fColiection
!
JTCe Center
I
.9107
j
UnlBd States
E nwomnental Pro lecnon
Agefw;y
Office of
E~rgency arod
Remedial Response
E P AlROOtRQ8.9OiQ33
Sepl&mber 1990
1)
oEPA
Superfund
Record of Decision:
I~
fB"fl.. 1'L/4al
'--
I~
4
Mystery Bridge at
Highway 20, WY
~.- u.s. E.~A. Regionl ...,
HPJ7~rt1ml~ 'M"It'+f\ Tf'\~",.,i~At Inro Ctr
-------
f'
REPORT DOCUMENTATION I"~ AEPOATNO. 1 ~ 1 A8cjp8tII' 8 Acc8Mion No.
PAGE EPA/ROD/R08-90/033
4. 1118 end ...... L A8part on.
SUPERFUND RECORD OF DECISION - 09/24/90
Mystery Bridge at Highway 20, WY
First Remedial Action I.
7. AuIIOfi8) I. P8rtotmIng OroenlDtion A8pL No.
8. ~ OrQ8lnll8tlon ....... end AddrM8 10. ,",ojec1lT88luWortL UnIt No.
11. ConIr8C'CC) or QnnI(G) No.
(e)
(Q)
12. ---. OrprU8l!on ....... end .-- 11. Type of A8part . P8fIocI eo--
U.S. Environmental Protection Agency 800/000
401 M Street, S.W.
Washington, D.C. 20460 14.
15. " ..' .........., No-
II. AbA'8Ct (IJn1It: 2011--)
The Mystery Bridge at Highway 20 site is an industrial area with two onsite
residential subdivisions, in Natrona County, one mile east of Evansville, Wyoming. A
portion of the site lies within the 100- and 500-year floodplains of the North Platte
River and Elkhorn Creek. Two plan~s are located at the site: the DOW/DSI facility,
an oil and gas production enhancement service facility; and the KN plant, which is a
natural gas fractionation, compression, cleaning, odorizing and transmission plant.
The site overlies a contaminated alluvial aquifer, which was previously used as a
source of potable water. Probable sources of onsite ground water contamination
include contaminant releases from a Dow/DSI truck wash water system, which is
comprised of an oil/water separator, a vitreous tile drain, and a leach sump system;
and an onsite toluene storage area. In 1965, an underground pipe burst, releasing
5,000 to 10,000 gallons of absorption oil from the KN facility into the soil. From
1965 to 1987, ~ flare pit was used by KN to collect spent materials and wastes, and an
onsite catchment area was used to collect the contaminated surface runoff and steam
condensate from a dehydration unit. From 1965 to 1987, several small contaminant
releases occurred near the flare pit and catchment area. In 1987, site investigations
(See Attached Page)
17. ~ AnIIy8I8 .. ~.....
Record of Decision - Mystery Bridge at Highway 20, WY
First Remedial Action
Contaminated Medium: gw
Key Contaminants: VOCs (benzene, PCE, TCE, toluene, xylenes)
b. ........,Opa..&.-s T-
Co CC8A11 ~
II. A""""""'" '" 88cUrItY CI88 (1N8 A8parO 21. No. of"""
None 107
2IIL 88cUrItY CI88 (1N8 P8g1. 22. Prtc8
NonA
(1188 ANIII-Z3I.I'.
11881n8frUd- 011--
(For-'Y ~)
0.,-"-" of eo--
50212.101
-------
EPA/ROD/R08-901033
Mystery Bridge at Highway 20, WY
First Remedial Action
Abstract (continued)
revealed the presence of aromatic hydrocarbons in the soil in this area. Additionally,
ground water sampling revealed the presence of two contaminated ground water plumes
originating from the Dow/DSI the BET X plume and KN (VHO plume) facilities,
respectively. The BET X plume consists of aromatic hydrocarbons including toluene, and
xylenes, while the VHO plume consists volatile halogenated organics and chlorinated
organics. From 1988 to 1989, both Dow/DSI and KN conducted removal actions, which
included remediation of approximately 440 cubic yards of contaminated onsite soil using
vapor extraction; excavation and landfilling of contaminated soil and removal of the
separator, a waste oil tank, and part of the vitreous tile drain at the Dow/DSI
facility; and ground water treatment at the KN plant. This Record of Decision (ROD)
addresses remediation of the bnsite ground water emanating from the Dow/DSI and KN
facilities; the VHO and BETX plumes respectively. Further cleanup of the remaining
source areas will be addressed in a subsequent ROD. The primary contaminants of
concern affecting the ground water are VOCs including benzene, PCE, TCE, toluene, and
xylenes.
The selected remedial action for this site includes pumping and treatment of ground
water in the VHO plume followed by air stripping of ground water in the more
contaminated upgradient portion of the plume, and natural attenuation in downgradient
portions of the plume; pumping and treatment of ground water in the BETX plume using
air stripping; reinjecting the treated ground water from both plumes into the onsite
alluvial aquifer; ground water and air monitoring: and implementing institutional
controls including deed and ground water use restrictions. The estimated present worth
cost for this remedial action is $601,739, which includes an annual O&M cost of
$122,914 for 6 years at the VHO plume, and $50,564 for 1 year at the BETX plume.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific ground water cleanup goals are based
on Safe Water Drinking Act MCLs and include benzene 5 ugll (MCL), toluene 2000 ug/l
(proposed MCL), and xylenes 10,000 ug/l (proposed MCL).
-------
RECORD OF DECISION
MYSTERY BRIDGE ROAD/U.S. HIGHWAY 20 SUPERFUND SITE
OPERABLE UNIT 1 . GROUND WATER
SEPTEMBER 24, 1990
DECLARATION STATEMENT
SITE NAME AND LOCATION
Mystery Bridge Road/U.S. Highway 20 Site
Natrona County, Wyoming
Operable Unit 1 - Ground Water
'i
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for Operable Unit 1 - Ground
Water (aU 1) of the Mystery Bridge Road/U.S. Highway 20 (Mystery Bridge) Superfund site
in Natrona County, Wyoming. This remedy was chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Uability Act of 1980
(CERCLA), as amended by the Superfund Amendments and Reauthorization Act of 1986
(SARA) and the National Contingency Plan (NCP).
This decision document explains the basis for selecting the remedy for this site. The
information that forms the basis of this remedial action decision is contained in the
Administrative Record for this site and is summarized in the attached decision summary.
The State of Wyoming concurs with the selected remedy for au 1. The State of Wyoming,
however, feels that the CERCLA remedial action and measures being developed under the
Resource Conservation and Recovery Act (RCRA) to address contamination from the
Sinclair/Uttle America Refinery Company (LARCO) property at the site need to be integrated
into a single comprehensive planning and remediation effort.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this Record of Decision (ROD), may present
an imminent and substantial endangerment to public health, welfare, or the environment.
DESCRIPTION OF SELECTED REMEDY
The Mystery Bridge Superfund site has been divided into two operable units: ground water
(aU 1) and contaminant source areas (OU 2). Past and current removal actions were
implemented to prevent the migration of contaminants from source areas. The selected.
remedy presented in this ROD addresses ground water that has been contaminated by
these sources. It describes remediation intended to reduce the levels of contaminants in
ground water that were released from the KNEnergy, Inc (KN) and oow Chemical Company
and Dowen-Schlumberger, Inc. (Dow/oSI) facilities. Ingestion of and direct contact with
contaminated ground water have been determined to pose the principal threat to human
health. au 2 will address contaminated subsurface soils in the vicinity of the industrial
properties at the site and is expected to complete remediation of contaminant sources. A
separate ROD will be prepared for the remediation of au 2.
The remedial action selected by EPA for OU 1 includes a system for extracting
contaminated ground water from locations near the KN and oow/oSI facilities, treating the
extracted water to remove contaminants, and reinjecting the resulting clean water into the
ground. The selected remedial actions for au 1 will address the ground water plume
emanating from the oow/oSI facility that contains volatile halogenated organic (VHO)
contaminants and the ground water plume emanating from the KN facility that contains
aromatic hydrocarbon contaminants including benzene, ethylbenzene, toluene and xylene
-------
"
\)
RECORD OF DECISION
MYSTERY BRIDGE ROAD/U.S. - HIGHWAY 20 SUPERFUND SITE
NATRONA COUNTY, WYOMING
OPERABLE UNIT 1 - GROUND WATER
SEPTEMBER 24,1990
-------
;; .
.
.
.
(BETX). The major components of the selected actions that are common to both the VHO
and BETX plumes include:
.
monitoring ground water, discharged treated water, and air; and
.
implementation of temporary institutional controls. such as deed and/or user
restrictions.
VHO Plume: Air Stripping Treatment with Umited Water Extraction. The major
components of the selected remedy for the VHO plume include:
extraction of VHO contaminated ground water in the upgradient portion of the plume:
air stripping of extracted ground water;
reinjection of treated ground water; and
natural anenuation in the downgradient portions of the plume.
BET)( Plume: Air Stripping Treatment of Extracted Ground Water. The major
components of the selected remedy for the BETX plume include:
.
extraction of BETX contaminated ground water;
air stripping of extracted ground water;
.
.
reinjection of treated ground water to injection wells.
This remedy assumes continuation of the ongoing KN removal actions.
DECLARATION OF STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment. complies with
Federal and State requirements that are legally applicable or relevant and appropriate to
the remedial action, and is cost effective. This remedy utilizes permanent solutions and
alternative treatment technologies. to the maximum extent practicable. However, because
complete treatment 01 the principal threats 01 the site was found to not be practicable, this
remedy does not satisfy in full the statutory preference for treatment as a principal element.
Only a portion 01 the VHO plume will be treated. Natural attenuation will reduce
contaminant levels in the remaining downgradient portion 01 the plume. Because of the
hydrogeologic conditions in the area. extraction and treatment of the entire VHO plume
would cause contamination from the nearby plume emanating from the LARCO facility
(referred to as the RCRA plume) to migrate further into the residential area. The LARCO
facility is under jurisdiction of RCRA and contamination at the facility is being addressed
under this authority. The entire BETX Plume will be remediated through treatment as a
principle element.
Because this remedy may result in hazardous substances remaining on site above health-
based levels, a review of the remediation will be conducted within five years after
commencement 01 the remedial action to ensure that the remedy continues to provide
adequate ion 01 human health and the environment.
it~ . ..2~ I 9~eJ
15ate
-------
DECISION SUMMARY
MYSTERY BRIDGE ROAD/U.S. HIGHWAY 20 SUPERFUND SITE
OPERABLE UNIT 1 . GROUND WATER
TABLE OF CONTENTS
Page
1
- 3
6
7
8
11
18
28
33
37
I. SITE NAME, LOCATION AND DESCRIPTION
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
III. HIGHLIGHTS OF COMMUNITY INVOLVEMENT
IV. SCOPE OF ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
V. SITE CHARACTERISTICS
VI. SUMMARY OF SITE RISKS.
VII. DESCRIPTION OF ALTERNATIVES
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
IX. SELECTED REMEDY
X. STATUTORY DETERMINATIONS
TABLES
1 VHO Plume Contaminants
2 BETX Plume Contaminants
3 Carcinogenic Risk Characterization
4 Summary of VHO Plume Alternatives.
5 Summary of BETX Plume Alternatives
6 Selected Remedy Costs
10
13
19
22
26
35
FIGURES
1 Site Map
2 VHO Plume
3 BETX Plume
4 Key Risk Terms
2
12
14
15
EXHIBIT
1 Mystery Bridge ARARs Evaluation
2 Selected Remedy ARARs
-------
morod6
I. SITE NAME, LOCAT10N AND CESCRIPT10N
u
The Mystery Bridge Road/U.S. Highway 20 (Mystery Bridge) Superfund site (Figure 1) is
located in Section 5, Township 33N, Range 78W 6th P.M. in Natrona County, one mile east of
Evansville, Wyoming. The site includes two residential subdivisions (Brookhurst and Mystery
Bridge) and an industrial area to the south where certain hazardous materials have been used.
The site is bordered on the north by the North Platte River, on the west by the Sinclair/Uttle
America Refining Company (LARCO), and on the south by U.S. Highway 20. Mystery Bridge
Road and the Mystery Bridge subdivision extend along the eastern perimeter of the site.
Topography of the area varies from flat or gently sloping to slightly rolling. The slope of the
land surface is less than 2 percent but ranges between 7 and 25 percent along the banks of
the North Platte River. The 100- and 500- year floodplains are within 50 to 100 feet of Elkhorn
Creek and the North Platte River. Because of upstream reservoir regulation, the relatively large
channel capacity of the river and rare heavy precipitation events, the North Platte River does
not have an extensive history of flooding.
Drainage is mainly overland flow to man-made diversion structures and to Elkhorn Creek.
Elkhorn Creek is a perennial stream that crosses the site and flows in a northeasterly direction
into the North Platte River. Water from Elkhorn Creek is used for washing equipment at
industrial facilities. During the summer, water is diverted for irrigation of nearby fields.
The Mystery Bridge site is underlain by an alluvial aquifer which previously served as a water
supply to all of the homes in the area. After discovery of organic compounds in water from this
aquifer, all but six of these homes began using other water sources. Currently only two wells in
the residential area are being used to provide drinking water. The alluvial aquifer is also used
for fire fighting by KNEnergy, Inc. (KN). The uppermost bedrock aquifer, the Teapot Sandstone
formation, provides water to a number of industrial wells in the area of the site. Except for
ground water, no other natural resources on the site are used. The North Platte River is used
for recreational fishing.
The residential area, located on the northern two thirds 01 the site, consists of 125 lots which
range in size from two to five acres. Houses were constructed on approximately 1 00 of these
lots between 1973 and 1983. According to population data collected in 1987, approximately
400 people lived within the Brookhurst subdivision. In addition, approximately 250 people
comprised the work force for the industrial properties bordering the residential area. Within a
1-mile radius of the study area, the total work daytime population is approximately 1000 people.
The population within a 3-mile radius was approximately 3000 people, which included 2160
people in the community 01 Evansville.
An industrial area is located along the southern perimeter of the site to the south of the
Burlington Northern Railroad (BNRR) right-of-way and north of the highway. Present industrial
operations at the site include companies which provide oil field services, bulk fuel storage for
local delivery, natural gas processing and compressing, and supply commercial chemicals.
Several petroleum refineries operate to. the west of the site. Other businesses located along
U.S. Highway 20 include truck sales, grading, moving and storage, and public utilities.
Past and present surface and subsurface storage units and other structures at the site include
several underground and above ground storage tanks, abandoned drums, an unlined waste
pond and a concrete lined waste pond. Although several of the units have been removed,
these features have released contaminants from the industrial facilities at the site and are
discussed in detail in the next section.
1
-------
--
fEUCO
--_..
-
LI TTlE
_RICA
REFINING
CIlltPANY
-
N
IIYCO
IlUAlIHGfOH-HOAfHfAH RAilROAD R/II
REf INING CO.
LITTLE A!tERICA
lIP FEED & II
I "'~",.., I
-CONf I HEN' AL
Oil CO.
PlATTE
Figure 1
Mystery Bridge
Site Map
I
I
I
bOU
~ .;;;.
IN HEI
"""ROX. SCAl E
,...'uLi
.J
-------
morocs6
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
c
Initial Investigations
In August of 1986, residents complained of poor air and water quality in and around the
residential subdivisions. As a result. the Wyoming Department of Environmental Quality
(WDEQ), the Natrona County Health Department and the Office of Drinking Water in EPA
Region VIII began an investigation of the site. Results of early sampling activities indicated
organic compounds in residential wells and tap water. Residents were advised not to use their
well water for drinking or food preparation purposes. In the same year, the State of Wyoming
began providing bottled water to residents. Under the Superfund Removal Program. EPA took
over the lead responsibility for: removal activities including providing bottled water. As part of
the removal program, EPA also installed monitoring wells and conducted sampling programs to
further investigate the release of contaminants and gather information to evaluate the need for
further removal action.
The Agency for Toxic Substances and Disease Registry (ATSDR) assessed the public health
risk posed by volatile organic compounds in the ground water at the site. ATSDR determined
that there was an imminent and significant health threat to site residents and that if action were
not taken within one year, the levels of contaminants would increase the lifetime cancer risk for
individuals drinking well water from the area.
In March 1987, EPA began an Expanded Site Investigation (ESI) to further define the nature
and extent 01 contamination in air, soil, surface water and ground water at the site and to
respond to community concerns. The ESI delineated several potential plumes 01 ground water
contamination and identified several potential sources of contaminants. Based on the findings
of the ESI, the Mystery Bridge site was proposed for the National Priorities Ust (NPL) in June of
1988. Usting 01 the Mystery Bridge site on the NPL was finalized on August 28, 1990.
The ESI concluded that one or more contaminated ground water plumes originate near the
Dow/DSI property, and that another ground water plume resulting from the release of aromatic
hydrocarb,ons originates near the KN facility. The report also concluded that soils at the Dow
Chemical Company and Dowell-Schlumberger Inc. (Dow/DSI) facility were contaminated and
soils at KN could be contaminated. A third major plume was identified as entering the
subdivision from the LARCO property to the west.
The LARCO facility is under the authority of the Resource Conservation and Recovery Act
(RCRA) and was not investigated as part of the CERCLA activities at the Mystery Bridge site.
The contamination associated with the LARCO facility is being addressed through a unilateral
3008(h) corrective action order issued on December 1,1988 on wl"lich LARCO and EPA are
negotiating a consent decree. The contaminated ground water (referred to as the RCRA
plume) is believed to be made up of floating petroleum/hydrocarbon products.
Based on an imminent and substantial endangerment to public health revealed by the ESI, EPA
decided to supply an alternative permanent water system for the subdivision. The water supply
project was separated into two phas~s: Phase I included the design and construction of a
water transmission line from the municipal water supply in Evansville to the site and a
distribution system throughout the residential area; Phase II involved upgrading the Evansville
water filtration facility, and included the design and construction 01 a new water intake and its
corresponding pump station, a new transmission line from the new intake to the Evansville
water filtration facility, and a new sedimentation basin. Phase II was required because the
existing intake was below the Casper wastewater treatment plant discharge and the water
quality was unacceptable. The system was put into operation in January 1989.
3
-------
moroo6
Concurrent with the initial scientific studies, EPA also conducted research to identify potentially
responsible parties (PRPs), parties who may be liable pursuant to CERCLA, tor the clean up of
contamination at the site. Notice letters regarding removal actions and remedial activities were
sent in late 1986 and 1987 to various PRPs identified including Dow Chemical Company,
Dowell-Schlumberger, Inc., and KNEnergy, Inc.
Pentachloraphenol (PCP) was detected in two soil samples and several wells located on the
BNRR right-ot-way. Over 60 abandoned 55-gallon drums were also tound on the property.
Analysis of samples trom the drums indicated that 11 of the drums contained aromatic
hydrocarbons and other chemical compounds. These drums were relocated to a BNRR freight
building. The remaining drums were found to contain typical trash and were disposed of by
WDEO. In 1988, a soil contamination study conducted at the 8NRR property concluded that
soil underlying the drums was not contaminated.
Removal Actions
In December 1987, KN and Dow/DSI each entered into Administrative Orders on Consent to
perform removal actions at their respective facilities. Dow/DSI and KN agreed to take
immediate actions to control suspected sources of ground water contamination on their
respective properties and to prevent further migration of contaminated ground water into the
subdivision.
Dow/DSI: The Dow/DSI facility uses mobile mounted pumps, tanks and other associated
equipment to perform oil and gas production enhancement services for the oil and gas
industry. Dow/OSI performs its own truck repair and stores solvents in drums on site.
A gravel leach sump for disposal of truck wash water located on the western portion of the
property had been in operation since shortly after the facility began operations. The wash
water is believed to have contained chlorinated solvents. Also located on the western part of
the property, a 1000-gallon underground oil/water separator tank was used to separate oil film
and solids washed from trucks. Separated wash water left the separator and flowed through a
vitreous tile drain to the leach sump system. A toluene storage area was located at the north
end 01 the 1acility. Contaminants were released from both the wash water disposal system and
toluene storage area.
Because 01 these releases and the resulting contamination, and in accordance with the
Administrative Orders on Consent, Cow/CSI prepared an Engineering Evaluations/Cost
Analysis (EElCA) report to document the extent and nature 01 the releases 01 contaminants,
and to propose expedited removal actions to control migration 01 contaminants and eliminate
sources 01 contaminants beneath and adjacent to their property. As a result of drilling and
sampling activities at the Oow/OSI1acility in 1987, severaJ volatile halogenated organic (VHO)
soil contaminants were identified in the ground water and soil near the abandoned chlorinated
sump area. The VHO group includes chlorinated organic compounds. The EE/CA prepared
by Cow/CSI evaluated removaJ technologies and recommended a removal action that was then
implemented.
Removal activities at the Cow/CSI facility began in January 1988. This removal included the
excavation and off-site land1llllng 01 approximately 440 cubic yards 01 contaminated surface
soils.1rom the chlorinated sump area. The oil/water separator, the decommissioned waste oil
tank .and portions 01 the vitreous tile drain were also removed from the site. A soil vapor
extraction (SVE) system was used in the chlorinated sump area and removed over 300 pounds
4
-------
mOr0d6
of contaminants from the soil. Almost 6,000 pounds of solvents were removed from soils from
the toluene storage area using a SVE system.
KN: KN has operated a natural gas fractionation, compression, cleaning, odorizing, and
transmission plant at the site since 1965. Operational maintenance activities are performed on-
site. .
o
Originally constructed as an earthen impoundment, a flare pit was used to collect spent
material generated by the facility. Materials that may have been placed in the flare pit include:
1) crude oil condensate; 2) absorption oil; 3) emulsions, antifoulants, and anticorrosive agents;
4) liquids accumulated in the flare stack; 5) potassium hydroxide treater waste; and 6)
lubrication oils and blowdown materials from equipment in the plant. In October 1984, the
western half of the impoundment was backfilled and a new concrete lined flare pit was
constructed on the eastern half. Use of the flare pit was discontinued and the pit was
decommissioned in 1987. Waste streams formerly collected in the flare pit were rerouted into
above storage tanks for temporary storage or recycling.
A catchment area, a low spot in the ground just west of Elkhorn Creek, collected surface run-off
water containing contaminants from the plant area and steam condensate from the dehydration
unit. Various activities were undertaken by KN to reroute materials away from this area in 1984.
In 1965, an underground pipe burst during facility start-up and 5,000 to 10,000 gallons of
absorption oil were injected under pressure into the ground beneath the process area.
Absorption oil is used at the KN processing facility to remove impurities from the natural gas
stream. Other releases occurred between 1965 and 1987 in the form of small leaks and spills
near the flare pit and catchment area.
Because of these releases and the resulting contamination, and in accordance with the
Administrative Order on Consent, KN prepared an EEiCA report. An investigation was
conducted as part of the EEiCA for removal actions at the KN facility. A soil vapor survey was
conducted in the vicinity of the flare pit, and soil boreholes and ground water were sampled.
Additional samples were collected from soils between the concrete flare pit and the flare stack,
and also beneath the concrete flare pit. SeveraJ aromatic hydrocarbon contaminants were
identified in the soils and ground water near the flare pit. Benzene, ethylbenzene, toluene and
xylenes (BETX) are included in the aromatic hydrocarbons group. A floating layer of BEn<
contaminants was identified during subsequent ground water sampling at the KN facility.
Based on additionaJ drilling and sampling, aromatic hydrocarbons were identified within the
boundaries of a section of soil that is stained by what is believed to be absorption oil from past
releases in the process area and flare pit location. The stained soil on the KN property extends
across the northeastern portion of the Dow/DSI property, through the railroad right-of-way and
slightly into the residentiaJ area.
In November 1989, removal actions designed to remove 8ETX contaminants from the ground
water and soil beneath the KN facility began. Pursuant to this removal action, volatile BEn<
contaminants are being removed from the ground water and soil using a SVE system and a
ground water treatment system. As of July 31, 1990, the KN removal system had recovered
approximately 6,000 gallons of BETX contaminants and has extracted approximately 135
pounds of benzene from the soils and ground water beneath the KN facility.
Remedial Investigation/Feasibility Study (RI/FS)
In December 1987, an Administrative Order on Consent was issued to Dow/DSI and KN
requiring them to conduct a Remedial Investigation/Feasibility Study (RI/FS) to characterize the
extent of contamination and identify alternatives for cleaning up the site. The RifFS report,
5
-------
mbr006
which was completed in June 1990, concluded that two plumes of contaminated ground water
originate in the industrial area south of the subdivision and are migrating through the
subdivision in a northeast direction. 'The first of these plumes is contaminated with VHO
compounds (referred to as the VHO plume), and extends from the Dow/DSI facility to the North
Platte River. The second plume is contaminated with BEn< compounds (referred to as the
BEn< plume), and extends from the KN facility to the BNRR property and possibly into the
subdivision directly north of the KN facility. In addition, a layer of BETX contaminants
originating at the KN facility and extending slightly into the subdivision was found floating on
the ground water.
PCP contamination near the BNRR property that was identified during the ESI was not detected
in subsequent ground water sampling conducted for the RI/FS. However, EPA will further
address the PCP contamination during activities conducted for the second operable unit for the
site which will evaluate contaminant source areas as discussed in Section IV.
The RI/FS also identified areas of contaminated soils related to the industrial properties at the
site including Dow/DSI, KN, Van Waters and Rogers, NATCO, Sivalls, Permian, and Mobile
Pipeline. Much of this soil has been removed or cleaned up as part of the removal actions
described above. However, some underground soil contamination remains in the industrial
area of the site. This contamination will be addressed during the studies conducted for
contaminant source areas of the Mystery Bridge site (see Section IV).
As part of the RI/FS, in September 1989, EPA prepared a baseline risk assessment (BRA) to
estimate potentiaJ heaJth and environmental risk which could result if no action were taken at
the site. The BRA indicated that exposure to ground water could result in significant risks due
to contaminants at the site. Details of the BRA are summarized later in Section VI.
The RI/FS, completed in June 1990, suggested that ground water plumes of VHO compounds
emanating from the Cow/CSI property and BETX compounds emanating from the KN property
are not commingled in the area downgradient from the Dow/DSI and KN facilities. The data
also suggested the VHO plume could be commingled with the RCRA plume. Since the most
recent data contained in the RI/FS was from ground water samples taken in September and
October 1,989, EPA requested the data be updated prior to issuing this ROD to determine if
these conditions had changed.
In July 1990, ground water samples from 20 wells were collected by consultants for Dow/CSt
(with split samples obtained by EPA and consultants for KN) and analyzed for selected VHO
and BETX compounds. The primary objectives of this sampling were to further assess possible
commingling 01 the contaminant plumes and to Investigate the current degree 01 contamination
as it may have been affected by the ongoing KN removal action. Results of the July sampling
suggest that there is no current commingling of the VHO plume with the BETX plume nor the.
VHO plume with the RCRA plume. The July 1990 data are somewhat conflicting with historical
data with respect to BETX compounds in the ground water northeast of the KN property line
and the volume 01 the BETX plume appears to be greater than that estimated in the RI/FS.
III. HIGHUGHTS OF COMMUNITY INVOLVEMENT
Community interest in problems at the Mystery Bridge site became very intense in late 1986
when site contamination problems first surfaced and tMe ATSCR advisory was issued. Early
public meetings, many of which were attended by as many as 100 people, often became highly
emotional encounters between concerned residents and public officials. Media coverage was
extensive, including coverage by tocaJ and State newspapers and television stations, as well as
some national television coverage.
6
-------
mbroo6
LJ
State legislators and Congressional staff member$ took a great interest in site activities. The
community's letter-writing campaign extended to the White House.
Initial community involvement was coordinated by an EPA removal program community
relations coordinator, as well as by an EPA field liaison, EPA's representative in Casper, and
the Emergency Response Branch's On-Scene Coordinator for the site.
-
v
EPA's removal community relations coordinator prepared a Community Relation Plan in
December 1986. The Plan was revised in November 1988 by the remedial community
involvement coordinator.
Between December 1986 and July 1987, EPA held five public meetings. From December 1986
through October 1989, EPA issued five Fact Sheets and 14 Information Updates. In January
1990, EPA distributed a Fact Sheet on the risk assessment for the site. In addition, EPA
provided for public comment on work plans, sampling plans, the Community Relations Plan,
alternative water supply options, and other key documents throughout site activities. EPA
issued responsiveness summaries for comments received during these comment periods.
From April 1987 through June 1988, EPA representatives participated in a Governor's Task
Force and Oversight Committee on a regular basis. From June 1988 through October 1989,
EPA worked with WDEa and the Natrona County Health Department to continue a monthly
forum for discussing issues with community members.
To further fulfill the requirements of CERCLAISARA Section 113 (k)(2)(i-v) and Section 117, the
Administrative Record file for the removal actions was established at EPA's Denver office and at
EPA's Wyoming field office in Casper. EPA also provided a copy of the record to one
community group who requested it under the Freedom of Information Act (FOIA). The
Administrative Record for the remedial activities was established at the Natrona County Ubrary
in Casper and in EPA's Denver office.
