PB98-963124
EPA541-R98-115
December 1998
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Burlington Northern (Somers Plant)
Somers, MT
7/21/1998
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 8, MONTANA OFFICE
FEDERAL BUILDING, 301 S. PARK, DRAWER 10096
HELENA, MONTANA 59626-0096
EXPLANATION OF SIGNIFICANT DIFFERENCES
Burlington Northern (Somers Plant) Site
Somers, Flathead County, Montana
United States Environmental Protection Agency
July 1998
I. INTRODUCTION
This Explanation of Significant Differences (ESD) is being issued by the U.S. Environmental
Protection Agency (EPA) to modify certain remediation criteria established in the Record of
Decision (ROD) issued by EPA on September 27, 1989 and modified by the previous ESD
issued on June 26, 1992 for the Burlington Northern (Somers Plant) Site (hereby referred to
as "Somers Plant" or the "Site") and identifies the documents that serve as the basis for the
determination.
EPA, in consultation with the Montana Department of Environmental Quality (MDEQ), and
after consideration of documents prepared pursuant to the first Five-Year Review of the
Somers Plant and other documents in the Administrative Record, has determined that
modifications to the remediation levels established in the 1989 ROD are required to
incorporate criteria developed since the ROD was issued.
The modifications to the remedy described in this ESD do not fundamentally alter the overall
approach of the remedy selected in the ROD. However, the modifications to the remediation
goals at the site significantly change the scope and performance of the selected remedy.
Therefore this ESD is required by the NCP and EPA guidance.
In accordance with Sections 117(c) and 121 of the Comprehensive Environmental Response,
Compensation and Liability Act of 1980 (Superfund), as amended, 42 U.S.C. Section 9601,
et seq. ("CERCLA"), and the regulations at 40 C.F.R. Section 300.435(c)(2)(i), the National
Oil and Hazardous Substances Pollution Contingency Plan (NCP), this ESD has been
prepared for the following reasons:
• to provide the public with an explanation of the nature of the changes to the
remedy;
• to summarize the circumstances that led to the changes to the remedy; and
• to affirm that the revised remedy complies with all statutory requirements.
O
Printed on Recycled Paper
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MDEQ (formerly the Montana Department of Health and Environmental Sciences, MDHES)
concurred on the ROD issued on September 27,1989, and has participated in the review of
information leading to this ESD, including the Five-Year Review Report which includes the
Protectiveness Evaluation and the Five-Year Review Site Visit (Roy F. Weston, Inc., 1995a
and 19955). MDEQ has reviewed and concurred on this final ESD.
This document presents a summary of the changes to the selected remedy and a synopsis of
information on the Site. The Administrative Record, which contains this ESD and the
complete documentation supporting the revisions selected herein, is available for public
review at the locations indicated at the end of this report.
II. SITE HISTORY AND BACKGROUND
The Burlington Northern (Somers Plant) Site is located in northwestern Montana in the
unincorporated town of Somers, Flathead County. The Somers Plant was operated by
Burlington Northern Railroad (BNRR) between 1901 and 1986, and covers approximately 80
acres. The plant treated railroad ties and other miscellaneous lumber products to protect the
materials from weathering and insects. Treatment fluids used by BNRR included zinc
chloride, chromated zinc chloride and creosote/petroleum preservative mixtures. The
treatment process generated wastewater primarily consisting of steam condensate containing
zinc chloride or creosote. Floor and shop washing, drippage from treated ties pulled from
the retort onto the drip track and storage of treated ties on the property were other sources
of process-generated wastewater. Prior to 1971, BNRR discharged wastewater into a lagoon
(the "CERCLA Lagoon") located immediately south of the retort building. Overflow from
this lagoon flowed in an open ditch from the facility into a swamp on the shore of Flathead
Lake. Sometime prior to 1946, a pond formed in the swamp area (the "swamp pond")
adjacent to Flathead Lake and waste material discharged through the open ditch accumulated
there.
BNRR abandoned the CERCLA Lagoon and ditch in 1971 when the company constructed
two new wastewater holding impoundments [the Resource Conservation and Recovery Act
(RCRA) impoundments]. In 1984 BN implemented a recycling system and topped all
wastewater discharges.
