PB97-963152
EPA/541/R-97/170
January 1998
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Janesville Ash Beds and
Janesville Old Landfill
Janesville, WI
9/17/1997
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FINAL
EXPLANATION OF SIGNIFICANT DIFFERENCE
JANFSVILLE DISPOSAL FACILITY
(JANESVILLE ASH BEDS AND JANESVILLH OLD LANDFILL
NATIONAL PRIORITIES LIST SITES AND ADJOINING AREAS)
JANESVILLE. WISCONSIN
I. Introduction
The Janesville Disposal Facility (JDF or "the site") is located on a 65-acre parcel of land locateu
in northwestern Janesville, Wisconsin. The facility contains four different areas: the Ash Beds (a
National Priorities List or NPL Site), the Old ut-.np. the Old Landfill (another NPL Site) and the
New Landfill. All four areas have been combined and the cleanup is being addressed jointly
under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
and the Resource Conservation and Recovery Act (RCRA). The Ash Beds Site consists of five
ash beds in an area of approximately 400 feet by 400 feet, in which industrial liquids and sludges
were deposited and allowed to evaporate. The Old Landfill and New Landfill are mixed
municipal/industrial landfills which occupy approximately 18 and 22 acres, respectively. The
Old Dump area was a general refuse dump which occupies about 15 acres. The JDF as a whole
is bordered on the north by an active landfill, on the west by commercial property, on the south
and east by public recreational areas and wetlands, and on the northeast corner by a residential
neighborhood.
The U.S. Environmental Protection Agency (U.S. EPA) and the Wisconsin Department of
Natural Resources (WDNR) are the lead and support agencies, respectively, for the site.
Pursuant to Section 117(c) of CERCLA and Section 300.435(c)(2)(i) of the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP), U.S. EPA has determined that it is
necessary to make a significant change in the selected remedy for the site.
The Record of Decision (ROD) requires the installation of groundwater extraction and treatment
systems, if needed. After reviewing groundwater monitoring data collected over several years,
U.S. EPA has determined that natural attenuation has significantly reduced contaminant levels in
the groundwater. Based on improvements in the levels of groundwater contamination
downgradient of the site, U.S. EPA and WDNR have determined (i) that groundwater extraction
and treatment are not necessary to achieve regulatory requirements and to protect public health
and the environment, and (ii) that these goals can be achieved by natural attenuation of
groundwater contaminants. Contaminant concentrations in the groundwater will continue to be
monitored and U.S. EPA will periodically review monitoring data to assess whether natural
attentuation is reducing contaminant levels in a satisfactory manner.
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This Explanation of Significant Difference (ESD) will become part of the Administrative Record
File for the site, which is located at U.S. EPA's offices at 77 West Jackson Boulevard in
Chicago. Illinois. This ESD and supporting documentation are also available for viewing at the
public repository of site-related documents at the Janesville Public Library at 31A South Main
Street in Janesville. Wisconsin.
II. Summary of Site History, Site Contamination, and Selected Remedy
The Old Dump, Old Landfill, and New Landfill operated one after the other during the period
between 1950 and 1985, each closing as it reached design capacity. The Old and New Landfills
are known to have accepted both municipal and industrial wastes, including drummed solvents,
used oils, paints and paint thinners, and dried sludges from the Ash Beds Site. The Ash Beds Site
and the New Landfill are also RCRA-regulated units, closed under interim status, while the Ash
Beds and the Old Landfill were listed on the NPL. Prior to closure of the Ash Beds, the City of
Janesville excavated several thousand tons of contaminated material from the Ash Beds. Some
material was incorporated into neighboring landfills (including the Janesville Old Landfill) and
some was disposed at private hazardous waste facilities. The City of Janesville back-filled the
Ash Beds with sand and capped the area with 2 feet of clay. When the Old Landfill was closed
in 1978. the City of Janesville placed two feet ~f clay over the landfill. When the New Landfill
was closed, it was ">lso capped with two feet of clay.
Responding to an Order from the U.S. EPA, in 1987 a group of Potentially Responsible Parties
(PRPs) began a Remedial Investigation/Feasibility Study (Rl/FS) for the combined sites.
The Rl/FS confirmed the presence of hazardous constituents in the landfills and ash beds and the
risk analysis confirmed that the contaminants presenting the most health risk in the groundwater
downgradient of the site were volatile organic compounds (VOCs), including, among others
trichloroethene (TCE), vinyl chloride, tetrachloroethene (PCE), 1,2-dichloroethene (1,2-DCE),
and benzene. Secondary contaminants included arsenic, barium, manganese, and iron.