The Proposed Plan for OU 1 was issued on July 3, 1990 with a one-quarter page advertisement
placed in the Casper Star Tribune on July 1" 1990 outlining remedial alternatives and
announcing the public comment period and public meeting. The public comment period was
open from July 5 to August 3, 1990. The public meeting was held July 18, 1990 at the Casper
City Council Chambers. A transcript of the public meeting is included in the Administrative
Record.
Approximately five community members attended the Proposed Plan public meeting. Two oral
comments were received at the public meeting and three sets of written comments were
received during the public comment period.
Details of community involvement activities and responses to official public comment on the
Proposed Plan are presented in the Responsiveness Summary attached to this ROD.
IV. SCOPE OF ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
The Mystery Bridge site has been divided into two operable units: one to address ground
water (OU 1) and the other to evaluate contaminant source areas (OU 2). The remedy selected
in this ROD is for the first operable unit and addresses. the contaminated ground water
emanating from the Dow/DSI and KN facilities. This ground water poses the principal threat to
human health and the environment due to ingestion 01 and contact with water from wells that
contain contaminants above the Maximum Contaminant Levels (MCLs) established by the Safe
Drinking Water Act.
7
-------
mc:wcce
EPA will evaluate remaining source areas in au 2 and, as necessary, will determine whether
further aCtion is required for contaminated subsurface soils in the vicinity of the industriaJ
properties that were identified during the RI/FS and represent possible continuing sources of
ground water contamination. Questions raised by comments received during the public
comment period regarding the BNRR property will be further evaJuated during au 2.
EPA believes additionaJ consideration of the contaminant source areas is necessary to ensure
the long-term effectiveness of the ground water dean up. The RI focused primarily on
contaminated ground water and did not address mechanisms which may transport
contaminants from soils to water. Removal actions for the Dow/DSI and KN facilities prevent
further migration from source areas into residents' ground water. Questions remain concerning
the ability of the removaJ aCtions to eliminate sources of contamination. For example. the SVE
and hydrocarbon recovery aCtivities at the site may not be effective on soils below the ground
water. There are also inherent technicaJ difficulties in deaning the stained soil areas above the
ground water and the floating BETX contaminants.
\
v. SITE CHARACTERISTtCS
Site Geology and Hydrology
The site is located within a narrow strip of Quaternary alluvial floodplain and terrace deposits
along the North Platte River and Elkhorn Creek. The upper 1.5 to 13 feet of the alluvial deposit
is a surticiaJ soil layer which consists of a mixture of sandy sift and clayey silt. The remaining
alluvium ranges in thickness from 13 to 68 feet It is well-sorted coarse to medium sand with
little fine sand and trace amounts of silt and gravel.
Bedrock crops out to the southeast and northwest of the site. In the uppermost 200 to 300 feet
of bedrock the formations are in ascending order: 1) Teapot Sandstone. consisting of medium-
to fine-grained sandstone with shaJe partings and 2) the Lewis ShaJe. consisting of thick
bedded shaJe grading into brown sandstone.
The bedrock surface at the site is beneath a layer of aJluvium. A clay layer indicating
weathered bedrock was encountered at the contact between the aJ/uvium and bedrock in
almost every borehole. A vaJley in the bedrock surface that roughly paraJlels the present
course of EJkhom Creek was aJso identified. This vaJley was probably eroded by a former
course of the North Platte River. Bedrock elevations increase on both flanks ot the vaJley. To
the east, this increase is part of a divide separating the site from an adjoining drainage. The
aJluvium pinches out in the east, restricting movement of ground water towards the residentiaJ
area. The bedrock surface is less regular to the northwest. A comparison of bedrock surface
topography to aUuviaj ground water flow directions shows that the shape of the bedrock valley
significantJy affects ground water movement in the aJluvia! aquifer. The low permeability layer at"
the bedrock surface also appears to confine the contaminants to the upper alluvial aquifer.
The horizontal component 01 ground water.flow within the aJluviaJ aquiter is consistently to the
northeast with only minor and 10caJ variations. The flow direction appears to be controlled to a
certain degree by the alignment ot the valley in the bedrock surface. Although water level
differences between the alluvium and undertying bedrock have been variable, they generally
confirm the potentiaJ for ground water in the bedrock to flow into the aJluvium in the vaJley from
peripheral portions of the 10caJ area. -
Based on the character of the aJluviaJ materiaJs at the site and on hydraulic tests conducted
within the alluvium, the ground water seepage velocity for horizontaJ flow within the aJluvium
ranges from 0.21 to 4.9 feet per day, with an average vaJue ot 2.12 feet per day. The seepage
velocity represents the rate at which dissolved contaminants would be transported with the
8
-------
mD
-------
Table 1: VHO Plume Contaminants
-4
a
Contaminants (ug/I)
Current t-1,2 DCE 1,1,1 TCA TCE PCE
Well 10 Oate ~ Average. Maximum Current Average. Maximum Current Average' Maximum Current Average' Maximum
MCC.'. :(:70 ~, ~HH'...' ~..., 7200 .:-;'.. .:. ... 5 5~"
EPA 1-1 7/90 2 2.8 4 6 15 21 22 29 37 35 34 37
EPA 1-2 4/89 <1 <1-<5 <5 8 18 31 4 55 110 17 37 45
EPA 1-6 4/89 <1 <1-<5 <5 11 8.5 11 1 5.6 10 15 17 23
EPA 1-7 4/89 5 3.9 5.0 23 73 99 180 138 190 77 87 110
EPA 2-1 4/89 <5 <5 <5 15 13 15 23 26 29 37 31 37
EPA 2-2 4/89 <5 <5 <5 15 14 21 25 36 52 39 36 40
EPA 2-3 7/90 <1 <1-<5 <5 <1 <1-<5 <5 2 6.3 15 4 7.0 13
EPA 2-8 4/89 <5 <5 <5 7 . 6.8 11 <1 2.3 4.0 10 8.7 12
EPA 2-9 4/89 <5 <5 <5 13 25 31 11 13 22 50 45 50
EPA 2-10 4/89 <5 <5 <5 <1 1.7 2.5 <1 49 130 <1 7.5 15
EPA 2-15 4/89 2 1.9 2.5 11 38 90 110 75 130 57 70 130
MK MW-1 4/89 24 24 24 4 4 4 110 110 110 38 38 38
PCMW-2 4/89 <1 1.9 2.5 9 56 78 10 17 28 42 67 88
PCMW-4 4/89 <5 <5 <5 1 9.1 21 <1 5.6 17 6 11 22
MW87-2 9/89 <1 <:1-<10 <10 <1 25 70 <1 <1-<10 <10 16 27 89
MW87-4 9/89 <1 <1-<15 <15 <1 40 150 2 20 71 7 87 320
MW87-6 7/90 <10 <1-<500 <500 <10 <1-<500 <500 <10 78 250 <10 78 250
MW87-7 9/89 <1 47 180 <1 56 140 220 172 340 7 75 150
MW87 -8 9/89 <1 <1-<10 <10 <1 26 100 5 57 220 23 142 540
OSI MW-1 9/89 <5 <5 <5 9 9 9 430 430 430 20 20 20
OSI MW-3 9/89 <5 <5 <5 <5 <5 <5 <5 <5 <5 20 20 20
OSI MW-4 9/89 <5 <5 <5 <5 <5 <5 44 44 44 23 23 23
OS. MW-6 7/90 <100 <5-<100 <100 <100 <5-<100 <100 <100 34 50 <100 <5-<100 <100
--
.. DBt8CIion UmiV2 va/UB USBd for averaging purposss
.... PropoSBd MCL
~
-------
mD
-------
......
I\)
-
--
'EXACO
LITTLE
AIIEIIICA
REF INI...
C_ANY
-
~
-
BuIlL I HG' OH-NOII'
HElIN RA ILROAO R/II
I
I
~ I
~ "'-'~~(I '~"
f1~ or -- "G,Qo". ~
t:::J -- ~''E '
- 0-, ---- 1111; 11 --......
~ nn ~iM~f!'dl!J.?~~ ~~110~-:;1(
r;;, ~ 11;/ fJo >- \ 1Ir--,
~ U h. t- a:U'I--
-.. ~ , : uf' " [}]IIO ~~a: (
.-- . tUn c:ao
'- - . - . .=:-JL IX
- - z
- c..
.ltHff+ -', '~,
""ttt."...".... 0:-:::: -" ~:::::::::::u
JOt1IIS' 01' FUEL Htttttt.". '~~" - J
LINERS CDrIt1fRCIAL
DUllDINC SYSlEHS
IIYCO
LITRE AHfRICA REFINING CO.
..-------"
i~1
"~I
~f.
, 01
A l2:.2i-~e_, II I
Httt~ ~ -
ttttt.Httt.
ttt~
-
COIIIItIfH' AL
all co.
LAlHROP
RANCH
Figure 2
Mystery Bridge
VHO Plume
LEGEND
--so ICE
I soc on can I r a tl on
Contour (in ugH I
~ Approximate A/lldl
Extent 01 RCRA Pluma
In the Residential Alea
@tta IIlustraliva E XdlllpltJ
0' Ground Waler 'lull
Would ba TrealtH!
o bOO
~...;.
I ~IJU
Al'PROX, SCALE IN fH I
-------
Table 2: BETX Plume Contaminants
Contaminants (ugJl)
Ethyl- Total
Current Benzene benzene Toluene Xylenes
Well 10 Date Current Averaae" Maximum Current Average" Maximum Current Average" Maximum Current Average" Maximum
MCa.: ",,;,:;"..-'::';";..5 --
.. 1OO~" 2000 ... 10000 ..
EPA 1-9 7/90 <1 2.4 4 <1 1.7 3 <1 <1-<5 <5 <3 <1-<5 <5
EPA 1-10 7/90 <1 5.9 19 7 5 11 <1 2.5 10 <3 7.6 21
EPA 2-11 7/90 <5 22 70 4 22 82 <5 <1-<10 <10 8 194 760
EPA 2-11 (Ip) 7/90 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 1.0 1.0 1.0
EPA 2-14 7/90 <1 <1-<5 <5 <1 <1-<5 <5 <1 <1-<5 <5 <3 <1-<5 <5
KN MW-2 2/88 <5 <5 <5 <5 <5 <5 <5 20 38 <5 <5 <5
KN MW-3 2/88 <5 <5 <5 2 2.3 2.5 <5 <5 <5 6 88 170
KN MW-5 2/88 <500 <500 <500 <500 <500 <500 <500 <500 <500 180 180 180
KN MW-6 7/90 <1 160 320 <1 <1-<500 <500 <1 <1-<500 <500 <3 461 920
KN MW-6 (Ip) 7/90 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.5 0.5 0.5
KN MW-7 7/90 <1 <1-<250 <250 <1 70 140 <1 <1-<250 <250 <3 551 1100
KN MW-7 (Ip) 7/90 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 1.7 1.7 1.7
KN ABC-11 7/90 <5 18 33 <5 56 110 <5 43 83 110 705 1300
KN ABC-11 (Ip) 4/89 <1000 <1000 <1000 2000 2000 2000 2000 2000 2000 18000 18000 18000
KN ABC-24 7/90 <1 <0.5-<5 <5 <1 <0.5-<5 <5 <1 <0.5-<10 <10 <3 2.7 7
KN ABC-25 10/89 <0.5 2.5 7 <0.5 <0.5-<1 <1 <0.5 <0.5-<10 <10 1 5.1 14
KN ABC-26 10/89 220 180 220 790 513 790 520 191 520 6900 4083 6900
KN ABC-26 (Ip) 10/89 <100 100-<1000 <1000 2000 1500 2000 3300 1900 3300 19000 18000 19000
KN ABC-27 10/89 <5 <5 <5 <5 <5 <5 38 45 52 300 184 300
KN ABC-27 (Ip) 10/89 9600 9600 9600 1400 1400 1400 9600 9600 9600 13000 13000 13000
KNP-2 10/89 <500 240 250 150000 75025 150000 390 390 390 1100000 550800 1100000
KNP-2 (Ip) 10/89 <100 <100 <100 2100 2100 2100 340 340 340 1400 1400 1400
-
.. Detection Umill2 value USBd for BV8raging purposBs
II II Proposed MCL
(fp) ;: Floating Product in ppm
-------
--
rEXACO
_"'.-f
~ITJLE
AIIEIIrCA
REF IKING
COIiPAHY
-
-
......
.
8URlINGION-NORrHfRN R~I~ROAO R/v
WYCO
LITT~E AnERICA REfiNING CO.
--"
-.--
~-~~
LATHROP FEED & I}
EQUIPIlENT /
--
-co,H II/ENUl
OIL CO.
PLA TTE
LATHROP
RANCH
Figure 3
Mystery Bridge
BETX
Plume
LEGEND
. Approxlmaltl
Are.' Exlenl 0'
Ground Waler Willi
BE TX Concenlralloll
> MCLs or Proposed MCLs
.0..." un HI,fa t:~IIHI,.I.'
Floaling
- Approxlllldl..
Areal Exl8111 0'
Hvdrocarbons LilY",
----- Approxllllal..
Are.' Exlenl 0'
Siained Soil
o bUU
~-
I lutl
_I
APPROX. SCALE IN flU
-------
Fjgure 4
Key Risk Terms
Carcinogen: A substance that increases the incidence of cancer.
Chronic Daily Intake (COI): The average amount of a chemical in contact with an
individual on a daily basis over a substantial portion of a lifetime.
Chronic Exposure: A persistent, recurring, or long-term exposure. Chronic exposure
may result in health effects (such as cancer) that are delayed in onset, occurring long
after exposure ceased.
Exposure: The opportunity to receive a dose through direct contact with a chemical or
medium containing a chemical.
Exposure Assessment: The process of describing, for a population at risk. the
amounts of chemicals to which individuals are exposed. or the distribution of exposures
within a population. or the average exposure of an entire population.
Hazard Index: An EPA method used to assess the potential noncarcinogenic risk. The
ratio of the cor to the chronic RfD (or other suitable toxicity value for noncarcinogens) is
calculated. If it is less than one, then the exposure represented by the cor is judged
unlikely to produce an adverse noncarcinogenic effect. A cumulative. endpoint-specific
HI can also be calculated to evaluate the risks posed by exposure to more than one
chemical by summing the CDI RfD ratios for all the chemicals of interest exert a similar
effect on a particular organ. This approach assumes that multiple subthreshold
exposures could result in an adverse effect on a particular organ and that the
magnitude of the adverse effect will be proportional to the sum of the ratios of the
subthreshold exposures. If the cumulative HI is greater, than one, then there may be
concern for public health risk.
Reference Dose (RID): The EPA's preferred toxicity value for evaluating
noncarcinogenic effects.
Risk: The nature and probability of occurrence of an unwanted, adverse effect on
human life Or health, or on the environment.
Risk Assessment: The characterization of the potential adverse effect on human life or
health. or on the environment. According to the National Research Council's
Committee on the Institutional Means for Assessment of Health Risk, human health risk
assessment includes: description on the potential adverse health effects based on an
evaluation 01 results of epidemiologic, clinical, toxicologic, and environmental research:
extrapolation from those results to predict the types and estimate the extent of health
effect in humans under given conditions of exposure: judgements as to the number and
characteristics of persons exposed at various intensities and durations; summary
judgements on the existence and overall magnitude of the public-health program: and
characterization of the uncertainties inherent in the process of inferring risk.
Slope Factor: The statistical 95% upper confidence limit on the slope of the dose
response relationship at low doses for a carcinogen. Values can range from about
0.0001 to about 100,000, in units of lifetime risk per unit dose (mg/kg-day). The larger
the value, the more potent is the carcinogen, Le., a smaller dose is sufficient to increase
the risk of cancer.
15
-------
.'11or0<36
Exposure Assessment
Although exposure pathways were identified for ground water, surface water and sediments,
residential soils, and air media at the site, the risk assessment indicated that only the ground
water pathway could result in significant health risks. Of the 13 indicator contaminants studied
in the BRA, PCE, TCE, 1,1 DCA and benzene were determined to be the primary contaminants
of concern in the ground water pathway.
Because of the northeasterly flow of ground water in the alluvial aquifer at the site,
contaminants introduced into the ground water below the sources at the southern section of
the site could be transported across the residential areas. Thus. a significant potential
exposure pathway involving ground water is likely to exist for the subdivision residences which
currently use site ground water for domestic purposes. All but two of the residences now use a
non-contaminated municipal water supply in place of ground water. The pathway for
contaminants is intercepted for residents using the municipal water supply; however, potential
risk of exposure to the ground water contaminants remains. In addition. considering the
potential for future land development at the site, future residences could potentially be located
on properties currently used by industries. The ground water pathway is therefore likely to be
complete for these future hypothetical residences. Two important exposure scenarios, the
Current Resident and Future Hypothetical Resident, were developed based on the fact that
ground water is the primary exposure medium at the site.
Intake of contaminants present in ground water could potentially occur via three routes: 1)
ingestion of ground water; 2) dermal contact with water while bathing, showering, cooking or
swimming (also ground water used for outdoor domestic and/or agricultural purposes); and 3)
inhalation of indoor air contaminants volatilized while bathing, showering, or cooking, or that
volatilized and directly accumulated in the living spaces. In addition, use of contaminated
ground water in a home cooling unit (Le., swamp cooler) could potentially lead to the inhalation
of volatilized contaminants. The contaminant intake equations and values chosen for various
intake parameters were derived from the standard intake equation and data presented in EPA
guidance documents. Chronic daily intakes (CDls) were estimated in the BRA. Representative
exposure. point concentrations were developed from the sampling data for contaminants
measured in EPA monitoring wells in the residential area.
The Reference Dose values (AtD) for a substance represents a level of intake which is unlikely
to result in adverse non-carcinogen health effects in individuals exposed for a chronic period ot
time. The RtDs (in mg/kg-day) for the contaminants include: 1,1 DCA = 0.01; 1,1,1 TCA =
0.09; 1,2 DCE = 0.02; PCE = 0.01; xylenes = 2; toluene = 0.3; and ethylbenzene = 0.1.
The slope factor represents the upper 95 percent confidence limit value on the probability of
response per unit intake of a contaminant over a life time (70 years tor the analysis in the BRA).
Slope factors used in the BRA tor the contaminants (in (mg/kg-day).I) include: TCE = 0.11; 1,1
DCA = 0.091; PCE = 0.051 and benzene = 0.029.
Toxicity Assessment
Indicator contaminants present in the ground water include VHO and BETX compounds. The
foliowirTg discussion comes from the toxicological profiles of these contaminants presented in
the BAA.
VHo.s TCE is classified as a group B2 carcinogen (a probable human carcinogen). TCE has
been shown to cause pulmonary adenocarcinoma, lymphoma, and hepatocellular carcinoma il
multiple strains of mice. Subchronic and chronic exposures of animals to TCE appears to
16
-------
mor0d6
result in liver and kidney toxicity. PCE has been classified as a group C carcinogen (a possible
human carcinogen) based upon evidence that the chemical causes hepatocellular carcinoma
in mice. Mouse and rat studies have indicated that PCE is a teratogen and a reproduction
toxin. In addition, both oral and inhalation exposure of laboratory animals to PCE for
intermediate and long-term exposure leads to liver, kidney and spleen toxicity. 1,1 DCA, t-1,2
DCE and 1,1,1 TCA are not demons~rated human carcinogens. 1,1 DCA appears to cause
kidney damage in laboratory animals exposed subchronically via the inhalation route. Rats
exposed to t-1,2 DCE via inhalation developed progressive damage to the lung and fatty
changes in the liver. Chronic inhalation exposure of laboratory animals to 1,1,1 TCA resulted in
hepatoxicity (fatty changes in the liver and increased liver weights).
8ETX EPA considers benzene to be a group A carcinogen. This listing signifies that there is
"Sufficient evidence from epidemiologic studies to support a causal association between
exposure and cancer." In sensitive humans, alterations in bone marrow have been shown to
form during short-term exposures to approximately 10 ppm benzene. Several studies have
demonstrated an increased incidence of non-lymphocytic leukemia from occupational
exposure. Intermediate and chronic exposure to benzene can adversely effect the
hematopoietic and immune systems.
Ethylbenzene, toluene and xylenes are classified as non-carcinogens. Ethylbenzene is acutely
toxic to the lung and central nervous system. However, subchronic and chronic exposures of
laboratory animals to this compound cause liver and kidney damage, as well as testicular
toxicity. The teratogenicity of ethyl benzene has also been indicated in rats. A primary target
for toluene toxicity is the central nervous system. In humans acute exposures to 100 ppm 01
toluene via inhalation causes fatigue, sleepiness, decreased manual dexterity and decreased
visual acuity. Exposure to high levels of toluene, as occurs in solvent abuse, can result in
permanent central nervous system effects such as tremors, atrophy, and speech, hearing, and
vision impairment. Animal studies indicate that toluene is also a development toxin causing
growth inhibition and skeletal anomalies. Xylene orally administered to animals can result in
central nervous system toxicity and has also been shown to cause ultra-structural liver changes
(although these changes are not necessarily adverse effects). Xylene has also been shown to
be a fetotoxin and a teratogen in mice at high oral doses.
Risk Characterization
The BRA evaluated the potential non-carcinogenic and carcinogenic risks posed by the
indicator contaminants in the various exposure media at the Mystery Bridge site. Carcinogenic
risk is presented as a probability value (i.e., the chance of contracting some form of cancer
over a lifetime). The estimate of carcinogenic risk is conservative and may overestimate the
actual risk due to exposure.
In the risk characterization, the aggregate carcinogenic risk due to ground water indicator
contaminants at the site is compared to an acceptable target risk. The chance of one person
developing cancer per one million people (or 1 ~ is used as a target value or point of
departure above which carcinogenic risks may be considered ,unacceptable. The 1 ~ point 01
departure is used when ARARs are not available (i.e., no MCLs or proposed MCLs for the
indicator contaminants) or are not sufficiently protective of human health and the environment.
17
-------
morooe
Carcinoaenic Risk. Carcinogenic risk is typically estimated by multiplying the Col of an
indicator contaminant by its slope factor. A summary of carcinogenic risks for residents living
directly above and using contaminated ground water from the VHO and BETX plumes in the
Current Resident scenario is provided in Table 3. The aggregate carcinogenic risk is 8.1 x 10-5
for the VHO plume and 4.7 x 10-5 for the BETX plume. Total carcinogenic risk due to ground
water consumption exceeded 1 Q-6 at both the VHO and BETX plumes. The primary source of
risk posed by the VHO plume was PCE and TCE contamination. The major component of the
risk values calculated for the BETX plume were based on the risk due to exposure to benzene.
Carcinogenic risks were also calculated for selected indicator contaminants for residents using
ground water from wells at the Dow/oSI and KN properties in the Future Hypothetical Resident
scenario. These risks, shown in Table 3, also exceeded 1 Q-6. The aggregate carcinogenic risk
for the VHO plume was 3.2 x 1 Q-<4 and 1.7 x 1 Q-<4 for the BETX plume.
Non-Carcinoaenic Risks. The ratio of Col to RfC was computed for each contaminant and the
resulting ratios are summed to give the hazard index. Non-carcinogenic hazard indices were
calculated for both the Current Resident and Future Hypothetical Resident scenarios. Results
indicated the aggregate hazard indices do not exceed unity; therefore, EPA believes that there
is no non-carcinogenic public health threat.
Risks Due to Indoor Air Contamination. There is a high likelihood that the residents who use
contaminated well water are being exposed to indoor organic vapor contaminants that have
volatilized from the well water. This exposure occurs through inhalation of volatilized
contaminants while showering, bathing, or cooking, as well as volatilized contaminants from
home cooling units. Quantitative risk calculations were not done for indoor air because there is
a high degree of uncertainty associated with the generic (non site-specific) and inhalation risk
factors. Although not quantified, this exposure to contaminated indoor air adds additional risk
for subdivision residents using contaminated well water.
Another potential source of site-related indoor air contamination is the direct emanation and
accumulation of volatilized plume water in the living spaces of residences located directly over
the contaminated ground water plumes. The risks from this direct accumulation of indoor
organic vapors is considered to be insignificant when compared to the risks from inhaling
volatilized shower, bath or cooking water.
Environmental Risks
The ecological effects due to releases from industrial areas are not expected to be significant
for three reasons: 1) these industrial areas do not provide habitat resources for wildlife; 2) the
sampling data for surface water and sediments at Elkhom Creek indicates minor levels 01
contamination from the site; and 3) contamination 01 the North Platte River via ground water
plume discharge is expected to be relatively insignificant due to the high rate of river flow as
compared with the rate 01 ground water discharge.
VII. DESCRIPTION OF ALTERNATIVES
A feasibility study was conducted to develop and evaluate remedial alternatives for OU 1 at the
Mystery Bridge site. Remedial alternatives were assembled from applicable remedial
technology process options and were initially evaluated for effectiveness, implementability, and
cost. The alternatives meeting these criteria were then evaluated and compared to nine criteria
required by the NCP. In addition to the remedial alternatives, the NCP requires that a no-action
alternative be considered at every site. The no-action alternative serves primarily as a point of
comparison for other alternatives.
18
-------
Table 3: Carcinogenic Risk Characterization
Methylene Pathway I
Scenario/Pathway Benzene PCE TCE 1 ,1 DCA Chloride Total I
Current Resident
Ingestion 7.0E-07 2.SE-OS S.1 E-OS 2.3E-06 2.SE-07 7.9E-OS
Absorbtion 1.3E-06 8.9E-08 1.9E-07 8.SE-09 9.0E-10 1.6E-06
Aggregate 8.1 E-05
Future Hvoothetical RAsident .
Ingestion - 7.1 E-OS 2.SE-Q4 - - 3.2E-04
Absorbtion - 2.9E-07 1.0E-06 - - 1.3E-06
Aggregate. 3.2E-Q4
VHO Plume
BETX Plume
Scenario/Pathway
Current Besident
Ingestion
Absorbtion
Aggregate.
Fu ure H oth
Ingestion
Absorbtion
Aggregate;
Benzene
PCE
TCE
1 ,1 DCA
Methylene Pathway
Chloride Total
1.4E-05 1.3E-06
2.5E-05 4.8E-09
8.3E-07 2.2E-OS
3.0E-09 2.SE-05
4.7E-05
5.8E-05
1.1 E-Q4
5.8E-05
1 .1 E -04
1.7E-04
. selected contaminants only
19
-------
mor006
Each remedial alternative acknowledges the removal activities that have occurred or are
currently taking place assumes continuation of the ongoing activities. While sources are being
controlled by the removal actions, ground water remains contaminated with VHO and BETX
compounds released from the sources. The remedial alternatives described in this ROD
address this ground water contamination.
A ground water model has been developed to simulate transport of dissolved VHO compounds
through the alluvial ground water system. The model incorporates a variety of physical,
chemical, and biological factors which can affect the rate of contaminant migration through the
aquifer. Known variability and expected uncertainty in these factors were incorporated into the
model by performing 5,000 duplicate model runs with model parameters selected randomly
from within their known or expected ranges. The resulting model runs provided an expected
range of contaminant concentrations over time, from which statistically most-probable
contaminant transport rates could be estimated. Contaminant transport rates were used to
estimate time frames for the remedial alternatives developed in the RI/FS. This transport model
was not applied to the BETX plume because downgradient migration of BETX compounds from
the KN property to the BNRR property appears to be minimal.
The action levels for remediation are the MCls and proposed MCls for the contaminants of
concern. Attainment of these levels will be protective of human health and the environment.
However, EPA recently studied the effectiveness of ground water extraction systems in
achieving specified goals and found that it is often difficult to predict the ultimate concentration
to which contaminants in the ground water may be reduced. The study did find that ground
water extraction is an effective remediation measure and can achieve significant mass removal
of contaminants. Most of the remedial alternatives described in this section include ground
water extraction systems and assume that it is technically feasible to achieve MCLs or
proposed MCls in the ground water.
Except for the no-action alternative which includes ground water monitoring only, each
alternative includes the following common elements:
Ground Water Monitoring. Ground water monitoring during the remedial activities will be
used to evaluate performance of the remediaJ action. Monitoring points are anticipated to be
located upgradient of the plume (to detect contamination from other sources), within the plume
(to track the plume movement during remediation), and downgradient (to detect plume
migration). Monitoring points to the west of the VHO plume would be used to evaluate whether
commingling with other plumes occurs in the Mure. Ground water samples would be analyzed
for site indicator compounds as determined during remedial design. Existing monitoring wells
and possibly additional monitoring wells to be installed would be used for ground water
monitoring. The specific locations and frequency 01 ground water monitoring will depend on
the remedial alternative selected and site conditions at the time of implementation. Monitoring
would continue after remedial objectives are met to ensure residuaJ contaminants desorbing
into ground water will not exceed MCls or proposed MCLs in the tuture.