In February 1984, the Montana Department of Health and Environmental Sciences (MDHES)
sampled the soils at the Somers Plant. Based on the results of this investigation, the Site was
proposed for inclusion on the Superfund National Priorities List (NPL) in 49 CFR 40320,
October 15,1984. The proposed listing cited potential adverse effects on Flathead Lake and
the water supply for the town of Somers, which drew water from the lake.
In May 1985, EPA, BNRR and Sliters Corporation (a corporation which owns a portion of
the site) signed an Administrative Order on Consent (AOC) (Docket No. CERCLA-VIII-85-
02) providing for an Emergency Removal Action in the area of the swamp pond adjacent to
Flathead Lake. The area was determined to pose an imminent and substantial hazard to
Flathead Lake because of the presence of creosote contamination in water and soil located
within two (2) feet of the shoreline. Pursuant to the 1985 AOC, BNRR removed
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contaminated soil and surface water from the swamp pond area and the drainage ditch. The
soils were temporarily placed in the lined RCRA impoundments and eventually hauled to the
BN RCRA-regulated facility in Paradise, Montana for treatment. The water was processed
at the plant. The excavated areas were backfilled with clean soil and riprap was placed along
the lakeshore.
In October 1985, EPA, BNRR, and Sliters Corporation signed another AOC (Docket No.
CERCLA-VIII-85-07) for a Remedial Investigation and Feasibility Study (RI/FS). The
purpose of the RI/FS was to determine the nature and extent of contamination at the Site, to
evaluate the impacts of contamination on public health and the environment, and to
formulate alternatives for remedial action. The field work to support the RI was performed
from the Fall of 1985 to Fall 1988. An RI/FS Report (Remediation Technologies, Inc., 1989)
was submitted to EPA in the spring of 1989.
The RCRA impoundments were closed in 1988 under the MDEQ Hazardous Waste
Permitting Program. Subsequent to the closure, a groundwater monitoring well located
adjacent to the impoundment indicated that groundwater was contaminated; therefore,
groundwater corrective action was required.
After completion of the RI/FS, a ROD was signed on September 27, 1989 (EPA 1989a). The
ROD selected a remedy and a contingency remedy for remediation of soil, groundwater and
sediments, which were determined to pose a potential threat to human health and the
environment. The selected remedy addressed the principal threats by removing the potential
for direct contact with soils, by reducing the impact of the soils and sediments on
groundwater and surface water and by treating the groundwater. The contingency remedy
was to be implemented if the selected remedy was not determined to be effective. On
December 20, 1991, the EPA entered into a Consent Decree (Civil Action No. CV-91-32-M-
CCL) with BNRR and Burlington Northern. Inc. for Remedial Design/Remedial Action
(RD/RA) of the selected remedy at the Site. The Consent Decree required performance of
a Pilot Study to demonstrate the "practicability" of the innovative bioremediation component
of the selected groundwater remedy. The Consent Decree required that the Pilot Study be
conducted prior to any soil application on the Land Treatment Unit (LTU).
EPA issued an ESD in June 1992 (EPA, 1992) that modified the elements of the selected
remedy, based on the "practicability" determination required in the ROD. The results of the
Pilot Study were presented in the Remedial Design Investigation Report for the Former
Somers Tie Plant (Remediation Technologies. Inc., 1991). The study was conducted to more
accurately define and quantify the conditions under which the groundwater could be
successfully remediated.
Operation of the 14.4 acre LTU commenced in 1994 following removal of soil from the
CERCLA Lagoon to a 15 foot depth (22.300 cubic yards), Swamp Pond Area to a 12 foot
depth (19,030 cubic yards), and the Drip Track/Retort Building (10,000 cubic yards). After
the first year of LTU operation, the ROD remediation levels for soils were achieved. The
second year of operation of the LTU produced a 19% reduction in carcinogenic Polycyclic
Aromatic Hydrocarbons (cPAH) concentrations (RETEC 1995a). The cPAH reduction
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allowed BN to apply a second lift of soil to the LTU in the fall of 1995 in accordance with the
1989 ROD requirements.
The groundwater remedy consisting of five (5) extraction and ten (10) injection wells and a
granular activated carbon (GAC) water treatment plant was put into operation at the end of
April 1994 to capture and treat contaminants at the CERCLA Lagoon and downgradient of
the CERCLA Lagoon. The system is designed to hydraulically contain Polycyclic Aromatic
Hydrocarbons (PAH) contaminated groundwater within the boundary of the influence of the
well fields. Extracted water is chemically and mechanically treated for free product,
dissolved organics and iron at the site Water Treatment Plant prior to reinjection.