(Contaminant concentrations are discussed in Section III of this ESD.) There are no private
residential wells or municipal supply wells in the line of the groundwater plume between the
landfill and the primary groundwater discharge point, the Rock River, 1200 feet west of the site.
On December 29, 1989, U.S. EPA issued a Record of Decision (ROD) which outlined the
remedy selection process and the selected clean-up actions for the entire JDF, including the two
NPL sites. The major components of the selected remedial action were:
* institutional controls
* landfill cap improvements for the New Landfill, including gas control and leachate
collection improvements
* landfill cap improvements for the Old Landfill NPL Site
* remove and dispose of ash piles at the Ash Beds NPL Site
* maintain present cap and upgrade site drainage at Ash Beds Site
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*
continued groundwater and air monitoring
* installation of groundwater extraction and treatment system, it" needed
Wisconsin DNR concurred with the selected remedy in the ROD.
In September 1991, U.S. EPA and a group ot'PRPs (including the City of Janesville and 60
industrial parties) signed a Consent Decree under joint RCRA/CERCLA authorities for cleanup
of the entire JDF. including the two NPL sites. Since that time, the PRP group has removed all
remaining ash stockpiles for disposal and seeded, graded and maintained the clay cap of the Ash
Beds site. They have also regraded the Old and New Landfills, and installed a combined cap
which meets State and Federal regulations, including installation of a gas collection system. On
June 26, 1997, U.S. EPA and WDNR personnel conducted the final inspection of the site and
found that this work had been completed satisfactorily.
The PRPs, with oversight of U.S. EPA and WDNR. conducted three rounds of groundwater
monitoring during the Rl/FS in 1987-88, and have conducted quarterly monitoring since 1993.
This monitoring has produced a substantial body of historical and current groundwater data on
which to base a decision to substitute monitored natural attenuation for extraction and treatment
at this site. Since the original sampling in 1987, groundwater adjacent to the site has improved
greatly due to the removal of source material, a private groundwater treatment system operated at
the Parker Pan facility nearby, the installation of new and improved landfill caps, and natural
attenuation.
The following section discusses U.S. EPA's determination that groundwater has improved to the
extent that extraction and treatment is not needed at the site.
III. Explanation of Significant Difference
The ROD for this site requires groundwater to be extracted and treated if needed. Because the
Agency has now determined that it is not needed, we are issuing this ESD. The decision not to
require the installation of groundwater extraction and treatment systems is based on a decade of
water-quality data gathered between 1987 and 1997. These data are summarized in a report
entitled "Petition for Eliminating Groundwater Punp and Treat System", submitted by the PRP
group on May 29, 1997 (Petition). The Petition will become part of the Administrative Record
File for the Site. While not necessarily endorsing all conclusions stated in the Petition, U.S. EPA
believes that the data summaries included in the Petition are accurate and is in general agreement
with the technical information contained in the Petition.
The Applicable or Relevant and Appropriate Regulations (ARARs) for groundwater at the site
include the National Primary Drinking Water Standards and Chapter NR 140 of the Wisconsin
Administrative Code (NR 140). The Drinking Water Standards and NR 140 provide
concentration standards used to limit the effects of contaminants in the groundwater, including
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maximum contaminant levels (MCLs) from the Drinking Water Standards and preventive action
limits (PALs) and enforcement standards (ESs) from NR 140. MCLs. PALs. and ESs are all
stated in terms of concentrations for various contaminants. PALs are generally lower
concentrations than primary MCLs or ESs. MCLs can be either primary standards, which are
health-based, or secondary standards, which are unenforceable federal guidelines regarding taste.
odor, color and certain other non-aesthetic effects of drinking water. PALs and ESs can be
cither public health-related standards or public welfare-related standards.
Both the concentrations and the areal extent of contaminants in groundwater downgradient of the
JDF have decreased greatly since 1987. In 1987. the groundwater plume which exceeded the
PALs, ESs and primary MCLs extended over much of the area between the JDF and the Rock
River. At that time, at least five VOCs frequently exceeded PALs, ESs and primary MCLs.
The highest contaminant concentrations related to the JDF site were located downgradient of the
Ash Beds at W5 (e.g., 480 ug/1 PCE) and at W6 downgradient of the Parker Pen USA Limited
facility (e.g., 4,000 ug/1 PCE). (The high PCE concentrations observed at W6 were likely caused
by a spill at the Parker Pen facility in 1985.) By 19W, only two VOCs exceed PALs: PCE at 61
ug/1 near the Ash Beds and TCE at 27 ug/1 near Parker Pen. At well W6 near the Rock River.
