Urited States
Environmental Pro*cdon
Agency
Office o'
Emergency and
Remedial Response
EPMKXVR03-9
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50272-101
REPORT DOCUMENTATION 11. REPORT NO. 2. 8. Ailclpl8nt'a "-eIon No.
PAGE EPA/ROD/R03-90/098
4. T1tIit IftCI WIcIIIa So AIport D*
SUPERFUND RECORD OF DECISION 09/28/90
Sand, Gravel and Stone, MD
Second Remedial Action a.
7. AuIhor(a) L P8rfonNng Organization Rapt. No.
8. ~ 0rpInIDII0n Name and Addr888 10. PfoIacUTalllWCIItI UnIt No.
11. ~C) or QnnI(G) No.
(C)
(0)
12. Sponaorlnll OrgarUation Name and AddNu 18. Type of AIport , PwtocI Cowracl
U.S. Environmental Protection Agency 800/000
401 M Street, S.W.
Washington, D.C. 20460 14.
1 S. Suppllrnan18ry NotM
.
16. Abatract (Umlt: 2OIIworda)
The 200-acre Sand, Gravel and Stone site is a former sand and gravel quarry three miles
west of the town of Elkton, in Cecil County~ Maryland, along a tributary to Mill Creek.
Surface water in Mill Creek eventually flows to the Elk River and the Chesapeake Bay.
Beginning in 1969, hazardous materials were disposed of on site. In 1974, a pool of
chemical waste burned in a onsite fire, the cause of which has yet to be determined.
Subsequently, 200,000 gallons of this liquid waste was removed to an offsite landfill
and the remaining drums and sludge were buried onsite in two excavated pits (eastern and
western). The site has been separated into three operable units (OU). A 1985 Record of
Decision (ROD) addressed OU1, the remediation of shallow ground water contamination near
the eastern excavated pit, source control (Le., removal of buried drums), and site
access restrictions. This ROD focuses on OU2, the threat posed by soil and ground water
contamination migrating from the eastern portion of the site, including remediation of
ground water contamination in the lower aquifers if needed, and evaluation of.
contaminant sources near the western excavation pit. Soil sampling ana.lyses and
geophysical studies now show that there are no unacceptable risks associated with soil
in the western area of the site. A future ROD will address OU3, the contaminated soil,
,
(See Attached Page) 0'
17. Document Analyala L Daacrlptora
Reco~d of Decision - Sand, Gravel and Stone, MD
Second Remedial Action
Contaminated Medium: gw
Key Contaminants: VOCs (benzene, toluene), metals
b. Idan1IfieralOpan..endad Tarma
c. COSA 11 FIaIcIIGroup
18. AVllllbility SlIlImant 18. Sac:urIty CI... (Thla Report) 21. No. 01 PI",a
None 7"7
I 2D. 8acurIty a.. (nH Page) 22. PrIce
None
:. .17)
(See ANSI _38.18)
s.. hr811uct1- on ~-
(Fonnerty NTlS-35)
Department 01 C-
-------
EPA/ROD/R03-90/098
Sand, Gravel and Stone, MD
Second Remedial Action
Abstract (Continued)
source control, final site closure, and post-closure operation
activities. The primary contaminants of concern affecting the
including benzene and toluene; and metals.
and maintenance
ground water are VOCs,
The selected remedial action for this site includes onsite and offsite ground water
monitoring. . If this monitoring data demonstrate that remediation is required, ground
water may be treated either onsite, or offsite at point of use, and bottled water will
be supplied to affected residences and businesses. The onsite treatment system
installed as a result of the first remedial action would be expanded and modified, as
necessary, to treat the ground water in the lower aquifer. Treatment measures may'
utilize granular activated carbon, air stripping, ion exchange, or any combination of
these techniques. The estimated present worth cost of this remedial action ranges from
$702,000 to $7,125,000, depending on the extent and nature of treatment required, and an
annual O&M cost ranging from $102,000 to $625,900 for 30 years.
PERFORMANCE STANDARDS OR GOALS: Action levels that will trigger theirnplementation of
onsite and/or offsite ground water treatment include concentrations of chemicals of
concern in excess of MCLs, . a cumulative carcinogenic risk in 'excess of 10 -4, or a
non-carcinogenic hazard index greater than 1.0.
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U.8. BBVIROHMBHTAL PROTBCTION AGBNCY - RBGION III
8UJtBUtJIfI) PROGRAM
RECORD OP DBCISION
MARYLAND SAND, GRAVEL AND STONE SITB
OPBRABLE UNIT TWO
BLltTON, MARYLAND
SBPTBKBBR 1"0
-------
I.
II.
III.
IV.
~LB o. COIh'BJl'fS
PAR'!'
DBCLARATION FOR THB RECORD OF DBCISION
DBCISION SUMMARY
RESPONSIVBHBSS StJXKARY
STATB'S LBTTBROF CONCORRBNCB
-------
I.
DECLARATION FOR THE RECORD OP.DECISION
-------
DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Maryland Sand, Gravel & Stone Site
Elkton, Maryland
Operable Unit Two
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for Operable Unit Two at the Maryland Sand, Gravel and Stone Site
("Site") in Elkton, Maryland, chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Liability
Act of 1980 (CERCLA), as amended, and to the extent practicable,
the National Oil and Hazardous Substances Pollution Contingency
Plan. This decision is based on the Administrative Record for
the Site. .
The State of Maryland concurs with the selected remedy.
ASSESSMENT OF THE SITE
Pursuant to duly delegated authority, I hereby determine,
pursuant to Section 106 of CERCLA, 42 U.S.C. S 9606, that actual
or threatened releases of hazardous substances from the Site, as
discussed in "S~mmary of Site Risks" in Section 6.0, if not
addressed by implementing the response action selected in this
Record of Decision may present an imminent and substantial endan-
germent to the public health, welfare, or the environment. .
DESCRIPTION OF THE REMEDY
This operable unit is the second of three operable units for
this Site. Operable Unit One dealt with shallow groundwater
contamination in the Eastern Excavated Area of the Site. The
remedy for Operable Unit One called for treatment of the
contaminated groundwater in a treatment plant that will be built
on the Site. It also provided for source control (i.e., removal
of buried drums) and access restrictions (i.e., a fence was
constructed around the Eastern Excavated Area). Operable Unit
Two, which is the subject of this Record of Decision deals with
groundwater contamination in the lower aquifers and an evaluation
of contaminant sources in the Western Excavated Area. Operable
Unit Three will address contaminated soils, closure, and post-
closure operation and maintenance activities.
The remedy for Operable Unit Two was selected after a
careful evaluation of the overall conditions at the Site. The
soil and groundwater in the uppermost aquifer in the Eastern
Excavated Area of the Site are highly contaminate~ with a variety
-------
of organic and inorganic compounds'- The soil and groundwater in
this area will continue to act as a source until this source is
removed or-controlled, either as part of Operable Unit One or
Operable Unit Three.
The remedy selected for Operable Unit Two addresses the
threat posed by the existing soil and groundwater contamination
in the eastern portion of the site. Although to d~te, the
migration of contamination from the uppermost aquifer appears to
be limited, the selected remedy will put in place a system to
monitor and treat contaminated groundwater that does migrate into
the deeper aquifers or offsite.
The major components of the selected remedy are:
o
Onsite and offsite groundwater monitoring
Onsite and/or offsite point-of-use treatment if .
determined. necessary based on groundwater monitoring
data.
o
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment, complies with Federal and State requirements that
are legally applicable or relevant and appropriate to the
remedial action, and is cost-effective. This remedy utilizes
permanent solutions.and alternative treatment (or resource
recovery) technologies to the maximum extent practicable and
satisfies the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, or volume as a
principal element.
.- -
Until a decision is made with respect to the contaminated
soils under Operable Unit Three, hazardous substances will remain
onsite above health-based levels. A review will therefore be
conducted within five years after commencement of remedial action
in accordance with section 121(c) of CERCLA, 42 U.S.C. ~ 9621(c),
to ensure that the remedy selected for this operable unit
continues to provide adequate protection of human health and the
environment.
~3
Edwin B. Erickson
Regional Administrator
Region III
SEP 2 8 1990
Date
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1.0
1
SITE LOCATION AND DESCRIPTION
1.1
SITE LOCATION
The Maryland Sand, Gravel and Stone site (MSGS site or Site)
is located in Cecil County, Maryland at 75°53'54" longitude and
30°36'53" latitude on the u.S. Geological Survey (USGS) North-
east, Maryland 7.5 minute quadrangle map. Consisting of-about'
200 acres, the Site is located north of Maryland Route 40 along a
tributary to Mill Creek and about 3 miles west of Elkton (Figure
1). It is situated within the western portion of a triangle
formed by Marley Road to the northwest, Nottingham Road to the
northeast, and Maryland Route 40 (Pulaski Highway) to the south
(Figure 2).
1.1 - site Description
The Site was previously operated as a sand and gravel
quarry. Quarrying operations removed materials from two areas:
the Eastern Excavated Area and the Western Excavated Area.
~ About three acres of the Site in the Eastern Excavated Area
-reportedly were used for the disposal of ,waste processing water,
_still bottoms, sludge, and drums of solid and semisolid waste
between 1969 and 1974. Three pits in the Eastern Excavated Area
were used as surface impoundments where about 700,000 gallons of
waste were dumped.
Within a 1 mile radius of the site there are approximately
150 units housing about 570 residents. Elkton, a town of 6,468
residents, is located approximately 3 miles to the east of the
site. The town of North East, located approximately 1.8 miles
west-southwest of the Site, has a population of 1,469.
The geology of the MSGS site consists of fluvial Potomac
Group Sediments that overlie fractured metamorphic bedrock. The
sediments are sand, gravel, silt and clay. The sediments exhibit
marked lateral variations. There do appear, however, to be
several laterally consistent strata across much of the Site.
These include an upper sand unit (primarily restricted to the
Eastern Excavated Area), a middle and a lower sand unit, a zone
of weathered bedrock (saprolite) and bedrock.
."
. The middle and lower sand units currently are used as a
source of drinking water and these units have therefore been
classified as a Class II (a) aquifer. The general direction of
groundwater flow from the Site is south or south-southwest.
There are a number of seeps and springs on the site.
Surface waters from the Site are collected by two intermittent
streams; the western and eastern tributaries of Mill Creek. The
tributaries merge at the southeastern corner of the site. Mill
Creek flows southeastward from the site, turns eastward and then
becomes a tributary of Elk Creek. Elk Creek drains into Elk
. . -
"....' ,..-.,-".,.. -'.':".' ,-;"''':;~'';" ,,'0 '."~' '.
. . '~'- ..,.' '~' -. "',:'". .
. . ~ -. - .
-------
-------
SITEMAP
Figure 2
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4
River and subsequently into the Chesapeake Bay. Recreational use
of the surface water for fishing occurs in both Elk Creek and Elk
River.
2.0
SITB HISTORY AND BHPORCEMENT ACTIONS
Quarrying operations at the site were conducted by the
Maryland Sand, Gravel and Stone Company. Hazardous materials
were disposed of on the Site between 1969 and 1974.
. In April 1974, a fire occurred onsite during which a pool of
chemical waste burned at high intensity before it was extin-
guished. The cause of the fire was not determined. .
Two hundred thousand gallons of liquid waste were removed
from the site in 1974, and taken to the Kin Buc Landfill in .
Edison, New Jersey. The drums and sludges that remained follow-
ing the removal of the liquid waste were buried onsite in exca-
vated pits (refer to Section 4.0 for current status of buried
drums) . .
In July 1979, EPA conducted an initial site investigation.
Additional investigations were conducted by EPA in February 1982.
EPA proposed the Site for inclusion on the National Priorities
List (NPL) in December 1982, and it was added to the list in
September 1984. .
EPA initiated remedial investigation (RI) activities in
June 1984. The Phase I Remedial Investigation/Feasibility Study
(RIfFS), conducted by EPA, was completed in september 1985.
On September 30, 1985, EPA issued a Record of Decision (ROD).
for Operable unit One at the Site. (refer to Section 4.0 for a
discussion of the scope and role of the three operable units
associated with this Site.) In April 1988, forty-one potentially
responsible parties (PRPs) entered into a Consent Decree with EPA
to implement the remedy identified in the ROD for Operable Unit
One. In October 1989, the United States filed an action against
five non-settlors seeking recovery of response costs.
On January 16, 1986, sixteen PRPs entered into a Consent
Order with EPA to perform the RIfFS for Operable Unit Two. 1
Work on the Phase Two RIfFS began in November 1985 and was
completed in May 1990. (Note, hereinafter the terms Operable.
Unit and Phase will be used interchangeably. That is, the Phase
II RIfFS corresponds to the RIfFS for Operable Unit two, etc.)
. Since January 16, 1986, there have been two amendments to
the Consent Order pursuant to which parties were added or dropped
as respondents. The Consent Order ended up with seventeen res-
pondents (Docket No. III-86-2-DC Amended caption and Amended
Caption No.2).
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3.0
5
HIGHLIGHTS O~ COKKUHITY PARTICIPATIOR
The RI/FS and Proposed Plan for Operable Unit Two at the
Maryland Sand, Gravel and stone Site were released to the public
on May 15, 1990. The documents were made available to the public
in both the administrative record and an information repository
maintained at the EPA Docket Room in Region III and at the Cecil
County Public Library. The Notice of availability of these two
documents was published in the Cecil Whig Newspaper on May 15,
1990. The Proposed Plan and administrative record were made
available to the public in accordance with Sections 113 and 117
of CERCLA, 42 U.S.C. S 9613 and 9617 and 40 C.F.R. S 300.430(f),
55 Fed. Bgg. 8850, March 8, 1990.
The public comment period was originally scheduled to run
from May 15, 1990, to June 15, 1990. However, upon request of
some of the PRPs associated with this Site, the comment period
was extended to July 15, 1990, in accordance with 40 C.F.R.. S
300.430(f) (3) (C), 55 Fed. Req. 8851, March 8, 1990.
I
,.
A public meeting was held on June 5, 1990, at 7:00 p.m. in
the Cecil County Public Library. At this meeting a represen-.
tative from EPA discussed conditions at the Site, summarized the
remedial alternatives under consideration and presented EPA's
proposed plan for dealing with Operable Unit Two. Following this
presentation, representatives from EPA and the Maryland
Department of the Environment answered questions about the site
and the alternatives under consideration. A response to the
comments received during the public comment period, including
those received during the public meeting, is included in the.
Responsiveness Summary that is part of this ROD. This decision
document presents the selected remedial action for Operable unit
Two at the Maryland Sand, Gravel and Stone Site in Elkton,
Maryland. The remedy selected was chosen in accordance with
CERCLA, 42 U.S.C. S 9601 et. seq., and to the extent practicable,
the National oil and Hazardous Substances Pollution Contingency
Plan (NCP). The decision for this operable unit is based on the
administrative record.
.' .
4.0
SCOPB AKD ROLB O~ OPBRABLB UNITS
. As with many Superfund sites, the problems at the
Sand, Gravel. and Stone Site are complex. As a result,
divided the work into three operable units. The scope
the operable units can be summarized as follows:
Maryland
EPA has
of each of
Operable Unit One
shallow groundwater contamination in the
Eastern Excavated Area, source control,
access restrictions . .
~ -f :;-,..'
",'. '. .
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6
Operable UDi~ Two
groundwater contamination in the lower
aquifers and evaluation of contaminant
sources in the Western Excavated Area
Operable ODi~ Three
soils, source control, final site
closure, and post closure operation and
maintenance activities.
EPA has already selected the clean-up remedy for Operable
Unit One (refer to September 30, 1985, ROD). The remedy provided
fer the removal of buried material (drums and/or cement mixer
barrels) and offsite disposal of hazardous materials at an
approved RCRA facility. The remedy called for a fence to be
constructed around the most heavily contaminated portions of the
Eastern Excavated Area. It also provided for the installation of
shallow groundwater interceptor trenches downgradient from the
waste sources to collect the contaminated groundwater and" "
leachate for treatment at a treatment plant to be built on the
Site.