Groundwater contamination at the site consists of Dense Non Aqueous Phase Liquids
(DNAPL) within and adjacent to the CERCLA Lagoon and dissolved components
downgradient from the lagoon.
Excavation activity in the swamp pond and slough areas resulted in the determination of the
need for mitigation of damage to wetland environments. The Fish and Wildlife Service
delineated and determined functional values of the wetland area in July 1993 (USFWS, 1994),
which are described in the Wetlands Compensation Determination (EPA, 1994c). BNRR
reconstructed the swamp pond in accordance with the plan and conducts semi-annual water
quality sampling and assessment of vegetation recovery for the area.
A Five-Year Review of the Remedial Action at the Somers Plant was performed in April
1996. The objectives of the Five-Year Review were: (1) to verify that the remedy is operating
and functioning as designed and, (2) to evaluate whether the remedial action selected for the
site remains protective of human health and the environment. The Five-Year Review
conducted for the Somers site was performed in accordance with the Office of Solid Waste
and Emergency Response (OSWER) Directives 9355.7-02 entitled "Structure and Components
of Five-Year Reviews", (EPA 1991) and 9355.7-02A, entitled "Supplemental Five-Year
Review Guidance", (EPA 1994a).
The Five-Year Review of the Somers site was triggered by the initiation of a portion of the
remedy by the responsible party, Burlington Northern Railroad, in 1991. The Five-Year
Review includes recommendations for the evaluation of remediation levels for the site to
ensure that the remedy is protective of human health and the environment and that the
remediation levels are current and consistent with CERCLA Section 121, and EPA and State
policy and guidance.
III. SUMMARY OF THE 1989 RECORD OF DECISION
The objectives of the remedy selected in the 1989 ROD are to reduce human exposure to soil,
sediment and groundwater contaminants of concern. The components of the remedy are
excavation and biological treatment of soils within an onsite LTU, and in situ biological
treatment of contaminated groundwater within the water table aquifer, supplemented by
extraction and treatment of contaminated water through a mechanical and chemical
treatment process to remove free product, metals and particulates, and dissolved organics
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through oil/water separation, equalization, oxidation, particulate settling and granulated
activated carbon filtration.
A list of the components of the original remedy selected for the site can be found on pages 40
through 46 of the 1989 ROD (EPA, 1989a). The remedy was modified by the 1992 ESD
(EPA, 1992) based on the Pilot Study for ground water contaminants of concern. A brief
summary of the original and modified remedy is provided below. The ROD remediation
levels for contaminated soil and ground water are presented in Table 1.
• The soil remedy involved excavation of creosote and zinc contaminated soils in the
CERCLA lagoon, drip track, drainage ditch, beneath the retort building and in the
slough and beach areas. Some soil left below the water table in the CERCLA lagoon
and swamp would be treated as part of the groundwater component of the remedy.
The ROD included provisions for groundwater monitoring and post-closure care for
up to 30 years or deed restrictions placed if hazardous constituents remained. Due to
RCRA land disposal restrictions, a demonstration of no-migration of hazardous
constituents was conducted to satisfy requirements.
• The original feasibility study alternative was modified for the selected remedy to
exclude the excavation of the beach sediments. The sediments were not excavated due
to a determination that the ecological risks to Flathead Lake from beach excavation
outweighed the benefits of removing the contaminated sediments.
• Excavated areas were required to be backfilled with clean borrow soils and
revegetated. The remedy also included replacement or restoration of wetlands lost
during the remedial action.
• The ROD identified groundwater remedy involved the evaluation of the applicability
of innovative technology, either hot water flushing of contaminated groundwater,
ozone/UV or peroxide/UV treatment at the surface and in situ biological treatment of
residual contamination.
The 1991 Consent Decree required that a pilot test of the hot water flushing and in situ
biological treatment technologies be conducted to evaluate their "practicability" in the
low permeability hydrogeologic conditions at the Site. Implementation of the soil
remedy was restricted until after the pilot test was conducted, as the contingency
remedy involved deep excavation and incineration of soils. The remedy involved the
installation of injection and recovery wells in the CERCLA Lagoon and the swamp
pond area. Recovered groundwater would be treated in a chemical reactor in order
to reduce contaminant levels.
• Identification and implementation of institutional controls to restrict use of
groundwater downgradient of the contaminated areas was required.