Temporary Institutional Controls. Temporary restrictions on the construction and use of
private water wells, such as well restrictions in property deeds, well construction permits,
and/or deed notices during remediation would effectively restrict human consumption of
ground water exceeding MCls and proposed MCls in the residential area until remediation
goals for ground water are achieved. Actual institutional controls to be used will be determined
during remedial design.
20
-------
moroc6
VHO Plume
Seven remedial alternatives for the VHO' plume were considered for detailed evaluation and are
described below. Table 4 provides a summary of the alternatives. Alternative V2 contemplated
collection of VHO-impacted ground water and transport to an off-site RCRA treatment facility.
This alternative was eliminated early in the evaluation process because it would be technically
infeasible to implement and would involve costs that would be grossly excessive compared to
its overall effectiveness.
Alternative V1 - No-action with ground water monitoring.
Under this alternative, EPA would take no further action to control the source of contamination.
However, long-term monitoring of the site would be necessary to monitor contaminant
migration. Monitoring using previously installed monitoring wells and residential wells can
easily be implemented.
Because this alternative would result in contaminants remaining on-site, CERCLA requires that
the site be reviewed every five years. If indicated by the review, remedial actions would be
implemented at that time to remove or treat the wastes.
Alternative V1 relies on natural processes in the ground water to reduce VHO levels in the
aquifer. Results of contaminant transport and fate modeling described previously indicated
that the most-probable time required for natural processes to reduce contaminant
concentrations by two orders 01 magnitude at the downgradient edge 01 the subdivision (Le., at
the North Platte River) would be approximately seven years. A two order 01 magnitude
reduction would result in VHO concentrations .below MCLs and proposed MCLs.
Consequently, it is expected that VHO contaminants will have been effectively flushed out of
the aqui1er beneath the subdivision within seven years. The ground water would be restored to
a Classification I aqui1er suitable for drinking water purposes. There is a minimal chance that
complete flushing would take as long as 19 years.
The present ~orth cost for Alternative V1 would be $71,000. Since the alternative requires "no-
action", there would be no capital cost. However, operation and maintenance (O&M) costs are
estimated to be $11,000 for ground water monitoring.
Alternative V3 - extraction of VHO-impacted ground water, aerobic biological treatment of
extracted ground water, and discharge of treated ground water to the North Platte River.
Extraction 01 ground water with VHO concentrations exceeding MCLs or proposed MCLs
would be accomplished with an extraction well system. Assuming al'l extraction system of ten
wells and a volume of impacted ground water of 1096 acre-feet, extraction would be completed.
in one to two years after initiation 01 the alternative. The actual number of wells could change
as determined by remedial design. The time for remediation could vary depending on several
factors including the pumping rate and the volume of impacted ground water.
A sequencing batch reactor system would provide aerobic biological treatment of extracted
ground water and would facilitate destruction 01 organic constituents. The treatment system
would be expected to volatilize some of the VHO contaminants which would be released to the
atmosphere.
Aerobic biological treatment of ground water would produce a sludge that would require
disposal. An estimated 170 tons of non-hazardous sludge per year would be generated. The
sludge would b~ expected to meet all RCRA criteria for land disposal.
21
-------
Table 4: Summary of VHO Plume Alternatives
Alternatives I
I
Component V1 V3 V4 V4AI V5 V6 I V6A I V7
Ground Water I I I I
Common Monitoring X X X X X X X X
Elements Institutional
Controls X X X X X X X
Extraction of Ground
Extent of Water with VHO
Ground Water Concentrations> MCLs X X X X
Extraction Extraction of Upgradient
Ground Water With VHO
Concentrations> MCLs X X
Aerobic Biological Treatment
of Extracted Ground Water X
Air Stripping of
Extracted Ground Water X X
Carbon Adsorption 01
Treatment Extracted Ground Water X X
Technology Chemical Oxidation 01
Extracted Ground Water X
Natural Attenuation 01 VHOs
in Downgradient Plume X X
In.-situ Bioremediation
of VHOs in Downgradient Plume (X) (X)
In-situ Bioremediation
01 VHO Plume X
Injection 01 Treated Water
to UpiDowngradient Wells X X
Disposition 01 Discharge 01 Treated
Treated Water Water to North Platte River X X X X
Discharge 01 Treated
Water to Elkhom Creek (X) (X)
(X) - Option or Contingency
22
-------
mbroo6
Treated ground water would be discharged to the North Platte River. For cost estimation
purposes, it was assumed that a treatment facility would be located on industrial property. The
discharge would be sampled as necessary to comply with National Pollutant Discharge
Elimination System (NPDES) permit requirements.
Capital cost for Alternative V3 would be over $2 million with O&M costs of $165,000. The
present worth cost would be almost $2.5 million.
Alternative V4. Extraction of VHO.impacted ground water, air stripping of extracted
ground water, and discharge of treated ground water to the North Platte River.
This alternative is similar to Alternative V3, except that extracted ground water would be treated
in an air stripping tower on-site to remove VHOs. In the air stripping process, VHOs are
transferred from the water phase to the air phase and discharged to the atmosphere. Air
stripper vapor discharge would be sampled as necessary to comply with Wyoming Air Quality
Standards and Regulations.
Alternative V4 would involve capital costs of over $1 million and O&M costs of $129,000. The
present worth cost would be approximately $1.3 million.
Alternative V4A. Extraction of VHO.lmpacted ground water, carbon adsorption treatment
of extracted ground water, and discharge of treated ground water to the North Platte
River.
This alternative is similar to alternatives V3 and V4, except that extracted ground water would
be treated in a carbon adsorption system on-site to remove VHOs. In the carbon adsorption
process, VHOs are adsorbed onto activated carbon, thereby removing them from the ground
water. The spent carbon is typically thermally or chemically regenerated for reuse.
Present worth cost for this alternative would be almost $1.4 million. Capital cost would be $1.2
million with O&M costs of $128,000.
Alternative VS. extraction of VHO.lmpacted ground water, chemical oxidation of extracted
ground water, and discharge of treated ground water to the North Platte River.
This alternative is similar to alternatives V3, V4, and V4A, except the chemical oxidation of
contaminants in extracted ground water would be implemented on-site using controlled reactor
vessels. A retention time of approximately a few minutes should be sufficient to treat influent
ground water VHO concentrations to the required levels.
Capital cost for Alternative V5 would be $1.1 million with O&M costs equal to $282,000.
Present worth cost is $1.7 million.
Alternative V6 . extraction In the upgradlent portion of the plume which contains the
highest VHO concentrations, air stripping of extracted ground water, discharge of treated
ground water to Elkhom Creek or reinjection upgradlent or downgradlent of the extraction
well system, and natural attenuation in the downgradlent portions of the plume.
An extraction well system would remove ground water with VHO levels exceeding MCLs and
proposed MCLs in the upgradient portion of the plume. Assuming one extraction well and a
volume of VHO-impacted ground water in the upgradient portion of the plume of 57 acre-feet,
extraction should be completed in about one year following implementation of the remedy. The
actual number of extraction wells could change as determined by the remedial design.
23
-------
mOt0d6
Extracted ground water would be treated to remove VHOs in an air stripping tower on-site as
described for Alternative V4. Concentrations of VHOs in the treated ground water would be
reduced to MCLs or proposed MCLs.
Treated ground water would be reinjected upgradient or downgradient of the extraction well.
Oowngradient injection points could accomplish the following objectives: 1) provide additional
hydraulic containment of the upgradient portion of the VHO plume being extracted; 2)
minimize the possibility of any interaction related to VHO remediation efforts with nearby
plumes and/or free BETX contaminants associated with the KN facility; and 3) assist
remediation in the downgradient portion of the VHO plume. The final reinjection locations(s)
would be determined during remedial design. Treated ground water would be sampled as
necessary to comply with Wyoming Underground Injection Control (UIC) program
requirements.
"
Alternative V6 relies on natural processes in the ground water to reduce VHO levels in
downgradient portions of the aquifer. Concentrations of VHOs should decline two orders of
magnitude, which would be sufficient to lower the VHO concentrations to MCLs and proposed
MCLs, within about six years. . An extraction well system in the upgradient portions of the plume
would help prevent VHO concentrations in ground water leaving the northern Dow/OSI property
boundary from exceeding MCLs or proposed MCLs. VHO concentrations throughout the
aquifer would therefore meet MCLs and proposed MCLs within six years under Alternative V6.
However, there is a minimal chance that a complete flushing could take as long as 18 years.
In situ bioremediation in the downgradient portion of the plume was considered as an
additional component of Alternative V6. However, it was not incorporated for the following
reasons: 1) this type 01 treatment is designed primarily for source control, not area control; 2)
the uncertainties in remediation time associated with this treatment; 3) extraction and injection
of treated water would cause nearby plumes to migrate further into the residential area; and 4)
treatability studies would be required.
Costs for Alternative V6 would include capital cost of $183,000, O&M costs of $122,000, and
present worth cost of $354,000.
Alternative V6A - extraction of the upgradlent portion of the plume which contains the
highest VHO concentrations, carbon adsorption treatment of extracted ground water,
discharge of treated ground water to Elkhom Creek or reinjection upgradient or
downgradlent of the extraction well system, and natural attenuation in the downgradient
portions of the plume.
This alternative is Similar to Alternative V6, except extracted ground water would be treated to
remove VHOs in a carbon adsorption system on-site similar to Alternative V4A.
Alternative va costs would include $357,000 in capital cost, $114,000 for O&M, and a present
net cost of $518,000.
Alternative V7 -In situ bloremedlatlon of VHO-Impactec:t ground water.
In situ bioremediation of ground water with VHO concentrations exceeding MCLs and
proposed MCLs would involve addition of an oxygen source, nutrients, and hydrocarbon
feedstock, such as methane, to the aquifer to promote the activity of organisms which co-
metabolize VHOs. An injection and extraction well circulation system would distribute oxygen,
nutrients, and co-metabolites through the aquifer. Assuming the extraction and injection well
system would consist of six extraction wells and four injection wells. VHO concentrations would
24
-------
mbr0d6
. be expected to be reduced to MCls and MCls in two to five years. The actual number of wells
for the system could change as determined by remedial design. Treatability testing would be
necessary to determine design parameters for in situ bioremediation.
Ground water monitoring would be performed during the two to five years of in situ ground
water treatment and following completion of treatment to verify the reduction of VHO
concentrations in the aquifer.
Capital cost for this alternative would be $425.000 and O&M costs would be $133.000. Present
worth cost would be over $1 million.
BETX Plume.
For the BETX plume. five remedial alternatives (including the no-action alternative) remained
following the screening analysis. Table 5 summarizes the alternatives for the 8ETX plume.
Each of the remedial alternatives designed to address the 8ED< plume are described below.
Alternative B2 contemplated collection of 8ETX-impacted ground water and transport to an off-
site RCRA treatment facility. This alternative was eliminated early in the evaluation process
because it would be technically infeasible to implement and would involve costs that would be
excessive compared to its overall effectiveness.
Alternative B1 - No-action with ground water monitoring.
Similar to Alternative V1 for the VHO plume, Alternative B1 relies on presently occurring natural
processes to reduce concentrations on the BETX compounds in the aquifer. The time frame
for the ground water to be restored to a Classification I aquifer under the no-action alternative
is unknown.
The costs associated with ground water monitoring for this altemative would be $11,000 in
O&M. Present worth cost would be $137,000.
Alternative B3 - extraction of BETX-impacted ground water, aerobic biological treatment of
extracted ground water, discharge of treated ground water to either Injection wells
located upgradlent or downgradlent of the extraction well system or to Elkhorn Creek
Extraction of ground water with BETX concentrations above MCls or proposed MCls would be
accomplished in Alternative B3 with an extraction well system. Assuming a volume of impacted
ground water of ten acre-feet as estimated in the RI/FS, the time of aquifer remediation has
been calculated to be approximately three months. If the volume of impacted ground water is
assumed to be 25 acre-feet, based on a more conservative approach, the time for remediating
the aquifer is extended to approximately eight months. Ground water extraction and treatment,
would continue until MCLs and proposed MCls are permanently attained in the BETX plume.
Extracted ground water would be passed ,through an oil/water separator to remove free
hydrocarbons. Recovered hydrocarbons would be recycled. It was assumed that the existing
oil/water separator would be used for this purpose.
Following separation 01 aromatic hydrocarbons. a sequencing batch reactor system. similar to
the system described for Alternative V3 for the VHO plume. would provide aerobic biological
treatment of extracted ground water and would facilitate destruction of organic constituents.
The treatment system would be expected to volatilize some of the BETX compounds which
would be released to the atmosphere.
25
-------
Table 5: Summary of 8ETX Plume Alternatives
Alternatives
Component ,')-
81 83 B4 85 86
Ground Water
"
Monitoring X X X X X
Institutional
Common Controls X X X X
Elements Soil Vapor Extraction ,
of 8ETX Contaminated Soils X X X X j
Hydrocarbons Recovery I
I
and Recycling X X X X !
,
Extraction of Ground
Extraction Water with 8ETX
Concentrations> MCLs X X X
Aerobic Biological Treatment
of Extracted Ground Water X
Treatment Air Stripping of
Technology Extracted Ground Water X
Chemical Oxidation of
Extracted Ground Water X
In-situ Bioremedlation
of BETX Plume X
Injection of Treated Water
Disposition of to UpiCownaradJent Wells X X X
Treated Water Discharge of Treated
Water to Elkhom Creek 00 (X) (X)
(X) - Option or Contingency
26
-------
."broa6
'-
Aerobic biological treatment of ground water would produce an estimated 1 0 to 20 tons of
sludge per year. The sludge would be expected to meet all RCRA criteria for land disposal.
Treated ground water would be discharged to injection wells upgradient or downgradient of the
extraction well system or to Elkhorn Creek. Upgradient injection locations could facilitate
movement of the contaminants toward extraction wells. Downgradient injection locations could
serve to contain the plume and also provide hydraulic assistance in ground water collection.
The discharge would be sampled as necessary to comply with NPDES and/or Wyoming UIC
program requirements.
()
Costs for this alternative would include capital cost of $582,000, and O&M costs of $44,000.
The present worth cost would be $750,000.
Alternative 84 - Extraction of 8ETX-impacted ground water, air stripping of extracted
ground water, and discharge of treated ground water to either injection wells located
upgradient or downgradient of the extraction well system or to Elkhorn Creek.
This alternative is similar to Alternative B3, except extracted ground water would be treated with
an air stripper. It was assumed that the existing on-site air stripper would be used. In the air
stripping process, BETX compounds are transferred from the water phase to the air phase and
discharged to the atmosphere. Based on the best available control technology (BACT)
analysis performed as part of the EEICA for the KN current removal action, vapors emitted
during air stripping and SVE treatment at the KN facility would be associated with an individual
probability of cancer of 1 X 10-1, which is within the acceptable limit established by the NCP.
Based on this analysis, the WDea determined that the preferred approach for management of
air stripper emissions for the KN removal action was venting the air stripper emissions at the
top of the on-site flare stack, which raises the point of emissions to 110 feet above ground
level, thereby decreasing the individual probability of cancer to 5 X 10-9. Accordingly, this
method 01 air emission management was implemented in connection with the current removal
action and is included in Alternative B4. It was assumed that vapors emitted from the air
stripping system would be vented from the flare stack and that risk levels similar to those for
the current removal action would be associated with the system proposed. Discharge from the
flare stack would be monitored as necessary to comply with Wyoming air quality standards.
The present worth cost 10r this alternative would be $248,000. The capital cost would be
$73,000 with O&M costs 01 $51 ,000.
Alternative 85 - extraction of BETX-impacted ground water, chemical oxidation of
extracted ground water, and discharge of treated ground water to either injection wells
located upgradlent or downgradlent of the extraction well system or to Elkhorn Creek.
This alternative is similar to alternatives 83 and 84, except chemical oxidation 01 extracted
ground water would be implemented on-site using controlled reactor vessels similar to
Alternative V5 for the VHO plume
Costs for this alternative would include $400,000 capital cost, $53,000 O&M costs, and a
present worth cost 01 $577,000.
Alternative 86 -In situ bioremedlatlon of BETX-Impacted ground water.
In situ bioremediation 01 ground water would involve adding an oxygen source and nutrients to
the aquifer in qrder to promote the activity of organisms which degrade contaminants in a
manner similar to Alternative V7 for the VHO plume. The injection/extraction well system would
27
-------
mDr0a6
. consist of one extraction well and one injection well. It was assumed that one of the three
existing aromatic hydrocarbons recovery wells would be used for extraction, and an existing
on-site injection well would be used for injection. The actual number and location of wells for
the system could change as determined by remedial design. Prior to mixing, extracted water
would be passed through an oil/water separator to remove BEn< contaminants extracted with
ground water. Recovered BEn< contaminants would be recycled. To the extent technically
practicable, in situ bioremediation would continue until the ground water achieves MCLs and
proposed MCLs which would be expected to be within two to five years. Treatability testing
would be necessary to determine design parameters for in situ bioremediation.
This alternative would cost $87,000 in capital cost with $37,000 for O&M. The present worth
would be $344,000.
!)
VIII. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The remedial alternatives developed in the FS were analyzed in detail for both the VHO and
BEn< plumes using nine evaluation criteria. The resulting strengths and weaknesses of the
alternatives were then weighed to identify the alternative for each plume providing the best
balance among the nine criteria. These criteria are: 1) overall protection of human health and
the environment; 2) compliance with applicable or relevant and appropriate requirements
(ARARs); 3) reduction of toxicity, mobility, or volume through treatment; 4) long-term
effectiveness and permanence; 5) short-term effectiveness; 6) implementability; 7) cost; 8)
state acceptance; and 9) community acceptance. Each 01 these criteria is described below.
VHO Plume
Criterion 1: Protection of Human Health and Environment
Overall protection 01 human health and the environment addresses whether a remedy provides
adequate protection and describes how risks posed through each pathway are eliminated,
reduced, or controlled through treatment, engineering controls, or institutional controls.
All the treatment technologies employed by the alternatives are protective 01 human health and
the environment by eliminating or reducing risk through the treatment 01 contaminants in ground
water. In addition, the institutional conyQls and the existing municipal water supply would
minimize further use 01 ground water and there10re reduce exposure to contaminants. As the
no-action alternative does not include treatment or controls, it provides no reduction in risk and
will no longer be discussed with regard to the VHO plume.
Alternatives V6 and VeA, which contemplate limited extraction 01 ground water, provide the
greatest overall protection. Extraction and injection of ground water throughout the entire VHO .
plume, as considered in alternatives V3, V4, V4A, V5, and V7, would accelerate eastward
migration 01 the RCRA plume. The approximate areal extent 01 the ACRA plume is shown in the
residential area on Figure 2. The resulting movement of the RCRA plume would increase the
areaJ extent of contamination in the aquifer from that plume, thereby increasing potential risk to
residents in the subdivisions.
Criterion 2: Comoliance with Aoolicable Relevant and Aoorooriate Reauirements (ARARs)
Applicable requirements are those cleanup standards, standards 01 control, and other
substantive requirements, criteria, or limitations promulgated under Federal or State
environmental or facility siting law that specifically address a hazardous substance, pollutant.
contaminant, remedial action, location, or other circumstance at a CERCLA site. Relevant and
appropriate requirements are those cleanup standards, standards of control, and other
28
-------
mbl'Od8
substantive requirements, criteria, or limitations promulgated under Federal or State
environmental siting law that, while not "applicable" to a hazardous substance, pollutant,
contaminant, remedial action, location, or other circumstance at a CERCLA site, address
problems or situations sufficiently similar to those encountered at the CERCLA site that their use
is well suited to the particular site. .
D
Compliance with ARARs addresses whether a remedy will meet all Federal and State
environmental laws and/or provide basis for a waiver from any of these laws. These ARARs are
divided into chemical specific, action specific, and location specific groups.
All the VHO alternatives would comply with ARARs. The ARARs evaluation is provided as
Exhibit 1 .
Criterion 3: Lona-Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of a remedy to maintain reliable
protection of human health and the environment over time. This criterion includes the
consideration of residual risk and .the adequacy and reliability of controls.
The remedial alternatives all result in minimal residual risk. All the alternatives are expected to
attain MCLs and proposed MCLs, thereby resulting in minimal risk from contaminant residuals
in ground water. The institutionaJ controls and the existing municipal water supply additionally
mitigate residual risk by minimizing the use of ground water.
Alternatives V3, V5 and V7 result in no treatment residuals. Alternatives V4 and va release
emissions to the atmosphere, but at negligible levels and minimal risk. Additional controls for
these two alternatives include monitoring to ensure compliance with Wyoming air quality
standards, and a BACT analysis to ensure emissions are minimized. Alternatives V4A and V6A
require disposal or treatment of contaminated carbon filters, but pose minimal residual risk.
Criterion 4: Reduction of Toxicitv. Mobilitv. or Volume throuah Treatment
Reduction of toxicity, mobility, or volume.through treatment refers to the preference for a
remedy that uses treatment to reduce health hazards, contaminant migration, or the quantity of
contaminants at the site.
All the alternatives employ an irreversible treatment as a primary element to address the
principal threat of contamination. Alternatives V6 and V6A treat a smaller volume of water than
the other alternatives in order to avoid adverse effects to the RCRA plume.
Reduction in toxicity, mobility, and volume of contaminants in ground water is best
accomplished by Alternative V5 through chemical oxidation. Alternatives V4 and va indirectly
reduce toxicity and volume through photodegradation of contaminants. Photodegradation
occurs when the contaminants, released to the atmosphere, are broken down by sunlight.
Alternative V7 reduces toxicity and volume through treatment but would require treatability
studies to evaluate its effectiveness. Alternatives V4A and V6A reduce mobility, but not volume
or toxicity because these alternatives result in spent carbon filters containing the contaminants,
requiring disposal or regeneration of the carbon. Alternative V3 reduces toxicity, mobility and
volume 'of contaminants, but would produce 170 tons of non-hazardous sludge annually which
would require disposal.
29
-------
mbroa6
Criterion 5: Short-Term Effectiveness
Short-term effectiveness refers to the period of time needed to complete the remedy and any
adverse impacts on human health and the environment that may be posed during the
construction and implementation of the remedy.
Alternatives V6 and V6A are not expected to pose any appreciable short-term risks to the
community and workers during construction and implementation.
Alternatives V3, V4, V4A, V5, and possibly V7 are expected to cause adverse effects to the
environment and human health by spreading the RCRA plume through the aquifer and possibly
depleting the aquifer.
'J
The high extraction volume in alternatives V3, V4, V4A, V5, and V7 are expected to attain
remedial objectives in the shortest time, two years, with the exception of V7 which could take
as long as five years. Alternatives V6 and V6A are expected to require six years to attain
remedial objectives. These two alternatives would not result in the unacceptable effects on
human health and the environment as are expected from the other alternatives through effects
on the RCRA plume.
Criterion 6: Imclementabilitv
Implementability refers to the technical and administrative feasibility of a remedy, including the
availability of materials and services needed to implement the chosen solution. It also includes
coordination of Federal, State, and local governments to clean up the site.
Alternatives V6 and V6A are most easily technically implemented because these alternatives
involve activities primarily on the Dow/DSI facility, requiring the least amount of construction
and least difficulty with property access. Alternative V7, and possibly V5, would be less easily
implemented because of the need for treatability studies to better understand the applicability
of in situ bioremediation and chemical oxidation to the site. Alternatives V3, V 4A, and V6A
present no technical difficulties, but require the additional burden of disposing of or treating
residual sludges and carbon filters.
All alternatives require ground water monitoring. Alternatives V6 and V6A additionally require
air monitoring. Monitoring activities would be coordinated with the State of Wyoming.
Criterion 7: Cost
This criterion examines the estimated costs for each remedial alternative. For comparison,
capital and annual O&M costs are used to calculate a present worth cost for each alternative.
Alternatives V6 and V6A have the lowest capital and O&M costs, resulting in present worth of
$353,B22 and $51 B,407, respectively. These alternatives are the least expensive because they
incorporate scaJed-down ground water extraction in comparison to the other alternatives. V7 is
the next most costly, with a present worth of $1,011,288. Alternatives V4 and V4A, which are
scaled-up versions of V6 and V6A, and V5, differ in treatment method, but are otherwise similar
and so cost nearly the same. Present worth estimates for these three alternatives range from
$1,351 ,BB3 to $1,673,488. V3 is the most costly because of very high capital expenses, and
has a present worth of $2,482,675.
30
-------
mDr0d6
Criterion 8: State Acceptance
EPA has involved the WDEQ in the RifFS and remedy selection process. WDEQ was provided
the opportunity to comment on the RifFS document and the proposed plan, and took part in
the public meeting held to inform the public of the proposed plan. WDEQ's statement in regard
to the selected remedy, read at the public meeting, states in part "It is the position of the
Department [WDEQ] that the proposed actions identified in alternatives B4 and V6 should be
implemented as soon as possible". WDEQ went on to add that it concurs with the proposal to
further investigate subsurface soil contamination sources as contemplated in OU 2.
WDEQ believes, however, that remedial actions taken under CERCLA should be integrated with
the RCRA corrective action addressing the RCRA plume, forming a comprehensive effort to
concurrently remediate all ground water contamination within the Brookhurst subdivision.
WDEQ's comments are further addressed in the attached Responsiveness Summary.
Criterion 9: Community Accectance
EPA solicited input from the community on the clean up methods proposed for the ground
water at the Mystery Bridge site. Although public comments indicate no specific opposition to
the preferred alternative, residents and their representatives did raise concerns about the
methods and data used to reach that alternative. These issues are addressed in the attached
Responsiveness Summary and some will be incorporated into OU 2 activities for the site.
BETX Plume
Criterion 1: Protection of Human Health and the Environment
All the treatment technologies employed by the remediaJ alternatives are protective of human
health and the environment by eliminating or reducing risk through the treatment of
contaminants in ground water. In addition, institutional controls and the municipal water supply
would minimize further use of ground water and therefore reduce exposure to contaminants.
As the no-action alternative does not include treatment or controls. it provides no additional
reduction in risk and will no longer be discussed with regard to the BETX plume.
None of the alternatives is expected to adversely impact the RCRA plume as some of the VHO
plume alternatives would.
Criterion 2: Applicable or Relevant and Acpropriate Reauirements lARARs}
All the BETX alternatives would comply with ARARs. The ARARs evafuatlon is provided as
Exhibit 1 .
Criterion 3: Lona-Term Effectiveness and Permanence
The remedial alternatives all result in minimal residual risk. All the alternatives are expected to
attain MCLs or proposed MCLs, thereby resulting in minimal risk from contaminant residuals in
ground water. The institutional controls and the existing municipal water supply additionally
mitigate residual risk by minimizing the use 01 ground water.
Over the long term. each alternative will likely leave some residual BETX contaminants in
subsurface soils on or near the KN facility. Problems related to these residuals will be
addressed au 2. Alternative B6, however, would help treat some of the residual BEn<
contaminants since in situ bioremediation would destroy contaminants with naturally occurring
microorganisms in ground water and in subsurface soils.
31
-------
mbr0d6
Alternative 85 would result in no treatm.ent residuals. Alternative 84 would release emissions to
the atmosphere, but at negligible levels and minimal risk. The air stripper contemplated in
Alternative 84 is currently operating as part 01 the KN removal action. Monitoring has
demonstrated that air stripper emissions are within Wyoming air quality standards. Alternative
83 would result in 10 to 20 tons annually 01 non-hazardous residual sludge requiring off-site
disposal.
"
Criterion 4: Reduction in Toxicitv. Mobilitv. or Volume throuoh Treatment
All the alternatives employ an irreversible treatment as a primary element to address the
principal threat 01 contamination~
Reduction in toxicity, mobility, and volume 01 contaminants in ground water would best be
accomplished by alternatives 85 and 86. Alternative 84 would remove contaminants from
ground water and indirectly reduce toxicity and volume through photodegradation 01 the
contaminants. Alternative 83 would reduce toxicity, mobility and volume 01 contaminants, but
would produce 10 to 20 tons 01 non-hazardous sludge annually requiring disposal.
Criterion 5: Short-Term Effectiveness
None 01 the alternatives would result in adverse short-term effects 10r community and worker
protection. However, Alternative 86 would require two to five years to achieve clean up, whereas
alternatives 83, 84 and 85 are estimated to achieve clean up within one year.
Criterion 6: Imclementabilitv
Alternative 84 would most easily be implemented because the air stripper used in this
alternative is currentJy in operation as part 01 the KN removal action. Alternative 85 would pose
no undue problem with regard to this criterion. Alternative 83 would present no technical
difficulties but requires the additional burden 01 disposing 01 residual sludge. Alternative 86
would be more difficult to implement because 01 the need for treatability studies to better
understand the applicability 01 in situ bioremediation to the site.
All alternatives require ground water monitoring. Alternative 84 additionally requires air
monitoring. Monitoring activities will be coordinated with the State of Wyoming.