Portions of the Operable unit One remedial ~ction have
already been completed. The fence has been installed. Drum
removal work is currently underway, and the treatability study to
determine the location and type of groundwater collection and
treatment systems is also ongoing.
This ROD addresses operable Unit Two at the Site. It
addresses groundwater contamination in the lower "aquifers and the
evaluation of potential contaminant sources in the Western
Excavated Area.
Operable Unit Three will address contaminated soils, closure
and post closure activities. "
5.0
SITB CHARACTBRIZATION
5.1
WESTBRN BXCAVATBD AREA
One of the objectives of the remedial investigation for
Operable Unit Two, was to investigate the possibility" of a
contamination source in the Western Excavated Area. Several
tasks in the remedial investigation were aimed at providing the
information necessary to make a determination as to whether waste
disposal had occurred in the Western Excavated Area.
A geophysical study was conducted in the Western Excavated
Area as well as in the Old Sedimentation Pond. The study did hot
encounter evidence of buried metallic waste or other indications
of contaminant sources in either of these areas.
Analysis of soil samples (0 to 3ft) and shallow borings
(0 to 8ft) taken from the Western Excavated Area also did not
reveal evidence of a contamination source in the Western
Excavated Area. "
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7
Based on a review of the results of geophysical studies,
surface soil sampling and shallow boring analysis conducted in
the Western Excavated Area, it does not appear that waste
disposal occurred in this area. The Risk Assessment summarized
in section 6.0 concluded that there were no unacceptable risks
associated with the Western Excavated Area. Therefore, no .
further investigation nor remedial activity is proposed to deal
with surface contamination in this area. .
Remedial activities associated with groundwater, both on-
.and off-site, including the Western Excavated Area, are discussed
below. Note, however, that wells in the Western Excavated Area
sampled during the Phase II remedial investigation did not
evidence contamination.
5.2
GROtnmWATER
As noted previously, the geology of the MSGS site consists
of fluvial Potomac Group Sediments that overlie fractured
metamorphic bedrock. The sediments are sand, gravel, silt and
clay. The sediments exhibit marked lateral variations. However,
there do appear to be several laterally consistent strata. These
include an upper, middle, and lower sand unit, a zone of
weathered bedrock (saprolite) and bedrock. Figure 3 provides a
representative cross-section of the Site showing the relationship
and relative thickness of the various units. Figure 4 shows the
location of the cross section with respect to the site.
The upper sand unit appears to be restricted to the Eastern
Excavated Area. The highest concentration of contaminants was
found in the groundwater associated with this unit due to the
disposal of wastes immediately above and within this unit.
Contamination in the upper sand unit was characterized in the
Phase I remedial investigation and confirmed in the Phase II
rer.~dial investigation.
The following constituents have been detected in
concentrations exceeding the maximum contaminant level (MCL) in
the upper sand unit: benzene, xylene, 1,2-dichloroethane, vinyl
chloride, toluene, 1, 1, I-trichloroethane, and cadmium. An order
of magnitude increase in the concentrations of volatile organics
in the upper sand monitoring wells was noted between 1985 and
1987 for wells south of Pond 1.
.'
The upper sand unit appears to be perched on a layer of silt
and clay. Groundwater moves from the upper sand unit into the
middle sand unit by way of surface seeps, leakage through the
confining. layer, or possibly by movement thorough undetected gaps
in the confining layer. The Phase I Remedial Investigation
identified three areas of surface seeps, one associated with each
of the three ponds located in the Eastern Excavated Area.
Groundwater in the upper sand unit flows toward these seeps
located west, southwest and southeast of the Eastern Excavated
Area.
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A'
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ItO
i ao
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Figure 3
CROSS SECTION A-A' SHOWifU
GRCMWOWATF R IWMTt
-------
Figure 4
LOCATION Of CIMMMf CTMH
-------
10
The water table aquifer in the middle sand unit south of the
Eastern Excavated Area and along the valley of the western
tributary to Mill Creek is underlain by a separate silt and clay
layer. Groundwater moves downward from the middle sand unit by
leakage through this confining bed, and through gaps in the
confining bed. Gaps in the confining layer were observed at
wells SMW-IO and D&M 14. The location of on-site monitoring
wells is shown on Figure 5. The direction of groundwater flow in
the middle sand unit is generally southward.
" Contaminant levels in the middle sand groundwater unit
generally were considerably lower than in the upper sand unit.
However, elevated levels of contamination were detected in middle
sand well DMW-7 which is located immediately downgradient of the
Eastern Excavated Area. Twelve organic compounds were detected
in the well. Five of these were detected in concentrations at or
exceeding MCL's. They include: vinyl chloride, benzene, tri-
chloroethene, 1,1-dichloroethene, and l,l,l-trichloroethane.
There was a significant increase in both the number and
concentration of contaminants found in this well "between 1985 and
1988. This increase likely represents migration of contaminants
into the groundwater in the area of DMW-7. No elevated levels of
metals were found in the middle sand wells. A summary of the
occurrence of analytes associated with groundwater from the
middle sand unit is provided in Table 1.
Few contaminants were found in the lower sand and bedrock
aquifer. Low levels of several metals and organic compounds were
detected, but they were found at concentrations that do not
present a concern at this time. Tables 2 and 3 provide summaries
of the occurrence of analytes in groundwater from the lower sand
and bedrock units respectively. .".
As previously ~oted, Operable Unit Two deals with only a
portion of the Site. The primary exposure pathway associated
with this operable unit involves the potential exposure to
contaminated groundwater by existing or future off-site
groundwater users.
Analytical data for groundwater samples collected from off-
site wells during the Phase II remedial investigation detected
metals and a few volatile organic compounds. Data from the
Phase I and Phase II remedial investigation do not indicate that
contaminants from the Site have reached the off-site wells
tested. However, the potential for future off-site migration of
contamination does exist.
The general direction of groundwater flow from the Site is
south or south-southwest. Estimated groundwater velocities are
shown in Table 4. The estimated velocities as well as the
calculated travel times shown on this table vary greatly as a
result of the heterogeneous nature of the sediments associated
with the Site. The calculated travel times are order of
magnitude estimates at best; actual groundwater velocities could
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TABLE I
TABLE 1
Summary of the Occurrence of Analytes Associated
With Ground water From the Middle Sand Unit
in the Western and Eastern Excavated Areas
(Means Calculated as the Average of the Detected Concentrations)
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TABLE 1
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. '.. .... . -"" ...ee... .. ...,. ..... ...,. ........
.' ... .... ... ......c. . ...... -. r...... .... ..11 K"'. a..ac..... ....a._. ... _II ........
. ... .... ... 1_...1(1 . ........ .. . .. ....-... ...... .. ... ...-... 1......,_.
I. ... ......CP ....... ..--. .u...". ....- ..'...... (881.. (a'U. OM"'.. (..... Q881'. u.. -....... ........ "'cll.' ......... ,"..... ~.. ....... .. II.
I '.. ..., . ...-.... .... ... .._.e. .... II'.... .. .......
. '.If' .... . -. (.888 ..... ... .... ... ......
.. 'tr .... . 8'" ...,. 'eee...'. .. -. ..... (...... .......
II. -.,.. .. 'II. .... . .... ...... ...... .... .. ... .....-. ..ee... ..... .... .... .... .... ... ","ec. ,,,,,,, "..UI.. ..... .08..
'I. -0' .... . ""n.. ....... ... .. ...... &18"" .......
II. -.. II.. . ,...... ....
M. .. . -. "'1""
.1. -II' .... ... ._...n . ....Iee... ....... u-......... lilt -.,. .... .. ... ".ee".. ...... ...e. ... .. .'ea.. ... '-""eI""" '_,,'n ... -'"'''' eec.......
... ."." '".." '..- . ...,.. .."ee.......... ...,. ....... """""""
" -... - -"'.. .. -..- . .U... "Ct"'" ..... ....... ........ I.... .. -... .... I'''. '1""""".
... .. "," ...,... .- .... "'1 ......... "..... "'" .. ....
." .. ._,,,,a... ,.. ..... .... ...a. h.... _,11. .. ...,......... 1M --......ae ..-.. ... .. ,. ,.ICA -. ...... .... .... .....
... lilt -... -" .. .. ..... .... c."ee." 1t...11 ..... .. .....
..... .-....... ,.. -....... -.. h._U ...... .. ...,............ __........ae ..-..... .....,rea -. ...... .... .... KI":
... '''01'-' C88C_"'''.- . .... ,... "'." e_........ .............. .. ... ..... ....... u ..... ... .. .,....Ua' -,.. ... ... ...... ... -,.......... -,..
... .... ... ... ,.... .. .......
... -. ... ",,"'..e It. "",'c -'." -. .. ...ee... ...... ... ....... ..... . ...... .... .. ..-- ... -''''c.... dIt8Ic.',. ... .....,~ ''''e.... c.......... .... - .-.."....
II .. ....,..... ... ....... c_-....... It II .-...,c """ .. -. "'H'"'''''' ... "'H". ..... . ...,.. .. _..... .. ... ..,..... ...., -. ..-.
.... ea.,- ..,..,.. e_......... .., "",'eI ... ...... .. .. .... It .. ..... .. ...... .......... . _............ c_......... ...,- "'H'" e_......... ... '-'''''ea ... ......
.... -' .. -...." .. ... ....- ......... ..... .-... ... ... -'."
......... .,.. -. ~..,..._....., .... -"". -.... ~--...... .. ... .........., "". -. .... .... ..... .... tI., ... ........ ..... ... .... _.,..; .......... ... -""
II ........ .. M . ........., .1 "'IC.
... ...... .... .. ......-....., ..... -..,..
-...... .. .. . .......... .. ....eI
-'''' c_-...... .. ... ............ -" -. .... ...... ..... .. ... .....U. ..... ... .... _.,..; .......... .... ...". II
-------
TABLE 2
Summary of the Occurrence of Analytes Associated
With Groundwa ter From the lower Sand Unit
In the Western and Eastern Excavated Areas
(Means Calcula ted as the Average of the Detected Concentra tions)
'eeoe' 18... .u, ... "'''.Uce. ,-"
.... ....... ...... e...."" .............. -.-... .......... ........ ......... .....e........ ........... ........ .....................................
018." OM." ... OM.... OM.'...' OM.'" ......... ..... ............ ....................
_... .Q., ..... ..... ..e.. II'" ..... OM." .....
.. ... ...... .............. .. .. .. .. .. .. ...... .. .. .. .. .. .. ...... ............... .. .
.118"'« ., 8J II ., 8J II .. II ..n ... .. .. '0"'11
IJ .. .e. ... -.. .«. 18"'«1 'UI':-
....u.. ...,..
................
.......~ (18'" ,. . 8 . I I 8 , , J 18 ,.1 ,. ,. . .. ,
.u... ." , . It .. I IS "' ,,. . .. ,
0.'.'.'.'. . . I . I , J ... 1 .1 .
....,~ I 8 I 8 J . I .. .
J. HIP....... JI" . . . .. .
'.'IMN ." '1 'M ' II M . . It 'M I .. .
(JI'.,,,,,,,~ .. . .. ... . .. ,
.. ..08.... , I .. .. .. .. .. .. .. .. .. , . ,. , . , ,
"8I".HIP"'~ M' " '' '' '' '' '' '' '' '' M. "' "" ,
"U "",".'.,.n .... .. .. .. .. .. .. .. .. .. III .. I ,. , . ,
,.."','....«. ....,..
..............".."."
"I.""~,,,,,'~'~"I' .. .. .. II .. ,. .. II " " II . I ,
"'I""~I~"I« .. . .. .. .. .. I I . . .
"'.'''I,'~I~''I« .. . .. .. .. .. . . . . .
""'~I,''-I~'..« .. . .. .. .. .. . . . . .
'«'''.C'. ", .. .. .. .. .. .. .. .. . , " I I ,
"",."~,,,,,,, . , t .. .. .. .. .. .. .. .. . I .., I I .
...«,-...."..(.,
811'" ....'"
...............
.....- .. UV ",... .. III ." 'IP "1 ., I". I8U .n ,.... "' "' .. . ,
I' Mft' ( , , U . . U I." ~ " U I , V . . I t. .. ..'" I.' V ., "' . . I' I'" J
11"- .. .. " PI liP .. ... . . I"" IU. . I' lIP .. V 11'1. ,. .. . I ' .
..",,,.. 'j . , U 'U .,." . . U . U .,." . 'V ..,." . U 1"'1. I.' I.' . ., . ,
(I'C'- .. 11188 ",... .. ...... "1' P ,..... II'" . ..... I" I'''' .n.. ..,.. ... . .
0.."'- "U . U .." '"~ .. . . " . U t." IU . . " .. " " .
<8M It .. , . V .. liP " . I V J' liP I . ¥ II" "'" '.1 lIP . . .. , " ,
CI88e' "'U .. V ""P ', "., II 'I. II¥ .. lIP ,.. V "'IP It. II ' . . ,
.... .. .u "M P .. J , ¥ ." P JU II'P ., V .11. . 1M 1111 . J ' .
UN MU I U I . Uf MU .11 . I of lit .....,.. IU ". .. . II ..., . I
....,.- .. Jell VI "" 'IP .. . II '" .... lIP 11M VI ." lIP . II WI "'.IP tI.. ... tI. . .
....... Ie .1 " MP .,. U . . ., II. . .., .... ~ II' II .1 .. .. . ., . .
.... "'" .. .... WI ...... .. ...... "'" . ",.. 'Jill. ".. ....... .... ".. II. ' .
,..1.. .. I'''' I .... PI .. ...... .... . .". I u... ..Jet .,.. II. .... ,... .,.. . .
"'1'1- .. ..U . . Uf .. . . ¥ .. ~ I.' U. I.' '" ..U . . ~ I' .. . . , .
--..,- .. ) . V , . liP " . . V I 1 " " ¥ tI'IP I.) V )., " ... " ' . . .
".. ... II \., .., po... ..'. . I. V .11.. II" It "" II" " PeN " ", '" .
..
"'v...
-------
/ 2 (con't)
Ul Will (•(••tint M<« Mil Itl
I klMt IM»<«• It «illail«« k««ui« •! ik« »i*i«o(* •! lm«il«i««c«
•»' !!•• • l<» «M« Ui *l«alin«i. «•!!••». M(I«B. MiyllllW. UtfalMT CiUlM>. CM«alM. cotall. Cl»lf. !>•* Mpwilia. Ma«M*M. w»rt«l Mlilllu*. SMMi.
t^lHB «MW«l«i MM IIM
"«" IU« • IMXMC* »». VM« ••« (IIMIIC. !••< MICHlHB. Mtf IIWllIlM
"CV ll*| • MMMl <•(* MM«I *• «M« IM •ttCMIlr
!• '«T !!•• • l*Ut Mfl»U ICCAMIV II ••) •IlklB C«lll*l IIMII.
II •«' *f 'IT IU| • Mllt«
I* •«/• IU« !•> IM>»MICI • HM*UCI«« IM MM«f «>l*Cl*IC« Bilk IM ~lf !!•• ll IM MIKIIWI Mall. «kUk «MII kt ItMkttf ••• iMfCMlCI kWMM iMIfMlCI *IC
14 •»» • -»» • M4 •«•' • iM«ltl c*ll(flt« 111 IM*. •«•?. *M IM* icMtcllotly
If '•!*.• -|l« ' *M "CS4* • OTIUl* «K«MI«« *lt«. I«II«IH |K**«IC« *!*« «"* CCMKl Silt MM.
!«• IM lUIIHIOI MMH(|r kMMII* IM MltflM lit •• CUCC«T« <•• KalwUII Itl .
