.5	5098.6-5118.6
M-37	5111.4	5109.2	5089.1-5114.5
M-49A	5126.1	5121.2	5119 - 5122
H-50As	No data	No data	5124 - 5127
H-50Ad	5122.3	5114.0	5121 - 5124
M-51As	5115.7	5114.0	5111 - 5114
M-51Am	5117.0	5115.2	5081 - 5084
H-51Ad	5115.7	5113.8	5059 - 5062
SP-1	5112.2	5110.9	*1
SP-2	5098.8	5096.6	*1
SP-3	5105.9	5105.5	*1
SP-4	5103.5	5103.0	*1
SP-4a	5102.7	5102.7	*1
SP-5	5080.4	5076.6	5070.5-5074.2
SP-7	5080.4	5076.5	5071.0-5074.5
SP-8	5080.4	5076.4	5071.5-5075.1
SP-9	5080.3	5076.4	5073.5-5077.2
SP-10	5080.6	5076.7	5071.0-5074.5
SP-19	5077.4	5077.0	5071.0-5076.5
SP-23	5077.5	5075.4	5072.1-5075.4
SP-24	5084.2	5079.0	5076.4-5079.4
Tabic 6 (continued)
ADEQUATE TO DETECT
LIGHT IHHISCIBLE
COMPONENTS AT
HISTORIC HIGH
ELEVATIONS?
ADEQUATE TO DETECT
LIGHT IHHISCIBLE
COMPONENTS AT
HISTORIC LOW
ELEVATIONS?
ADEQUATE TO
DETECT DENSE
PHASE IHHISCIBLE
COMPONENTS?
Yes
No
No
NO
No
NO
No
No
No
No
No
No
No
NO
Yes
No
Yes
No
No
No
Yes
No
No
No
No
Yes
No
No
No
No
Yes
No
No
Yes
Yes
Yes
No
Yes
No
No
No
No
Yes
Yes
No
No
Yes
Yes
No
Yes
Yes
Yes
No
No
No
Yes
No
Yes
No
No
No
NO
No	No	Yes
No	No	Yes
No	No	Yes
No	Yes	Yes
No	No	Yes
No	No	Yes
No	Yes	Yes
No	Yes	Yes

-------
tuu- a
slh
HISTORIC HIGH	HISTORIC LOU	SCREENED INTERVAL
WELL I.D.	ELEVATION	ELEVATION	ELEVATIONS
SP-25	5080.1	Dry *1
SP-26	5080.3	5076.5 *1
SP-27	5080.3	Dry *1
SP-28	5080.1	5076.2 5071.5-5079.5
SP-29	$077.0	5075.3 5074.3-5077.8
SP-30	5077.5	5076.0 5070.6-5079.8
SP-31	5077.9	5076.4 5073.0-50B0.0
SP-32	5077.4	5075.8 *2

-------
eval-B
Task Force. The first area is located east of the CEP and North Land
Farm. As noted in Plate 1 Section A-A', a palco-channel (top of bedrock
depression) occurs cast of the HWMUs. In addition, the Teapot Sandstone
subcrops in or near this bedrock depression. Based on well logs, the Teapot
Sandstone has at best a single well located so as to monitor ground-water
quality of this unit. Because this unit is used as a water supply down-dip
(towards the northeast), the Task Force recommends both the installation of
additional wells to characterize water quality on Texaco property, and
sampling of wells down-dip to determine if contamination has migrated off-
site.
The second area of concern noted by the Task Force is the lack of
monitoring wells located south and southwest of the HWMUs. This area is
characterized by the shaley unnamed middle member. Previous technical
reports submitted by Texaco indicate that this unit acts as a ground water
barrier, and that flow is diverted on both sides of this unit (i.e. to the
southwest and southeast). However, it appears that locally this shaley unit
may be hydraulically connected with the surrounding units (i.e., the colian
and alluvial deposits). Evidence to substantiate this is based on the fact
that two wells (M-9d and M-lOd) have shown contamination in the past.
The Task Force recommends that additional wells be installed south and
southwest of the HWMUs in the unnamed middle member. The installation
of additional wells in this area would also provide data on the impact that
the SWMUs may have on ground water. In addition, it is evident based on
Figure 19 that an inadequate number of wells arc installed adjacent to the
Excess Service Water Effluent Ponds to evaluate potential release from this
SWMU. Based on-the geology and hydrogeology of the area and past
analytical data, the wells located along the western property boundary arc
adequately loeafed from a horizontal viewpoint.
Design and specifications of the wells located within the North Area are
presented in Table 7. Additional information related to the technical
adequacy of the construction of these wells arc presented in Tabic 8. In
assessing the technical merit of the monitoring system, only generalized
inadequacies will be mentioned. The reader is referred to Tables 7 and 8
for specific construction inadequacies of each monitoring well.
All wells were drilled by rotary or hollow stem auger methods. The Task
Force noted that two different types of drilling fluids were used during
construction of some of the wells. Table 9 lists the type of drilling fluid
and the associated wells. All other wells used air and/or water, or used a
hollow stem auger where no fluid is necessary.
70

-------
tab-b
slh
DATE	SURFACE	10TAI	CASING
UELl I.O. DRILLEO	ELEVATION	DEPTH	DIAMETER
(feet above	(feel below (Inches)
man lei leva!)	surface)
N* 1 11/24/61 5227	50'	4-
N-2 M/25/A1 5201'	32'	4-
M-S 12/2/81 5201'	15'	4-
H-ft 12/4/61 5201'	26'	4"
H-5 12/1/81 NA	100'
M-6a 12/4/81 5179'	40'	4"
H*68 12/11/01 5176'	35'	4-
N-7s 1/6/82 5U2'	26.5'	4"
M-7d 12/5/61 5142'	60'	4"
M-a 1/8/82 5138'	20'	4"
Table 7
Monitoring Well Specification!
(Morth Area)
CAS1MG TYPE
Sch 40 0V at
Sch 40 gv at
Sch 40 gv at
Sch 40 0v at
Sch 40 gv (
Sch 40 gv i
Sch 40 gv at
Sch 40 gv at
SCHEMED
UtERVAl
(feet tl
surface)
39-44'
10-15'
19-24'
27-30'
23.5-26.5'
SLOT OC
PERF. SIZE
(lnchs)
0. 10"
0.10-
O.IO-
ft-12 free aatd
1/4** pea grav
ft B-12 frac d.
1/4* pea grav
ft 6-12 frac sd.
1/4** pea grav
ft 8 12 frac id.
12-20 frac send
1/4 pea grav
ft 6-12 frac td.
12-20 frac land
Drill cuttings
SCREENEO UMll
EolI an Sand
EolIan Send
EolI an Sand
teapot Sand
Eol(an Sand
leopot Sand
UATER
BEARING UNIT
Uppermost aquifer
Uppermost aquifer
Uppermost aquifer
Uppermost aquifer
DRY, PLUGGED AWO ABANDONED
Uppermost aquifer
Eolion Sand
Teapot Sand
EolI an Sand
Teapot Sand
EolI an Sand
Teapot Sand
EolI an Sand
Teapot Sand
Uppermost aquifer
Uppernost aquifer
Uppernost aquifer
Sch 40 gv st
12-20 frac sand Eol Ian Sand	Uppermost aquifer

-------
ttb-b
 lh
f*bl 7 (contlntied)
VEIL I.O.
H-8sa
K-ftd
CME
DRILLED
1/10/42
1/1A/A2
SURFACE
ELEVATION
(feet above
neon aea level>
513?'
5140'
TOTAL
OEPTM
CASUG
DlAflEICI
(feet bo Iow (Inches)
urface)
40'
70'
CASING ITPE
Sch 40 gv it
Sch 40 gv it
SCftEEhEO
IWTEBVAL
(feci txIow
surface)
19-22'
67-70'
1/27/82
5H4'
Sch 40 gv it
16-21*
-9d
1/27/62
5144'
38'
Sch 40 gv it
1/11/82
5144'
Sch 40 gv it
19.5-22.5'
1/25/82
Sch 40 gv i
M-10d
1/25/82
5144'
Sch 40 gv at
M-11a
1/26/82
22'
Sch 40 gv st
H-11d
1/26/82
5141'
50'
Sch 40 gv at
M-12*
K13
4/15/82
6/25/82
1
51*1'
9.5'
4>7'
5-9'
21.75-27.75'
SLOT 00
pEir. $iit
(Inchee)
SAKO PACK
SCREENED UWtT
VTA t Eff
BEARING UN1I
0.020	8- 12 frac card Cot (an Sand	Uppermost aquifer
0.200"	Drill cutting* Unnamed	Unnairied
Middle Hbr.	Hiddte Hbr.
0.020"	12-20 frac aand iollan Sand	Uppermost aquifer
leapot Sand
0.020"	12-20 frac aand Unnamed	Umamed
Middle Hbr.	Hiddle fffcr.
0.020"	12-20 (rac land iollan Sand	Uppermost aquifer
Teapot Sand
0.020"	Drill cutting* Teapot Sand	Uppermost aquifer
UYi&ned H. Hbr.
0.020"	Orlll cuttings Unnamed	Urramed
Middle Hbr.	Hiddle Hbr.
0.020"	Orlll cuttings FollanSand	Uppermost aquifer
Teapot S^nd
0.020"	Drill cuttings Unnamed	Unnamed
Middle Hbr,	Middle Hbr.
At luvlun	AI luvlus
0.020"	8-16 i 12-20	Eollan Sand	Uppermost aquifer
E oil on Send

-------
teb-b
slh
Table 7 (coot I rued)
WELL 1.0.
M-Hs
DATE
OfllllED
7/10/62
SURFACE
ELEVATION
(feet above
netn lei level)
5135'
TOTAL
OEPTH
(feat below
uriici)
26'
CASING
01 AmCICR
(Inches)
CASIUG TYPE
SCtECNfO
INTERVAL
(lot below
lur(tca)
nor OA
PERf . SUE
(tnchi)
0.020"
12-20
Si Iica Sand
SCREEUE0 UWIT
WATER
BEARING UNIT
EolIan Sand	Uppermost aquifer
H-Ud
7/9/62
5135'
70'
PVC
44.3-50.3'
12-20
SI Iice Sand
Unnamed
Hlddle Hbr
Unnamed
Middle Hbr.
M-15
7/11/82
5117*
32.5'
26.5-32.5'
0.020"
12*20
Si Ifca Sard
Basal Clay
Uppermost aquifer
H-14
M-17
M* 16d
7/10/62
7/13/62
7/12/62
5135'
51311
5129'
26'
27.6'
53.5'
21.5-27.5*
16-26'
47.5-53.5'
0.020"
0.020-
0.020"
1220
SI Iica Sand
1220
Slllea Sand
12 20
SI Iica Sand
EolIan Sand
Basal Clay
EolIan Sand
Basal Clay
Unnamed
Hiddle Hbr.
Uppermost aquifer
Uppermost aquifer
Umomed
Hlddle Hbr.
H-19
7/11/62
14-20'
12-20
S iIica Sand
Eol Ian Sand	Uppermost oqulfer
H-20
H-21
6/17/62
7/8/62
NA
5137'
32'
52'
Sch 40 at
PVC
22.5-25.5'
40.5-46.5'
0.020-
0.020"
12-20 free sand
12-20
SI Iica Sand
Colian Sard
Col Ian Sand
Uppermost aquifer
Uppermost aquifer
H-22
H-23
6/16/62
6/19/82
<4.6'
27.5'
Sch 40 0V st
PVC
24-30'
12.3-16.3'
0.016"
0.020"
12-20 frac aand
12-20 frac sand
EolIan Sand
EolIan Sand
Uppermost aquifer
Uppermost Aquifer

-------
tftb-b
slh
Ttblt 7 (continued)
WELL I.O.
DATE
DRILLEO
SU*fACE
ILEVATIOM
(feet above
vwn lea level)
TOTAL
DEPTH
(feet below
aurface)
CASIUC
OlAMCTCt
(Inches)
CASIUC TTPE
SCRCCMCO
INTERVAL
((tit below
aurface)
SLOT OA
peiF. SIZE
(Inchtl)
SCREENED UWIT
WATER
BEAHIMG UUIT
H-24
7/7/52
5144'
4ft'
41.5-47.5
12-20	Sartfy alltatone Uppermost aquifer
S11 ice Sand
M-2S
7/7/82
5124'
36'
2"
24.5-30.5'
0.020-
12-20 1 fl-16	latal alltatone Upper,-noit aquifer
Sll Ico Sand
H-26
6/20/62
5101'
16'
2"
6.5*12.5
0.020-
12-20
Silica Sand
EolI an Send
U(f>ermott aquifer
M-27
6/20/62
5116'
0.020"
12-20
Silica Sand
Unnamed
MldJl Mbr.
Umamed
Hiiidle Mbr.
M2fi	7/13/62	HA	26'	HOiE PLUGGED AW0 ABANDONED
M-29	7/13/62	5135'	27.5'	2"	PVC	16-26'	0.020M	12-20	Eollan Sand	Uppcrmoil equtfer
SUIca Sand	Batal Clay
H-30	6/20/62	5099'	16'	2"	PVC	7.5-13.6'	0.020"	12-20	Col Ian Sand	uppermost apjifar
Silica Send
M-3U	6/29/62	5140'	33.5'	2"	PVC	27.1-33.1'	0.020-	Clean drill	Eollan Sand	Uppermoit aquifer
cutiIng*
M-J1	6/30/82	5139.5'	59'	2	PVC	*1.1-47.S'	0.020"	Clean drill	Soisl CUy	tlppermoit qulfr
cut 11 r*9
H-32	7/15/82	5095'	14'	2"	PVC	3-13'	0.020"	12-20	Eotlan Sand, Basal Uppermost aquifer
Silica Sand	Clay, Urm. H. Hbr.

-------
lab-b
slh
Table 7 (continued)
WELL I.O.
M-33
OAlt
DfilllEO
7/15/02
SURFACE
ELEVATION
(feel abovt
Man hi 1 evil)
5099'
TOTAL
DEPTH
(feet below
urfici)
CASING
DIAHEICB
(Inches)
CASIUC TTPE
SC8EEUE0
I MItBVAl
(fet below
lurfict)
12-22'
SLOT 0*
per* . size
( Inches)
fi-16
S111c* Sand
SCREENED UWIT
Basal Clay
Unnamed M. Hbr.
WATER
BEARING UMIT
Uppermost aquifer
M-34
7/15/62
51(0'
39.5'
2"
*9.6-39.5'
12-20
Silica Sand
Basal Clay
Uppermost aquifer
M-35
7/15/62
5126'
29.5'.
IB.1-26.1
6-16 ft 12-20
Silica Sand
Basal Clay	Uppermost aquifer
M-36
M-37
H-49A
H-50AC
H-SOAd
3/29/64
9/20/64
1/24/82
1/26/62
1/12/62
5136.6'
5119.9'
5141*
5142'
W.A.
40'
31.5'
25'
22'
56'
Sch 40 PVC
Sch 40 PVC
1120
Sch 40 gv at
Sch 40 gv st
Sch 40 gv st
20-40'
5.4-30.6'
19-22'
16-21''
52*55'
0.020-
0.025-
0.020-
0.020-
0.020-
OrHI cuttings MA
6-16 frac sand Sand ft gravel
Drill cuttings EollanSand
Yea	EotI an Sand
12-20 frac sand Unnamed
Middle Hbr.
Uppermost aquifer
Uppermost aquifer
Uppermost aquifer
Uppermost aquifer
Unnamed
Middle Hbr.
M-51AI
1/10/62
5124'
15'
Sch 40 gv st
12-20 frac sand Backfilled
EolI an Sand
Uppermost aquifer
H-SlAa
1/20/62
5124'
Sch 40 gv at
0.020"
Drill cuttings Unnamed
Middle Mbr.
Unnamed
Kiddle Mbr.
A-51Ad
1/22/62
Sch 40 gv st
0.020-
Drlll cuttings Unnamed
Middle Mbr.
Unnamed
Middle Mbr.

-------
tb-b
ftlh
DATE	SURFACE
UELL l.D. DRILLED	ElEVATIOM
(feet ibovi
mean set I eve
SP-1 3/26/62	*1
SP-2 4/15/82	M
G\
SP-3	4/15/02
SP-4 4/15/62	*1
SP-4A
SP-5 6/22/62	5079*
SP-7 6/22/62	5081'
SP*8 6/22/62	5082'
SP-9 6/22/62	5082'
SP-10 6/22/62	5081'
SP-1P 6/26/62	5081'
Table 7
TOTAL	CASING
DEPTH	DIAMETEI	CASING TYPE
(feel below (Irxhci)
> lur(ica)
9'
6'
5'
11'
9'	2m	Sch 40 gv (
M.2'	2"	Sch 40 gv it
11.2'	2"	Sch 40 gv at
9'	2-	Sch 40 gv it
14'	2"	Sch 40 gv it
8.5*	2"	Sch 40 gv it
coot tnued)
SCKIhEO
INTERVAL
(feel below
tor face)
SLOT OS
PCI'. SIZE
(Inches)
5-6.5'
4-7.5*
1-4.5'
7-10.5'
SCREENED UNIT
UAIER
BEARING umit
EolI an Sand
Uppermost aquifer
Unnamed
Middle Hbr.
Unnamed
Middle Hbr.
EolI en Sand
Uppermost aquifer
Unnamed
Middle Mbr.
Unnamed
Middle Mbr.
4.6-6.5'	0.020"	12*20	Allisvlu*	AIIuvIltb
Si I lea Sand
6.5-10'	0.020"	12-20	Alluvlui	Alluvlun
Silica Sand
6.9-10.5'	0.020	12-20	Altisvlm	Alluvlun
Silica Sand
4.6-6.5'	0.020"	12-20	Allt/vlim	Alluvluo
Si I lea Sand
6.5-10'	0.020**	12-20	Alluvia	Atlirvlm
Silica Sand
4.5-7.6'	0.020-	Clean drill	Alluvlus	AtliAvlin
cuttings

-------
tab*b
 lh
SP-20
SP-21
SP-22
SP-2J
DATE
DRILLED
2
2
2
6/29/A2
SURFACE
ElEVATIOH
(feet above
oean tea level>
TOTAL
DEPTH
(Ictt below
aurface)
CASING
01AMEIER
(inches)
5060'
9.3'
IP-24
7/15/62
13'
SP-25
SP-26
SP-27
SP-26
2
2
2
3/29/84
5081.5'
SP-29
9/19/84
5079.8'
5.7'
SP-30
9/19/84
5083.3'
12.9'
Table 7 (contlnjcd)
SCIEEME0
CASING TYPE	IMIESVAI
(feat below
lurlice)
SLOT OR
PES'. S12E	SM0 PACC
(Inchci>
WATER
SCBEEMEO UWIT	BEAR1UG UMIT
Sch 40 gv at	4.6-7.9'	0.020"
0v at	9.6-12.6'	0.020"
Clean drill	Al IlvIlti	Alluvlm
cuitlogs
8-16	At luvlin	Alluvlue
Silica Sand
PVC	2-10'	0.020"
Sch 40	2-5.5'	0.025"
PVC 1120
Sch 40	3.5-12.7'	0.025"
PVC 1120
Clean drill	Sand and gravel	AlluvliA
cut tlogs
B-16 free land Soft * clay 	Alluvlui
sand
Clean sand	Sand and gravel Alluvlin
and gravel

-------
tab*b
 Ih
Table 7 (continued)
WELL I.O.
OATE
DRILLED
SU8/ACE
ELEVA1ION
(feet above
mean ie level)
TOTAL
DEPTH
(feet be Iow
urface)
CASING
DIAMETER
(Inches)
CASING TYPE
screened
INTERVAL
(feat below
surface)
SLOT OA
PEBF. SIZE
(Inches)
SCREENED UNIT
UAfER
GEAR IMG UNIT
SP-J1
CD
9/19/64
5083.0'
10.0'
Sch 40
PVC 1120
3-10'
0.025"
Natural sand
and gravel
Send and
gravel
SP-32
9/21/M
Sch 40
PVC 1120
0.025-
Natural a and
and gravel
Sand arvJ
gravel
1 Ho log; partial Information obtained from well Inventory sheets.
"2 Information unavailable.
NA Information not specified on completion details.

-------
tab-c
Slh
Tabic 8
Technical Adequacy of Monitoring Wells (North Area)
(Depth and Thicknesses in Feet)
Thickness



Bentonite Bottom
of F i Iter. Pack

Th i ckness of Drill
Cement


Uater
Total Depth
Seal Inplaced
and/or Drill Cuttings
Thickness of
Cuttings Above
Annular
Surface
Well l.D.
Bearing Unit
of Borehole
in Borehole?
Above uell Screen
Bentonite Seal
Bentonite Seal
Seal?
Seal?
M-1
upper aquifer
50
Yes
0
*1
-25
No
Yes
H-2
upper aqui fer
32
Yes
0
*1
-10
No
Yes
H-3
upper aquifer
15
No
0
*1
- 4
No
Yes
M-4
upper aquifer
24
No
0
*1
-12
No
Yes
H-6a
upper aquifer
30
NO
12
1
- 5
No
Yes
H-6b
upper aquifer
24
No
3
*1
- 5
No
Yes
M-7s
upper aquifer
26.5
No
a.5
*1
- 6
No
Yes
M-7d
upper aqui fer
52
No
1

-37
No
Yes
H-Bs
upper aquifer
17
NO
2

- 5
No
Yes
H-8sa
upper aquifer
22
No
7

6
No
Yes
M-8d
unnamed Hidl. Hbr.
70
No
10
*1
-47
No
Yes
M-9s
upper aquifer
21
No
3
*1
- 7
No
Yes
M-9d
unnamed Hidl. Hbr.
37
NO
2
*1
-17
No
Yes
H- 10s
upper aquifer
22.5
No
2.5
1
- 9
No
Yes
M-IOm
upper aquifer
32
No
1
*1
-22
No
Yes
H-10d
unnamed Hidl. Hbr.
43
NO
2
*1
-32
NO
Yes
M-11s
upper aquifer
21
No
-15
0
N/A
No
Yes
M-11d
unnamed Hidl. Hbr.
47
NO
4
*1
-30
NO
Yes
H-12s
alluv. aquifer
*2






M-13
upper aquifer
67
Ho
4.75
U.75
0
Yes
Yes
*1 Thickness unknown, but appears adequate.
N/A Not applicable.
*2 Well log unavailable; information taken from well inventory data sheets.

-------
tab-c
slh
Table 8 (continued)
Thickness



Bentonite Bottom
of F iIter Pack

Thickness of Drill
Cement


Uater
Total Depth
Seal Implaced
and/or Drill Cuttings
Thickness of
Cuttings Above
Annular
Surface
uell 1.0.
Bearing Unit
of Borehole
in Borehole?
Above Wet I Screen
Bentonite Seal
Bcntoni te Seal
Seal?
Seal?
M-Hs
upper aquifer
28
No
16.5
4
0
Yes
Yes
M-Kd
upper/un. Midi. Hbr
70
No
19.7
22
1
No
Yes
H-15
upper aquifer
32.5
No
10.5
14
0
Yes
Yes
H-16
upper aquifer
28
No
15.5
4
0
Yes
Yes
M-17
upper aquifer
27.8
No
8
5
0
Yes
Yes
H-18d
upper aquifer
53.5
No
19.5
15
11
No
Yes
M-19
upper aquifer
20
No
8
4
0
Yes
Yes
M-20
upper aquifer
32
No
15.5
4.5
0
Yes
Yes
H-21
upper aquifer
52
No
24.5
11.5
0
Yes
Yes
H-22
upper aquifer
44.8
No
17.5
5
0
Yes
Yes
H-23
upper aquifer
27.5
No
6.3
4
0
Yes
Yes
N-24
upper aquifer
48
No
35
5.5
0
Yes
Yes
M-25
upper aquifer
36
NO
20.5
3
0
Yes
Yes
M-26
upper aquifer
16
Yes
2.5
2
0
Yes
Yes
H-27
unnamed Midi. Hbr.
33
No
20.8
4
0
Yes
Yes
H-29
upper aquifer
27.5
No
8
5
0
Yes
Yes
H-30
upper aquifer
16
Yes
3.5
2
0
Yes
Yes
H-31s
upper aquifer
33.5
No
23.1
3
0
Yes
Yes
H-31m
upper aquifer
59
No
36.8
2.6
0
Yes
Yes
H-32
upper aquifer
14
NO
0.5

N/A
Yes
Yes
H-33
upper/unm. Midi. Mbr. 23
No
4

0
Yes
Yes
H-34
upper aquifer
39.5
No
14.5
7
5
No
Yes
H-35
upper aquifer
29.5
No
10.8
4
0
Yes
Yes
H-36
upper aquifer
40
No
-17
*1
*3
No
No
H-37
upper aquifer
31.5
No
3.4
0
*3
Yes
Yes
N-49A
upper aqui fer
25
No
-16
0
*3
Yes
Yes
*3 Bentonite seal to surface.

-------
tab-c
slh
Well I.D.
Uater
Bearing Unit
Total Depth
of Borehole
Bentonite Bottom
Seal Implaced
in Borehole?
H-50As
H-50Ad
M-51AS
H-51Am
M-51Ad
SP-1
SP-2
SP-3
SP-4
SP-4a
SP-5
SP-7
SP-fl
SP-9
SP-10
SP-19
SP-23
SP-24
SP-25
SP-26
SP-27
SP-28
SP-29
SP-30
SP-31
SP-32
upper aquifer
unnamed Midi. Mbr.
upper aquifer
unnamed Midi. Hbr.
unnamed Midi. Hbr.
upper aquifer
unnamed Midi. Hbr.
upper aquifer
unnamed Midi. Hbr.
*4
alluv. aquifer
alluv. aquifer
alluv. aquifer
alluv. aquifer
alluv. aquifer
alluv. aquifer
alluv. aquifer
alluv. aquifer
*4
*4
alluv. aquifer
alluv. aquifer
alluv. aquifer
alluv. aquifer
alluv. aquifer
22
56
15
45
70
9
8
5
11
9
13.2
11.2
9
14
8.5
9.3
13
10
5.7
12.9
10
10.5
Yes
No
No
No
No
*2
*2
2
*2
No
No
NO
No
Yes
No
No
No
No
No
No
No
No
4 Well log and well inventory data sheets unavailable.
Table 8 (cont inued)
Thickness
of Filter Pack
and/or Drill Cuttings
Above Wei I Screen
Thickness of
Bentoni te Seat
-15
0
-5
3
1
0
1
*1
7
10
6.83
4.92
2.33
2.5
4.5
4.6
6.6
1
2
3
2.5
2
0
0
3
3
0
0.5
1
0.4
Thickness of Drill Cement
Cuttings Above	Annular Surface
Bentonite Seal	Seal?	Seal?
* 3
-	2
-	2
-27
-47
Yes
No
No
No
No
Yes
Yes
Yes
Yes
Yes
1
1
1
0
2
N/A
N/A
*3
No
NO
No
No
No
No
No
No
No
NO
No
No
No
No
No
No
N/A
N/A
N/A
N/A
N/A
NO
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes

-------
eval-B
Table 9
Drilling Fluid Utilized (North Area Wells)
Mvdro-gcl
Bnroid foam
M-1
M-2
M-3
M-4
M-5
M-7s
M-7d
M-6a
M-6b
M-7s
According to the TEGD, Texaco should provide chemical data regarding any
potential impacts on water quality the drilling fluid may have (EPA, 1986a).
According to Texaco, most of the wells in the system are designed and
constructed in the colian sands and the Teapot Sandstone (upper aquifer).
It should be noted that contrary to the various technical reports, the Teapot
Sandstone is not being monitored directly except for possibly in one well
Completion details show that many of the wells were drilled several feet
deeper than the bottom of the screen was set (Appendix B). This interval
was filled with drill cuttings and/or 12-20 frac sand, providing a potential
pathway for downward migration of contaminants. Very few of these wells
used a bentonite or equivalent bottom seal as depicted in Table 8. The
TEGD recommends a bottom seal for the same reason as noted above (EPA,
In virtually every well, the filter pack (consisting of drill cuttings and/or
12-20 frac sand) extended well above the well screen. As presented in Tabic
8, this interval ranged upwards to 36.8 feet. In order to ensure discrete
sample horizons, the filter pack should extend no more than two feet above
the well screen (EPA, 1986a). Completion details in some cases do not
specify the thickness of the bentonite annular seal (Appendix B). From a
qualitative standpoint, however, it appears that the thickness is adequate in
most cases. Several of the wells, most notably the SP- series, do not utilize a
bentonite annular seal. Most of these have a cement surface seal, however.
The Task Force noted that two wells, SP-19 and SP-23, did not use either a
(annular) bentonite or a cement (surface) seal.
Table 8 also indicates the thickness of drill cuttings above the bentonite seal
and below the cement surface seal. The TEGD recommends this interval be
filled with a cement-bentonite grout (EPA, 1986a). Finally, Table 8
indicates which wells used a cement based annular seal and a surface seal in
their construction, as depicted from the completion details.
Completion details specify that all monitoring wells were constructed of
either galvanized steel or PVC (Appendix B). According to the details, at
least two wells were constructed using dissimilar metals. Wells M-20 and M-
22 were constructed using a stainless steel screen and a galvanized steel
casing. Additional wells may have been constructed using stainless steel
(M-35).
1986a).
82

-------
eval-B
screens, but were not indicated in the well completion details. The TEGD
(EPA, 1986a) recommends avoiding the use of dissimilar metals in the
saturated zone unless a dielectric coupling is placed between the two metals.
Potential problems may exist when PVC is used in contact with aqueous
organic mixtures. These organics may encourage leaching from or
adsorption to the PVC polymer matrix. There has been recent concern over
the potential of vinyl chloride monomer to lcach from PVC casing, which in
some cases may cause organic analytical interferences in situations where
prolonged exposure to aqueous organic mixtures may occur (Barcelona and
others, 1983). In certain situations under high organic concentrations, PVC
may also adsorb organic constituents (Barcelona and others, 1983).
Furthermore, PVC .in contact with organics, particularly benzene, is not
recommended because of problems with long term structural integrity of the
well. In the future Texaco should review all available data/information on
casing materials carefully and make a selection accordingly before installing
new wells. This would be important at wells which exhibit significant
organic accumulations, especially since long term monitoring is probable.
In addition, the type, method and duration of well development have not
been specified. Turbidity measurements during the Task Force evaluation
indicate generally high values. Most wells exceeded the recommended limit
of 5 N.T.U. (EPA, 1986a). Completion details often did not specify if a
protective casing with a locking device was cmplaccd over the wells. The
purpose of this is to prevent tampering with the well or entrance of foreign
material (EPA, 1986a). Finally, decontamination of equipment and well
casing were not specified.
Past Analytical Performance A ground-water pollution abatement plan was
requested by EPA in November 1982, and the following month, the plan was
implemented. As part of the plan, Texaco began treatment of the CEP
water by mechanical aeration in December 1982 (WWC, 1984a). In
November 1983, the treated water from the CEP was discharged to the
Excess Service Water Effluent Ponds. Texaco stated that even though the
resulting sludge contained up to 2.4 percent lead, EP toxicity tests indicated
that the sludge was non-hazardous (WWC, 1984a). The sludge was removed
from the CEP in 1986 and disposed of in the North Land Farm. As
previously mentioned, approximately half of the monitoring wells located in
the North Area are sampled quarterly as part of Texaco's assessment
program. The purpose is to evaluate the rate, extent and concentration of
contamination emanating from the CEP. The remainder of the wells arc
sampled semi-annually or annually. The specific well and the sampling
frequency are presented in Table 10.
The parameters Texaco monitors pursuant to 40 CFR 265.93(d)(4)(ii) include:
specific conductance, pH, TOC, total ammonia, total chloride, phenols,
sulfide, total sodium, cyanide, nitrate, oil and grease, total sulfate, total
arsenic, total barium, total cadmium, total chromium, total lead, total
mercury, total selenium and total silver. Analytical results for the above
parameters have been provided to the Task Force from March 1982 through
December 1987 (WWC, 1984a, 1985, 1987a and 1988). Additional analyses
were done between March 1982 and December 1984 on the following
83