TCE concentrations have decreased from over 20,000 ug/1 in 1988 to non-detect in 1997. A
detailed discussion of trends for all major contaminants may be found in the documents in the
Administrative Record which support this ESD.
The improvement in groundwater quality at the JDF site is due mainly to (i) remedial actions
taken at the site, (ii) a private groundwater treatment system at the Parker Pen facility, and (iii)
natural attenuation.
Remedial actions. Remedial actions at the JDF site include capping of the Ash Beds in 1985
just prior to the Remedial Investigation; removal of approximately 10,000 cubic yards of ash in
1996 and incorporation under the New Landfill cap; and construction of a multi-layer clay cap
over two landfills on the JDF site in 1996, which greatly lessens the infiltration of rainwater into
the landfill waste and thus lowers the migration of contaminants into the groundwater.
Private groundwater treatment system. During 1993, the Parker Pen facility operated a
groundwater extraction and treatment system to treat TCE and degradation products released in a
spill on their property in 1985. The capture zone for this system was downgradient of the JDF
site and it is reasonable to assume that VOC contaminants migrating into the capture zone from
the JDF also were removed.
Natural attenuation. The term "monitored natural attenuation" refers to the reliance on natural
attenuation processes (within the context of a carefully controlled and monitored site cleanup
approach) to reduce the concentration of contaminants in order to restore groundwater quality
within a timeframe that is reasonable compared to other methods. There are several different
physical, chemical, and biological processes that can contribute to natural attenuation, including
biodegradation, dispersion, dilution, sorption, volatilization, and chemical or biological
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stabilization, transformation or destruction of contaminants.
Natural attenuation is effectively reducing the concentration and the mass of contaminants at the
JDF site. The predominant natural attenuation process in this setting is likely biodegradation.
Three lines of evidence supports the presence of natural attenuation at this site:
(i) Stable to receding plume conditions.
For example, the overall size and concentration of the total chlorinated ethene (TCE. PCE
and 1,2-DCE) contaminant plume decreased significantly between 1988 and 1993. Since
no active groundwater remedial action had been implemented prior to July 1993. when
groundwater extraction was initiated at Parker Pen, the reduction in total chlorinated
ethene concentrations from July 1988 to April 1993 is attributable to natural attenuation
processes.
(ii) Decreasing concentrations along flow paths.
For example, in March 1997, groundwater flowing from beneath the Ash Beds at
monitoring well W5 contained 47 ug/1 PCE and 7 ug/1 TCE. but by the time it reaches
well W6 near the Rock River, the concentrations have decreased to 27 ug/1 PCE and no
TCE was detected.
(iii) The presence of redox and geochemical indicators of biodegradation.
For example, increasing concentrations of iron (Fe2+) and manganese (Mn2-i-) oxides
exist in groundwater immediately downgradient of the Ash Beds and the landfills (an
indicator of biodegradation), but are not present further downgradient along groundwater
flow lines as conditions become oxidized. Under these oxidizing conditions closer to the
river, other metals, such as arsenic, are co-precipitated with the iron and manganese and
no longer present in the groundwater.
Each of these lines of evidence is discussed in detail as it relates to the JDF site in the report
"Petition for Eliminating Groundwater Pump and Treat System" referenced above, which is in
the Administrative Record for this site.
Currently, only PCE and TCE exceed the federal primary drinking water standards (primary
MCLs) at the site. Arsenic and barium continue to exceed the PALs, although levels are below
the primary MCLs and the ESs. There are no primary MCLs (which are health-based drinking
water standards) for iron and manganese, although the levels of both continue to exceed
unenforceable secondary MCLs and State public welfare standards. The arsenic, barium, iron,
and manganese levels are likely elevated due to their release into groundwater from the aquifer
sands during biodegradation of the remaining organics.
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Based on extrapolations from current rates of reduction in contaminants, it is likely to take
approximately 9 years for TCE and PCE in groundwater to reach the drinking water standards, as
expressed by the primary MCLs. and an additional 15 years to reach PALs. Due to the low
concentrations of contaminants, an active extraction and treatment system is unlikely to
significantly speed up this time. The Feasibility Study for the site estimated that it would take at
least 20 years of groundwater extraction and treatment to reach cleanup levels. Concentrations
of iron, manganese, and arsenic are expected to require more time than TCE and PCE to reach
drinking water standards, due to their release into groundwater from biodegradation of organics.
which will continue whether or not groundwater is extracted and treated.
Ground water is not currently being used downgradient of the JDF and is unlikely to be used in
the future due to the availability of city water and a local ordinance prohibiting wells in this area.
