United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
Superfund
Record of Dec'ision:
&EPA
Mason County Landfill, MI
'"
PB94-964119
1I/liR/IID IDI am IIDI IIil Dill ""' "III ""I IIill"
EPAIRODIROS-931241
September 1993
PB94-964119
-
EP A Report Collection
Information Resource Center
US EP A Region 3 .
Philadelphia, PA 19107
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REPORTDOCUMENTA~ON T 1. REPORT NO. 2. 3. Recipient's Accession No.
PAGE EPA/ROD/R05-93/241
4. Title and Subtitle 5. Report Date
SUPERFUND RECORD OF DECISION 09/27/93
Mason County Landfill, MI 6.
Second Remedial Action - Final
7. Author(s) 8. Performing Organization Rept. No.
9. Performing Organization Name and Address 10 Project TaskIWork Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
12. Sponsoring Organization Name and Address 13. Type of Report & Period Covered
U.S. Environmental Protection Agency
401 M Street, S.W. 800/800
Washington, D.C. 20460 14.
15. Supplementary Notes
PB94-964l19
16. Abstract (Limit: 200 words)
The 18-acre Mason County Landfill site is an inactive, sanitary landfill located in
Pere Marquette Township, Mason County; Michigan. Land use in the area is predominantly
rural, with a wetlands area, woodlands, and orchard areas located to the southwest,
east, and south of the site, respectively. Surface water in the site area includes I.ris
Creek, which discharges into Pere Marquette River and, subsequently, into Lake
Michigan. The estimated 1,112 people who reside withiI1 three miles of the site use a
municipal water supply to obtain their drinking water. In addition, there are 14
residential wells located within a half-mile radius of. the landfill. Beginning in 1972,
Acme Disposal operated the landfill, under contract with the State, until it reached
capacity and was closed in 1978. Disposal at the landfill included slurry and sludge
waste from local industries. In 1981, Mason County purchased the property as part of
the settlement of a suit filed by the property's owner. Public concerns over water
quality in nearby Iris Creek prompted the State to review closure activities.
Beginning in 1982, several State and EPA investigations indicated VOC contamination in
ground water' samples. In 1984 and 1985, the State implemented improvements to the
landfill, which included the construction of a clay cap, berms, storm drains, two
surface aerators, and 15 gas vents. A 1988 interim ROD addressed the contaminant
(See Attached. Page)
17. Document Analysis a. Descriptors
Record of becision - Mason County Landfill, MI
Second Remedial Action - Final
Contaminated Medium: None
Key Contaminants: None
b. Identifiers/Open-Ended Terms
c. ceSATI Field/Group
18. Availability Statement 19. Security Class (This Report) 21. No. of Pages
None 30
20. Security Class (This Page) 22. Price
None
50272-101
(See ANSI.Z39.18)
SBelnstructions on Reverse
OPTIONAL FORM 272 (4.77)
(Formerly NTIS-35)
Department of Commerce
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EPA/ROD/R05-93/241
Mason County Landfill, MI
Second Remedial Action - Final
Abstract (Continued)
source areas and required installation of a RCRA compliant soil/clay cap and four new
monitoring wells, ground water monitoring, and implementation of institutional controls,
including deed restrictions. In late 1991, dedicated submersible pumps were installed in
each monitoring well. This ROD addresses the onsite ground water contamination, as OU2.
EPA investigations indicated that previous remedial actions and natural processes
significantly have reduced the onsite contamination to acceptable levels. As a result,
EPA determined that no further action is necessary to protect human health and the
environment; therefore, there are no contaminants of concern affecting this site.
The selected remedial action for this site is no further action, with long-term ground
water, and sediment monitoring for up to 30 years. This remedial action will allow for
further assessment of the effectiveness of the clay cap in reducing the amount of
contamination reaching ground water. The estimated present worth O&M cost for this
remedial action is $500,000 for 30 years.
PERFORMANCE STANDARDS.OR GOALS:
Not applicable.
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DECLARA TION FOR THE RECORD OF DECISION
SITE NAME AND LOCA nON
Mason County Landfill. Ludington. Michigan
STA~ BASIS
This decision document presents the selected remedial action for the Mason County Landf1ll.
in Ludington, Michigan, which was chosen in accordance with the Comprehensive
Environmental Response. Compensation. and Liability Act of 1980 (CERCLA), as amended
by the Superfund Amendments and Reauthorization Act of 1986 (SARA). and. to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP).
This decision is based on the administrative record for the site.
The State of Michigan does not concur with this Record of Decision.
. DESCRIPTION OF THE SELECTED REMEDY
The United States Environmental Protection Agency (EPA) has selected "No Action with
Monitoring"
DECLARATION
EP A has determined that no further remedial action is necessary at this site. Therefore, the
site now qualifies for inclusion in the" sites awaiting deletion" subcategory of the
Construction Completion category of the National Priorities List.
As this is a decision for "No Action", the statutory requirements of CERCLA Section 121
for remedial actions are not applicable and no five year review will be undenaken, although
a five year review will be performed at this site due to the previous Record of Decision
which required upgrading the clay cap for the landfill.
~/.;7A)
DATE
:11;14 t&u/
A: - Valdas V. Adamkus
/ . "'Regional Administrator
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DECISION SUMMARY
1. Site Name. Location. and Description
The Mason County Landfill Site is located three miles south of the City of Ludington and
one mile east of Lake Michigan (see Figures 1 and 2). The Site occupies approximately
eighteen acres of a predominantly rural area in Pere Marquette Township; approximately ten
acres of the Site is landfilled.
Ludington. Michigan has a population of about 9.500. The population of Mason County was
estimated at 26.400 based 'on the 1980 census. The population within a three mile radius of
the Site was estimated at 1.112.
As Figure 3 indicates. just nonh of the Site is heavily wooded and orchards are located to
the east and south of the Site. The local topography varies from relatively level upland areas
south and east of the landfill to steep valleys nonh of the landfill. Figure 3 shows both the
1990 topography and Site topography before landfilling began in 1971. Comparison of the
topographic contours indicates that an estimated 140.000 cubic yards (+/20.000 cubic yards)
of fill is buried in the landfill. The landfill is generally a valley fill with a maximum depth
estimated to be 40 to 50 feet.