• Monitoring activities required to assess the performance of the components of the
remedy would be conducted throughout the life of the remedial activities. Activities
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involve monitoring of groundwater wells and semi-annual monitoring of the Somers
municipal supply well until cleanup concentrations are achieved.
• The Site conditions will be reviewed no less than every five years after initiation of the
remedial action to ensure that the remedy remains protective of human health and the
environment.
In 1992, EPA modified the remedy selected for the site through an ESD. The ESD presented
the "practicability" determination for the innovative bioremediation technology for the
groundwater component. The significant differences between the remedy described in the
1989 ROD and the 1992 ESD are listed below:
1. Excavation of additional soils in the CERCLA Lagoon and the Swamp Pond
Areas increasing the total excavated materials from 11,700 cubic yards to
41,000 cubic yards. Additional excavation was conducted to aid the
remediation process.
2. Increase the size of the Land Treatment Facility from 10 acres to 14 acres to
decrease the time required to meet remedial objectives and cleanup
remediation levels. Procedure for completion of land treatment described in
the ROD (p. 42) was not modified.
3. Elimination of the hot water flushing option of the groundwater remedy due
to the low permeability of the aquifer materials. Excavation of additional soil
in the CERCLA Lagoon would remove more source material and aid the
remediation process.
4. Change in soil and groundwater cleanup times. Decrease the time to achieve
soil remediation levels to 4 to 6 years rather than 10 years. Increase the
estimate to achieve groundwater remediation levels from 10 to 15 years to 50
years.
IV. SUMMARY OF SIGNIFICANT DIFFERENCES TO THE REMEDY
The significant differences between the remedy selected in the 1989 ROD and the 1992 ESD
and in this ESD are:
1. The soil remediation level for carcinogenic polycyclic aromatic hydrocarbon
(cPAH ) is revised from 36 to 57 milligrams per kilogram (mg/kg) calculated
as benzo(a)pyrene (B(a)P) equivalents using the revised B(a)P cancer slope
factor.
2. The limitations established in the 1989 ROD for pyrene, naphthalene and
phenanthrene in soils are removed. EPA cites in part the rationale provided
by field data, toxicological assessment and the language within the No-
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Migration Petition as reasons for removing these requirements. Further
discussion is provided below.
3. The soil remediation level for total non-carcinogenic PAH is revised from 1875
mg/kg to 1500 mg/kg based on the revisions to the Reference Dose (RfD) for
naphthalene equivalents which has been revised from 0.005 to 0.004 mg/kg-
day.
4. The groundwater remediation level for total non-carcinogenic PAH is revised
from 0.3 pg/L to 40 jtg/L based on the current procedure of not considering
co-carcinogenicity and the change in the Reference Dose (RfD) equivalent to
naphthalene noted in item 3. above.
5. The groundwater remediation level for total phenolics is revised from 15,000
/tg/L to 6000 ng/L calculated, based on revisions in the RfD for Phenol and
RfD values for other phenolic compounds.
Only those changes in Section IV paragraphs 1 through 5 above are being made to the
remedy selected in the 1989 ROD and 1992 ESD. All other aspects of the selected remedy
documented in 1989 ROD and 1992 ESD remain the same. A detailed rationale and
background for the changes in this ESD follows.
Risk-Based Remedial Goals
Risk-based cleanup remediation levels established in the ROD for contaminated soils and
groundwater were reviewed to determine the impact of changes in the toxicological
assessment of contaminants of concern (COCs) including total PAHs, cPAHs and phenolic
compounds using current EPA toxicological information and updated relative potency factor
(RPF) and Toxicity Equivalency Factor (TEF) guidance (EPA, 1989b, EPA 1994b, EPA
1993). This review effort was performed to assess the degree of protectiveness afforded by
the current risk-based remediation levels documented in the 1989 ROD for Somers.
The residential exposure scenarios were used as the basis for 1989 cleanup levels presented
in the ROD for groundwater and soil. The site-specific exposure parameters established in
the human health evaluation for these scenarios were used in the calculation of chemical
concentrations for specific target risk levels. In the absence of site-specific information,
standard default exposure parameters were used in the calculations. Risk-based remediation
levels were also prepared for contaminants with MCLs for comparison purposes only (EPA,
1994e).