A few side-gradient residential wells are in use; however, recent re-testing has confirmed that
they are not impacted by the JDF. A conservative risk analysis shows that excess cancer risk
associated with a possible impact to indoor rir in the downgradient homes from the TCE and
PCE present in the groundwater (for example in basements overlying the plume) is between 1 x
10'6 and 6 x 10"8, an extremely low risk which would not justify extraction and treatment of
groundwater.
Monitored natural attenuation has several additional advantages over groundwater extraction and
treatment at the JDF site, including:
* Less generation or transfer of remediation wastes;
* Less intrusive surface structures are required;
* Cost savings of approximately $1.4 million, calculated as the 30 year present
worth cost.
U.S. EPA has therefore determined (i) that the installation of groundwater extraction and
treatment systems is not necessary to achieve regulatory requirements and to protect public
health and the environment, and (ii) that these goals can better be achieved by natural
attenuation of groundwater contaminants. Monitored natural attenuation meets all relevant
remedy selection criteria, will be fully protective of human health and the environment, and will
meet site objectives within a reasonable time period. Groundwater monitoring will continue and
U.S. EPA will periodically review monitoring data to assess whether groundwater is making
progress toward cleanup standards.
In commenting on the Record of Decision in 1989, the Rock County Health Department
commented that if money is to be spent on groundwater remediation, the JDF site was not their
top priority. Some members of the public were concerned that the proposed treatment method
would transfer contaminants to air. Many commentors indicated that they did not think
groundwater extraction and treatment was cost effective at this site and preferred that the site be
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monitored first to see if it was necessary. In effect, this is wha' has beer done.
IV. Support Agency Comments
The WDNR indicated in a letter dated August 22. 1997 that it concurs with this ESD and has no
comments.
V. Public Comments
U.S. EPA issued a mailing and published a notice of a public comment period for this proposed
remedy change. The comment period began August 15, 1997 and ended August 29, 1997. U.S.
EPA also offered to hold a public meeting to discuss the proposed changes, but no requests for
this meeting were made and the meeting was canceled. U.S. EPA received comments only from
the PRP Group. A response to these comments is attached to this ESD. U.S. EPA also received
a concurrence letter from the WDNR during the comment period.
VI. Affirmation of Statutory Determination
U.S. EPA has determined that the selected remedy, with the change described above, will be
protective of human health and the environment, will comply with federal and State requirements
that are applicable or relevant and appropriate to this remedial action, and will be cost-effective.
In addition, the revised remedy utilizes permanent solutions and alternative treatment
technologies to the maximum extent practicable for this Site. Upon careful scrutiny of the
suggested change and the information submitted to support this change, U.S. EPA, therefore, has
changed the remedy set out in the ROD in the manner described above.
William E. Muno, Director Date
Superfund Division
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Responsiveness Summary for
Explanation of Significant Difference
Janesville Disposal Facility
(Janesville Old Landfill and Janesville Ash Beds Superfund Sites)
Janesville. Wisconsin
Two comment letters were received during the public comment period, from the State of Wisconsin
and from the Janesville Disposal Facility Potentially Responsible Party (PRP) Group.
In a letter dated August 22. 1997. the Wisconsin Department of Natural Resources stated that they
agree that groundwater quality has improved downgradient of these sites and that a groundwater
extraction and treatment system is no longer necessary. They concur with U.S. EPA's Explanation
of Significant Difference (ESD).
In a letter dated August 20, 1997, the PRP Group stated that they are also is in agreement with the
ESD. but suggest the following changes:
Comment 1: Page 2. Section II. first paragraph, line 2, change "1950" to "1952".
Response: U.S. EPA has made this correction.
Comment 2: Page 3, Section III, first paragraph, last sentence, delete and substitute: "U.S. EPA
believes that the data summaries included in the Petition are accurate and is in general agreement
with the technical information contained in the Petition."
Response: The sentence has been revised to read "While not necessarily endorsing all conclusions
stated in the Petition, U.S. EPA believes that the data summaries included in the Petition are accurate
and is in general agreement with the technical information contained in the Petition." U.S. EPA does
not mean to imply that there are particular conclusions with which it disagrees; the statement is
meant as a general disclaimer because the report was not authored by U.S. EPA.
Comment 3: Page 4, Section III, Remedial Actions, line 3, after "incorporation", insert "in the 1985
site".
Response: U.S. EPA has made this correction; however, we have referred to the landfill as the "New
Landfill" rather than the "1985 site" to be consistent with the Record of Decision.
Comment 4: Page 4, Section III, Private groundwater treatment system, line 1, delete "From 1990
to" and insert "During".
Response: U.S. EPA has made this correction.
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