Surface waters in the Site area are Iris Creek, the Pere Marquette River, Pere Marquette
Lake, and Lake Michigan (see Figure 2). The headwaters of Iris Creek are located less than
500 feet from the landfill and consist of a wet, marshy area southwest of Babbin Road (see
Figure 3). Water from the marshy area drains into Babbin Pond, which discharges directly
into Iris Creek. Iris Creek discharges into Pere Marquette River. which discharges into Lake
Michigan. A pumped-storage power reservoir operated by Consumers Power Company is
located approximately one half mile south of the Site.
Lake Michigan is the main drinking water source in the area and is the City of Ludington's
water supply. In rural Pere Marquette Township, residents generally depend on small
domestic wells screened in sand and gravel aquifers for potabLe water supplies. There are
founeen residential wells within about a half mile radius of the landfill that vary in depth
from 30 to 150 feet below ground surface (bgs).
Other water uses in the area include Large capacity wells that produce salt brine for industrial
use. A salt brine well about 1,000 feet west of the landfill is screened in an aquifer at a
depth of 450 feet bgs. The brine aquifer is separated from the overlying aquifers used for
potable water by more than 300 feet of low permeability glacial till.
Mason County is underlain by bedrock formations at depths from 300 to 700 feet.
Mississippi Age Coldwater Shale lies beneath the landfill Site at a depth of 650 feet. The
formation is predominantly shale with occasional interbeds of sandstone and limestone.
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~RANT
HAMLIN
31
VICTORV
~KE MICHIGAN
MASON COUNTY
LANO"LL.SITE
"AI MARaUETTE
TOWNSH"
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MASON
COUNTY
IOUNOARV .
KEY TO COUNTIES
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FIGURE 1
LOCATlON MAP
MASON COUNTY LANOFILL RI
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SOURCE; U.S.G.S 7.S' TOPOGRAPHIC MAP
OF LUDINGTON. MICHIGAN QUADRANGLE.
@
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SCALE IN FEET
FIGURE 2
VICINITY MAP
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1~ ~ FROM 1971 TOPOGRAPHIC MAP PROVIDED
,,- FOR ACME DISPOSAL
a
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I
SCALE IN FEET
----- APPROXIMATE LANDFILL BOUNDARY
SOURCE: MASON Co. DPW
CONTDURINTERVAL-25FEET
FIGURE 3
SITE MAP WITH ORIGIN
SITE TOPOGRAPHY
MASON COUNTY LANDFI LL RI,
NOTE: ADProaim8t8 I.ndfill ~-ry b8I8d on Maon COuntY
~. -: ~ --:- - -, DM"",1KOO8ftV d81ciD11On.
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-------
.,
Three or four subsurface till have been recognized in the immediate Site vicinity. The upper
three tills are relatively thin an~ are separated by thick outWash deposits. A conceptual
model of the regional geology near the Mason County Landfill is depicted in Figure 4.
II. Site History and Enforcement Activities
A. Site History
The Site property was originally owned by Edward Dains when it was selected for use as a
sanitary landfill by the Mason County Department of Public Works (DPW). In 1971. Mason
County DPW leased the property from Mr. Dains and subsequently entered into an
agreement with Acme Disposal to operate the landfill. Mr. Dains was hired bv Acme
Disposal as a sanitation Engineer to oversee the daily operations of the landfill" from 1972
until 1978. The Michigan Depanment of Public Health (MDPH) approved Acme's Solid
Waste Disposal Area license in 1971 with the stipulations that no refuse be disposed of below
the 710 foot elevation mean sea level. that the final cover contain at least twenty-percent
clay, and that monitoring wells be installed. The original Site topography is in Figure 3. In
1973. landfill licensing and oversite were transferred from the MDPH to the Michigan
Depanment of Natural Resources (MDNR). The MDNR documented that the slurry and
slLidge wastes from local industries. were being dumped at the landfill. allowed to dry, and
then covered. The Site's license was renewed annually through 1977; it was closed in
August 1978 when it reached capacity. Public concerns over the water quality in nearby Iris
Creek prompted the Mason County DPW and the MDNR to review closure activities.
In 1981, two property owners filed suit against Mason County. One. a neighbor. alleged
that the landfill run off had damaged property and deteriorated the groundwater quality,
while the other. the owner of the landfill property. alleged there had been a breach of
contract regarding the property lease agreement with the Mason County DPW. As part of
the settlement with both parties. Mason County purchased both properties and is currently the
owner of the landfill property.
In 1983, the Mason County DPW received a grant from the State of Michigan for
improvements to the landfill. A .clay cap was completed and berms and storm drains were
constructed to improve Site drainage (Figure 5). Two surface aerators were installed in
Babbin Pond to help aerate the pond and facilitate biodegradation of organic matter. Fifteen
gas vents were placed into the top of the landfill.
B. Past Studies
Site studies and investigations. previous to the formal EP A Remedial Investigations at the
Mason County Landfill, began in 1971 with a preliminary evaluation of the landfill Site and
have continued through the Site closure work completed by the Mason County DPW in 1984-
85. The EPA Field Investigation Team (FIT) inspected the landfill Site in May 1982,
sampling and analyzing the existing monitoring wells. After the FIT data was evaluated the
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FIGURE
4
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3
Site was assigned a ranking system score of 34.18. a score high enough to qualify it for
inclusion on the National Priority List (NFL). This score was given because of the presence
in groundwater of ethyl-benzene. pentachlorophenol. trichloroethene. 1.: trans-
dichloroethene. and 1. I-dichloroethene and the associated toxicity and persistence of these
compounds. The Site was put on the tinal NFL in 1982.
The MDPH replaced S. Dains's and May's residential wells (see Figure 5) in September
1987 because of health risks identified by MDPH sampling done in the fall of 1986.