141 «C*«I ••« *>IIMM*II< II Ml •>•*•!< MtlVIC Ml Ml «•!*€!•« *M«« IM *tl*CII«» I !•! I • MlM •! Itl* Ml «IUM*« 1*1 HWIIa«l<«l«> • tIMKM M M Ml* II •! lt
-------
TABLE 3
Summary of the Occurrence of Analytes Associated
With Groundwa ter From the Bedrock in the
Western and Eastern Excavated Areas .
(Means Calcula ted as the Average of the Detected Concentrations)
"..ee' "'" ..,
'................................................. -"'0"...".'''.'.'.......''..''''''.''.................''[[[ ......
_... _... ...,.
_... .c.IA' ..... ...., _.M ..... -.., .,ea.. ..... _.'" ..... --.. ,ca.1 _. II 'CIA' '''AI 'CIA I
'..""....'....'.,. ........................ ""'0."...... .............. .............. .............. ................ -
-"" IS .. .. .. .. 'I' .. II If II 'II If If .. If .. If .. .11 .. Ie,
_'UI'" ,...'1'
.................
..,"'I... ~,..I" . . . , . . .. . .. .. . . .. . " ,..
AC"- .. . .., "' . .. ... It ... III
. ..O'clI'........... . . .
-.- , . 1 . . . . .. . .. ,.,
.....- II . . .
'....CII.....I"" . . .
,.,- u .. . 18 II ... 1 . .. . . '18 ' .. ..,
8".... , . . .
u,e. ....,,,.. .. .. .. I , .. .. .. .. .. .. . ,
............. '...'"
......O'................
.11I...."'IIIt.,......",.... .. .. .. .. .. II . .. .. . . .. . . .. ", 'JJ .. ".
.,...ee.,. ......,.,. .. .. .. .. .. .. .. .. '"~ . . . I
.......", ...,...... .. .. .. 1 . .. .. .. .. .. .. .
......, .. .. .. .. .. .. .. .. .. I . . . I'
....,. ....' II
.................
..-- " .U 'M'" .. .. WIll .U .. WIll .U .. WIll .U .U .." .U .. WIll .,., .." ...." U'I" ..
8' -'C . . U ,.""...w , . U I.' II' , . U I 1 ... ,. U ... W , ... .. U , . II' ,. U . 1 ... . . "" . 1 II' .. 88' . II W . .
...,. .. "., "'''' '' II'''' ... ..." ., '" II'''' .n., M'" II'''' " ., "' .", ..., ...", ."" .'1" '"
..".... . . U , U '18" .. U ....", ..., ..,... . U '18" . U . U '11'''' . U '18" . U '18" ..." ''''1'' ..
u.c,. .. ._" u.." .. ... . 1"1 ,.... ...." ,... JIll .... ". ..." ...... ..... ..... . ..,.. ".." ..... " .,... ...
(I"",. .. . . U .,,, "U .." 'U "'" 'U "" . U ~ U ..." .U "" 'U "" "" "" .
c.ll1I .. .. ., ...", .. . ... .." ,..." ..., " ~ 'U ' ,.., "" .. . ., . ." IU "" ,. " I.'" . .
c....' "'U . U .. .", "'u .'1" ..., ",,, ,.,, ,," , U ..., . . " I '" " " 'U .." ,. ... "'1" .
II. .. ..... ...." .. .... " u. ". " .,. '18" '" I IU .. ".. '" .,.." ... I ,... ".. ..." ...." ....
t... MU .U ... MU '&W . ,,, .. W IU .. ... .., IU 1.1 W .U .. W . .., .. W 18' I.' W , I
-...... a " "M" ,...... .. "II'" ,... I ...." .... '" ....... nil., ", '" ..... 18" '" "'" I" """ '''' .", 1188. I" 'U"I" ....
....... .. .. .. ., " II II ". ,.. 18'" "' .. '" an a., .." II II" . I., fI" ,.. '" ., .. If
.......-. .. II. ., ..." .. ,n." ... n.. .... I ."." -- ". I ....." ....., ..,." .... ."." ...." ..... " flU
...,. .. IJIII I .....", .. ...... ,... I ...... "'" I ""'1" 'U" I ..... I ....." "M I ....... .... I ,..." ..-" 11-" ,...
........ .. ..U .. W .. ,. W ... U ,. w ..U ... W ..U "U ... W. ..U ,. W . ." . I W. . I W .. W .,
....... .. . .., ..... .. 1 a" . . ., . i" I ." ..a" , U . ., 1 '" . . " 1 '" . U . '" ... ~ I'" ..
-------
TABLE 3
(can't)
~ .. .. .. .. .. .. .. .. .. .. .. .. .. ..
III .... '~'.'" .... -.....:
. ,... ..c. . ....... .. .......
a. -.- .... . ........ c_..,....- ... c....-. .., _U 8M... ..... '''''11(8''. <"......, ,lie ....,.. <--...... .. .... ..... ... .... ........... ....,... ...... .. ..,..
) -,- ..., . -.... ....... .. ..... ......
. -.- ..., . -.... "'H'" .. ....,. ..... ..,. ........
. -.- ..., ... """(1 . ........ .. ....... ..... .... -... '.'UII.. ,...,_. ... ..,. ....88..
. -,- ...,"" '-""(1 . '....... -... .. ................ ... ......... ............
, -.- ..., . ,~. ....... ......-. ........ ...,.. ...,,,... ~.. (8'C'.. (11,_.. C81818. C8188,. If.. ....... -... "c"'. ......... .11-. ...... ...... ... II..
. -,- .... . 'UI..ce U. .... ... ..-.C. ..... ..,.... ... ......
. -cw- ..., . -. (888 .... u. .... ... ..C..,
.. -It" ..., . II'" ....,. "(8"" .. .. ....... c..... .......
.. -.,.... -..- "" . ..... ,...,.. ....... ....' .. ... ,....-. ...88. ..... "., .., .... .... ... (88".' ....,... 01..88. ..... 'GlCliI.
II. -.- .... . ""u.. ""'''' ... .. .11"'. c.U.. .......
II -.- .... . 'UIC'" ..,..
,. Nil.'" -"'"
" -\I" ..., ... '-""U . .......... ........ ..-..... ..... ... -\I" ..., .. ... ....U.. ...... ...C..... .. ...C,.. ... '_",'etllC"" ,,,,,,,'et ... """'''' .C""".
" -at. - -" - 8M ...- . ....... ,.lIfl'" ,.. '..,. ,..,. ... ..... ""'''''''
., -"..- -"..- 8M -GSA- . ....... ..C...... ..... ,...... ..e.....' ..... 8M ~... ..,. ..... ......,...,.
:'U - -...,c., ....,.. ...... ,.. .......,."...... ,......... ... ... .. ..... .. ....... ... ........". -., IIC..... ... 118"'" 88. .. ."..... ... ..............
'0 .... ... .. .......,. II... ....." -"" .. .. "'.(1"",,, .... "'IC"'" ...... . .... .. .... .. u~ ... _...c.... ,....."... ,.. .....,c ...It.... C....."... .... - -........
.. .111 .......... .... "..c... c_",........ II.. ,.......c ....... .. ... ..."......... .... ....e..- 01.... . ..... ., _.118" .. ... "'1("- ..... .. ......
'.. ....- ....etll c_....."... ... ......u ... ..-. .. .. II.. .. .. ..... - ...11 ......... . --"'1('88" ,_......,.... ....- '"1('" ,-.......-. ... ,-",'et... ..~
.. .. .-. .. "".N" .. .... ....- "..cll- ..... ........ ... .... ....".
III -..... ..... .. (......1..... ., .11.. ........ ....... u."....".. .. .... "-'-11' ....... .... ..... .... II.. ..., ... "'IC". ..... ... ..... -"": ........... .... -....
II ,....,..... .. .. . ""'.'0" ..II'nl
a
-------
TABLE *
Representative Croundwater Velocity Calculations and Resulting
Travel Time to the MSGS Southern Boundary
Changi Hydraulic Efftctivi Oiitanci to Travtl TIN to
Uil! Oiitanct in Htad Conductivity Porosity (a) Vtlocity (b) Boundary Boundary,
I dl (ft) dh (ft) K (ft/d) P V (fl/dJ D (ft) t (yr>
-------
19
be several orders of magnitude greater than the calculated
velocities- shown.
6.0 SUMMARY O~ SITB RISKS
An Endangerment Assessment was prepared to assess the.
potential human health effects that may result from exposure to
.Site releases in the absence of remediation. The portions of. the
Site specifically addressed by the Endangerment Assessment are
the soils, surface water, and sediments in the Western Excavated
Area and groundwater associated with the three water bearing
zones (the middle sand, lower sand and bedrock units) present in
both the Western and Eastern Excavated Area.
Contaminants in the surface water and groundwater comprising
the perched aquifer (i.e., the upper sand unit) in the Eastern
Excavated Area were not evaluated in the Phase II Endangerment
Assessment because those media were addressed in the Phase I
Endangerment Assessment. Soils and sediments associated
primarily with the Eastern Excavated Area also are not addr~ssed'
in the Phase II Endangerment Assessment, as they will be the
subject of a future focused feasibility study (Operable Unit 3).
Indicator chemicals (i.e., chemicals observed at the site
which are most likely to pose a threat to public. health and the
environment) for the MSGS Site are summarized below. Chemicals
selected only for specific media have the applicable media in
parentheses following the chemical. All other chemicals are
applicable to all media.
* Benzene
* Bis(2-ethylhexyl) phthalate
. (sediment)
* Di-n-butlyl phthalate
* Carbon Disulfide
* Chloroform
* l,l-Dichloroethane
* l,l-Dichloroethene
* l,2-Dichloroethene
* l,4-Dioxane
(BEHP)
* Phenol
* Tetrachloroethene
* Toluene
* l,l,l-Trichloroethane
* Trichloroethene
* Vinyl chloride
* Cadmium (soil)
* Lead (groundwater)
* Mercury (soil)
Exposure pathways were evaluated for two scenarios, current
and future use. The current-use scenario considered the existing
land use patterns of the area and evaluated the completeness of
potential exposure pathways based on the current land use
information. For the future-use scenario, the exposure pathways
were altered to reflect the effects of possible future changes.
Potential exposure to the indicator chemicals was evaluated for
both scenarios for the following media: .
* Middle sand unit groundwater
* Lower sand unit groundwater
* Bedrock groundwater
* Surface soil
-------
20
* Subsurface soil
* Surface water
* Sediment
* Aquatic life
* Air
Tables 5 and 6 summarize the current-use and future-use pathways,
respectively.
Because the western portion of the Site is open and
residential areas are adjacent to the Site, public access is
possible. Therefore, a potentially complete pathway under the
current-use scenario was defined as dermal and incidental
ingestion by exposure to the sediment in the Western Excavated
-Area. A potential future-use scenario for the Site includes
possible residential development up to the southern boundary,.
This scenario reflects public access to sediment and could result
in additional groundwater supply wells that withdraw water from
the middle sand unit, lower sand unit, and/or bedrock. Potential
future exposure routes related to exposure through groundwater'
include ingestion, dermal absorption during bathing, and
inhalation of vapors during water usage (e.g., showering).
Exposure doses and risks were calculated under conservative
most-probable and worst-case conditions. Risks calculated in
this manner represent the upper bound of the probability of
contracting cancer .from a lifetime of exposure. This means that
the true risk of contracting cancer is probably less and may be
zero. Probabilities are expressed in scientific notation. ,For
example, 1.0 E-6 is the same as 1 x 10.6 and equates to a one in
a million chance of contracting cancer. Similarly, 1.0.4
represents a one in ten thousand chance of contracting cancer.
Quantitative estimates of potential risks for the complete
pathways (i.e., direct contact with sediment and'soil for the
current-use scenario and exposure to sediment, soil and,
groundwater for the future-use scenario) are summarized below.
Sediment Excosure Pathway
Table 7 summarizes most-probable and worst-case risks for
exposure to sediment under both the current and future-use
scenarios. Risks under both scenarios are below EPA's target
risk range (10.4 to 10.6) and indicate no unacceptable,
carcinogenic risks related to exposure to sediment from the
Western Excavated Area under either the current or future-use
scenario.
Soil EXDosure Pathway
Table 8 summarizes the most probable and worst case risks
for exposure to soil under both the current and future-use
scenarios. Neither inorganic cadmium nor mercury compounds are
carcinogenic through oral exposure. Therefore, neither cadmium
-------
TABLE 5
Evaluation of Exposure Pathways--Current Use
Potential Transport Medioa/ Exposure Point/ Potential . Pathway
Media Source Release Mechanism Exposure Population Exposure Route Complete
Middle Sand Yesa Groundwater No NA No
Unit flow/leaching
Lower Sand Yesa Groundwater No NA No
Unit flow/leaching
Bedrock Yesa Groundwater No NA No
flow/leaching
'Surfac~ Soil Yes Direct contac i Yes Incidental ingestion Yes
(WEA)b
Subsurface Soil Yes Direct contact Yes Incidental ingestion Yes
(WEA)
Surface Water No NA NA NA No
(WEA)
Sediment Yesc Direct contact Si te/humans Dermal contact/ Yes
(WEA) incidental ingestion
Aquatic Life No NA NA NA No
(WEA)
Air No NA NA NA No
(WEA)
aThe potential source is the near-surface contamination confirmed at the Eastern Excavated Area-
b
Western Excavated Area-
c-
o Thf' ~IIIII I~dl ~urce dppears to be runoff ftom the Eastern Excavated Area-
-------
Media
-He Sand
u Sand
drock
Jrface Soil
VEA)b
\Jbsurface Soil
VEA)
.Jr face Water
:tEA)
. ~diment
ilEA)
\quatic Life
. 'ilEA)
\ir
TABLE 6
Evaluation of Exposure Pathways--Future Use
Potential Transport Media/ Exposure Point/ Potential . Pathway
Source Release Mechanism Exposure Popula tion Exposure Route Complete
Yesa Groundwater Of fsi te/humans Ingestion/inhala tion/ Yes
flow/leaching dermal contac t
Yesa Ground wa ter Offsite/humans Ingestion/inhala tion/ Yes
flow/leaching dermal contact
Yesa Groundwater Offsite/humans IngestionJinhala tion Yes
flow/leaching dermal contact
Yes Direct contact Onsi te/humans Incidental ingestion/ Yes
inhalation
Yes Di rec t con tac t Onsi te/humans Incidental ingestion/ Yes
inhala tion
No NA NA NA No
Yesc Direct contact Site/humans Dermal contact! Yes
incidental ingestion
No NA NA' NA No
No NA NA NA No
rhe potential source is the near-surface contamination confirmed at the Eastern Excavated Area.
':'estern Excavated Area.
. Ie principal source appears to be runoff from the Eastern Excavated Area.
+.,
-------
Operative
pathway
Sediment
23
Table 7
Calculation of Most Probable and Worst Case
U~Der Bound Total Incremental Risk from Potential Carcinoqens
Current and Future Use - Sediment'
Applicable
Indicator
Chemical
Current Use
Chemical-SDecific Risk
Most Probable Worst Case
Future Use
Chemical-SDecific Risk
Most Probable Worst Case
Benzene
3.07 E-13 1. 65 E-11 3.31 E-12 1. 07 E-09
9.94 E-13 4.22 E-11 2.45 E-11 1. 96 E-09
2.09 E-12 7.60 E-11 9.08 E-12 6.99 E-09
7.56 E-12 1.76 E-10 3.28 E-11 1.62 E-08
1.10 E-11 3.11 E-10 6.97 E-11 2.63 E-08
Chloroform
Tetrachloroethene
Bis(2-ethylhexyl)
phthalate
TOTAL RISK
-------
Operative
Pathway
Soil
a)
b)
24
Table 8
Summary of Most Probable and Worst Case
Upper Bound Total Incremental Risk from Potential Carcinoqens
Current and Future Use - Soil
Applicable
Indicator
Chemical
Current Use
Chemical-Specific Risk
Host Probable Worst Case
Future Use
Chemical-Specific Risk
Most Probable Worst Case
Cadmium
3.15 E-09
9.03 E-07
--a
--a
Mercury
--b
--b
--a
--a
Total Future Use site Risks.