A summary of the results of the risk-based cleanup goal review effort is presented in Table
1.0. Details regarding the methods and input parameters used to develop the 1998 risk-based
remediation levels presented in these tables are provided in the Supplemental Remedy
Protectiveness Evaluation (Roy F. Weston. 1995b).
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Soils Remediation Levels
The 1989 risk-based remediation levels for total carcinogenic and non-carcinogenic PAHs in
soils differ from the 1998 risk-based remediation levels. The differences are based on
revisions in the slope factor for B(a)P and the establishment of new RfD's for non-
carcinogenic PAHs. Table 3 provides a summary of the slope factor and RfD revisions.
Total cPAH
The 1989 risk-based remedial remediation levels for total carcinogenic PAHs for soils,
established using residential exposure scenarios differ from the 1998 risk-based remediation
levels. The difference is due to revisions in the slope factor for B(a)P from 11.5 to 7.3
(mg/kg-d)'1. Also, the 1989 remediation levels were applied to the sum of all cPAHs with the
assumption that each cPAH was equal in carcinogenic potency to B(a)P. However, since
promulgation of the ROD, cPAHs have been assigned RPFs which are used to convert
individual cPAHs to B(a)P equivalent concentrations, thus resulting in less potent
classification and having an effect of decreasing the estimated risk from cPAHs. The
determination of compliance to the revised remediation levels for soils can be accomplished
using EPA Region VIII Superfund Technical Guidance, Development of Toxicity Values for
PAHs (EPA, 1994b).
Using the updated slope factor for B(a)P results in a change of the soil treatment cPAH
limitation from 36 mg/kg to 57 mg/kg.
Total non-carcinogenic PAH
In 1989 non-carcinogenic effects of total PAHs were based upon the assumption chat ail PAHs
were as toxic as naphthalene with an RfD of 0.005 mg/kg-d. Since promulgation of the ROD,
the RfD for naphthalene has been revised from 0.005 to 0.004 mg/kg-d. Additionally, RfDs
for other PAHs have been derived. As with the groundwater, those PAHs that have no RfD
are conservatively evaluated as equal to most potent known RfD (naphthalene).
Application of the revised RfD produces a soil cleanup level for non-carcinogenic PAHs of
1500 mg/kg to replace the 1875 mg/kg level found in the 1989 ROD.
Naphthalene, Pyrene and Phenanthrene
EPA and MDHES established soil cleanup levels in the 1989 ROD that were based on both
risk assessment results and proposed (Best Demonstrated Available Treatment) BDAT
requirements for land disposal of the wastes found at the Site. These remediation levels
include.
Contaminant(s) Cleanup Goal Source
Total cPAH 36.0 mg/kg Risk Assessment
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Total PAH 1,875 mg/kg Risk Assessment
Naphthalene 8.0 mg/kg BDAT Requirements
Phenanthrene 8.0 mg/kg BDAT Requirements
Pyrene 7.3 mg/kg BDAT Requirements
The remediation levels listed above that are based on BDAT requirements were incorporated
within the 1988 ROD due to the land disposal restrictions (LDRs) that applied to the remedy
(a land treatment unit) proposed for the wastes found in soils at the Site. The BDAT
limitations were included in the ROD due to the lack of other numerical standards that
applied to the contaminated soils. The BDAT limitations were derived from a demonstration
using an incineration technology not a bioremediation technology as was selected for
implementation at the Somers site.
It was recognized by both Burlington Northern and EPA at the time of the ROD that
achievement of the pyrene level by land treatment would likely prove most difficult because
the BDAT limitations were based on incineration as the applicable treatment technology.
The No-Migration Petition for the Somers site was submitted by ReTec, Inc., as Appendix
D of the Remedial Design investigation Report (December 1991). The petition evaluated
migration potential for all contaminants of concern at the Site, including pyrene, naphthalene
and phenanthrene. The petition was reviewed by EPA and MDEQ and commented on
extensively by EPA. EPA approved the final No-Migration Petition with the issuance of the
1992 ESD on June 26, 1992. The study demonstrated that no migration of contaminants and
no adverse impact to human health or the environment would occur during operation and
closure of the LTU. 40 C.F.R. Section 268.6 allows EPA to approve a waiver of the Land
Disposal Restrictions BDAT standard based on a successful No Migration Demonstration and
Petition.