S. Dains's old well. approximately 400 feet from the landfill and screened at a depth of 130
feet. was replaced by a well 348 feet deep. The well was replaced because of the presence
of 2-butanone and 4 methyl-2-pentanone. May's old well located approximately 1.200 feet
nonh of the landfill and screened at a depth of 60 feet. was replaced by a well 218 feet deep.
The old May well was replaced because of the presence of trace concentration of
tetrachloroethane. In 1990 Mason County purchased the S. Dain's property.
A Remedial Investigation (RI) at the Site was conducted by the EP A through the use of its
contractor. CH2MHill. The RI consisted of two phases or sampling events. Phase I of the
RI fieldwork was conducted from September to November 1986 and Phase II was conducted
between October 1987 and January 1988.
The RI at the Site included the following:
1. Review, and evaluation of past investigations as well as historical practices and other
records relating to the Site. (RI Phase-I)
2. Extensive aquifer sampling and water level measurementS (in both the upper and lower
aquifers) to determine groundwater quality, flow directions
3. An electromagnetic geophysical survey was conducted to evaluate whether existing landtill
monitoring wells were properly- positioned to interpret potential plumes originating from the
Site. (RI Phase I)
4. Samples were collected within the wetland. Babbin Pond, and Iris Creek to define the
Site's effect on the surface waters and sediment. The base flow in Iris Creek was determined
to help estimate groundwater discharge rates into the creek. (RI Phase I and II)
5. Soil borings and the gama logging of existing monitoring wells was conducted to help
define the geology of the Site. (RI Phase-I and II)
6.The Site's gas ventS and ambient air was sampled to determine the Site's impact on air
quality. (RI Phase I and II)
7. Surface soil samples were taken to determine if erosion along the northern side of the Site
presentS a pathway of contaminant migration. (RI Phase II)
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~OAO
1"""1 MAY OS
I...J RESIDENCE
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I.EGEND
GROUND CONTOUR
------
APPROXIMATE lANDFilL BOUNDARY
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SURFACE WATER INTERCEPTION BERM
.----4
BURIED 10.. PLASTIC DRAIN PIPE WITH INLET AND OUTLET
o
.
SCAI.E IN FEE
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BURIED 24.' CRAIN PIPE WITH TWO MANHOLES
= IIID.mar...
DRAINAGE SWALE
FIGURE 5
SITE IMPROVEMI
'"' c , C\o., "".n , at
CLA Y CAP
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~
The results of the RI are detailed in the RI Repon (July 1988). The Site Feasibility Study (FS)
was completed in July 1988. The FS documents in detail the development and evaluation of an
array of remedial action alternatives for the Mason County Landfill Site. A summary of the
physical and chemical characteristics of the Site from the Phase I and II investigation are
discussed below.
The upper aquifer - Thineen monitoring wells and four residential wells were screened in the
upper aquifer at the time of the study. Founeen volatile organic compounds (VOCs) and ten
semi-volatile organic compounds CSVOCs) were detected in the tive downgradient monitoring
wells within 400 feet of the landfill.
In general, the target compound list (TCL) or priority pollutant compounds that can be attributed
to the landfill were predominantly VOCs. Six chlorinated volatile hydrocarbons were detected
in at least one phase of the remedial investigation at concentrations ranging from 1 to 59 pans
per billion (ppb). The highest concentration (59 ppb of l,l-dichloroethene) was detected at
MWl, during Phase I (refer to Figure 8 for all residential and monitoring well locations). 1,1-
dichlorothene was not detected in Phase II, and only chloroethane, l,l-dichloroethane, and
tetrachloroethane were detected in both Phase I and Phase II. Benzene, ethylbenzene, xylene.
2- butanone, and 4-methyl-2-pentanone were found in both phases in concentrations ranging from
2 to 300 ppb. Toluene and 2-hexanone were detected only during Phase I at MW1 with
concentrations of 75 and 19 ppb, respectively.
The concentrations of iron, manganese, and sodium were at least one order-of-magnitude above
upgradient levels in MWl, MW3, and MW7 for both investigative phases. These wells are
located within 400 feet of the landfill.
The lower aquifer - Seven monitoring wells and seven residential wells are screened in the lower
aquifer in Phase I. no TCL organic contaminants were detected in the three residential wells and
therefore these wells were not sampled in Phase II. During Phase I. five VOCs and three
SVOCs were detected in RW06. The State of Michigan replaced RW06 (screened at about 130
feet below ground surface) with a new well screened at about 365 feet, and no TCL organic
contaminants were detected in that new well during Phase II. RWIO was also replaced between
Phase I and Phase II. That well and all other residential wells screened in the lower aquifer did
not contain organic contaminants.
Trace concentrations of five VOCs were detected in two of the three monitoring wells located
along Inman Road. Benzene and tetrachloroethene were detected in MC3D and MC4D at
concentrations of 2 ppb and 1 ppb, respectively. The other compounds detected in at least one
of these wells are 1,1-dichloroethane (1 ppb), 1,2-dichloroethene (2 ppb), and trichloroethene
(1 ppb). These results suggested that Site-related organic contaminants are being transponed
into the lower aquifer.
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5
Manganese was detected at levels one order-oi-magnitUde greater than upgradient levels in
MC4D and RW06 (Phase I). This is consistent with organic data indicating that
contaminants are migrating to the lower aquifer.
. C. Current Site Status
A Resource Conservation and Recovery Act (RCRA) subtitle C compliant soil/clay cap as
directed by the September 1989 interim ROD for the landfill operable contents (disposed
refuse), began construction on November 13. 1990 and was completed September 23, 1991
by Mason County. Institutional controls along with deed restrictions were enacted in late
1991 at the Site by Mason County. Groundwater monitoring (Phase Ill) for the site began
October 9, 1989 and semi-annual sampling has been performed by EPA since that time.
During the week of October 18, 1991. Mason County installed four new monitoring wells at
the site. The new wells are numbered 22 through 25 and are located on the nonh side of the
landfill. (see Figure 8). Monitoring well 23 was screened in the deep aquifer. and all other
wells were screened in the shallow aquifer. Dedicated submersible pumps were installed in
each monitoring well in November 1991.