Resulting from Exposure to Soil:
3.15 E-09
9.03 E-07
No carcinogenic risks, because inorganic cadmium and mercury
compounds are not carcinogenic by the oral exposure route.
No carcinogenic risks, because mercury is not carcinogenic
via the inhalation exposure route.
-------
25
nor mercury pose carcinogenic risks under the current-use soil
exposure scenario. Carcinogenic risks under the future-use
scenario are at acceptable levels, and remediation of soils in
the Western Excavated Area of the Site is not warranted.
Groundwater EXDosure Pathway
. Table 9 summarizes the most probable and worst case risks
for exposure to groundwater under the future-use scenario. The
following are the most probable and worst case carcinogenic risks
for the middle sand, lower sand and bedrock units summarized from
that table.
Water Bearina Unit Most Probable Worst Case
Potential Risk Potential Risk
Middle Sand 1.48x10-2 2. 51x10-2
Lower Sand 3. 66x10-5 -5
9.. 20x10
Bedrock 2. 99x1(f6 3. 79X10-6
The upper limit of the target risk range is exceeded for the
middle sand unit only. For this unit, for both the most-probable
and worst-case scenarios, the principal chemicals driving the
risk are: chloroform; 1,1-dichloroethene; tetrachloroethene;
trichloroethene; and vinyl chloride. These chemicals were
detected in the middle sand unit only at well DMW-07, located in
the Eastern Excavated Area. Vinyl chloride, for which a single
concentration of 6 ppb was detected, was observed in well D&M-03
in 1987. However, a more recent analysis (1988) of well D&M-03
did not detect vinyl chloride. Therefore, the area of the MSGS
site where the middle sand unit poses human health risks is in
the vicinity of well DMW-07. This is consistent with the
documented contaminant source in the upper sand unit in the area,
and the flow of ground water into the middle sand unit.
Table 10 summarizes the hazard index calculated under both
most-probable and worst-case conditions for exposure to
groundwater under the future-use scenario. The hazara index is
the ratio of the estimated dose received by exposed individuals
to the reference dose. The reference dose is a chronic dose
believed to be without effect in human populations. Thus, a
hazard index of less than 1.0 (estimated dose is less than
reference dose) suggests that harmful effects are unlikely; a
hazard index greater than 1.0 suggests that safety is no longer
certain.
,::,.
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26
Table 9
Snmmarv of Most Probable UDDer Bound and Worst Case
Total Incremental Risk from Potential Carcinoaens
. Future Use - Groundwater*
Most probable
Worst
Case
Aauifer/Chemical
SDecific Risk
Chemical-SDecific Risk**
Chemical-
Middle sand unit
Chloroform
l,l-Dichloroethene
1.16E-04 2.53E-04
1.40E-02 2~39E-02
2.25E-05 2.84E-05
2.12E-05 3.46E-05
6.01E-04 9.15E-04
1.48E-02 2.51B-02
Tetrachloroethene
Trichloroethene
Vinyl chloride
TOTAL AQUIFER RISK
Lower Sand Unit
Benzene
1,4-Dioxane
1.16E-05 2.49E-05
2.04E-05 6.15E-05
4.60E-06 5.55E-06
3.66B-05 9.20B-05
Chloroform
TOTAL AQUIFER RISK
Bedrock
Tetrachloroethene
2.99E-06
3.79E-06
TOTAL AQUI~Ba RISK
2.99E-06
3.79B-06
*Includes oral, dermal and inhalation exposures
**Means calculated as average of the detected concentration
-------
Aauifer/Chemical
Middle Sand Unit
Chloroform
l,l-Dichloroethane
l,l-Dichloroethene
1;2-Dichloroethene(a)
Tetrachloroethene
Toluene.
l,l,l-Trichloroethane
Trichloroethene(a)
Vinyl chloride(a)
Di-n-butyl phthalate
L- ~
tof Hazard Indices
.Lower Sand Unit
Benzene(a)
Chloroform
1,4-Dioxane(a)
Toluene.
Lead
Sum of Hazard
Indices
Bedrock
Carbon disulfide
l,l-Dichloroethane
Tetrachloroethene
Toluene
Di-n-butlyl phthalate
Phenol
Lead
Sum of Hazard Indices
27
Table 10
SummarY of Noncarcinoaenic
Chronic Hazard Index
Future Use - Groundwater
Most Probable Scenario
Worst Case Scenario
Oral and
Dermal
Oral and
Dermal
Inhalation
4.9SE-02
4.10E-OJ
3.1JE-Ol
4.27E-Ol
1. 20E-02
1. 20E-02
,,': .'~
4.3SE-03
1. 20E-02
3.7SE-02
5.38E-02
( a)
Chemical for which non carcinogenic AIC data are unavailable
in the Superfund Public Health Evaluation Database.
Inhalation
6.l3E-02
2.0JE-02
6.S0E-Ol
2.64E-02
l.JOE-01
l.29E-02
7~8JE-Ol
4.0JE-02
6.SJE-03
2.26E-Ol
1.24E-03
l.OlE-Ol
4.8.SE-02
8.80E-03
3.06E-Ol
4.24E-03
1. 64E-Ol
1.17E+OO
1.29E-Ol
6..27E-OJ
S.4SE-Ol
l.8SE+00
1.62E-02
3.l7E-02
4.47E-03
2.3lE-Ol
2.S2E-Ol
l.33E-03
2.58E-02
S.4SE-Ol
. 6. 03E-Ol
1. 33E-OJ
6.S8E-04 1.29E-03
1.78E-03 2.32E-OJ 2.1SE-03
S.36E-03 6.46E-03
7.07E-03 2.llE-03 2.S8E-02
1.82E-03 2.70E-03
S.30E-03 1. 93E-04 8.08E-03
1.70E-Ol 6.32E-Ol
l.92E-Ol 4.62E-03 6.78E-Ol
'. .""
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28
The following are the most probable and worst case hazard indices
for the middle sand, lower sand, and bedrock units summarized
from Table 10.
Water Bearinq Unit
Most Probable
Hazard Index
Worst Case
Hazard Index
Middle Sand
1.3
2.28
Lower Sand
0.25
0.62
Bedrock
0.20
0.72
Each of these hazard indices are the sum of the hazard
indices developed for the oral, dermal and inhalation exposure
routes.
The hazard index exceeds 1.0 for the middle sand unit under
both the most probable and worst case scenarios. This finding is
consistent with the findings of the carcinogenic risk evaluation,
which indicated that unacceptable health .risks may be posed by
the middle sand unit.
Actual or threatened releases of hazardous substances from
the Site, if not addressed by implementing the response action
selected in this Record of Decision may result in an imminent and
substantial endangerment to the public health, welfare or the
environment.
7.0
DESCRIPTION OF ALTERNATIVES
The following section describes remedial action
alternatives that were evaluated for this operable unit in
accordance with the NCP (See 40 C.F.R. ~ 300.430, 55 Fed. Req.
8846, March 8, 1990). It is important to remember that the scope
of Operable Unit Two included analysis of groundwater
contamination in the lower aquifers (i.e., middle sand, lower
sand and bedrock units) and evaluation of contaminant sources in
the Western Excavated Area. Since the remedial investigation
concluded that there was no evidence of waste disposal in the
Western Excavated Area, the following alternatives deal only with
remediation of groundwater in the lower aquifers. Remedial
alternatives for surface water and groundwater in the upper sand
unit were evaluated in the Phase I Remedial Investigation/
Feasibility Study. Soils and sediments, primarily associated
with the Eastern Excavated Area, will be addressed in a future
focused Feasibility Study (Operable Unit Three).
In developing and evaluating remedial alternatives for the
lower aquifers, it is important to keep the overall problems
-------
29
associated with this Site in perspective. As summarized in the
Phase I Record of Decision, the soil and groundwater in the upper-
sand unit in the Eastern Excavated Area of the Site are highly
contaminated with a variety of organic and inorganic compounds.
The soil and groundwater in this area will continue to act as a
source of contamination until it is removed or controlled. The
threat posed by this contamination is that it will migrate down
into the lower aquifers, -and eventually offsite. This would
present an unacceptable risk to individuals using this
groundwater. Residents downgradient from the site currently use
the middle sand and lower sand units as a water supply source.
Since it is impossible to predict with any certainty the
time required to reduce contamination in the upper sand unit to
acceptable levels, the alternatives developed to deal with
contamination in the lower aquifers focus on ways to monitor and
react to contamination over an extended period of time. -
A total of six alternatives were evaluated- to deal with
current and potential future contamination in the lower aquifers.
They are summarized as follows:
7.1
ALTBRNATIVE 1 - NO ACTION
The reason for evaluating a no action alternative is to
provide a basis for comparison of existing conditions with other
proposed remedial alternatives.
I
I-
Since no remedial measures would be taken under this
alternative, risk to the environment and public health would only
be influenced by the present hydrology and geology and the
implementation of the Phase I ROD. With groundwater treatment
instituted under the Phase I remedy, the concentrations of
compounds in leachate generated from the upper sand unit should
decrease. Compounds already in the upper and middle sand units
could continue to migrate and leach/seep into the middle and
lower sand units until the upper sand unit is remediated. Thus,
with the passage of time, the risk associated with the lower
water bearing units at the site may increase before decreasing.
contaminants have been detected in the middle sand unit
above acceptable levels. The no action alternative would not
provide for the reduction of pollutant levels in the onsite
groundwater. This would result in violation of the Maximum
contaminant Levels (MCLs) and non-zero Maximum Contaminant Level
Goals (MCLGs) established under the Safe Drinking Water Act -(40
C.F.R. Parts 141 and 143). Further, no action would allow the.
continued migration of onsite contamination into deeper portions
of the aquifers and eventually offsite. This would allow -
additional human exposure to contaminants associated with this
Site. The no action alternative would result in no direct
capital or operation and maintenance (O&M) expenditures.
.- -
...'
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7.2
30
ALTERNaTIVE 2 - ONBITE GROUNDWATER MONITORING
Alternative 2 consists of onsite groundwater monitoring.
Wells to be monitored include six new wells and eleven existing
wells (refer to Figure 6). These wells are located upgradient.
and downgradient of the area where wastes were disposed and
.provide for monitoring of the middle sand, lower sand and bedrock
units. No monitoring in the upper sand unit is provided since it
will be closely monitored during implementation of the Phase I
ROD.
Quarterly samples would be taken from the 'middle and lower
sand unit wells and analyzed for Target Compound List (TCL)
volatiles. These wells would be sampled annually for Target
Analyte List (TAL) metals. Bedrock wells would be sampled.
annually and tested for volatile organic compounds (VOCs) and
metals. The sampling program would continue until two years
after start up of the Phase I treatment system (currently
projected for mid-1993), or approximately four years of
monitoring. At that time, VOC sampling of the middle and lower
sand units would be reduced to semiannually, until a total of
five years has elapsed and the monitoring program is reevaluated.
If further monitoring beyond the five years is deemed necessary,
or if expansion of the program is warranted based on monitoring
results, revisions to the monitoring program will be developed
and implemented.
This alternative, as with no action, would not result in
compliance with Federal ARARs (MCL's and non-zero MCLGs)
associated with drinking water. Concentrations of contaminants
in excess of established MCLs have been documented onsite in the
middle sand unit. Monitoring alone would do nothing to reduce
contaminant levels, although it would provide a means to measure
the changes in groundwater conditions due to attenuation,
dilution, or the Phase I treatment system.
Federal Resource Conservation and Recovery Act (RCRA)
requirements contained in 40 C.F.R. S 264.90-264.101 pertaining
to groundwater monitoring were determined to be relevant and
appropriate, and would be complied with during the implementation
of this alternative. In addition, Maryland's well construction
requirements (MD. Code Ann.S 26.04.04) and OSHA requirements for
workers at remedial action sites 29 C.F.R. Part 1910 would be
achieved.
Capital costs for this alternative are estimated to be
$114,000 with annual O&M costs of approximately $92,400. The net
present worth of this' alternative at a discount rate of 10% for
30 years is $614,000.
;~ '"
..."';' .< '.
-------
WE LLS TO »E MONIT
MSI. MS% MS 3. MM. MSfc.
OMW 07. SMUMOL MUMOt.
--^^c^l-.
. --If-
DM* 12
Figure 6
APPMOXIMATE LOCATION OF OMSITi
MONI1JI (Q Wf LCS
|AtTEMN4 I a. JL AND 41
-------
7.3
32
ALTBRHaTIVB 3 - ORSITB AND OPPSITB GROUHDWATBR XOBITORIBG
Alternative 3 consists of onsite and offsite groundwater
monitoring. The onsite monitoring portion of this alternative is
identical in scope to the onsite monitoring program described for
.Alternative 2. The offsite monitoring program would encompass
four wells serving both residential and commercial users.
The proposed offsite monitoring well locations are shown on
Figure 7. The wells were selected to maximize the likelihood of
detection of contamination from the Site. Most of the locations
are south of the Site, in the direction of groundwater flow. A
large volume groundwater user is included in the monitoring plan
'to account for the possibility that contamination might
preferentially be drawn to this location. Access and permission
to sample will have to be obtained for each well from the
property owner prior to sampling. . .
Offsite monitoring would be conducted on an annual basis,
with samples being analyzed for TCL VOC's and TAL metals. As
with. the onsite program, the monitoring schedule and number of
.,offsite wells monitored may be expanded as necessary to provide
-information on plume migration. . The scope of the monitoring
program would be reviewed at least every 'five years, in
compliance with Section 121(c) of CERCLA, 42 U.S.C. S 9621(c),
and continued as necessary.
This alternative would not result in compliance with Federal
ARARs (MCLs and non-zero HCLGs) associated with drinking water.
Monitoring alone would do nothing to reduce contaminant levels
although it would provide information about the condition of
groundwater both on and off-site.
Federal RCRA requirements contained in 40 C.F.R. S264.90-
264_101 pertaining to groundwater monitoring were determined to
be relevant and appropriate, and would be complied with during
the implementation of this alternative. In addition, Maryland's -.
well construction requirements (MD Code Ann. S 26.04.04) and OSHA Y'
requirements for workers at remedial action sites (29 C.F.R. Part
1910) would be followed.
This alternative consists of monitoring 17 onsite and four
offsite wells chosen to provide representative samples from the
middle sand, lower sand, and bedrock units. Capital costs' for
the alternative are estimated to be $114,000 with annual O&M
costs of approximately $101,800. The net present worth of this
alternative at a discount rate of 10% for 30 years is $702,400.
7.4
ALTERNATIVE 4 - ORSITE AND OPPSITE GROUNDWATER MORITORING
WITH DEPERRED OPPSITE TREATMENT
Alternative 4 invoives the use of onsite and offsite ,
monitoring as described for Alternatives 2 and 3. In addition,
if indicated by offsite monitoring data, offsite point-of-use
",,,,~,""~."'.~"',-. "- '..
-------
KEY:
Figur^ 7
LOCATION OF Of FSITE
MOMITOMINQ NELLS
#»,•
*. . , ft-l^i
-------
, -~
,
34- -
treatment would be implemented. For offsite wells, detection of
any of the contaminants of concern during a particular monitoring
period would require immediate resampling of the affected well.
concurrently, bottled water for drinking purposes would be made
available to the affected residence or business. As noted under
Alternative 3, the scope of the monitoring program would be.
evaluated and adjusted as necessary in order to provide
information on plume migration.