-------
Table 10 Monitoring Frequency of Wells on North Property for 1987
Quarterly
Serrii -Annual ly
Annually
Uppermost Aquifer
M - 7 s
M-8sa
M-9s
H-lOs
M-lOm
M-lls
M-13
M-Ks
M-16
H-17
M-19
M-26
M-30
M-32
M-33
M-36
M-37
M-49A
M-51AS
5P-1
SP-3
M-l
M-2
H-3
M-4
M-6b
H-7d
M-15
M-20
M-21
K-22
M-23
M-24
M-25
M-29
H-3 Is
M-31n
M-34
H-35
Unnamed Middle Member
M-9d
M-lOd
Alluvial Aquifer
M- 12s
SP-7
SP-23
SP-28
SP-29
SP-30
SP-31
SP-32
M-8d
M-l Id
K-I4d
M-lfid
H-27
M-50Ad
M-51Am
M-SlAd
SP-2
SP-4A
SP-5
SP-9
SP-8
SP-1G
SP-24
SP-26
Surface Water
North Platte Ri'/er
Recharge Pond
ESW-la
ESW-2a
E5W-5a
Source: WWC, 1988.
84

-------
eval-B
parameters: DOC, TOX, alkalinity, aluminum, dissolved ammonia, dissolved
arsenic, total barium, beryllium, boron, dissolved cadmium, calcium,
dissolved chloride, dissolved chromium, cobalt, copper, coliform bacteria,
fluoride, the herbicides 2,4-D and 2,4,5-TP Silvcx, iron, dissolved lead,
lithium, magnesium, manganese, dissolved mercury, nickel, nitrite, the
pesticides endrin, lindane, mcthoxychlor and toxaphene, potassium, gross
alpha, gross beta, Ra-226, Ra 228, Sr-90, uranium, dissolved selenium,
dissolved silver, dissolved sodium, dissolved sulfate, total dissolved solids,
vanadium and zinc.
In addition to the above "regular" analyses, four separate sampling events
were held in the past. In.March and September of 1984, Texaco monitored
for the organic priority pollutants, and in June of 1986 for the modified
Skinner list (TriHydro, 1987a). The Task Force evaluation was the fourth
event. Twenty-three monitoring wells, two seeps and the alluvial pond were
sampled during the first three events. The sampling locations and the
results of the organic analyses are presented in Figure 10 and Table 11,
respectively. The inorganic results arc too massive to be included in the
report or as an Appendix, but may be found in Volume III of the TriHydro
(1987a) report.
The results of past organic analyses indicate that contamination exists in
the North Area, primarily centered around the CEP and North Land Farm.
The volatile organics benzene and toluene were detected at concentrations
of less than 1000 ug/1 near the regulated units during past sampling events.
These two volatile's were not detected or were detected at extremely low
concentrations in wells located along the western property boundary and the
alluvial wells. Methyl ethyl ketone was also detected in wells M-32 and M-
36 (Figure 10).
The basc/neutral extractable organic bis(2-cthylhexyl)phthalate was detected
at most sampling locations, including several wells along the western
property boundary during the two events held in 1984. Because this
constituent was not detected during the Task Force evaluation, it seems
likely that these results may be due to laboratory or sampling related
contaminants. Texaco has not presented any supporting information
suggesting either of the above, however. Naphthalene was either not
detected or not analyzed in the past.
Minor concentrations of the pesticides chlordane and heptachlor were
detected in wells M-lOs, M-IOd and M-36 in 1986. Several acid extractable
organics also were found in the ground water in the past. Again, these are
generally confined to the wells surrounding the two regulated units. These
constituents include benzenethiol, cresols, 2,4-dimethylphcnol and phenol.
Of importance, cresol was detected in concentrations up to 289,000 ug/1. It
is interesting to note that this constituent may exist as a dense phase and
that the highest concentrations of cresol were detected in wells screened at
or near the upper aquifer/shale interface. From the above discussion and
Table 11, wells M-lOm and M-36 appear to be the most contaminated of all
wells located in the North Area. Samples analyzed for a complete set of
organic constituents in the wells near the Excess Service Water Effluent
Ponds have not been collected prior to the Task Force evaluation. Two
85

-------
Table 11 Organic Hazardous Constituents Detected In Ground Uater, Casper Plant Worth Property.'
Uell Hunter and
Date Samaled
Vol at I Ie Orqanlc
8enienc	Hethvl ethyl Icetone	Tol ixnt
Base/Hentral Entractable Oroanlcs
Pes 11cIdei
HapMhalene B I s( ?- e(hyl hmyl Ifhthalate	Eh 1 orrfar*	Hept ach I or
H-7g (Bacfcqround)
3-21-M
6 -&6
ND
HO
ND
HD
ND
ND
KD
HA
0.005
HA
HA
HA
NA
HA
H-IOs
7 -B6
0.012
WD
0.018
0.043/0.040J
HO
0.048
HO
K- 10m
3-21M
6 -&A
0.330
0.150
HD
ND
0.945
o.aoo
HO
HA
0.171
HA
HA
HA
HA
HA
H-10d
7 -A6
0.057
NO
0.012
HD
HO
NO
0.00026
H-12
9-21-M
6	-&4
7	-W
HO
HO
0.0032J
HO
HO
HD
HD
0.005
HD
HD
HA
Hp
0.064
HA
HD
HA
HA
HD
HA
HA
HO
M-30
3-21-W
ND
HO
HQ
HO
0.073
HA
HA
H-32
3-21-M
9-21-M
& -64
HD
HD
HO
HO
HD
0.011
HD
HO
HO
HD
HD
HA
0.10
0.10
HA
HA
HA
HA
HA
HA
HA
H-33
3-21-M
7 -84
HO
HO
HO
HD
HD
HD
HO
HD
0.132
HO
HA
HD
HA
HD
H35
7 -B6
HD
MD
HO
HD
HD
HD
HO
* All units are In mg/L.
HA  Not Analyied
HO  Hon Detectable
J - Indicates an estimated value where the measured value Is less than the method detection limit but greater than 0.
Source: TriHydro 1987a

-------
Table 12. Organic Hazardous Constituents Detected In Ground Voter, Casper Plant North Property (continued).
Vol at 11e Organic*
Well Nurfcer and
Pate Sampled
H3&
6	-86
7	-84
7 -84
(cfcjpl Icate)
tL<24
3-21-84
6 -86
8enrene	Methyl ethyl Itetone	Toluene
Bnse/Heutral Extractable Org/mlcs
P(stIcIdts
Hanhthalene Bls(2-ethylhexyl)rVitha(Bte	Chlordane	Heptachlor
0.230
0.310
0.270
0.13
0.16
0.520
0.670
0.570
HD
NO
0.330
0.410
0.340
0.10
0.410
HA
HO
NO
NO
MA
HA
NO
HO
HO
HO
HA
0.480
0.300
HO
NA
HA
HO
HD
HA
HA
7 -64
5P  1
3-21-84
0.074
0.058
ND
HD
0.034
HO
NO
NO
NO
0.071
HO
HA
HO
HA
spi3
3-21-84
9-21-84
6 -84
0.15
0.089
0.080
HO
NO
NO
0.22
0.12
0.099
NO
NO
HA
0.10
0.072
HA
NA
HA
NA
NA
HA
NA
5P-7
9-21-84
SP-9
9-21-84
5P-10
9-21-84
NO
NO
HO
HO
HD
NO
HO
HO
NO
HO
HO
NO
0.064
0.12
0.064
NA
MA
HA
NA
HA
HA
5P-23
9-21-84
SP-2B
9-21-84
HO
HO
ND
ND
HO
HD
HI?
HO
0.019
0.011
NA
HA
HA
HA
SP-29
9-21*84
HD
NO
HO
HO
0.030
HA
HA
* All unit* are In mg/L.
HA - Not Analyzed
ND  Hon Detectable
J  Indicates an estimated value where the measured value Is less than the method.detect(on limit but greater than 0,

-------
Table 11 Organic Hazardous Constituents Detected In Groundwater, Casper Plant Morth Property (coot Inucd).
Well Nurfcer and
Date Sampled
Vol at Ite Organlcs
SP-30
9-21*84
SP-31
9-21-ft*
SP-3?
9-21-84
Seep n
9-21-84
Seep *4
9-21-ft*
Alluvial Pond
9-21-84
Benierte	Hethvl ethyl ketone	Toh>cne
Onse/Hcutral futractahle Organic*
Pestle Ides
Naphthalene Bls(?-ethvlhexyl)rMhalte	Chlordnne	Heptachlor
ND
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
ND
NO
ND
ND
NO
NO
ND
ND
NO
ND
ND
NO
NO
0.010
0.056
0.028
0.024
0.052
O.OSO
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
CO
00
 All units are In mg/L.
NA - Not Analyzed
NO - Hon Oetectable
J  Indicates an estImated value where the measured value Is less than the method detection limit but greater than 0.

-------
Table ill Organic Hazardous Constituents Detected In Ground Uater, Casper Plant Worth Property.*
Uetl Hurber and
Date Sanpled
Acld-Extractabl e Organlcs
ientenethlol	Cresol s	2. 4 -0I me thy! phenol	2. 4-01 n 11 ropheool	4-Nl tror^tnol
Phervol
H-7s (Background)
3-21-84
6 -86
NO
HD
NO
NO
NO
ND
NO
NO
HO
NO
NO
HO
H-10$
7 -86
NO
0.048/0.060J	0.023/0.031J
O.OoOJ
0.0&&5/0.380 0.008/0.010J
H-10m
3-21-84
6 -86
1.0
0.12
289
32
29
5.0
NO
NO
NO
HO
130
a.t
H-10d
7 -84
NO
NO
1.1
NO
HO
NO
H- 12s
9-21-84
6	-86
7	-86
NO
NO
0.014 J
NO
NO
NO
NO
NO
NO
ND
NO
NO
NO
NO
ND
HO
NO
NO
oo mo
3-21-84
HO
HO
NO
NO
NO
HO
L22
3-21-84
9-21-84
6 -56
HO
NO
HD
NO
NO
HO
NO
NO
HO
NO
NO
NO
NO
WO
ND
ND
ND
HD
21
J-21-84
7 -86
HO
NO
NO
NO
NO
ND
HD
NO
HO
HD
HD
HD
H-3S
7 -R6
ND
0.0032J
HO
NO
HO
0.0038J
 All units are Inmg/L.
HA  Not Analyicd
NO  Non Detectable
J  Indicates nn estimated value where the mcosured value Is less then the method detection limit but greater than 0.

-------
Table 11 Organic Hazardous Constituents Detected In Ground Uater, Casper Plant Worth Property (continued).
Uel I Hurtxr and
Date Sampled
BenzenethIol
Ac IdExtractahle Orqanlcs
Crcsol s	Z.<-Dlnv:thylr^ennl	2 ,4-Dinl trophenol
4  Hi t ror^ienol
Phenol
H-3A
6	-66
7	-64
7 *B6
(dupl(cote)
H-49A
3-21-84
6	-B6
K-SUl
7	-66
SP-1
3-21-84
SP-3
3-21-64
9-21-84
6 -86
SP-7
9-21-84
5P-9
9-21-84
SP-10
9-21-84
SP-23
V-21-84
SP- 28
9-21-84
SP - 29
9-21-64
4.00
HD
HD
HO
MO
MO
0.012
0.11
WO
WD
HO
HO
MO
HO
HD
HO
170
U3
136
214
93
1.676J
0.033
30
HO
<9
HD
HD
HO
HO
HO
HO
25
H
13
19
12
2
0.33
7.9
6.5
15
HD
KD
HO
HO
HO
HO
HD
HD
HO
HO
NO
HD
HO
HD
HD
ND
HD
HO
HO
HO
HO
HO
HO
HO
HD
HO
HD
HD
HD
HD
HO
HO
HO
HO
HO
HD
HD
HD
64
64
62
64
49
HD
HD
0. 14
0.23
HO
HD
HO
HD
HO
HD
HD
 All units are In mg/L.
NA  Hot Analyzed
ND  Hon Oetectabl e
J - -Indicates an estimated value where the measured value Is .less than the method detection I Imlt but greater than 0.

-------
Table 11 Organic Hazardous Constituents Detected In Ground Uater, Casper Plant Worth Property (continued).
Uell Hurber and
Date Satrpled
Ac Id-Ektractable Organic*
Benieneth I ol	Cresol s	2 . t -0 I mo thy! phenol	?.t-D i nl t ronhenot	4  N11rophenol
Phenol
SP-30
9-21-M
NO
NO
NO
HO
NO
HO
SP-51
9-21-M
ND
NO
NO
ND
ND
ND
SP-33
9-21-M
NO
NO
ND
HO
NO
NO
Seep 
-------
eval-B
wells, M-l and M-6b, did not indicate organics present in the ground water
during the evaluation, however. In addition, inorganics above applicable
standards (to be discussed later) were not detected.
The extent of contamination has been defined by Texaco on a yearly basis
for only a select group of parameters. These include TOC, phenol, sulfide
and ammonia. Independent evaluations of these values and subsequent
concentration maps prepared by the Task Force agree favorably with
Texaco's presentations. Appendix F contains these concentration maps over
a five year period for the above mentioned parameters. Additional
contaminant concentrations have been posted for select organic species by
the Task Force for further comparison purposes (Figures 20, 21, and 22).
These parameters include benzene, phenol, toluene and 2,4-dimcthylphenol.
The above parameters were chosen because of their high rate of occurrence,
relative to other parameters. It should be noted that because these figures
are based on a limited number of data points (see Figure 10 and Table 11)
the data cannot be contoured.
Other factors which may have had an effect on past analytical performance
are summarized below. The system cannot generally detect light and dense
phase immiscibles. Furthermore, it is unknown what influence some of the
construction inadequacies may have on water quality. Texaco should
consider installing new wells using current recommendations adjacent to
some existing wells, and comparing analytical results of the paired wells to
determine if construction inadequacies affect water quality. These paired
wells will also aid in evaluating the effects of PVC casing material used in
some wells. Finally, the depth at which the sample is taken in relation to
the screened interval may affect past analytical results.
In summary, contamination has been documented in the past in the North
Area. Strong evidence exists indicating that contamination may be
migrating into the alluvial wells to the southeast. Organic contamination
does not appear to have migrated past the western property boundary.
Sufficient data do not exist to make a similar determination of the eastern
property boundary, however. With the possible exception of light and/or
dense phase constituents migrating off-site, the system as a whole seems
capable of monitoring the rate and extent of contamination in the dissolved
phase, assuming the appropriate analytes and wells are utilized.
Adequacy of Svstem The assessment program, as it was designed and
constructed, is adequate in some respects. Several potential and known
problems exist with the system, however. This Subsection addresses the
monitoring network as a whole, with major emphasis placed on the
adequacy of the assessment program currently on-going at the facility.
The system is able to detect dissolved contaminants migrating from the
HWMUs in most instances. An insufficient number of wells exist in the
unnamed middle member south and southwest of the CEP and the North
Land Farm. Because contamination has been documented in two wells in
this unit, some degree of hydraulic communication may exist. In addition,
the Teapot Sandstone subcrops just east of the North Land Farm. As
indicated on Plate 1, this unit dips gently towards the northeast. Because
92

-------
TEXACO PROPERTY
'BOUNDARY
M - 20
U - 22
L  7
*
M-7
CHEMICAL EVAPORATION POND
SOLID WASTE
LANDFILL
NORTH LAND FARM
M-29
M- 16
M-49A
H- 30
7900
u-32
M-33
SP-24
ASPHALT DISPOSAL
BRIDGE
LEGEND
FEET"
O Monitoring Well in Unnomed
Middle Member
 Monitoring Well in Uppermost
Aquifer
9 Monitoring Well in Alluvial
Aqui fer
SI Nested Monitoring Wells in
Uppermost Aquifer
B Nested Monitoring Wells in Uppermost Aquifer
and Unnamed Middle Member
~ Lyslmeter
Monitoring Well in Seep Area
O^Seep Area
FIGURE 20
170 
240-
19,000
6300.
'Benzene Concentrations
Toluene Concentrations
"Phenol Concentrations
*2,4- OimethyIphenol Concenfrotions
Concentrations of Select Organic Constituents (ug/l )
March, 1984 ( Texaco )
Texaco Refinery, Casper, Wyoming
93

-------
TEXACO PROPERTY
-BOUNDARY
 U -20
M-23
M- 25
M -22
M-24
L-7
M- 7
CHEMICAL EVAPORATION POND
SOLID WASTE
LANDFILL
U- 30
M-32
P-24
M-21
M - 31
NORTH LAND FARM
M -1 4
M- 16
CLIFF
8400
3000
ASPHALT DISPOSAL
1
SP-I
JI



U- 36
230
330
64,000
25,000

160
410
49,000
 12,000 

 tfl
*-26 M-SIA
o
M-27
B
M-ll
L-M
~
0
o
o
0
0
0
0
Or
LEGEND
FEET
O Monitoring Well in Unnomed
Middle Member
 Monitoring Well in Uppermost
Aquifer
O Monitoring Well in Alluvial
Aquifer
SI Nested Monitoring Wells in
Uppermost Aquifer
8 Nested Monitoring Wells in Uppermost Aquifer
and Unnamed Middle Member
~ Lyslmefer
Monitoring Well in Seep Area
Q^Seep Area
170'
240
19,000
6300 
FIGURE 21
8enzene Concentrations
Toluene Concentrations
Phenol Concentrations
2, 4- Dimefhylphenol Concentrations
Concentrations of Select Organic Constituents (ug/l)
June, I986 (Texaco)
Texaco Refinery, Casper, Wyoming
94

-------
TEXACO PROPERTY
-BOUNDARY
 M-ZO
U - 22
M-23
L-7
V
M-7
SOLID WASTE
LANDFILL'
M- 25
M- 30





M - 36



J/O
SP-I


410



64,000
I


I4t 000

y -49A

M- 8
JL
CHEMICAL EVAPORATION POND
M - 2 I
 .
M - 31	U- 34
n	
NORTH LAND FARM
M- 29
M-2S
M- 16
U-IS
M - 35
CLIFF
SP-24
ASPHALT DISPOSAL
BRIDGE
LEGEND
FEET
O Monitoring Well in Unnomed
Middle Member
 Monitoring Well in Uppermost
Aquifer
0 Monitoring Well in Alluvial
Aqui fer
B Nested Monitoring Wells ip
Uppermost Aquifer
8 Nested Monitoring Wells in Uppermost Aquifer
and Unnamed Middle Member
V Lysimeter
Monitoring Well in Seep Area
O^Seep Area
170-
240
19, 000
e loo-
Benzene Concentrations
Toluene Concentrations
Phenol Concentrations
2, 4 -Dlmethylphenol Concentrations
FIGURE 22
Concentrations of Select Organic Constituents (ug/l)
August, 1986 (Task Force)
Texaco Refinery, Casper, Wyoming
95

-------
eval-B
Texaco docs not currently maintain any wells screened in this unit, a
potential exists for contamination, especially dense phase immiscibles, to
migrate off-site undetected.
It is apparent that the system cannot differentiate the source(s) of
contamination between the CEP and/or possibly the North Land Farm.
Because of the extent of contamination and the proximity of the HWMUs to
each other (Figure 10), differentiating sources of contamination is probably
not possible. Under the original assessment program, Texaco included both
HWMUs as one single management unit under one assessment monitoring
system. Following Tcxaco's admission that contamination was coming from
the CEP and not the North Land Farm, an assessment monitoring program
under 40 CFR 265.93(d) was continued for both units.
The majority of the wells as designed and constructed arc only capable of
monitoring dissolved constituents. As has been discussed in previous
Subsections, relatively few wells have the capacity to detect light phase
immiscibles during both historic high and low water levels. The same holds
true for dense phase immiscibles, with the exception of the SP- series wells.
Several construction problems also exist with the monitoring system.
Although it is difficult to assess the impact of these problems in relation to
the adequacy of the system, they should be investigated by Texaco. As
noted in the previous Subsection, Texaco shoul.d consider installing new
wells next to existing wells and compare the results to determine what
influence the construction flaws may have on the system.
In summary, the assessment program as a whole is able to detect the extent
and rate of transport of dissolved species in the North Area. However,
Texaco should re-evaluate their choice of parameters to be analyzed. The
Task Force recommends that additional organic constituents be analyzed,
plotted and contoured. Correlations between organic contaminants and
organic indicators should be established, to demonstrate that the indicators
(e.g., TOC, phenols) accurately depict contaminant concentrations and plume
migration.
2. Proposed Ground-water Monitoring System under 40 CFR 264 (North Area)
Texaco has proposed in their Part B Permit Application that upon permit approval,
the assessment program currently on-going under interim status for the North Land
Farm would be dropped and that detection monitoring under 40 CFR 264
regulations would be implemented (Texaco, 1985). Tcxaco's logic is that
unsaturated zone monitoring beneath the North Land Farm and the CEP in the
past indicate that the CEP is the source of degraded ground water. Texaco has not
designated detection wells specific to the land farm under interim status.
During the assessment monitoring of both HWMUs under interim status, Texaco
determined that contamination was a result of the CEP and not the land farm. At
this time an assessment program is on-going for the HWMUs as a whole, but the
North Land Farm designate a detection program in order to monitor and detect an
immediate release from this unit. As previously mentioned, differentiating the
sources of contamination from the CEP and/or the landfill is probably not
possible, but if a detection monitoring system was implemented for the land farm.
96

-------
eval-B
additional releases specifically from the land farm could have been monitored for,
especially since wastes ceased to be disposed in the CEP after June 1982 but
continued in the North Land Farm. Because of this, baseline and statistical data
have not been provided for the North Land Farm area. In addition, Texaco must
institute a corrective action program under 40 CFR 264.101 to protect and/or
remediate the ground water from all releases from any SWMU, regardless of the
time at which wastes were placed in such unit. This pertains specifically to the
CEP pond as it is evident that some type of ground water restoration program
should be implemented. In fact at the time of the Task Force Evaluation, Texaco
had implemented a program involving the recharge of the CEP with river water in
order to enhance biodegradation and reduce concentrations of contaminants.
a. Detection Monitoring Program (North Land Farm)
The detection monitoring program proposed by Texaco under 40 CFR 264.98
is assessed below. This includes an assessment of the design, placement and
construction of the monitoring wells, past analytical performance and the
adequacy of the system.
Monitoring Well Svstem Design/Plnccment/Construction According to
Texaco's Part B Permit Application, two existing and two proposed
monitoring wells are specified to meet the requirements of 40 CFR 264
(Texaco, 1985). Texaco has designated monitoring well M-36 as the
upgradient and M-lOm as one of the downgradicnt wells. Although not
explicitly stated in the application, the point of compliance appears to be
the perimeter of the North Land Farm. The other two downgradicnt wells
(M-38 and M-39) arc to be installed upon application approval (Texaco,
1985). Figure 23 identifies the existing and proposed wells. A conflicting
group of monitoring wells have also been presented by Texaco "to provide
an environmental evaluation of the solid waste landfill and the North Land
Farm" (TriHydro, 1987b). In this scenario, monitoring well M-7s is
considered the upgradient well and M-lOs, M-49A, M-50A and M-51As the
downgradient. Information is not available stating with any certainty
which group of wells has been and will continue to monitor ground water
quality near the North Land Farm under the requirements of RCRA, 40
CFR 264. This Task Force evaluation will assess the monitoring system
proposed in the Part B Permit Application. The other group of wells was
previously discussed under the Interim Status assessment monitoring
program for the North Area.
The current and proposed monitoring wells should be designed to monitor
both light and dense phase immiscible constituents. Table 5 presents a list
of constituents detected in the ground water in the vicinity of the North
Land Farm and CEP. Following the recent land treatment demonstration,
17 hazardous waste constituents were identified in the soils under the North
Land Farm at depths of up to seven feet. These were at statistically
significant concentrations above background.
The potential for these constituents leaching and/or migrating into the
aquifer is quite possible. Based on past water level elevations,
approximately ten feet of soil are all that separate the extent of known
contamination in the soil and the ground-water surface.
97

-------
TEXACO PROPERTY
-BOUNDARY
SOLID WASTE
LANDFILL
CHEMICAL EVAPORATION POND
NORTH LAND FARM
M- 36
U- 38
>* K)m
M- 39
ASPHALT DISPOSAL
SITE
LEGEND
FEET
BRIDGE
 Existing Monitoring Well
O Proposed Well
FIGURE 23
Location of North Land Farm Existing
and Proposed Monitoring Wells
Texaco Refinery, Casper, Wyoming
98
Source: Part B Permit Application, 1985

-------
eval-B
According to the Part B Permit Application, Texaco only intends to monitor
at the water tabic of the uppermost aquifer (Texaco, 1985). The Task Force
has compiled Tabic 6 which demonstrates the ability of the North Land
Farm wells to adequately monitor light phase immiscibles relative to historic
high and low water table elevations. As indicated, monitoring wells M-36
and M-lOm are not capable of detecting light phase immiscibles during high
water table events because of screen placement. Historical high water level
elevations will probably fluctuate as a result of Texaco artificially
recharging the CEP. Complete water table elevations from wells in the
North Area from December 1986 to December 1987 arc located in Appendix
E.
Monitoring wells M-36, M-lOm and the proposed M-38 and M-39 wells arc
not designed to monitor dense phase immiscibles. This determination was
based on well logs (Appendix B) and top of shale bedrock (unnamed middle
member) (Figure 8). It should be noted that well M-lOm could detect dense
phases, based on well logs. As previously discussed, Plate 1 Section A-A' is
a cross section of the North Area, and indicates a depression in the shale
confining unit in the vicinity of the North Land Farm. The potential exists
for dense phase constituents to pool or conglomerate in this depression.
Currently, none of the existing and proposed wells could detect such a layer.
Additional wells arc required to monitor the lower depths of the aquifer for
dense phase constituents, or designating different wells for such. The depth
of the screened interval should intersect the upper aquifer/ confining unit
interface.
The horizontal locations of monitoring wells (existing and proposed) arc
based on local ground-water flow. The three downgradient wells meet the
regulatory and technical requirements for compliance point monitoring,
although based on the lateral distance between wells, additional compliance
point wells along the southern boundary are required. In this case, the limit
of the waste management unit is the point of compliance. Background
monitoring well (M-36) docs not, however, comply with the required
recommendations and regulations. Based on previously mentioned
potentiomctric surface maps constructed by Texaco and the Task Force
(Figure 15), M-36 is generally not hydraulically upgradient. The fact that
soil contamination exists below the treatment zone may indicate that
contaminants are entering the ground water. Background wells must be
designed/designated so that they are not affected by the unit they are
monitoring. An anomalous potentiomctric low has been noted in the past
near M-36. It stands to reason that representative background water is not
possible from M-36. The Task Force recommends that Texaco's choice of
background well M-36 be removed from the permit application. This
includes either designating an existing well as the background well, or
replacing M-36 with a new well(s). The Task Force recommends that a new
monitoring well be installed near M-36 to correct the previously mentioned
deficiencies.
Construction details for monitoring wells M-36 and M-lOm, in addition to a
brief narrative for the construction of the proposed wells (M-38 and M-39),
have been made available to the Task Force. Table 7 presents specification
and design information and Appendix B contains well construction details
(logs).
99

-------
eval-B
Monitoring well M-36 was drilled and completed on March 29, 1984 using a
6 1/4 inch hollow stem auger. Well M-lOm was drilled and completed on
January 25, 1982 using a rotary rig and a 6 1/2 inch bit. After drilling to
the total depth (Table 7), the well screen and casing were emplaced into the
borehole. A filter pack of known size and composition was not used in
these wells, as collapsed formation sand and drill cuttings were used. A
bentonitc seal was emplaced immediately above the screened interval in M-
10m. Well M-36 had approximately 17 feet of drill cuttings placed above
the screened interval prior to placement of the bentonite seal. A cement
surface seal was used in M-lOm, but not in M-36, as the top of the bentonite
seal was flush with the ground surface. Well development procedures were
not indicated.
Sufficient detail to fully-asscss the technical merit of these wells is not
available, although some deficiencies were noted. A bentonite bottom seal
was not used prior to well installation to prevent vertical migration of
constituents in M-36 and M-lOm. Well completion details do not specify or
indicate whether a bottom cap was used at the bottom of the screen. The
filter pack consisted of collapsed formation sand in M-lOm and drill
cuttings in M-36. If surrounding formation material is used as a filter pack,
the TEGD recommends that a sieve analysis to establish the appropriate well
screen slot size and a determination of the chemical inertness of the
formation material be performed (EPA, 1986a). This information was not
provided. A bentonite seal was emplaced immediately above the well screen
in M-lOm, although the thickness of this seal is not specified. In M-36,
approximately 17 feet of drill cuttings were emplaced above the screened
interval, effectively acting as a conductor of water. The TEGD
recommends a maximum of two feet of filter pack material above the well
screen to ensure discrete sample horizons (EPA, 1986a). A bentonite seal of
unknown thickness was emplaced above the drill cuttings (filter pack) to the
ground surface. A cement surface seal was not used in M-36, according to
completion details. In well M-lOm, approximately 25 feet of drill cuttings
were emplaced above the bentonite seal and below the cement surface seal.
The annular space above the bentonitc seal and below the surface seal
should consist of a cemcnt-bcntonite mixture, as recommended by the TEGD
(EPA, 1986a). Well casing stick-up was approximated for M-36, but not
given for M-lOm. Surveyed casing and/or reference point elevations arc not
specified on the construction details, as recommended by the TEGD (EPA,
1986a). The choice of the screened interval and construction material for
M-36 may be inadequate. Completion details indicate that a 20 foot well
screen was used (Appendix B).
Potential problems may occur when PVC is used in contact with aqueous
organic mixtures. These organics may encourage leaching from or
adsorption to the PVC polymer matrix. There has been recent concern over
the potential of vinyl chloride monomer to leach from PVC casing, which in
some cases may cause organic analytical interferences in situations where
prolonged exposure to aqueous organic mixtures may occur (Barcelona and
others, 1983). In certain situations under high organic concentrations, PVC
may also adsorb organic constituents (Barcelona and others, 1983).
Furthermore, PVC in contact with organics, particularly benzene, is not
recommended because of problems with long term structural integrity of the
100