Removing the BDAT requirement for pyrene will not compromise the overall protectiveness
of the selected remedy. Pyrene is now included in the list of total PAH compounds ( no
longer considered by EPA to be carcinogenic) whose sum total concentration must be
remediated below the risk-based cleanup goal of 1,875 (modified to 1,500 by this ESD). By
remediating the total PAHs below this level, EPA has determined that the residual
concentrations of PAHs (including pyrene) will be protective of human health and the
environment.
Field data available in BNRR's LTV Annual Operations Reports also indicate that BDAT
requirements for both naphthalene and phenanthrene are achievable with the selected soils
remedy. During operation of the Site LTU, remediation levels for these compounds are
achieved prior to achievement of remediation levels for total carcinogenic PAHs. Thus, the
standard set for total carcinogenic PAHs would ultimately govern the total time required to
fully remediate a soil lift within the LTU.
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With a potential for expediting the time required to remediate the contaminated soils at the
Site while still maintaining the degree of protectiveness for human health and the
environment, and EPA's approval of the No-Migration Petition, EPA is removing the soil
treatment levels for pyrene, naphthalene and phenanthrene. As explained above, the degree
of protectiveness for human health and the environment will be maintained by remediating
the total PAH compounds to 1,875 mg/kg and the carcinogenic PAH compounds to the new
risk-based goal of 57 mg/kg. All other requirements for remediating the contaminated soils
within the LTU (as listed above) will remain in effect.
Only the initial treatment levels are being changed by this ESD. The ROD requirement for
additional treatment of soils, after attaining the new initial treatment levels, until the annual
reduction in cPAH is less than 20 percent, remains unchanged. The additional ROD
requirement that health risks posed by direct contact with site soils be reduced to at least
1x10-5 also remains unchanged.
Groundwater Remediation Levels
Total non-carcinogenic PAHs
In 1989, the Risk Assessment for the BN Somers site identified a concentration for total PAHs
of 50 /ug/L as being protective against noncancer health effects. This level was calculated
based on the assumption that all PAHs had an RfD equivalent to naphthalene (0.005 mg/kg-
d). However, this risk-based value was not selected for incorporation in the ROD due to
concerns at the time over carcinogenic promotion or co-carcinogenicity of noncarcinogenic
PAHs. Therefore, a cleanup level for total PAHs of 0.300 /ug/L was set, using a value one
order of magnitude greater than the risk-based cleanup level for carcinogenic PAHs
Currently, carcinogenic promotion by noncarcinogenic PAHs is not considered in estimating
potential carcinogenic effects from exposure to PAHs (EPA, 1994c) and a health-based level
using RfDs for noncarcinogenic effects is appropriate. As noted above, since issuance of the
ROD in 1989, the RfD for naphthalene has been revised from 0.005 to 0.004 mg/kg-d, and
many of the PAHs have been assigned individual RfDs. Those PAHs for which no RfD has
been assigned have been assumed to be equal to the most potent known RfD (naphthalene =
0.004 mg/kg-d).
The recalculation of the health based clean-up goal is 40 ug/L. To determine compliance
levels, exposure point concentrations (EPCs) for individual PAHs are recalculated based on
the revised RfDs and converted to naphthalene equivalent concentrations using RfD ratios.
These naphthalene equivalent concentrations are then summed to represent total PAHs
present in groundwater for comparison to the revised clean-up level.
There is no change in the exposure risk to the public due to this revision in the remediation
level for non-carcinogenic PAHs.
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Total phenolics
For total phenolic compounds, the RfD for phenol has been revised to 0.6 mg/kg-d, resulting
in a revised clean-up goal of 6000 pg/L which replaces the 1989 ROD level of 15,000. As with
the cPAHs and PAHs, RfD values for other phenolic chemicals of concern have been derived
(phenol, 2,4-dimethylphenol, 2-methylphenol, 4-methyphenol). Again, EPCs for individual
phenolic compounds are converted to phenol equivalent concentrations using ratios of RfDs,
which are summed to represent total phenolics present at the site for comparison to the
revised clean-up level.
There is no change in the exposure risk to the public due to this change in the remediation
level for total phenolics.
Carcinogenic PAHs
Although federal MCLs for cPAHs have been promulgated since the ROD was issued, no
change is made to the ROD at this time because: (1) MDEQ is currently revising the Montana
WQB-7 standards for these compounds and (2) BNSF will prepare a Technical
Impracticability (TI) waiver application relative to groundwater cleanup at the Site. Updated
groundwater standards will be addressed as part of the TI waiver analysis and application.