Action levels that would "trigger" the implementation of
offsite groundwater treatment include MCLs for those contaminants
for which these criteria exist, a cumulative carcinogenic risk in
excess of 10'4 or a hazard index greater than 1.0. The
cumulative risk and hazard index estimates shall include all
detected contaminants. The existence of any of the above three
conditions would trigger treatment. ~
If any of the contaminants of concern are detected at levels
above these action levels following confirmation sampling --
employing statisti~al analysis, then point-of~~se treatment
systems would be installed at the affected wells. The type of
>system would depend on the analytes found during monitoring. -
~Highly soluble organics not amenable to granular activated carbon
adsorption would require a small scale point-of-use air stripper.
If other organics are confirmed, an activated carbon unit would
,be utilized either with or without the air stripper. An ion-
exchange system would be provided for metals removal. The ion
exchange system may be used in series with the granular activated
carbon filter and/or the air stripper. The exact nature and
configuration of the point-of-use treatment systems would be
based on the contaminants found in a particular well. These
systems would be maintained in proper working order (e.g.,
replacement of carbon filters) throughout their useful life.
This alternative would result in compliance with the MCLs
and the non-zero MCLGs established under the Safe Drinking Water
Act at the point of use. If offsite detection of analytes were
limited to a small area, this alternative would be protective of
groundwater users in that area without requiring construction of
a complete large-scale treatment system.
- - ~
The overall objective of the point-of-use treatment systems
would be to reduce the concentration of contaminants to
acceptable levels (i.e., 10-6 carcinogenic risk and a Hazard
Index ~1.0). In addition, the point-of-use treatment systems
would result in compliance with MCLs and non-zero MCLGs
established under the Safe Drinking Water Act.
In addition to the ARARs identified under Alternative 3
pertaining to the monitoring aspects of this alternative, ~he
following requirements pertaining to the treatment aspect of this
alternative would be achieved.
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35
The state of Maryland's requirements pertaining to air
pollution control would be complied with during the
implementation of this alternative. Also, any waste product
(e.g., spent residential carbon filter cartridges) determined to
be hazardous would be transported in accordance with Department
of Transportation regulations, 49 C.F.R. Part 107 and 49 C.F.R. S
171.1 through 172.558, and disposed of in accordance with the
waste disposal requirements of 40 C.F.R. Part 261, including the
land disposal restrictions, 40 C.F.R. Part 268.
Costs for this alternative would vary, depending upon the
number and type of point-of-use treatment systems installed. A
range of costs have been developed based on best-case (no
treatment units necessary) and worst-case (all three treatment
technologies required for all residences and businesses within
the affected area during the first year). It is important to
note that these costs are order-of-magnitude estimates and. are to
be used for comparison purposes only. Actual costs may differ
due to development in the area or a larger affected population.
. The costs for the best-case situation would.be the same as
those identified for the onsite and offsite groundwater
monitoring alternative (Alternative 3). These costs consist of
capital costs amounting to $114,000 and annual O&M costs of
$101,800, that result in an estimated net present worth of
$702,400.
The worst-case estimate is based on the installation of
point-of-use water treatment systems in 25 residences and three
businesses. This case would have capital costs of $556,400, O&M
costs of $167,000 per year, and a net present worth of .
$1,763,700. Monitoring for all units would continue on an annual
basis for 30 years. As with the previous alternatives, the scope
and schedule for monitoring would be reevaluated at least every 5
years in accordance with Section 121(c) of CERCLA, 42 U.S.C. S
9621(c), and continue as necessary. .
7.5
ALTERNATIVE 5 - ONSITE GROUNDWATER MONITORING WITH DEFERRED
ONSITB TREATMENT
Alternative 5 involves the onsite groundwater monitoring
program described in Alternative 2 coupled with onsite pumping
and treatment of contaminated groundwater. The action levels
that which would "trigger" the implementation of onsite
groundwater treatment are, as described previously, HCLs, a
cumulative carcinogenic risk of 10'10 or a hazard index greater...
than 1.0. If groundwater treatment is determined to be required,
it would involve use of the Phase I treatment system. The
decision process for implementing onsite groundwater treatment is
shown in the lower portion of Figure 8.
Implementation of this alternative must be coordinated with
the Phase I remedy. It is important to remember that the
contaminated soil and groundwater in the upper sand aquifer in
-------
,
;
~
~
I
~
a
..
..
o
No
,~ !~ ANAL v..
\j".'
).;: ..- RIUII"
I ',: t. e-.,..,- ...
\ ~i ~ --~ORIIIG
.~ ;: DATA
., .
:~<
EVALUA TI
INDICA TOR
CHEMICAU
DETECTED
FOR
REATA8IU
.:1;"
to ."
~
~
~
1M
.
~
I
,
.
I
I
/
I !
,
\ ~
llilAWLE
ON88Y1
_LU.
Y..
~
~
'NSTALL
POINT -OF.uSl
TREATMENT
UNIT' AI .
MPROM8ATE
EVALUATE
TE/Off."
MONITORING
NEtWORK AND
EXTRACTION
.VITEM AND
EXJlANDAI
NECiIlARV
FIGURE 8
DECISION PROCESS'FOR IMPLEMENTING ONSITE AND/OR OFFSITE WATER TREATMENT
. CAL TERNA TIVES 5 AND 6)
[ ,
INS'ALU
EXPAIIO
EXTRACTION
! WELL IVITEM
AND EXPAND
. PHAII.
TREAn.NT
IVITEM AI
NECEIlARV
RE-
""'OIIING
....... . II....
-------
37
the Eastern Excavated Area will continue to act as a source of
contamination until it is removed or controlled. Thus the
groundwater treatment portion of this alternative could have
negative impacts on the groundwater quality within the lower
aquifers if it were implemented without regard to contaminant
sources in the upper sand unit. Lowering of the hydraulic head
by pumping from the middle sand unit could accelerate the rate of
downward migration of contamination from near-surface
groundwater. .
Information concerning the design and performance of the
Phase I groundwater treatment system must be taken into account
during the design and implementation of this alternative. For
example, information concerning the effect which Phase I
treatment in the upper sand unit has on groundwater quality in
the underlying middle sand, lower sand and bedrock units would
affect the design of this system. Also, the method of disposal
(gravity outfall line to discharge point south of the Old
Sedimentation Pond or discharge into the on-site ponds) of
treated effluent from the Phase I treatment system may reduce or
increase recharge to the unconfined portion of the middle sand
unit along the western tributary of Mill Creek and in the sedge
Meadow Area. This would impact design alternatives for extract-
ing groundwater from the units underlying the upper sand unit.
The proposed groundwater collection system associated with
this alternative provides for the installation of three
extraction wells. The tentative location of these extraction
wells is shown on Figure 9. The proposed location of these wells
coincide with the three seep areas that have been identified as
the most likely patb for migration of contaminants from the upper
to the middle sand unit. The actual number .and location of the
extraction wells will be determined during design.
. Initially, these extraction wells would be pumped at a rate
only large enough to prevent contaminant migration through the
middle sand unit away from the seep areas. This would be done in
an effort to contain contamination to a discrete on-site area.
Full-scale remediation of the lower water bearing units (e.g.,
pumping these wells at higher rates) would be delayed. until the
Phase I remedial system in the upper sand unit has operated long
enough to reduce the potential for further contaminant migration.
The initial production rate from the three middle sand extraction
wells is estimated at approximately 10 gallons per minute.. This
rate will depend on local conditions at the well locations.
The on-site Phase I (upper sand) treatment facility would be
expanded and modified as necessary to treat the groundwater from
the lower water bearirig units. It is expected that if contami-
nation is confirmed in the lower water bearing unit it will
likely contain the same type of contaminants found in the upper
sand unit. Thus, expansion of the Phase I treatment system will
provide an efficient means of providing treatment for this
groundwater.
-------
CUMUM AIM ol EnrKiteii «Mk
n ' 6-vk (
; C'.. r--<\& \
J U-^:M4-
Figure 9
APf ROXIMATE LOCATION OF
MONITORINQ AND EXTRACTION IttLl
(ALTERNATIVES I AND •)
-------
39
The scale-up of the Phase I system to accommodate the
increase in flow should not affect the overall technical
feasibility of the system. The flow increase would be
approximately 10 gallons per minute or 14,400 gallons per day.
This will result in the approximate doubling of the capacity of
the Phase I treatment system.
As noted in the September 30, 1985, ROD for Operable unit
One, the objective of the Phase I (and now the Phase II)
treatment system is to reduce organic compound and heavy metal
concentrations in the groundwater to an acceptable risk level
(10.6) or meet standards determined by the Agency. .
In addition, an objective of the Phase II treatment system
is to reduce the non-carcinogenic risk associated with potential
exposure to .groundwater in the lower aquifers to acceptable
levels (i.e., Hazard Index~1).
The remedial action objectives for this alternative include
achievement of MCLs and non-zero MCLGs at the point of . .
compliance. The "point of compliance," or point at which
compliance with the remedial action objectives will be measured,
will include all wells placed in the plume of contamination. The
time required to achieve the remedial action objectives cannot be
determined with any accuracy, and was not estimated.
As discussed under Alternative 2, federal requirements
pertaining to groundwater monitoring, state well construction
requirements and OSHA requirements for workers at remedial action
sites would be complied with during the implementation of this
alternative. .
In addition, the fOllowing requirements pertaining to the
treatment aspects of this alternative have been determined to be
applicable or relevant and appropriate and would be complied with
during remedy implementation. The provisions of the National
Pollutant Discharge Elimination System 40 C.F~R. Parts 122-124,
and the State of Maryland's requirements pertaining to direct
discharges, MD Code Ann. S 26.08.01 through 26.08.04, would be
applicable to the discharge of treated groundwater.
Effluent limitations would be based upon state water quality
standards and federal ambient water quality criteria. The state
water quality standards would be used for those compounds
specifically addressed by the standards. Ambient water quality
criteria would be used to develop effluent limitations for
compounds not specifically addressed by the standards.
Discharges of treated effluent would be to a tributary of Elk
Creek which is designated as a freshwater stream. The designated
uses of Elk Creek and its tributaries include water contact
recreation, protection of aquatic life and public water supply.
Therefore, the water quality criteria for water and fish
-------
40.
ingestion and both acute and chronic aquatic impacts would be
relevant and appropriate criteria to be used in the development
of discharge limitations.
The treatment facility would comply with the State of
Maryland's requirements pertaining to tank standards and
generators of hazardous waste (MD. Code Ann. ~ 26.13.05.06 and
26.13.03).
Air releases resulting from onsite treatment would be in
compliance with the applicable provisions of Maryland's.
requirements pertaining to toxic air pollutants (MD Code Ann.
~ 26.11.15). In addition, the state's requirements pertaining to
testing, recordkeeping, odors and permits associated with the air
pollution control aspects of this alternative have been
determined to be relevant and appropriate. Citations to the
particular provisions of these requirements are summarized in
Table 7 which is located in Section 7.6 of this ROD. . Since the
site is located in an attainment area, the p~visions of the
above state requirements were determined to be applicable or
.. relevant and appropriate rather than those contained in OSWER
"Directive 9355.0-25, entitled, "Control of Air Emissions from
superfund Air Strippers at Superfund Groundwater sites."
Waste products (e.g., s.udge, spent carbon). resulting from
the treatment of groundwater would be managed in accordance with
the applicable provisions of RCRA at 40 C.F.R. Part 261,
including land disposal restrictions at 40 C.F.R. Part 268.
Listed hazardous wastes were disposed of at this site, and these
constituents are now "contained in" the groundwater being ..
treated. Thus the cited requirements are applicable because they
relate to the treatment and disposal of wastes containing
hazardous wastes. ' .
." .
Transportation of
out in compliance with
regulations, 49 C.F.R.
172.558.
waste materials offsite would be carried
the applicable provisions of u.s. DOT
Part 107 and 49 C.F.R. ~ 171.1 through
EPA's policy set forth in 40 C.F.R. Part 6, Subpart A,
pertaining to the protection of wetlands would also be applicable
to the groundwater treatment aspects of this alternative, but
only in the event that groundwater extraction actually results in
an adverse effect on wetlands. .In such case, actions to minimize
the adverse effect or recreate lost wetlands would be taken.
Costs for the first phase of this alternative would be"
identical to those developed for Alternative 2-0nsite Groundwater
Monitoring. This monitoring would have a capital cost of
$114,000, an annual Q&M cost of $92,400, and a net present. worth
of $614,100.
Costs for treatment were based on the change in flow
capacity that would be required for the Phase I treatment system
-------
41
to accommodate groundwater extracted from the middle sand unit. -
The Phase I system would require approximately twice the current
design capacity. The cost of this increase has been estimated as
50 percent of the capital and O&M costs presented in the Phase I
FS. The total worst-case cost of this alternative, assuming both
onsite monitoring and treatment, would involve a capital cost of
$1,151,100, annual O&M costs of $550,900, resulting in a net
present worth of $6,063,400.
7.'
Al~erDa~ive , - ONSITE AND OFFSITB GROUNDWATER MONITORING
WITH DEFERRED ONSITB AND OFPSITB TREATMENT
Alternative 6 involves the use of onsite and offsite
monitoring as described in Alternatives 2 and 3. In addition, if
indicated by monitoring data, onsite and/or offsite point-of-use
treatment would be provided. Immediateonsite treatment for
containment purposes (if necessary) would involve pumping -and.
treatment of groundwater from the middle sand unit using wells
located in the seeps, as described in Alternative 5. If further
onsite treatment is deemed necessary, a more extensive extraction
system would be designed. Offsite treatment (if-necessary) would
involve point-of-use treatment systems and the decision mechanism
discussed under Alternative 4. .
The decision process for implementing onsite and/or offsite
point-of-use water treatment is shown on Figure 8. An initial
decision to install either onsite or offsite point-of-use water
treatment would be based on the results of a statistical analysis
of the respective monitoring information. Detection and-
confirmation of indicator chemicals at statistically significant
concentrations above action levels in offsite wells would result
in installation of appropriate point-of-use treatment units at .
the affected locations. Action levels that "trigger" the
implementation of onsite and/or offsite groundwater treatment
include MCLs for those contaminants for which these criteria
exist, a cumulative carcinogenic risk in excess of 10-4, or a
hazard index greater than 1.0. The cumulative risk and hazard
index estimates shall include all detected contaminants. The
existence of any of the above three conditions would trigger
treatment. .
The network of onsite and offsite monitoring wells would be
evaluated for possible expansion in view of the location and
water-bearing unit of the affected welles) and the
concentration(s) of indicator chemicals detected. changes would
be made to the network (as necessary) prior to the resumption of
monitoring. In addition, both monitoring networks would be -
reevaluated especially in terms of scope and schedule every five
years, in accordance with Section 121(c) of CERCLA, 42 U.S.C. .
!i 9621(c).
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42
Federal and State ARARs and remedial action objectives
associated-with the various components of this alternative have
been discussed previously under Alternatives 4 and 5, and are
summarized in Table 11.
Costs for this alternative would vary depending upon whether
onsite and offsite treatment are found to be necessary, and the
,extent to which treatment must be provided at either of these-
locations. A range of costs has been developed based on best-
case (no treatment units necessary) and three worst-case (onsite
treatment, offsite treatment, or both) situations.
The costs'for the best-case situation would be the same as
those developed for the onsite and offsite groundwater monitoring
alternative (Alternative 3).
The cost estimate for implementation of offsite treatment on
a worst-case basis is based on a maximum of 25 residences and
three businesses requiring point-of-use treatment. Costs for
this sit~ation are the same as th9se developed for Alternative 4~
Costs for onsite treatment for containment purposes have
been estimated from a scale-up of the Phase I treatment system as
discussed under Alternative 5. The costs for this scenario are
based on containment in the middle sand unit. If a more
extensive groundwater extraction system, or pumping of the lower
sand or bedrock aquifers is determined to be necessary,
additional costs would be incurred.
A final worst-case scenario would involve installation of
both onsite and offsite treatment as described above. The costs
associated with the various scenarios developed for this
alternative are summarized below.