Criterion 7: Cost
Wrth the air stripper already in place, Alternative 84 has minimal capItal costs. Its present worth
01 $247,917 is also the least among all alternatives. Alternative 86 is the next most expensive
with a present worth 01 $334,553. Alternatives 85 and 83 are the most costly I with present
worth estimates 01 $577,217 and $750,502, respectively.
Criterion 8: State Accectance
State acceptance for this alternative is the same as described above for Alternative V6 for the
VHO plume.
Criterion 9: Community Accectance
Community acceptance for this alternative is the same as described above for Alternative V6 for
the VHO plume.
32
-------
mbtoo6
IX. SELECTED REMEDY
EPA has selected the combination of alternatives V6 and B4 as the remedy for the ground
water operable unit for the Mystery Bridge site. This remedy is made up of the following
components:
Common Elements
.
O'
.
Monitoring ground water, discharged treated water, and air; and
Implementation of institutional controls.
VHO Plume: Alternative V6
.
Extraction of ground water with concentrations of VHOs above MCLs or proposed
MCLs in the upgradient portion 01 the plume (Le., on and/or near the Dow/DSI
facility) ;
.
Treatment of contaminated ground water with an on-site air stripping facility;
Reinjection of treated water into the aquifer to provide additional hydraulic
containment of the upgradient portion of the VHO plume being extracted,
minimize any impact from the VHO remediation efforts on the RCRA plume and
8ETX plume, and enhance the natural attenuation process in the downgradient
portions 01 the VHO plume; and
.
Reliance on natural processes for reduction 01 VHO levels in downgradient
portions 01 the VHO plume.
BET)( Plume: Alternative B4
.
.
Extraction 01 ground water with concentrations 01 8ETX compounds above MCLs
, or proposed MCLs throughout the plume;
.
Treatment 01 contaminated ground water with an on-site air stripping facility; and
Reinjection 01 treated water into the aquifer to provide additional hydraulic control
01 the 8ETX plume and minimize any potential impact from the 8ETX remediation.
efforts on the RCRA and VHO plumes.
.
Alternative 84 assumes continuation 01 the ongoing KN removal action. This removal action
would be expanded, if necessaty, to recover any hydrocarbons originating from the KN
operation that may exist outside of KN's facility. In addition, since no ground water in the
residential areas is believed to be contaminated with 8ETX originating from KN at
concentrations above MCls or proposed MCls, this remedy requires that no ground water
contaminated above such levels will be allowed to enter the subdivision from the KN property.
Periodic monitoring will be used to eyaluate compliance with this condition.
The remediaJ design will specify the appropriate number and location 01 wells and monitoring
points, and system parameters such as flow rates for both the VHO and BETX ground water
treatment systems. Some modifications or refinements may be made to the remedy during
remediaJ design and construction. Such modifications or refinements, in general, would reflect
results 01 the engineering design process. Estimated cost for the selected remedy is $600,739.
Details 01 the costs for each of the VHO and 8ETX remedies are shown in Table 6.
33
-------
'T1broa6
The selection of this remedy is based upon the comparative analysis of alternatives presented
above, and provides the best balance of tradeoffs with respect to the nine evaluation criteria.
ARARs for the selected remedy are shaded in the table provided as Exhibit 1. As pointed out in
the comparative analysis, the impact of each VHO plume aJternative on the RCRA plume was
carefully considered. The close proximity of these two plumes prescribes a remedy that would
not adversely affect the extent of the RCRA plume. VHO plume alternatives which include
limited ground water extraction and minimally disturb the aquifer down gradient of the source
areas meet this need. Air stripping was chosen as the appropriate treatment technology
applied to the extracted ground water by weighing the factors outlined in the comparative
analysis. Natural attenuation was chosen over in situ bioremediation for the downgradient
portion of the VHO plume in Alternative V6 because it would not adversely impact the RCRA
plume in any way, does not require treatability studies, is effective at the existing level of
contamination, and has less uncertainty than bioremediation with regard to remediation time
frame. The selection of Alternative B4 as the remedy for the BETX plume was also based upon
the comparative analysis. A particular strength of this alternative is that it is already in place
and has been proven effective as part of the KN removal action.
Based on the findings in the BAA for the Current Resident and Future Hypothetical Resident
scenarios (see Table 3), the remedial action objectives for this site are the following:
Q
1) Prevent ingestion of water containing t-1,2 DCE, 1,1,1 TCA, TCE, PCE, benzene,
toluene, ethylbenzene, or xylene at concentrations that either a) exceed MCLs or
proposed MCLs, or b) present ~ total carcinogenic risk range greater than
1 x1 ()-4 -1 x1~; and
2) Restore the alluviaJ aquifer to concentrations that both a) meet the MCLs or proposed
MCLs for t-1 ,2 DCE, 1,1,1 TCA, TCE, PCE, benzene, toluene, ethylbenzene, and xylene,
and b) present a total carcinogenic risk range less than 1 x1 ()-4 -1 x1 (}6.
Remedial action goals specifically delineate action levels, area of attainment. and restoration
time frame. The action levels are MCls and proposed MCls (as shown previously in tables 1
and 2). Attainment of these action levels will provide protectiveness of human health and the
environment. The area of attainment shaJl be the entire VHO and BETX plumes. including
those areas of the plumes within and outside the Dow/DSI and KN properties. Based on the
contaminant transport modeling performed for the RI/FS, the restoration time frame for this
remediaJ action shaJl be six years, with the expectation that remediation of the BETX plume
should be no longer than one year, and with the acknowledgement that the restoration time
frame may vary depending upon the outcome 01 OU 2 in addressing remaining sources, and
other factors described below.
A further objective of this remediaJ action is to restore the ground water, with the exception of the
area impacted by the RCAA plume, to its beneficiaJ use, which is, at this site, a drinking water
aquifer. Based on information obtained during the RI, and the anaJysis of all remedial
alternatives, EPA and the State 01 Wyoming believe that the selected remedy will achieve this
objective. It may become apparent, during implementation or operation of the ground water
extraction system, that contaminant levels have ceased to decline and are remaining constant at
levels higher than the remediation goaJ. In such a case, the systems' performance standards
and/or the remedy may be reevaluated.
34
-------
Table 6: Selected Remedy Costs
Page 1 of 2
"
VHO Plume
I Item Cost
Direct Caoital Costs
Temporary Deed and/or User Restrictions $15.000
Extraction Well System Installation $3.500
Well Installation Supervision $1.110
Well Pumps $2.500
Influent and Discharge Piping $5.000
Piping Installation $4.000
Air Stripper System $57.000
Air Stripper System Installation $14,000
Discharge Pump $2,500
Mobilization $7.000
Equipment Decontamination $5.000
Health and Safety Program $10.000
Estimated Direct Capital Cost $126.610
Indirect Cacital Costs
Contingency Allowance (25%) $31.653
Engineering Fees (15%) $18.992
Legal Fees (5%) $6.331
Estimated Indirect Capital Cost $56.975
Total Estimated CapitaJ Cost $183.585
Annual Oceration and Maintenance Costs
Ground Water Sample Collection $2,600
Ground Water Sample Analysis $8,400
Electricity (pumps, blower) $4,320
Air Stripper Operation $23,360
Air Stripper Maintenance $13,440
Air Stripper Cleaning Solution $1 .500
Discharge Sampling (water) $11,680
Discharge Analysis (water) $54,750
Air Stripper Vapor Discharge Sampling $1 ,664
Vapor Sample Analysis $1.200
Estimated Annual Ooeratlon and Malnenance Cost $122,914
Present Worth of AnnuaJ Operation and Maintenance Costs (1-5%) $170,237
Total EStimated Cost VHO Plume. . . . $353,822
From.' RIfFS Report (June 1990)
35
-------
Table 6: Selected Remedy Costs
Page 2 of ,
BEn< Plume
Item Cost
Direct Cacital Costs
Temporary Deed and/or User Restrictions $15,000
Influent and Discharge Piping $4,000
Piping Installation $600
SVE Wells $10,500
Product Recovery Well. $4,500
Product Recovery Pump $2,500
Vacuum Pump $7,500
Well Installation Supervision $1,850
Mobilization $3,000
Equipment Decontamination $500
Health and Safety Program $500
Estimated Direct Capital Cost $50.450
Indirect Cacital Costs
Contingency Allowance (25%) $12,613
Engineering Fees (15%) $7,568
Legal Fees (5%) $2.523
Estimated Indirect Capital Cost $22,703
Total Estimated Capital Cost $73,153
An/;lual Oceration and Maintenance Costs
Ground Water Sample Collection $2,600
Ground Water Sample Analysis $8,400
Electricity (pumps, blower) $6,000
Air Stripper Operation $6,400
Air Stripper Maintenance $3,200
Air Stripper Cleaning Solution $1,700
Discharge Sampling (water) $3,200
Discharge Analysis (water) $15,000
SVE Vapor and Stade DIscharge Sampling $1,664
Vapor Sample Analysis $2.400
Estimated Annual Ogeration and Mainenance Cost. $SO,S64
Present Worth of AnnuaJ Operation and MaJntenance Costs (1-5%) $174,765
Total estimated Cost BETX Plumsq .. $247,917
.,
. From: RI/FS Report (June 1990)
36
-------
moroa6
"
The selected remedy will include ground water extraction for an estimated period of at least
one year for the VHO plume and less than one year for the BETX plume, during which time the
systems' performance will be carefully monitored on a regular basis and adjusted as warranted
by the performance data collected during operation. The operation monitoring period will be
determined during remedial design. The operating system may include discontinuing
operation of extraction wells in areas where cleanup goals have been attained, alternate
pumping at wells to eliminate stagnation points, and pulse pumping to allow aquifer
equilibration and encourage adsorbed contaminants to partition into ground water for
extraction and treatment.
x. STATUTORY DETERMINATIONS
EPA's primary responsibility at Superfund sites is to select remedial actions that are protective
of human health and the environment. CERCLA also requires that the selected remedial action
for the site comply with applicable or relevant and appropriate environmental standards
established under Federal and State environmental laws, unless a waiver is granted. The
selected remedy must also be cost-effective and utilize permanent treatment technologies or
resource recovery technologies to the maximum extent practicable. The statute also contains a
preference for remedies that include treatment as a principal element. The following sections
discuss how the selected remedy for contaminated ground water at the Mystery Bridge site
meets these statutory requirements.
Protection of Human Health and Environment
In order to meet the remedial objectives outlined in the previous section, the risk associated
with exposure to the contaminated ground water must fall within the acceptable risk for
carcinogens. Attainment of MCLs and proposed MCLs will assure site risk falls within this
range. The selected remedy protects human health and the environment by reducing levels of
contaminants in the ground water through extraction and treatment, as well as through natural
attenuation. EPA expects VHOs in ground water would be reduced to MCLs or proposed
MCLs in six years and MCLs or proposed MCLs for BETX compounds would be attained within
one to two years. However, there is a minimal chance that complete remediation may take as
long as 18 years. Together with deed and/or user restrictions and the existing municipal water
supply, the threat of exposure currently posed to residents from contamiRated ground water
would be significantly reduced if not eliminated. Of all the alternatives for both the VHO and
BETX plumes, the selected alternatives provide the best protection to human health without
significant adverse impact to the environment. No unacceptable short-term risks or cross-
media impacts would be caused by implementing this remedy.
Attainment of Applicable or Relevant and Appropriate Requirements of Environmental
Laws
All ARARs would be met by the selected remedy.
Chemical Soecific ARARs. The selected remedy would achieve compliance with chemical
specific ARARs related to the downgradient ground water and ambient air quality at the site.
The relevant and appropriate requirements include primary drinking water standards
established by the Safe Drinking Water Act. Some cOr:1taminants of concern identified for the
site have MCLs. MCLs have been proposed for the remaining contaminants of concern and
are to be considered. Values for the MCLs and proposed MCLs are shown on Table.1 for the
VHO compounds and on Table 2 for the BETX compounds. Concentrations of BEn<
compounds throughout the entire BETX plume would be reduced below MCLs or proposed
MCLs by the Alternative B4 treatment system. Concentrations of VHO compounds in the
37
-------
merod6
while natural attenuation would reduce concentrations in the downgradient portion of the
plume to below MCLs or proposed MCLs.
Benzene emissions from the air stripping treatment system will be monitored and if required,
controls would be implemented to ensure would compliance with the National Emission
Standards for Hazardous Air Pollutants (NESHAP). At present it is not expected that
constituents for which standards have been established by the Wyoming Air Quality Rules and
Regulations will be produced in the treatment process. In the unlikely event that constituents
are produced, the necessary controls would be implemented in order for the emissions to
comply with the regulations.
Action Specific ARARs. The selected remedy would address and comply with action specific
ARARs for injection of treated water back in to the ground according to Wyoming UIC program
established by 40 CFR 147 and Wyoming Water Quality Rules and Regulations, Chapter IX.
The ground water monitoring program which includes wells located upgradient, downgradient,
and within the contaminated ground water would fulfill the requirements of the RCRA corrective
action program.
$)
:J
Land disposal restrictions are not applicable to the selected remedy. Instead, RCRA section
3020 applies to reinjection of treated ground water into Class IV injection wells during CERCLA
response actions. Since the goal is to clean up ground water to drinking water levels, health-
based drinking water standards (MCLs), rather than land disposal restrictions, are the relevant
and appropriate clean up standard.
RCRA requirements would be met as appropriate for owner and operators of hazardous waste
treatment, storage, and disposal facilities. BACT analysis for construction, modification, and.
operation of the water treatment systems would comply with the requirements of Wyoming Air
Quality Rules and Regulations and discharges would not be concealed. Similarly, BACT permit
and data requirements for the ground water extraction/injection system would comply with
Wyoming Water Quality Rules and Regulations.
Location Specific ARARs. The selected remedy would address and comply with all location
specific ARARs for preservation and protection of the North Platte River floodplain according to
the requirements of 40 CFR 6.302. RCRA location standards for treatment, storage and
disposal facilities are relevant and appropriate for temporary storage tanks of recovered
hydrocarbons.
Cost Effectiveness
EPA believes the selected remedy is cost-effective in mitigating the principal risk posed by .
contaminated ground water within a reasonable period 01 time. Section 300.430(~(ii)(D) 01 the.
NCP requires EPA to evaluate cost-effectiveness by comparing all the alternatives which meet
the threshold criteria: protection of human health and the environment, against three additional
balancing criteria: long-term effectiveness and permanence; reduction of toxicity, mobility or
volume through treatment; and short-term effectiveness. The selected remedy meets these
criteria and produces the best overall effectiveness at the lowest reasonable cost. Therefore,
the selected remedy is cost-effective as defined in the NCP. The estimated cost for the
selected remedy is over $600,000.
38
-------
mbr0d6
(J
Utilization of Permanent Solutions and Alternative Treatment Technologies or Resource
Recovery Technologies to the Maximum Extent Practicable
EPA believes the selected remedy represents the maximum extent to which permanent
solutions and treatment technologies can be utilized in a cost-effective manner for the Mystery
8ridge site. Of those alternatives that are protective of human health and the environment and
comply with ARARs, EPA has determined that the selected remedy provides the best balance
of trade-offs in terms of long-term effectiveness and permanence; reduction in toxicity, mobility
or volume achieved through treatment; short-term effectiveness; implementability; and cost,
and also considering the statutory preference for treatment as a principal element and
considering State and community acceptance.
Alternative V6 complies with ARARs; and reduces the toxicity, mobility, and volume of the
contaminants in the ground water equally as well as the other VHO plume alternatives. Short-
term effectiveness and protection of human health and the environment were critical in
choosing Alternative V6 with natural attenuation for the downgradient portion of the VHO plume
in light of effects on the RCRA plume and trade-off with remediation time frame.
Alternative 84 provides long-term effectiveness equally as well as alternatives 83 and 85.
Although Alternative 86 has potential to best provide protection, it would require a greater
remediation time frame and cost more than Alternative B4. Alternative B5 would accomplish a
greater reduction in toxicity, mobility and. volume of contaminants than 84, but at over twice the
cost. Alternative B4 removes contaminants from ground water and will indirectly reduce the
toxicity and mobility through photodegradation. Alternative B3 requires the additional burden
of disposing of 10 to 20 tons 01 non-hazardous sludge annually. Since Alternative 84 would be
a continuation of the ongoing air stripping operation at the KN facility; it would be the easiest to
implement and cost the least of the BETX plume alternatives.
The State 01 Wyoming is in concurrence with the selected remedy. The Proposed Plan for the
Mystery 8ridge site was released for public comment in July 1990. The Proposed Plan
identified aJternatives V6 and B4 as the preferred remedy. EPA reviewed all written and verbal
comments submitted during the public comment period. Upon review 01 these comments, EPA
determined that no significant change to the remedy originally identified in the Proposed Plan
was necessary.
Preference for Treatment as a Principal Element
The selected remedy satisfies, in part, the statutory preference for treatment as a principal
element. The principaJ threat to human health is from ingestion of and direct contact with
contaminated ground water. The selected remedy reduces levels of BETX contaminants and
the highest concentrations of VHO contaminants in ground water through treatment using air
stripper systems. Natural attenuation of the downgradient portion of the VHO plume was
selected over treatment because of the adverse effects on the nearby RCRA that would result
from aquifer drawdown during pumping of that portion of the plume for treatment. If the
downgradient portion 01 the plume is pumped, the RCRA plume could migrate further into the
residential area and thus increase the risk of exposure to contaminated ground water.
\
39
-------
Exhibit 1 - Mystery Bridge ARAAs Evaluation
Page: 1 0115
ARAR CITATION. REQUIREMENT EVALUATION
A. location - Soecitic AAARs
33 CFR 320 '3 Army Corps 0' Engineers Permit Program Regulations pertain to certain actions allecting navigable
Regulations. waters 0' the United States Including discharges 0' dredged
or'lII material. No dredged or .iIl material to be generated.
Regulation Is neither applicable nor retevant and appropriate. .-
40 CFR 6.301 and 36 CFR 800 Action to protecttandmarks, historical, No landmarks, historical, or archaeological sites.
and archaeological slles. Regulation Is neither applicable nor relevant and appropriate.
40 CFR 6.302 Action to preserve and protect wetlands, Acllon likely In floodplain 0' North Plalte River; other items
"oodplalns, tmportant 'armlands, coastal not applicable. Regulation is applicable.
zones, wild and scenic rivers, fish and
wildlife, and endangered species.
40 CFR 230 Guidelines for specification of disposal No dredged or fill material to be generated. Regulation is
sites for dredged or fill material. neither applicable nor relevant and appropriate.
40 CFR 264.18 location standards for treatment, storage, II temporary storage tanks 0' recovered hydrocarbons are used,
and disposal facilities. regulation may be applicable.
50 CFR 200 Action to conserve endangered species No endangered or threatened species. Regulation is neither
or threatened species. applicable nor relevant and appropriate.
50 CFR 402 Acllon to conserve endangered species No endangered or threatened species. Regulation is neither
or threatened species. applicable nor relevant and appropriate. -- --
16 U.S.C. 1131-36 Actions to preserve federally owned No wilderness area Involved. Regulations are neither applicable
50 CFR 35.1-.14 wilderness areas as wilderness areas. nor relevant or appropriate.
16 U.S.C. 1451-64 Actions must be consistent wilh a state's No coastal zone involved. Regulation is neither applicable nor
approved coastal zone management program. relevant or appropriate. ~ ---- -
33U.' .03 Permitting requirements 'or structures or The proposed remedial actions will not alleet navigable wate.
33 CH, __0-30 work In or allectlng navigable waters. Regulations are neither applicable nor releva~~~ apP!9e!j~~:
-------
;:,
.'
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 20115
..
ARAft CITATION ftEQUIRI;MENT EV ALUA TION
Wyoming Water Quality Location criteria lor the design and The remedial action will not use commerclaU
Rules and Regulations construction 01 biological and non- industrial water and wastewater ponds. Regulation is
Chapter IX, Part C biological treatment ponds' that accept neither applicable nor relevant or appropriate.
Sections 28(a) and 3O(a). commerclaUlndustrlal waste and waste water.
B. Chemical - Snecific ARARs
..
40 CfR 141.11 National RevIsed Primary Drinking Water Relevant and Appropriate: ground water concentrations must not
Regulations: maximum contaminant exceed maximum contaminant levels.
levels 101 OIganlc chemicals. Constituents 01 concern Identllied lor the site lor
which MCLs have been promulgated include: 1,1,1- trichloroethane,
trichloroethene, and benzene. Proposed MCLs are to be considered.
40 CfR 143.3 National Secondary Drinking Water Non-enlorceable, non health-based concentrations lor drinking
Regulations: secondary maximum contaminant water. Regulation, although not enlorceable. should be considered.
levels.
40 CfR 141.50 Maximum Contaminant Level Goals: Non-enlorceable health goals lor public water systems.
drinking water quality goals set at Regulation Is relevant or appropriate lor constituents 01
levels 01 no known or anticipated concern with an MClG greater than zero.
adverse health effects; with a
margin 01 salety.
Clean Water Act Section 304 Ambient Water Quality Criteria lor Applicable or Relevant and Appropriate: concentrations
Protection 01 Aquatic lile and In any surlace water must not exceed water quality criteria
Human Health. as a result 01 receiving ground water.
.--
40 CfR 50.5 National Secondary Ambient Air Quality At present ills not expected that sullur oxides will be produced
Standards lor Sulfur Oxides. In the treatment process. In the unlikely event that
sulfur oxides are produced. regulalion would be apphcab~~____u -.-
40 CFA 50.6 National Primary and Secondary Ambient At present it is not expected that particulales will be produced
Air Quality Standards lor Particulales. In the treatment process. In the unlikely evenl thai
particulates are produced. regulation wou~cJ ~ ~~I~~~~~. - --
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 30115
-~..-
ARAR CITATION REQUIREMENT EVALUATION
40 CFR 61 National Emission Standards lor Hazardous Regulations lor benzene emissions are applicable
Air Pollutants. tor air stripping treatment system.
~
40 CFR 50.8 National Primary Ambient Air Quality At present it is not expecled that carbon monoxide will be produced
Standards tor Carbon Monoxide. In the treatment process. In the unlikely eventlhal
carbon monoxide Is produced, regulation would be applicable. ..
Wyoming Water Quality Rules Water quality Slandards tor Wyoming Federal requirements equal to or more slringenllhan
and Regulations, surface waters. State requirements. Regulation Is neither applicable
Chapter 1. nor relevant and appropriale.
Wyoming Water Quality Rules Water quality standards tor Wyoming Federal requirements equal to or more stringenllhan
and Regulations. Chapter ground waters. State requirements. Regulations are neilher applicable
VIII, SeCtions 3 and 4. nor relevant and appropriate.
Wyoming Air Quality Rules Air quality Slandards tor partlculales. At present It Is nol expected that partlculales will be produced
and Regulations, Section 3 In the treatment process. In the unlikely event that
(except tor (a)(iil) )., particulates are produced, regulation would be applicable.
Wyoming Air Quality Rules Air quality standards tor sultur oxides. At present It is not expected thai sullur oxides will be produced
and Regulations, Section 3 In the treatmenl process. In the unlikely evenllhal
(except tor (a)(iii) ). sultur oxides are produced, regulation would be applicable.
..
Wyoming Air Quality Rules Air quality standards tor sulturic acid AI present II Is not expected Ihat sulfuric acid mislS will be
and Regulations, Seetlon 6. mist. produced in Ihe treatment process. In the unlikely evenllhat
sulturic acid mislS are produced, regulalion would be applicable.
--
Wyoming Air Quality Rules Air quality standards tor hydrogen sulfide. At present it is not expected that hydrogen sulfide will be
and Regulations. Seetlon 1. produced In Ihe trealment process. In the unlikely event Ihal
hydrogen sulfide is produced, regulation would be applicabh:i.
Wyoming Air QualilY Rules Air qualily standards tor photochemicals. At presenlll is not expecled Ihal photochemicals will be
and Regulations, Secllon 8. produced in Ihe Irealmenl process. In Ihe unlikely evenllhal
pholochemicals are produced, regulation would be applicabll .-- - .
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 4 01 15
-
ARAR CITATION , REQUIREMENT EVALUATION
Wyoming Air Quality Rules Air quality standards lor nitrogen oxides. At present it Is not expected that nitrogen oxides will be
and Regulations. Section 10 . produced In the treatment process. In the unlikely ellent that
(except lor a). nitogen oxides are produced, regulation would be applicable.
Wyoming Air Quality Rules Air quality standards lor lIuorides. At present it Is not expected that lIuorides will be
and Regulations. Section 11. produced in the treatment process. In the unlikely ellent that
lIuorides are produced. regulation would be applicable.
Wyoming Air Quality Rules Air quanty standards lor carbon monoxide. At present it is not expect~ that carbon monoxide will be produced
and Regulations, Section 12. In the treatment process. In the unlikely event that
carbon monoxide is produced. regulation would be applicable.
Wyoming Air Ouality Rules Air quality standards lor parliculate At present it Is not expected that particulate emissions will be
and Regulations. Section 14. emIssIonS. produced In the treatment process. In the unlikely event that
particulate emissions are produced. regulation would be applicable.
Wyoming Air Quality Rules Air quality standards lor odors. At present II is not expected that odors will be
and Regulations. Section 16. produced In the treatment process. In the unlikely event that
odors are produced. regulation would be applicable. --
C. Action - Soecific ARARs
-.
40 CFR 122 EPA Administered Permit Programs: The Regulation relers to discharges Irom treatment system.
National Pollutant Discharge Elimination Substanllve requirements are applicable or relevant and
System. appropriate lor alternatives that propose discharges to oil-site
sur lace water body, and relevant and appropriate lor discharges
to on-site sur lace water body. . -- ---
40 CFR 125 Criteria and standards lor the National Substantive requirements are applicable or relevant and
Pollutant Discharge Elimination System. appropriate lor allernatives that propose discharges to oil-site
sur lace water body. and relevant and appropriate 101 discharges
to on-site surlace water body. _d__- -
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 5 01 15
~-_.
ARAA CITATION. REQUIREMENT EVAlUATION
-
40CFR 129 Establishes effluent limitations lor None 01 the Identilied compounds have been observed at the site.
certaIn pollutants. Regulation Is neither applicable nor relevant and
appropriate.
40 CFR 136 GuidelInes establishing test procedures Substantive requirements are applicable or relevant and
lor the analysis 01 pollutants. appropriate 101 alternatives that propose discharges to oil-site
surlace water body. and relevant and appropriate lor discharges
to on-site surlace water body.
---
40 CFR 144 Underground Injection Control Program Deler to State 01 Wyoming regulations. Regulations is neither
applicable nor relevant and appropriate.
--
40 CFR 146 Underground Injection Control Program: Deler to State 01 Wyoming regulations. Regulations is neither
criteria and standards. applicable nOl relevant and appropriate.
40 CFR 141 Wyoming underground Injection control Regulation is applicable
programs. lor Injection 01 treated ground water back Into aquifer.
n
40 CFR 221 Apptlcatlons lor ocean dumping permits. Ocean dumping is not viable alternative. Regulation neither
applicable nor relevant and appropriate.
40 CFR 264 Standards 101 owners and operators 01 See below.
(specified sections) hazardous waste treatment. stOlage, and
disposallacilities.
40 CFR 264.91 - 100 Requirements lor releases Irom Solid Waste Solid Waste Management Units not envisioned. Regulation
Management Units. neither applicable nor relevant and appropriate lor ground
waler remediation.
--.---
40 CFR 264.91 Required programs. Solid Waste Management Units not envisioned. Regulation
neither applicable nor relevant and appropriale lor ground
waler remedialion-
--------_.-
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 60115
AAAR CITATION ..
REQUIREMENT EVALUATION
40 CFR 264.92 Ground Water protection standard. Solid Waste Management Units not envisioned. Regulation
neither applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.93 Hazardous constituents. Solid Waste Management Units not envisioned. Regulation
neither applicable nor relevant and appropriate lor ground
water remediation.
--
40 CFR 264.94 Concentration limits. Solid Waste Management Units not envisioned. Regulation
neither applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.95 Points 01 compliance. Solid Waste Management Units not envisioned. Regulation
neither applicable nor relevant and appropriate lor ground
water remediation.
-
40 CFR 264.96 Compliance period. Solid Waste Management Units not envisioned. Regulation
neither applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.91 General ground water monitoring Solid Waste Management Units not envisioned. Regulalion
requirements. neither applicable nor relevant and appropriate lor ground
water remediation.
-----
40 CFR 264.98 Detection monitoring program. Solid Waste Management Units not envisioned. Regulalion
neither applicable nor relevant and appropriate tor ground
water remediation.
-.
40 CFR 264.99 Compliance monitoring program. Solid Waste Management Units not envisioned. Regulation
neither applicable nor relevant and appropriate lor ground
water remediation.
~- ------ ----- -
40 CFR 264.100 Corrective action program. Establishes ground water monitoring program 10 demonslrate
etlecliveness 01 corrective action. Subslantive wquirements
01 regulal~ons are potenl~~relevan~~~~ ~)plOeli~!~: . ---
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 7 of 15
--.