D. CERCLA Enforcement
Notice letters informing potentially responsible parties (PRPS) of their potential liabilities and
offering them the opponunity to perform the RIlFS were mailed via cenified mail in August of
1985 to six PRPS, including the Site's owners, operators and waste generators. On September
6, 1985, the EPA decided to use Federal funds to conduct the RIlFS due to the PRPs refusal to
participate. The EP A, contracted with CH2M Hill to conduct the RIfFS under contract number
68-01-7251, work assignment number 0065LE3.0.
Negotiations for the remedial design/remedial action (RD/RA) with the PRPs were conducted but
no settlement was reached. On April 10, 1989 a Unilateral Administrative Order pursuant to 106
of CERCLA was issued to Mason County to perform the RD/RA for the clay cap. On April
24,1991, a complaint was filed by the Department of Justice against Straits Steel and Wire and
was later amended to include Citation Walther for past costs associated with the project. The
litigation is currently on-going.
In. Highlights of Community Participation
A RIfFS public hearing was held on November 13, 1986 to inform the local residents of the
Superfund process and the work to be conducted under the Rl. No major issues were raised by
the community at this meeting.
An information repository has .been established at the Ludington Library, at 217 E. Ludington in
Ludington, Michigan. According to Section (113)(k)(I) of CERCLA, the Administrative Record
is available to the public at the Ludington Library.
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6
The draft FS and the interim action Proposed Plan were available for public comment from
August 8. 1988 to August 31. 1988. A public meeting was held on August 17. 1988 to present
the interim action Proposed Plan and FS. Comments received during that Public comment period
and the U.S. EPA's responses are included in the Responsiveness Summary of the interim ROD.
A fact sheet informing the community that the landfill cap construction was expected to begin and
explaining the on-going monitoring program at the.Site was distributed in December of 1990. The
Proposed Plan for the final action at the Site was released to the public on August 6. 1993. The
Technical Memorandums. 1 through 7 upon which this decision is based, were made available in
both the Administrative Record and the information repository.
Apublic comment period was held from August 9 through September 7, 1993. A public meeting
was held on August 25, 1993 to present the results of the technical memorandums and the
preferred alternative as presented in the Proposed Plan for this final action. All significant
comments which were received by EP A prior to the end of the public comment period. including
those expressed verbally at the public meeting, are addressed in the Responsiveness Summary,
which is attached to this Record of Decision. The provisions of Sections l13(k)(2)(i-v) and 117
of CERCLA have been satisfied.
IV. Scope of Response Action
The Mason County Landfill Site has been divided into two operable units: one to control the
contaminant source areas, which was addressed in the September 1988 interim ROD which
required construction of a RCRA compliant subtitle C clay cap, and the groundwater. The interim
ROD also required continued monitoring and to evaluate the effect of the clay cap on the
groundwater prior to and after construction. Residential and monitoring well results after
construction of the clay cap for three rounds of sampling shows a decrease in the contamination
observed from sampling prior to construction of .the clay cap. This decision addresses the
groundwater operable unit. The selection of No Action with long term monitoring will allow
further evaluation the clay cap's effect on the groundwater and ensure risk to human health
remains protective.
V. Summary of Site Characteristics
The 1988 ROD required further monitoring for the groundwater operable unit. EPA began semi-
annual sampling in October 1989 and the last sampling round was completed May 1993
(Round 8). Round 7 results, conducted October 1992 are the most recent results available when
the proposed plan was written. The nature and the extent of contamination for Samp~ing Rounds
1 through 7 are presented in Technical Memorandums, Phase III, Rounds 1 through 7 and
summarized in the following sections.
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7
A. Hydrogeologic Characteristics
Two aquifers have been identified at the Site. The potentiometric suriaces or the upper and lower
aquifers were determined using water level measurementS taken in D~ember 1987 (Figures 6 and
7). The hydraulic gradientS and hydraulic conductivities or each aquifer are summarized as
follows:
Hydraulic Conductivity (cm/s)
Hydraulic Gradient (ftlft)
Range
Logarithmic
Average
Range
Upper Aquifer 5.0 x 10"-
to 8.7 x 1003
2.5 X 10-3
0.040 to 0.064
lower Aquifer 6.1 x 1003
to 2.4 X 10-3
4.4 X 1003
0.018 to 0.310
The upper aquifer is unconfined and possibly perched above the subsurface till unitS as evidenced
by large head differentials betWeen the two aquifers. The till units are thin and possibly
discontinuous on the north side of the landfill. The outwash depositS overlying the till unitS have
interlayered seams of silt andlor clay. The tills and clay/silt seams retard groundwater flow from
the upper aquifer to the lower aquifer. This subsurface condition combined with recharge
(including potential recharge from the nearby pump-storage reservoir) could produce perched
conditions. .
Water from the upper aquifer percolates downward to recharge the lower aquifer. Downward
percolation is controlled by the thickness and permeability of the intervening till unitS and
clay/silt seams. There may be areas where the intervening layers are missing, which would allow
a larger quantity of water to percolate downward to the lower aquifer. Groundwater in the upper
aquifer flows generally to the northwest and discharges into the wetlands, Babbin Pond and Iris
Creek (see Figure. 6). Water level measurementS during Phase lIT, Rounds 3,4,5 and 6 had
shown the upper aquifer to have a north to northeast component.
In the lower aquifer both confined and unconfined conditions exist. The potentiometric surface
in the low~ aquifer is higher than the till unit along Inman Road, indicating a confined condition.
East and south of the landfill, a 20 to 40-foot thick unsaturated zone of sand lies betWeen the
water surface in the lower aquifer and the till unit, indicating an unconfined condition.