Caoital
Cost
Annual
o & M Cost
Net Present
Worth
Onsite and Offsite Monitoring
Offsite Treatment
Onsite Treatment
Both Onsite and Offsite
Treatment with Monitoring
$ 114,000
442,300
1,037,200
$101,800
. 65,600
458,500
$ 702,000
1,062,000
5,449,000
1,593,500
625,900
7,125,000
8.0 SUMMARY OP ~BE COKPARA~IVE ANALYSIS OF AL~ERNA~IVES
The following nine criteria,
C.F.R. ~ 300.430(e), 55 Fed. Reg.
in the evaluation of the remedial
Operable Unit Two at the Maryland
as set forth in the NCP, 40
8848, March 8, 1990, were used
action alternatives for
Sand, Gravel and Stone Site:
Threshold Criteria
1)
Overall protection of human
health and the environment;
and
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43
Table 11
Maryland Sand Gravel and Stone Site
Ooerable unit 2
SummarY at Maior ARARs
Action - Soecitic ARARs
I)
Hazardous Waste
Waste Disposal Requirements for Treatment Residues 40 C.F.R.
Part 261, including land disposal restrictions 40 C.F.R. Part 268
[applicable]
Corrective action program requirements in 40 C.F.R. Subpart
F, S 264.90-264.101 that address groundwater monitoring [relevant
and appropriate]
State of Maryland requirements contained in MD Code Ann. S
26.13.05.10 regarding tank standards; S 26.13.05.06 governing the
methodology of groundwater monitoring; and S 26.13.03 regarding
generators [relevant and appropriate]
II)
Water
National Pollutant Discharge Elimination System (NPDES)
requirements contained in 40 C.F.R. Parts 122 through 124*
[Applicable]
state of Maryl~nd requirements contained in MD Code Ann. S
26.08.01 pertaining to general requirements.associated with water
pollution control, S 26.08.02 pertaining to water quality .
standards, S 26.08.03 pertaining to discharge limitations, and ~
26.08.04 pertaining to discharge permits* [applicable]
III)
Air
state of Maryland requirements contained in MD Code Ann. ~
26.11.15 pertaining to toxic air pollutants* [applicable]
state of Maryland requirements contained in MD Code Ann. S
26.18.01, subsections .04 and .05 pertaining to testing,
monitoring and records; ~ 26.11.06 subsections .08 and .09
pertaining to nuisances and odors; and S 26.18.02*, subsections
.01 to .03 pertaining to permits and approvals [relevant and
appropriate]
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44
Table 11
(continued)
IV)
OSHA
Occupational Safety and Health Administration (OSHA)
requirements for workers at remedial action sites 29 C.F.R. Part
1910 [applicable]
V)
Transportation
U.S. Department of Transportation (DOT) Regulations, 49
C.F.R. Part 107, and 40 C.F.R. ~ 171.1 through 172.558
[applicable]
VI)
Well Construction
State of Maryland requirements contained., in MD Code Ann. ~
26.04.04 subsections .04 and .06 pertaining to. application and
issuance on well permits*; subsection .07 pertaining to
construction standards; and subsection .11 pertaining to
abandonment. [applicable] .
Chemical-SDecitic ARARs
'Maximum Contaminant Levels (MCLs) and non-zero Maximum
Contaminant Lev~l Goals (MCLGs) contained in 40 C.F.R. Parts 141
and 143 [relevant and appropriate]
Federal Ambient Water Quality criteria [relevant and
appropriate] .
'Location-SDecitic ARARs
Wetlands
EPA's policy set forth in 40 C.F.R. Part 6, Subpart A, for
carrying out the provisions of Executive Order 11990 (Protection
of Wetlands). [applicable]
..)-,'
* The substantive requirements of these sections will be
complied with. However, in accordance with Section 121(e) of
CERCLA, 42 U.S.C. ~ 9621(e), permits are not required for onsite
activities.
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Primary Balancing Criteria
Modifying criteria
45
2)
Compliance with applicable or
relevant and appropriate
requirements.
3)
4)
Long-term effectiveness and
permanence;
Reduction of toxicity,
mobility, or volume through
treatment;
Short-term effectiveness;
Implementability; and
Cost.
5)
6)
7)
8)
State/support agency
acceptance; and
Community acceptance.
9)
A brief description of each of these criteria is provided in
Table 12. .
Of the six alternatives developed for this Operable unit,
three fail to satisfy the threshold criteria identified above.
Alternative 1 (No Action), Alternative 2 (Onsite Groundwater
Monitoring), and Alternative 3 (Onsite artd Offsite Groundwater
Monitoring) would not be protective of human health and the
environment. These alternatives would do nothing to reduce
contaminant levels that currently exceed MCLs in at least one
well in the middle sand unit. These alternatives would not be
considered protective of human health and the environment since
they would allow the further migration of onsite contamination
into deeper portions of the aquifer and eventually offsite. This
would allow additional human exposure to contaminants associated
with this Site. .
. Since Alternatives 1, 2, and 3 failed to satisfy
threshold criteria they will not be discussed further
section. The remainder of the section will deal with
evaluation of Alternatives 4, 5 and 6 with respect to
evaluation criteria.
the
in this
the
the nine
Overall Protection of Human Health and the Environment -
Alternative 6 provides the best overall protection of human
health and the environment. Alternative 6 (Onsite and Offsite
Monitoring with Deferred Onsite and Offsite Treatment) offers
advantages over Alternative 5 (Onsite Monitoring with Deferred
Onsite Treatment). By providing for offsite monitoring and
offsite treatment, Alternative 6 contains a mechanism for moni-
toring pollutant levels offsite and provides a means to treat
contaminated groundwater that has moved offsite at the point of
use.
Alternative 6 also offers advantages over Alternative 4
(Onsite and Offsite Monitoring with Deferred Offsite Treatment)
by providing for the control of contaminants onsite. This
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46 .
Table 12
NINE EVALUATION CRITERIA
Overall Protection of Human Health and the Environment
addresses whether or not a remedy provides adequate protection
and describes how risks posed through each pathway are
eliminated, reduced or controlled through treatment, engineering
controls, or institutional controls.
Compliance
meet all of the
requirements of
and/or provides
with ARARs addresses whether or not a remedy will
applicable or relevant and appropriate
other Federal and state environmental statutes
grounds for invoking a waiver.
Lona-Term Effectiveness and Permanence refers to the ability
of a remedy 'to maintain reliable protection of human health and
the environment over time once cleanup goals have been aChieved..
Reduction of Toxicitv. Mobilitv or Volume refers to the
anticipated performance of the treatment technologies a remedy
may employ.
Short-Term Effectiveness addresses the period of time needed
to achieve protection, and any adverse impacts on human health
and the environment that may be posed during the construction and
implementation period until cleanup goals are achieved.
Im~lementability is the technical and administrative
feasibility of a remedy, including the availability of materials
and services needed to implement a particular option.
Cost includes estimated capital, operation and maintenance,
and net present worth costs.
State Acceotance indicates whether, based on its review of
the RI/FS and Proposed Plan, the State concurs with, opposes, or
has no comment on the preferred alternative.
Community Acceotance refers to the comments and/or concerns
expressed by interested persons during the public' comment period.
.' .
......'
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47
provides a, ~echanism for re~oving contaminan~s before they have
an opportun1ty to move offs1te and present r1sks to additional -
water users.
Comoliance with ARARS - Alternative 6 will comply with all
Federal and state ARARs associated with groundwater monitoring,
and onsite and offsite treatment. These are summarized in Table
11. Alternative 5 will comply with Federal and State ARARs
associated with onsite monitoring and onsite treatment, and
Alternative 4 would comply with requirements pertaining to
monitoring and offsite treatment.
Lona-Term Effectiveness and Permanence - The long-term
effectiveness of both the onsite and offsite treatment systems
should remain high throughout their period of operation. By
providing both on- and offsite treatment~ Alternative 6 offers
advantages over both Alternatives 4 and 5. Onsitetreatment will
provide for source control, while offsite treatment at affected
wells will ensure that risks associated with contaminants which
do.migrate offsite are effectively controlled.
- Alternative 5, while providing for onsite treatment, does
not provide a mechanism that will address offsite contamination
if it occurs. Although Alternative 4 does provide for offsite
treatment, the overall effectiveness of this alternative is
limited by not providing for onsite control/reduction of
contaminants.
Reduction in Toxicitv.Mobilitv or Volume - Alternative 6
provides the greatest reduction in the toxicity, mobility or
volume of contaminants associated with this site. The onsite
treatment aspect of this alternative will likely have the
greatest impact in reducing the mobility of the contaminants.
Both the onsite and the offsite treatment systems will be effec-
tive in treating the groundwater, and thus reducing ~oxicity.
since Alternative 6 employs both on and offsite treatment, the
degree of reduction in toxicity and/or mobility of contaminants
would be greater than either Alternative 4 or Alternative 5.
Short-Term Effectiveness - Alternatives 4 and 6, which include
provisions for offsite monitoring and point-of-use treatment,
provide the highest degree of short-term effectiveness. The
decision process for both these alternatives provides for
supplying bottled water to affected well owners immediately after
contamination from the site has been detected. Since no
contamination has as yet been detected in offsite wells, this'
provides for an expeditious means of reducing risks from
contaminated groundwater.
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48
Alternative 5, which provides for onsite
not provide adequate short-term effectiveness
pumping and treating contaminated groundwater
order to reduce risks to acceptable levels.
Imolementabilitv - The groundwater monitoring aspects of all
three alternatives would be carried out using proven technologies
and widely practiced techniques.
treatment, would
since years of.
may be required in
Offsite treatment which would be provided under Alternatives
4 and 6 would be accomplished using components (i.e., air
strippers, carbon adsorption, and ion exchange units) that have
been used extensively in business and industry for a variety of
water treatment needs. Thus, a system that is properly designed
for the contaminants detected should function reliably over its
expected useful life.. .
The design of the onsite treatment system, which would be
provided under Alternatives 5 and. 6, will be based on the results
of treatability studies. Once again, a properly designed system
,should be capable of treating the groundwater in order to achieve
the remedial action objectives established for this site.
As mentioned previously, the implementation. of onsite
groundwater treatment for this operable unit must be done in
concert with the treatment provided under Operable Unit One.
Otherwise, contaminants may be drawn into the middle sand unit
from the more heavily contaminated upper sand unit.
Cost - The capital, annual operation and maintenance, and present
worth costs for all six alternatives evaluated in the feasibility
study are summarized in Table 13.
State Acceotance - The state of Maryland concurs with EPA's
selection of Alternative 6 as described in Section 9.0 of this
ROD.
.'
Community Acceotance - Comments received during the public
comment period concerning the various alternatives are summarized
in the Responsiveness Su~ary which is a part of this ROD.
9.0
THE SELECTED REMEDY
Based upon consideration of the requirements of CERCLA, the
detailed evaluation of the alternatives, and public comments, EPA
has determined, and the State of Maryland has concurred that
Alternative 6 is the most appropriate remedy for the site.
Alternative 6 involves the use of an onsite and offsite
monitoring program. In addition, if indicated by monitoring
data, onsite treatment and/or offsite point-of-use treatment
would be provided.
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49
TABLB 13
Summary of Costs Associated with Remedial Alternatives
Maryland Sand. Gravel & Stone site
Operable Unit Two
Alternative
Cost (thousands of dollars)
CaDital QiM NPW ( a )
o 0 0
114 92 614
114 102 702
l-No Action
2-0nsite Groundwater
Monitoring
3-0nsite and Offsite
Groundwater Monitoring
4-0nsite and Offsite
Groundwater Monitoring
with Deferred Offsite
Point-of-Use Treatment
114(d)
556(e)
102(d)
167(e)
702 (d)
1,764(e)
5-0nsite Groundwater
Monitoring with Deferred
Onsite Groundwater
Treatment
114(b) 92(b) 614(b)
1,151(c) 551(c) 6,063(c)
114(b) (d) 102(b) (d) 702(b) (d)
556(b) (e) 167(b) (e) 1,764(b) (e)
1,151(c) (d) 560(c) (d) 6,063(c) (d)
1,594(C) (e) 626(c) (e) 7,125(c), (e)
6-0nsite and Offsite
Groundwater Monitoring
with Deferred Offsite and
Onsite Treatment
(a) Net present worth: evaluated at a 10%
(b) If onsite treatment is not necessary
(c) If onsite treatment is necessary
(d) If offsite treatment is not necessary
(e) If offsite treatment is necessary
discount rate for 30 years
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50
Based on comments received during the public comment period, EPA
has modified the action level that would "trigger" the
implementation of offsite treatment from that described in the
Section 7.6. As explained in Section 11.0, EPA has determined
that the action level for offsite treatment should include a
criterion for requiring action based on 10-5 rather than 10-4
carcinogenic risk as described in section 7.6.
Thus, action levels that would "trigger" the implementation
of offsite treatment have been defined as MCLs for those
contaminants for which these criteria exist, or a cumulative
carcinogenic risk in excess of 10.5, or a hazard index greater
than 1.0.
Action levels that would "trigger" the implementation of
onsite treatment have been defined as MCLs for ~hose contami-
nants for which these criteria exist, or a cumulative carcino-
genic risk in excess of 10-4, or a hazard index gr~ater than 1.0.
The cumulative risk and hazard index estimates shall include
all detected contaminants. The confirmed existence of any of the
above three conditions in either onsite or offsite wells would
trigger treatment in that location.
For offsite wells, detection of any of the contaminants of
concern during a particular monitoring period would require
immediate resampling of the affected well. Concurrently, bottled
water for drinking purposes would be made available to the
affected residence or business.
Following initial detection of contaminants at concen- .
trations in excess of either the onsite or offsite action levels,
confirmation sampling would take place. This second round of .
sampling would employ statistical analysis to confirm the
presence of contaminants at levels above the action levels. Once
it is confirmed that the action level has been exceeded, a
remedial action plan will be developed to provide treatment for
the nature and extent of the confirmed contamination.
The objective of this alternative is to reduce the con-
taminant concentration in the lower aquifers, both on and off-
site, to an acceptable risk level (i.e., carcinogenic risk 10-6
and Hazard Index ~ 1.0). In addition, an objective of the
selected alternative is the achievement of MCLs and non-zero
MCLGs at the point of compliance. The point of compliance will
be measured at all wells placed in the plume of contamination.
The time required to achieve the remedial action objectives
cannot be determined with any accuracy, and was not estimated.
It will be influenced by a number of factors, including the
effectiveness of the Phase I (upper sand) treatment system.
A more detailed description of the selected alternative is
provided in Section 7.6. It should be recognized that the action
levels for onsite and offsite treatment are those described in
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51
this section as opposed to Section 7.6. It should also be
recognized that minor changes to the selected alternative may be
made during design (e.g., location or number of wells). These
changes in general will reflect the usual modifications resulting
from the engineering process.
10.0
STATUTORY DETERMINATIONS
EPA's primary responsibility at Superfund sites is to
undertake remedial actions that are protective of human health
and the environment. In addition, Section 121 of CERCLA,
42 U.S C. S 9621, establishes several other statutory
requirements and preferences. These specify that when complete,
the selected remedial action for each site must comply with
applicable or relevant and appropriate environmental standards
established under federal and state environmental laws unless a
statutory waiver is granted. The selected remedy also must be
cost-effective and utilize treatment -technologies or resource
recovery technologies to the maximum extent practicable.
Finally, the statute includes a preference for remedies that
permanently and significantly reduce the volume, toxicity or
mobility of hazardous wastes. The following sections discuss how
the selected remedy for this Site meets these statutory
requirements.
Protection of Human Health and the Environment -The selected
remedy protects human health and the environment by controlling
exposure to contaminated groundwater associated with the Site.
Detection of constituents above the action levels in groundwater
onsite would trigger implementation of onsite groundwater
treatment. This will provide a mechanism for controlling the
migration of contaminants, as well as reducing the level of
contamination. If contamination is detected in residential wells
offsite, point-of-use treatment systems will provide the means
for controlling individual exposure to contaminated groundwater.