AAAR CITATION REQUIREMENT EV AlUA TION
40 CFR 264.111 Closure performance standard. Regulation neither applicable nor relevant and. appropriate.
-~_.
.,
40 CFR 264.117 POSI-closure care and use 01 property. Regulation pertains to closure 01 hazardous waste disposal
'acllitles. Hazardous waste disposal facilities not
envisioned. Regulation neither applicable nor relevant and
appropriate 'or ground water remediation. ---.
40CFR264.171-118 Use and management of hazardous waste Regulation neither applicable nor relevant and appropriate -
containers. does not pertain to this site.
40 CFR 264.111 Condition 01 conlalners. Regutation neither applicable nor relevant and appropriate -
does not pertain to this site.
40 CFR 264.112 Compatibility 01 waste with containers. Regulation neither applicable nor relevant and appropriate -
does not pertain to this site.
40 CFR 264.113 Management 01 conlainers. Regulation neither applicable nor relevant and appropriate -
does not pertain to this site.
40 CFR 264.114 Inspections. Regulation neither applicable nor relevant and appropriate -
does not pertain 10 this site.
40 CFR 264.175 Containment. Regulation neither applicable nor relevant and appropriate -
does nol perlaln to this site. .-
40 CFR 264.176 Special requirements lor Igitable or Regulation neither applicable nor relevant and appropriate -
reactive waste. does not pertain to this site.
- -- -
40 CFR 264.177 Special requirements lor incompatible Regulation neither applicable nor relevant and appropriate -
wastes. does not pertain to this site. --.
40 CFR 264.178 Closure. Regulation neither applicable nor relevant and appropriate.
does not pertain to this site.
.---
-------
D
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 8 01 15
ARAR CITATION REQUIREMENT EV ALUA TION
40 CfR 264.190 - 198 Requirements for facilities that use tank systems II remedy includes the use of tanks to store or manage RCRA
fOl SIorlng 01 treating hazardous waSle. wastes, these regulations are applicable.
40 CfR 264.190 Applicability. I II remedy includes the use ollanks 10 slore or manage RCRA
wastes, this regulalion Is applicable. 0-
40 CfR 264.191 Assessment of existing tank syslem's II remedy includes Ihe use ollanks 10 slore or manage RCRA
integrity. wastes, this regula lion is applicable.
40 CfR 264.192 DesIgn and InSlallation of new tank II remedy includes the use 01 tanks to store or manage RCRA
sySIems 01 components. wastes, this regulation Is applicable.
40 CfR 264.193 Containment and detection of releases. II remedy includes the use 01 tanks to store or manage RCRA
wastes, this regulation Is applicable.
40 CfR 264.194 General operating requirements. II remedy includes the use 01 tanks to store or manage RCRA
wastes, this regulation Is applicable. ..
40 CfR 264.195 Inspections. II remedy includes the use 01 tanks to store or manage RCRA
wastes, this regulation Is applicable.
-
40 CfR 264.196 Response to leaks or spills and disposition of II remedy includes Ihe use 01 tanks 10 slore or manage RCRA
leaking or until tank systems. wastes, this regulation Is applicable.
40 CfR 264.191 Closure and pOSI-closure care. II remedy includes the use 01 tanks 10 slore or manage RCRA
wastes, this regulation is applicable.
40 CFR 264.198 Special requirements lor ignitable II remedy Includes the use 01 tanks 10 slore or manage RCRA
or reactive wasle. wasles, Ihls regulalion Is applicable.
-.---.-
40 CFR 264.220 - Requirements for surlace impoundmenls. SUI lace impoundmenls not envisioned. Regulalion is
221,226-228 neilher applicable nor relevanl and appropriale lor
ground water remedialion. ---- ---- -- -
-------
Exhibil1 - Myslery Bridge ARARs Evalualion
Page: 9 01 1~
ARAR CITATION REQUIREMENT ~.~.
EVALUATION
40 CFA 264.220 Applicability. Surlace impoundments not envisioned. Regulalion is
neither applicable nor relevant and appropriate lor
ground water remediation.
--
40 CFA 264.221 DesIgn and operating requirements. Surlace impoundments not envisioned. Regulation is
neither applicabte nor relevant and appropriate lor
ground water remediation.
-
40 CFA 264.226 Monllorlng and Inspection. Surlace impoundments not envisioned. Regulation is
neither applicable nor relevant and appropriate lor
ground water remediation.
40 CFA 264.221 Emergency repairs; contlgency ptans. Surlace impoundments not envisioned. Regulation is
neither appticable nor relevant and appropriate lor
ground water remediation.
40 CFA 264.228 Closure and posl-closure care. Sur lace impoundments not envisioned. Regulation is
neither applicable nor relevant and appropriate lor
ground water remediation.
40 CFA 264.251 Waste plies: design and operating Waste piles not envisioned. Regulation Is neilher
requlremenls. applicable nor relevant and appropriate lor ground waler
remediation.
40 CFA 264.258 Waste plies: closure and post-closure Waste piles not envisioned. Regulation Is neither
care. applicable nor relevant and appropriate lor ground waler
remediation.
40 CFA 264.211.213. Requiremenls lor land treatment. Land treatment not envisioned. Regulation is neither
276.218.281-282 applicable nor relevant and appropriate lor ground
water remediation.
-- -- --~._._- - - .----
40 CFR 264.271 Treatment program. land trealment nOI envisioned. Regulation is neither
applicable nor relevant and approprlale lor ground
waler remedial ion.
---_.
-------
c
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 100115
ARAR CITATION REQUIREMENT EVALUATION
40 CFR 264.273 Design and operating requirements. Land treatment not envisioned. Regulation is neilher
applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.276 Food chain crops. Land treatment not envisioned. Regulation is neither
applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.278 Unsaturated zone monitoring. Land treatment not envisioned. Regulation is neither
applicable ....or relevant and appropriate lor ground
water remediation.
40 CFR 264.280 Closure and pOSI-closurecare lor Land treatment not envisioned. Regulation is neither
land treatment units. applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.281 Special requirements lor Ignitable or Land treatment not envisioned. Regulation is neither
reactive wastes. applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.282 Special requirements lor incompatible Land treatment not envisioned. Regulation is neither
wastes. applicable nor relevant and appropriate lor ground
water remediation.
40 CFR 264.301,303 Requirements lor landlills. Landlills not envisioned. Regulation Is neither
304,310,314. applicable nor relevant and appropriate lor ground
water remediation.
---
40 CFR 264.301 Design and operating requirements. Landlills not envisioned. Regulation is neither
applicable nor relevant and appropriale lor ground
water remediation.
-------- .
40 CFR 264.303 MDnitorlng and Inspection. landfills not envisioned. Regulalion is neither
applicable nor relevant and appropriate tor ground
waler remediation.
- -- .-
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 11 of 15
AAAR CIT A TIQN REQUIREMENT -.
. .' EVALUATION
40 CfR 264.310 Closure and post-closure care. landlills not envisioned. Regulation is neither
applicable nor relevant and appropriate for ground
water remediation.
40 CfR 264.314 Special requirements lor bulk landlills not envisioned. Regulation is neither
and containerized liquids. applicable nor relevant and appropriate lor ground
water remedialion.
40 CfR 264.340.341 Requirements for Incinerators. tncinerators not envisioned. Regulation is neither
343.345.351 applicable nor relevant and appropriate lor ground
water remediation.
40 CfR 264.340 Applicability. Incinerators not envisioned. Regulation Is neither
applicable nor relevant and appropriate lor ground
water remediation.
40 CfR 264.341 Waste analysis. Incinerators not envisioned. Regulation Is neither
applicable nor relevant and appropriate lor ground
water remediation.
40 CfR 264.343 Perlormance slandards. Incinerators nol envisioned. Regulation is neither
applicable nor relevant and appropriate lor ground
water remediation.
40 CfR 264.345 Operating requirements. Incinerators not envisioned. Regulation is neither
applicable nor relevant and appropriate for ground
water remediation.
40 CfR 264.351 Closure. Incinerators not envisioned. Regulation is neither
applicable nor relevant and appropriate for ground
water remediation.
40 CFR 267 tnt/3rim standards lor owners and operators Hazardous waste land disposal lacilities not envisioned.
(specil' 1<:tions) 01 new hazardous waste land disposat Regulation neither applicable nor relevant and
facilities. appropriate for ground water remediation.
--------~ -~ -
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 120115
-u
ARAR clr A rlON REQUIREMENT EVALUATION
40 CFR 267.10 Environmental performance slandard. Hazardous wasle land disposal lacilities not envisioned.
Regulation neither applicable nor relevant and
appropriate lor ground waler remedial ion.
40 CFR 267.23 Closure and post-closure. Hazardous wasle land disposal lacililies not envisioned.
Regulation neither applicable nor relevant and
appropriate lor ground waler remediation. -
40 CFR 268 Land disposal restrictions. Land disposal reslriclions are not applicable 10 Ihese activities.
Inslead oi LDR, RCRA secli~n 3020 applies 10 relnJeclion 01 treated
ground waler Inlo Class IV injection wells during CERCLA response
actions. Moreover, lor CERCLA response action where, as here, Ihe
goal Is to clean up ground waler 10 drinking waler levels, the
Agency believes Ihat health-based drinking waler slandards
(e.g.. MCLs), ralher IhalLDRs, will generally be Ihe relevanl
and appropriate clean up slandard.
40 CFR 268.30 Waste-specific prohibitions lor solvent Ground water injection exempt Irom land disposal
wastes. reslrlctions lor solvent wastes. Therelore, regulation is
neither applicable nor relevant and appropriale lor injeclion
of treated ground waler. --
40 CFR 268.41 Treatr.nent slandard expressed as Regulation may be applicable lor land disposal 01
concentration In wasle exlract. sludge from blologicallreatment 01 ground water.
40 CFR 268.50 Reslricts slorage of hazardous waSle. Proposed remedial actions do nOI include hazardous
wasle storage lor more than 90 days. Regulation Is neilher
applicable nor relevant and appropriale.
40 CFR 270 EPA Adminstered Permil Program: The Regulation neilher applicable nor relevanl and appropriale:
Hazardous Wasle Permit Program. adminiSlralive aClions are waived lor Superlund remedial
actions. ---
40 CFR 403 General pretrealmenl regulalions lor Regulation neilher applicable nor relevant and
existing and new sources 01 pollution. appropriate - not pertinent to sile. .-- . _. _.. ---_._~
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 130115
ARAA CITATION. REQUIREMENT EVALUATION
Wyoming Water Quality Rules Data requirements lor permit applications Regulation incorporates treatment 01 ground water
and Regulations, lor the construction 01 treatment works, exceeding MCLs. Regulation Is applicable.
Chapter III, Section 15 disposal systems, and other,potential
sources 01 pollution.
Wyoming Water Quality Rules Permit requirements lor construction, Substantive requirement 01 BACT analysis are applicable.
and Regulations, Chapter IX. modllicatlon, and operation (BACl).
--
Wyoming Water Quality Rules Requirements lor design and operation No sewerage or water works or land application
and Regulations, Chapter XI, 01 sewerage and public water works, lacilities are proposed. Regulations are neither applicable
Section 5. and land application. nor relevant and appropriate.
Wyoming Water Quality Rules' Requirements lor design and operation No sewerage or water works or land application
and Regulations, Chapter XI, 01 sewerage and publiC water works, lacilitles are proposed. Regulations are neither applicable
Section 24, and land application. nor relevant and appropriate.
Wyoming Water Quality Rules Requirements lor design and operation No sewerage or water works or land application
and Regulations, Ghapter XI, 01 sewerage and public water works, lacilities are proposed. Regulations are neither applicable
Sections 50 and 53. and land application. nor relevant and appropriate.
Wyoming Water Quality Rules Requirements lor design and operation No sewerage or water works or land application
and Regulations, Chapter XI, 01 sewerage and public water works, lacilities are proposed. Regulations are neither applicable
Part C. and land application. nor relevant and appropriate.
Wyoming Water Quality Rules Requirements lor design and operation No sewerage or water works or land application
and Regulations, Chapter XI, 01 sewerage and public water works, lacilities are proposed. Regulations are neither applicable
Part C. and land application. nor relevant and appropriate.
-~--
Wyoming Water Quality Rules General requirements lor discharge Irom federal requirements equal to or more stringent than Slate
and Regulations, Chapter XI, wastewater treatment lacility. requirements. Regulation is neither applicable nor
Section 25. relevant and appropriate.
- ---_.~-
Wyoming Water Quality Rules R~uirements lor discharge to POTW. Remedial actions do not include discharge
and R 'Ions, Chapter XI, to POTW. Regulation is neither applicable nor relevant
Section '::0. and appropriate. --------- - -- - - -
-------
Exhibit 1 - Mystery Bridge ARARs Evaluation
Page: 14 of 15
ARAA CITATION. AEQUIAJ:MENT EVALUATION
Wyoming Water Quality Rules Design considerations lor land The remedial action will not use land application.
and Regulations, Chapter XI, application lacllities. .. Regulation Is neither applicable nor relevant or appropriate.
Pan E, Sections 50 (b)
and (d) and 53. --
Wyoming Water Quality Rules DesIgn requirements lor pump stations lor No domestic or municipal wastewater involved. Regulation
and Regulations, Chapter XI, domestic and municipal wastewater. Is neither applicable nor relevant and appropriate.
Part B, Section 100b) (ii).
Wyoming Air Quality Standards Restrictions on the open burning No open burning 01 wastes involved. Regulation Is neither
and Regulations. Section 13. of wastes. applicable nor relevant and appropriate.
Wyoming Air Quality Standards Restrictions on visible emissions Visible emissions would not be generated by groundwater
and Regulations. Section 14. Irom new sources. technologies. Regulation Is neither applicable nor relevant.
Wyoming Air Quality Standards Prohibits the use of methods or devices which Regulation potentially applicable or relevant and appropriale.
and Regulations. Section 18. would conceal or dilute an emission from a source.
Wyoming Air Quality Standards Emissions excursions due to unusual operating Regulation potentially applicable or relevant and appropriate.
and Regulations. Section 19. conditions shall not be a violation 01 the regulations. ----
Wyoming Air Quality Standards Permliling requirements lor new Substantive requirements potentially applicable or relevant
and Regulations, Section 21. soUrces of air emissions. and appropriate lor alternatives utilizing technologies
which would resuU in air emissions.
-
Wyoming Solid Waste Management Requirements lor solid waste disposal Proposed remedial technologies do not include the
Rules, Sections 8.a(1),(2),(4) sites and hazardous waste disposal sites. development 01 a solid or hazardous waste disposal site.
and (5), 10.a(15), l1.a(4), Regulation neither applicabte nor revelant and appropriate.
l1.c(1), and l1.d(I). -- -------..-
Wyoming Environmentat Quatity Prohibits discharge 01 wastes to state Regulation neither applicable nor revel ant and appropriate -
Act. Wyoming Statue waters without a permit. deler to NPOES requirements.
35-11-301(a). ---.. -~_.---. - ---- -
-------
Exhibit 1 - Mystery Bridge AAAAs Evaluation
Page: 15 of 15
. .
AAAR CITATION REQUIREMENT EVALUATION
Wyoming Environmental Quality Provides State with authority to enter Regulation neither applicable nor revelant and appropriate -
Act, Wyoming Statue and Inspect property at which air, water, no substantive requirements.
35-11-1 09a(vi). or land pollution source Is located.
Wyoming Environmental Qualily General policy and purpose of Wyoming Regulation provides no substantive requirements. Regulation is
Act. Wyoming Statue environmental Quality Act. neither applicable nor relevant and appropriate.
35-11-102.
, ,
-------
Exhibit 2: Selec...d Remedy ARAHs
.ige 1 of 4
ARAR CITATION REQUIREMENT EVALUATION
A. Location Soocific ARARS
40 CFR 6.302 Action to preserve and protect wetlands, Action likely in lIoodplain 01 North Platte River; other items
lloodplalns, Important larmlands, coastal not applicable. Regulation is applicable.
zones. wild and scenic rivers, lish and
wildlife, and endangered species.
40 CFR 264.18 Location standards 'or treatment, storage, II temporary storage tanks 01 recovered hydrocarbons are used,
and disposal 'acilities. regulation may be applicable.
B. Chemical Soecific ARARS
40CFR 141.11 National Revised Primary Drinking Water Relevanl and Appropriate: ground water concentralions must not
Regulations: maximum contaminant exceed maximum contaminant levels. MCLs have been identified lor
levels 'or organic chemicals. 1,1,1-trichloroethane. trichloroethene, and benzene.
Proposed MCLs are to be considered.
40 CFR 143.3 National Secondary Drinking Water Non-en'orceable, non health-based concentrations lor drinking
Regulations: secondary maximum contaminant water. Regulation, although not enlorceable, should be considered.
levels.
40 CFR 141.50 Maximum Contaminant Level Goals: drinking water Non-enlorceable health goals lor public water systems.
quality goals set at levels 0' known or anticipated Regulation is relevant or appropriate lor constituents 01
health eUects. with a margin of salety. concern with an MCLG greater than zero.
Clean Water Act Section 304. Ambient Water Quality Criteria for Applicable or Relevant and Appropriate: concentrations
Protection of Aquatic Lile and In any sur'ace water must not exceed water quality criteria
Human Health. as a result 01 receiving ground water.
40 CFR 50.5 National Secondary Ambient Air Quality At present it is not expected that sulfur oxides will be produced
Standards for Sulfur Oxides. in the treatment process. tn the unlikely event that
they are, regulation would be applicable.
40 CFR 50.6 National Primary and Secondary Ambient At present it is not expected that particulates will be produced
Air Quality Standards lor Particulates. In the treatment process. tn the unlikely event that
they are, regulation would be applicable.
40 CFR 61 National Emission Standards lor Hazardous Regulations lor benzene emissions are applicable
Air Pollutants. lor air stripper trealment system.
--------.. ---- - --- - - --
-------
Exhibit 2: Selected Remedy ARARs
Page 2 of 4
--
ARAR CITATION REQUIREMENT EV ALUA TION
40 CFR 50.8 National Primary Ambient Air Quality At present it Is not expected that carbon monoxide will be
Standards for Carbon Monoxide. produced in the treatment process. In the unlikely event that
.. It is, regulation would be applicable.
Wyoming Air Quality Rules AIr quality standards lor particulates. At present it Is not expected that particulates will be produced
and Regulations, Secllon 3 in the treatment process. In the unlikely event that
(except for (aXiII) ). they are, regulation would be applicable.
Wyoming Air Quality Rules AIr quality standards for sulfur oxides. At present ills not expected that sulfur oxides will be produced
and Regulations, Section 3 in the treatment process. In the unlikely event that
(except for (a)(lII) ). they are, regulation would be applicable.
Wyoming Air Quality Rul~ Air quality standards for sulfuric acid At present It Is not expected that sulfuric acid mists will be
and Regulallons, section 6. mist. produced In the treatment process. In the unlikely event that
they are, regulation would be applicable.
Wyoming Air Quality Rules Air quality standards for hydrogen sulfide. At present ills not expected that hydrogen sulfide will be
and Regulations, Section 1. produced In the treatment process. In the unlikely event that
ills, regulation would be applicable.
Wyoming Air Quality Rules AIr quality standards for photochemlcals. At present Ills not expected that photochemicals will be
and Regulations, Section 8. produced In the treatment process. In the unlikely event that
they are, regulation would be applicable.
Wyoming Air Quality Rules . AIr quality standards for nitrogen oxides. At present ills not expected that nitrogen oxides will be
and Regulations, Section 10 produced in the treatment process. In the unlikely event that
(except for a). they are, regulation would be applicable.
Wyoming Air Quality Rules AIr quality standards for fluorides. At present it Is not expected that fluorides will be
and Regulations, Section 11. produced in the treatment process. In the unlikely event that
they are, regulation would be applicable.
Wyoming Air Quality Rules Air quality standards for carbon monoxide. At present it Is not expected that carbon monoxide will be
and Regulations, Section 12. produced in the treatment process. In the unlikely event that
it is, regulation would be applicable.
-
Wyorr ir Quality Rules Air quality standards lor particulate emi> 5. At present it is not expected that particulate emissions will '
and h-llulations. Section 14. produced in the treatment process. In the unlikely eventll.
they are, regulation would be applicable. - ---- .-- - -
.
-------
c
c
exhibit 0:::: Selected Remeoy ARAHS
t'dye 3 01 4
ARAR CITATION REQUIREMENT EV ALUA TION
Wyoming Air Quality Rules Air quality standards lor odors. At present it is not expected that odors will be
and Regulations, Section 16. produced in the treatment process. In Ihe unlikely event thaI
they are, regulation would be applicable.
C. Action Specific ARARs
40 CFR 147 Wyoming underground injection control Regulation is applicable lor
programs. injection 01 treated ground waler back inlo aQuiler. -.-
40 CFR 264.190 - 198 Requirements lor lacilities that use tank systems II remedy includes the use ollanks 10 Slore or manage
lor storing or treating hazardous waste. RCRA wastes, regulation is applicable.
40CFR 264.190 Applicability. II remedy includes the use 01 tanks to store or manage
RCRA wastes, regulation is applicable.
40 CFR 264.191 Assessment 01 existing tank system's II remedy includes the use of tanks to store or manage
Integrity. RCRA wastes, regulation Is applicable.
40 CFR 264.192 DesIgn and Installation 01 new tank II remedy Includes the use of tanks to store or manage
systems or combonents. RCRA wastes, regulation is applicable.
40 CFR 264.193 Containment and detection 01 reteases. II remedy includes the use of tanks to store or manage
RCRA wastes, regulation is applicable.
40 CFR 264.194 General operating requirements. II remedy Includes the use 01 tanks to store or manage
RCRA wastes, regulation Is applicable. -
40 CFR 264.195 Inspections. II remedy Includes the use of tanks to slore or manage
RCRA wastes, regulation is applicable.
40 CFR 264.196 Response to leaks or spills and II remedy includes the use of tanks 10 slore or manage
disposition of leaking or unlit RCRA wastes, regulation is applicable.
tank systems. ..
40 CFR 264.197 Closure and post-closure care. II remedy Includes the use ollanks 10 slore or manage
RCRA wasles, regulalion is applicable. -. -.- --- - _.-
40 CFR 264.198 Special requirements lor ignilable II remedy includes Ihe use 01 tanks 10 slore or manage
or reactive wasle. RCRA wastes. regulation is applicablo.
-. ..
-------
Exhibit 2: Selected Remedy ARARs
Page 4 0' 4
ARAR CITATION --
REQUIREMENT EVALUATION
40 CFR 268 land disposal restrictions. land disposal restrictions are not applicable to these activities.
Instead 01 lOR, RCRA section 3020 applies to reinjection 01 treated
ground water into Class IV injection wells during CERCLA response
.. actions. Moreover, lor CERClA response action where, as here. the
goal Is to clean up ground water to drinking water levels. the
Agency believes that health-based drinking water standards
(e.g., MCls), rather than lORs, will generally be the
relevant and appropriate clean up slandard.
Wyoming Water Quality Rules Data requirements lor permit applications lor the Remedy Incorporates treatmenl and disposal 01 ground waters
and Regulations, construction 0' treatment works, disposal systems, exceeding MCLs. Regulation is applicable.
Chapter III, Section 15. and other potential sources 01 pollution.
Wyoming Water Quality Rules Permit requirements lor construction, Substantive requirement 01 BACT analysis are applicable.
and Regulations. Chapter IX. modification, and operation (BACT).
Wyoming Air Quality Standards Prohibits the use 01 methods or devices which would Regulation potentially applicable or relevant and appropriate.
and Regulations, Section 18. conceal or dilute an emission Irom a source.
Wyoming Air Quality Standards Emlsslons'excurslons due to unusual operating Regulation potentially applicable or relevant and appropriate.
and Regulations, Section 19. conditions shall not be a violation 01 the regulation.
Wyoming Air Quality Standards Permitting requirements lor new Substantive requlremenls polentially applicable or relevanl
and Regulations, Section 21. sources 01 air emissions. and appropriate lor alternatives utilizing technologies
which would result in air emissions.
-------
mbl'esp6
RESPONSIVENESS SUMMARY
MYSTERY BRIDGE ROAD/U.S. HIGHWAY 20 SUPERFUND SITE
OPERA~LE UNIT 1 - GROUND WATER
INTRODUCTION
u
This responsiveness summary is organized into four sections:
I. Background of Community Involvement
II. Community Concerns
III. State Concerns
IV. PRP Concerns.
I. BACKGROUND OF COMMUNITY INVOLVEMENT
Community interest in problems at the site became very intense in late 1986 when site
contamination problems first surfaced and the ATSDR advisory was issued. Early public
meetings, many of which were attended by as many as 100 people, often became highly
emotional encounters between concerned residents and public officials. Media coverage
was extensive, including coverage by local and State newspapers and TV stations as well
as some national television coverage.
State legislators and Congressional staff members took a great interest in site activities.
The community's letter-writing campaign extended to the White House.
The community was divided early over appropriate means of obtaining information and
having input to decisions being made about site activities. Three groups formed, each with
its own interest, making communication difficult. One group clearly was interested in
having the government buy their properties and move them out of the area. Another group
was a board established during the early phase of the Brookhurst Subdivision's growth to
serve as a legal entity for Brookhurst residents in improvement projects. A third group was
made up of residents of the Mystery Bridge Subdivision who asked that they be recognized
separately from either group in Brookhurst.
Initial community involvement was coordinated by an EPA removal program community
relations coordinator, as well as by a field liaison from EPA's Office of External Affairs, EPA's
Wyoming office representative and EPA's On-5cene Coordinator for the site. Early activities
included meetings with citizen groups and interested parties and a public meeting held at
the Evansville School on December 5. 1986. On that date, EPA also issued a fact sheet
describing EPA's role in site work and immediate plans for the site. Those plans included
providing botUed water to site residents until a permanent supply could be provided. EPA
began installing bottled water dispensers on December 15. Most residents signed up by
January.
EPA's removal community relations coordinator prepared a Community Relations Plan in
December 1986. The plan included activities designed to disseminate information, identify
key concerns 01 residents and other interested parties, keep public officials informed and
develop an overall communication. network for the site.
On January 14, 1987, EPA held a second public meeting at the Evansville School and
released a second Fact Sheet. Topics at the meeting included EPA's installation of a
monitoring well system, plans for a permanent water supply favoring an Evansville hook-up,
and a discussion of air monitoring work, including work to be performed by the Wyoming
Department of Environmental Quality (WDEQ) and limited indoor monitoring to be
1
-------
mbresp6
conducted by EPA. The January 14, 1987 fact sheet and a subsequent January 20, 1987
fact sheet also focused on these aspects of site work. One community group at the
meeting demanded that a complete health assessment of the subdivision be performed by
EPA.
On February 14, 1987, at the request of one community group, Wyoming's new Governor, a
state Senator and the Director of the WDEO, visited an estimated 100 residents at the
subdivision to hear their concerns and reaffirm the State's commitment to them. Three
days later, on February 17, the Governor issued a press release identifying a schedule for
State investigations, including soil sampling, investigation of dumping sites, and
investigation of complaints lodged regarding industries contributing to the contamination.
Additionally, in response to citizen concerns, the Governor announced that a 1,000 gallon
tanker from the National Guard would arrive on February 17 and begin dispensing water to
site residents to be used for other domestic purposes, such as bathing and showering.
On February 27, 1987, EPA held a third public meeting and distributed the first EPA
information update (Update No.1). The update described EPA's authorities under the
remedial and removal programs, as the Agency began studies leading toward long-term
remediation of the site. The update also contained a discussion of recent and projected
community involvement activities. These included a three-day visit by an EPA
representative to meet with concerned citizens. EPA also announced that a community
involvement representative would be made available atter March 2nd to meet with residents
and hear their concerns. Other activities included development of an initial mailing list of
residents and concerned individuals for use in disseminating site information. The update
identified a toll-free number for community members to contact EPA directly with questions
or concerns.
An estimate 150 people attended the February 27th public meeting. EPA presented a
progress report on actions related to groundwater monitoring and plume delineation as well
as evaluation of a permanent public water supply system. EPA and WDEO staff discussed
soil sampling, surface and tap water sampling, ambient air monitoring, indoor air
monitoring, a source inventory and an area waste disposal inventory. EPA explained the
hazard ranking system (HAS) and how it is used in determining NPL listing. A public health
advisor from A TSDA answered questions about possible health effects of the
contamination. Some residents vehemently voiced their concerns about health risks.
By the week 01 March 2nd, two community liaisons had been posted in the area by EP A
and Wyoming's Governor. Both were temporarily situated in EPA's Wyoming field office in
Casper. During early March, the liaisons held meetings with community groups and
individual community residents and involved public officiaJs. Vital concerns expressed
during these meetings continued to relate to fears regarding the health and safety of
children and adults at the site and frustration over perceived government indifference.