Groundwater flow in the lower aquifer trends toward the northwest (see Figure 7) and eventually
discharges to the Pere Marquette Lake and River and Lake Michigan. According to well logs
from local brine wells owned and operated by Dow Chemical, the aquifer is underlain by a
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FIGURE 6
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FIGURE 7
LOWER AQUIFER
POTENTIOMETRIC SURFACI
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AL TERN A l1YE REMEDIAL CON1RACTING S'TRA iEGY
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WORK ASSIGNMENT No. 044-5LE3
JOCUMENT CON'TROL No. 4500- ..u.-AGT,6..
FIGURE
,
LOCATIONS OF MONITORING
ac RESIDENTIAL WElLS
MASON COUNTY LANDFIll.
Ludington. Michigan
1488
-------
. .
8
massive till unit (see Figure 4). The exact thickness 01" the lower aquifer at the Mason Counry
Landfill Site is unknown.
Surface Water - The Site lies within the Pere Marquette River watershed. Surface water units
near the Site include a wetland area at the base of the landfill that discharges to man-made
Babbin Pond, which in turn discharges to Iris Creek. Since no upslope stream feeds the
wetland area, the wetland area fonns the headwaters of Iris Creek.
Iris Creek flows for about one mile through a series of small ponds and eventually discharges to
the Pere Marquette River just west of Highway 31 (see Figure 2).
Surface runoff from the landfill cap discharges directly into Iris Creek. Other surface runoff from
the landfill is channeled to the nonh through riprap lined ditches that lie on the side slopes of the
landfill (see Figure 9).
The wetland area is a local discharge area for groundwater that covers approximately 0.8 acre.
Babbin Pond covers approximately 0.1 acre and contains about 200,000 gallons of water.
B. Residential Wells
Prior to the installation of the upgraded clay cap, low levels (generally 1 to 2 ppb) of one or two
organic chemicals were periodically detected in some of the residential wells, and lead was
detected in two residential wells at concentrations from 2 to 5 ppb, with a maximum detection in
one well of 23 ppb (Table 1). After the landfill cap was repaired and upgraded however, no
organic contaminants were detected in any of the residential wells, and lead was only detected in
the two residential wells in one of three sampling events (Round 6) at concentrations of 4 to 5
ppb. Lead had not been detected in either of these residential wells during the previous round of
sampling, nor was lead detected in subsequent sampling. The levels of lead detected during this
one sampling event are well below the level considered safe for humans to drink (the Action Level
set by EPA under the Safe Drinking Water Act for lead is 15 ppb at the tap), and may be the
result of lead in indoor plumbing rather than contamination from the landfill. In addition, lead
was also detected in shallow and deep wells located upgradient of the landf1l1 (MW-9 and MW-19)
at maximum concentrations of 38 and 52 ppb, and may be the result of naturally occurring
deposits of lead or some source other than the landfill.
c. Monitoring Wells
The results of on-site groundwater monitoring indicate that the landfill cap is effective in reducing
the amount of contamination reaching the groundwater, resulting in a reduction of the number and
levels of chemicals present in groundwater. As illustrated in Table 2, prior to the constrUCtion
of the upgraded cap a variety of chemicals including volatile, semivolatile and inorganic
compounds were detected in several site wells, some at levels exceeding the Maximum
Contaminant Level (MCL) set by U.S. EPA under the Safe Drinking Water Act, (benzene,
antimony, cadmium, chromium, lead and nickel). After the landfill cap was repaired and .
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, BEFORE NEW LANDFILL AFTER NEW LANDFILL
COVER COVER
DETECTED DETECTED
CONCENTRATIONS SAMPLING CONCENTRATIONS SAMPLING
CHEHICAL (ppbJ WELLS ROUND (ppb) HELLS ROUND HCL
VOLATILES (VOCs)
Aceton.e 1 RW-S 4 NO - - *
2-Butanone 3-10 RW-S,6, 3 NO - - *
12
Chloromethane 1-2 RW-4,7 2 NO - - *
Methylene Chloride 1-2 RW-4,5, 4 NO - - *
8,9,10
12
Toluene 1-2 all 3,4 NO - - 1,000
wells
except
RW-11
INORGANICS
, Lead I 2-26 RW,-4, 6, 1,2,3,4 4-5 RW-7,8 6 15
1,8
. -
TABLE 1
CHEMICALS DETECTED IN RESIDENTIAL WELLS
BEFORE AND AFTER NEW LANDFILL COVER
NOTES:
Includes seven rounds of residential well sampling; Rounds 1-4 before new landfill
5-7 after new cover.
MCL is Maximum contaminant Level set by u.s. EPA under Safe Drinking Water Act.
* indicates MCL not available.
ND indicates "Not-Detected".
cover, Rounds
-------
TABLE 2
CHEMICALS DETECTED IN SITE MONITORING WELLS
BEFORE AND AFTER NEW LANDFILL COVER
BEFORE NEW LANDFILL AFTER NEW LANDFILL
COVER COVER :
DETECTED DETECTED MAXIMUM
CONCENTRATIONS CONCENTRATIONS BACKGROUND
CONCENTRATION
CHEMICAL ( ppb) WELLS (ppb) WELLS (ppb) HCL
VOLATILES (VOCs)
Acetone 2 MW-16 ND-6 KW-15 10 *
Benzene 2-14 MW-1,3,7,8 2-12 MW-1,7 4 5
2-Butanone 21 MW-16 ND - ND *
------
Carbon Disulfide 4-180 MW-1,3,4,7, ND - 14 *
8,12,13,14,
15,17,20
Chlorobenzene ND - 1 KW-7 ND *
Chloroethane 2-5 MW-3,7 ND - ND *
Chloroform ND - 10 MW-14 ND 100
Chloromethane ND - 2 MW-7 ND *
--
1,1-Dichloroethane 1-3 MW-3,7,15 ND - 1 *
1,1-Dichloroethene 0.6-2 MW-3,7,1S 2 KW-7 1 7
1,2-Dichloroethane ND - ND - 9 5
1,2-Dichloropropane 2 MW-7 2 KW-7 ND 5
Ethylbenzene 4-120 MW-1,3,7 42-78 KW-7 ND 700
Methylene Chloride ND - 7 KW-lS 2 .