V. SUMMARY OF STATE COMMENTS AND AVAILABILITY OF
ADMINISTRATIVE RECORD
As stated above, MDEQ has reviewed the documents that serve as the basis for this
determination and has provided comments to EPA on the documents and on this ESD. All
of the MDEQ comments were incorporated into the final reports. MDEQ has been provided
with the opportunity to review and comment on this ESD and all of their comments have been
incorporated.
Documents referenced within this ESD are part of the Administrative Record for the Somers
Site. The administrative record will also contain any written public comments that may be
received regarding this ESD. The complete administrative record for the Site is available for
public review at the following location:
U.S. EPA Montana Office Flathead County Public Library
Federal Building, Room 192 247 1st Avenue East
301 South Park, Box 10096 Kalispell. Montana 59901
Helena, Montana 59626-0096
(406) 441-1150 (406) 756-5690
Mon-Fri, 8:00 a.m. to 5:00 p.m. Mon-Fri, 8:00 a.m. to 4:00 p.m.
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VI. AFFIRMATION OF STATUTORY REQUIREMENTS
Considering the new information that has been developed and the changes that have been
made to the selected remedy, EPA, in consultation with MDEQ, believes that the remedy
remains protective of human health and the environment, complies with Federal and State
requirements that both applicable or relevant and appropriate to this remedial action or
involves appropriate waivers of these requirements, and is cost-effective. In addition, the
revised remedy utilizes permanent solutions and alternative treatment technologies to the
maximum extent practicable for the Site.
VII. APPROVAL
Mark A. Simonich, Director Date
Montana Department of Environmental Quality
Max H. Dodson, ARA Date
Office of Ecosystems Protection and Remediation
U.S. Environmental Protection Agency
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REFERENCES
Montana Department of Environmental Quality. 1995. Circular WQB-7. Montana Numeric
Water Quality Standards. August 1995.
Remediation Technologies, Inc. (RETEC). 1995a. BN-Somers Land Treatment Facility 1994
Operations Report. Somers, Montana. Prepared for Burlington Northern Railroad.
Remediation Technologies, Inc. (RETEC). 1991. Remedial Design Investigation Report for
the Former Somers Tie Plant. Prepared for Burlington Northern Railroad.
Remediation Technologies, Inc. (RETEC). 1989. Remedial Investigation and Feasibility
Study. BN-Somers Superfund Site. Volumes II & III. Exposure and Endangerment
Assessment and Feasibility Study. Prepared by RETEC, Inc., for Burlington Northern
Railroad.
Roy F. Weston, Inc. 1995a. Five-Year Review Site Visit Report. BN Somers Tie Plant.
Somers, Montana. Prepared for the U.S. Environmental Protection Agency, Region VIII,
Montana Operations.
Roy F. Weston, Inc. 1995b. Five-Year Review, Protectiveness Evaluation. BN Somers Tie
Plant, Somers Montana. Prepared for the U.S. Environmental Protection Agency, Region
VIII, Montana Operations.
Roy F. Weston, Inc. 1997. Risk Evaluation for PAHs in Drinking Water, Somers Tie Plant,
Somers, Montana. Prepared for the U.S. Environmental Protection Agency, Region VIII,
Montana Office. October 10, 1997.
U.S. Environmental Protection Agency. 1995. Office of Health and Environmental
Assessment. Retrieval from the Integrated Risk Information System (IRIS), September 1995.
U.S. Environmental Protection Agency. 1994a. Supplemental Five-Year Review Guidance,
Office of Solid Waste and Emergency Response, OSWER Directive No. 9355.7-02A.
U.S. Environmental Protection Agency. 1994b. Region VIII Superfund Technical Guidance.
Development of Toxicity Values for PAHs to use in Human Health Risk Assessments. Draft.
U.S. Environmental Protection Agency. 1994c. Letter on Wetlands Mitigation plan and
Wetlands Compensation Determination. August 1994.
U.S. Environmental Protection Agency. 1994d. Office of Solid Waste and Emergency
Response. Health Effects Assessment Summary Tables (HEAST). FY-1994 Annual.
U.S. Environmental Protection Agency. 1994e. Office of Water. Drinking Water
Regulations and Health Advisories. November 1994.
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U.S. Environmental Protection Agency. 1993. Provisional Guidance for Quantitative Risk
Assessment of Polycyclic Aromatic Hydrocarbons. Office of Research and Development,
Washington, D.C.