Some residents continued to assert that relocation was the only solution acceptable to
them. AdditionaJ issues which were emerging included: concern regarding the safety of
showering with contaminated well water; concern over the safety 01 Evansville's drinking
water as a permanent alternate water supply due to elevated trihalomethanes (THM) levels
and traditional mistrust 01 Evansville's water quality; water resource concerns; concern
regarding the potentiaJ for "off gassing" (Le., the potentiaJ for upwardly migrating vapors
from contaminated groundwater to cause soil and air contamination); and concern whether
EPA would be able to ensure that surrounding industries would not recontaminate the area
in later years.
The liaisons initiated contact with local TV and press representatives on March 5th to
explain their role in the community involvement efforts and to notify the media of their
2
-------
mbrll8Q6
availability. A press briefing was held by representatives from EPA and the Governor's
office at the end of March which included representatives from local television stations (Ch.
2, 14 and 20) and newspapers (the Casper Star Tribune and Casper Journal). Due to
requests of press members in attendance, briefings were provided on the scope of the ESI
work plan, the HRS process, and its relationship to NPL listing.
Other community involvement activities in March 1987 included distribution of Update NO.2
and a THM fact sheet, and establishment of two information centers, one located at the
Evansville School Ubrary and one at EPA's Wyoming office. The work plan for the ESI,
which included the sampling plan for ESI work, was also released for public comment from
March 6 - 20, 1987. Copies of the report were made available for review at the two
information centers. Additional copies were provided to the three organized community
groups for distribution to their members and other interested residents. On March 26,
1987, EPA issued a press release announcing upcoming ESI activities to be conducted
under the direction of the EPA Remedial Project Manager. The Governor's office also
initiated activities in March to provide free counseling through the Central Wyoming
Counseling Center, in response to residents' concerns over mental stress created from
living at the site. Approximately seven subdivision families took advantage of this service.
April 1987 activities included an invitation for the public to review and submit comments on
EPA's evaluation of potential permanent water supply sources, as contained in the draft
version of the Permanent Water Succlv Source for the Brookhurst Subdivision. The public
comment period extended from April 3rd to April 17th.
On April 13, 1987, Governor Sullivan announced the formation of the Brookhurst
Environmental Task Force. The Task Force was composed of representatives from the
Brookhurst and Mystery Bridge subdivisions, EPA, WDEO, the Natrona County health and
planning departments. the Casper Board of Public Utilities. the Wyoming Community
Development Authority (WCOA), Natrona County legislators, and the Mayor of Evansville.
Three local residents, including members of the three community groups and a
representative-at-Iarge from the Mystery Bridge area. were members. The Task Force's
goal was to increase interagency communication and coordination to expedite resolution of
environmental problems at the site and to involve area residents in the process. Three
Task Force meetings were held in April focusing on such issues as providing available
WCOA housing to interested residents and possible replacement of the National Guard
water truck.
On April 15, EPA mailed its responsiveness document to commenters.on the draft ESt work
plan. The comments were also discussed at an April 16, 1987 public meeting held at the
Casper City Council Chambers. Other topics of discussion at that meeting included status
of WOEa investigation of 34 complaints regarding industries in the area, an overview of
EPA's water quaJlty program, presentation 01 public water supply options, the status of the
ESI, and the status of temporary housing activities. Speakers included EPA, WOEQ and
WCOA representatives. .
On May 4, 1987, EPA released sampling results from 28 monitoring wells sampled during
March. Well samples had been tested for 129 priority pollutants, including pesticides and
metals. EPA Update NO.3 was also prepared and.distributed in May. The update
addressed continued concern of residents over the safety of using contaminated well water
for irrigating gardens and watering livestock, and included a Fact Sheet clarifying A TSOR
and EPA's evaluation 01 heaJth effects from exposure to contaminated well water. The Task
Force held ~hree more meetings in May continuing to explore numerous issues, including
issues related to options for a permanent water supply system.
3
-------
mbresp6
Task Force meetings continued in June. In mid-June, the representative from one of the
Brookhurst groups resigned from the Task Force, citing concern that Brookhurst residents'
wishes had been ignored in the choice of Evansville as the supplier of a permanent water
supply system for the site and voicing her opinion that the Task Force was not worthwhile.
The final draft ESI report was released by EPA on June 30, 1987, with public comment
solicited from June 30-July 14. Copies of the report were distributed to the Brookhurst and
Mystery Bridge groups as well as placed in the two current information centers at EPA's
Wyoming office and the Evansville Town Hall. The Town Hall was selected instead of the
Evansville School library due to the limited summer hours in which the school was open to
the public.
On July 9, 1987, a public meeting was held at the Casper City Council Chambers for
citizens to discuss the ESI report with EPA and WDEa representatives. The meeting
included a heated exchange regarding the ESI report's findings that the site was "habitable"
and a buyout was unwarranted, as well as its recommendation that the site be hooked up
to the Evansville water supply with the water intake relocated above the Casper wastewater
treatment plant. As a result of concerns voiced at this meeting, the public comment period
for the ESI report was extended through July 21.
Also in July 1987, with identification of a permanent water supply and growing emphasis on
the installation of the permanent supply system, the Governor requested that the Task
Force begin to redefine its role and membership composition to reflect a new focus
directed at providing oversight and serving as a liaison between the Governor, the state,
county commissioners, EPA and site residents. Plans were made to disband the existing
Task Force by the end of July when finaJ approval of the ESI report was anticipated. The
Task Force was to be replaced with an oversight committee with a focus on overseeing the
timely implementation of the permanent water supply system.
On July 21 st, at the request of the Brookhurst Citizens Committee (BCC), members of the
BCC met in Denver, Colorado with EPA's RegionaJ Administrator. The residents' purpose
for the meeting was to voice their concerns regarding health effects and to stress their
conclusion that a buyout was the most protective and cost-effective solution for the site.
The meeting ended abruptly when the EPA RegionaJ Administrator reaffirmed EPA's
position that the subdivision was safe with the planned water supply and that residents
would not be relocated.
In August 1987, EPA released its responsiveness summary addressing comments obtained
from citizens on the finaJ draft ESI report. EPA Update No.4, also distributed during the
month, addressed concerns regarding the permanent water system, including fire
protection in connection with the new water system, user rates, potential water supply
concerns and concern by residents over industriaJ user hqokups.
The newly formed Governor's Oversight Committee held its first meeting on August 13 with
subsequent Governor's Oversight Committee meetings occurring on August 27th,
September 4th, and thereafter on a periodic basis. Membership included many members of
the originaJ Task Force and expanded resident representation to five. Residents chose
their own representatives for the Committee. The Governor's objectives for the committee
were identified at the August 13 meeting. These objectives included serving as a direct
liaison with the Governor's office and EPA; ensuring construction time-lines were
maintained; coordinating residents' inquiries; releasing updated information on the
progress of the water transmission line; overseeing the construction project; and serving as
a technical coordination body between the federal government, the State and Natrona
4
-------
mbres;16
County. EPA used this forum regularly to update site residents about site activities and to
discuss concerns raised at the meetings by resident representatives.
o
In October 1987, EPA distributed Update No.5. providing a status on the water supply
source decision and water line installation. EPA's Administrative Record for public use for
this action was placed in EPA's Wyoming office. Again. due to concerns regarding public
hours, the location of the second information center was switched from the Evansville Town
Hall to the Natrona County Ubrary in October. Because of space constraints at the library,
however, only the index of the Administrative Record and key technical documents were
housed there.
In December 1987, EPA Update NO.6 was distributed. It included a discussion of the two
Administrative Orders on Consent (consent orders) issued by EPA on December 15 to
three PRPs - KN Energy, Dow Chemical Company and Dowell Schlumberger. The focus of
the removal orders was to clean up suspected sources of groundwater contamination on
KN and Dow Chemical Company/Dow Schlumberger properties. Update NO.6 also
discussed a third consent order negotiated by EPA with the three parties requiring the
PAPs to conduct the AlfFS phase of Superfund activities at the site. The purpose ot the
RI/FS work was to investigate environmental damage and identify alternatives for cleaning
up site contamination. The RI/FS Administrative Order on Consent was submitted for public
comment from December 5. 1987 to January 29, 1988, the Agency designating a longer
comment period than usual due to the holidays.
On January 27, 1988, the Governor sent a memo to the Governor's Oversight Committee
addressing some members' feelings that the committee should disband. The- Governor
recommended instead that the committee remain in force until all members collectively
agreed its goat had been accomplished and suggested meetings should be scheduled only
when necessary. Governor's Oversight Committee meetings continued periodically
through the spring 01 1988 providing updates on the progress of the removal work and
exploring other site issues consistent with the committee's objectives.
EPA updates were prepared and distributed in March and May 1988. These updates
provided a status on the progress of removal work, RifFS work and RCRA work at the site.
On March 16, EPA released its responsiveness summary to public comments on the RI/FS
Administrative Order on Consent. A public comment period was held from April 14 - 27 on
the PAPs' draft AlfFS work plan.
On June 2, the status 01 Superfund and ACRA enforcement investigations and related
WDEa site investigations were discussed at a Governor's Oversight Committee meeting.
During the meeting, Governor's Oversight Committee members discussed the need for
streamlining and again redefining composition and goals of the committee to address a
different set of objectives reflective of the growing focus of site work on AlfFS activities.
In late May and early June 1988, the EPA Community Involvement Coordinator and
contractor personnel conducted meetings in Wyoming and Colorado with site residents,
public officials and representatives of the PAPs, to aid in updating EPA's community
relations plan for the site.
On June 22. EPA released its responsiveness summary to public comments on the draft
RifFS work plan. The final work plan was approved on July 13, 1988.
On August 24, the Governor announced that the Oversight Committee had indeed fulfilled
its mission with the virtual completion of the water line and indicated that EPA and WDEa
would continue some forum for discussing technical issues with community members
5
-------
mbresp6
throughout the RI/FS. On August 26, EPA and WOEa sent a special notice announcing tr
formation ot a new technical coordination group with two important objectives: (1)
informing and discussing site activities with the public, and (2) interagency coordination.
The newly formed Technical Coordination and Discussion Group (TH.D.) met on a regular
basis with members of the community to discuss technical progress at the site and to
ensure continued coordination among the various governmental entities involved. The last
of these meetings was held October 26, 1989.
The Governor's office provided for minutes of these meetings to be recorded. Meetings
minutes were regularly distributed to everyone on the site mailing list.
In November 1988, EPA issued the revised Community Relations Plan for the site providing
site background, community involvement history and a strategy for continuing to work with
community members and various governmental organizations to ensure involvement in the
decision-making process.
'1
EPA prepared and distributed additional information updates in August 1988, October 1988,
December 1988, April 1989, August 1989, and October 1989. These updates contained
information on the status of site activities and addressed concerns raised during periods
between updates. In addition, the Agency developed and distributed a fact sheet in
January 1990 which discussed the results of the site risk assessment.
The RI/FS for the site was completed in June 1990. In July 1990, the Proposed Plan was
mailed to everyone on the site mailing list and distributed to the Administrative Record at
the Natrona County Library. A public comment period was held from July 5 - August 3,
1990 on the Proposed Plan. A public meeting was held July 18, 1990 at Casper City
Council Chambers to discuss the Proposed Plan with the interested public. An ad
summarizing the Proposed Plan and announcing the public meeting was placed in the
Casper Star Tribune July 1, 1990.
EPA received three sets of written comments during the public comment period. Two of
these were from lawyers representing PRPs at the site; one was from a technical expert
hired by attorneys representing approximately 268 parties (84 or 85 families) in connection
with claims arising from contamination of the Brookhurst and Mystery Bridge subdivisions.
Two oral comments were received at the public meeting. Comments are summarized
below, along with EPA's responses.
II. COMMUNITY CONCERNS
A summary 01 verbal comments made during the July 18, 1990 Mystery Bridge public
meeting, and EPA's responses to those comments follow:
Comment #1: One resident commented that her residential well was contaminated with
BETX, but EPA's maps included in the proposed plan indicated that the well is within the
VHO plume. and not within the BEl'X plume.
EPA Response #1: During the public meeting, the Remedial Project Manager stated that
he could not respond directly to the comment, but would investigate and respond in writing.
On September 21, 1990, the response was sent to the commenter; a copy of the letter is
included as Exhibit 1 to this summary. EPA's response stated that, based on the analytical
results from samples taken from monitoring wells several times from 1981 through 1990,
EPA believes there is no correlation between the BETX plume from KN or the plume
emanating from the LARCO facility and any BETX in her well.
6
-------
mcresp6
Comment #2: The same resident asked if the proposed remedy would eliminate the non-
VHO chemicals from her well water.
EPA Response #2: EPA believes that if the proposed remedy performs as expected.
contaminants from DOW/DSI and KN, including non-VHO contaminants, in the ground
water throughout the site will be reduced to levels that are in compliance with the federal
and state regulations and the health risks from ingestion of the ground water contaminated
from these sources will be reduced to acceptable levels.
u
Comment #3: The same resident requested that she receive a copy of the RI/FS report for
review.
EPA Response #3: The commenter was told at the public meeting that the RI/FS and all
the other reports are available for public review at the three locations listed in the Proposed
Plan. EPA sent a copy of the RI/FS report to the commenter. In addition, this particular
commenter has been receiving technical documents leading to the RI/FS for the past two
years because she has been on EPA's technical document mailing list.
Comment #4: One attendee at the public meeting asked how many years the EPA would
be monitoring the ground water to make sure that the remedy is effective.
EPA Response #4: The Remedial Project Manager answered the question in two parts.
During the remedial action phase, EPA will monitor to evaluate the behavior of the ground
water system and the removal of the contamination. After the ground water has been
cleaned up to acceptable levels, and if contamination is left on site, EPA would continue to .
monitor at least every five years until the potential for contamination of the ground water is
eliminated. The second operable unit (OU 2) for the site will address contaminant source
areas, particularly those soils on and immediately adjacent to the industrial areas.
EPA received one letter providing comments from the community during the public
comment period. The letter came from Dr. Patrick Sullivan. A copy of this letter is
appended to this summary as Exhibit 2. Dr. Sullivan is an independent environmental
consultant hired by the law firm of Spence, Moriarity and Schuster in Cheyenne, Wyoming.
This law firm represents approximately 268 parties (84 or 85 families) in connection with
claims arising from contamination 01 the Brookhurst Subdivision.
The comments are grouped under a topic heading. Each specific comment made by Dr.
Sullivan is first quoted, and then the EPA response is provided.
TOPIC: Characterization of the Alluvial Aquifer-Aquifer Homogeneity.
Comment #5: The RI/FS assumes that the alluvial aqui1er is composed of homogeneous
porous media that is a "poorly sorted clay to sandy clay with a coefficient of permeability
ranging from 3.9 x 1 (}'3 to 5.6 x 10"5 em/see" that was determined from five samples (page
28).
EPA Response #5: The statement cited refers to laboratory permeability tests conducted
on undisturbed samples 01 "the upper fine grained layer" collected during monitoring well
installation. These are samples 01 the surficial soil layer at the site, which generally lies
above the local potentiometric surface and above the saturated aquifer zone. Thus, while
these data are relevant to the possible transport and/or retention of contaminants spilled at
the surface, they are not relevant to the question 01 ground water flow and contaminant
transport through the saturated alluvial aquifer.
7
-------
mbresp6
Comment #6: "The horizontal component 01 flow in the alluvial aquifer is consistently to the
northeast with only minor and local variations. (page 29)",
EPA Response #6: Based on the ground water elevation maps given on Figures 19A. 198,
19C, 190, 19E, 19F, 19G, 19H, 191, and 19J 01 the RifFS report, the statement cited is an
accurate portrayal 01 available data and site conditions. There appears to be no reason to
question, qualify, or modify the cited statement.
Comment #7: "There were only eight wells (Le" opportunities to characterize the alluvium
in the subdivision) installed in the Brookhurst area. No detailed split-spoon sampling (or
boring logs) were correlated or compared to determine alluvial soil texture variations".
EPA Response #7: OBG installed 11 monitoring wells on and adjacent to the site (Well
IDs: OBG-2, -3, -4, -5, -6, -7, -8, -9, -11, -12, and -13). 01 these, 6 were located within the
Brookhurst Subdivision (see RifFS Figure 11). All 11 wells were drilled to bedrock, and
detailed boring logs developed from split-spoon samples are provided in Appendix 0 of the
RifFS report. The 1987 Expanded Site Investigation (ESI) includes comparable boring logs
from 28 wells installed on behal1 01 EPA, including 10 located within the subdivision (RifFS
Figure 11). Consequently, detailed split-spoon sampling and boring logs are available for a
total 01 39 wells, 16 01 which are located within the Brookhurst Subdivision,
Comment #8: "No resistivity studies (or borings) were completed to determine the
potential presence 01 old river chan~els ..."
EPA Response #8: As noted above, data are available 1rom 39 borings completed to
bedrock in the area. In the RI/FS report, Figure 12 provides a map 01 the bedrock surface
inferred 1rom the boring data. A distinct channel in the bedrock surface is noted on the
figure, and discussed on page 18 01 the RI/FS report. In general, the axis 01 this channel
coincides with the general northeasterly direction 01 ground water flow in the study area.
Comment #9: "Aerial photos 01 the subdivision in 1962 clearly show that the initial segment
01 Elkhorn Creek is man-made and the current contamination that exists at this site follows
this man-made channel. How is this 1actor incorporated into the modeling 01 the alluvial
aqui1er?",
EPA Response #9: It is apparent from other maps 01 the area and 1rom site surveillance
that the channel 01 Elkhorn Creek has been artificially altered through the industrial
properties south 01 the subdivision. However, it is not believed that channelization 01
Elkhorn Creek is a significant 1actor in the transport of contaminants through the underlying
ground water aquifer.
The creek channel is only a few 1eet deep, whereas the ground water surface in the
alluvium is about 30 feet deep. Thus, although the creek does appear to be losing flow as
it traverses the site, it does not appear to be in direct hydraulic communication with the
underlying ground water. The flow lost by the creek probably recharges the ground water
by percolation through 20 1eet or more of unsaturated alluvium. This recharge in turn is
generally distributed over a considerable length 01 the creek, not concentrated in the
industrial areas. Contaminated ground water is observed directly beneath the industrial
properties, and in places upgradient from the creek bed. It is thus unlikely that the creek
channel serves to direct the flow 01 contaminants on the surface or in the subsurface.
Furthermore, the contaminant plumes, although well-defined, are not defined in such detail
that they can be directly correlated with the right-angle bends observed in the channelized
creek bed.
8
-------
mbresp6
To the extent that the direction of contaminant plume movement can be correlated with
either the natural or artificial dire<;tion of stream flow in Elkhorn Creek, it is probably
because both the ground water and surface water gradients are generally to the northeast,
towards the North Platte River. This general direction of ground water flow has been
incorporated into modeling of the alluvial aquifer, but there appears to be no reason to
incorporate the specific effects of recharge from Elkhorn Creek into the modeling.
Comment #10: "The VHO plume models in the 1987 Site investigation show trends toward
the west side hydrocarbon plume direction.
"
EPA Resconse #10: The trends noted are believed to be largely artifacts of the data
contouring. Subsequent data plots do not clearly show such trends (see RifFS report
Figures 50A, 508,500, 52A, 52C, and 52E).
Comment #11: "The geologic data provided in the RifFS do not support an interpretation
of a relative uniform alluvial aquifer. It is strongly recommended that a more detailed
characterization of the alluvial aquifer be completed ..."
EPA Resconse #11: EPA believes that substantial data have been collected on the nature
of the alluvial aquifer at the site, and that the data overwhelmingly support a conclusion that
the aquifer is in fact relatively homogeneous in its makeup and hydrologic properties,
although it is recognized that the aquifer is of variable thickness because of its presence
within a channel in the bedrock surface.
A review of the well log data provided in the ESI and Appendix 0 of the RifFS report
indicates that the predominant material detected below the~evel of first water occurrence is
a tan, fine to coarse sand with some gravel, with a Uniform Soil Classification of SW (well-
graded sand or gravelly sand with little or no fines). Approximately 84% of the total alluvium
penetrated below the water table in 35 borings is classified as SW. In 15 of 35 borings, the
entire alluvial interval penetrated is SW, while in only 2 of 35 borings does SW constitute
less than half of the interval penetrated (in those two wells, the predominant material
encountered below the water table is gravel, GP or GW). 8ased on gradation analyses of
11 samples collected during monitoring well installation, the proportion of sand varied from
46% lo 90%, with the proportion of sand exceeding 75% in 10 of the 11 samples.
TOPIC: Modeling Analysis
Comment #12: "The discussion of the sensitivity analysis pertaining to the predictions of
contaminant transport modeling (beginning on page 1 07) of VHO plume is only theory.
What actual laboratory or field tests were performed to verify the selected conditions? ..."
EPA Resconse #12: The sources 01 data used in the sensitivity analyses are noted in the
RifFS on Table 10. Hydraulic conductivity, hydraulic gradient, porosity, and saturated
thickness were based on field measurements at the site. Longitudinal and transverse
dispersion coefficients were based on values reported in the literature for materials of
similar composition to those observed during sampling of site borings. Retardation
coefficients were based on published values of organic-carbon partition coefficients for
contaminants of interest, plus estimates of soil organic carbon content, porosity, and bulk
density based on values reported in the literature for materials of similar composition to
those observed during sampling of site borings. In general, EPA believes that the data
used in the sensitivity analyses are reasonably representative of site conditions.
9
-------
mbresp6
Comment #13: "...The predictions and sensitivity analysis pertaining to the Brookhurst site
would be more believable if the EPA could provide one or more examples of how modeling
and the subsequent sensitivity analysis have actually periormed in predicting remediation
effectiveness for other sites..."
EPA Response #13: The sensitivity analyses were conducted in order to determine the
sensitivity of model predictions to uncertainty in the model input parameters. Thus, the
different input parameters were varied across their possible ranges of values as determined
from site-specific data or published data, and predictions made of contaminant plume
configurations. In this manner, it was possible to determine which input parameters were
more important in affecting predicted plume configuration. In addition, by comparing
predicted plume configurations with the observed configuration based on field data, it was
possible to "calibrate" the model by selecting a set of input parameters which resulted in a
predicted plume configuration most nearly consistent with the observed configuration.
Thus, it is not necessary to demonstrate that the model reasonably predicts contaminant
migration at other Superiund sites, as suggested by the commenter, since the model
reasonably predicts past contaminant migration at this site. .
o
TOPIC: Bedrock Surface
Comment #14: "The limited number of wells completed in the Brookhurst area does not
provide many data points to determine a reasonable representation of the bedrock suriace
contours."
EPA Response #14: EPA believes that sufficient data are available to adequately represent.
bedrock surface contours. As noted above, data are available from 39 borings completed
to bedrock in the area. Figure 12 of the RI/FS report provides a map of the bedrock suriacE'
inferred from the boring data. A distinct channel in the bedrock suriace is noted on the
figure, and discussed on page 18 of the RI/FS report. In general, the axis of this channel
coincides with the general northeasterly direction of ground water flow in the study area.
Figure 12 also shows the elevation of the top of bedrock at most of the wells in the study
area, so that bedrock contour maps with a contour interval less than ten feet could be
constru~ed if necessary
TOPIC: Trace Element Distributions and Cleanup
Comment #15: "EPA monitoring wells 1-3, 1-8, 1-9, 1-10, 2-11, and 2-14 that occur within
or adjacent to the KN Energy BETX plume all either exceed chromium and/or lead MCL's.
What is the extent of the distribution of these trace elements with this plume?...Are lead and
chromium not a hazard'r
EPA ResDonse #15: The reported concentrations of lead and chromium in unfiltered
ground water samples exceeded MCLs at several wells. Twenty-five of forty samples
exceeded the MCl for chromium, with the maximum value about 3 times the MCl. Fifteen
of forty samples exceeded the MCl for lead, with the maximum value about 2.5 times the
MCL For chromium, the mean concentrations were approximately the same for wells
upgradient of the industrial sites, on the industrial sites, and immediately downgradient of
the sites (about 65 ug/L). For lead, the mean concentration for wells immediately
downgradient from the industrial sites was about twice that for wells upgradient of or on the
industrial sites. Most of the elevated lead values were from wells far to the east of the 8ETX
plume from the KN property, and cannot be readily correlated with the plume.
It should be noted, however, that the elevated metals concentrations discussed above were
for values from unfiltered ground water samples. Dissolved concentrations of metals in
10
-------
mcrllSpO
ground water are generally determined from filtered samples so as to avoid bias from
suspended particles in the water collected from a monitoring well. Only one filtered sample
exceeded a primary MCL (234 ug/L silver in well EPA 1-12). Furthermore, none of the
ground water samples reported in the ESI exceeded MCLs for any trace metals. Thus,
there is not believed to be a significant health threat from trace metals in ground water in
the study area.
TOPIC: Southeast Soil Gas Analysis
o
Comment #16: "...the GC air analyzer having a photoionizable (PIC) detector will not detect
compounds such as methylene chloride and acetone. In order to detect these compounds
a FIC detector would be required. Because a GC with a PIC detector was used, a potential
plume containing methylene chloride and acetone that is indicated in residential well waters
was not investigated. This IS suggested for the following reasons:
(,
a)
NATCO is a potential source of methylene chloride and acetone based on
use of paint thinners, painting and stripping.
Numerous residential tap water analysis in the area adjacent to NATCO
showed elevated levels (an order of magnitude) of methylene chloride and
acetone compared to other Brookhurst samples...
b)
d)
...many potential compounds from the southwest area may not have been
detected.
As a result, no EPA monitoring wells were installed within the southwestern portion of the
subdivision. .."
EPA Response #16: It is believed that the commenter is actually referring to the
southeastern part of the subdivision, since this is the area adjacent to the NATCO facility.
The thrust of the commenter's statements are based on the results of ground water
analyses from the ESI. Upon reviewing the data, EPA believes that neither acetone nor
methylene chloride are of concern for the following reasons:
.
Acetone - acetone levels of the order of 10.ug/L were reported in 11 of about
60 domestic tap water samples in 1987. Only one of the samples was from
the vicinity of the NA TCO facility; eight of the samples were from the
northeastern part of the subdivision, adjacent to the river, and the other two
were from the west-central part of the subdivision. Several values of about
20 ug/L were reported in wells in the southeastern part of the subdivision,
although acetone was also detected in associated laboratory blanks and.
was detected at comparable levels in a contemporaneous field blank.
Acetone was reported in 1987 from only three monitoring wells in the
industrial area, and from none of the monitoring wells in the Subdivision.
Curing subsequent sampling, acetone was reported only from three wells
near the northern KN property line, although all three values are unreliable
because acetone was also detected in the associated blank samples,
suggesting laboratory contamination or presence of acetone in the sampling
containers.
.
Methvlene chloride - methylene chloride was reported in several domestic
tap water samples in 1987. In the area north 01 Rawhide Road, between
Buckskin Road and Elkhom Creek, methylene chloride was reported in four
11
-------
mbresp6
wells at levels of 76 to 668 ug/L; in a fifth well in this area, methylene chlorid
was reported at only 4 ug/L All of these values are unreliable because
methylene chloride was also detected in the associated blank samples,
suggesting laboratory contamination or presence of methylene chloride in
the sampling containers.
In the southeastern part of the Subdivision, near the NATCO facility,
methylene chloride was reported in six domestic well samples at levels
comparable to those seen in a field blank. Methylene chloride was also
reported in the associated laboratory blanks.
o
In subsequent sampling of monitoring wells, methylene chloride was
reported .in February 1988 at about 20 ug/L in four wells in the industrial area
and five wells downgradient of the industrial area. Methylene chloride was
also reported in February 1988 at 480 to 910 ug/L at three wells along the
northern property line of KN. All of these values are unreliable because
methylene chloride was also detected in the associated blank samples,
suggesting laboratory contamination or presence of methylene chloride in
the sampling containers. In addition, all of the wells where methylene
chloride was reported are interspersed among several more wells where
methylene chloride was not detected, so there is no definite pattern of
methylene chloride presence in the ground water.
Despite the fact that neither acetone nor methylene chloride has been unambiguously or
continuously reported in ground water samples from the area, these parameters will
continue to be monitored during remedial activities to assure that they pose no health risk.
TOPIC: Modeling and Homogeneous Aquifer
Comment #17: "The model in this RI/FS used hydraulic conductivity values based on the
Horslov (sic) method ... One should be careful in using Harslov (sic) method values for the
following reasons:
a)
The Horslov (sic) method gives only an order of magnitude estimate for
hydraulic conductivity...
There were not enough data collected for a proper Horslov (sic) analysis..."
b)
EPA Resconse #17: The data collected during the slug tests were limited because of the
rapid recovery of water levels in the wells due to the relatively high hydraulic conductivity of
the alluviaJ aquifer material. Given the limited data available for analysis, the Horslev .
analysis may be most appropriate because it is the simplest, most direct method of slug
test analysis. Furthermore, the relatively high degree of consistency among calculated
values of hydraulic conductivity based on different methods (slug tests, pumping tests, and
grain size analysis. see Appendix H) indicates that the hydraulic conductivity of the aquifer
has been adequately characterized.