Toluene .. MW-8 ND - ND 1,000
Xylene 3-260 MW-3,4,7 39-120 MW-7 ND 10,000
_.....
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TABLE 2 Con't
CHEMICALS DETECTED IN SITE MONITORING WELLS
BEFORE AND AFTER NEW LANDFILL COVER
-- -
BEFORE NEW LANDFILL AFTER NEW LANDFILL
COVER COVER ;
DETECTED DETECTED MAXIMUM
CONCENTRATIONS CONCENTRATIONS BACKGROUND
CONCENTRATION
CHBHICAL (ppb) WELLS (ppb) WELLS (ppb) HCL
SEMIVOLATILES (SVOCS)
Bis(2-ethylhexyl)phthalate 0.5-180 HW-l,3,4,7, 0.3-79 MW-1,3,15 3,700 *
8,15,16,17,21 17,21,25
Butylbenzlphthalate ND - 1-7 HW-17,25 ND *
4-chloro-3-methylphenol 1 HW-7 1-8 MW-7 ND *
1,4-Dichlorobenzene 1-2 MW-7 0.8-2 MW-7 ND *
2,4-Dimethyphenol 3 HW-7 1-5 MW-7 ND *
Diethylphthalate 0.8-12 MW-3,7 0.4-14 MW-1,3,7, 2 .
16,20
Di-N-Butylphthalate 2 MW-16 0.1-1 MW-1,4,7, 8 *
12,13,14
23,24
Din-octylphthalate ND - 0.6 MW-17 * *
Napthalene 2-4 MW-1,7 0.5-4 MW-1,7 ND *
Phenol 5 MW-l ND - 1 .
INORGANICS
Aluminum 89.5=2,730 all wells 17.28 HW-1 486 *
Antimony 20-28.5 MW-3,4,7,14 ND - 61.4 6
Arsenic 3.7-16 MW-3,7,15 17.1 MW-7 ND 50
Barium 6.3-290 all wells 269 MW-7 835 2,000
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TABLE 2 Con'l
CHEMICALS DETECTED IN SITE MONITORING WELLS
BEFORE AND AFTER NEW LANDFILL COVER
BEFORE NEW LANDFILL AFTER NEW LANDFILL
;
COVER COVER
DETECTED DETECTED MAXIMUM
CONCENTRATIONS CONCENTRATIONS BACKGROUND
CONCENTRATION
CHBHICAL (ppb) WBLLS (ppb) WELLS (ppb) HCL
Cadmium 3.8-6.9 0-8,12,17,21 7.2 0-3 ND 5
chromium 5.6-169 0-17,20,21 10.5-56 MW-23 27.8 100
--
cobalt 12 0-3 ND - ND *
copper 2.1-26.1 MW-3,7,8, 26.1 MW-21 31.7 1,300
16,17,20,
21
Lead 2.1-83.3 0-1,3,8, 3.8-13.2 MW-l,3,8 52.1 15
17,21 20
"----
Manqanese 1.7-2,670 MW-l,3,7,12 1.1-2,680 MW-1,3,7, NO *
13,15,16,21 12,13,16
Mercury NO - 0.24-2.5 MW-1,12, NO 2
13,15,20
21,24
Nickel 17.9-129 MW-17,21 ND - NO 100
--
Silver 4.3 MW-3 12 MW-1 ND *
Vanadium ND - 4-4.8 MW-1,16 ND *
zinc 20.1-6,110 all wells 21. 3-927 HW-1,3,4, 5,030 *
except 7,8,12,16,
M1I-13,17 17,20,21
NOTBS:
Does not 1nclude chem1cals due to laboratory contam1nat1on.
Maximum background concentration from upgradient wells MW-9
MCL is Maximum contaminant Level set by u.s. EPA under Safe
* indicates MCL not available.
NO '--dicates "Not Detected".
and MW-19.
Drinking Water Act.
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.
~
upgraded however. many contaminants were no longer detected in the groundwater. or were only
detected sporadically at limited well locations and at concentrations generally below those
previously detected. Three chemicals. including benzene (MW-7. Round 7), cadmium (MW-3.
Round 6) and mercury (MW-15. Round 7) were detected at concentrations above the MCL.
however these chemicals were not detected consistently in these wells. and were only detected in
one of the last three rounds of sampling.
D. Contaminant Migration
Population areas that could be affected if exposed to contamination migrating from the landfill in
groundwater or from groundwater discharging to the wetland and Iris Creek include residents that
reside nonh of the landfill. Environmental areas include the wetland area. Babbins Pond. and Iris
Creek, nonh of the site. The RI modeled the contaminant load necessary for benzene and xylene
to exceed MCLs at the site boundary. The results of the modeling concluded that extremely large
volumes (in the range of millions of gallons) of pure product would be needed in the landfill to
exceed MCLs at the site boundary for a one time release. The modeling suggests that a constant
and continuous source of 7 x 10,,4 gallons per day of benzene and 2 x 10-) gallons per day of
xylene added to the aquifer over a 6-year period would be required to exceed the MCL at the site
boundary. These results indicate that a slug of contamination (e.g., a drum rupture) is unlikely
to cause an exceedance of MCLs at the site boundary because of the large volume of contaminants
needed.
VI. Summary of Site Risks
A. Human Health Risk
Within the RI, a Risk Assessment chapter detailed a baseline risk assessment that addressed the
potential threats to public health and the environment from the Site associated with the. no action-
alternative for the Site. .
The RI report funher details the baseline assessment for the Site and the baseline indicated the
following major area of concern:
The use of groundwater from wells located between the landfill and Iman Road may result
in adverse health effects. This concern comes from the detection of carcinogens in
monitoring wells at concentrations greater than those associated with a 1 x 10-7 excess
lifetime cancer risk, the presence of noncarcinogens at levels higher than those needed to .
exceed reference dose values, and the presence of two chemicals (benzene and 1, 1- .
dichloroethene, 11 ppb and 59 ppb) at levels that exceed MCLs.