Together, the onsite and offsite monitoring program, coupled with
deferred onsite and/or offsite treatment, will be protective of
human health and the environment. There are no significant
short-term threats associated with the selected remedy. In
addition, no adverse cross media impacts are expected from
implementation of this remedy.
Attainment of Applicable or Relevant and Appropriate Reauirements
The selected remedy will attain all location, action and .
chemical-specific applicable or relevant and appropriate
requirements for the Site. The major federal and state ARARs
pertaining to the selected alternative are summarized in Table
11.
Cost Effectiveness - EPA believes and the state concurs that the
selected remedy is cost effective in mitigating the risk posed by
the contaminants associated with this operable unit. The staged
approach to monitoring, and both on and offsite treatment,
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52
represents a cost-effective approach to addressing current and
future ris~s associated with this portion of the Site.
utilization of Permanent Solutions Emplovina Alternative
Technologies to the Maximum Extent Practicable - The selected
remedy is the most appropriate solution for this operable u~it
and represents the maximum extent to which permanent solutions
and treatment can be practicably utilized.
Preference for Treatment - This preference is satisfied since
treatment is a principal element of the chosen alternative.
.11.0
DOCUMENTATION OF SIGNIFICANT CHANGES
The alternatives developed in the Feasibility Study (and as
described in Section 7.0), were based on action levels which
included a criterion of 10" for carcinogenic risk. The alter-
natives employed this criterion for both on and offsite wells.
When EPA issu~d the Proposed Plan to the'public for comment,
EPA proposed revising the carcinogenic risk criterion to 10'5 for
. both on-and offsite wells.
In response to comments received during the public comment
period, EPA has modified the selected remedy from that described
in the Proposed Plan. The selected remedy will emploj a
carcinogenic trigger criterion of 10" onsite, and 10' in offsite
wells.
The onsite trigger mechanism has been revised to 10" in
response to comments relatin~ to the cost/benefit of providing'
onsite treatment based on 10' carcinogenic risk. other consid-
erations included the fact that there are no onsite users of
groundwater, and that some degree of attenuation would be .
expected to occur as groundwater moves across the Site. EPA
continues to believe, however, that the offsite trigger must
remain at 10.5 to be protective of human health and the
environment.
.' .
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XarylueS SaneS Gravel' stone
Responsiveness summary
The following discussion summarizes the comments raised
during the public comment period for the Proposed Plan for
Operable Unit Two at the Maryland Sand, Gravel and Stone Site.
This responsiveness summary is divided into two sections. The
. first section describes the comments received at the public.
meeting that was held to present the Proposed Plan. The second
section summarizes the written comments received during the
public comment period.
I)
Public Meeting Comments
On June 5, 1990, EPA held a public information meeting to
present the Agency's proposed remedial plan for Operable unit Two
at the Site. Approximately 45 people attended the meeting, which
took place from 7:00 to 8:30 p.m. at the Cecil County Public
Library. Attending the meeting were representatives from the
community, local officials, businesses, news ".media, the Maryland
Department of the Environment and EPA. .
Representatives from EPA and the Maryland Department of the
Environment made a presentation that addressed: the history of
the Site, the current conditions at the Site, an explanation of
the Superfund process, a description of the remedial alternatives
that had been developed for Operable Unit Two, and EPA's proposed
alternative for Operable unit Two.
Following the presentation, there was. a question and answer
session. During this session, the majority of the questions were
requests to clarify or explain in greater detail certain aspects
of the conditions at the Site. For example, questions focused on
identifying the nature and extent of contamination found at the
Site, the rate at which groundwater moved under the Site, and
other activities taking place on the Site (e.g., drum removal).
Representatives from EPA and the Maryland Department of the
Environment responded to each of these points.
-,'
One commentor suggested that it might be less costly to
provide area residents with a centralized water system instead of
cleaning up the contaminated groundwater. While EPA agrees that
it may be less costly to provide a centralized water supply, this
would do nothing about remedying the contamination that exists at
the Site. EPA's preference for Alternative 6 was not based on
cost alone, but on the nine evaluation criteria in the NCP, 55
Fed. ~. 8848, March 8, 1990, to be codified at 40 C.F.R. ~
300.430(e) (9) (iii).
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II)
Written Comments
This section of the responsiveness summary addresses the
written comments received during the60-day public comment
period. Only one set of written comments was received during the
comment period. The comments are described below. .
By letter dated July 13, 1990, the Settling Parties under
the Consent Decree for the Phase I Record of Decision ("Settling
Parties") at the Site objected to EPA's revision to the risk
based action level described in the Phase II Feasibility Study.
The Settling Parties stated that the revisions to the risk based
action level has raised other technical issues relating to how
the action levels would be calculated, the method for determining
when the action levels have been reached, and what actions will
be taken if it is determined that the action levels have been
reached. The Settling Parties identified numerous technical
issues that they believe should be addressed by EPA before a
response action is selected. ..
The Settling Parties expressed a concern that improperly
installed monitoring wells may have caused contamination of the
lower aquifers. They objected to several of the applicable or
relevant and appropriate criteria (ARARs) that EPA identified
during the development of the Feasibility Study. The Settling
Parties also stated their belief that EPA's selection of
Alternative 6 was arbitrary and capricious, and identified
Alternative 5 as the preferred alternative for dealing with the
conditions associated with Operable Unit Two.
I .
The following discussion summarizes the main points raised
by the Settling Parties in their July 13, 1990, letter and.
explains how EPA has responded, or will respond, to these
concerns.
Revision to Risk Based Action Levels
The Settling Parties raised a number of issues relating to
EPA's decision to revise the carcinogenic risk based action level
that would require either onsite or offsite treatment from 10'4
to 10-5. The Settling Parties' comments included a summary of
some of the exchanges that went into the development of the risk
based action level that was ultimately included in the
Feasibility Study. This summary notes that there was significant
disagreement throughout the development of the Feasibility Study
as to the appropriate terms of the risk based action level (or
"trigger mechanism") . .
Although EPA directed the Settling Parties to incorporate a
10-4 trigger mechanism into the Final Feasibility Study, EPA
reconsidered its position with respect to the trigge~ mechanism,
and on May 15, 1990, issued a Proposed Plan for Operable Unit Two
that included a risk based action level for both onsite and
offsite remediation of 10-5. In their comments to the Proposed
2
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2)
Plan the Settling Parties objected to EPA's proposal to revise
the risk based action levels for a variety of reasons. The
Settling Parties' objections, and EPA's response to these
objections are summarized below.
1)
The Settling Parties argued that"EPA's revision to the risk-
based action level violated procedural requirements. The
Settling Parties believe they should have been afforded the
opportunity to exercise the dispute resolution provisions of
the Consent Order under which they prepared the RI/FS for
Operable unit Two. They believed that EPA's failure to
disapprove the Feasibility Study, which would have allowed
'them to invoke the dispute resolution provisions of the
Order (assuming the Respondents did not agree to incorporate
the revised trigger mechanism) violated the procedural
requirements relating to the Consent Order.
EPA ResDonse - The Settling Parties had already raised this
same point earlier and by letter dated May 30, 1990, EPA
responded to the Settling Parties' request to invoke the
dispute resolution provisions of the Order. In essence, the
conditions under which dispute resolution" could be invoked'
did not present themselves since EPA did not notify the
Settling Parties of a deficiency in the Feasibility Study.
EPA had no obligation to disapprove the Final Feasibility
Study or to issue a notice of deficiency. Rather, in an
effort to keep the project moving forward, EPA modified the
trigger mechanism contained in the Feasibility Study, and
incorporated the modified trigger in the Proposed Plan. As
explained to the Settling Parties at a meeting on June 28,
1990, (during the public comment period) one of the primary
functions.of issuing a Proposed Plan is to solicit comments
from all interested parties on all aspects of the proposed
alternative. Thus, EPA has not violated any of the ,-
procedural requirements of the Order, and the Settling"
Parties have been afforded the required opportunity to
comment on the revised risk based trigger, mechanism.
The Settling Parties commented that EPA had acted in an
arbitrary and capr~cious manner by identifying a risk-based
action level of 10. , when language in the Proposed Plan
stated "Remedial action is generally warranted at a site
when the calculated carcinogenic risk level exceeds
10.4".
EPA ResDonse - The statement that remedial ,action is
generally warranted when carcinogenic risks exceeds 10-4 was
included in the Proposed Plan as a means of identifying the
upper limit of EPA's acceptable risk range. The National
Oil and Hazardous Substances Contingency Plan (NCP), 55 Fed.
~. 8848, March 8, 1990, to be codified at 40 C.F.R.
~ 300.430(e) (2) (i) (A) (2), identifies the acceptable exposure
levels (risk range) as 10.' to 10-6. ' However, it also
specifies that EPA shall use the lower end of this ri~k
3
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3)
ranqe (i.e., 10-6) as the "point of departure". Thus EPA's
proposal to initiate remedial action that will reduce the
threat to public health when the risks are below the upper
end ot the risk ranqe (i.e., 10.4) is entirely consistent
with the NCP. EPA strongly believes its actions are
consistent with CERCLA and the NCP and are not arbitrary and
capricious. .
The Settling Parties commented that the quantitation limits
of several of the contaminants of concern at the site
support a 10.4 risk based action level. The Settlinq
Parties have cited a memorandum dated July 26, 1989, from
Roy L. Smith, Ph.D., an EPA toxicologist, which states in
part:
"To summarize our discussions last week on triggers,
I agreed that using a combined 10-6 risk level as a
trigger (as opposed to a clean-up goal) was too'
restrictive for this site. The reason for this is
that two contaminants of concern, 1,1-DCE and vinyl
chloride, are not detectable at the 10~6 level. To
initiate offsite and onsite groundwater cleanup, a
combined risk of 10.4 or hazard index of 1 is
justifiable."
The Settling Parties' position is that EPA's own
toxicologist has acknowledged that a remedial action trigger
of 10-4 is justifiable, and that a trigger of 10.6 is not
justifiable because certain contaminants of concern are not
detectable at the 10.6 level.
EPA Resoonse - As noted in the Proposed Plan, several
contaminants of concern at the Site cannot be quantified at
concentrations less than those equal to a risk of 10.4. On
the other hand, the majority of contaminants found at the
site can be quantified at concentrations that would be
equivalent to a risk of less than or equal to 10.6. EPA's
identification of 10.5 as an action level was consistent
with trying to minimize the risk of exposure to chemicals
from the Site~ Thus, althou~h the July 26, 1989, memorandum
cited above states that a 10. level is "justifiable"~ this
does not foreclose the Agency from finding that a 10. level
was necessary because of its obligation to protect public
health. In addition, the Settling Parties, as well as the
public at large, were informed of, and given an opportunity
to comment on, the proposed change in the Proposed Plan. '
EPA acknowledged in the Proposed Plan that not all
contaminants could be quantified down to the 10.5 risk
level, so as to not create a false impression for the
general public. While EPA established 10.5 as both the
onsite and offsite trigger mechanism in the Proposed Plan,
EPA recognized and wanted to make sure that the general
public understood that certain contaminants could not be
4
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5)
4)
quantified at that level. As mentioned previously, the
majority of the contamina~ts 'found at the Site can be
quantified down to the 10' level. Thus, although it would
have-been EPA's desire to quantify all contaminants of
concern at the 10'5 level, analytical limitations preclude
this from being possible for some contaminants at this time.
The Settling Parties commented that EPA failed to ass~ss
cost effectiveness, as required by CERCLA, when it revised
the risk based trigger in the Proposed Plan.
EPA ReSDonse - As noted in the Settling Parties' comments,
the Feasibility Study did include cost estimates for each of
the response alternatives. These cost estimates were based
on a number of assumptions, and it would be unreasonable to
think that the cost estimates in the Feasibility Study could
cover every conceivable future scenario. In fact, the costs
in the Feasibility Study for onsite treatment are based on
the limited pumping and treatment of groundwater from the
middle sand unit, where contamination was found in the area
of DMW-7. Obviously, additional costs would be incurred if.
it were determined that contamination had. migrated further'
into the lower aquifers.
EPA's revision to the risk based trigger would not affect
the overall ranking of the alternatives with respect to
cost, though it would have an impact on the time at which
the remedial action would have to be implemented, and thus
on the overall cost of the remedy. Thus, although the
trigger criteria will have an effect on when the remedial
action must begin, the main factor driving the overall
project costs is whether contaminants from the upper sand
unit migrate into the lower aquifers. .
.' .
In summary, EPA did consider cost when evaluating the six
alternatives developed in the Feasibility Study, and EPA's
selection of Alternative 6 was based on its belief that the
alternative achieves the best balance among the nine
evaluation criteria. The revision to the risk based trigger
did not change the overall ranking of the six alternatives
with respect to the selection criteria.
The Settling Parties commented that EPA's proposed revision
to the risk based trigger would increase the total cost of
the preferred alternative by $16 to $23 million dollars.
"
EPA ReSDonse - The Settling Parties calculation of
additional costs that would be incurred as a result of EPA's
revision to the risk based action level is grossly,
overestimated. The $16 to $23 million figure is based on a
straight-line scale-up of a relatively small system and does
not take into account the economies of scale associated with
either the construction or operation of a larger system.
5
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6)
Furthermore, the cost figures the Settlinq Parties cite
assume that qroundwater from both the lower sand and the
bedrock aquifers would require treatment immediately, and
that this treatment would continue for 30 years. Based on
the data in the remedial investigation, treatment of
groundwater in the lower sand and bedrock aquifers would not
currently be required under either the 10.4 or 10.5 trigger
mechanism. Thus, treatment of these lower aquifers would be
required only if additional contamination were to migrate
into these units. (Note that although the values summarized
in the Proposed Plan suggest that the risk in the lower sand
unit presently exceeds 1 x 10'5, this is the result of an
extremely conservative averaginq technique employed in the
risk assessment. EPA would employ a less conservative
approach in calculating the values to be used in its deter-
mination of the trigger mechanism.)
The Settling Parties commented that it is not cost effective
to spend $16 to $23 million to treat groundwater that. meets
"acceptable exposure standards" (i.e. within EPA's accept-
able risk range of 10.4 to 10.6), and that this expenditure
is excessive when compared to the minimal benefit that would
be achieved. ..
EPA Response - The response to the previous question
addressed EPA's position with respect to the accuracy of the
Settlinq Parties' cost estimate. The response to comment #2
in this section addressed EPA' s mandate to employ 10'6 as a .
point of departure in determining acceptable risks.
Nevertheless, EPA has reconsidered its position with respect
to the onsite trigger mechanism in view of the cost/benefit
argument presented by the Settling Parties.
Although EPA does not agree with the magnitude of the cost
estimates developed by Settling Parties, additional costs
would be incurred as a result of imilementing treatment in
an aquifer when the risk was at 10' as opposed to the 10'4
level. Since there are no users of onsite groundwater, and
some degree of attenuation would be expected to occur as
groundwater moves across the Site, EPA believes that the
establishment of 10-4 as the onsite trigger will result in a
remedy that is protective of human health and the environ-
ment. The offsite trigger, however, must remain at 10-5 to
also be protective of human health and the environment.
7)
The Settlin~ Parties commented that a risk based action
level of 10' cannot be substantively supported because
background concentrations of organics and inorganics at the
Site exceed 10'5. .
EPA ResDonse - There were a number of technical and logical
errors employed by the Settling Parties' consultant in
arrivinq at the conclusion that background carcinogenic risk
in the area of the site exceeds 10-5. This resulted in an
6
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erroneously high value for the risk associated with
background wells. For example, filtered and unfiltered lead
data were combined improperly resulting in high estimates of
carcinogenic risk due to lead. Methylene chloride is not a
contaminant of concern at the Site, and therefore should not
have been included in the background risk assessment. The
presence of high concentrations of insoluble bis(2-ethyl-
hexyl)phthalate (BEHP) suggests that the organic samples
were unfiltered. BEHP is unlikely to migrate in ground-
water, so its presence is probably an artifact of sampling
or analysis. .