Comment #18: "Contaminant plume shapes clearly indicates the heterogeneities in the
aquifer. The values used for m'odel sensitivity analysis (Table 10) and the basis for these
values, clearly show the heterogeneous nature of the aquifer".
EPA Resconse #18: It is recognized that the various aquifer tests suggest a degree of
inhomogeneity. Calculated values of hydraulic conductivity based on the field tests range
over more than an order of magnitude. However, data from nine of fourteen wells which
12
-------
mDr~
were tested range from 1.1 to 6.0 x 10-2 em/see and vary by only a factor of about five from
minimum to maximum. Only one well exhibited a value less than 1 x 10-2 em/see, and only
four exhibited values greater than 1 x 10-' em/sec. As noted below, this degree of
heterogeneity in aquifer properties has been incorporated into the modeling predictions.
Comment #19: 'While 'porosity range for these tests was 24 to 34%...' (page 28),
sensitivity analysis uses 35 to 45% porosity..."
EPA Resoonse #19: The commenter's observation is correct that some site data suggest a
possibly lower range of porosity than that used in the modeling effort. On the other hand,
the model sensitivity analyses indicated that porosity was a much less significant parameter
than the Darcy velocity which is controlled by the hydraulic conductivity and gradient
observed in the aquifer. Furthermore, the model calibration (as discussed above) indicated
that the default value of porosity used in the model resulted in a predicted plume
configuration which reasonably matched the observed plume configuration. Consequently.
EPA does not believe that the inadvertent omission of lower porosity values in the modeling
effort significantly affects the model predictions or the ultimate selection of remedy.
Comment #20: "...a description of the model is not provided, which makes it difficult to
evaluate how the model is calibrated/validated...if the model is based on the analytical
solution, then heterogeneities cannot be incorporated in the model".
EPA Resoonse #20: The uncertainties in some aquifer properties noted above have been
incorporated into the predictive modeling of contaminant transport through the stochastic
features of the model employed. As noted on pages 107 and 108 of the RI/FS report, the
contaminant transport model was based on "...an analytical solution for a two-dimensional
contaminant plume in a uniform ground water flow field." Although it is true, as noted by
the commenter, that an analytical model cannot directly incorporate aquifer heterogeneities,
the application of the model in the present case implicitly incorporates such heterogeneities
through its stochastic features. That is, as described on page 108, values of each input
parameter are randomly chosen from their ranges of possible values and a value of
contaminant concentration at a point and time of interest is calculated. The random
selection of input parameters and calculation of contaminant concentrations is repeated
thousands of times so as to develop a probability distribution of predicted contaminant
concentrations. The most probable resulting value is thus one which does incorporate the
uncertainty involved in representing the actual aquifer as a uniform, homogeneous aquifer.
TOPIC: Free Product Plume from LARCO
Comment #21: -EPA 2-4 well is located inside the free product plume from LARCO.
However, ground water sample from this well shows Toluene, Xylenes, and Ethyl Benzene
below detectable limits. These components are commonly found in gasoline and refinery
products. Absence of these product in the ground water sample at EP A 2-4 well is a clear
indication 01 sensitivity 01 dissolved hydrocarbons on the vertical location where sample
was taken.
Hydrology literature is full of examples where dissolved product plume extends much
further than the free product plume. Remediation efforts should take that into account.
Also, adsorbed and trapped hydrocarbons in the vadose zone (unsaturated region) will
continue to act as source of contamination for the ground water. Trapped hydrocarbons
can exist even inside the water table due to seasonal water level fluctuations.
How does the LARCO result influence EPA's understanding of the BETX plume that is
considered for remediation?..."
13
-------
mbresp6
EPA Resconse #21: The LARCa facility is under the jurisdiction of the Resource
Conservation and Recovery Act (RCRA) and contamination emanating from the LARCa
property (referred to as the RCRA plume) is being addressed under RCRA authority. Well
EPA 2-4 is generally indicated as being on the fringe of the RCRA plume, while well EPA 2-
5 is shown as being in the interior 01 the RCRA plume (ESI, Figure 6-5). As can be seen
from the data 01 Table 9 01 the RifFS report, the observed values 01 all four BETX
compounds have consistently been observed at relatively high levels at well EPA 2-5. At
well EPA 2-4, values slightly above detection levels have been sporadically observed for all
BETX compounds except ethylbenzene. These results are believed to be consistent with
the observations associated with the BETX plume originating at the KN property, where a
plume 01 dissolved BETX compounds in excess 01 MCLs and proposed MCLs is located
within a plume 01 floating hydrocarbons 01 greater extent (RifFS report Figure 60).
EPA recognizes that there is not a perfect correlation between the presence of free
hydrocarbons floating on the water table and the presence 01 elevated levels olBETX
compounds. EPA agrees with Dr. Sullivan and recognizes that free hydrocarbons floating
on the water table, or free hydrocarbons held in the aquifer pores above or below the water
table, can constitute continuing sources of ground water contamination. Consequently, the
proposed remedial action includes continuation of the ongoing removal action involving
vapor recovery and free hydrocarbons recovery, as well as extraction and treatment of
contaminated ground water. In addition, continued ground water monitoring following
termination of the remediaJ action will detect any effects 01 continuing contaminant sources
so that remediaJ actions can be reinstituted if necessary.
'.
EPA will continue to coordinate the planning and implementation 01 the CERCLAIRCRA
clean up activities 10r the ground water problems at the site.
TOPIC: PCP and Other Contaminants Heavier Than Water
Comment #22: -...No effort has been made to obtain verticaJ profile of PCP at any location.
Since bedrock elevations are also not mapped, which can give potential trap locations for
these heavier contaminants...Given that PCPs were detected in the vicinity 01 the
Burlington-Northern Railroad right-01-way, there is the potential that heavy wood treating
waste may exist and have accumulated within depressions 01 the bedrock surface".
EPA Resconse #22: PCP was reported at quantifiable levels in nine wells, and estimated
levels in another four wells, in March 1987. The proposed MCL of 200 ugfL was equalled or
exceeded at only 10ur wells, only one of which (EPA 2-10) was immediately downgradient 01
the industrial areas south 01 the Brookhurst Subdivision. '
The wells at which PCP was reported are widely scattered throughout ,the study area, and
cannot be correlated with any industrial source. PCP was reported in an upgradient well
(EPA 1-13 at 200 ug/L) and in a bedrock well (EPA 2-1 at an estimated 47 ug/L). PCP was
reported in ground water at six locations along the Burlington Northern Railroad right-ol-
way, but it was not detected at another nine comparable locations along the railroad right-
of-way. PCP was not detected in ground water prior to the March 1987 sampling event,
and in only one instance was PCP reported subsequent to March 1987 (an estimated 26
ug/l in well EPA 2-6 In April 1989). The RVFS report notes that PCP was not detected in
any ground water samples collected during the RifFS. Although PCP was not detected in
ground water during the RI/FS, the commenter's suggestion is valid and possible PCP
contamination will be evaluated in au 2 for the site.
14
-------
mbresp6
SECTION III. STATE CONCERNS
-,
At the public meeting, representatives of the State of Wyoming made brief statements to
describe the State's position on the proposed remedy. Those comments, provided in
Exhibit 3, are summarized below and followed by EPA's response.
Comment #23: "Wyoming DEO;WOD concurs with the selection of alternatives in Operable
Unit #1 and the need for additional investigation of the subsurface soil contamination at the
. sources for Operable Unit #2."
('
EPA Response #23: EPA believes that the selected alternative is the best remedy for
protection of public health and the environment and appreciates the concurrence of the
State in the selection.
Comment #24: "The proposed CERCLA plan and measures being developed under RCRA
to address the contamination from the LARCO property need to be integrated into a single
comprehensive planning and remediation effort."
EPA Response #24: To the maximum extent practicable EPA will continue to coordinate
the planning and implementation of the CERCLA/RCRA clean up activities for the ground
water problems at the site. In addition, EPA will also continue to ask for the State's input
and concurrence to the remedial action process to the maximum extent practicable.
Comment #25: "The Wyoming State ground water standards must be restored and
maintained within an acceptable and timely fashion under both programs."
EPA Response #25: The State's ground water standards have been considered in the
remedy selection process for OU 1. Given the technical limitations and the hydrological
conditions at the site, EPA believes that the remedial action will achieve the State standard
in a time frame that is appropriate and that is consistent of the State's goals and the
requirements of CERCLA and the NCP.
SECTION IV. PRP CONCERNS
During the public comment period, letters were received ,from the legal representatives of
KNEnergy, Inc. (KN) and Dow Chemical Company/Dowell-Schlumberger, Inc. (Dow/DSI).
These letters are provided as Exhibits 4 and 5. Specific comments are summarized below
and EPA's responses follow.
Comment #26: Representatives of Dow/DSI "are concerned that EPA's proposed Remedial
Action Plan ... calls for the creation and independent study of a 'second operable unit' for
soils...DSI and Dow object to the DSI site's inclusion in the 'second operable unit.'"
EPA Response #26: EPA will evaluate remaining source areas in OU 2 and, as necessary,
will determine whether further action is required for contaminated subsurface soils in the
vicinity of the industrial properties that were identified during the RI/FS and represent a
possible continuing source of ground water contamination.
EPA believes additional consideration of the contaminant source areas is necessary to
ensure the long-term effectiveness of the ground water clean up. The RI focused primarily
on contaminated ground water and did not address mechanisms which may transport
contaminants from soils to water. Removal actions for the KN and Dow/DSI facilities
15
-------
mbresp6
prevent further migration from source areas into residential ground water. Questions
remain concerning the ability of the removal action to eliminate Sources of contamination.
Possible contamination at oow/oSI will be included for consideration in OU 2 until further
study indicates that there are no sources of contamination at the oow/oSI facility. EPA
acknowledges the removal actions that oow/oSI have performed to date at the site.
Comment #27: The attorneys for oow/oSI "submit that the underground biological
treatment as proposed in alternative V6 is unnecessary." and that EPA consider the "option
to select a natural attenuation remedy for the oSI site."
EPA Resconse #27: EPA's selected remedy, particularly Alternative V6, incorporates
natural attenuation for the downgradient portion of the VHO plume. Although the
alternative as described in the Proposed Plan contemplated in-situ bioremediation as an
option for the downgradient portion of the VHO plume, EPA has not included in-situ
bioremediation in the selected remedy for the reasons outlined in the ROO.
;)
Comment #28: oow/oSI commented that they support the alternative described in the
proposed plan. "oSI and oow agree with EPA that, with the installation of a permanent
municipal water supply for the subdivision; all human exposure pathways have been
eliminated...the municip81 water supply has eliminated the ground water pathway."
EPA Resconse #28: EPA does not agree that the ground water pathway has yet been
"eliminated." Rather, because of the municip81 water supply, exposure via the ground water
pathway has been reduced. One go81 of remedi81 action in operable unit 1 will be
elimination of this exposure pathway.
Comment #29: Representatives of KN submitted the following comments:
.
From a management standpoint, EPA should consider each remedial
alternative as a separate operable unit.
.
EPA lacks the authority under CERCLA to address the KN-related materials
at the site. .
.
Assuming that EPA has jurisdiction under CERCLA to address the KN-related
materi81s, there is no ARAR for floating product.
EPA Resconse #29: In response to the first comment, EPA has considered separating the
remediaJ action for the BETX and VHO plumes into individual operable units. However, in
light of the close proximity of the plumes and the hydrogeologicaJ conditions at the site,
remedial actions at one plume would effect the remedlaJ actions and potentially the
migration of contaminants in the other plume. Therefore, EPA believes that the remedial
action for the BETX and VHO plumes should be coordinated as a single operable unit. The
State of Wyoming is concerned that the contamination at the site be "Integrated into a
single comprehensive planning and remediation effort.. Although the State is referring
primarily to coordination between the CERCLA action and RCRA measures for the plume
emanating from the LARCO facility, it is apparent that any separation of the CERCLA action
would only add to the State's concerns.
.
In its comments on the Proposed Plan, KNEnergy, Inc. has asserted that EPA lacks
authority under CERCLA to address releases from the KN facility. KN bases this contention
on the assertion that "the CERCLA petroleum products exclusion applies to KN-related
materials at the Site." Specific81ly, KN contends that the hydrocarbon recovery and
16
-------
mbte8C)8
<.
recycling component of Alternative 84, and the ground water and soil treatment actions
involved in the remedy involve petroleum products and, therefore, fall within the petroleum
products exclusion.
EPA disagrees with KN's characterizatio'n of the contaminants released from the KN facility,
and does not agree that the petroleum products exclusion is applicable to releases from
the KN facility. Documents which form the basis of EPA's determination concerning the
inapplicability of the petroleum exclusion to releases from KN's property are contained in
the Administrative Record for the Site. This documentation includes information submitted
to EPA by KN,1 as well as the Expanded Site Investigation, the KNEnergy Engineering
Evaluation/Cost Analysis, and the RI/FS.
KN operates a natural gas fractionation, compression, cleaning, odorizing and transmission
facility on the southern border of the 8rookhurst subdivision. There are three sources of
contamination on KN's property. One source was a flare pit, into which KN placed
numerous wastes, including hydrocarbon products and solvents, which were then burned.
A second source was a catchment area, a low spot in the ground to which run-off was
diverted. The third source was the plant itself, which, at some time in the 1960s, and
perhaps continuing thro~gh the 1 980s, released absorption oil.
The flare pit, originally an earthen impoundment, was used to collect spent materials
generated by the facility. Materials that may have been placed in the flare pit include: 1)
crude oil condensate, 2) absorption oil, 3) emulsions, antifoulants, and anticorrosive
agents, 4) liquids accumulated in the flare stack, 5) potassium hydroxide treater waste, 6)
lubrication oils, and blow down materials from equipment in the plant. In 1985, a concrete-
lined flare pit replaced the earthen pit. Use of this new pit was discontinued when it was
decommissioned in 1987.
Absorption oil is a generic term for a product used at the KN facility to absorb contaminants
from the natural gas stream. Used absorption oil was released in 1965 when an
underground pipe burst and injected several thousand gallons of the substance into the
ground beneath the facility. Additional releases occurred from the flare pit, from the
catchment area, and as a result of gradual losses from facility operations.
Pursuant to section 101 (14), section 101 (33), and section 104(a)(2) of CERCLA, petroleum
products are excluded from the definition of hazardous substances.2 KN contends that the
contamination released from its facility consists entirely of petroleum products.
Contaminants of concem released from the KN facility consist of benzene, ethylbenzene
toluene, and xylene (BETX). Although these compounds are constituents of petroleum
KN's submittals to EPA on the petrOleum exclusion 1ssu81nclude a report entitled 'Appllcabillty of the
Petroleum Product Excluslcn to HydrocarbOn Product Released From the KNEnergy Facility,' Adrian Brown
ConsultantS. Inc.. Febtuary 20, 1990; a report entitled 'Response to EPA Questions on 'Applicability of the
Petroleum ProdUCt Exclusion to Hydrocarbon ProdUCt R8I8aS8d From the KNEnergy Casper compressor
Facility," Adrian Brown Consultants, Inc., March 30,1990; and a letter from Elizabeth H. Temkin and Jeffrey B.
Gray to Ben Garcia, Remedial Project Manager, concerning 'Appllcabillty of the Petroleum Products Exclusion to
KNEnergy Facility,' dated April 3, 1990. EPA has also considered !(N's 104{e) response and Other information
contained in the AdminiStrative Record. Information and commentS concerning KN's petroleum exclusion claim
as it relates to the listing of this site on the National Priorities USt can be found in the record for the NPL liSting,
2, This exclusion pertains to .petroleum, including crude oil or arry fraction thereof which is not otherwise
specifiCally liSted or designated as a hazardous subStanCe under subparagraphs (A) through (F) of this
paragraph and the term does not Include natural gas. liquefied natural gas, or synthetiC gas usable for fuel or
mixtures of natural gas and such synthetic gas.' 42 U.S.C. Section 9601 (14).
17
-------
mbresp6
products, they are also designated hazardous substances pursuant to section 101 of
CERCLA, 42 U.S.C. section 9601. EPA believes that the CERCLA petroleum exclusion is
not applicable to releases of these hazardous substances from the KN facility.
Contamination emanating from the flare pit is not subject to the petroleum exclusion
because it consisted of hazardous wastes mixed with petroleum products. See
memorandum entitled "Scope of the CERCLA Petroleum Exclusion Under Section 101 (14)
and 1 04(a)(2)," OSWER Directive No. 9838.1, July 31, 1987. Materials deposited in the flare
pit did not consist of natural gas, but were wastes either generated in the processing of
natural gas or drained from the natural gas pipeline. Moreover, the used absorption oil
source does not implicate the petroleum exclusion because absorption oil is a product
used to pick up contaminants in the processing of gas. The samples of product recovered
by KN in the subdivision showed levels of contaminants in excess of those that would be
expected to appear in "new" absorption oil. Used oil that contains hazardous substances at
levels which exceed those normally found in petroleum are subject to CERCLA jurisdiction.
See Memorandum entitled "Scope of the CERCLA Petroleum Exclusion Under Section
101(14) and 104(a)(2)," OSWER Directive No. 9838.1, July 31,1987. The contaminants in
used absorption oil, specifically elevated levels of benzene, are hazardous substances to
which a CERCLA response may be directed. In addition, according to the memorandum
entitled "Scope of the CERCLA Petroleum Exclusion Under Section 101 (14) and 104(a)(2),"
OSWER Directive No. 9838.1 , July 31, 1987, "where a petroleum product and an added
hazardous substance are so commingled that, as a practical matter they cannot be
separated, then the entire oil spill is subject to CERCLA response authority."
II
Finally, benzene is not only an ingredient in petroleum, it is also a component of many
solvents. Once the benzene is in groundwater its source cannot be conclusively
determined, and since it may have come from solvents, it is subject to remediation under
CERCLA.
For these reasons, EPA is acting within its CERCLA authority in selecting a remedy for the
site that addresses the contamination released from the KN facility, including ground water
and soil treatment as well as hydrocarbon recovery and recycling.
KN has also commented on the lack of an ARAR for floating hydrocarbons. The layer of
hydrocarbons floating on ground water presents a continuing source of ground water
contamination, and thus presents a potential health risk. The floating product must,
therefore, be considered within the scope of site clean up. MCLs for ground water
contamination do exist, as discussed in the ROD. Clean up of substances causing MCLs in
ground water to be exceeded is a logical approach to achieving site remediation goals, and
clean up of the floating product is, accordingly, driven by MCLs for the constituents of the
product. Moreover, ARARs do not define the limits of EPA's clean up authority. In
accordance with CERCLA and the NCP, EPA's actions may address releases or potential
releases of hazardous substances, and, as discussed in detail above, EPA has determined
that the floating product is a hazardous substance and is not subject to the petroleum
exclusion.
Exhibits
Exhibit 1 - Letter from EPA
Exhibit 2 - Letter from Dr. Sullivan
Exhibit 3 - Letter from State of Wyoming
Exhibit 4 - Letter from lawyers representing Dow/DSI
Exhibit 5 - Letter from lawyers representing KN
18
-------
EXHI BIT 1
C?i:::.
~
~V
UNITED STATES ENVIRONMENTAL PROT.ECT10N AGENCY
REGION VIII
999 18th STREET - SUITE 500
DENVER! COLORADO 80202-2405
Ref:
8HWM-SR
September 21, 1990
Ms. Pat Neville
6312 East Mustang
Evansville WY 82636
Dear Ms. Neville:
At the recent public meeting we held regarding our Proposed
Plan for cleaning up ground water at the Mystery Bridge Road/U.S.
Highway 20 Superfund site, you said that benzene, ethylbenzene,
toluene and xylenes (BETX) had been detected in your residential
well. You asked if the proposed treatment for VHOs would
e)iminate BETX from your well.
According to our records, your well was sampled during the
Expanded Site Investigation (ESI) in April 1987. Table 6-11 of
.the ESI report indicates that BETX concentrations found in the
sample taken from your well are below the maximum concentration
limits (MCLs) established under the federal Safe Drinking Water
Act.
Below are BETX concentrations found in the sample from your
well compared to the established MCLs:
Chemical
Your Well
MCL
Benzene
Ethylbenzene
Toluene
Xylenes
2 ug/l
10 ug/l
13 ug/l
52 ug/l
5 ug/l
700 ug/l
2,000 ug/l
10,000 ug/l
We have not found BETX compounds above detection limits in
samples taken several times from monitoring wells near your
property from 1987 through 1989. The detection limits used were
usually less than 5 ppb, which is at or below maximum
concentration limits (MCLs) for these compounds. Because
monitoring wells are constructed to provide precise information
about contaminants in the aquifer, the monitoring well samples
are probably a better indication of BETX in ground water in that
area than results from residential wells.
Table 9 in the Remedial Investigation/Feasibility Study
(RI/FS) report, which I sent to you, shows monitoring well data
for EPA 2-3 (approximately 250 yards southwest of your property),
08G 13 (approximately 250 yards northwest of your property), and
EPA 1-1 (approximately 250 yards southeast of your property).
-------
The enclosed map shows these wells surrounding your
property. These are the wells which would indicate if
contamination is moving toward your well. As you can see from
Table 9, none of the wells contains BETX above detection limits.
The most recent sampling, conducted in July of this year, show
the same results.
In addition, LARCO well MW-49 (see map), lies
between your well and the plume emanating from the
property. No BETX was found in samples taken from
July.
directly
LARCO
this well in
Given this sampling data, we have concluded that there is no
correlation between the plumes emanating from KN or LARCO and any
BETX in your well.
In response to your question concerning the effectiveness of
the remedy on non-VHO contamination, EPA believes that if the
proposed remedy performs as expected, contaminants from KN Energy
and DowIDSI, including non-VHOs, will be reduced to levels that
are in compliance with federal and state regulations and the
health risks from ingestion of the ground water contaminated from
these sources will be reduced to acceptable levels.
If you have any questions, please feel free to call me at 1-
800-759-~372, ext. 1526.
~
Sincerely,
~/~-~
Bert Garcia
Remedial Project Manager
2
-------
~
.-
1
-:.'('('0 -
~
-N-
6""11'
T .'J
QOI, 11
\ "'"
...
6""" ,....... ~vJ'I"
T') T.e.
..........
6""57
T.')
....,.c,-,".
MW-4,
-12000 -
-
6""1.1
~
.
L
.-.
G....I.1.
.
w
a:
.
..
..
o
-------
EXHIBIT 2
90 ~~'~ -2 p~ 3: 48
August 2, 1990
~.~..c ~.~r:~='~~. ~ ~i~'~ '.,' ~.'.),,{.c.
I MI.- . . . r;'.. 1011
. .. '. -. .-'" t ~...'i, I":'. 'it
-,.
Bert Garcia (8~R)
Ranedial Project Manager
U. S. Environmental Protection Agency
999 18th Street
Cenver, CO 80202
-
.1
'. .
RE: Mystery Bridge ~/U .S. Highway 20 Public Ccmnent
--
Enclose::1 are my caments on the Feasibility St1Jdy an:i the Proposed Plan for
the Mystery Bridge tbad/U. S. HighNay 20 SUpe.rfuOO Site Natrona Camty,
WyaT1ing.
You may mail your response to:
Dr. Patrick Sullivan
4405 CaTW1Che Drive
Laramie, WY 82070
~~
-------
..,
. COMMENTS ON THE UNITED STATES ENVIRONMENTAL PROTECTION
AGENCIES FEASIBILITY STUDY AND TIlE PROPOSED PLAN FOR
THE MYSTERY BRIDGE ROADIU.S. HIGHWAY 20 SUPERFUND SITE
NA TRONA COUNTY, WYOMING
()
TABLE OF CONTENTS
1. Characterization of the Alluvial Aquifer..................................................1
Aq u ifer Homo genei ty [[[1
Modeling Analysis......... ................. ................ ..............................................3
Bedrock Surface and Heavy Organics ..................................................3
2. Trace Element Distributions and Cleanup................................................4
3. Sou thwest Soil Gas Analysis [[[4
-------
"
CO!v1MENTS ON THE UNITED STATES ENVIRONMENTAL PROTECTION
AGENCIES FEASIBILITY STIJDY AND 11iE PROPOSED PLAN FOR
THE MYSTERY BRIDGE ROADIU.S. HlGHWA Y 20 SUPERFUND SITE
NATRONA COUNTY, WYOMING
,\
The comments provided in this assessment deal with three
major deficiencies of the June 1990 RIIFS Report and their impact on
"
the selected remedial actions.
These deficiencies pertain to 1) the
characterization of the alluvial aquifer, modeling assumptions, model
sensitivity analysis, and bedrock surface and heavy organics, 2) trace
element distributions, 3) the use of PID detectors instead of FID
detectors in the southwestern portions of the site for soil gas
analysis, 4) aquifer homogeneity and modeling, and 5) implications
of vertical sampling errors.
1.
Characterization of the Alluvial Aquifer
Aquifer Homogeneity
The RIIFS assumes that the alluvial aquifer is composed of
homogenous porous media that is a "poorly sorted clay to sandy clay
with a coefficient of permeability ranging from 3.9 x 10-3 to 5.6 x
10-5 em/see" that was determined from five samples (page 28).
"The horizontal component of flow in the alluvial aquifer is
consistently to the northeast with only minor and local. variations."
(page 29).
These statements imply that modeling of groundwater flow and
contaminate
transport is accurately predicted and, thus, the
years for the VHO plume to clear the subdivision is
However, the following should be noted:
estimated 6
reasonable.
-------
a)
There
were
only
eight
wells
(Le.,
opportunities
installed in
to
characterize
the alluvium in' the
subdivision)
the
~
Brookhurst area.
No detailed split-spoon sampling (or boring logs)
were correlated or compared to determine alluvial soil texture
variations.
b) No resistivity studies (or borings) were completed to
determine the potential presence of old river channels which should
have been obvious due to the site location.
The presence of the free
hydrocarbon plume from the west side of the site which is at almost
a 45 degree angle to the VHO plume is a good indication of the
presence of at least one old channel through the subdivision.
c) Aerial photos of the subdivision in 1962 clearly show that
the initial segment of Elkhorn Creek is man-made and the current
contamination that exists at this site follows this man-made channel.
How is this factor incorporated into the modeling of the alluvial
aquifer?
d) The VHO plume models in the 1987 Site Investigation show
trends toward the west side hydrocarbon plume direction.
The geologic data provided in the RIIFS do not support an
interpretation of a relative uniform alluvial aquifer. It is strongly
recommended that a more detailed characterization of the alluvial
-2-
-------
aquifer be completed before implementing a no-treatment option in
the Brookhurst subdivision.
Modeling Analysis
The discussion of the sensitivity analysis pertaining to the
.J
prediction of contaminant transport modeling (beginning on page
107) of VHO plume is only theory. What actual laboratory or field
tests were performed to verify the selected conditions?
known with models, "garbage in, garbage out"!
As we all
The real issue with the model predictions pertain to previous
Superfund remedial actions.
The EPA has had many years of
experience in the remediation of other sites contaminated with the
same
VHO plumes.
The. predictions and sensitivity analysis
pertaining to the Brookhurst site would be more believable if the
EP A could provide one or more examples of how modeling and the
subsequent
sensitivity
analysis
have
actually
performed
In
predicting remediation effectiveness for other sites.
That is, the sites
do not have to be identical, either the sensitivity analysis theory
works or it does not.
Given that the EPA is depending upon theory to assure
residence that the site will be clean in six years, there should be
some proof that the modeling and sensitivity analysis works before
implementing the no-treatment option in the Brookhurst subdivision.
Bedrock Surface and Heavy Organics
The limited number of wells completed in the Brookhurst area
does not provide many data points to determine a reasonable
- 3 -
-------
representation of the bedrock surface contours.
Given that PCPs
were detected in the vicinity of the Burlington-Northern Railroad
right-of-way, there is the potential that heavy wood treating waste
L
may exist and have accumulated within depressions of the bedrock
surface.
In this regard, the EPA should at least proceed with a
preliminary investigation to determine that wood treating wastes are
not present at the site before implementing a no-treatment option of
the Brookhurst groundwater.
2.
Trace Element Distributions and Cleanup
EPA monitoring wells 1-3, 1-8, 1-9, 1-10, 2-11 and 2-14 that
occur within or adjacent to the KN Energy BTEX plume all either
exceed chromium and/or lead MCL's.
What is the extent of the
distribution of these trace elements with this plume?
The RI/FS does not discuss trace element hazards and the
removal of these trace elements (air stripping is not an effective
method for the removal of these elements from water).
Are lead and chromium not a hazard?
proposed treatment system is not adequate.
If they are a. hazard, the
3.
Southwest Soil Gas Analysis
"The soil boring program was designed to inves.tigate the
nature and extent of contamination in each potential source area
or to verify the absence of
contaminants in areas without soil vapor detections."