Cancer potency factors (CPFs) have been developed by U.S. EPA's Carcinogenic Assessment
Group for estimating excess lifetime cancer risks associated with exposure to potentially
carcinogenic chemicals. CPFs, which are expressed in units of (mg/kg-dayrl, are multiplied by
the estimated intake of a potential carcinogen, in mg/kg-day, to provide an upper-bound estimate
of the excess lifetime cancer risk associated with exposure at that intake level. The term "upper
bound" reflects the conservative estimate of the risks calculated from the CPF . Use of this
approach makes underestimation of the actual cancer risk highly unlikely. Cancer potency factors
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"
10
. .-
are derived from the results of human epidemioloe:icai studies or chronic animal bioassavs to
which animal-to-human extrapolation and uncenainty factors have been applied. .
Reference doses (RIDs) have been developed by U.S. EPA for indicating the potential for adverse
health effects from exposure to chemicals exhibiting noncarcinogenic effects. RIDs. which are
expressed in units of mgikg-day, are estimates oT lifetime daily exposure levels for humans.
including sensitive individuals. Estimated intakes oT chemicals from environmental mediale.g.,
the amount of a chemical ingested from contaminated drinking water) can be compared to the
RID. RIDs are derived from human epidemiological studies or animal studies to which
uncenainty factors have been applied (e.g., to account for the use of animal data to predict effects
on humans). These uncertainty factors assure that the RIDs will not underestimate the potential
for adverse non carcinogenic effects to occur.
Excess lifetime cancer risks are determined by multiplying the intake level with the cancer potency
factor. These risks are probabilities that are generally expressed in scientific notation
(e.g., IxlO-6). An excess lifetime cancer risk of Ixl
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.
11
B. Ecological Risks
The RI concluded that environmental impacts were limited due to the low levels of contamination
and the shallow creek depth. Chronic water quality criteria was exceeded for iron. lead. and
copper during Phase III. Round 7 sampling in the creek. although due to the lack of fish in the
creek and its shallow nature no ecological risk exists.
VII. Description of Alternatives
In addition to addressing landfill contents. the FS and interim action ROD also identified and
evaluated alternatives to address threats and/or potential threats from contaminated groundwater.
The alternatives that were evaluated to address contaminated groundwater include:
A. Alternative I - No Action, Continue Groundwater Monitoring.
Under this alternative approximately 8 residential wells. and 20 existing on-site groundwater
monitoring wells. would continue to be sampled and analyzed on an annual basis for volatile.
semivolatile and inorganic compounds. Groundwater monitoring would be conducted for up to
30 years to ensure the upgraded landfill cap continues to be effective in reducing the amount of
contamination reaching the groundwater. thus eliminating or continuing to reduce chemical
concentrations in groundwater to an acceptable level, and to monitor the water quality of nearby
residential wells to ensure that residents are not exposed to unacceptable levels of contaminant
concentrations. The estimated cost of this alternative is $0.5 million.
B. Alternative 2 - Groundwater Collection and Treatment
Under this alternative an on-site water treatment plant would be constructed and approximately.
10 extraction wells would be constructed to collect the groundwater. Groundwater treatment
would occur using precipitation and settling tanks, followed by granular activated carbon
adsorption. Sludges that accumulate would be collected. solidified and disposed of at an
appropriate off-site landfill. Treated groundwater would be discharged by pipeline to Iris Creek.
The estimated capital cost for this alternative is $4,270,000 and the O&M cost is $416,000. The
estimated total present worth cost of this alternative is $12,000,000.
VIII. Comparative Analysis of Alternatives
In order to determine the most appropriate alternative for the Mason County site. the alternatives
were evaluated against each other. Comparisons were based on the nine evaluation criteria. The
nine criteria are: 1) overall protection of human health and the environment, 2) compliance with
applicable or relevant and appropriate requirements. 3) long-term effectiveness and permanence,
4) reduction of toxicity, mobility, and volume, through treatment, 5) shon-term effectiveness, 6)
implementability, 7) cost, 8) state acceptance, and 9) community acceptance.
A. Overall Protection of Human Health and the Environment
The long term monitoring described in Alternative I will provide information on whether
contaminant concentrations in groundwater and surface water continue to be within acceptable
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. .
12
human health and environmental standards. The construction of the clay cap minimizes the
amount of infiltration through the landfill contents which decreases contamination migrating into
the shallow aquifer. Thus contamination is being reduced through natural attenuation. As a result
of this natural attenuation. contaminates in the shallow aquifer will be reduced to levels required
by MCLs in a time frame comparable to that which could be achieved through active remediation.
Long term monitoring of the shallow aquifer will provide funher information regarding the
effectiveness of the clay cap.
Alternative 2 would remove contaminants. thereby reducing the risks from ingestion and funher
off-site migration.
B. Compliance With ARARs
Each alternative is evaluated for compliance with ARARS. including chemical specific. action
specific. and location specific ARARS.
Because no remedial action will be performed for Alternative 1. no ARARS are applicable to the
groundwater operable unit. although the following policy will be complied with:
It is the policy of EP A to evaluate the appropriate remediation of groundwater based upon EP A . s
Protectine the Nation's Groundwater. EPA's Strateey forthe 1990's, July, 1991. Pursuant to the
Groundwater Protection Strategy, the groundwater located in both the shallow 'and deep aquifer.
are classified as Class IIA groundwater. At this site, goals for Class ITA groundwater is set at
the Maximum Contaminant Levels (MCLs) under the Federal Safe Drinking Water Act.
The following are ARARs that alternative 2 would comply with: the Clean Water Act for
discharge to Iris Creek and the Clean Air Act and state code MAC R336.1701-.1702 for
discharges to the air; spent treatment residuals if land disposed will comply with treatment
standards of 40 CFR 268.41 and if regenerated, 40 CFR Part 264 Subpart X.
C. Long-Term Effectiveness and Permanence
This evaluation focuses on the results of a remedial action in terms of the risks remaining at the
site after response objectives have been met. The following factors are addressed for each
alternative: magnitude of remaining risk, adequacy and reliability of controls.