-------
eval-B
well. In the future Texaco should review all available data/information on
casing materials carefully and make a selection accordingly before installing
new wells. This would be important at wells which exhibit significant
organic accumulations, especially since long term monitoring is probable.
Well development techniques are unknown. Based on a turbidity value of
450 N.T.U. obtained during the Task Force evaluation in monitoring well M-
36, development techniques or the choice of slot size appear inadequate.
The TEGD recommends that if turbidity values in monitoring wells exceed
5 N.T.U.'s, then the well performance should be re-evaluated by further
development or replaced as necessary (EPA, 1986a). Decontamination of the
drill rig and well casing were not discussed as recommended by the TEGD
(EPA,.-!986a). Finally, the anomalous low water levels at well M-36 noted
earlier in this report during the latter part of 1987 should be evaluated.
Proposed construction of monitoring wells M-38 and M-39 is discussed in
Texaco's Part B Permit Application (Texaco, 1985). The following is taken
verbatim from the application:
"Wells M-38 and M-39 will be installed in accordance with the RCRA
regulations at 40 CFR 264.97(c). Test holes will be drilled by the hollow
stem auger method. Total drilling depth is estimated to be 30 to 40 feet at
each location. Boreholes will penetrate 10 to 15 feet into the uppermost
aquifer.
"Soil samples will be taken from the ground surface to total depth. A
lithologic log of the strata encountered will be recorded for each borehole.
All drilling samples will be logged, recorded, bagged, and sealed in the
field. Particular attention will focus on the identification of stained or
discolored strata, odors, moisture content, and significant lithologic
variations.
"After drilling and logging is completed, schedule 40, PVC casing will be
installed to the total depth drilled. Casing diameter will be four inches.
Factory-slotted PVC casing will be set from about 10 feet below the water
table to about 5 feet above the water table. This range is desirable to
ensure that the wells remain functional during the expected fluctuations in
static water levels. Blank casing will extend from the top of the screen to
the ground surface.
"A gravel pack consisting of sand or gravel will be emplaced in the annulus
opposite the screen and up to about three feet above the screen. A
bentonite seal will be emplaced above the gravel pack. A concrete grout
will be emplaced in the annulus from the top of the bentonite seal to the
ground surface. A protective steel shelter with locking lid will be set into
the cement at each well.
"The drill stem and equipment will be cleaned with soap and water prior to
drilling each borehole to prevent contamination of the sites." (Texaco, 1985)
A full technical evaluation of the two proposed monitoring wells would be
pointless without actual construction details. However, the Task Force
recommends the following changes: The well screen length should be re-
101

-------
eval-B
evaluated by Texaco. Fifteen feet of well screen may not provide water
quality at discrete locations. The proposed wells are not capable of
detecting dense phase immisciblcs. Finally, the choice of material (PVC) in
the construction of these wells should be re-evaluated in terms of leaching/
adsorption and long term structural integrity.
Past Analytical Performance According to the Part B Permit Application,
water quality data have been collected quarterly since March 1982 at 23
wells in the vicinity of the CEP and North Land Farm (Texaco, 1985). The
two existing wells proposed under 40 CFR 264.98 are included in this
sampling frequency (Table 10).
Existing water quality data, based on the horizontal location of well M-lOm
and past analytical data, arc representative of water downgradient from the
North Land Farm. It should be noted that well M-lOm is screened towards
the bottom of the saturated zone of the upper aquifer, thus prohibiting the
detection of light phase immisciblcs. Therefore, well M-lOm is capable of
detecting only dissolved and dense phase contaminants.
Texaco indicates in their Part B Permit Application that well M-36 is the
background well for the North Land Farm. Past water quality data show
that this is one of the most contaminated wells in the North Area.
Potcntiomctric maps constructed by Texaco and the Task Force clearly
indicate that this well is generally not upgradient. Furthermore, the ground
water depression observed in this well should be explained (Figure 11).
Also, because the contamination source cannot be currently delineated, the
CEP is most likely affecting water quality in well M-36. The vertical
placement of the screen in well M-36 is located to monitor the water table
(for light phase immiscibles) during relatively low stages only.
According to well completion logs, M-36 has a 20 foot screened interval. A
screen of this length may not provide discrete samples, as factors including
dilution can affect water quality. Finally, it should be noted that well M-36
may be capable of detecting dense phase components based on Figure 8,
Bedrock Surface Contours. However, the well log does not indicate that the
unnamed middle member was encountered during drilling (Appendix B).
In summary, only well M-lOm has provided adequate samples of ground
water beneath the North Land Form for dissolved species, but as previously
stated, it cannot monitor for light and/or dense phase immiscibles at the
point of compliance. To avoid redundancy, analytical data from these
wells, in addition to others sampled by Texaco in the past, were previously
presented in the Ground-Water Monitoring System under Interim Status
(North Area) - Assessment Program section earlier in this report. Also,
because a detection monitoring program under 40 CFR 265 was not
implemented at the land farm, baseline data and/or statistical evaluations
were not available.
Adequacy of Proposed Ground-Water Monitoring Program The ground-
water system existing and proposed in Texaco's Part B Permit Application
does not meet technical recommendations and regulatory requirements. The
most serious problem is Texaco's choice of a background monitoring well.
Well M-36 is neither hydraulically upgradient, nor able to provide water
102

-------
eval-B
quality unaffected by the North Land Farm. An apparent ground-water
depression observed at well M-36 (Figure 14) should be explained. Texaco
should evaluate this and designate other existing or new wells as the
upgradicnt well(s). Regulation 40 CFR 264.97(g)(3)(i) states that background
quality may be based on sampling of wells that are not upgradient from the
waste management area where hydrogcologic conditions do not allow the
owner or operator to determine what wells are upgradicnt. Downgradient
wells M-lOm (existing) and M-38 and M-39 (proposed) are located at the
compliance point from a horizontal view. Additional wells designed to
monitor the southern boundary of the North Land Farm are also warranted.
Vertical placement of the existing and proposed downgradient wells arc
currently not capable of detecting dense phase immisciblcs. Finally,
construction details indicate that representative water quality samples may
hot be possible. Texaco should consider constructing new wells using
current recommendations adjacent to existing wells, and compare analytical
results to determine if construction flaws do in fact affect water quality.
Of importance for the North Land Farm unit is to design a ground-water
monitoring system which meets the 40 CFR 264 Subpart F requirements, and
is capable of detecting statistically significant releases over the long term.
This includes ground-water monitoring specifically for the Land Farm, even
during the corrective action program for the CEP or other SWMUs required
under 40 CFR 264.101.
In summary the main purpose of the detection monitoring system should be
to detect releases from the land farm given all of the other variable
hydrogeologic and hydrogcochemical conditions in the immediate area
surrounding the land farm.
b. Corrective Action Program under 40 CFR 264.101 (CEP)
This Subsection docs not assess a corrective action program specified by
Texaco, as the facility has not designated such a program under RCRA at
this time. Rather, this Subsection reflects the view of the Task Force
relative to the regulations under 40 CFR 264. Due to the serious nature of
this deficiency in regards to permitting the North Land Farm, it merits
discussion.
As a review, Texaco maintains that the ground-water monitoring program
under 40 CFR 264 for the land farm would be detection monitoring (40
CFR 264.98). This is due to the fact that unsaturated zone monitoring at
both the CEP and the land farm during interim status confirm that ground
water degradation is due to the CEP. Quoting 40 CFR 264.101, "The owner
or operator of a facility seeking a permit for the treatment, storage or
disposal of hazardous waste must institute corrective action as necessary to
protect human health and the environment for all releases of hazardous
waste or constituents from any solid waste management unit at the facility,
regardless of the time at which waste was placed in such unit."
Texaco readily admits to degraded ground water in the North Area,
emanating from the CEP. This is evident by the assessment program
currently on-going under interim status. Based on the above discussion,
Texaco must operate a corrective action program under 40 CFR 264.101
103

-------
eval-B
because corrective action under 40 CFR 264.100 is not applicable as wastes
were not received in the CEP after June, 1982 according to Texaco. As part
of the program, Texaco must specify a ground water monitoring program
capable of determining the effectiveness of the remedial action program in
the form of recharge to the CEP, which at the time of the Task Force
Evaluation had just begun. This would entail specifying the number and
location of the wells, the parameters to be analyzed and the methods of
evaluating data to show decreases in contaminant concentrations and the
responsible hydrogcochemical mechanisms at work (e.g., dilution vs.
biodegradation).
The Task Force recommends that Texaco submit a ground water remediation
program pursuant to 40 CFR 264.101 which at a minimum specifics:
o The number and locations of wells to be utilized, rationale for their
selection and an evaluation of the construction details to permit
assessment of the integrity of each well.
o Designate those indicator parameters and waste constituents to be
used to compare to a background well which can provide data that
can accurately represent the conditions at the site. This is essential
in order to show that all waste constituent concentrations of concern,
the indicator parameters, arc decreasing
o Design a sampling and analysis program, which would complement
data evaluation techniques, which can ultimately show the
effectiveness of restoring the quality of ground water in the North
Area.
A number of possible analytic procedures could be applied to existing data
to assess the effects of recharge of river water on the attenuation of
contaminant concentrations in ground water in the CEP area. These could
include, but not necessary be limited to, the following kinds of data
evaluation techniques:
o Trend analyses of contaminant concentrations versus time in
monitoring wells, in an effort to isolate the effects of river water
recharge from attenuation effects occurring prior to recharge.
Monitoring wells might be grouped according to their distances
downgradient from the recharge pond in an effort to eliminate some
variability in the data.
o Reassessment of trends of maximum quarterly contaminant
concentrations, to determine whether the data more probably suggest
a stabilization of maximum concentrations, rather than a continuing
decline. In addition, the wells at which maximum quarterly
concentrations are detected should be identified, and an assessment
made as to whether or not there is an identifiable trend of distance
of maximum concentration from the CEP versus time.
o Since Texaco has suggested that changes in sulfide and sulfate
concentrations may correlate with aerobic or anaerobic
biodegradation (Hamilton, 1988), an examination of temporal of
104

-------
eval-B
spatial trends in variations of sulfide/sulfate ratios might provide
useful information. Similar geochcmical studies might be possible
using other chemical-species.
o Mathematical modeling of the hydraulic effects of river water
recharge could provide useful information regarding relative rates of
recharge versus ground-water underflow, rates of transport of
recharged water within the uppermost aquifer, and the arcal and
temporal extent of the effects of river water recharge. Furthermore,
by treating the recharged water as an ideal tracer within an
appropriate mass-transport model, it should be possible to estimate
the attenuation due solely to dilution and dispersion effects, and thus
provide estimate, of the attenuation due to chemical and biological
degradation phenomena.
3. Compliance with Applicable Regulations
This subsection addresses the regulatory deficiencies of the present interim status
and proposed RCRA ground-water monitoring programs. At this time the CEP has
been "clean closed" under RCRA and Texaco continues to monitor ground water
under an assessment monitoring program. This program has been implemented to
address ground-water contamination emanating from the CEP.
The North Land Farm is currently operating under the same interim status
assessment monitoring program as the CEP (40 CFR 265.93(d)). A Part B
application has been submitted for continued operation of this unit. A permit has
been issued to Texaco for the Land Treatment Demonstration required prior to
issuance of a permit. Because Texaco intends to continue operation of this unit,
they will be required to operate their ground-water monitoring system in
compliance with 40 CFR 264 Subpart F, and must provide permit information
pursuant to 40 CFR 270.14(c).
a. Interim Status Program
The interim status ground-water monitoring system for the North Area has
changed significantly since its inception in 1982. In 1982, as previously discussed,
four wells were designated as RCRA wells under detection monitoring. Over the
last 6 years changes in the designation of certain wells (detection vs. assessment),
implementing a corrective action program (recharging the CEP), and the closure of
the CEP have complicated the analysis of historical data from these wells. At this
time Texaco considers the North Area to be operating under assessment monitoring.
Based on the above discussion, Texaco's assessment monitoring program must
identify the extent and rate of migration of contamination, in addition to defining
the concentrations of hazardous waste constituents within the plume. In addition,
because a corrective action program (recharging CEP) will be on-going, the
assessment monitoring program must be capable of demonstrating the effectiveness
of the corrective action. The deficiencies noted in the interim status assessment
monitoring system are as follows:
105

-------
eval-B
o Texaco must determine the rate and extent of migration and concentration
of hazardous waste in the groundwater (40 CFR 265.93(d)(4)). Currently,
Texaco has made the above determination on only four parameters (TOC,
phenol, sulfide and ammonia). The rate and extent of migration and
concentration of all Appendix VII wastes must be established.
o Because Texaco maintains that the CEP is the source of contamination in
the North Area, the North Land Farm should not be included under an
assessment program in conjunction with the CEP. Instead the North Land
Farm should have a designated detection monitoring program which will
allow for the immediate detection of releases from this unit (40 CFR
265.90). Data collected from this interim status program, which Texaco has
not yet implemented, could be used as baseline data in evaluating the
proposed detection system under 40 CFR 264.98.
o Each well must be constructed in a manner that maintains the integrity of
the well bore hole (40 CFR 265.91(c)). The casing must be screened to
enable sample collection at depths where appropriate aquifer flow zones
exist. The annular space must be sealed to prevent contamination of
samples and the ground water.
Based on the refinery waste constituents, the monitoring system should be
capable of evaluating the presence of both light and dense phase
immiscibles. Only a few of the monitoring wells in this area arc capable of
detecting light phase constituents at both historic high and low water levels,
in addition to detecting a dense phase component. Numerous wells also
have construction deficiencies which may influence the quality of the
samples and may provide a downward potential migration pathway for
contaminants.
b. Proposed 40 CFR 264 Ground-Waler Monitoring
Because Texaco is seeking a permit to continue the operation of the North Land
Farm, the ground-water monitoring system, as previously stated, should be capable
of detecting an immediate release at the point of compliance as outlined in 40 CFR
264 Subpart F. In operating the North Land Farm ground-water monitoring
system, it is important to take into consideration how the recharging of the CEP
will affect the ground-water flow in the vicinity of the land farm. The ground-
water monitoring system must be capable at all times (during recharge and
following completion of the CEP corrective action program) to detect immediate
releases from the land farm. It is evident that this will require a detailed and
continuous evaluation of the ground-water flow conditions and hydrodynamic
effects from the CEP. Because ground water contamination is known to exist in
the North Area, Texaco will also be required to implement a corrective action
program under 40 CFR 264.101 for the CEP.
The following deficiencies for the proposed North Land Farm ground-water
monitoring system are based on the ground-water monitoring requirements set
forth by Texaco in their Part B application and those deficiencies found by the
Task Force to be lacking for implementing a corrective action program under 40
CFR 264.101 for the CEP:
106

-------
eval-B
North La.nd Farm
o Texaco should implement a monitoring system consisting of a sufficient
number of wells to yield ground-water samples which are representative of
background water quality unaffected by leakage from the regulated unit
and which represents the quality of ground water passing the point of
compliance (40 CFR 264.97(a)). Texaco designated well M-36 as the
upgradicnt well designed to meet this requirement. This well is not always
hydraulically upgradicnt from the North Land Farm. Due to its location,
background water quality could likely be affected by the land farm.
Furthermore, ground water flowing from well M-36 does not pass under the
point of compliance. Finally, Texaco should evaluate the anomolous water
levels and contaminant concentrations in well M-36. It appears that this
well may be acting as a sink for contaminants and could introduce
contamination into the lower portion of the uppermost aquifer. Therefore,
Texaco's choice of M-36 as an upgradicnt well is inadequate.
o Texaco must designate monitoring wells at the point of compliance which
will detect an immediate release of hazardous waste constituents to the
ground water (40 CFR 264.98). Based on the permit application, existing
well M-lOm and proposed wells M-38 and M-39 located at the point of
compliance, an insufficient number of wells exist directly south of the
North Land Farm.
o All regulated monitoring wells must be constructed in a manner that
maintains the integrity of the borehole. The casing must be screened to
enable sample collection at depths where appropriate flow zones exist. The
annular space must be sealed to prevent contamination of samples and the
ground water (40 CFR 264.97(c)). Because constituents which may exist in
both light and dense phases have been documented, the monitoring wells
should be screened to detect these phases. Well M-lOm is capable of
detecting dense phase components, but not light phase components. Well M-
36 is not constructed so as to detect light phase layers during relatively or
historic high water levels, nor is it capable of monitoring the depths of the
aquifer for dense phase constituents. Both monitoring wells M-lOm and M-
36 have construction deficiencies which may influence the quality of the
samples and may provide a downward potential migration pathway for
contaminants.
o Texaco is required to monitor for indicator parameters, waste constituents
or reaction products that provide a reliable indication of the presence of
hazardous constituents in ground water (40 CFR 264.98(a) and
270.14(c)(6)(i)). The parameters chosen by Texaco include benzene, toluene,
phenol, lead and chromium. These parameters are already present in the
ground water and any leakage from the North Land Farm may not be
detected. Texaco must provide a list of parameters unique to the land
treatment wastes that would serve as reliable indicators of hazardous
constituents migrating from the unit.
CEP
o Texaco must implement a corrective action program which mitigates ground
water contamination from any solid waste management unit (40 CFR
107

-------
eval-B
264.101). Texaco has stated that the degraded ground water in the North
Area is from leakage of the CEP. Because a Part B permit has been applied
for, the facility is required to initiate such a program. This should include
specifying all pertinent information required to determine the effectiveness
of the program. 40 CFR 264.101 lacks specific regulatory requirements for
this corrective action program, therefore the following technical
deficiencies arc listed based on what the Task Force feels to be an
appropriate corrective action program:
Texaco should first establish a waste management boundary with a
set of designated RCRA wells installed at this boundary. These wells
should be continuously monitored in conjunction with those wells
designated under the corrective action program for continued
evaluation of the effectiveness of the corrective action program
under 40 CFR 264.101.
Texaco should establish a list of hazardous constituents and
concentration limits for those hazardous waste constituents to be
used in order to monitor the effectiveness of the corrective action
program. These constituents should include not only indicator
parameters, but those hazardous constituents detected in the ground
water and which are unique to the CEP. In setting concentration
limits, close scrutiny of the background wcll(s) should be performed.
Texaco must designate those wells which will be utilized as part of a
groundwater monitoring program to aid in evaluating the rate and
extent of contamination. These wells may also be utilized as part of
the corrective action ground-water monitoring program which will be
used to determine the success of the corrective action. The data
evaluation techniques used to determine the effectiveness of
corrective action and the data collection schedule should be
presented. Texaco should outline in detail those wells and data
evaluation techniques which will be utilized as part of this corrective
action ground-water monitoring program under 40 CFR 264.101.
At this time, Texaco has only provided a description of the rate and
extent of migration and concentrations of four indicator parameters:
phenols, TOC, sulfide and ammonia. It appears that Texaco has only
analyzed for organics four times, including the Task Force split
samples, since 1982. Only during the Task Force Evaluation was an
Appendix IX scan completed. An identification of organics on a
continual basis is essential in order to relate those concentrations to
the indicator parameters (e.g. TOC and phenols) that are currently
being utilized to determine the effectiveness of the corrective action
program. Texaco should not only evaluate indicator parameters over
time for effectiveness of the corrective action program, but must also
show that concentrations of specific hazardous waste constituents are
also being addressed or treated as part of the program.
4. Ground-Water Monitoring System (South Area)
The area south of the North Platte River (South Area, Figure 15) currently
maintains a network of ground-water monitoring wells, but is not subject to the
108

-------
eval-B
ground-water monitoring requirements of RCRA as outlined in 40 CFR 264 and
265 subparts F. As previously mentioned the South Area contains the process units
of the refinery and several tankage units. RCRA-regulated or interim status land
disposal units do not exist in this area. The South Area docs, however, contain
numerous solid waste management units which possess relatively high potential for
contamination to the ground water. Such units include the service water return
ditch; storm water surge ponds; PCS coke settling pond; precipitator and accelerator
ponds; barometric separator and barometric lagoons; several tank farms; and the
process area and associated piping and historical spills. In addition, the reports
reviewed by the Task Force indicated that a waste oil dump, old ponds and dump
sites located along the south bank of the river may also be contributing to releases
to the ground water.
a. History
Investigations have been ongoing in the South Area since the 1940's to
investigate and/or remediate the accumulation of large quantities of
floating hydrocarbons in the central tank farm area (Figure 2). In addition
a new study (1986/1987) is currently underway to investigate ground-water
contamination beneath the southeastern corner of. the site adjacent to the
east tank farm and land farm area (Figure 2). This study was implemented
as a result of the Task Force evaluation analytical results. A brief history
of ground-water monitoring and hydrocarbon recovery activities for the
South Area is as follows:
o Between 1947 and 1958 Texaco drilled and installed approximately
74 wells which were used as monitoring wells, hydrocarbon recovery
wells and for exploration of the local geology.
o In July 1957, an east and west open interceptor ditch was installed to
intercept the flow of hydrocarbons in the ground water before they
seeped into the North Platte River. This open ditch system was
replaced with a closed system in 1972/1973.
o Sometime after 1957 a "clay barrier" was constructed east of the east
end of the cast interceptor ditch to halt hydrocarbon migration
(WWC, 1982c).
o In 1972 and 1973, the east and west interceptor ditches were replaced
with a closed interceptor system which consisted of two 24-inch
perforated culverts stacked one on top of the other and buried. A
concrete sump was installed at the east and west end of the west and
east interceptor ditches, respectively. Each sump contained a 300
gpm pump (WWC, 1982c).
o From December 1981 to January 1982, 15 additional wells were
drilled as part of the Phase I studies to better define the local
geology, because detailed lithologic descriptions were not available
(WWC, 1982b).
o From June to July 1982, 27 additional monitoring wells were
installed to further define the extent of hydrocarbon accumulation
and the local hydrogeologic conditions (WWC, 1982c).
109

-------
eval-B
o As a result of the June and July 1982 investigation, Texaco
submitted an Application for Permit to Construct the Hydrocarbon
(Oil) Recovery Project proposed at the Casper Texaco Refinery in
March and June 1983 (WWC, 1983b).
o In July and August 1983, Phase I of the Oil Recovery operations
were implemented with the construction of four recovery wells, nine
recharge wells and 11 additional monitoring wells. The system
became operational (uninterrupted) in September 1983.
o From April through June 1984, Phase II of the Oil Recovery system
was undertaken. This phase included the installation of two
additional recovery wells, 13 recharge wells, and four monitoring
wells (April 1984). In April 1985, five additional recharge wells were
installed.
o In August 1986, EPA performed a Task Force Evaluation of the
Texaco Refinery which included split sampling of six wells and the
PCS Coke Settling Pond in the South Area.
o As a result of the Task Force Evaluation ground-water analytical
results, contamination was detected beneath the southeast corner of
the Texaco Refinery. In December 1986 and January 1987, eight
additional monitoring wells were installed to further investigate this
contamination (WWC, 1987b). Because this investigation was
undertaken after the Task Force Evaluation, it will not be discussed
in detail.
A total of 139 ground-water monitoring wells were installed in the South
Area from 1947 until January 1987. These wells were installed to monitor
accumulations of floating hydrocarbons, oil recovery activities and
characterization of the hydrogeologic conditions.
As part of the oil recovery system, a total of six recovery wells and 27
recharge wells have been installed.
Of the 139 ground-water monitoring wells and 33 oil recovery system wells,
numerous wells either do not contain completion records or geologic logs, or
they have been plugged, abandoned, or arc no longer in use. An inventory
of the monitoring wells as tabulated by Texaco as of 1982 is included as
Appendix C. In evaluating the South Area, the Task Force only utilized
wells where completion records and/or geologic logs were available. Fifty-
nine ground-water monitoring wells which met this criterion are listed in
Table 12 with their locations identified in Figure 15. This list of wells does
not include those related to oil recovery operations, although their locations
are included on Figure 15. The oil recovery system is discussed in further
detail later in this section.
Those wells which were not utilized by the Task Force include the wells
listed in Appendix C minus those presented in Table 12. Also wells SS-52
through SS-55 installed in April 1984 were not included, as no records were
provided to the Task Force.
110

-------
t22-cap
DATE
yell	iwsmicp
SSI	12*9-61
SS-2	12-10-81
SS-3	12-11-61
SS-4	12-11-61
SS-5	12-12-61
SS-6	12-13-61
SJ-7	12-15-61
SS-9	1-4-62
APPfiOX.
GROUMO
SUAFACE
CASING	ELEVATION
H	(HSt)
4" CALV	5066
4" CALV	5085
4" CALV	$06$
4- GAIV	5085
4" CALV	5085
4- CALV	S104
4U CALV	5116
4M CALV	5106
COHPLETION
INTERVAL
(SCttffW)
27-52
(5059-5054)
7.5-12.5
(5077.5-5072.5)
25-50
(5060-5055}
6-13
(5077-5072)
15-18
(5070-506/)
6-9
(5098-5095)
42-45
<5074-5071)
42-45
(5066-5063)
Table 12
Srxe < Hft t pr>  Smith Arft
OfPTH 10
Bcoaocr
NONI1OAE0
INTERVAL
AVERAGE
WATER
LEVELS
C04RECIEO
MAT, AUG., OCT.
1?85
COUIO
OETECT
HEAVY
IHMSCIBLES
YES/MO/POSSIBtE
COUIO
OEIECT
LIGHT
IHMISCIBLES
YE 5/HO/pnsSIBl E
35
(5051)
5060.3
37
(5046)
5060.5
36
(5049)
5060.6
19
<5066>
5081.6
20
(5065)
5076. S
19
(5065)
60
<5056)
5064.9
54
(5054)
5065.6

-------
t22*csp
DATE
WELL	IMST ALI CO
N>
SS-IO	12*18-81
SS-11	12-20-01
SS-12	12-7-81
SS-1J	6-25-52
SS-14	7-8-82
SS-1S	7-11-82
SS-I&	7-11-02
SS-17	7-11-82
APPRO*.
CROUWO
SURFACE
CASING	ELEVATIOU
TYPE	(HSL)
4" GALV	5098
4" CALV	5098
4** CALV	5090
4" PVC	5111
4" PVC	5116
2" PVC	5113
2" PVC	5096
2- PVC	5089
wall
COMPLETIOM
IM1C8VAL
(SCftfm
16-21
(5080-5077)
5-25
<5093-5071)
11-16
(5079-5074)
32.3-42.3
(5078.7-5068.7)
31.7-41.7
(SOW. 3-5074.3)
29.1-35.1
(508J.9-5077.9)
8.3-17.3
(5057.7-5075.7)
3.7-12.7
(5085.3-5076.3)
55* tfla 7-14 -82
2" PVC
soaa
3.2-13.2
(5084 .8*5074 .8)
Table 12
IMf>(loft|  Sonih Arg>
AVERAGE
UAIER	COULD	COULD
LEVELS	OETECT	DETECT
COflBfCItO	HEAVY	LIGHT
DEPTH 10	HOMITOAEO	HAY, AUG., OCT.	1MHISCIBLES	1HXISCIBLES
BEOaOCt	IMlEiVAL	19*5	YES/MO/POSSIBlC	YfS/MO/POSSIBLE
23
(5 0 75)
5085.1
26
(5072)
5078.6
20
(5062)
5081.83
28.5
(5082.5)
BEOROC*.
5085.9
68.5
(50;7.5)
37.5
(5075.5)
18.5
(5077.5)
12.5
(5076.5)
U.O
(5074)

-------
t22-casp
Tblt 12
WH	 South Are>
WELL
DATE
iMsmifO
CASING
U
APPBOX.
CROUMO
SU8FACE
eicvatiou
(H?l )
CCNPICTION
ItffCffVAL
(SCBFfW)
DfPTH TO
efOBocr
MOMMOflfO
IXIMV'I
AVEBAGE
UA1E8
LEVELS
COflBECICO
HAT, AUG., OC1.
1065
COULD
OEIECT
HEAVY
IMHI5CI0US
TfS/HO/POSSIBl
couio
DETECT
LIGHT
IHHJSCIBLES
YES/HO/POSSIBLE
IS-19	7-H-B2
2- PVC
5057
7.5-17,5
(5079.5-5069.5)
10.0
(5069)
5060.4
SS-20	7-U-B2
5095
10.3-20.3
(5084.7-5074.7)
25.0
(5070)
5062.fi
SS-21	7-16-02
11.221.2
(5083.8-5073.6)
22.5
(5072.5)
5062.3
SS-22	7-1J-fi2
5099
19.2-29.2
(5079.6-5069.6)
17.5
(5061.5)
5061.7
SS-23	7-14-62
11.0-21.0
(5065-5075)
23.0
(5073)
POSSIBLE
SS-24	7-K-B2
2" PVC
5091
9.5-19.5
(5031.5-5071.5)
22.0
(5069)
5091.5
SS-25	7-15-82
10-8-19.8
(5085.2-5076.2)
22.5
(5073.5)
5081.4
POSSIBLE
SS-26	7-15-82
2- PVC
ll.fi-20.6
(5080.2-5071 .2)
22.5
(5069.5)
5061.4
SS-27	7-15-82
2" PVC
10.3-19.3
(5082.7-5073.7)
22.5
(5070)
5081.7

-------
t22-cop
APPBOX.
GfiOUWD
SUBfACE	COUPLET ION
DATE	CASING	CLEVA1ION	lUIfSVAL
WELL	1HSTAUCP	1TPE	(NSL)	CSCBftW)
SS-28	7-15*82	2* PVC	5095.5	U.32J.3
(5081.2-5072.2)
SS-29	7-15-82	2" PVC	5090	7.0-16.0
(5083-5074)
SS-30	7-16-82	2M PVC	5088	5.1-15.1
(5032.9-5072.9)
SS-32	7-16-82	2 PVC	5088	13.0-23.0
(5075-5065)
SS-33	6-26-82	2" PVC	5084	2.5-8.5
(5081.5-5075.5)
SS-34	6*26-82	2" PVC	5084	4.4-14.4
(5079.6-5069.6)
SS-35	6-27-82	2M PVC	5086	3.6 13.2
(5032.4-5072.8)
SS-36	6-27-82	2" PVC	5085	4.8-U.4
(5080.2-5070.6)
SS-37	6-27-82	2" PVC	5088	4.9-K.5
(505J.1-5073)
T>ble 12
Spec W lot\ont - South Ary
AVERAGE
UATEB	COULD	C0U10
LEVELS	DETECT	DETECT
CORRECTED	HEAVY	LIGHT
DEPTH 10 HCM|T0*C0 MAT, AUG., OCT.	IHMISCIBIIS	IKHISCI81ES
9fQ>OCr IM T t BVAL 1985	YES/HO/POSS181E	YfS/HO/POSSIB1E
27.5	AlV	5081.7
(5068)
22.5	AlV	5081.9
(5067.5)
15.1	ALV	5082.2
(5072.9)
24.0	ALV	5082.2
( 50M)
8.0	ALV	5078.9
(5076)
2J.7	ALV	5080.1
(5060.3)
25.5	AlV	5079.9
(5060.5)
32.8	AlV	5080.4
(5052.2)
31.4	ALV	50e0.6
(5056.6)

-------
t22-coip
U1
0A1E
iLV
CAS 1KG
UPC
APPBOX.
C80UKD
SURFACE
eiCVATIOM
(HSU
cohpi e now
IMTf RVAl
(SCBffM)
M-39	7-12-82
2" PVC
-109a
1.7-10.7
(5096.J-5087.J)
SS-40	1903
2" PVC
0.0-16.0
OOAS.i-son.n
SS-41	1983
2- PVC
5097.18
11.0-21.0
(5056.2-5076.2)
SS-42	1983
2- PVC
3092.68'
6.8-16.8
(5085.9-5075.9)
SS-43
5093.29'
4.3-U.3
(5068.9-5078.9)
SS-U	1983
5092.97
7.0-17.0
(5085.9-5075.9)
SS-45	1983
4- PVC
5097.29'
9.0-19.0
(5083.3-5078.3)
SS-47	1983
10.0-20.0
(5086.8*5076.8)
SS-48	1983
5099.77
12.0-22.0
(5087.8-5077.8)
Uhlt 12
WtU Spec 1 f IcH loot  South
0EPTM TO
BfQgQCC
MMITOftCO
|MTf ivt.
AVCtACC
VA1ER
LEVELS
CORRECTED
HAT, AUC., OCT.
1965
COULO
DEIECT
HEAVY
IKM1SCIBLCI
TES/MO/POSSIBlf
COULD
DEIECT
LIGHT
IKXISC181ES
TE S/MO/PQS S191E
11.0	ALV	HO	POSSIBLE	HO
(5087)
NA	ALV	5081.1	HO	YES
MA	ALV	UO	MO	HO
HA	ALV	5081.1	NO	YES
MA	ALV	5080.9	UO	YES
HA	ALV	5080.9	WO	YES
HA	ALV	5081.2	HO	YES
HA	ALV	5082.2	NO	YES
HA	ALV	5082.5	UO	YES