-4-
-------
"OBO performed a soil vapor survey to identify potential source
areas of volatile organic contamination to ground water on the
industrial
properties
near the
Subdivision.
The
survey
was
conducted on each of twenty industrial properties along the southern
boundary of the Subdivision and across U.S. Highway 20. The soil
~
vapor survey was not meant to replace laboratory analyses, but were
designed to identify potential source areas for the placement of soil
borings for sampling and laboratory analyses."
"The majority of the soil vapor samples were collected at a
depth of 3 ft and analyzed on site using a Photovac Model 10S70
portable GC air analyzer.
Instrument internal libraries and BTEX gas
standards
were
used
for
the
preliminary
identification
and
quantification of specific volatile organic compounds and a total
photoionizable
volatile compound
concentration.
The
total
concentration of volatile organic compounds was determined by
summing the peak areas on the chromatogram and using the relative
response factor for benzene for quantification.
were reported as parts per million of benzene."
As such, all results
"Shallow soil borings were advanced to a depth of 42 inches at
four locations on each industrial property with
no identified
contamination. "
"The four samples from. each
property were
composited to form a single sample which was analyzed for HSL
semi-volatile compounds and those metals listed in Appendix III of
40 CFR Part 265 according to USEP A CLP protocol."
Using the procedure defined above, the GC air analyzer having
a photoionizable (PID) detector will not detect compounds such as
methylene chloride and acetone.
In order to detect these compounds
- 5-
-------
a FID detector would be required.
Because a GC with a PID detector
was used. a potential plume containing methylene chloride and
acetone
that is indicated in
residential well waters
was not
in ves tigated.
This is suggested for the following reasons:
"
a) NA TCO is a potential source of methylene chloride and
acetone based on use of paint thinners. painting and stripping.
b) Numerous residential tap water analysis in the area adjacent
to NA TCO showed elevated levels (an order of magnitude) of
methylene chloride and acetone compared to other Brookhurst
samples.
This is significant.. even if it is proposed that both are
laboratory or blank contaminants and should not have been ignored.
c) Soil borings that were collected were composite samples and
many volatiles may have been significantly diluted prior to analysis
(and only represents 4 data points).
d) As a consequence of this procedure, many potential
compounds from the southwest area may not have been detected.
As a result. no EP A monitoring wells were installed within the
southwestern portion of the subdivision.
It is highly recommended
that a more detailed groundwater investigation in this area be
completed to determine the absence of groundwater contamination
in this area.
-6-
-------
4.
Modeling and Homogeneous Aquifer
The model in this RIIFS used hydraulic conductivity values
based on the Horslov method (except for one value from a pump
test). One should be careful in using Harslov method values for the
following reasons:
a) The Horslov method gives only an order of magnitude
estimate for hydraulic conductivity (Chirlin in Spring 1989 issue of
Ground Water
Monitoring Review).
b) There were not enough data collected for a proper Horslov
analysis.
To use the Horslov analysis, there must be enough data to
form a straight line.
observed in slug tests.
Sometimes, a double straight line effect is
If a double straight line effect is observed, than the second
straight line is representative of the aquifer conductivity (Bouwer in
May-June 1989 issue of Ground Water Jr.). When only 2 or 3 data
points are available (which is the case here), than hydrologist cannot
select the proper straight line, and therefore the results from the
analysis is questionable.
Contaminant plume shapes clearly indicates the heterogeneities
in the aquifer.
The values used for model sensitivity analysis (Table
. .
10) and the basis for these values, clearly show the heterogenous
nature of the aquifer.
While "porosity range for these tests was 24 to 34%..." (page
28), sensitivity analysis uses 35 to 45% porosity.
An explanation for
-7-
-------
this discrepancy is not provi~ed.
Saturated aquifer thickness varies
u
from 14 to 39 feet (table 10), which is again a clear indication of
heterogeneities present.
"
In addition, a description of the model is not provided, which
makes it difficult to evaluate how the model is calibrated/validated.
If it is a numerical model, then numerical dispersion can artificially
lower the contaminant concentrations and underestimate the time
needed for remediation.
On the other hand, if the model is based on
the analytical solution, than heterogeneities cannot be incorporated
in the model.
5.
Free Product Plume from LARCO
EP A 2-4 well is located inside the free product. plume from
LARCO.
However, ground water sample from this well shows
Toluene, Xylenes and Ethyl Benzene below detectable limits. These
components are commonly found in gasoline and refinery products.
Absence of these product in the ground water. sample at EP A 2-4
well is a clear indication of sensitivity of dissolved hydrocarbons on
the vertical location where sample was taken.
Hydrology literature is full of examples where dissolved
product plume extends much further than the. free product plume.
Remediation efforts should take that into account. Also, adsorbed
and trapped hydrocarbons in the vadose zone (unsaturated region)
will continue to act as source of contamination for the ground water.
Trapped hydrocarbons can exist even inside the water table due to
seasonal water level fluctuations.
-8-
-------
. .
of the BTEX plume that is considered for remediation?
How does the LARCO result influence the EP A's understanding
What is the
extent of the BTEX plume, given questionable sampling and or
analysis?
6.
PCP and Other Contaminants Heavier Than Water
The LARCO example shows the sensitivity of the dissolved
contaminants
concentrations to the vertical position of the sample
collection point. If dissolved product is sensitive to the vertical
location of the sample than, heavier contaminants are obviously
sensitive to the sample location.
No effort has been made to obtain
vertical profile of PCP at any location.
Since bedrock elevations are
also not mapped, which can give potential trap locations for these
heavier contaminants.
Based on these problems, it is strongly recommended that more
detailed analysis for PCP profiles be determined.
-9-
-------
-- -
-".
EXHIBIT 3
DEQ STATE:"(£.~T
SUPERFUND ?ROGRAM ?ROPOSED ?!..AN
C.tSPER, './YO~lING
JUl.':' 18, 1990
My
nace
1.3
l.arry
RobLn:;on
and
represen t
the _yom1ng Depar:~ent of
EnvLronmental Quality, Water ~alit.y Division.
The Depart~ent would liKe :0 take
this opportunity to than\< the E?A for its cooperation and error~s to provide for
participation in the process of identifying alternatives for addressing problems
1n the Brookhurst area.
Present stat. activH1e~ 1n the Srookhurst area incl~e enforcement actions
involvLng LLttle America Refining Company (l.ARCO), KN Energy, Dowell Sc~lumberger,
Texaco Ref1nln& and Marketing, Inc., Amoco Pipeline Company and WYce Pipeline
Company.
It is the respon~ibi1ity of DEQ to ensure that the requirements 01' the
Wyoming Environmental Quality Act are adequately acdressed during the fede:-al
process and
to
take appropriate
1ndependent
regulatory
measures
as may
be
necessary.
This means ensur1ng that grounawater quality wlthln the Brookhurst
Subd1v1~lon 1~ returned to an maintained at Cl~~ I or domestic use standard,.
It h the po:sH10n of the Department that the propo,ed aoO:lons identif1ed ~n
Alternat1ve:s 84 and V6 should be imple~ented as soon as possible.
We also concur
with the EPA proposal to ~rov1de additional study of the subsurfaoe 50i1 contami-
nation sources on the ~~ Energy and Dowell Schlumcerger properties during Operable
Un 1 t 2.
It 1s also our position, however, that the proposed plan being developed
under CERCLA and the plan being de~eloped under RCRA to addres, the con~ination
plume enterLns the Brookhurst Subd1v 1~lon fro:! l.ARCe property need to
6rated 1nto a single comprehensive planning and remediation effort.
~e inta-
This is
nece5~ary 1n order to insure that groundwater Quality with1n tne Subdtv1s1on is
protected or restored to Class I criteria within an acceptable and consistent time
-------
/'~
.---' .
!'r-ame.
It i3 not po33ible to ~ke an appropriate deoision concernin& ~he olean up
of' ~he 'lHO plume wiChtn Broo\(hu/'":s~ Subdiv1310n without knoloOing wh.a~ actions ....il~
be taken and ....oat time frame will be established to re!Dediate the UR~ plt;e
with1n the Brookhurst Subdivision.
A siiniricant factor in sehcting Alternative '16 and tne longer time t'ra.11e
for clean up 1s the fact that several of the other alternatives have the potential
to negat i vely impact the LARCO plume.
Using th13 as an evaluat ion cri ceria is
inappropriate 1n light of the fact that no t1~e frame or remediation plan has been
developed for the LARCO plume.
This is of particular concern when the LARCO plume
has been identified as having the greater health risl:.
We recognize tnat E?A
intends to adQress the L~RCO plume through the RCRA proces$. However, we feel that
the CERCL.A process must be structured suc.~ that it concurrently addresses this
matter 1n order to adequately evaluate the remediation altarnat.ives which hav'-'
been pre~ented.
Croundwater contamination and possible associated health et'!'ect3 w1th1n the
Broolchurst Subdivision are an 1mediate and continu.ing problem.
E:tt ended time
frames for clean up are a matter of concern to the DEQ. We agree t.hat EP~ proceed
i0oi1 th the recolIIDended removal actions at Dowell Schlumberger and !QJ Energy.
we
recommend developini a comprehensive p~posal involving both HCRA and CERCLA
programs result1ng 1n a timely remediation of all groundwater contaminat1on within
Brockhurst Subdivision.
I In
2
.
-------
,
,~ j
EXHIBIT 4
.,..,' I
-' \
/\ I:v ~ \
~ CI-'
~ .I
.;
MONTGOMERY. GREEN. JARVIS.
KOLODNY & MARKUSSON
",.o...(.~., ..a"
IC[VI,..' .......ruzIO
'..C" ; C.O$$
~CTC. S OU$It.ItC'
JAMES I( C-I£['"
10'0 Srl,tC:",TrC....""1iI ST'8(C.
S\,,/iT( 1700
Oc:~'Wr. C:::l~:>."'OO
802&5
r(~(...o""( f )0)1' J.. .eco
TC\-CC::.,(III)O)I '59~ )'90
... .. (1"'" ;".'''5
Joyce,- ,;( "41(1l1li5
JOE\.. .. I(O~OON.
SCOTT. "C c....
O(,..,.NIS '"" "'.AI(USSO~
C "'IC~"C:\. "ONTGOW(."
.011l:IIIT.. "UI\'E"'ltu.C
''''0'''''55 JI.."C""""'"
;C..\,O \, ..u'CIII~U$
JO"'" T 'V.'" vOO."'$
August 3, 1990
VIA HAND-DELIVERY
Mr. Bert Garcia
Remedial Project Manager
United States Environmental
Protection Agency
Region VIII
999 18th Street, Suite 500
Denver, Colorado 80202-2405
RE:
Mystery Bridge Road/Highway 20 Site
Superfund Site, Natrona County, Wyoming
Proposed Remedial Action Plan
Dear Mr. Garcia:
The following comments on the U.S. Environmental Protection
~gency' s ("EPA") proposed Remedial Action Plan ("RAP") for the
Mystery Bridge Road/U .S. Highway 20 Superfund Site ("the site")
in Natrona County, Wyoming, are submitted on behalf of Dowell
Schlumberger, Inc. ("DSI") and the Dow Chemical Company ("Dow").
DSI and Dow generally concur in EPA's selection of alternative B4
and V6 as the preferred remedial alternatives for the site.
However, DSI and Dow have some concerns about certain aspects of
the RAP as set forth below. The comments contained herein are
submitted for EPA's review and consideration prior to the final
selection of the site remedy. DSI and Dow request that these
comments be included in the administrative record for this site.
DSI and Dow's primary concern about the RAP relates to the
scope of the. investigation already undertaken and the future
activity proposed as a "second operable unit." As EPA is fully
aware, pursuant to an Administrative Order on Consent (" AOC")
entered by EPA in this matter on December 15, 1987, DSI, Dow and
KNEnergy, Inc. ("KN") agreed to perform a Remedial Investiga-
tion/Feasibility Study ("RI/FS") of what was then termed the
"Brookhurst Subdivision site," an area of mixed
residential-industrial use one mile east of Evansville, Natrona
County, Wyomi:,;g, "bounded by the North Platte River on the north,
Sinclair/Little America Refinery on the west, the Burlington
Northern Railroad on the south, and the Brooks-Hastings
-------
Mr. Bert Garcia
August 3, 1990
Page 2
Irldustrial complex on the east.". (AOe, III, 1.) Dow, DSI and K..~
retained O'Brien & Gere Engineers, Inc. ("OaG" or "RIfFS contrac-
tor") to perform the RIfFS. In June of 1988, oaG submitted a
workplan to E?A for the RIfFS which provided, in pertinent part,
that soils within the "study area" identified in the AOe, above,
would be investigated along with other media including surface
and ground water and air. A sampling plan for the investigation
of all these media was submitted to EPA in October, 1988.
Neither the Aoe nor the RIfFS workplan or sampling plans approved
by EPA provide for division of the study area into "operable
units."
Pursuant to the RIfFS sampling plan, soils within the
Subdivision and on each of the industrial properties, including
the DSI site, were sampled. At EPA'S request, additional soil
sampling to bedrock was performed at the DSI site in September of
1989 (RIfFS Report..S6.03.2, June 1990). The results of these DSI
soil sampling campaigns and the air, surface and ground water
studies were regularly reported to EPA over a two-year period in
technical memoranda and other documents. The results of these
investigations formed the basis of the final RIfFS report first
submitted to EPA in January, 1990, and accepted by EPA in June of
1990. EPA directed this process and regularly commented on OBG's
efforts. EPA accepted the investigation as complete.
Dow and DSI are concerned that EPA's proposed Remedial
Action Plan for the site calls for" the creation and independent
study of a "second operable unit" for soils. The RAP does not
define the location and boundaries of this operable unit and the
scope of the study contemplated. Having participated at great
expense in a thorough study of the soils on the DSI site, DSI and
Dow object to the DSI site's inclusion in the "second operable
uni t. " AS the direct result of a vigorous source removal action
undertaken by DSI and Dow at the DSI site in 1987, (see, RIfFS
Report S6.03.1, June 1990 and "Summary of Removal Activities
through May 31, 1988 at the Dowell-Schlumberger Facility, Casper
Wyoming", June 18, 1988 (We 1988)), concentrations of contami-
nants of concern in ground water have decreased dramatically and
residual soil levels do not exceed those set by EPA (RIfFS
Report, SS6.03.4 and 8.02.2, June 1990; see also David Duster
letter to Swiatoslav Kaczmar dated Novembe~22~989, attaching
Stefancheck soil action levels for constituents of concern at DSI
site). Furthermore, soil sampling firmly established that soil
constituents from the DSI site do not extend beyond the site's
boundaries. Clearly, the DSI site should not be included in a
"second operable unit" requiring additional soil sampling of
DSI's site and DSI should not bear the burdens associated with
that operable unit. Should EPA pursue additional soil studies,
DSI and Dow encourage EPA to adhere to the sampling and quality
assurance and quality control protocols previously followed in
-------
Mr. 8ert Garcia
August 3, 1990
Page 3
this matter in order to achieve a consistent and reliable ',""ork
product.
v
OSI and Dow agree with EPA that, with the installation 0: a
permanent municipal water supply for the Subdivision, all human
exposure pathways have been eliminated. The data generated
during the RIfFS support the conclusion that air, soil and
surface water do not present an exposure pathway and the munici-
pal water supply has eliminated the groundwater pathway. There-
fore, DSI and Dow request that EPA adopt this position in any
addi tional risk assessment done for this site as part of the
"second operable unit."
Lastly, OSI and Oow agree with EPA's assessment that concen-
trations of constituents of concern in ground water within. the
Brookhurst subdivision are now at such reduced levels that
natural attenuation will effectively resolve any continuing
ground water impacts. Indeed, ground water concentrations both
within the Subdivision and at the OSI site have decreased dramat-
ically since 1987 (RIfFS Report, S8.02.2, June 1990). This
attests both to the efficacy of the DSI removal actions and the
natural attenuation processes at work in the Subdivision. OSI
and 'Dow anticipate that additional ground water sampling per-
formed during the Remedial Design, Remedial Action ( "RDfRA" )
phase of this matter will show further reductions in ground water
values since the last round of sampling was conducted in Septem-
ber, 1989 (RIfFS Report, S8.02.2, June 1990). These continuing
reductions demonstrate that the DSI removal actions were suffi-
cient and that the natural attenuation processes at work within
the Subdivision are also effectively at work at the OSI site.
Therefore, DSI and Dow submit that the underground biological
treatment as proposed in alternative V6 is unnecessary. Eased
upon the foregoing, DSI and Dow request that the Record of
Decision entered in this matter provide EPA the option to select
a natural attenuation remedy for the DSI site.
In sum, with the few exceptions set forth above, DSI and Dow
agree with and support the Remedial Action Plan proposed by EPA.
Very truly yours,
MONTGOMERY, GREEN, JARVIS,
KOLODNY & MARKUSSON
;V ~..tifr~r';
H. Keith ~arvis
By
HKJ:alr
-------
Mr. Ser<:: Garcia
August 3, 1990
Page 4
cc:
J. P. Srosset, Dowell Schlumberger, Inc.
w. J. Witt, The Dow Chemical Company
S. Rook, Esq., The Dow Chemical Company
L. Korte, KNEnergy, Inc.
E. Temkin, Esq., Davis, Graham & Stubbs
S. Kaczmar, Ph.D., O'Brien & Gere Engineers, Inc.
-------
EXHIBIT 5
-.
J /'
.',fv .1~'" V
( / \ ~'~' ,<-/,~'
, ';'~Nr
DAVIS. GRAEAX & STUBBS
ArOQ..,.c"'S .1' Ji.-
."""''''010'''- O.C:. O'l'tCC
SV1~t .700
. )70 5£"C""'1'C£""'1',. ~TQr:C!
O!:NV!:~. CC...O~AOO 60Z0Z
5.l",r ""-C Clf'" ~,r,cc
SUITt 500
,ZOO .....""crce""1'''' 5T1~CCT. "",W'.
."'5-'...OTO"', O.C. l:lOJe'l.OZ
-C.CO-O"C lOl'lIll'IIIIIIO
"'''''\''';''''0 AOOl:tC5S
POST O'''ICC eo. 18~
SUIrt. ,e,OO.!P
. t..Ac....t ~...rc "~..,'.:g
~o CAS. 501",.:." "!:...o'.c
s......~ ......."c. : ."', J""'. :].'1. :':'6
..t""ca-c...c eO'.3~e'6::':C
O!:NV!:R, CO...ORAOO 60Z01-0165
Tt~C."O"t 303'1191'90000
""'CS'NI"'C 303-893-1)79
1'C\.O 413728 ~GS 0". vO
~81..t ~"'''GRAW. ce"",vCR
..J~""Q~V B. c;ROY
e~i!.7J7Z
-
August 2, 1990
VIA HAND DELIVERY
Mr. Bert Garcia
Remedial project Manager
U.S. Environmental Protection Agency
Superfund Remedial Branch, 8HWM-SR
999 18th Street, Suite 500
Denver, CO 80202
Re:
Mystery Bridge Road/U.S. Highway 20 Site -
Superfund Program Proposed Plan
Dear Mr. Garcia:
On behalf of our client, K N Energy (ltKNIt), we are
providing written comments on the Proposed Plan (the "Plan") for
the Mystery Bridge Road/U.S. Highway 20 site (the "Site").
specifically, our comments will focus on the following: (1) KN
believes that from a management standpoint EPA should consider
each of the two remedies selected as a separate operable unit
("OU")(~, the site should be divided into discrete units based
on plume delineation); (2) EPA lacks the authority under the
Comprehensive Environmental Response, Compensation, and Liability
Act, as amended (ltCERCLA"), to address the fractions of petroleum
or natural gas detected at the KN property (the "KN-related
materials"); and (3) even if EPA has jurisdiction under CERCLA to
address the KN-related materials, there is no applicable or
relevant and appropriate requirement ("ARAR")' for the floating
product. While some ot our comments concern OU 2, because the
Plan is limited to OU 1, we reserve our right to provide
additional comments on OU 2 until such time as EPA proposes a
plan for OU 2.
FROM A MANAGEMENT STANDPOINT. EPA SHOULD CONSIDER EACH REMEDIAL
ALTERNATIVE AS A SEPARATE OPERABLE UNIT.
As noted on the Figure on page 2 of the Plan, it is
clear that the Site can be divided into discrete units based on
plume deli~eation. In tact, EPA has agreed in the Plan that the
plumes should be addressed separately. Therefore, from a remedy
-------
~:-. Ber": Ga:-cia
Augus~ 2, 1990
?age 2
wanage~en~ s":and?oint and for ease of i~?le~enting and overseeing
t~e separa~e :-e~edies, ~~ proposes es~ablishing ODs on a
geographical or plume basis. Under KN'S proposal, eac~ pl~we and
any associated areas of concern would be considered a sepa:-ate
au,~ with EPA entering into a separate consent decree that ~ould
i~plement the separate remedial actions for each plume. The
cleanup phases, which EPA proposes in the Plan, could be
i~plemen~ed as pa~ of each au, as necessary.v
~
Dividing the site into aus on a geographical or plume
basis is appropriate for a number of reasons. First, given that
the Plan proposes separate remedial treatment systems for the
BETX and VHO plumes, .it only makes sense to treat each plume
separately by establishing a separate ou for each plume. Second,
treating the plumes separately is advantageous from a technical
perspective. Each treatment system will be constructed by an
individual company (~, KN will likely implement Alternative 84
and The Dow Chemical Co. ("DOw") will likely implement
Alternative V6) and each system will be operated independently of
the other system. Moreover, the success of cleaning up each
plume will not depend on the effectiveness of'~both treatment
systems. Instead, the clean up of each plume will depend
entirely on the effectiveness of the treatment system for t..~at
plume. Third, it makes sense from a management and oversight
perspective to divide the site into OUs on a plume basis.
Because the timeframes for completing the remedial actions, the
milestones, and the reporting requirements will likely be
different for each plume, because ARARs and progress toward
meeting those (and other) remedial goals will be different for
each plume and because community relations aspects of the overall
remedy can best be dealt-with by separating the plumes, it would
1/ In the Plan, EPA has designated remedial action phases as
OUs. Specifically, as proposed by EPA, each au would address
Site-wide impacts, except those attributable to LARCO, and would'
address both the soil and ground water media (although apparently
OU 1 would focus on qround water and OU 2 would focus on soil).
KN proposes instead establishing OUs on a geographical basis and
each OU could, as necessary, address the media of concern in a
phased approach.
Z/ It is unclear from the Plan what components make up each au.
specifically, because the Plan is so vague, it is difficult to
know what is addressed in au 1 and what is addressed in au 2.
For example, the Plan seems to address floating product in both
ou land OU 2. Therefore, until EPA provides more specificity
concerning what each au will address, KN has a concern about
EPA's phased approach.
-------
Mr. Bert Garcia
August 2, 1990
Page 3
L
be more appropriate for EPA to oversee management of and
compliance with the remedial alternatives if they are in separate
aus.
If EPA establishes each plume as a separate au, it
obviously makes sense for EPA to enter into a separate consent
decree for each au. Each consent decree, respectively, would
address the phased approach EPA has in mind for cleaning up each
of the plume-based OUs. In addition, entering into separate
consent decrees is not only more efficient from EPA's oversight
perspective but also more equitable from the PRPs' perspective.
specifically, it would be unfair for EPA to hold KN liable for
Dow's plume and treatment system and vice versa. In fact, it
would appear arbitrary and capricious for EPA to do so.
consequently, KN requests that EPA consider establishing plume-
based aus and entering into a separate consent decree for each
au.
EPA LACKS THE AUTHORITY UNDER CERCLA TO ADDRESS THE KN-RELATED
MATERIALS AT THE SITE.
As you know, the materials currently detected at the KN
property consist only of fractions of petroleum or natural gas.
As a result, the CERCLA petroleum products exclusion applies to
the KN-related materials at the site and, as a matter of law, EPA
lacks jurisdiction over the KN-related materials. More
specifically, the hydrocarbon recovery and recycling action, a
component of Alternative B4, is a remedial activity involving
petroleum product. Likewise, the ground water and soil treatment
actions also involved KN-related materials. and, as a result~ fall
within the CERCLA petroleum products exclusion. Therefore, as to
those aspects of Alternative B4, the petroleum products exclusion
precludes EPA from relying on its CERCLA jurisdiction as to au 1.
Nevertheless, as you know, KN has voluntarily
undertaken numerous activities at the site to prevent the
introduction -of KN-related materials into the environmental
(~, decommissioning the flare pit and changing .the facility's
operation) and to clean up the residual KN-related materials
(~, undertaking the removal action). CERCLA does not mandate
that KN take these activities or any additional remedial
activities. Rather, KN has undertaken these activities as a
matter of good corporate citizenship. As you also know, KN
stands ready to take any necessary and reasonable additional
action required by the circumstances. Meanwhile, however, KN
reserves the right to invoke the CERCLA petroleum products
exclusion with respect to the KN-related materials at the site.
-------
Mr. Bert Garcia
August :2, 1990
Page 4
ASSL~ING EPA HAS JURISDICTION UNDER CERCLA TO ADDRESS THE KN-
RELATED MATERIALS. THERE IS NO ARAR FOR FLOATING PRODUCT.
KN believes that it is logical to recover as much
floating product as is technically feasible and cost effective.
In fact, as part of its removal action, KN has voluntarily
recovered floating product located beneath its property. KN has
also proposed to EPA to extend its floating product recovery
system offsite to recover the floating product that apparently is
present beneath the Burlington Northern ("aNn) property. Again,
KN has done this, not because CERCLA mandates such an action, but
to ensure the protection of the environment. Moreover, KN has
done this even though from a health standpoint, petroleum product
in the free or floating product phase at the site is not a
significant health risk because there is no credible exposure
pathway.
KN's position concerning the mandatory removal of
floating product at the site is based on the language in CERCLA.
CERCLA mandates that remedial actions selected at a site meet
ARARs. ~ 42 U.S.C. S 9621(b). As noted in the RI/FS Report,
the proposed ARARs for the site encompass a variety of federal
and state standards. There is, however, no ARAR for floating
product. As a result, once the ground water beneath the floating
product meets MCLs, KN believes that the remedial alternative has
achieved its goal and has satisfied CERCLA's requirements.
continued recovery of floating product is not mandated. In fact,
to pursue additional removal of free product on a diminishing-
returns basis would not be cost effective and therefore would be
inconsistent with the NCP. ~,~, 55 Fed. Reg. 8666, 8726
(Mar. 8, 1990).
As KN has mentioned to EPA, KN will continue to remove
floating product from its property as well as from under the BN
property, as needed, until such time as it is technically
infeasible to remove any more floating product. KN will not
agree to remove All of the floating product as EPA appears to
want done.J! CERCLA does not mandate this requirement,.
1/ In fact, KN disagrees with EPA's statement on page 3 of the
Plan to the extent it seems to require the total elimination of
all contamination at the Site. Specifically, in the Plan, EPA
states in the context o~ discussing the removal actions that
n[c]ontamination ot water trom soils was stabilized but not
entirely eliminated during the removal actions." plan at 3
(emphasis added). CERCLA does not mandate the entire elimination
of hazardous substances. It requires that the remedial actions
(continued...)
-------
.Mr. Bert Garcia
August 2, 1990
Page 5
'.
Furthermore, it is not warranted from a public health standpoint.
Finally, it is not even possible from a technical standpoint to
eliminate all the floating product. Therefore, KN will refuse to
cooperate with EPA to the extent EPA seeks to remove gll floating
product as part of the overall remedy for the Site.
One final comment is that of the three plumes at the
site the KN plume has clearly had the smallest impact on the
environment. In fact, there has been no documented impact on the
Brookhurst subdivision from any KN-related materials.
Nevertheless, KN to date has done more than any other company to
address its materials and has done so voluntarily. Specifically,
KN has undertaken extensive response actions--decommissioning the
flare pit, instituting effective work practices and removing KN-
related materials from the soil and ground water--to address the
situation quickly and effectively. Even though its impact on the
environment has been ~ minimis, KN has done these response
actions as quickly as possible to ensure that public health and
the environment were protected. KN respectfully requests that
EPA consider KN's efforts when deciding how to implement the
proposed remedial alternatives for the Site and in deciding
whether to issue separate consent decrees to implement the
remedial alternatives.
KN appreciates the opportunity to submit these written
comments on the Plan. If EPA should have any questions
concerning KN's comments, please contact either Elizabeth Temkin
or me.
Sincerely,
~B.~
Jeffrey B. Groy
for
DAVIS, GRAHAM & STUBBS
cc:
Elizabeth Wald, Esq.
A. Michael Gaydosh, Esq.
Lawrence J. Corte, Esq.
Adrian Brown
H. Keith Jarvis, Esq.
l/ ( . . . continued)
meet a number of requirements, including attaining ARARs.
Therefore, KN disagrees with EPA's statement to the extent it
misleads the public as to how clean the site will be once the
remedial alternatives achieve their goals.
------- |