Alternative 1 complies with this criteria by controlling the remaining risk through monitoring to
prevent residents from being exposed to unacceptable concentrations in groundwater.
Alternative 2 would slowly remove the contaminated groundwater onsite. Removing a bulk of
the contamination will prevent migration towards the residential wells. It is projected that the
groundwater extraction and treatment may attain the Ground-Water Cleanup Standards within 30
. years or less. However, ground-water quality will need to be evaluated to determine if the
remedial action objectives have been met.
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.
. ,
13
D. Reduction of Toxicity. Mobility. or Volume (TMV) Through Treatment
This .evaluation addresses the statutory preference for selecting remedial actions that employ
treatment technologies which permanently and significantly reduce toxicity. mobility, or volume
of the hazardous substances. This preference is satisfied when treatment is used to reduce the
principal threats at a site through destruction of toxic contaminants. irreversible reduction of
contaminant mobility, or reduction of total volume of contaminated media.
Alternative 1 will not reduce the toxicity, mobility, or volume through treatment although
treatment will occur through natural attenuation. Alternative 2, by removing and treating the
groundwater, will reduce the toxicity and the mobility of the groundwater plume as well as the
volume of the plume.
E. Shon- Term Effectiveness
This evaluation focuses on the effects to human health and the environment which may occur
while the alternative is being implemented and until the remedial objectives are met. The
following factors were used to evaluate the shon term effectiveness of each alternative: protection
of the community during remedial actions, protection of workers during remedial actions,
e,nvironmental impacts from implementation of alternatives, and time until remedial objectives are
met.
Alternative 1 is. expected to protect the community until the goal is met. and is not expected to .
have any effects on workers performing monitoring. Monitoring is. expected for 30 years or until
the goals have been met.
Construction operations associated with Alternative 2 will produce minimal disturbance to the
surrounding community. .
With regard to the time until remedial objectives are met Alternative 2 could be operated for 30
years but will be operated until the remedial objectives are met, which could be substantially less.
With regard to environmental impacts. Alternative 2 may result in a change in groundwater flow
and will have to be monitored so that no adverse impacts result in the wetland nonh of the
landfill.
F. Implementablity
This evaluation addresses the technical and administrative' feasibility of implementing the
alternatives and the availability of the various services and materials required during its
implementation.
Alternative l, monitoring, is well demonstrated and commercially available. Alternative 2 is a
proven technology and is commercially available.
Administratively, none of . the alternatives should pose any problems with regard to
implementation.
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. '
1~
G. Cost
This evaluation examines the estimated costs for implementing the remedial alternatives. Capital
and O&M cost are used to calculate estimated present wonh costs for each alternative.
Alternative 1 has a capital cost of $0 and an O&Mcost of $500.000. Total present wonh is
5500.000. Alternative 2 has a capitol cost of $4.300.000 and an O&M cost of $8.000.000. Total
present wonh cost of $12.000.000.
H. State Acceptance
The State of Michigan does not concur with the selection of Alternative 1. The State's comments
and EP A's responses are included in the responsivene$s summary.
1. Community Acceptance
Commuz:tity response to the alternatives is presented in the responsiveness summary, which
addresses comments received during the public comment period.
IX. The Selected Remedy
After considering the requirements of CERCLA, the detailed analysis of alternatives, and public
comments, EP A has selected Alternative I for the final action at the Mason County Landfill which
consists of continued monitoring for up to 30 years for residential wells. appropriate groundwater
monitoring wells, sediment and surface water.
X. Statutory Determinations
The selected remedy must satisfy the requirements of Section 121(a-e) of CERCLA to:
A. Protect human health and the environment;
B. Comply with ARARs;
C. Be cost-effective;
D. Utilize permanent solutions and alternate treatment technologies to the maximum extent
practicable; and,
E. Satisfy a preference for treatment as a principle element of the remedy.
The implementation of Alternative 1 at the Mason County site satisfies the requirements of
CERCLA as detailed below:
A. Protection of Human Health and the Environment
Implementation of the selected alternative will address potential risks to human health and the
environment by continued monitoring water quality to ensure that residents are not exposed to
contaminated groundwater.
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.
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15
8. Compliance With ARARS
Section 121(d)(2) of CERCLA requires all remedial actions to attain ARARS upon completion of
. the remedial action. Because no remedial action will be perfonned. no ARARS are applicable
to the groundwater operable unit.
8.1 Chemical-specific ARARS
The interim ROD stated that after closure is completed. the substantive monitoring and
maintenance post closure requirementS contained in Section 264.117 through 264.120 of Subpart
G will be conducted.
The above regulation for post-closure requirementS is relevant but not appropriate because the
amount of listed hazardous waste that was disposed of in the landfill is minor in comparison to
the overall waste 1andfilled. Therefore post-closure requirementS will be in accordance with
EP A's Groundwater Protection Strategy.
8.2 Action-specific ARARS
RCRA closure requirementS for landfills with hazardous wastes are outlined in 40 CFR Subpart
G. The interim ROD included this provision as relevant and appropriate and the landfill cap was
upgraded in compliance with RCRA subtitle C requirementS.
C.
Cost-Effectiveness.
The selected remedy provides overall cost-effectiveness. The alternative provides protection
through the use of institutional controls and allows the aquifers to achieve MCLs through natUral
attenuation at a cost significantly less (S500,000 vs. S12.000,(00) than the active groundwater
collection and treatment.
D.
Utilization of Permanent Solutions, Alternative Treatment Technologies to the Extent
Practicable. and Preference for Treatment as a Principal Element.
The selected remedy provides the best balance with respect to the nine evaluation criteria as
described in Section vm. Treatment technologies are not being utilized in this alternative as
treatment has not been delineated to not be appropriate at this site. This alternative provides
protection while being cost-effective.
E.
Preference for Treatment as a Principal Element
The selected remedy does not utilize treatment as a principal element. and. therefore. does not
satisfy the statutory preference for treatment. Groundwater treatment is not. .at this point.
ncn-ss:ary to provide adequate protection of human health and the environment.
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