-------
tZZ-cisp
TabU \l
UtU $f>f c H I cat tooi  South Are
DATE
tU 1"s"UfP
CASING
TYPE
APPRO*.
GROUND
SURFACE
ELCVAT 104
(MSI )
COHPlETION
mcflvAi
(SCgffU)
OEPTN 10
aEoaoct
KOMIIOAEO
iWTtBVAL
AVERAGE
WAT CI
LEVELS
CORRECTED
HAY, AUG., OCT.
1965
COULO
DETECT
HEAVY
IKMISCIILES
YfS/HO/POSSIBlE
COULD
OEIECT
LIGHT
1HHISCIBIES
YfS/MO/POSS > 81 E
SS-49	1963
SS-50
1983
1963
SS-56	12*29*66
SS-57	12-30-86
SS-56	12-30-86
2* PVC
2" PVC
5093.24
5095.20
5098.51
5106.9
5112.1
5114.0
5.3-15.3
(5087.9-5077.9)
8.7-16.4
(5066.5-5076.6)
9.7-19.7
(5066.6-5076.6)
16.2-25.9
(5090.7-5081)
21.6-31.4
(5090.5-5060.7)
24.2-13.8
(5089.6-5060.2)
5062.3
30'
(5076.9)
WE
5061.9
5085.7
5035.7
5085
.7T2'
SS-59	12-31-86
SS-60	1-5-87
SS-61	1-6-87
2" PVC
5114.4
5110.3
5106.0
2).6-3).6
(5090.6-5060.8)
19.6-29.6
(5090.5-5060.7)
15.5-25.3
(5090.5-5f0.7i
HE
5065.8'
5085.r
YES

-------
t22-caip
KEU
DATE
IWSTHICP
CASIMG
TYPE
APPROX.
GROUND
SURFACE
CLEVATION
cohple t i on
INTERVAL
(SCOf f N)
SS-62	1-7-67
2- PVC
5114.6
24.5-34.4
(5090.1-5080.2)
SS-63	1-7-87
siu.a
26.6-35.6
(50&6-5079.2)
N-41	2-7-52
46-49
(5077*5074)
M*41a	6-21-62
2 PVC
-5114
49-55
(5065-5059)
12-19-ei
-5097
3-25
(5094-5072)
oa-2
1-7-62
4- ?
19-59
(5077-5057)
1*	TOP Or CASIMG ELEVATION (HSl)
2*	WATER LEVELS (MOT CORRECTED), SEPTEMBER 1987
HO	HO OATA
ME	MOT EMCOUMTEREO
GALV	GALVANIZED STEEL
MA	MOT AVAILABLE
ThU 12
Uell jpfclHculoni - South lri
OEPTM TO
erpBoc<
HOMITOAED
|MtBV
-------
eval-B
Completion records and geologic logs for the South Area wells utilized by
the Task Force arc also presented in Appendix C.
b. Monitoring Well System Design/Placemcnt/Construction (South Area)
The facility-wide ground-water monitoring system in the South Area was
installed to define the extent- of accumulation of floating hydrocarbons and
local hydrogeologic conditions. Subsequently, the system has not been
utilized to define the water quality which would include dissolved
constituents and also dense phase immiscible components of refinery wastes.
This docs not include the southeast area of the refinery, where ongoing
investigations are evaluating both dissolved and light immiscible
contamination.
The horizontal placements of the South Area wells were based on previous
data on hydrocarbon accumulations and also local ground-water flow
conditions. This resulted in almost all of the wells being completed to
define the extent of floating hydrocarbons. For the remaining discussion,
the central South Area and the southeast corner will be discussed separately.
Central South Area The vertical placement of the screened intervals of
most wells arc completed in the alluvium with emphasis placed on screening
the water table to detect floating hydrocarbons. Only two wells in the
South Area, SS-13 and SS-22, had screened intervals within the unnamed
middle member. Well SS-13 is discussed under the Southeastern Corner
Area.
Based on the refinery waste constituents (Table 5), the ground-water
monitoring system should be capable of monitoring the water table for light
immiscibles, dense immiscibles and also dissolved organic and inorganic
constituents. According to Texaco, oil samples from ten wells showed virgin
to cracked contaminated products with the cracked content increasing
eastward, and distillation tests indicated contaminated refined product
mixtures ranging from nearly heavy straight run naphtha to gas oil (WWC,
1982b).
To evaluate the monitoring well network's capability of detecting light
immiscibles. Table 12 presents data for average water levels, corrected for
hydrocarbon accumulations taken from most wells in May, August and
October 1985 corrected water levels, except as noted on the Table. These
averaged water levels were compared to screened interval depths to evaluate
which wells would be capable of detecting light immiscibles. Table 12 lists
those wells capable of detecting light immiscibles with a "Yes." The term
"Possible" was used as screen and water levels may vary from 1 to 2.0 feet,
and these wells may be capable of detecting floaters during fluctuations in
water levels. These wells have also been plotted on Figure 24, which shows
the apparent petroleum thickness as calculated by Texaco on November 5,
1985. This was the most recent petroleum thickness map available to the
Task Force.
It should be noted that numerous wells measured on November 5, 1985
displayed the presence of light immiscibles at less than 0.5 feet. These wells
include: SS-24, 0.48'; SS-11, 0.44'; SS-23, 0.15'; SS-45, 0.41'; SS-47, 0.49'; SS-52,
118

-------
IN ItRCt P'OH
SVSlt M
TEXACO PROPERTY *esi
 BOUNDARY	/ is??
BHiOGt
Appro ii TO 11 LtXOt.nn O'
CiO| Ho">
> * fo I lrt o I if ' '95 ?
PREC iP a ACCI L
BLOA- DOWH POND
tic*
CC 11
\ \ X C U l VI
nlHClP'OB
LAST
19 T2
SPARC
STOHWI PONO
o o o
J YV BAROME TRlC
lagoon
ll-IOI 
STORM
MAT  R
su rcc
PONO
t\ It
t\ 
-^PCS co*f
SETTLING
POND
;n
L ANO
FdMW
AREA
FAR
Ct NT
i i r. i n o
iCASt O TO
GREAT iAftS
CARBON CORP
>'
MAIN PROCESS AREA
OFF ICt
MunilOf We* I
I'f rho'Qe Wei I
Kercwery Well
TRUCK
MAIN T E NANC f
plant nccovt ry a
storage yard
loading
Seep l.ocniion
ft Number
AREA
ROAD OIL
TANK FARM
	 POpe'fy DoundO'y
ft A>ilt .hlch Or* copobla o'
de Itc ll ng light phOM I mm I 
oiqnnici bated o" CDmpliJi
mid o11
C*Z3
^ H?rj/ocoft>or Thlcknut, II*
FIGURE 24
Monitoring Wells Capable
of Delecting Light Phase
Immiscible Organics,
South Area
Teioco Refinery, Casper, Wyoming
Sou'CQ MorlHled l">i" r.round-oief Technology,
100 5 - l98i
11'j

-------
eval-B
0.15'; SS-5, 0.23'; SS-37, 0.26'; and SS-55, 0.14' (Groundwater Technology,
1983-1985). These wells and other wells often show fluctuations in oil
thickness with water level incrcasc/dccrcascs. This is discussed later in this
Section, under the Hydrocarbon Recovery System.
Figure 24 points out that wells do not exist north/northeast of the storm
surge ponds to detect light immisciblcs. It is interesting to note that wells
SS-4 and SS-5 have historically shown hydrocarbon accumulation up to 2.0
feet, even though their screened intervals do not intersect the average water
table. During the Task Force evaluation, 5.02 feet of hydrocarbon
accumulation was measured in well SS-4 (sec Task Force Field Data Sheets,
Appendix D). Oil was measured from 9.83 to 14.85 feet (screen at 8-13 feet
and measured total depth of 15.4' below ground surface), thus explaining
that this hydrocarbon accumulation may be attributed to a dense immiscible
phase rather than light. Regardless, the potcntiometric map previously
presented (Figure 17) would indicate that this area may be seeping into the
North Platte River. The lack of wells adjacent to SS-4 and SS-5 screened at
the water table or deeper precludes an evaluation of hydrocarbon
accumulation in this area. Additional areas which may lack wells to
evaluate accumulations of hydrocarbons include the areas north of SS-30
and SS-17, adjacent to SS-51 and between the east and west interceptor
ditches north of SS-52 (Figure 24).
Table 12 also presents those wells in the South Area which may be capable
of detecting a dense phase immiscible component. Criteria for these wells
included those whose screened interval was completed at approximately the
alluvium/unnamed middle member contact. The potential for dense phase
immisciblcs has not been investigated by Texaco, as their efforts have been
directed to the floating phase. As previously mentioned, the Task Force's
detection of hydrocarbons in well SS-4 indicates the presence of a dense
phase (i.e. 5.02 foot of hydrocarbons from 9.83 to 14.85' with a screened
interval from 8 to 13 feet and a total depth of 15.4 feet). The Task Force
also detected a dense phase at well SS-19, where 1.0 foot of hydrocarbons
were measured on the bottom of the well (see field data sheet for SS-19,
Appendix D). No other dense phases were detected by the Task Force in the
South Area. To date, no measurements or documentation exists from Texaco
for dense immiscible components. Those wells which may be capable of
detecting a dense phase are plotted on Figure 25. Based on the
hydrogeologic conditions in the South Area previously discussed, there are
two areas where the potential for an accumulation of dense immisciblcs
could exist. They include a bedrock erosional low presented previously in
Figure 7 and confirmed in Figure 16, and also a potentially abandoned
meander loop identified on those figures. The low and abandoned meander
loop are presented on Figure 25 for comparison to well locations. Although
these areas may be potentially conducive to dense immiscible accumulation,
other variables such as ground water flow directions and the alluvium/
unnamed middle member interface surface (i.e. local features) may also be
conducive.
For detecting dissolved constituents, it appears that numerous wells would
be suitable, although Texaco has not implemented such a ground-water
program at this time.
120

-------
IN T c RCCP TOW
SYS T  M
TEXACO PROPERTY wist
BOUNDARY
BR lOGt
PHtCif a ACC E L
HlO* 00 *'N POND
in I t HCC PTO S'5iI M
LAS I
19/2

SPAl
SlO N M PON 0
BAROMl TRfC
lagoon
u>
.. V *'*er
mm-
< i - toi ft
STORM
.flTCR
SURGE
PONl)
4% - * O
 PCS CO**
SET TUSG
RONO
II I' - I ' <91
WEST TANK FARM
V !..  \
J A N I
HHU
ARM
^CENI
t 1 ( I N I)
MAIM PROCESS ARE A^
LEASE l> 10
onC A T l AwE s
CARBON CORP
OFF ICE
I of Well
Uc r tu)/ (j e We 11
Approximate
Area of
Ml'COv?f y We I I
TRUCK
Bedrock Low maintenance
M to plant reco^rv a I
LOADING
Loronon
El Number
AREA
ROAD OIL
TANK FARM
STORAGE YAH IN
Possi ble
Abandoned Meonder
  f'r iijier ly Hourtflary
(*) Welt* Mch Oft copobU n'
dfif.llng riant  phott Imml
of'j'inlc* Mtert on compltH"
I ft 1 p t (Oil
FIGURE 25
son

Monitoring Wells Capoble of
Delecting Dense Phase
Immiscible Orgonlcs,
South Area
Te*aco Refinery, Casper, Wyoming
] 2 1

-------
eval-B
Only two wells, SS-13 and SS-22, have a screened interval within the
bedrock, although at this time no analytical data have been collected. Both
wells appear to have been completed in a sandy siltstone or silty sandstone
lens in the unnamed middle member. It should be noted that construction
details indicate that only well SS-13 may be completed to allow for a
discrete sample from the bedrock unit and this well is located in the
southeastern area far removed from the areas of hydrocarbon accumulation
(Appendix C). Further evaluation of the bedrock unit is recommended in
order to evaluate the potential for contaminant pathways and/or
contamination in this unit.
The horizontal locations of wells M-41, M-41a, M-42 and SS-9 all appear to
be appropriate for them to serve as background-wells for the South Area,
based on ground-water flow (Figure 17). Although M-42 is presented on this
Figure, no completion records or geologic logs were provided to the Task
Force.
Design specifications of the wells located within the South Area and
evaluated by the Task Force are presented briefly in Table 12 and arc
detailed on completion logs in Appendix C. Because of the large number of
wells in the South Area, only general construction practices and
inadequacies will be mentioned.
All wells were drilled with either rotary or hollow stem augers to the total
depth of the boring. The rotary drilling included the use of either
Hydrogel, air, water, or Johnson Revert (Appendix C). No details were
provided by Texaco on the chemical composition of the drilling fluids.
As indicated on Table 12, many of the wells were drilled to a total depth
(top of bedrock) which was several feet deeper than where the bottom of
the well was actually completed. In most cases the bottom of the boring was
either backfilled or gravel packed, and then the well was completed. As
was previously stated for the North Area, the backfilled or gravel packed
interval below the bottom of the well may act as a pathway for potential
migration of contaminants deeper in the aquifer. At least one well (SS-6)
contained a bentonite seal at the bottom of the hole to avoid vertical
migration of contamination (Appendix C).
As presented in Table 12, well construction materials vary from 2" and 4"
PVC to 4" Schedule 40 galvanized steel. The screen and in many cases the
perforated interval was constructed of saw, pre-cut galvanized (0.10
perforations) slots or stainless steel Johnson screen (0.02 to 0.1 slot) for the
4" galvanized wells or factory slotted PVC screen with variable slot size
from 0.02, 0.08, to 0.18 inches for the PVC wells. Screen lengths varied
from 3.0 to 22 feet (Table 12, Appendix C). The TEGD (EPA, 1986a) states
that the use of galvanized in conjunction with stainless steel may lead to
accelerated corrosion of the galvanized steel, which could cause failure of
wells during long term monitoring. The TEGD recommends that an
electrically isolating (dielectric) coupling be used when two dissimilar
metals are in direct contact.
Also, the use of PVC as a monitoring well material may present problems
when in contact with aqueous organic mixtures. Please refer to the
discussion on the adequacy of PVC well casing material for the North Area.
122

-------
eval-B
In all wells, the filter pack consisted primarily of a gravel pack material
(pea-gravel, 8-16 or 12-20 free silica sand), or in many cases, collapsed
formation material or backfill from drill cuttings. Texaco did not provide
a grain size analysis of the formation material which could have been used
to evaluate the adequacy of the screen slot size with either the natural
gravel pack or the introduced filter pack.
In most cases the gravel pack and/or backfill extended well beyond the
recommended 2.0 feet above the top of the screen. This recommended
interval ensures collection of discrete samples (TEGD, EPA, 1986a)
(Appendix C).
The use of bentonitc as.an annular sealant above the screen was noted in
numerous wells, although it was also common practice to backfill the
annular space above the gravel pack and/or top of screen with drill cuttings
to about 2-3 feet below ground surface. Overlying the gravel pack, a
cement surface seal (2:1 cement to water ratio) was installed. The use of
drill cuttings as backfill material may not be appropriate as contaminants
from the soils could migrate into the open interval. In addition, where a
bentonite annular seal is non-existent, the backfill and/or gravel pack could
provide a contaminant pathway from shallow to deep aquifer flow paths.
There were no data presented by Texaco on the type of well development
procedures which may have been utilized following well construction.
Data collected by the Task Force for turbidity from several South Area
wells indicate values exceeding those recommended by the TEGD (5 N.T.U.)
(EPA, 1986a). The values recorded by the Task Force include: SS-19, 90
N.T.U.; SS-7, 85 N.T.U.; and SS-49, 247 N.T.U. These high turbidity values
may be a result of screen slot size vs. gravel pack vs. formation material, or
may be a result of the natural introduction of silts and clays to the well.
The impact of such turbidity values should be evaluated by Texaco if a
ground-water quality sampling program is implemented in the future.
As a check on the construction diagrams and the measured vertical
placement of the screened intervals, the Task Force measured total depth
for comparison. A brief comparison showed that the Texaco boring logs for
wells SS-49, SS-4, SS-7, SS-34 and M-41A compared favorably with only
slight variances of 1 to 2 feet. These variances may be a result of
accumulations of sediment in the bottom of the well or errors in
measurements during well completion.
Past Analytical Performance (Central South Area) Studies of the water
quality in the South Area are limited to those performed by Texaco in
conjunction with the oil recovery project. Specifically, only an evaluation
of the excess water produced from the recovery wells exists. The first set
of ground-water analyses were collected in September 1982 at monitoring
wells M-41a (upgradient), SS-9 (upgradient), Ob-2, SS-1, SS-5 and #10 (not
utilized or presented on Table 12 by the Task Force). These wells are for
the most part completed with screens below the oil-water interface to
evaluate concentrations of dissolved constituents. As part of Texaco's
permit conditions to operate the oil recovery system, samples were collected
123

-------
cval-B
at the recovery wells on November 27, 1984 and again on May 14, 1985
(Groundwater Technology, 1983-1985). During these sampling events,
indicator parameters, inorganics and some metals were sampled for. The
only organic analysis for the alluvial aquifer in the South Area was for
effluent from the interceptor system flowing to the effluent ponds (WWC,
1983b). The next sampling event was performed by the Task Force in
August 1986, where five wells (SS-19, SS-49, SS-34, SS-4, .and M-41a) in the
central portion of the South Area were analyzed. Results verify the
presence of organics in the ground water. This docs not include the present
investigation currently ongoing in the southeastern portion of the property,
which is discussed later in this section.
The inorganic and indicator parameter analytical results for samples
collected from wells M-41a, well SS-9, well Ob-2, well SS-1, well SS-5 and
well #10 arc presented in Table 13 and their locations can be found on
Figure 15.
These data show elevated TOC and chlorides when compared to background.
The metals analysis did not show any elevated constituents. As was
previously mentioned, Texaco maintains that the organic data listed in
Table 14 for the inflow to Excess Effluent Ponds is representative of the
alluvial ground water as it originates in the interceptor ditches. These data
show several organics detected which may exist in light and/or dense
immiscible phases (dependent upon concentrations) and/or dissolved in
ground water when compared to the physical characteristics of refinery
wastes outlined previously in Table 5.
The ground-water data collected in November 1984 was for effluent being
pumped from recovery wells RW-1, RW-2, RW-3, RW-5 and RW-6
(Groundwater Technology, 1983-1985). These data were evaluated to
characterize the quality of the water being discharged to recharge wells as
part of the oil recovery system. These wells ( RW-1, RW-2, RW-3, RW-5 and
RW-6) were again sampled in May 1985 for similar constituents which
include indicator parameters, some inorganics and several heavy metals. As
previously mentioned, no organics were sampled for. Analytical results arc
presented in the Fifth and Seventh Quarterly Reports for the Oil Recovery
System (Groundwater Technology, 1983-1985). Table 15 lists those
parameters which cither appear to be elevated or have been identified as
indicator parameters at the facility. These results indicate variable water
quality with sulfate and chromium concentrations being consistently
elevated and above the applicable criteria. It should be noted that sulfates
may be a function of variable ground-water quality in the shallow aquifer
and/or biodegradation of sulfides, as background sample results in Table 13
show elevated sulfates. It is probable that the waste constituents of concern
in the South Area are organics, for which there is a lack of data.
The Task Force samples collected in August 1986 were analyzed for organics
at wells SS-19, SS-49, SS-34, SS-4 and M-41A. These results are discussed in
detail later in this report. In summary, numerous organics including
benzene, ethylbenzene, naphthalene, toluene, total xylenes and other
base/neutral organics were detected in various concentrations. The
upgradient well M-41A did not contain any organics. It is worth noting that
at well SS-4, adjacent to SS-5, several other organics were detected which
124

-------
Table 13 Water Quality Data, Casper Texaco Refinery (September 1902).
Constituent
to
cn
Organic Species
Biochemical Oxygen Demand (mq/1)
Chemical Oxygen Oemand (mg/1)
Oil and Grease (mg/1)
Phenols (mg/1)
Total Organic Carbon (mg/l)
Field Parameters
ptl (std. units)
Spec. Cond. (umhos 3 25*CJ
Temperature (*C)
Major Inorganic Species
Total Otssolved Solids (mg/l)
Sodium (mg/l)
Potassium (mg/l)
Calcium (mq/1)
Magnesium (mg/l)
Bicarbonate (mg/l)
Sulfate (mg/l)
Chloride (mg/l)
Hlnor Inorganic Species
Arsenic, Total (mg/l)
Barium, Total (mg/l)
Doron, Total (mq/1)
Cadmium, Total (mg/l)
Chromium, Total (mg/l)
Chromium, Dissolved (mg/l)
Copper, Total (mg/l)
Cyanide, Total (mg/i)
Fluoride, Total (mg/I)
Iron, Total (mg/l)
Lead, Total (mg/l)
Manganese, Total (mq/1J
Hercury, Total (mg/l)
Nitrogen, Ammonia (mg/l as 11)
nitrogen, Hitrate (mg/1 as N)
Nitrogen, Mi trite (mg/l as M)
Selenium, Total (mg/l)
Silver, Total (mg/l)
Sul fide (mg/ 1)
Uranium, Total (mq/1)
Zinc, Tota1 (mg/l)
Well H-4IA
Well SS-9
Well 0b-2
Well SS-I
Well SS-5
20
23
26
H
23
43
2
75
3
199
2.1
1.0
1.9
1.2
54.2
-0.01
-0.01
-0.01
-0.01
0.10
29.2
21.0
61.9
34,6
50.5
7.1
7.3
7.2
7.5
6.9
2030
1380
1490
2110
1490
10
19
21
23
22
2526
1400
1323
1817
1145
210
128
122
373
202
2?
10
07
49
39
261
132
172
116
120
185
105
105
105
63
540
400
000
700
800
1430
650
363
315
8
32
17
72
445
255
-0.001
-0.001
-0.001
-0.001
-0.001
-0.10
-0.10
-0.10
-0.10
-0.10
0.92
0.51
0.74
0.51
0.42
-0.002
-0.002
-0.002
-0.002
-0.002
-0.01
-0.01
-0.01
-0.01
-0.01
-0.01
-0.01
-0.01
-0.01
-0.01
0.01
-0.01
-0.01
-0.01
-0.01
-0.02
-0.02
-0.02
-0.02
-0.02
0.27
0.40
0.30
0.45
0.27
0.04
0.03
0.04
0.04
0.29
-0.05
-0.05
-0.05
-0.05
-0.05
0.18
0.05
1.06
0.70
2.46
-0.0002
-0.0002
-0.0002
-0.0002
-0.0002
-0.05
-0.05
0.05
0.27
3.3
0.40
0.22
0.10
0. 15
0.24
0.035
0.002
0.001
-0.001
0.005
-0.001
-0.001
-0.001
-0.001
-0.001
-0.01
-0.01
-0.01
-0.01
-0.01
-0.10
-0.10
-0.10
-0. 10
-0.10
0.028
0.007
0.004
0.002
0.001
1.043
1.191
1.329
0.603
1.550
well flO
32
127
 0.4
0.10
46.2
963
65
64
164
01
1020
12
56
-0.001
-0. 10
0.54
-0.002
-0.01
-0.01
-0.01
-0.02
0.40
0.09
-0.05
1.08
-0.0002
4.0
0.47
0.040
-0.001
-0.01
-0.10
0.001
-0.005
Hole: - means less than value shown
Snnrnp; wwo. 19R3h

-------
Table 14 TOX and Priority Pollutant Data for the Excess Service Water Effluent Ponds, Casper Texaco Refinery
(October 1982).
Consti tuent
Inflow to Excess
Effluent Ponds
Chlorinated Hydrocarbons
(a)
Excess
Effluent
Pond #1
Excess
Eff1uent
Pond n
TOX (ug/1 as CI)
--
41
63
oC~ BHC (Benzene Hexachloride) (ug/1)
-0.001
-0.001
-0.001
Endosulfan Sulfate (ug/1)
3.5
-0.03
-0.03
1,1,1 - Trichloroethane (ug/1)
3
-2
-2
Unchlorinated Hydrocarbons^



Methyl Phenol (2 Isomers) (ug/1)
-50
-50
-50
Dimethyl Phenol (2 isomers) (ug/1)
-50
-50
-50
Methyl Ethy1 Phenol (2 isomers) (ug/1)
-50
-50
-50
Acetone (ug/1)
25
-5
-5
2,2,5 - Trimethylhexane (ug/1)
20
-5
-5
Dimethyl Hexane (ug/1)
24
-5
-5
Methyl Octene (ug/1)
31
-5
-5
Methyl Cyclohexane (ug/1)
53
-5
-5
Trimethyl Cyclopentane (ug.l)
9
-5
-5
Ethyl Methyl Cyclopentane (ug/1)
6
-5
-5
Methyl Naphthalene (ug/1)
150
-10
-10
Dimethyl Naphthalene (ug/1)
530
-10
-10
Trimethyl Naphthalene (ug/1)
370
-10
-10
Methyl Phenanthrene (ug/1)
97
-10
-10
Hydrocarbons Cj6 - Cig (ug/1)
180
-10
-10
Naphthalene (ug/1)
-10
-10
-10
Toluene (ug/1)
-2
-2
-2
Chrysene (ug/1)
27
-10
-10
Fluorene (ug/1)
11
-10
-10
Phenanthrene (ug/1)
67
-10
-10
Pyrene (ug/1)
61
-10
-10
^a) Priority pollutants not listed on the table were not dr-tectetf in the samples.
^nii rnn 	1 OP^ih
Excess
Eff1uent
Pond #5
49
0.12
-0.03
-2
-50
-50
-50
88
-5
-5
-5
-5
-5
-5
-10
-10
-10
-10
-10
-10
-2
-10
rio
-10
-10

-------
tab- j
slh
Table 15
Surmary of Refinery- Related Constituents
Recovery Ucll Samples - South Area
Parameters
Sulfate
Chloride
Phenol
Chromiun(T)
Lead (T)
TOC
OiI & Grease
pH (su)
Conduct!vity
(mhos/cm)
Applicable RU-1
Cri teria 11/27/84
RU-1
5/14/85
250 1
250 1
NA
0.05*
0.05*
NA
NA
NA
NA
8
24
0.16
0.10
ND(0.05)
32
365(oiI)
7.1
936
24
24
0.11
0.08
NO (0.05)
23
0.7
7.0
1090
RU-2
11/27/84
1020
26
0.04
4.0
6.4
1600
RU-2
5/14/85
1030
31
0.10
0.17	0.20
NO(0.05) NO(0.05)
ND(I.O)
7.65
2180
RU-3
11/27/84
2840
110
1.5
0.21
0.17
62
1091.0
7.5
4360
RU-3
5/14/85
1960
84
0.99
0.23
HD(0.05)
29
1.4
7.2
3750
RW-5	RU-5
11/27/84 5/14/85
RU-6
11/27/84
RU-6
5/14/85
440
38
0.08
0.08
ND(0.05)
18
22.8
7.0
1260
550
57
0.11
0.12
ND(0.05)
19
77.8
7.35
1660
760
32
0.10
0.14
ND(0.05)
129
3.58
7.2
1710
900
30
0.11
0.19
ND(0.05)
10
0.4
7.0
1920
Secondary Drinking Uater Standards 40 CFR 143.3.
*2
Primary Drinking Uater Standards 40 CFR 265 App III.
Sources: Groundwater Technology, 1983-1985

-------
eval-B
are indicative of a dense immiscible organic phase. These constituents
include chrysenc, fluorcne, fluoranthene, pyrcnc and phenanthrcnc. This
supports the previous statement that dense immiscible organics arc of
concern at wells SS-4, SS-5, and possibly in other areas at the site.
Based on the past analytical performance for the South Area, it is apparent
that Texaco has only been evaluating the extent of floating product, as a
ground-water quality evaluation for both dissolved constituents and dense
phase organics has not been undertaken.
Southeast Corner As previously mentioned, the southeastern corner of the
refinery property is currently subject to an investigation of the extent of
ground-water contamination in this area (WWC, 1987b). Approximately 13
monitoring wells have been included in this investigation (Figure 15). Of
the 13 wells, 8 were installed in late 1986 and 1987 as a result of the Task
Force evaluation and will not be discussed in detail. These eight wells
include SS-56 through SS-63 (see Figure 15). The subsequent discussion
refers to the five original wells.
The vertical placement of the screened interval in most wells is completed
in the alluvium with emphasis on detecting light immiscible phases. In the
past, floating phases have been detected in well SS-15. Monitoring well SS-
13 has been screened within the unnamed middle member.
Based on the refinery waste constituents (Table 5), the monitoring wells in
this area should be capable of detecting light and dense immisciblcs and
also dissolved constituents. Based on Table 12 and Figure 24, none of the
five wells have screened intervals capable of detecting light phases (SS-6
and 7, SS-13 - 15). As was previously presented in Figure 18, the ground-
water flow direction appears to be northeast to cast, ajthough in the vicinity
of well SS-15, the gradient appears to be fairly flat and probably to the
cast. According to Table 12, SS-14 docs not have a screened interval which
intersects the water table. At this time no wells exist at the southeastern
property boundary (Figure 24) capable of monitoring for light immisciblcs
potentially migrating off the Texaco property. The presence of light
immiscibles detected in well SS-15 (0.1 feet) indicates the need for
additional wells located to the east/southeast to evaluate the presence of a
floating phase.
Table 12 also presents those wells which could detect a dense immiscible
component. As previously mentioned, these wells would have to contain a
screened interval completed at the alluvium/unnamed middle member
interface.
Based on these criteria, only one well, SS-15, may be capable of detecting a
dense immiscible phase if measured and/or sampled for (Figure 25). Well
SS-13, completed in the unnamed middle member, may be capable of
detecting a dense phase, if migration from the alluvium to the top of the
unnamed member has occurred. It is interesting to note in this area,
especially at well SS-7 and SS-14, that the erosional subsurface of the
bedrock is deep, compared to adjacent wells. This feature can be seen on
the bedrock surface map presented as Figure 16. It is possible that the
128