U.S. Environmental Protection Agency. 1992. Explanation of Significant Differences,
Burlington Northern (Somers Plant) Site, Somers Montana, June 1992.
U.S. Environmental Protection Agency. 1991. Structure and Components of Five-Year
Reviews, Office of Solid Waste and Emergency Response, OSWER Directive No. 9355.7-02,
Washington D.C.
U.S. Environmental Protection Agency. 1989a. Region VIII Montana Operations Office,
Record of Decision, BN-Somers Superfund Site, Somers, Montana.
U.S. Environmental Protection Agency. 1989b. Risk Assessment Guidance for Superfund,
Volume 1, Human Health Evaluation Manual. EPA/540/1-89-002, December 1989, Interim
Final. Office of Emergency and Remedial Response, Washington D.C.
U.S. Fish and Wildlife Service. 1994. Wetlands Delineation and Evaluation, Burlington
Northern Superfund Site, Somers, Montana. April 1994.
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TABLE 1.0
COMPARISON OF 1989 AND 1995 RISK-BASED REMEDIATION LEVELS FOR BN-SOMERS ("'e)
Contaminants of Concern
Total Carcinogenic PAHS (b>
Total PAHs - NonCancer
Effects
Phenol
Total Phenolics
Groundwater
1989 Risk Based Goal
(MB/L)
0.030 fig/L
0.300 /ig/L
Based on concern over
possible co-carcinogeniciry
__
15.000
Risk-Based 1995 Target
Clean-up Concentration
(Mg/L)
0.047 fig/L
40 /*g/L
Based on noncancer health
effects calculated using
naphthalene equivalent
concentrations
6000
6000
Soil
1989 Risk Based
Goal (rag/kg)
36 mg/kg
l,875(e)
—
3.000(c)
Risk-Based 1995
Target Clean-up
Concentration
(mg/kg)
57 mg/kg
1.500
45,000
45.000
(a) Calculated using toxicity values shown in Table 2.0.
(h) Benzo(g,h.i)perylene assessed as a potential carcinogen in 1989; not classifiable as to human carcinogenicity and assessed as a noncarcinogen in 1995.
(c) Value cited as an excavation concentration.
(d) Values obtained from 1989 ROD for BN-Somers.
(e) Methods for comparing site concentrations to risk-based remediation levels have been revised since 1989. See text for further detail.
— Risk-based value not used as goal in 1989 ROD.
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TABLE 2.0
COMPARISON OF TOMCITY VALUES USED FOR
RISK CHARACTERIZATION AT BN-SOMERS
1989 AND 1998 VALUES
Contaminant of Concern
PAHs:
Naphthalene
Acenaphthylene
Acenaphthene
Fluorene
Phenanthrene
Fluoranthene
Pyrene
Benzo(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Indeno( 1 ,2,3-c.d)pyrene
Dibenzo(a.h)anthracene
Benzo(g,h, i)perylenew
2.4-dirnethylphenol
2-meihylphenol
4-methylphenol
Phenol
Zinc
1989 Values'"
RfD (mg/kg- oSF (mg/kg-d)'1
d)
0.05 to
0.005""
0.03
0.20
0.07*
0.07«
0.07*
0.06
0.07*
0.07*
0.07*
0.07*
0.07*
0.07*
0.07*
0.07*
NA
NA
NA
0.04
0.21
11.5
11.5
11.5
11.5
11.5
11.5
11.5
11.5
1998 Values'"
RfD (mg/kg-d) oSF (mg/kg-d)-1 <">
0.004
NA
0.06
0.04
NA
0.04
0.03
NA
NA
NA
NA
NA
NA
NA
NA
0.02
0.05
NA
0.6
0.3
0.73
0.0073
0.73
0.073
7.3
0.73
7.3
-
(a) Values from Table 2 of the 1989 ROD
(b) PAH specific Slope Factors calculated from B(a)P by multiplying by RPF (see text)
(c) Values obtained through reviews of IRIS, HEAST and Safe Drinking Water Guidance (EPA. 1995. 1994d.
1994e)
(d) Provided range of RfDs for Naphthalene, however used most stringent (0.005) in calculations
(e) Assessed as a potential carcinogen in 1989; not classifiable as to human carcinogenicity and
assessed as a non carcinogen in 1998
* Value assumed equal to average RfD for other noncarcinogenic PAHs
NA Not Available
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