-------
eval-B
bedrock surface could control contaminant migration and ground-water
flow. The potcntiomctric map constructed by the Task Force (Figure 18)
appears to mimic the bedrock surface, especially near well SS-13.
For detecting dissolved constituents, it appears that several of the wells
would be capable, as several dissolved contaminants were detected in the
wells, unrelated to light phase immiscibles (i.e., SS-7 and SS-14). At this
time, the monitoring wells completed at the eastern boundary (SS-7 and SS-
14) and along the southern boundary (SS-13) have shown some organics
contamination. No wells have been installed outside of the Texaco property
to evaluate the extent and/or contaminant concentrations. Analytical
results are discussed in further detail later in this section, under past
analytical performance.
Wells SS-6 and M-41A would appear to be located appropriately to act as
upgradicnt wells. However, the ground-water flow conditions as they relate
to well M-4 1 A and the southeastern corner should be investigated further,
possibly by the installation of additional piezometers.
Design specifications of the wells located within the southeastern area are
presented in Table 12 and arc detailed on completion logs presented in
Appendix C. The new wells SS-56 through SS-63 arc included in this Tabic
and Appendix as information on well specifications was available to the
Task Force at the time of this writing.
The construction of wells SS-6, SS-7, SS-13, SS-14 and SS-15 is similar to the
design specifications previously discussed for the wells in the central
portion of the South Area (see previous discussion). Therefore the
deficiencies in construction previously presented also pertain here.
Past Analytical Performance (Southeast Corner) The sampling of
monitoring wells in this area began with the detection of benzene,
ethylbenzene, total xylenes and naphthalene at well SS-7 by the Task Force
evaluation performed in August 1986. Since August 1986, Texaco collected
samples in October 1986 for verification of the Task Force results, and in
December initiated a drilling program and sampling schedule to investigate
this contamination.
Potential sources as identified by Texaco may include "the storage tanks and
pipe lines in the East Tank Farm, numerous other (non Texaco) hydrocarbon
pipelines in the area and other (non Texaco) storage tanks near the area of
investigation" (WWC, 1987b). No further details were provided.
It appears that Texaco has only analyzed for selected organic compounds
(benzene, ethylbenzene, toluene, xylene, and naphthalene) in the
southeastern area. Texaco has plotted concentrations for the October 1986
sampling event, which are presented in Figure 26.
As can be seen from Figure 26, contamination has been detected consistently
along the eastern property boundary (SS-7 and SS-14) and southeastern
corner (SS-15), with the highest concentrations found in SS-15 (note that this
well has contained accumulations of hydrocarbon in the past).
129

-------
IrEXACO PROPERTY BOUNDARY

y





-------
In summary, it appears that the potential for migration of contamination
off-site to the cast is high, as wells along the property boundary have
elevated concentrations of several organics and the potcntiomctric map
(Figure 18) indicates an eastern/northeastern component of flow. It should
be noted that the ground-water flow is not completely understood at this
time. As previously mentioned, additional data is required to completely
understand the conditions in this area.
c. Adequacy of Ground-water Monitoring System (South Area)
The facility-wide monitoring system was designed and constructed to detect
and evaluate the extent of accumulations of floating hydrocarbons
throughout the south property. As a result, the full extent of contamination
in the South Area has not been defined, specifically the presence of
dissolved and/or dense phase immiscible organics. It appears that a detailed
evaluation of the rate and extent of contamination and oversight of the
ground water corrective action system will fall under RCRA as the
potential for releases from SWMUs has been documented in an RFI (A.T.
Kearney, 1986).
Of importance is the identification and abatement of all potential sources
of ground-water contamination in the South Area which may be continuing
to release contaminants into the ground water in the form of light and
dense phase immisciblcs and other dissolved organic and inorganic
contaminants.
The monitoring well network overall appears adequate to detect and
evaluate the presence of the floating hydrocarbons in the South Area,
although as was pointed out previously, several areas north of the identified
plume (Figure 24) appear to lack wells constructed to monitor for light
immisciblcs. These wells would aid in detecting floating hydrocarbons
migrating towards the river prior to any actual seepage along the south
bank of the North Platte River.
Although numerous wells may be adequate to detect dense phase immiscible
components, Texaco has not initiated a program to evaluate the potential
for such accumulations. It was documented during the Task Force
investigation that dense phase immiscible do exist at the site as was
evidenced by a one foot sinking oil phase at the bottom of well SS-19. As
was previously mentioned, several areas at the site appear to be conducive
for the accumulation of dense phase immisciblcs (e.g., Figure 25 presents
approximate locations of bedrock lows and abandoned meander loop
channels of the North Platte River).
The significance of dissolved organic contamination in the ground water
has not been addressed except in the southeastern corner of the South Area.
Wells in this area have detected benzene, ethyl benzene, toluene, total
xylenes and naphthalene.
The southeastern area lacks the number of wells required to define the full
extent of contamination. This is apparent as wells located along the eastern
and southern boundary have detected organic contaminants, and based on
ground-water flow directions, appear to be migrating off-site to the
east/northeast.
131

-------
eval-B
Several construction problems also exist with the monitoring well network
as previously mentioned. It is difficult to asses the impact of these
problems at present as Texaco has concentrated only on monitoring
accumulations of floating hydrocarbons. When a ground-water quality
assessment of the South Area is undertaken, the adequacy of each well must
be evaluated prior to collecting and analyzing ground-water samples. It
may be appropriate, through process of elimination, to choose wells in the
South Area which meet the technical requirements of RCRA monitoring
wells as set forth in the TEGD (EPA, 1986a) and at the same time arc
placed vertically and horizontally such that the full extent of contaminant
migration can be evaluated.
d. Hydrocarbon Recovery System
In response to the problem of floating hydrocarbons, two remedial action
technologies have been employed at the site. The first remedial action
includes the interception of ground water along the south bank of the North
Platte River via two interceptor ditches, and the second, involves the
recovery of floating hydrocarbons by pumping the aquifer. The following
is a discussion of each remedial action technology.
Interceptor Ditch Svstem The original interceptor ditch was installed in
1957 to address oil seepage into the North Platte River (i.e. seeps #2 and #3,
Figure 15). In addition to these open ditches, several pits were installed to
intercept floating hydrocarbons. Both the trenches and pits reportedly
recovered high volumes of hydrocarbon wastes (WWC, 1982c). There arc no
data on the maintenance and/or performance of these trenches from 1957 to
1972, when they were replaced. According to Texaco, a "Clay Barrier" was
also constructed in 1957 (Figure 15). No construction details were provided,
except that the clay was locally derived material with hydraulic
conductivities ranging from 10"* to 10"^ cm/sec (WWC, 1982a). Based on the
potcntiometric map for the South Area (Figure 17), it appears that this clay
barrier may still exist (i.e., flow of ground water around clay barrier and
east trench).
The present interceptor system (east and west, Figure 15) was constructed in
1972 and 1973 to replace the original open trenches. This new system
consisted of a closed system. The east and west trenches were constructed
using two 24-inch perforated culverts, stacked on top of each other,
approximately 495 and 643 feet long, respectively. Each ditch, following
insertion of culverts, was backfilled with one inch gravel, a minimum of 2
feet on each side of the culvert (WWC, 1982c). Based on the regulatory
definition of a SWMU, both trenches meet this definition as previously
discussed.
At the east end of the west trench and the west end of the east trench, a 17-
foot deep concrete sump was installed with a 300 gpm pump located in each.
Water levels in the trench were controlled by an adjustable weir located in
each sump. Water levels in the trench were maintained approximately 0.6'
below the river in order to reverse flow and have the trenches act as a
ground-water sink. From the sumps, the hydrocarbons and ground water are
132

-------
eval-B
diverted through a scries of tanks used to separate the oil phase and store
water prior to discharge to the service water ditch svstem (Figure 15) (WWC,
1982c).
In 1982, Texaco performed a spot check on the velocity of flow and also
installed 4 wells, SS-36 and SS-37 (West System) and SS-34 and SS-35 (East
System) to evaluate the cone of depression caused by the trenches. The flow
tests performed by Texaco indicated that there was flow in the western
system, but little to no flow in the eastern system. This would indicate that
the eastern system may not operate properly during certain times of the
year. The water level measurements taken in 1982 at the wells adjacent to
the trenches (SS-34, SS-35, SS-36, SS-37) show that the trench systems arc in
fact acting as ground-water sinks (WWC, 1982c). Since 1982, no data exist
on maintenance or performance monitoring of the interceptor system. Based
on the location of the east and west system, and the approximate location of
the "clay barrier" (Figure 15), it appears that approximately 950 feet of the
south bank of the North Platte River could be subject to undetected
seepage. This seems highly likely as substantial accumulations of
hydrocarbons were detected over time by Texaco in wells SS-4 and SS-5 and
by the Task Force in August 1986 in well SS-4 (5.02 feet). This suggests
that floating hydrocarbons and possibly dense phase immiscibles may be
migrating to the north and towards the river in this area.
The analytical results collected by the Task Force in August 1986 at well
SS-34 showed concentrations of benzene at 38 ug/1, indicating that a
dissolved organic fraction may be migrating past the cast interceptor trench.
In addition the Task Force results for well SS-4 indicate that organic
contamination exists in this well in elevated concentrations, thus increasing
the potential for discharge to the river as a trench or barrier docs not exist
in this area. As previously mentioned, the results seem to indicate that
contamination in wells SS-4 and SS-34 may be in the form of a dense
immiscible phase (i.e. presence of chryscnc, fluorcne, fluoranthene etc.) or
dissolved organics respectively. This indicates the trench system may not be
capable of intercepting dense phase organics.
Because detailed construction design specifications were not available, it
could not be determined whether the interceptor trenches would in fact
intercept dense immiscibles migrating towards the river. If in fact the
trenches could intercept dense phases, the sumps (based on details provided
by Texaco) do not appear capable of pumping dense phase hydrocarbons
collected at the bottom of the sump (WWC, 1982c). Although the interceptor
system may drain dissolved organic constituents within the ground water to
the sump, the treatment process (oil/water separation) would not adequately
treat dissolved constituents. The water routed through the separation tanks
would in fact end up in the service water system ditch, and would be
returned to the ground water through seepage from the bottom of the ponds
(i.e. service water ditches and ponds) (A.T. Kearney, 1986).
Oil Recovery Svstem Texaco installed a series of hydrocarbon recovery
wells in August, 1983 (RW-1 through RW-4). In June 1984, two additional
recovery wells (RW-5 and RW-6) were installed. The approximate locations
of these recovery wells is presented on Figure 15.
133

-------
eval-B
Each recovery well is fitted with two pumps, one which is situated at the
ground-water interface to pump product, and the other pump utilized to
depress the water table and induce flow of floating hydrocarbons toward
the recovery well(s). The water produced from the pump which lowers the
water table is injected without treatment down a series of recharge wells
assigned specifically for each recovery well, except for RW-I which
discharges to the PCS coke settling pond. These recharge wells are also
presented on Figure 15.
The design of the oil recovery system was based on the identified extent of
floating phase, and the characteristics of the aquifer (WWC, 1983c). Figure
27 presents the theory originally used for the installation of the first four
recovery wells in 1983. Figures 28 and 29 present as-built drawings for
recovery wells RW-1 through RW-4. Design specifications for RW-5 and
RW-6 installed in 1984 were unavailable. An as-built diagram for the
recharge wells installed in 1983 is presented as Figure 30.
The design and operation of the oil recovery system as of January 1986,
which includes all new components (recovery and recharge wells), is
discussed below. Table 16 presents specifications for the recovery system in
operation as of January 1986.
The operation of the recovery system has been somewhat intermittent since
August of 1983 due to 1) severe weather during the winter months which
forced shutdown of all recovery wells, except RW-1; and 2) in September,
1986, .when the price of oil dropped, so did the reason for operating the
recovery system, except RW-1. This was because the contractor operating
the system derived their profits from the sale of recovered product (A.T.
Kearney, 1986).
The reason for continued operation of RW-1 was that sometimes during the
shutdown of this recovery well, oil seeps were noted along the river, beyond
the interceptor system (probably the clay barrier). Since the system's
operations from August 1983 to November 30, 1985, approximately 25,007
barrels of hydrocarbon have been recovered from this system (Groundwater
Technology, 1983-1985). The breakdown for each individual well is as
follows:
RW-1 9.0 barrels (no product removed since 1983; RW-1 still operating)
RW-2 11,307.68 barrels
RW-3 9,663.35 barrels
RW-4 587.58 barrels (shutdown April 1984)
RW-5 1,569.36 barrels
RW-6 1.870.85 barrels
Total 25,007.82 barrels
The Task Force reviewed nine quarterly reports from the period August
1983 to November 1985 (Groundwater Technology, 1983-1985) in order to
evaluate the effectiveness of the oil recovery program in reducing the
accumulations of hydrocarbons across the central portion of the South Area.
During each quarter, Texaco constructed apparent petroleum thickness maps
and ground-water contour maps to evaluate the effects of pumping. Figures
31 through 40 present apparent petroleum thicknesses for each quarter. As
134

-------
('.imwHDWAiun
no ir
U1
TXACO INC.
PROJECT
LOCATION  CASfGrt, wr
MAIMTCHAifCC ,
*.amf *ccovc*r
nortACt r*nu
on
OftAWirfC HO.
A proposed recovery- wlll
X PROPOSED OQ$RVATICXl WLLL
OOO RECHARGE AREA
	> FLOV. LINES
f 1 AOOtFER RECHARGE
GRAPHIC SCALE
Figure 27
Source: wwc, 1983C

-------
ELECTRICAL outlets
FOR PUMPS
EXPLOSION proof
ELECTRICAL CONTROL PANEL
FOR PUMPS ANO PR08ES
electrical outlets-
FOR PROOUCT -WATER
A.N 0 PROOUC
PROSES
AIR
ELECTRIC LINE TO Tank FULL PROeE
PROOUCT
DISCHARGE
HOSE
PROOUCT FLOW METER
,STEEL PIPE
/TO PRODUCT
/STORAGE TANK
GROUND WATER-
DISCHARGE HOSE
4" PVC PIPE TO 
RECHARGE WELLS
2.3
jCL
II
ac5i
-------
ELECTRICAL OUTLETS
FOR PUMPS
EXPLOSION proof electrical
CONTROL PANEL FOR P'JMPS
A no PROBES
ELECTRICAL OUTLETS
FOR PROOUCT-v/ATER
AnO PROOuCT-AiR
PROBES -	
ELECTRIC LINE TO TA.'JK FULL PR03E
PRODUCT OISC^ARGE HQS
GSOUNO WATER
OlSCHARGc hCSE
PSOOUCT FLOW metes
,-STliL PlP TO
4" PVC PIPE TO
RECMARGc WELLS
z.z
GROUND SURFACE i.
9 E N T 0 NIT  SEAL
16 STEEL, 10 GAGE CASING
20* -
16 STEEL JOHNSON. IRRIGATOR
SCSEEN WITH 0.120 SLOT SIZE
25 -
50' -
Figure 29
as-built diagram of recovery wells
RW-2, RW-3.AND RV/-4, CASPER TEXACO
refinery
Source: Groundwater Technology, 1983-1985

-------
Girt VALVE
2" PVC SCHEDULE <0
0R0? PIPE \
4 PVC SCHEDULE 40
PIPE FROM RECOVERY WELL
2ENT0NITE SEAL
4 1/2 PVC SCMEOULE 40 CASING
10* -
15* -
20' -
41/2" PVC SCREEN WITH .032 SLOTS
25" -
ORILL CUTTINGS
30' -
Figure 30
AS-8UILT DIAGRAM OF RECHARGE WELLS SS-46
1-1,1-2,1-3,1-4,1-5,1-6,1-7,1-8 CASPER
TEXACO REFINERY
Source: Groundwater Technology, 1983-1985
138

-------
tab- i
sth
Recovery Well
RW-1
RW-2
RW-3
RW-5, RW-6
Table 16
Oil Recovery System Design Specifications
Recovery Well - Injection (Recharge) Well
Series
Receiving Injection Wells
PCS Coke Settling Pond
I -1, 1-2, 1-3, 1-9 and I-10
1-4, 1-5 and SS-46
I -11 through 1-19 and P-l
Note: 1) RW-4 was removed from service in April 1984.
2)	Documentation as to what recovery well discharged to
recharge wells P-2, P-3, 1-20 and 1-25 through 1-29
was not available.
3)	Recharge Gallery I -11 through 1-19 abandoned in May 1985.
Rec'overv Well
RW-1
RW-2
RW-3
RW-5
RW-6
Operational Pumping Rates
Maximum Pumping Kate
(qpd)
14,400
259,200
259,200
230,400
230,400
Average Pumping Rate
(qpd)
7,200
216,000
216,000
64,800
129,600
Recharge Wei 1s/Capacitv to Receive
Recharge Well
1-1, 1-2, 1-3, 1-9, 1-10
1-4, 1-5, SS-46
I-11 through I-19 and P-2
Maximum Receiving
Rate (qpd)
51,840
86,400
46,080
Average Receiving
Rate (qpd)
43,200
72,000
19,440
Source: A.T. Kearney, 1986
139

-------
Fipure 31
APPARENT
PETROLEUM THICKNESS
CONTOUR MAP
GltC'JNOMMTCn
rtCHiotoov
INTACCMO* StSTCm wCS*
"0"r" ^rrc 
sbcctoa
Vriitt" tut
l&coom
ff
poj
a ow Do-**
v *3*0
troMM
STOAki AfO
SLACC POO
0.5
K1 CO'C
3C T TlinC M3m0  SS->4
<0
WEST TANK
cast
tank
FARM
3-5
CENTRAL TA hk
^0
C * i A T l*kCS
ClflttON COftf
PROCESS ARA
MAIN
LEGEND
0.5
TEXACO INC
CASPER, WT
PROJECT
MAlNrtNAJ
-------
BS
IGiiOUmnvAlEH
I 11 CurOiOGV  ;'
H i . .;
	o---o-~\ ^
 I t imI(RC(^IM {rSI(u wfjf - J	\
eo-occ
"OftrH
1
RiVfp
in rniccMO*
Jt(M (*5T
miciP
 I  I'M   7
STOA
1l*GC
*0*0
K1 CO 12-9*83
 MONITORING WELL
wCLC lOCMTlftCATtOH
f*.SS>6 . WCLL ID. NO.
0.0  APHRlHT ffT0LCOM
TmiOnCSS (im ffOI
~ RECOVER* WELL
OOO RECHARGE WELLS
N f r
Technology, 1983-1985

-------
;j|-rriaa!a'Sr .'
	-o- -  O' \
,|.| miHZirum srsitu wtj
t- * "
l Af.uO'J
UCf MO ,

J^ SIOhm
>C
5 T o*m aT(*
SU"Cf *OM>
L. >
ss-n
m con
it I ICING PGHO  S3-It
is.f
* 11-25
 
wSJ Tank Farm
it ii
TANK
Farm
CCrriRA
FfiR'
CBfA' LfS
C*SON COP
main process aiiea
 ss .ri
fRoC
UA inf N*mC(
^ t n I *i COv qt
JfO*CJ v ,
lO^D>'iC
hoaq oil
Tank Farm
 ii'lO
'!i
J; Figure 3 3
Mlil!	i
wM'
LEGEND
PROjCCT ! TCXACO IMC.
LOCATION : CASPCR, Wt
I
drawing mo  ; 4 0if - 20
MONITORING 0*TE  3-12-04
.1 1
 MONI TOTING 'WELL :
wCll iGomfiCAn   ,
 Sl-i4 WCLL 10. NO.
t
4PP4ft(MT rCTMOt
1IC'C3S (* ft
CO//TOUH I N TC rtVAj_ as SHOW" 'J fee T
Cm.Mlc SCALE
feet
A. recovery well
OOO RECKAHGE WELLS
Source: Ground'Water Technology, 1983-1085

-------
Figure 3 4
APPARENT PETROLEUM
THICKNESS MAP
Clit KlNOWAllll
TVCliw^ fV.Y
-o- - -o
ftAKCWC I *11
*\.A7y r
lni( <&st
**! j ig*
sl*
4.0
it r u i*c ro*o  ss '<
2.0
TANK
Farm
Cc*1 L*tJ
Af\t A
LEGEND
PROJECT 
TCXACO INC.
LOCATION
n. an i Mccovtf t
JIOAaCC
OAawING NO
mOmi TOP inC Oatj 9-3-84
MONIT OHiMC WELL
 III	T
 - PC TRCXll*l THIOMCSS
TRACE	*' rCCT
PxaCE ii RECOVERY WELLS
nccovcnr wcll
COlOuH IHlCAvlLS
'J S..0-.N* IN 11(1
OOO RCCiunce wells
onn PHA;r n RfnABf.r wfi  <
Source: Ground Water Technology, 1983-1985

-------
EE
GROUNDWATER
TCMfOtOCV 
II), , ss-l
i- imicrccpioa srsrcw wur
nO*Th
&aACmCT*iC ^OCOOh
^4rrr
Rivro
>vu  . ,
no*
|T0*
itiia
K1 coc	y
UriciHC ^0.0 *53.^
W[ST TANK FARM
Cast
[ AN K
:AAM
CtHTftAU^^JAWK FARM
0-S
OFflCt
C* T LA'CS
CihOOM CO"*
MAIN PROCESS A^EA
00-2 i
TRUCK
M A I M r
^V*I ACCOv [flf o
STOAaCC tio
LOACXNC
0*0 oil
ARC A
Fieure 35
APPARENT
PETROLEUM THICKNESS
CONTOUrt MAP
CflAPKiC 5CALC
11/ ft T
LEGEND
PROJECT  TfKACO tHC
LOCATION  CASPAR, V/t
OAAWIfJG NO  IQ.4011-26
MONITORING DATE  3-2-84
 MOMJTCflJMG WELL
wLL \t
-------
APPARENT PETROLEUM
THICKNESS MAP
GnouHOWAren
ltC'0
-------
Fin-urn 37
APPARENT PETROLEUM
THICKNESS MAP
0,1(1 KJNOWAM'.II
11 O
			O"
INl(NC(f10< JTJT(W wCJI
^4r,c 'vf
JtJUu |*lf
L-*op
1 s
>WI 1
}!0M
>0

res co-t
s( f rt inc pono  O
HCCMAtce G*LLf*r
Farm
0.5
G"C * T cAC S
PROJECT  rc*co inc.
location i CASftn. w*
OHAWING NO 1 lO-^ OH -4 4
MONITORING 0AT > 2-11-83
 MONiTOliNG WELL
wLC iK^TIflCAllOH 
t *.  SS -M -	10. NO.
I 70 - APPAHCnT Ft THOlCUU |H.l
2O0
4 CO
A RECOvCRY WELL
OOO RECHARGE WELLS
GOG PHASE li RECHARGE WELLS
CKAPiur: 3Cal
in r~ZT
Source: Ground Water Technology, 1983-1985

-------
mq
ULO
,iii it :i mii M
i>.	 <>
II MCI P iom inifM rn ^
Rivcr
wt$l TA nk Farm
MUAH0040)
^ M "
CA ST
fAMK
F ARM
tNlHAL TANK FARM
Or
yiln
Office
A I M IT MAX 7C
pianv ntcc*t*r a
JTOAaCC T*fn)
o*o otc
vani (ah
Figure 38
APPARENT PETROLEUM
THICKNESS MAP
PROJECT  TC * ACO MC.
LOCATION  CASPCR. wr
CLAWING NO.  I0-40H-50
MONITORING OATE  5/6/61
 MONITOOlMC WP.LC
wfLL IOCxTi/ICaTKX 
C*. ' Sl-Sft . VCLL 10. NO.
CDHTOUR INTERVALS
AS ShOwn-in FCC T
firmtp*1" f! round Wfltfsr Technology, 1983 1.985
C'IaVmiC 5C*Lt
 IN feci
-A. BCCOvEnr well
OOO hecharce wells

-------
jj.ii
is-j .
.			
,!- iHTCJtcCPfOA snrfu wCi
amocc
KARO'LTA

iT STfU CA1T
1VU 
!**< SICMu
K><0
JIOAu ifO<
Si*C fO0
KXO
:f^/ooo< 30^
res COC
icrriiMC roo*S3-<
U-ll
WEST TANK F-ARU
. ss-z*
-RfCMAKQC CALLt HY
(l-ll  1-fJ)
(A01HOONCD)
t AST
pAHM
CtNTftALSJ*MK FARM
MAIN
OFFICC
cf*r lakcs
CAABOH CONP
MAIN PlfOCCSS AtftA
IfKJCt
MAINTENANCE
rv*MT rttcovCnr a
Stdaacc "*r>o
LOAOtHC
flOAO OIL
Tank FaRu
CO Af-HlC jCALE
in reer
Figure 39
APPARENT PETROLEUM THICKNESS
DISTRIBUTION MAP
PROJECT  TXACO INC.
LOCATION ' C^SPtA, wr
CflAWIMG NO. ' 10-4011-62
MONITORING 0*TE >11-5-85
 MONITGfllNG WELL
wCLL lOCfiJIflCAtiCH 
tl.i 55 X . WCLL 10. HO.
JL RECOVERY WELL
OOO nccHAnce wells
OGO PHASE II RECHARGE WELLS
COuTOuA IN I f ft va l J
11 * nfw> 4u r rr 

-------
u
vo
 i. . 
	o	~ * \
-1.6	trlKu wtst - J	V
K1 CO-C
jcrtLiNC *oo  s*-4*
RfCKiKCC G4(.IC*Y
(i>ii  i-rjj
(abamDO'CO)
WCST
TANK
FARM
CAST
TANK
farm
NTRAI
Farm
TANK.
CAC4I LiKI
ciiC( taao
LOCATION
LO*CNNC
Figure 40
rnra Source: Ground Water Technology, 1983-1985 m ree
APPARENT PETROLEUM
THICKNESS MAP
TEXACO IMC.
CASPCR, WT
OAAWINC NO ' I0-0H-S6
UONI tqrihc o*TC  8-12-85
WOlllTOfllHC WELL
wLL 104J* * iflCATfCH 
( Sl.M - **- NO'
A. RECOVERY WELL
OOO RECHARGE WELLS
OOO PHASE II RECHARGE WELLS
COMtOu*
,f 4	IM f f f 1

-------
eval-B
can be seen from these figures, it appears that a reduction in the
hydrocarbon plume is occurring as a result of pumping, although the plume
dimensions seem to vary through time. This is evidenced by the presence of
hydrocarbon accumulation isolated at wells SS-4 and SS-5 during the May
quarterly measurement periods (Figures 35 and 38). This accumulation does
not appear to be within the influence of either the interceptor trenches or
recovery wells currently in place. Other isolated accumulations arc also
evident through time.
It is also interesting to observe the influence that the recharge wells/
galleries are having on the shape of the plume. For example, it appears that
recharge wells I-l, 1-2 and 1-3 and later 1-9 and I -10 could be pushing
accumulations of hydrocarbons farther north towards well SS-37 and the
northern bank of the Barometric Lagoon (Figures 35 and 37). In addition,
the recharge gallery 1-11 through 1-19 activated in September of 1984
(Figure 34) appeared to have controlled some lateral migration of
hydrocarbons by hydraulic control (reversal in gradients). When this gallery
was abandoned in May 1985 (Figure 38), the plume appears to have
migrated farther eastward. Without further monitoring, the effects of
adding and/or abandoning recharge wells on plume migration cannot be
evaluated.
An evaluation of decreasing accumulations in any one given well across the
site would be difficult, as the fluctuations appear to be sporadic and,
controlled by several variables including but not limited to, seasonal
fluctuations in water levels which may be attributed to rise and fall of the
North Platte River and operation and shutdown of both the recovery and
recharge wells.
Task Force conclusions on the oil recovery system are that after three years
of operation, there still appears to be an area trending northwest/southeast
adjacent to the cooling towers and service water ditch where substantial
accumulations of hydrocarbons arc present (2.0 - 3.0') (Figures 31 through
40). The overall dimensions of the plume appear to have decreased since
1983.
The treatment of the floating hydrocarbons in a series of tanks cannot be
evaluated as no data have been presented by Texaco on the effectiveness of
this process.
The ground water collected from the recovery wells (i.e. pumps used to
depress water table) is injected down a scries of recharge wells. The quality
of this water, re-injected into the uppermost aquifer, has been sampled
twice, but only included an analysis of indicator parameters and several
water quality constituents. These data were previously discussed and
presented in past analytical performance for the central South Area. Table
15 previously presented a summary of analytical results collected from the
recovery wells. No analysis for organics has ever been performed on the
ground water being re-injected into the aquifer. The only analysis for
organics in the alluvium was collected by the Task Force in August 1986 for
wells SS-4, SS-19, SS-49 and SS-34. The results may be indicative of the
ground-water quality being extracted from the recovery wells and re-
injected into the uppermost aquifer due to their locations in relation to the
150

-------
eval-B
recovery wells. The organics detected arc presented here for information on
the recharge water quality. A detailed discussion of the Task Force data is
included later in this report.
Table 17 presents the Task Force organic data which may be most
representative of the ground-water quality being rc-injcctcd into the aquifer
through the recharge wells. Wells SS-19 and SS-49 are probably the most
indicative of recharge water as they arc located closest to the recovery
wells. Wells SS-34, located north of the interceptor trench, and SS-4 (which
appeared to contain dense immiscible components) may be less
representative. The data (Table 17) show considerable concentrations of
benzene, ethyl benzene, toluene, naphthalene, and total xylenes. In addition,
as previously discussed and presented in Table 15. other inorganic
constituents may be present in the recharge ground water, such as total
chromium above the Interim Primary Drinking Water Standard (40 CFR 265
App III).
In addition to the recharge wells, the PCS coke settling pond and service
water return ditch are the receptors for skimmed water from recovery well
RW-1 and also from the interceptor trench system. As can be seen from
Table 17, the PCS Pond results indicate that contaminants were detected and
may be seeping back into the aquifer.
These data suggest that re-injcction of this ground water from recovery
wells may not be appropriate without prior treatment. In addition, both the
dissolved organic fraction and dense immiscible phases arc not addressed by
the current oil recovery system.
Evaluation of Hydrocarbon Recovery Svstem The hydrocarbon recovery
system currently in place at the Texaco south property can only be expected
to reduce the floating hydrocarbon phase but not entirely eliminate it.
According to Texaco, up to 50 percent of the hydrocarbons will remain
bound to sediments and will not flow to either the interceptor trenches or
recovery wells (WWC, 1982c).
The existing data indicate that a dissolved organic fraction and probably a
dense immiscible organic phase exist at the site. The extent of these types
of hydrocarbon contamination has not been defined and the current
recovery system (trenches and recovery wells) is not capable of extracting or
treating these contaminant plumes. In fact, with the re-injection of
dissolved organic contamination into the recharge wells, the recovery system
may be contributing more to the dissolved organic contamination.
It is possible that the recovery wells will increase contamination of ground
water by mixing of floating hydrocarbons with ground water (i.e. change in
gradients and pumping of product within the recovery well), thus causing
more contaminants to dissolve into the ground water and possibly migrate
and/or discharge to the North Platte River.
Specific conclusions and recommendations for the hydrocarbon recovery
system are as follows:
151

-------
tab-h
slh
SS-19
Benzene	2000
Acetone	ND
Ethylbenzene	170
Toluene	290
Total Xylenes	890
Anthracene	ND
Benzo(a)anthracene	ND
Chrysene	ND
Fluorene	ND
Fluoranthene	ND
Naphthalene	770
2-Hethyl-naphthalene	1800
4-Methylphenol	ND
2-4-Dimethylphenol	ND
Pyrene	ND
Phenanthrene	340
Table 17
Ground-Water Quality/Dissolved Fraction
Indicative of Recharge Water Quality
Ground Uater Task Force, August 1906 (ug/l)
SS-49	SS-34	SS-4	PCS Pond
6000 38	900	7.7
ND ND	ND	12
310 ND	41	HO
620 ND	44	ND
3000 ND	140	27
NO
NO
NO
NO
ND
2800
3200
210
500
NO
240
ND
NO
ND
ND
NO
NO
ND
ND
ND
ND
ND
480
860
1200
700
560
610
960
ND
ND
2100
6000
ND
33
68
ND
ND
ND
ND
ND
ND
120
59

-------
eval-B
o The oil recovery system (recovery and recharge wells) and the
interceptor trench system should work in conjunction with each
other. Texaco only reports quarterly on the operation of the oil
recovery system. Continued operation of these components should be
maintained.
Texaco should implement a performance monitoring program
for the interceptor trenches, which at a minimum should
include 1) an evaluation of grade control (Wagner, et al., 19S6)
to ensure that ponding in the trenches is not occurring; 2)
continued monitoring of water levels in wells SS-34, SS-35, the
east interceptor trench, wells SS-36, SS-37, the west interceptor
trench and the North Platte River to ensure the trench is
continuing to act as a ground-water sink. This is important as
it is probable that the oil recovery system (recovery and
recharge wells) plus seasonal variations in water levels will
alter the performance of the trench. In order for the trenches
to be effective, they must operate to account for these
variations. Texaco should consider additional wells south and
north of the trenches to evaluate gradients; 3) the
implementation of a monitoring program of wells installed
between the trenches and the North Platte River to ensure
that no contamination is migrating past the trenches. The
wells should be completed to monitor for floating
hydrocarbons, dissolved organics and dense immiscible phases;
4) A maintenance and operation program to inspect the
trenches to ensure proper operation. Inspections should
include an evaluation of the drains for chemical clogging
(biological slimes), excess siltation due to introduction of fines
and other mechanical failures associated with the pumps and
skimming devices in each sump.
o At this time, there is approximately 950 feet of shoreline along the
North Platte River where a trench or barrier docs not exist (Figure
15). This area is evidenced by the potcntiomctric contours plotted by
the Task Force in Figure 17 and appears to be a prominent
contaminant pathway for the discharge of hydrocarbons to the North
Platte River. This is further supported by the presence of
contamination in wells SS-4 and SS-5 in the form of a floating
and/or sinking phases. Based on the location of wells SS-4 and SS-5,
it appears that discharge of contaminants to the North Platte River
may be occurring, possibly on a seasonal basis.
It is recommended that Texaco evaluate the potential for
releases in this area to the North Platte River. This may
include the installation of additional wells between SS-4 and
recovery well RW-1 (Figure 15). As part of this evaluation,
the structural integrity of the clay barrier installed in 1957
(Figure 15) should be investigated in order to determine the
efficiency of this structure to control contaminant migration
(i.e. floating, dissolved and/or dense immiscibles). If the
potential for migration is high, which it appears to be in this
area, Texaco should consider the installation of a ground-
153

-------
eval-B
water control system in this area which may include French
drains or barrier walls, or possible expansion of the oil
recovery system (recovery wells). As part of this monitoring
and performance evaluation for the trenches, inspection for
seeps along the south bank of the North Platte River (entire
Texaco property) should be implemented so that immediate
detection of releases can be made. The inspection schedule
for seeps should take into account seasonal fluctuations in
water levels and river stages and operation and shutdown of
the hydrocarbon recovery system.
o It is apparent that the oil recovery system (recovery and recharge
wells) may be increasing contamination of the aquifer by injecting
untreated ground water back into the aquifer. As part of
performance monitoring, Texaco should sample the water being
recharged to the aquifer for organics. Based on these analyses,
Texaco should present a treatment method (if required) such as air
stripping to remove the dissolved hydrocarbons to an acceptable level
(Wagner, et al., 1986). The use of the PCS coke settling pond and the
service water ditch for discharged skimmed water from RW-1 and
the interceptor trenches, respectively, should be evaluated as this
may also be re-introducing contaminants into the ground water
through seepage as was previously discussed and presented in Table
17. An enclosed treatment system as opposed to open ponds would be
more appropriate. In conclusion, the treatment technologies currently
in place should be re-evaluated to determine further impacts to the
ground water and/or surface water bodies.
o The oil recovery system installed to treat the floating hydrocarbons
appears to have significantly reduced accumulations of hydrocarbons
across the site. As part of the performance monitoring of this
recovery system, Texaco should continually monitor the existence of
intersecting capture zones (overlapping cones of depression) to assure
that the plume is being contained and captured. This evaluation
program should include the identification of dead zones where
contamination is not being influenced by the recovery system. Also,
the influence of the recharge wells should be evaluated as to their
impact to the shape of the floating hydrocarbon plume. As was
previously mentioned, the impact from the recovery and recharge
wells on the interceptor system should be evaluated.
E. SAMPLING AND ANALYSIS
This section of the report assesses Texaco's Sampling and Analysis Plan for compliance
with the applicable technical recommendations and regulatory requirements of 40 CFR
265.92 and proposed for 40 CFR 264. Texaco's field implementation is also assessed for
compliance with accepted methodologies and adherence to their sampling and analysis
plan. Following the above assessment, the analytical results of the Task Force inspection
are presented and discussed. Also, an analytic comparison between the split samples (Task
Force and Texaco) are provided. Finally, this section compares the analytical results from
the Task Force to past results from Texaco.
154

-------
eval-B
1. Texaco
a. Sampling and Analysis Plan Review
Two sampling and analysis plans and one addendum have been submitted by
Texaco in their Part B Permit Application. The report entitled Casper
Texaco Refinery Sampling and Analysis Plan was prepared by Western
Water Consultants, Inc. on November 19, 1981 (WWC, 1981). An addendum
to this plan was prepared by the same author on May 5, 1982. Interestingly,
this addendum contained an undated Ground-Water Monitoring Manual
prepared by TriHydro Corporation, which is for the most part a sampling
and analysis plan. The Part B Permit Application docs not specify how
these reports arc related. Because all were submitted within the application,
the Task Force will consider them as a single document and review them as
such.
The sampling and analysis plan addresses the following topics: prcsampling
procedures, sample collection, sample preservation and shipment, analytical
procedures and chain-of-custody control. Most of the above topics are not
addressed in any appreciable detail. A brief discussion of the above topics
follows:
Prcsampling Procedures All wells will be monitored for water levels prior
to water quality sampling. At least three saturated well column volumes
will be evacuated prior to sampling. Field parameters will include specific
conductance, temperature, and pH.
Sample Collection A submersible pump or bailer will be used to obtain
water samples. The pump or bailer will be constructed out of materials
resistant to leaching or sorbing when placed in contact with ground water.
To reduce possible interpretation errors on the vertical segregation of water
quality at the nested well site, the shallow wells will be pumped and
sampled first. The pump and bailer will be thoroughly cleaned after
sampling each well. Samples to be analyzed for volatile organics will be
transferred directly to a VOA bottle.
Sample Preservation and Shipment The plan states that all sample bottles
will be cleaned with the acid used in the preservation procedure if required
and distilled water. In addition, two distilled water blanks preserved with
concentrated nitric acid will be analyzed for the heavy metals. Preserved
samples will be refrigerated and transported to the laboratory for analysis.
Samples will reach the laboratory within 24 hours of collection.
Analytical Procedures The plan states that analytical procedures will be
selected from "Standard Methods (APHA, 1975), Manual of Methods for
Chemical Analysis of Water and Wastes (EPA, 1979), and the Annual Book
of ASTM Standards (ASTM, 1980)" wherever possible (WWC, 1981).
Chain-of-Custody According to the plan, a chain-of-custody record will be
maintained for every sample in order to document sample possession from
the time of collection through the time of analysis.
155

-------
eval-B
In accordance with the TEGD (EPA, 1986), the following technical
deficiencies of the written sampling and analysis plan were noted by the
Task Force:
o The air in the well head should be sampled for organic vapors using
either a photoionization analyzer or an organic vapor analyzer.
o A discussion of how static water levels will be obtained is not
included.
o The plan does not specify how light and/or dense phase immisciblcs
will be detected. A discussion on how Texaco will determine the
thicknesses of such layers should also be included.
o A step by step procedure for well evacuation was not included in the
plan. Specifically, the procedures used by the facility when an
appropriate volume of water cannot be evacuated, should be
discussed.
o Texaco should further discuss sample withdrawal procedures. The
plan docs state the choice of materials used during sampling
withdrawal, but docs not indicate how samples will be obtained for
light and/or dense phase immisciblcs.
o Texaco indicates in the addendum to the sampling and analysis plan
that ground water samples that arc organically contaminated should
be filtered. This is in direct opposition of current protocols.
o A detailed QA/QC program that will be used in the field and
laboratory was not specified in the plan.
The above deficiencies in the plan indicate that the sampling and analysis
plan lacks the detail required as set forth in 40 CFR 265.92(a) and also the
technical recommendations in the TEGD (EPA, 1986a) due to a lack of
detail.
The only other regulatory deficiency noted by the Task Force in the written
plan specifically for the 40 CFR 264 ground water program was that a
statistical procedure for determining whether a statistically significant
change has occurred was not proposed [40 CFR 264.97(h)(2)].
b. Field Implementation (Sampling Audit)
Two months prior to the actual Task Force evaluation, members of the Task
Force scheduled a sampling audit coinciding with Texaco's scheduled round
of sampling at all wells in the North Area (EPA, 1986b). The purpose of
this audit was to evaluate Texaco's field procedures relative to their
sampling and analysis plan and accepted methodologies. Samples were
collected by Western Water Consultants, Inc. on behalf of Texaco.
Western Water Consultants stated that all the wells had three casing volumes
of water removed. Also, some of the wells had gone dry before three casing
volumes could be removed, and it was necessary to revisit some of the well
156

-------
eval-B
sites to remove the three casing volumes. It should be noted that evacuation
of the wells took place before the Task Force arrived in the field. An
independent evaluation of the methods used to calculate the three casing
volumes and how the quantity was measured could not be performed.
The sampling procedures were the same at all wells. Western Water
Consultants stated it followed the procedures listed in the document entitled
Casper Texaco Refinery Sampling and Analysis Plan, written by the same.
The Task Force observed that a 1 1/2 inch I.D. stainless steel bottom-filling
bailer was used for sampling the wells. A braided white rope was present in
each well. It was stated that this rope was also used on the bailers which
were used to purge the wells. According to Western Water Consultants, new
ropes are used during each sampling event. Plastic drop cloths were present
around each well to minimize the contact of the bailer rope with potential
contaminants on the ground surface.
Prior to sampling, the stainless steel bailer was cleaned in the field by first
rinsing with a small amount of acetone, and then with deionized water.
The rope was then attached and the bailer was lowered into the well. The
first bail of water was used to rinse the device used for filtering samples
obtained for the analysis of metals. The filtering device was then filled
and placed into a positive pressure nitrogen drive filtering apparatus. A
0.45 micrometer filter was used. One liter plastic bottles, with preservatives
already emplaced, were then filled for analysis of metals.
The subsequent sample bottles were filled by pouring the ground water
directly from the top of the bailer into the appropriate sampling container.
Labels on the sampling containers were filled out prior to filling the bottles.
The pH, temperature, and specific conductance of the well samples were
measured in the field by filling a glass beaker with ground water from the
bailers. The field instruments were calibrated in the field, at the beginning
of each day, and immediately prior to use. All the filled sample bottles
were placed into a cooler with "blue ice." Preparation of chain-of-custody
records was not observed. It was stated by Western Water Consultants that
the appropriate forms are filled out in the office prior to shipping the
samples. Western Water Consultants also stated that the samples arc shipped
by bus to Accu-Labs, which is located in the Denver metropolitan area.
The parameters to be analyzed varied depending on which well was
sampled.
At most of the wells, samples were taken for the analysis of:
0
dissolved metals
0
phenols
0
anions
0
oil and grease
0
cyanide
0
nutrients
0
sulfide
0
TOC
157

-------
eval-B
The sampling for the above parameters was done on the majority of wells
sampled during this event (RCRA semi-annual). On ten of the wells,
Texaco changed the analysis to include sampling for organic constituents.
The parameters sampled on the ten wells were the same as the list given
above with the following changes:
o	volatile organic analysis
o	base-neutral organic analysis
o	no oil and grease analysis
o	no cyanide analysis
The following deficiencies in sampling methodologies were noted:
o The air in the well head was not sampled for organic vapors.
o Texaco did not sample for light and/or dense phase immisciblcs, nor
determine the thickness of any such layer.
o The first bail of water was used to rinse the filter used for dissolved
metal analysis. Samples taken for volatile organic analysis should be
taken first to minimize disturbance of the well water by the bailer.
o The composition of the bailer rope was not specified.
The above discussion noted the technical deficiencies as observed by the
Task Force. In general, Texaco's sampling procedures appear adequate. The
sampling audit verified that Texaco's current sampling procedures arc more
up to date than the sampling and analysis plan. The Task Force
recommends that Texaco update its November, 1981 plan and addendum to
incorporate current recommendations of the TEGD (EPA, 1986a).
Task Force
a. Techniques of Sampling
The Ground Water Task Force conducted an evaluation of the Casper
Texaco facility from August 11 to 15, 1986. This evaluation included
conferences with facility representatives and an independent sampling of 16
ground-water monitoring wells and three surface water locations. In
addition, five QC samples were taken including a field blank, three
equipment blanks and a trip blank. The sampling procedures listed below
were detailed by the Ground Water Task Force in a Project Plan dated
August, 1986 (EPA,. 1986c).
Well Purging Table 18 presents the list of parameters analyzed by the CLP
laboratory during the Task Force evaluation. Field analysis included pH,
specific conductance, temperature, turbidity and static water level
measurements. All field analysis and sample collection were performed by
Versar Inc., on behalf of the Task Force. The field analyses may be found
in Appendix D.
Prior to sampling, depth to water measurements were obtained. Standing
water in all wells sampled by the Task Force (Versar Inc.) was removed
158

-------
TABLE 18 Analytical Parameters
VOLATILES
chloromethane
bromome thane
vinyl chloride
ch1oroethane
methylene chloride
acetone
carbon disulfide
1,1-dichloroethene
1.1-dichloroethane
trans-1,2-dichloroethene
chloroform
1.2-dichloroethane
2-butanone
1,1,1-trichloroethane
caroon tatrachlorioe
vinyl acetate
bromoaichloromethane
1,1,2,2-tetrachloroethane
1,2-di chloropropane
trans-1,3-dichloropropons
trichloroethane
di Dromochloromethane
1,1,2-trichloroethane
benzene
cis-1,3-dichloropropene
2-chloroethylvinyl ether
bromoform
2-hexanone
4-methy1-2-pentanone
tetrachloroethene
toluene
chlorobenzene
ethylbenzene
styrene
SEMI VOLATILE COMPOUNDS
acenaphthene
2,4-dini trophenol
bis (2-chloroethyl)ether
2-chlorophenol
1.3-dichloroDenzene
1.4-dichlorobenzene
benzyl alcohol
1,2-di chlorobenzene
2-methylphenol
bi s(2-chloroisoproply)ether
4-methylphenol
n-nitroso-di-n-propyl amine
hexachloroethane
ni trobenzene
leophorone
2-ni trophenol
2,4-dimethylphenol
benzoic acid
bis (2-cnloroethoxy) methane
2,4-dichlorophenol
1,2,4-tncn lorobenzene
naphthalene
4-chlonoam 1 i ne
hexach1orobutadiene
4-chloro-3-metnylphenol
phenol
4-ni trophenol
di benzofuran
2,4-dinitrotoluene
2,6-dinitrotoluene
diethylphthalate
4-chlorophenyl-phenyl other
fluorene
4-ni troani1i ne
4,6-di nitro-2-methy1 phenol
n-ni trosodi phenyl ami ne(1)
4-bromophenyl-phenyl ether
hexachlorobenzene
pentachlorophenol
phenanthrene
anthracene
di-n-Dutylphthalate
fluoranthene
benzidine
pyrene
butyl benzylphthalate
3,3-dichlorobenzidine
benzo (a) anthracene
bis (2-ethylhexyl) phthalate
chrysene
Source: Project Plan Ground-Water Monitoring Compliance Evaluation
Hazardous Waste Ground Water Task Force, Texaco Inc.,
Casper, Wyoming, August 1986.
159

-------
Table 18
2-methyl naphthalene
hexachlorocyclopentadi ne
2,4,6-trichlorophenol
2,4,5-trochlorophenol
2-chloronaphtnalene
2-ni troan i1i ne
dimethyl phthalate
acenaphthylene
PESTICIDES/PCB'S
alpha-BHC
delta-BHC
heptachlor
heptachlor epoxide
dieldrin
endn n
4,4-DDD
endosul fan sulfate
methoxychlor
chlordane
aroclor-1016
aroclor-1232
aroclor-1243
aroc1or-1260
METALS AND OTHERS
alumi num
antimony
arsenic
bari um
Dery11lum
cadmi um
calcium
chromium
coDalt
copper
i ron
lead
cyani de
ammonia
chloride
nitrate
purgeaDle organic carDon
purgeaole organic carbon
Sulfides
Total Sslfides
Tds
(continued)
di-n-octyl phthalate
benzo (b) fluoranthene
benzo (k) flupranthene
benzo (a) pyrene
indeno (1,2,3-cd) pyrene
. dibenz (a,H) anthracene
benzo (g.h.t) perylene
3-nitroaniline
beta-BHC
gamma-BHC (lindane)
aldrin
endosulfan I
4,4,-DDE
endosulfan II
endrin aldehyde
4,4-DDT
endrin ketone
toxaphene
aroclor-1221
aroclor-1242
aroclor-1254
magntsium
manganese
mercury
nickel
potassium
selenium
si 1ver
sodium
thai 1i um
ti n
vanadium
zi nc
percent solids ()
sulfates
total organic carbon
total organic ha1ioe
total phenois
160

-------
prior to sampling. Removal of three casing volumes was attempted using a
Teflon bailer or bladder pump. When the recovery rate of the well was
sufficient, three well volumes were purged and sampling instituted. The
order of collection, beginning with volatile organics, is presented in Tabic
19, along with the bottle type and preservation method. The amount of
water removed was determined by collecting it in a container of known
volume during purging.
Where slow-recharging wells were encountered, the three casing volume
minimum evacuation requirement was waived. In these situations, the
volatile organic samples were collected as soon as possible. The other
samples were collected after a sufficient volume had accumulated. The
purged water was treated as a hazardous waste and shipped off-site for
disposal. For wells in which historical or field information did not indicate
contamination, the purged water was disposed of at the well.
The following information was recorded during purging of the well (note
that Western Water Consultants did the actual purging of the wells prior to
the arrival of the Task Force):
1)	Type of purging equipment used and types of materials used in well
construction, including lines used to lower equipment into the well.
This was recorded for each well. Also noted was if facility-
dedicated equipment was used.
2)	Physical properties of evacuated water:
o Color,
o Odor,
o Turbidity,
o Presence of oil/grease or heavy-phase organic compounds.
3)	Intake depth in wells not completely evacuated.
4)	Volumes purged from all wells.
5)	Time interval necessary for each purge sequence.
6)	Methods used to determine volumes evacuated.
7)	Procedures for collection, management and disposal of evacuated
water.
8)	Decontamination and cleaning procedures for equipment used to
sample more than one well.
Sample Collection In wells in which an immiscible phase was not
encountered, dedicated Teflon bailers with double check valves that are
bottom emptying were used for sample collection. These bailers were used
for the collection of all sample parameters. The Teflon bailers were
lowered into the wells using a Teflon and stainless steel cable. The
sampling proceeded as follows:
161

-------
TABLE 19 Sampling Order, Bottle Type and
Preservation Method
Sampl1ng
Order	Parameter Dottle Type Preservati ves
1.	Volatile orgamcs 4 - 40 ml VOA vials Cool 4
2.	PurgeaDle organic 1 - 40 mL VOA vials Cool 4
carDon (POC)
3.	PurgeaDle organic 1 - 40inL VOA vials Cool 4
halogens (POX)
4.	ExtractaDle organics 4 - 1 L. amber glass Cool 4
5.	Pestlcides/herDicles 2 - I L. amber glass Cool 4
6.	Dioxin 2 - 1 L. amber glass Cool 4
7.	Total metals 1 L. plastic IIIIO3-5 mL
8.	Dissolved metals 1 L. plastic 1UJ03-5 mL	r
9.	Tot^ggyganic c^^^^oq 1 - 50 mL glass II2SO4
10.	Total organic halogens 1 L. amber glass Cool 4C
(TOX)	no headspace
11.	Phenols 1 L. amber H2SO4-5 mL
Cool 4
12.	Cyanide 1 L. plastic NaOH-5 mL
Cool 4
13.	Sulfate and chlorine 1 L. plastic Cool 4
14.	Nitrate and ammonia 1 L. plastic h2S04~5 mL
Cool 4
Source: Project Plan Ground-Water Monitoring Compliance Evaluation
Hazardous Waste Ground Water Task Force, Texaco Inc.
Casper, Wyoming, August 1986.

-------
eval-B
1)	Selection ot a new or cleaned Teflon bailer.
2)	Attached bailer to a Teflon-coated stainless steel cable.
3)	Lowered the bailer siowly until it contacted the water surface.
4)	Allowed the bailer to sink to the bottom of the screened interval and
then filled with minimal surface disturbance.
5)	Slowly raised the bailer to surface. Efforts were made not to allow
the bailer line to contact the ground surface by placing the bailer
line on a protective liner.
6)	Opened the bottom emptying device to allow slow discharge down the
side of the sample bottle with minimal entry turbulence.
Intermediate sample containers were not used.
7)	Repeated the above steps as needed to acquire a sufficient sample
volume to fill all containers. The sample bottles were filled by
parameter sets.
In wells in which an immiscible phase was encountered, a bladder pump
constructed of Teflon was employed. The bladder pump was operated by
compressed air from air cylinders. The bladder pump intake was lowered
slowly through the immiscible oil phase to the bottom of the well, and then
moved up approximately one foot to minimize the introduction of
sediments. After three casing volumes were removed, sampling began. The
pumping rate was adjusted to minimize the velocity at which water exits the
sample orifice to minimize turbulence.
Pond Sampling Samples of the liquids contained in one waste pond in the
South Area and two ponds on the North Area were obtained. The samples
obtained were also analyzed for the parameter listed in Table 18.
Sampling of the three ponds was performed using an intermediate collection
container attached to a pole. The container was constructed of Teflon, and
was rinsed before filling with the desired pond liquid twice before taking a
sample. Care was taken to avoid leaves, stones, sediments and other debris
that was present. The appropriate sample container was filled in a manner
that minimized sample agitation/aeration.
The same in-situ parameters measured at each well were also measured at
each pond sampling site. The three surface water sample locations were as
follows:
1)	Inlet pond to the Excess Service Water Ponds on the North Area of
the North Platte River.
2)	The pond formed at the base of the bluff near well M-12s on the
North Area of the North Platte River.
3)	The PCS coke setting pond on the South Area of the North Platte
River.
163

-------
eval-B
Quality Assurance/Oualitv Control The sampling activities during these
evaluations were supported by preparing and analyzing several sets of
quality control (QC) samples. The QC samples fell into two major
categories, including field blanks and field duplicates. Laboratory QC
samples (performance evaluation sample) were not required by the
laboratory.
Several types of QC blanks were employed during the evaluation. They
included:
o Trip blanks,
o Field blanks,
o Equipment blanks.
Trip blanks are used to determine if contamination is introduced from the
sample containers. This includes the time during container transport to the
facility and container storage at the facility. These blanks were prepared
by the sampling team selected for the Texaco facility. They were prepared
by using certified, organic free water of known high purity, and were sent
with the other sample bottles to the field. For each analytical parameter
group such as organic compounds, metals, and volatile compounds, one set of
trip blanks was prepared and accompanied the monitoring personnel during
the sampling activities.
Field blanks were used to determine if contamination was introduced by the
sample collection activities or sampling environment. They were prepared
by bringing a quantity of certified, organic free water to the field and
using this water to prepare appropriate sample aliquots for each parameter.
Equipment blanks arc used to determine if contamination is introduced by
the sample collection equipment. Although the recommended procedure is
to have dedicated equipment for each monitoring well to be sampled, there
were occasions when some equipment, including bladder pumps and bailers,
were reused. After the equipment was decontaminated, a quantity of
certified, organic free water was passed through the instrument and aliquots
collected for each analytical parameter. An equipment blank was collected
by the sampling personnel each day that sampling equipment was reused
during the evaluation. This was submitted for analysis in place of the field
blank for that day of sampling.
Duplicate samples arc a method of checking on the precision of analytical
methods of the laboratory. The duplicate samples were submitted to the
analytical laboratory along with all other samples. One duplicate sample
was taken at well M-36.
Equipment All field equipment that was used for obtaining field
measurements was calibrated prior to the investigation and at periodic
intervals during use. Calibration records were maintained to demonstrate
the precision and accuracy of field measurements made with a particular
instrument.
Calibration records included:
o A unique identification number assigned to the device.
164

-------
eval-B
o The source and traccability of the standard(s) used for calibration.
o The name of the person performing the calibration, the date and
notation as to whether it was a routine check or one required by
malfunction.
Equipment calibration was further supported by routine maintenance, as
required by the individual types of equipment used. Routine maintenance
included changing batteries in portable meters and lubricating moving parts
of a sampling device with non-contaminating materials.
Maintenance records were kept similar to calibration records, and
documented the type of work done (routine checks, emergency repairs), the
person performing the work, and the identity of the equipment.
Decontamination Decontamination of all field equipment was performed
prior to use. The decontamination was performed off-site whenever
possible. The waste solvents were collected in a container for proper
disposal. Decontamination procedures for smaller sampling equipment such
as soil scoops and containers were not necessary, as the equipment was
properly disposed of after use.
On-site decontamination was performed only when extenuating
circumstances dictated. On-site decontamination was performed by the
procedure as for off-site decontamination.
When bailers and bladder pumps were decontaminated on-site, an equipment
blank was collected by rinsing the equipment with certified, organic free
water and submittal of aliquots of the rinsate (equipment blank) to the
laboratory for analysis.
Documentation Accountable field documents included items such as
logbooks, field data records, correspondence, sample tags, graphs, chain-of-
custody records, bench cards, analytical records and photographs.
All field logbooks, field data records, field laboratory logbooks, sample tags
and chain-of-custody records were assigned to the inspection personnel for
appropriate distribution and accountability. All pertinent factual
information was recorded in these logbooks from the time each individual
was assigned to the inspection team, until the inspection was completed.
Logbook entries were dated, legible, and contained accurate and inclusive
documentation of inspection activities.
Chain-of-Custodv Each sample shipment was accompanied by a chain-of-
custody record identifying its contents. The original record accompanied
the shipment, and a copy was retained by the sampling team. When
replicate samples were offered to the facility, it was noted in the remarks
section of the custody form. The note indicated to whom the replicate
samples were offered, and was signed by both the sampler and recipient.
Labeling and Packaging All samples collected were labeled in a clear and
precise way for proper identification in the field and for tracking in the
165

-------
laboratory. Sample labels had a prc-assigned, unique number that was
indelible and waterproof. A two-part label was used so that the sample
identification number was affixed to the sample bottle and also entered in
the field logbook at the time of collection. The label attached to the bottle
listed only the sample number; the label for the notebook included the
sample number and the following information:
0
Project code number.
0
Station location and number,
0
Date and time,
0
Sample type (composite or grab).
0
Signature of sampler.
0
Preservative indication (yes and no; type),
0
Analyses required, and
0
Additional remarks.
Samples were properly packaged for shipment and dispatched to the CLP
laboratory for analysis, with a separate custody record accompanying each
shipment (e.g., one for each laboratory, one for samples driven to
laboratory). Shipping containers were sealed for shipment to the laboratory.
Only metal and plastic ice chests were utilized as the outside shipping
container. The drainage hole at the bottom of each ice chest was
permanently plugged to prevent any possibility of leakage through the hole.
Each icc chest was clearly marked with arrows indicating the proper
upright position of the container, a label indicating "THIS END UP" on the
top, a label stating "ENVIRONMENTAL SAMPLES" on the lid, and a sticker
containing the originator's name and address.
Each ice chest was securely taped shut. This was accomplished by wrapping
reinforced tape around the ice chest near each end, where the hinges arc
located. Sample containers were packaged in the following manner:
Glass Containers
o The containers were separated in the shipping container by
cushioning to prevent breakage due to contact with other glass.
o The small glass vials for volatile organic samples were placed inside
a larger plastic container to minimize breakage and to contain any
leakage.
Plastic Containers
o The cap was tightened securely before it was placed in the shipping
container.
166

-------
o The plastic containers were packaged so as to be protected from
punctures from sharp objects.
All sample containers and wet ice were packed inside a sturdy plastic bag,
placed inside the shipping container as an inner pack. The plastic bag was
tightly closed after all of the sample containers and ice had been added to
prevent any leakage of material from the bag.
Transportation Samples transported off-site to the CLP were packaged for
shipment in compliance with current DOT and commercial carrier
regulations. All required government and commercial carrier shipping
papers were filled out and shipment classifications made according to
current DOT regulations.
Sample traffic reports, chain-of-custody records, and any other shipping/
sample documentation accompanying the shipment were enclosed in a
waterproof plastic bag and taped to the underside of the cooler lid. All
samples were shipped "Priority One/Overnight" to the CLP laboratory. If
shipment requires more than a 24-hour period, sample holding times may
compromise the integrity of the sample analyses. When holding times were
exceeded, the analyses were not performed. The Sample Management Office
(SMO) was notified immediately after sample shipment, and was provided
with the following information:
o Sampling contractor's name;
o Project number;
o Exact number(s) and typc(s) of samples shipped;
o The name of the facility and location from where the samples
were being shipped;
o The laboratory that the samples were shipped to;
o Carrier, airbill number(s), method of shipment (e.g., priority,
two-day);
o Shipment date and time; and
o Irregularities or anticipated problems, such as special handling
needs, and hazardous samples.
b. Interpretation of Data
This subsection summarizes the usability of the Task Force results, the
QA/QC results and provides a generalized interpretation of the Task Force
data. Lockheed Engineering and Management Service Company, Inc.
(Lockheed) provided the Task Force with the organic and inorganic
usability audit reports. PRC Engineering provided the same with a QA/QC
data evaluation report.
167

-------
eval-B
Two separate laboratories performed the actual analyses: Compu Chem
Laboratories of Research Triangle Park, NC, for organic analyses and
Centec Laboratories of Salem, VA, for the inorganic and indicator analyses.
Both arc utilized as CLP laboratories.
i) Organic/Inorganic Usability
The organic and inorganic usability audit report was prepared by
Lockheed, and is presented in Appendix G. This report lists the
sample number and the associated matrix for comparison. The
following is a summary of their findings.
Organics - The organic analysis met the accuracy Data Quality
Objectives (DQOs) established for the program, except eight of 22
average percent recoveries of matrix spike compounds. All the
precision DQOs were met; the average RPDs for both matrix spike
and surrogate compounds arc within the DQOs for the program.
Volatilcs by purge and trap data quality - The analysis of these
compounds can be considered quantitative with a few exceptions.
The detected compounds in samples Q0588 (M-36), Q0590 (M-36 Dup),
Q0596 (SS-19), and Q0599 (SS-49) arc judged semiquantitative. The
high dilutions of the samples may have resulted in false negatives.
The usability parameters arc acceptable.
Semivolatile Data Quality - The scmivolatilc analysis is judged
quantitative for 18 of 25 samples. However, all detected compounds
in samples Q0586 (M-10D), Q0591 (M-51As), Q0596 (SS-19), Q0588 (M-
36 Dup), Q0590 (M-36 Dup), Q0599 (SS-49), and Q0804 (SS-4) arc
considered semiquantitative with the possibility of false negatives.
Samples Q0588 (M-36 Dup), Q0590 (M-36 Dup), Q0599 (SS-49), and
Q0804 (SS-4) are considered suspect because of unusable QC
surrogate data and matrix spike data.
Pesticide Data Quality - The pesticide analysis is judged suspect due
to high dilutions, poor matrix spike and surrogate spike recoveries,
problems with dibutylchlorendate shifts and unaddresscd peaks in
the chromatograms.
Metals - The average percent recoveries for total metals are within
the program accuracy DQOs in 87% of the low concentration samples
and 91% of the medium concentration samples. The average RPDs
are within the program precision DQOs in 91% of the low
concentration and 100% of the medium concentration samples for the
total metals.
No laboratory blank contamination was reported. A1 and Fe
contamination was found in the sampling blanks. Analyses met the
completeness goals.
All evaluation criteria used for the total metals are based on IFB WA
84-J092 (SOW 785).
168

-------
Inorganic and Indicator Parameters - The average percent recoveries
for the inorganic and indicator parameters are within the program
accuracy DQOs in 92% of the low concentration and 100% of the
medium concentration samples. All the inorganic and indicator
parameters are within precision DQOs.
No laboratory blank contamination was reported. However, phenol
and TOC contamination was found in the sampling blank. Analyses
met the completeness goal.
All evaluation criteria used for CN are based on IFB WA 84-J092
(SOW 785).
ii) QA/QC Audit
The QA/QC audit was prepared by PRC Engineering and is
presented in Appendix H. Summarized below are their findings.
Oreanics
Quantitative:
Semi-quantitative:
Qualitative:
volatile and semivolatile results with exceptions.
volatile results for samples Q0588 (M-36 Dup),
590 (M-36 Dup), 596 (SS-19), 599 (SS-49), and
801 (SS-7); semivolatile results for samples
Q0586 (M-10D), 591 (M-51As), and 596 (SS-19);
and positive semivolatile results for samples
Q0588, 590, 599, and 804 as previously
mentioned.
all pesticides results; all negative (non-dctcct)
semivolatile results for samples Q0588 (M-36
Dup), 590 (M-36 Dup), 599 (SS-49), and 804 (SS-
4) arc qualified by a higher than usual
probability of false negative results due to
dilution.
Graphite Furnace Metals
Quantitative:
Qualitative:
Unreliable:
all arsenic, cadmium, thallium, and selenium
results; antimony and lead results with
exceptions.
antimony results for sample MQ0586 (M-10D)
and lead results for sample MQ0588 (M-36 Dup).
antimony results for sample MQ0591 (M-51As)
and lead results for sample MQ0596 (SS-19).
169

-------
eval-B
ICP Metals
Quantitative:	all barium, beryllium, calcium, chromium,
cobalt, copper, magnesium, manganese, nickel,
potassium, silver, sodium, and vanadium results
and medium concentration matrix results for
aluminum with exceptions and iron and zinc.
Semi-quantitative: low concentration matrix iron results with
exceptions listed below.
Qualitative:	low concentration matrix positive aluminum
results for samples MQ0588 (M-36 Dup), 589 (M-
35), 590 (M-36 Dup), 591 (M-51As), 592 (M-33),
593 (SP-7), 598 (SS-34) and 806 (41 A); medium
concentration aluminum results for sample
MQ0596 (SS-14); low concentration matrix zinc
results; and low concentration matrix iron
results for samples MQ0583 (M-l) and 586 (M-
10D).
Unusable:	low concentration matrix negative aluminum
results; low concentration matrix positive
aluminum results for samples MQ0583 (M-l), 584
(M-6), 585 (M-lOs), 597 (M-l2s), 599 (SS-49), and
801 (SS-7); iron results for sample MQ0803
(alluvial pond).
Mercurv
Quantitative:	all mercury results.
[noreanic and Indicator Analvtcs
Quantitative;	all chloride, bromide, and sulfate results; nitrate
nitrogen, nitrite nitrogen, ammonia nitrogen,
total phenols, TOC, and TOX results with
exceptions; and cyanide results for samples
MQ0596 (SS-19), 599 (SS-49), 802 (inlet pond),
803 (alluvial pond), 804 (SS-4), and 805 (PCS).
Semi-quantitative; all POX results; ammonia nitrogen results for
samples MQ0582 (blank), 583 (M-l), 584 (M-6),
801	(SS-7), 802 (inlet pond), 803 (alluvial pond),
804 (SS-4), 805 (PCS) and 806 (M-41A); nitrate
and nitrite nitrogen results for samples MQ0589
(M-35), 593 (SP-7), 597 (M-12S), 801 (SS-7), and
802	(inlet pond); TOC results for samples
MQ0589 (M-35), 592 (M-33), 593 (SP-7), 596 (SP-
19), 597 (M-12S), 801 (SS-7), 802 (inlet pond),
and 803 (alluvial pond); and TOX results for
samples MQ0584 (M-6), 585 (M-10S), 586 (M-
10D), 587 (blank), 597 (M-12S), 599 (SS-49), and
600 (equipment blank).
170

-------
eval-B
all POC results; and cyanide results for samples
MQ0582 (blank), 585 (M-10S), 586 (M-IODj, 592
(M-33), 593 (SP-7), and 597 (M-12S).
cyanide results with the above exceptions; total
phenols results for samples MQ0592 (M-33), 593
(SP-7), 596 (SS-19), 597 (M-12S), 801 (SS-7), 802
(inlet pond), 803 (alluvial pond), 804 (SS-4), and
806 (M-41A); and TOC results for samples
MQ0583 (M-l), 584 (M-6), 598 (SS-34), and 806
(N1-41A).
iii) Analytical Results
Ground water and to a lesser degree surface water samples collected
by the Task Force confirm that hazardous waste constituents or other
indications of contamination exist beneath and around the Texaco
facility. The Task Force sample results above detection limits are
presented in Tabic 20. The raw data may be found in Appendix A.
Figure 41 shows the 16 ground water and three surface water
locations where the Task Force obtained samples.
Organic Analysis Analytical results confirm organic contamination
on both the North and South Areas of the facility. In addition,
several constituents were detected in the surface water of the PCS
Pond. The results from the North Area are summarized below.
Wells M-l and M-6b are located near the Excess Service Water
Effluent Ponds (Figure 41), and show no evidence of organic
contamination (the reader is continually reminded to refer to Table
20, as no quantitative results will be reiterated in this section). Well
M-36 shows the highest overall organic concentrations of all wells
sampled by the Task Force. Based on its location relative to the CEP
and North Land Farm, and on past analytic data, this observation
was expected. Furthermore, the relatively high level of
contamination confirms that the source of ground-water
contamination in the North Area is from the CEP and/or the North
Land Farm. Downgradient wells M-lOs, M-lOd and M-51As (Figure
41) also indicate contamination, although in lower concentrations and
numbers of organic species than in M-36. Wells M-33 and M-35 are
located near the west and east property boundaries, respectfully.
Neither wells indicate any organic contamination. These results,
coupled with potentiometric surface maps, indicate that organic
contaminants do not appear to be migrating off-site at those locations
during the Task Force evaluation. It should be noted that a potential
for off-site contamination still exists as the number of wells sampled
by the Task Force totaled two wells.
Samples taken in the alluvial pond in the North Area clearly show
that several organic species exist in this area. It seems likely that the
source of these contaminants is from the CEP and North Land Farm,
based on potentiometric surface maps. Well completion logs further
Qualitative:
Unusable:
171

-------
M-l
M-6b
Acetone
Bftnteni
2-Butanone
Ethyl Benzene
Methylene Chloride
Toluene
Total Xylenes
Anthracene
Benzo (a) anthracene
Benco (b) fluoranthene
Banco (k) fluoranthene
Benco (a) pyreno
Chrysene
Fluorene
Fluoranthene
Naphthalene
2-Methyl-naphthalene
Phenol
2-Methy1phenol
4-MethyIphenol
2*4 Dlmethylphenol
2-Nltrophenoi
4-Nltrophenol
Pyrene
Phenanthrene
Chlordane
Heptachlor
M-lOs
59
12
Table 20
Analytic Results (Task Force)
August 11-15, 1986
M-lOd M-36 M-36 M-35 M-51As H-33
18
24
87
48
57
12
1100
0.26
3806
310
670
410
330
64000
50000
93000
14000
480
M-36
DUP
3000
270
570
360
290
23
76
INLET POND
15
34
59
62000
40000
96000
13000
300
1600
2000
SP-7 M-12a ALL. POHD
11
5.2
SS-19 SS-<
2000
170
290
890
770
1800
340
WOTEi
N - Spike recovery not within control limits.
- Blank indicates those concentrations below the lower llmLt of detection.

-------
SS-34	SS-7	SS-4
Acetone
Benzene
2-Butanone
Ethyl fiensene
Methylene Chloride
Toluene
Total Xylenes
Anthracene
Benso (a) anthracene
Benso (b) fluoranthene
Benzo (k) fluoranthene
Benso (a) pyrene
Chryiene
Fluotene
Fluoranthene
Naphthalene
2-Methy1-naphthalene
Phenol
2-Methylphenol
4-Methylphenol
2-4 Dimethylphenol
2-NltrophenoL
4-NLtrophenoL
Pyrene
Phenanthrene
Chlordane
Heptachlor
38	1400	900
180	41
44
460	140
480
860
700
360
230	610
960
2100
6000
Table 20 (continued)
H-41A PCS POND
12
5.5
27
33
26
26
23
68
TRIP
BLANK
FIELD
H-36
350
BAILER
BLANK
270
PUMP
BLANK
390
19
BAILER
BLANK
29
120
59

-------
Table
20 (continued)

M-l
M-6b
M-10
M-lOd
H- 36
M-36
M- 35
M-51AJ
H- 33
INLET P011D
SP-7
M-12s
ALL. POND
SS-19






DUP








Aluminum
110OM
488
704H

3330N
2290N
551 ON
20500N
3670H
154
5840N
1530H
131
2330N
Antimony


15.5

12.9
10.2






6.7

ArscnLc
12.3
13.7
53.6

196
229

79
3.2
7.1
10.9
31.5

14.4
Barium
36
36
81
37
106
106
59
411
47
119
135
166
20
1160
Beryllium














Cadmium






1.2
7.1





1.4
Calcium
18300
259000
568000
193000
8510
8550
88100
268000
224000
250000
77100
92400
73900
130000
Chromium




25
18








Cobalt


16

25
31

44
8

12
,8


Copper







55



'


Iron
914N
2270H
14800N
889N
2690N
2750
3460
224000
3360N
1110
17400N
12200
252
20300N
Lead

6.7
10.2

8
8
5.2
31
13.5

14.4
36. 1

11.1
Magnetlura
3920
87600
294000
121000
4220
4490
39600
176000
112000
278000N
72600
91700
58900N
80600
Manganese
26
249
49800
483
112
119
279
2740
887
7 3 OH
2570
1760
357
1620
Mercury





0.2
0.4






0.2
Nlckle


29

257
266

38


44
32


Potassium
3230
10600
5230
19300
8750
8800
11800
32000
18400
7960
15400
1 4 BOO
12000
4900
Selenium


141

99.2
73.5
8.1
2.3

27.5

38. 3


Stiver














Sodium
206000
208000
196000
519000
939000
990000
107000
316000
420000
920000
456000
467000
432000
154000
Thallium



2.0










Vanadium


13

151
153

80


13

9

Zinc
2630N
2950N
1090N
1660N
120N
34 N
36N
15900N
4 2M

5200N
2320N

30N
Total Phenola


6000
5500
394000
284000

4200
41
39
282
198
32
207
TOX

10
36
6.4



14
25
16
16

13
12
POX













7
TOC
1200
7800
69000
69000
676000
726000
18000
125000
16000
16000
29000
36000
16000
33000
POC




2600
2400

280

390

190

8100
N03-N
270

1510


0.05
3000

470
20000
5000
6000


HH3-N
300

19000
300
610000
580000

8000
1100

1800
4400

14000
H02-N














Chloride
1400
260000
40000
87000
10000
80000
18000
50000
7000
190000
80000
70000
58000
43000
Bromide



1900

1400

1600
550



250
600
S04
120000
750000
2580000
370000
480000
540000
290000
150000
74000
11500000
590000
500000
970000
50000
Cyanide


121N
414N



552
17 2N
36
14 5N
145N

20N
10800

-------

SS-34
SS-7
SS-4
Aluminum
24900N
4 SON
347
Antimony
6.9


Arsenic
20.3

39.9
Barium
564
928
1200
Berylllum



Cadmium



Calcium
172000
43900
120000
Chromium
18


Cobalt
23


Copper
33


Iron
56700H
4870N
52600
Lead
140
6.9

Magneslum
128000
79800
62900N
Manganese
2370
874
797N
Mercury



Nickle



Potasslum
10800
3 3 60
4190
Selenium
2.8


Silver



Sodium
160000
112000
127000
Thallium



Vanadium
72


Zinc
220H
2120N
1870
Total Phenols

76
109
TOX
11
20
17
FOX

7

TOC
10000
25000
48000
POC
650
4900
12000
N03-H

1000

NH3-N
4200
130
400
N02-N



Chloride
35000
31000
90000
Bromide
400

550
S04
350000
480000
5700
Cyanide	20
Table 20 (continued)
H-41A PCS POND
311
9.9
376
124000
1580
16800N
625H
102000
9754
12
39000
420
TRIP FIELD BAILER PUMP BAILER
BLANK M-36 BLANK BLANK BLANK
296
1 36N
532	277	533
759
86
2200
2.4
511
431
43
394
16
5
1300
389
394
107
137
7
584
574
41
3900
26000 120000
250
1000000 1000000

-------
TEXACO PROPERTY BOUNDARr
E CC SS SERVICE AA1 l r
L'FLUENT PONDS
/ NMD
1 t M ACO PHOCtM I r I
BOUNUAR
iahO
tm .&&!
 COO
C *  '
ooo
7'tZbI
liNU
RO*0 OIL
(CiL( IN fII1
rn wnlr r Cc n * u 11 onl >, IVr) '
_L t G L" N 0_
0 Apprui I'lio to Location of
Sufloce Wofe Sample
 Mont lot nig Ws I I
FIGURE 41
Task Force Sampling Locations
Texaco Refinery, Casper, Wyoming
kttsto to
ON L * I i*11
(1I.0DN COM p '

-------
eval-B
support this notion as they reveal zones of higher conductivity
within the confining unit. These zones most likely contribute to the
discharge points, or seeps, located in the bluffs immediately above
the alluvium.
Analytical results from the South Area further confirm organic
contamination. Five of the six wells sampled by the Task Force
indicate contamination above detection limits. Only well M-41A
(Figure 41) did not indicate the presence of organics during the
sampling event. This confirms this well as an upgradient background
well. The PCS Pond was found to contain a wide variety of organic
species, although in generally low concentrations.
The analytical results confirm that both light and dense phase
immiscibles should be monitored for. This is due to the detection of
constituents listed in Table 5 which arc characteristic of light and
dense phase refinery wastes. Of the organics detected at the Tc.xaco
facility, only two have established criteria for which comparisons
can be made. These criteria include maximum concentration limits
(MCLs) and recommended maximum concentration limits (RMCLs).
Benzene was detected above the MCL of 5 micrograms per liter
(mg/1) in ten of the 16 wells sampled by the Task Force. Xylenes do
not have an MCL, although a Recommended Maximum Concentration
Limit (RMCL) has been proposed. Four wells had concentrations of
Xylenes above the RMCL of 440 ug/l. Three of these were located
on the South Area and one in the alluvium on the North Area.
Inorganic Analysis Ground-water samples from the North Area
indicate concentrations of metals and indicator parameters above
MCL, RMCL, and Secondary Drinking Water Standards.
Arsenic and selenium have MCLs of 50 and 10 ug/l, respectively.
Wells M-lOs and both sets of samples from M-36 show concentrations
which exceed these standards. A surface water sample from the inlet
of the Excess Service Water Effluent Pond shows a value above the
MCL for selenium. The RMCL of 10,000 ug/l nitrate was also
exceeded at the inlet location.
Secondary Drinking Water Standards for iron, manganese and sulfate
were exceeded at several wells and the inlet location.
Analytical results from the North Area alluvium indicate levels of
iron, manganese, selenium and sulfate above the applicable standards.
Most of these were from wells SP-7 and M-12s, although the alluvial
pond displayed elevated concentrations of manganese and sulfate.
The South Area wells indicate the following parameters above the
applicable standards: barium, iron, and sulfate. The PCS Pond also
displays iron and sulfate above standards.
177

-------
eval-B
3. Data Comparison (Task Force and Texaco)
Ground-water and surface water samples were collected in the field for the Task
Force by Vcrsar, Inc. Sample splits were presented to Western Water Consultants
on behalf of Texaco. The data comparison is presented in Table 21. Tcxaco's
PARL laboratory analyzed samples from wells M-lOs, M-lOd, M-36, M-51As, SS-49,
SS-34, SS-4, M-41A; from the Inlet Pond, Alluvial. Pond, PCS Pond; two bailer
blanks and one pump blank. Accu-Labs Research, Inc. analyzed Tcxaco's splits
from wells M-l, M-6, M-35, M-33, SP-7, M-12s, SS-19, and SS-7. Accu-Labs ran the
inorganic contaminants and indicator parameters but subcontracted the organic
contaminants to Rocky Mountain Analytical Laboratory. The raw data arc located
in Appendix I for the Texaco samples. All analytcs ran for organics, inorganics
and indicators and detection limits are listed in Appendices I.
The Task Force data were analyzed by EPA contract labs under the CLP. The raw
data, in addition to the detection limits reported by the lab(s), is included in
Appendix A. It should be noted that three samples collected by the Task Force
were medium concentration samples and, as such, the detection limit was elevated.
Often, the comparison of Task Force data was made on a limited list of
constituents with Texaco's data from the two laboratories. For example, Texaco's
PARL laboratory reported only a partial list of results for inorganics, organics and
indicator parameters as shown on Table 22. For comparison, those analytcs
sampled by the Task Force are listed in Table 18.
Tabic 22
Analytcs Reported by (Texaco) PARL Laboratory
Inorganics
Indicator Parameters
Organics
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Vanadium
Zinc
Cyanide
Phenols
Ammonia
Sulfate
Chloride
Conductivity
Benzene
Toluene
Ethylbcnzenc
Xylene
Where blanks occur in Table 21, the analyte was either below the level of
detectability, was not sampled for, or was not reported. These blanks can be
investigated further by review of raw data from the Task Force and Texaco in
Appendices A and I respectively. The capital letter "N" for the Task Force results
denotes a spike recovery not within control limits.
178

-------
Table 21
Analytical Comparison, Ground-Water Task Force vs Texaco
SAMPLE SOURCE
PROPRIETOR
LABORATORY
Acetone
Bentene
2-Butanone
Ethyl Benxene
Methylene ChLorLde
Toluene
Xylene
Phenol
M-l
TP
TEX
ACCU
M-6b
TP TEX
ACCU
M-lOs
TP
59
12
18
24
TEX
PARL
9260
M-lOd
TP	TEX
PARL
57
12
3240
TP
3806
310
670
410
330
64000
M-36
TP
DUP
3000
270
570
TEX
PARL
290
360	420
290	140
62000 226000
H-35
M-51As
TP
TEX
ACCU
TP
23
76
15
34
59
TEX
PARL
220
9670
NOTCx
TP - Task Porce (micrograms/liter)
TEX - Texaco (mllllgrams/llter converted to micrograms/I Iter)
H - Spike recovery not vlthln control limits
- Blank Indicates those concentrations below the lower limit of detection

-------
SAMPLE SOURCE	M-33
PROPRIETOR	TP	TEX
LABORATORY	ACCU
Acetone
Benzene
2-Butanone
EthyL Benzene
Methylene Chloride
Toluene
Xylene
Phenol	11
INLET POND
TP	TEX
PARL
20
20
90
Table 21 (continued)
M-12
TF	TEX
A CCU
11
3.2
36
ALLUVIAL POND
TF
TEX
PARL
SS-19
TF
2000
170
290
890
TEX
ACCU
290
SS-49
TF
6000
310
620
3000

-------
SAMPLE SOURCE
PROPRIETOR
LABORATORY
AceCona
Benzene
2-Butanone
Ethyl Benzene
Methylene Chloride
Toluene
Xylene
Phenol
SS-34
TP
JB
TEX
PARL
10
40
230
SS-7
TP
1400
180
4 60
TEX
ACCU
31
Table 21 (continued)
SS-4
TEX
PARL
820
40
50
240
4210
M-41A
TP
TEX
PARL
30
PCS POND
TP
12
5.5
27
TEX
PARL
920
BAILER BAILER
BLANK BLAlfK
TF
270
TEX
PARL
20
PlIHP PUMP BAILER BAIL!
BLANK BLANK BLANK BLAh
TP
390
19
TEX
PARL
90
TP
29
TE
PAI
IE

-------
Table 21 (continued)
SAMPLE SOURCE
PROPRIETOR
LABORATORY
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnejlura
Manganese
Mercury
Nlckle
Potassium
Selenium
Sliver
Sodium
Thalllura
Vanadlum
Zlna
INDICATOR PARAMETERS
Total Phenols
TOX
POX
TOC
POC
N03-N
NH3-N
N02-N
Chloride
Bromide
S04
Cyanide
M-l
914N
5920
26
3250
1200
270
300
1400
120000
TEX
ACCU
700
TF
neoN
12.3
36
18300 17000
780
5
5400
36
40
2600
206000 190000
2630N	3400
5000
300
400
130000
M-6b
t f
468
13.7
56
259000
2270H
6.7
87600
249
10600
208000
2950N
10
7800
TEX
ACCU
18
240000
12
50
6
2200
5
75000
210
0.1
60
10000
190000
3300
7000
300
4 00
280000 270000
750000 740000
M-lOs
TEX
PARL
30
70
190
60
1420
36710
140
14
120
320
1280
9260
37400
52000
2580000 2766000
121H	1700
TF
704H
15.5
53.6
81
568000
16
14800H
10.2
294000
49800
29
5230
141
196000
13
1090N
6000
36
69000
1510
19000
M-lOd
TF	TEX
PARL
37
193000
889H
121000
483
19300
519000
2.0
1660N
5500
6.4
300
87000
1900
370000
4 1 4 M
70
670
400
60
120
1660
3240
1330
98000
581000
2040
TF
3330N
12.9
196
106
8510
25
25
2690N
8
4220
112
257
8750
99. 2
151
120N
610000
100000
480000
M- 36
TF
DUP
2290K
10.2
229
106
8550
18
31
2750
6
4490
119
0.2
266
8800
73.5
939000 990000
153
34N
394000 284000
676000 726000
2600	2400
580000
80000
1400
540000
TEX
PARL
30
90
100
190
110
226000
407000
62000
330000
1020
M-35
TP
5510N
59
1.2
88100
3460
5.2
39600
279
0.4
11800
8.1
107000
36N
16000
3000
TEX
ACCU
4800
1 0
74000
40
3600
34000
320
0.2
30
10000
94000
9
35
4000
3300
18000 18000
290000 300000
H-51As
TP
20500N
79
411
7.1
26B000
44
55
224000
31
176000
2740
38
32000
2.3
316000
80
15900N
4200	9670
14
125000
280
8000 164000
50000 289000
1600
150000 291000
552	1550

-------
>9
TEX
PARL
2220
60
430
210
70
640
3110
6000
120
Table
21
(continued)
M-33
TF
3670N
3.2
47
224000
8
5360N
13. 5
112000
687
18400
420000
42H
41
25
16000
TEX
ACCU
5200
IB
200000
16
40
20
7700
12
98000
830
100
17000
6
390000
12
60
11
INLET PGND
24000
100
470	360
1100	200
7000	70000
550
74000	1100000
172N	150
TP
154
7.1
119
250000
1110
278000N
730N
7960
27.5
920000
39
18
16000
390
20000
190000
11500000
36
TEX
PARL
110
120
1290
670
90
50
220
320
1210
3408000
150000
250
SP-7
TF
5840H
10.9
135
77100
12
17400H
14.4
72600
2570
44
15400
456000
13
5200N
282
16
2 9000
5000
1800
80000
590000
145N
TEX
ACCU
4100
11
13
70000
11
15
20000
12
64000
2400
100
13000
420000
11
4800
34000
200
1200
72000
490000
120
M-12s
TF
1530N
31 .5
166
92400
8
12200
36.1
91700
1760
32
14800
38.3
2320N
198
36000
190
6000
4400
70000
500000
145N
TEX
ACCU
32
11
86000
40
13
10000
17
81000
1500
110
13000
467000 430000
6
1500
56
36000
200
5400
76000
490000
130
ALLUVIAL POND
TF	TEX
PARL
131
6.7
50
390
340
20
73900
252
58900N
357
12000
432000
9
32
13
16000
230
58000 1453000
250
970000 75000
450
50
SS-19
TF
2330N
14.4
1160
1 . 4
130000
20300N
11.1
80600
1620
0.2
4900
30N
207
12
7
33000
6100
14000
43000
600.
50000
20N
TEX
ACCU
1200
12
1300
9
110000
20000
72000
1500
50
4000
154000 140000
8
33
190
41000
15000
15000
41000
50000
18

-------
Table 21 (continued)
SAMPLE SOURCE

SS-34

SS-7

SS-4

M-41A
PCS
POKD
PROPRIETOR
TF
TEX
TP
TEX
TF
TEX
TF
TEX
TF
TEX
LABORATORY

PARL

ACCU

PARL

PARL

PARL
Aluminum
24900N

430N

347

113000N

311

Antimony
6.9









Arsenic
20.3



39.9
20
41

9.9

Barium
564
130
928
1100
1200
1060
1640
60
376
350
Berylllura






5



Cadmium






4.6



Calcium
172000

43900
40000
120000

398000

124000

Chromium
18
100



60
123
130

60
Cobalt
23





58



Copper
33





132
50


Iron
56700N

4870N
4500
52600

171000N

1580

Lead
140
770
6. 9
7

460
138
960

460
Magneslum
128000

79800
71000
62900N

207000

16800N

Manganese
2370
2260
874
750
797N
860
5100
2170
625N
590
Mercury






0.7



NLckle

80

50


89
110


Potasslum
10800

3360
3000
4190

23500

8250

Selenium
2.8





6.2



Silver







50


Sodium
160000

112000
110000
127000

154000

102000

Thallium










Vanadium
72
1 60



80
309
200

80
Zinc
220N
360
2120N
2200
1870
1720
861N
560


INDICATOR PARAMETERS










Total Phenols

230
76
33
109
423
33
30
9754
920
TOX
11

20

17

9.9

12

POX


7







TOC
10000

25000

48000

5700

39000

POC
650

4900
9600
12000

620

420

N03-N


1000



910



NH3-N
4 200
4310
130
300
400
2930




N02-N










Chloride
35000
405000
31000
31000
90000

26000
752000
120000
122000
Bromide
600



550



250

S04
350000
54000
480000

5700
75000
1000000
40000
1000000
55000
Cyanide

1000


20
260

60

70
BAILER BAILER
BLANK BLANK
IF
TEX
PARL
277
431
43
20
1180
90
PUMP PUMP BAILER BAIL!
BLANK BLANK BLANK BLAJ
TP
TEX
PARL
533
394
16
5
1300
90
2260

-------
eval-B
Based on the QA/QC data validation reports discussed previously and presented in
Appendices G and H, all analytical data reported for organics and inorganics arc
within the program accuracy Data Quality Objectives. Based on this conclusion
the following discussion compares the Task Force data to Tcxaco's data. For ease,
this is broken up into organics, metals and indicator parameters as they are
presented in Table 21.
Organics
Table 21 shows the occurrence of acetone in five samples by the Task Force but
not detected by Texaco. Concentrations appear to be low in all samples except at
M-36 where 3000 to 3806 ug/1 concentrations were detected. Lower concentrations
may be attributed to sample handling contamination, although the concentrations
in M-36 may be associated with degradation of petroleum waste constituents. At
this time the relationship between acetone and petroleum waste degradation is not
well understood. Samples analyzed by Texaco compare favorably with all other
organic constituents except phenol with only slight discrepancies. Phenols arc
consistently detected by both of Tcxaco's laboratories, while the Task Force data
reported concentrations above the detection limit only once. This was at well M-
36, but even then the Task Force results did not compare favorably with Tcxaco's
(see Table 21). Total phenol concentrations listed under Indicator Parameters in
Tabic 21 for the Task Force appear to compare more favorably to Tcxaco's,
although apparent discrepancies do exist. It is apparent that two different types of
methods and possibly laboratories analyzed for phenols and/or total phenols, thus
possibly explaining the variation between the Task Force and Texaco results. The
Texaco data presented in both columns under phenols is the same concentration
(i.e. repeated on the Table by the Task Force).
Metals
Metals analyzed by both Texaco and the Task Force show some discrepancies. In
addition, some parameters at various wells exceed the primary drinking water
standard (PDWS). A brief summary of notable discrepancies and cxcccdancc to
standards follows:
o Values for arsenic appear to compare favorably between Texaco and the
Task Force except at well M-36. Arsenic as reported by either Texaco
and/or the Task Force exceeded the PDWS of 0.05 mg/1 at wells M-lOs, M-36
and M-51As.
o Discrepancies were seen in barium concentrations at wells M-51As, SS-34
and M-41A. Wells where barium exceeded the PDWS of 1.0 mg/1 as reported
by the Task Force and/or Texaco include SS-19, SS-49, SS-7, SS-4 and M-
41 A.
o Discrepancies in cadmium concentrations were seen at wells M-35 and SS-19,
and then only slightly. Wells where the PDWS of 0.01 mg/l for cadmium
was exceeded include M-6b, M-33, SP-7, M-12s, and M-35.
o Numerous discrepancies in chromium concentrations were detected in most
wells. It appears that chromium was consistently detected by Texaco's labs
and not by the Task Force. No reason for this discrepancy could be given.
The PDWS for chromium of 0.05 mg/1 was exceeded in wells M -10s, M-lOd,
M-51As, SS-49, SS-34, SS-4, M-41A and the PCS, inlet and alluvial ponds.
185

-------
eval-B
o Notable discrepancies in lead concentrations were also seen in numerous
wells including M-lOs, M-lOd, M-51As, SS-49, SS-34, M-41A and the PCS,
inlet and alluvial ponds. General trends indicate that Texaco's
concentrations are usually higher and at several wells, Texaco detected high
concentrations and the Task Force reported non-detectable. Those wells
which exceed the PDWS for lead of 0.05 mg/1 include M-lOs, M-lOd, M-51As,
SS-49, SS-34, SS-4, M-41A and the PCS, inlet and alluvial ponds.
o Discrepancies in nickel concentrations were seen at wells M-lOs, M-51As, SP-
7, and M-12s. Again, on several occasions the Task Force data was lower
and even non detected in several wells while Texaco reported
concentrations.
o Results for selenium compared favorably except at well M-lOs where
Texaco's value was much less than the Task Force's. The PDWS for
selenium of 0.01 mg/1 was exceeded in wells M-lOs, M-36, M-12s and the
inlet pond.
o Several discrepancies in silver concentrations were noted in that while
Texaco reported values, the Task Force results were below the detection
limit. Silver concentrations exceeded the PDWS of 0.05 mg/1 at wells M-lOs,
M-51As, M-41A and the inlet pond.
o Several discrepancies in vanadium concentrations were seen. For the most
part, Texaco's values were consistently higher than the Task Force results
and were also detected at times when the Task Force reported non-
detectable.
Indicator Parameters
Only those indicator parameters for which discrepancies were noted arc discussed
below.
o Several discrepancies were noted in the total organic carbon (TOC)
concentrations, especially at wells M-l and M-35. Other discrepancies,
although slight, may be attributed to the detection of TOC in the pump and
bailer blanks by the Task Force.
o Other indicator parameters tend to compare favorably where reported by
Texaco and the Task Force except as noted. Ammonia (N) was reported by
Texaco in M-51As at 25 times the concentration reported by the Task Force.
Bromide was detected in ten samples taken by the Task Force, but was not
reported in any samples by Texaco. The cyanide results are interesting in
that the concentrations detected by Texaco are consistently higher than
those reported by the Task Force.
In summary, the analytical results reported show several discrepancies as noted
above. General observations would be that for several inorganic parameters, it
appears that Texaco is reporting consistently higher concentrations than the Task
Force. In fact for several analytes, the Task Force often reported concentrations
below the lower limit of detection while Texaco reported concentrations
186

-------
eval-B
significantly above the detection limit. For both parties, analytical results indicate
that numerous analytcs exceed the PDWS set forth in 40 CFR 265 Appendix III as
discussed previously.
In the future, field blanks and/or reporting of internal QA/QC procedures utilized
by Texaco's laboratories would assist in assessing the confidence of the reported
analytical results. As previously mentioned, this field and laboratory QA/QC
program should be discussed in detail in the sampling and analysis plan, and
should be implemented in the field to assure that data quality objectives are met.
This is especially important in reviewing data for an evaluation of the
effectiveness of any type of remedial action program, especially when evaluating
background ground-water quality.
4. Comparison to Past Texaco Data
Minimal data exist for comparison of past Texaco data with those of the Task
Force. As previously mentioned, only three "comprehensive" sampling events in the
North Area were performed by Texaco prior to the Task Force evaluation. Two
sampling events in 1984 were analyzed for priority pollutants and one event in
1986 for the modified Skinner list (TriHydro, 1987a). A comprehensive sampling
event has not been performed in the South Area.
The following constituents were chosen for comparison: benzene, toluene, phenol,
2,4-dimethylphcnol and 2-butanonc (methyl ethyl ketone). These were chosen
because they occurred or were at least analyzed more often than other organic
constituents. Furthermore, data comparisons could only be made in the following
wells: M-lOs, M-lOd, M-33, M-35, M-36, M-51As and SP-7, as these were the only
wells sampled by both the Task Force and Texaco in the past.
The above mentioned constituents were either not analyzed or not detected above
the detection limit in both sampling events held by Texaco in 1984. Additionally,
Texaco did not analyze or detect above the lower detection limit any constituents
except in well M-36 in June, 1986. It should be noted that this is based on the
previously mentioned wells only. Contamination was detected in other wells by
Texaco, but for comparison purposes, will not be reviewed. Table 13 contains
Texaco's summary table listing the constituents detected in the past and the
associated wells.
In comparing Texaco's past organic data with the Task Force, no significant
deviations or trends were observed. All the above mentioned constituents were
detected in well M-36 by both parties in similar concentrations. Benzene was
reported at 230 ug/1 by Texaco and 310 ug/1 by the Task Force. Toluene
concentrations were 330 ug/1 for Texaco and 410 ug/1 from the Task Porce. Both
parties reported 64,000 ug/1 of phenol. 2,4-dimethylphcnol was reported at 25,000
ug/1 by Texaco and 14,000 ug/1 by the Task Force. Finally, 2-butanone (methyl
ethyl ketone) concentrations were 520 ug/1 as reported by Texaco and 670 ug/1 by
the Task Force.
To be consistent with the organic comparison, only June, 1986 inorganic data will
be compared with the Task Force data. Only those wells which were sampled and
analyzed by both parties are included. In addition, only those inorganic
parameters which exceed drinking water standards during Texaco's June 1986
analysis were reviewed.
187

-------
eval-B
Nitrate was reported by Texaco in M-lOs at 16,000 ug/1, while the Task Force
reported 1,500 ug/1. Selenium exceeded the standard in two wells by both Texaco
and the Task Force. Well M-12s showed concentrations of 100 and 38 ug/1 for
Texaco and the Task Force, respectively. Well M-36 concentrations were 30 and 90
ug/1, respectively. Cadmium was reported by Texaco in well M-33 at 20 ug/1, but
not detected by the Task Force. Finally, arsenic concentrations from well M-36
were 200 ug/1 from Texaco and 196 ug/1 from the Task Force.
188

-------
eval-B
F. REFERENCES
Barcelona, M.J.; Gibb, J.P.; Miller, R.A., 1983, A Guide to the Selection of Materials for
Monitoring Well Construction and Groundwater Sampling, Illinois State Water
Survey, SWS Contract Report 327.
Crist, M.A.; Lowry, M.E., 1972, Ground-Water Resources of Natrona County, Wyoming:
U.S. Geol. Survey Water-Supply Paper 1897.
Feathers, K..R.; Libra, R.; Stephenson, T.R., 1981, Occurrence and Characteristics of
Ground Water in the Powder River Basin, Wyoming; Water Resources Research
Institute, University of Wyoming, Report to U.S. Environmental Protection Agency,
Contract Number G-008269-79.
Groundwater Technology, Inc., 1983-1985, Quarterly Reports of Oil Recovery Operations
at Texaco, Casper, Wyoming Refinery, First Through Ninth Quarterly Reports.
Hamilton, F.C., Personal Communication, 1988.
Headley, J.B., Jr., 1958, Oil in Mesaverde, Powder River Basin, Wyoming. In Guidebook,
Wyo. Geol. Assoc. 13th Ann. Field Conf.
Hodson, W.G.; Pearl, R.H., and Druse, S.A., 1973, Water resources of the Powder River
basin and adjacent areas, northeastern Wyoming: U.S. Geol. Survey Hydrologic
Investigations Atlas HA-465.
A.T. Kearney, Inc., 1986, RCRA Facility Assessment of the Texaco Refinery, Casper,
Wyoming, October 1986.
Purccll, T.E., 1961, The Mesaverde Formation of the Northern and Central Powder River
Basin, Wyoming: in. Wyoming Geol. Assoc. 16th Ann. Field Conf.
Rocky Mountain Association of Geologists, 1972, Geologic Atlas of the Rocky Mountain
Region, A.B. Hirschfeld Press, Denver, Colorado.
Texaco Casper Refinery (Texaco), 1983, Closure and Post-Closure Plans, June 9, 1983.
Texaco Casper Refinery (Texaco), 1985, Part B Permit Application for the North Land
Farm, November 5, 1985.
TriHydro Corporation (TriHydro), 1987a, Casper Plant North Landfarm Reconnaissance
Investigation Report, June 15, 1987.
TriHydro Corporation (TriHydro), 1987b, Casper Texaco Refinery North Landfarm 1986
Annual Report, July I, 1987.
U.S. Environmental Protection Agency, 1986a, RCRA Ground-Water Monitoring Technical
Enforcement Guidance Document, Final, September 1986.
U.S. Environmental Protection Agency, 1986b, RCRA Inspection Report, July 15, 1986.
U.S. Environmental Protection Agency, 1986c, Project Plan Ground-Water Monitoring
Compliance Evaluation, Hazardous Waste Ground Water Task Force, Texaco Inc.,
Casper, Wyoming, August 1986.
189

-------
eval-B
Western Water Consultants, Inc. (WWC), 1981, Casper Texaco Refinery Sampling and
Analysis Plan, November 19, 1981.
Western Water Consultants, Inc. (WWC), 1982a, Casper Texaco Refinery Sampling and
Analysis Plan Addendum, May 5, 1982.
Western Water Consultants, Inc. (WWC), 1982b, Geology and Hydrogeology of the Part of
the Casper Refinery south of the North Platte River, August 2, 1982.
Western Water Consultants, Inc. (WWC), 1982c, Occurrence and Control of Hydrocarbon
Seeps along the South Bank of the North Platte River, Casper Texaco Refinery,
October 1, 1982.
Western Water Consultants, Inc. (WWC). 1982d, Casper Texaco Refinery North Property
Monitoring Plan, October 15, 1982.
Western Water Consultants, Inc. (WWC), 1983a, Casper Texaco Refinery North Property
Ground-Water Pollution Abatement Plan, November 30, 1983.
Western Water Consultants, Inc. (WWC), 1983b, Application for Permit to Construct
Hydrocarbon Recovery Project, Casper Texaco Refinery, March 25, 1983.
Western Water Consultants, Inc. (WWC), 1983c, Addendum to Application for Permit to
Construct Hydrocarbon Recovery Project, Casper Texaco Refinery, Prepared by
Groundwater Technology, June, 1983.
Western Water Consultants, Inc. (WWC), 1984a, Casper Texaco Refinery North Property
Ground-Water Pollution Abatement Program, 1983 Annual Report, March 1, 1984.
Western Water Consultants, Inc. (WWC), 1984b, Organic Characterization of the Ground
Waters of the North Property Casper Texaco Refinery (Fall 1984 Update),
November 27, 1984.
Western Water Consultants, Inc. (WWC), 1985, Casper Texaco Refinery North Property
Ground-Water Pollution Abatement Program, 1984 Annual Report, February 28,
1985.
Western Water Consultants, Inc. (WWC), 1987a, Casper Texaco Refinery North Property
Ground-Water Pollution Abatement Program, 1986 Annual Report, March 25, 1987.
Western Water Consultants, Inc. (WWC), 1987b, Texaco Refining and Marketing Inc. Casper
Plant Investigation of Groundwater Contamination Beneath the Southeast Corner
of Casper Plant, Interim Report Based on Data Collected through September 1987,
October 9, 1987.
Western Water Consultants, Inc. (WWC), 1988, Texaco Casper Refinery North Property
Ground-Water Pollution Abatement Program, 1987 Annual Report, February 29,
1988.
Wiloth, G.J., ed., 1961, Symposium on Late Cretaceous Rocks, Wyoming and Adjacent
Areas: Wyoming Geological Association 16th Ann. Guidebook.
190

-------
Effects of Chemical Evaporation Pond Recharge
The Chemical Evaporation Pond (CEP) was operated at the North Area from 1955 to
August 1982. The pond received wastewater from the process system, including the Hydro
Treater Unit (HTU), Catalytic-Polymerization Unit (Poly), Fluid Catalytic Cracking Unit
(FCCU), Pressure Coke Stills (PCS), Vacuum Pipe Stills (VPS), Catalytic Reforming Unit
(CRU), and Stabilizers. The process water system also received 138 tons of caustic soda
per year from the mcrox system. Flow from the FCCU and PCS accounted for 50-60% of
the waste stream to the pond; the Poly, HTU, CRU, and VPS contributed about 30-40% of
the waste stream; and the stabilizers contributed about 10% (WNVC, 1983a). An analysis of
the quality of the waste waters is shown on Table 8.
In October of 1986, in an effort to augment contaminant degradation in the uppermost
aquifer near the CEP, Texaco constructed a recharge pond from the southern third of the
old CEP and began recharging the ground-water system with relatively clean water from
the North Platte River.
The location of the CEP is shown on Figure 10. The pond had a surface area of 6.62
acres, and a maximum capacity of 16 million gallons. Seepage from the pond has been
identified as the primary source of ground-water contamination in the North Area (NVWC,
1983a). Contamination identified as originating from the pond includes TOC, pH,
conductance, lead, chromium, selenium, phenols, ammonia, sulfide, and chloride, based on
comparisons to National Interim Primary Drinking Water Standards, RCRA indicator
parameters, and Wyoming Water Quality Criteria (WWC, 1983a). In addition, a number of
hazardous organic constituents have been identified in wells near the CEP during
sampling in 1984 and 1986.
In December 1982, Texaco ceased discharging process wastewaters to the CEP and
implemented a program to abate ground-water pollution resulting from previous operation
of the pond. Water remaining in the pond was treated by mechanical aeration from
December 1982 until November 1983, and the treated water was then discharged to the
Excess Service Water Effluent Ponds (WWC, 1984a). In October 1986, the sludge and some
of the soil from the bottom of the CEP was removed to the North Land Farm as part of
CEP closure (WWC, 1987a). Texaco was also relying on the natural processes of dilution,
sorption, and biodegradation to attenuate ground-water contamination in the vicinity of
the CEP (WWC, 1983a). Although Texaco investigated the viability of sorption and
biodegradation to attenuate contaminant concentrations, they concluded that dilution
would remain the principal means of attenuation (WWC, 1983a). Texaco monitored the
progress of contamination abatement through a program of quarterly sampling of
indicator parameters and water levels.
In October of 1986, in an effort to augment contaminant degradation in the uppermost
aquifer near the CEP, Texaco constructed a recharge pond from the southern third of the
old CEP and began recharging the ground-water system with relatively clean water from
the North Platte River. About 8.8 million gallons of water were pumped into the pond
between October and December 1986 (WWC, 1987a), and about an additional 35 million
gallons were pumped into the pond in 1987 (WWC, 1988), or the relative losses from the
pond due to evaporation and infiltration into the ground-water aquifer. However, no
recharge occurred during the winter of 1986-87, when the pond was frozen (Hamilton,
personal communication, 1988).
1

-------
ATTACHMENT

-------
Table q Quality 0f Waste Streams Feeding Chemical Evaporation Pond, Casper Texaco Refinery
Units Containing
Flow TOS pli Phenol Irnn TOC Ammonia	II^S
	;	(maZJJ	IinaZU	("Ml/P ("'fl/D	(mu/i)	(mg/l - H) (mq/l)
FCCU & PCS	16	9.2	179	0.99	260	2022
Poly, IITII, CniJ,
and VPS	101	7.0 26	0.10	251	3250	7007
Stabilizers	2000	9.0 12.6		769	G15
Note: Analyses are an average of three samples from lite FCCII and'PCS and arc an average of two
samples from the other two waste streams. All samples were taken between May 14 and
June 1, 1901.
-- No Analyses
Source: WWC, 1983a

-------
512-eff
a 1 h
Hydraulic Effects of CEP
In addition to the degradation of ground-water quality noted above, the CEP also had a
significant effect on local ground-water levels and ground-water flow directions. As a
result of seepage from the pond, a distinct ground-water mound was established in the
immediate vicinity of the pond. In the absence of the pond, the estimated potcntiomctric
surface elevation beneath the pond would range from 51 15 feet msl on the south, to 5118
feet msl on the north (WWC, 1983a). However, at the time the CEP was taken out of
service in 1982, the potcntiomctric surface beneath the pond was in excess of 5124 feet
msl (WWC, 1984a). The apparent mound in the potcntiomctric surface was approximately
1500 feet in diameter, and extended beneath essentially all of the CEP, the landfill to the
west, and the land farm to the cast. When recharge to the pond ceased in 1982, the
mound began to decay, and potcntiomctric levels began to fall in the vicinity of the CEP.
By the autumn of 1986, potcntiomctric levels beneath the pond had declined to
approximately 5120 feet. An apparent mound still existed, but its diameter had been
reduced to about 800 feet (WWC, 1987a). With the onset of river water recharge in late
1986, the mound was quickly reestablished. By June 1987, potcntiomctric levels beneath
the recharge pond had risen to more than 5126 feet (and in excess of 5128 feet at well M-
11s). The diameter of the apparent mound had increased to about 1200 feet.
Furthermore, a review of the potcntiomctric level data for 1987 (WWC, 1988) indicates
considerable variability in water levels during the year. At well M-lls (Figure 10), where
maximum water levels were recorded, the water levels varied by more than four feet
during the course of the year. Furthermore, a continual water level rise was not observed.
The potcntiomctric level at well M-l Is was about 5121 feet prior to recharge, rose to
about 5127 feet by December 1986, fell to 5124 feet by March 1987, rose to in excess of
5128 feet by June 1986, and then fell to about 5126 feet by December 1986. These data
suggest two things: first, potcntiomctric levels in the immediate vicinity of the recharge
pond arc very sensitive to the input of water at the pond; and second, it appears that the
infiltration of water from the pond may be quite variable throughout the year, with a
large proportion of recharge to the ground-water system occurring in late spring and early
summer of 1987. No details on the operation of the system arc available from which
these conclusions could be confirmed, other than the cessation of recharge during the
winter of 1986-87, when the pond was frozen. Reportedly, the recharge pond is operated
so that a constant head is maintained in the pond (Hamilton, personal communication,
1988).
It should also be noted that water level fluctuations at well M-36 have been anomolous
from the time the well was installed in 1984. Western Water Consultants (WWC, 1988), in
their potentiometric level map for June 1987, indicate a localized depression in the
potentiometric surface in the vicinity of well M-36. However, water levels at this well
have continuously been depressed slightly with respect to water levels at other nearby
wells since water levels were first reported for the well in April 1984. Furthermore, as
water levels rose in response to recharge of river water at the CEP, the water levels at M-
36 rose more slowly than the levels at nearby wells. Texaco reports that the elevation of
this well is continually resurveyed (Hamilton, personal communication, 1988), so that it is
unlikely that the reported water level in this well is in error. Texaco also reports that
well M-36 does not recover abnormally slowly when the water level in the well is drawn
down (Hamilton, personal communication, 1988). As will be noted below, water chemistry
at M-36 has also not responded as directly as at other wells to the introduction of river
water at the recharge pond. This evidence suggests that well M-36 may be hydraulically
isolated in some manner from other nearby wells. A number of possible explanations for
this phenomenon can be suggested, ranging from plugging of the well screen to
installation of the well in a buried channel of high hydraulic conductivity. However, the
3

-------
512-eff
alh
available information docs not permit any definite conclusions to be drawn regarding the
apparently depressed water levels at well M-36.
Chemical Effects of the CEP
As noted previously, the use of the CEP prior to 1982 has been identified by Texaco as
the primary cause of ground-water contamination in the North Area. The pond has
apparently allowed the introduction of a wide range of contaminants, including several
hazardous constituents, into the uppermost aquifer. The mounding of the potcntiomctric
surface beneath the CEP also induced flow radially outward away from the CEP, with
some contaminated ground water apparently discharging from the uppermost aquifer at
the seeps along the bluff southeast of the CEP and subsequently entering the alluvial
aquifer downslope from the seeps.
Following cessation of discharge to the CEP in 1982, Texaco has documented general
declines in contaminant concentrations in the vicinity of the CEP. Texaco attributes
these declines to a combination of dilution of contaminated water with uncontaminatcd
water from upgradicnt; sorption of contaminants onto soil particles; biodegradation; and
other chemical degradation phenomena (WWC, 1984a, 1985, 1987a, 1988). However,
Texaco has provided few details as to the nature or relative magnitudes of these various
possible mechanisms for attenuation of contaminant concentrations. Early in the program.
Texaco did investigate the availability of microorganisms in ground water in the CEP
area, and did investigate the relative efficiencies of dilution and other degradation
mechanisms. They concluded that the ground water did contain microorganisms capable
of degrading some organic contaminants, although perhaps not within the ground water
immediately adjacent to the CEP where contaminant concentrations were very high. They
also concluded that whereas phenomena other than dilution were apparently effective in
attenuating concentrations, dilution was probably the principal mechanism (WWC, 1983a,
1.984a).
The recharge of relatively uncontaminatcd river water at the CEP beginning in late 1986
was expected to augment the rates of contaminant attenuation within the uppermost
aquifer. In addition to the obvious potential for concentration reduction due to increased
dilution, it was expected that the relatively oxygen-rich river water would enhance the
rates of aerobic microbial degradation of contaminants. One of the major objectives of
the Ground Water Task Force has been to assess whether the recharge of river water has
in fact enhanced the degradation of organic contaminants in the aquifer, or whether the
effects of such recharge have been largely the hydraulic ones of dilution and lateral
transport away from the recharge basin.
In an effort to assess the effectiveness of river water recharge in augmenting rates of
natural attenuation of contaminant concentrations, the Task Force has conducted a
variety of preliminary investigations, utilizing primarily data reported by Texaco,
supplemented where possible with data collected by the Task Force. These preliminary
investigations have included the following:
o Estimating the changes in total mass of various indicator chemicals in the system
as a function of time.
o Estimating the changes in total mass of individual organic contaminants in the
system as a function of time.
o Reviewing changes in contaminant concentrations as a function of time at
individual wells.
4

-------
512-eff
slh
o Reviewing the reported rates of decline of maximum quarterly concentrations of
various indicator chemicals.
o Assessing the rates of ground-water underflow beneath the CEP relative to the rate
of river water recharge.
o Reviewing the response of the ground-water mound to the recharge of river water.
The first assessment attempted by the Task Force was the consideration of variations in
the estimated total mass of contaminants in the system. For each of three indicator
species (chloride, TOC, and total phenols), the total mass in the system at any given time
was estimated from the isopleths reported by Texaco (WWC, 1984a, 1987a, 1988). For cacli
map of contaminant distribution, the area encompassed by different isopleths was
estimated, and the area enclosed by two successive isopleths was calculated. The area
enclosed by two successive isopleths was then multiplied by an estimate of the average
concentration within the isopleths, and then multiplied by an assumed average thickness
of the uppermost aquifer (25 feet) and an assumed effective porosity (25%), to yield an
estimate of total mass of that contaminant enclosed by the isopleths. The mass enclosed
by all of the successive pairs of isopleth lines was then summed to get an estimate of total
mass of that constituent in the uppermost aquifer. This process was complicated in some
cases by the fact that isopleths, as displayed by Texaco, often extended beyond the
boundary of Texaco property, although the isopleths were terminated at the property line.
In these cases, it was necessary to estimate the extent of the isopleths beyond the property
line (and in fact beyond the extent of available data). Any errors made in such
extrapolation of the available data would be expressed in the consequent estimates of
total mass in the system. In order to reduce the effects of this class of error, it was
necessary in some cases to limit the estimate of total mass to the mass contained within a
particular isopleth (e.g., the 50 mg/I.isopleth for chloride, TOC, and phenol).
Consequently, any mass occurring outside of this isopleth, or transported outside of the
previous location of this isopleth, will not be accounted for in the analysis.
This approach was also attempted for specific individual constituents for which sufficient
data existed to permit contouring of isopleths (benzene, toluene, and total crcsols).
However, since these constituents were observed in only three or four wells, accurate
contouring of the data was extremely difficult, and the resulting estimates of total mass
are not considered reliable. They will, however, be discussed here for the sake of
completeness.
Table 9 summarizes the resulting estimates of total mass of various constituents as a
function of time. For each constituent, the mass relative to that estimated for the system
in June 1984 is also given. In general, the chloride mass in the system remains somewhat
constant, in relative terms, from 1982 to 1986, and then declines somewhat in 1987. TOC
concentrations decline rather steadily from 1982 to 1986, and then seem to stabilize.
Phenol concentrations vary considerably, sometimes declining considerably in a year,
sometimes rising dramatically. Benzene mass declines from 1984 to 1986 at a rate
comparable to that for chloride. Toluene increases substantially from 1984 to 1986, and
total cresols decline by more than 50% from 1984 to 1986. In terms of absolute rates of
mass decline, chloride mass declined at an average rate of about 12 million grams per
year, TOC at a rate of about 17 million grams per year, phenols at a rate of about 13
million grams per year, and total cresols at a rate of about 28 million grams per year.
5

-------
17-Cbbp
Table 9
Estimates of Total Contaminant Mass in
Uppermost Aquifer. North Area
(106 grains)
Parameter 6/82
6/83
6/84
6/85
6/86
6/87
Chloride	232	252
(.943)* (1.024)
246
(1.000)
215
(.874)
192
( .780)
TOC
199	184
(1.276) (1.179)
156
(1.000)
162
(1.038)
126
( . 808)
126
(.808)
Phenols	79.2	78.7
(1.520) (1.511)
52 . 1
(1.000)
4 0.5',
(.777)
55.8
(1.071)
27 . 1
(.520)
Benzene
. 0885
(1.000)
. 0774
( . 875)
Toluene
. 124
(1.000)
. 166
(1.339)
Cresols
80. 2
(1.000)
35.9
( . 448)
* Mass relative to that in the system in June 1984

-------
512-eff
alh
The results of these analyses are somewhat inconclusive. In terms of relative annual
changes in concentrations, chloride remains relatively constant from 1982 until 1986. and
then declines somewhat with the onset of river recharge. Since chloride is a conservative
and relatively non-reactive species, this is as would be expected. The decline in total
concentration between 1986 and 1987 can be attributed to the lateral transport of
chlorides beyond the 50 mg/1 isoplcth, and thus not considered in the analysis. The
gradual decline in TOC mass from 1982 to 1986, and the average rate of mass decline
which is about 40% higher than that for chloride, may be attributed to degradation
phenomena other than dilution. However, the apparent stabilization of mass from 1986 to
1987 is anomolous, and suggests at the least that the recharge of river water did not
accelerate the degradation of TOC. The variation in phenols was not very consistent,
although there is an overall trend of declining mass at a rate comparable to that for
chloride. The approximately 50% decline in total mass of phenols from 1986 to 1987 may
be attributed to the operation of the recharge pond, and is greater than the mass decline
in chlorides or other species, and thus might indicate enhanced degradation of phenols.
However, a comparable relative decline in total crcsols was observed from 1984 to 1986,
prior to the onset of river water recharge. In terms of absolute rates of annual decline in
mass, chloride, TOC, and phenols all declined at approximately equal rates, while total
crcsols declined at a rate approximately twice that of the other parameters. With the
possible exception of phenols, no acceleration in the rate of mass decline was observed
with the onset of river water recharge.
In general, the results of this analysis suggest the possibility that degradation phenomena
beyond mere dilution may be acting to reduce the concentrations of some contaminants,
but the evidence is not very clear, and on the basis of the absolute rates of estimated mass
decline, it appears that TOC and phenols decline at approximately the same rates as
chloride, and thus probably subject to much the same phenomena.
A second line of analysis attempted by the Task Force involved reviewing changes in
contaminant concentrations as a function of time at individual wells. With the onset of
river water recharge, a few wells experienced declines in contaminant concentrations,
many wells exhibited no immediate response, and some wells exhibited increases in some
indicator parameters. Significant declines in TOC and phenols concentrations with the
onset of recharge were observed at wells M-49A and M-9s; declines in TOC and phenols
concentrations at well M-lls were observed, although they did not begin until June 1987.
Chloride concentrations also declined significantly at well M-49A, but not nearly so
significantly at wells M-9s or M-lls. At wells M-36, M-51As, and SP-1, none of the
indicator parameters considered (TOC, phenols, and chlorides) appeared to respond to the
river water recharge, remaining at approximately the same levels as they had been during
1986. At two of the wells considered, M-13 and M-8sa, the river water recharge seems to
have induced a temporary increase in the levels of indicator parameters. At both of these
wells, TOC, phenols, and chloride concentrations generally rose from September 1986 until
June 1987, and then began to decline.
The results of this phase of the Task Force assessment indicate that with the onset of
river water recharge, concentrations of indicator parameters generally declined at wells
closest to the recharge pond, temporarily rose at wells a little further away, and were
essentially unchanged at wells beyond about 750 feet from the recharge pond. This
evidence suggests that the principal effect of the river water recharge was a dilution of
contaminated water immediately beneath the pond, accompanied by a lateral "flushing" of
contaminated water away from the recharge pond as the ground-water mound beneath the
pond was reestablished. Although the recharge of oxygenated river water may have
enhanced aerobic biodegradation, the effects of any such activity would appear to be
largely outweighed by the effects of dilution and lateral transport, to the extent that the
7

-------
512-efT
slh
possible effects of other degradation phenomena can not be clearly seen in the data
considered.
Texaco (Hamilton, personal communication, 1988) has also considered variations in sulfate
concentrations as a possible indicator of biodegradation activity, with a rise in sulfate
concentrations possibly indicating aerobic biodegradation of sulfides, and a decrease in
sulfates suggesting anaerobic biodegradation. In general, however, it is difficult to
observe any distinct changes in sulfate concentrations corresponding to the onset of river
water recharge at the CEP, except for decreases in sulfate concentrations at wells M-lOs
and M-lOm, and increases in sulfates at wells M-17 and M-19. All four of these wells arc
downgradicnt of the CEP and to its cast, with wells M-17 and M-19 located further
downgradient than wells M-lOs and M-IOm (Figure 10). Since the trends in these changes
in sulfate concentrations arc contrary to what would be expected with increased aerobic
biodegradation near the pond, and since even wells closer to the pond showed no definite
correlations of sulfate with river water recharge, it is not possible to assert that recharge
of aerated river water enhanced biodegradation based on this evidence.
The Task Force also reviewed the reported rates of decline of maximum quarterly
concentrations of various indicator chemicals (WWC, 1985, 1987a, 1988). According to
Texaco, these maximum quarterly concentrations continued to decline, even through 1987,
although the rates of decline as calculated by Western Water Resources (1985, 1987a, 1988)
were decreasing in some cases. Upon closer inspection of the reported data, it appears
that the quarterly maxima for several parameters (TOC, phenols, sulfide, and chloride)
have actually stabilized since about 1985, with no apparent effect of river water recharge.
Ammonia and conductance maxima appear to have remained fairly steady since 1982,
although the maxima for both of these parameters declined late in 1987. Again, these
trends would be consistent with dilution and lateral transport as the primary mechanisms
of contaminant attenuation, with no apparent enhancement of contaminant degradation as
a result of river water recharge. The apparent stabilization of quarterly maxima might
reflect a gradual outward transport of contaminants, with no continuing attenuation of
concentrations by means of any phenomena.
Finally, as noted previously, the ground-water mound beneath the CEP has responded
immediately and directly to the recharge of river water. This is not surprising, since it
appears that the rate of recharge of river water far exceeds the rate of natural ground-
water underflow beneath the area of the CEP. Average recharge of river water during
1987 was 35 million gallons over the course of the year, or about 100,000 gallons per day.
Natural underflow is difficult to estimate because of the absence of ground-water level
data unaffected by the CEP, and because of the wide variation in estimated hydraulic
conductivity of the "eolian" sands (ranging from 1.5 to 1067 gpd/ft (WWC, 1983a). Based
on the potentiometric contours for June 1987 (WWC, 1988), the water-level gradients to the
southeast and southwest, relatively unaffected by the CEP, are about 0.02 (the estimated
gradient beneath the CEP following total decay of the ground-water mound was about
0.006 (WWC, 1983a). It should be noted that the maximum estimated values of hydraulic
conductivity are for well M-49a, the tested well nearest the CEP (Figure 10). Excluding
data for this well, the mean hydraulic conductivity measured for the "eolian" sands in the
area unaffected by the CEP (the area where the gradient was estimated) would be 14
gpd/ft . For an assumed gradient of 0.02, hydraulic conductivity of 15 gpd/ft2, and
aquifer thickness of 25 feet, the underflow through a cross section 2400 feet wide (the
approximate width of the estimated phenol plume in 1986) would be about 18,000 gpd.
Thus, it appears that natural underflow beneath the CEP may be as low as 20% of the
annual average recharge of river water. Even if the estimated rate of ground-water
underflow were increased by an order of magnitude, the rate of river water recharge
would remain more than 55% of the underflow. This again suggests that dilution and
8

-------
512 - off
slh
lateral transport of contaminants away-from the reestablished water-level mound may be
the major phenomena affecting contaminant attenuation in the vicinity of the CEP.
Recommendations
These preliminary Task Force calculations suggest the variety of analyses that could be
brought to bear on the question of attenuation of ground-water contamination in the
North Area. Although Texaco maintains that several mechanisms for attenuation of
contaminants may be at work in the North Area ground-water system (WWC, 1983a, 1984a,
1985, 1987a, 1988; Hamilton, personal communication, 1988), analyses of the data to
support this contention has largely been limited to documenting long-term trends in
declining constituent concentrations. Attempts at quantification of the relative effects of
dilution, hydrogeochemical, and hydrobiological phenomena have apparently not been
consistently applied. In order to permit a rational assessment of the potential for river
water recharge to enhance natural attenuation mechanisms, it is recommended that Texaco
provide quantification and discussion of the relative effects of all possible attenuation
mechanisms.
9

-------

B
w*t
o'
Eoil
Generalized Hydrogeologic Cross Sections
Casper Texaco Refinery

-------
North
  ir>' *
C
South
	PLATE 1	
Generalized Hydrogeologic Cross Sections
Casper Texaco Refinery

-------