More importantly, the concept of overall background risk is
really not an issue. In general, remedial actions do not
require any particular contaminant to be cleaned up below
background concentrations, but this determination is made on
a chemical by chemical basis for the particular compounds
found at a site. Therefore, the concept of a "background
risk" from all chemicals combined is not germane to the
remedial decision.
8)
The Settling Parties commen~ed that a provision of the. NCP,
55 ~. E&g. 8848, March 8, 1990, to be codified at 40
C.F.R. t 300.430(e) (2) (i) (D), e'stablishes a presumption that
cleanup levels more stringent than 10'5 are not required
unless cumulative risks at the site. exceed 10.4.
EPA Response - EPA disagrees with the settling Parties
interpretation of the cited provision of the NCP. That
provision provides direction for dealing with sites like the
Maryland Sand, .Gravel and Stone Site where multiple
contaminants are involved. The provision directs EPA to
ensure that risks at such sites are maintained within the
acceptable risk range of 10'4 to 10'6, again making specific
reference to the use of 10'6 risk level as the point of
departure. Thus, EPA maintains that its action to limit
risk to values below the upper end (10'4) of the acceptable
risk range are not inconsistent with the NCP.
9)
The Settling Parties commented that EPA cannot support a
risk based action level of 10-5 for the Site when based on
information developed by the Settling Parties' consultant,
the risk level associated with drinking water in the
Baltimore, Maryland and Denver, Colorado water supplies
currently exceeds 10'5.
As previously explained, EPA's action in establishing risk
based action levels for the Site are based on the NCP.
There is no provision in the NCP that provides for a
comparison of risk in public drinking water supplies.
."
As a point of explanation, however, the cancer risk from the
two public drinking water supplies cited by the Settling
Parties, as well as many other urban water supplies, are
7
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10}
1}
2}
elevated as a result of risk associated with exposure to
lead and trihalomethanes. The EPA Office of Drinking Water
,is aware of these risks, but allows them because: 1} Lead
leaches into water from pipes in the distribution system,
which are very costly to replace; and, 2} Trihalomethanes
are unavoidable by-products of disinfection, the benefit of
which is judged to outweigh the risk.
The Settling Parties commented that they have been unable to
locate any other CERCLA sites where EPA had selected a
remedy with action levels as stringent as 10.5, and referred
to an article by Travis, Richer et ale (Risk and
Regulation. Chemtech. Auaust 1987) which concluded, based on
a survey of several Federal Agencies, that "for small
populations impacts, regulatory action was never taken for
individual risk levels less than 10.4. II
EPA ResDonse - The action levels for the Site were based on
the conditions and chemicals associated with the site. EPA
developed them in accordance with the provisions of the NCP,
which does not include requirements for comparisons to other
sites, nor to surveys conducted by private parties. .
Technical Issues
The Settling Parties have raised a number of technical
issues that they believe must be addressed by EPA prior to
remedy selection. In general, the majority of the issues
raised in this category are technical concerns which are so
specific that they are dealt with properly during the
remedial design phase rather than as part of remedy
selection. Specific responses to the concerns raised by the
Settling Parties are summarized below:
The Settling Parties commented that several technical issues.
had to t~ resolved prior to the selection of the Phase II
remedy because of concerns related to the implementation of
the Phase I Remedy.
EPA Response - While it is correct that implementation of
the Phase II onsite groundwater treatment system must be
done in concert with the treatment provided under Operable
Unit One, there is nothing that would prevent implemen-
tation of the Phase I groundwater treatment system prior to
implementation (if determined to be necessary) of the Phase
II Treatment System. The Settling Parties who are party to
the Consent Decree for Operable Unit One have an obligation
to implement the Phase I remedy, notwithstanding a decision
on Operable Unit Two.
The Settling Parties commented that the assumptions and
methodologies used in the Endangerment Assessment for the
site are overly conservative when compared to other
Endangerment Assessments prepared for other Superfund sites.
8
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EPA ResDonse - The Endangerment ~ssessment, which we note as
being prepared by the Settling Parties' contractor,
contained assumptions and methodologies that were acceptable
to EPA. The change in the trigger mechanism which the
Settling Parties claim caused them to "reevaluate" the
assumptions and methodologies employed by their own
contractor, does not in EPA's view, warrant the development
of a new Endangerment Assessment for the Site.
Similarly, the settling Parties' comparison of the
Endangerment Assessment methodology employed at the Site to
~hose employed at other Superfund sites does not warrant
revising the existing Endangerment Assessment. The assump-
tions and methodologies that were employed by the Settling
Parties' contractor are still acceptable to EPA for the
purpose of remedy selection.
3)
The Settling Parties commented that certain aspects of the
Endangerment Assessment prepared for the Site are incon-
sistent with current EPA guidance.
4)
EPA Response - The Phase II Endangerment Assessment was
. prepared in accordance with the then-current EPA guidance.
As noted during our meeting with representatives of the
Settling Parties on June 28, 1990, EPA agrees that future
risk calculations should be done in-accordance with ~
Assessment Guidance for SUDerfund (RAGS) and the Excosure
Factors Handbook. The assumptions and the methodologies in
these documents can be used to calculate the risks for
determining whether the trigger mechanism has been exceeded
during th~ course of Remedial Design/Remedial Action
(RD/RA). EPA does not believe it is necessary, or
appropriate, to stop the process at this point for the sake
of incorporating a revised Endangerment Assessment into the
Remedial Investigation.
The Settling Parties raised a number of concerns relating to
the specific methodology that would be employed in
determining when the risk based action level has been
exceeded. They commented that in order to fully assess the
impact, including the economic repercussions of the risk
based action level, EPA must address each each of these
concerns prior to remedy selection.
.'
. ,~.
EPA Response - EPA does not believe that these concerns need
to be addressed prior to remedy selection. . These concerns
.relate to remedy implementation, rather than to remedy
selection. While the procedures used to determine whether
the action level has been exceeded, will have an effect on
overall project costs, determinations on each of these
points will not undermine the overall cost-effectiveness
analysis contained in the Feasibility Study. Final
decisions on many of the points raised by the Settling
Parties in this area will be made during the development of
9
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the remedial design work plan. However, the following
discussion summarizes EPA's current view on several of these
points:
statistical Acproach - EPA agrees that a statistical
approach should be employed to determine whether action
levels have been exceeded. The guidance contained in
statistical Analvsis of Ground-Water Monitorina at RCRA
Facilities (U.S. EPA, April 1989) may be used in developing
this approach.
Identification of Comcliance Wells - EPA agrees that the
selection of compliance wells can be deferred pending
collection of additional data and selection of a
statistical approach to groundwater monitoring. The data
the Settling Parties presented regarding the construction of
some of the onsite wells, suggests that proposed wells.
should be evaluated prior to making a determination to use a
particular well as a compliance point. Furthermore, the
statistical approach chosen to evaluate whether the risk
based action level has been exceeded will have an effect on
the number of monitoring wells needed in each water bearing
zone.
Dilution/Attenuation - The Settling Parties have suggested
utilizing dilution/attenuation factors for several calcu-
lations involved in the determination as to whether the risk
based action level has been exceeded. Presumably this
recommendation relates to their preference for selection of
Alternative 5 which only employs onsite monitoring and
treatment. In EPA's view there is no need to employ
dilution/attenuation factors in the implementation of
Alternative 6 since it employs direct measurements .at
specific compliance points. Further, given the complex
hydrology, it is uncertain if accurate dilution/attenuation
factors could be developed for the Site.
Confirmatory Sampling - EPA agrees that confirmation
sampling should be employed prior to implementing remedial
action. The procedures for evaluating the analytical
results from both the initial and the confirmation sampling
will be developed in the RD/RA work plan.
5)
The Settling Parties commented that an additional decision
point should be incorporated into the process for
determining when to implement groundwater treatment for
Operable unit Two at the Site. They believe that triggering
the action level should lead to a secondary decision. That
decision being to evaluate whether the particular .
contaminants that resulted in the action level being exceded
are less than either: (1) the concentrations identified as
acceptable cleanup levels at other Superfund sites; or, (2)
concentrations that are achievable using best demonstrated
available technology ("BOAT").
10
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7)
EPA ResDonse - Clean-up levels are established on a site
specific basis, and change according to our knowledge of the
effects that particular contaminants have on human health
and the environment. It would be entirely inappropriate to
base a decision as to whether remedial action was required
at the Maryland Sand, Gravel and Stone Site on a clean-up
level established at a different site.
With regard to the second proposal, the Settling Parties
have not cited a single specific example whereby BCAT tech-
nology could not achieve the 10-6 clean-up goal established
for the Site. At this point, EPA is not aware of any
situation where use of BCAT would preclude achievement of
the 10.6 clean-up goal for the contaminants found at this
Site.
6)
The Settling Parties commented that the groundwater
contamination discovered in the middle sand, lower sand, and
bedrock units may be the result of improperly installed
monitoring wells. The Settling Parties believe that the
contaminants discovered in these lower aquifers are simply
artifacts of improper well installation in the immediate
vicinity of the monitoring wells and are not indicative of
the true characteristics of water quality beneath the entire
Site. The Settling Parties commented that the scope and
nature of the required remediation may need to be directed
to ameliorate only the effects of the monitoring well
installation, as opposed to remediation of large areas of
the lower aquifers at the Site.
EPA ResDonse - The Settling Parties have presented
information that indicates discrepancies between the records
documenting the construction of some of the monitoring wells
installed during the Phase I Remedial Investigation and in
recent field observations. 0 The information presented is 0
insufficient to allow EPA to conclude that the contaminants'
found in the lower aquifers were artifacts of well construc-
tion. However, if during the implementation of the selected 0
alternative, it is determined that the contamination is in
fact limited in scope, as suggested by the Settling Parties,
then the remedial action would be designed to deal with only
that localized contamination rather than remediation of the
entire aquifer. It should be noted, as in the case of
CMW-7, that it may be necessary to install additional
monitoring wells in order to ascertain the localized extent
of contamination detected in any of the proposed monitoring
wells. .
.00
The Settling Parties disagreed with EPA's determination
concerning applicable or relevant and appropriate require-
ments (ARARs) that must be complied with during implemen-
tation of the selected alternative. In particular, the
Settling Parties asserted that such requirements that-would
apply only during the course of the clean-up are not appli-
11
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cable or relevant and appropriate. The Settling Parties
commented that based upon section 121(d) (2) (A) of CERCLA, 42
U.S.C. S 9621(d) (2)(A), ARARs are supposed to be substantive
standards that apply "with respect to any hazardous
substance, pollutant or contaminant that will remain onsite
. . . at the completion of the Remedial Action".
EPA ReSDonse - The Settling Parties have raised this issue
previously, and by letter dated October 30, 1989, EPA
summarized our position as to why it was necessary to comply
with ARARs during the implementation of the remedy. The NCP
was finalized following the issuance of our October 30, 1989
letter, and it contains a specific provision requiring
compliance with ARARs during the course of RD/RA (See 55
~. ~. 8852, March 8, 1990, to be codified at 40 C.F.R.
S 300.435(b) (2).
8)
The Settling Parties do not believe that theRCRA land
disposal restrictions under 40 C.F.R. Part 268 are appli-
cable or relevant and appropriate to the Phase II remedy at
the Site because the treatment of contaminated groundwater
and the subsequent recharge of such treated water to
groundwater does not constitute the "placement of hazardous
waste into land disposal units" as required for the land
disposal requirements to apply.
9)
EPA Response - EPA's "contained in" RCRA policy triggers the
requirement to handle and treat the contaminated groundwater
from the site as a hazardous waste. Contaminated ground- .
water that has been treated to remove hazardous constituents
to below health based levels is no longer considered a
hazardous waste, and therefore, discharge of such treated
water to a recharge point would not constitute "placement"
of a hazardous waste under the land disposal restri9tions.
Treatment residues resulting from the groundwater treatment
process will "contain" hazardous constituents and the l~nd
disposal restrictions will apply to their dispo~al. -
The Settling Parties commented that because the Site did not
receive wastes after July 26,1982, See 40 C.F.R. S
264.90(a) (2), the only RCRA corrective action provision that
is "arguably applicable or appropriate is 40 C.F.R. S
264.101, which allows for onsite remedial measures to be
decided on a case-by-case basis".
EPA Response - By letter dated March 2, 1990, EPA identified
the ARAR's associated with the remedial action for Operable
Unit Two. This listing included the identification of the
corrective action program requirements in 40 C.F.R. S 264..90
- .101 as being relevant and appropriate to the remedial
action. These requirements were cited as relevant and
appropriate, rather than applicable, primarily because
12
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10)
11)
12)
of the date the wastes were disposed ot at the' Site. EPA
continues to believe that these requirements are relevant
and appropriate for the selected remedy. .
- .
The settling Parties commented that the requirements of the
National Pollutant Discharge Elimination System ("NPDES")
regulations, 40 C.F.R. Parts 122-124, are only applicable or
appropriate to regulate direct discharges from a point
source to surface waters of the united states. Thus, the
NPDES regulations should only be applicable to the extent
that there is a discharge from the groundwater treatment
facility into Mill Creek.
EPA ReSDonse - EPA agrees that these requirements would only
be applicable to a direct discharge to Mill Creek.
The Settling Parties stated that Maximum Contaminant Levels
("MCL's") should be the "initial clean~up goals" for'
groundwater that is to be used for drinking water. They
further stated that when restoration of the groundwater to
MCL standards is not practicable, alternative achievable
concentration limits or background levels should be the
designated clean-up standard. .
EPA Response - As noted in the Record of Decision, the
overall clean-up goal, once remedial action has been
triggered, is to reduce the risks associated with the
groundwater to acceptable levels (i.e. 10.6 carcinogenic risk
and Hazard Index <1.0). Clean-up goals for individual
compounds include MCL's and non-zero Maximum Contaminant
Level Goals (MCLG's) for those compound for which these
criteria exist. If it is determined that these goals are
not achievable, EPA may establish alternative clean-up
standards.
The settling Parties commented that they did not believe
that Maryland requirements regarding tank standards,
groundwater monitoring and generators (Md. Code Ann. S
26.13.05.10, 26.13.03 and 26.13.05.06), are applicable or
relevant and appropriate. They stated that since Maryland
does not recognize EPA's "contained in" policy, the'
groundwater which is the subject of the Phase II Feasibility
study, is not a hazardous waste under Maryland's regulatory
scheme and thus these regulations are not applicable or
appropriate to the contemplated remedy.
EPA ReSDonse - As noted in the State of Maryland1s September
10, 1990, letter from Kathy M. Kinsey, Assistant Attorney
General to EPA, the state agrees that its position with
respect to EPAls "contained in" policy results in the
determination that these requirements are not applicable.
13
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However, as outlined in their letter, the State has
deterained that these requirements are relevant and
appropriate.
As noted in EPA's March 2, 1990, letter to Dr. Paul Krueger,
EPA'8 position is that these requirements are, at a minimum,
relevant and appropriate and compliance with these require-
ments must be achieved.
13)
The Settling Parties commented that they do not believe that
. Maryland's toxic water criteria and discharge regulations
(Md. Code Ann. S S 26.08.01, 26.08.02, and 26.08.04) should
be applicable or relevant and appropriate because these
regulations are primarily oriented towards surface waters,
as opposed to groundwater which is the subject of the Phase
IX activities. The Settling Parties also commented that
since these regulations did not become effective until after
the Feasibility Study was completed, neither the settling
Parties nor EPA anticipated incorporation of these standards
into the Feasibility study. .
EPA Response - Like the Federal NPDES regulations, the cited
State requirements apply to that portion of the remedy
relating to discharge of treated groundwater. These
regulations are applicable due to the fact that there is a
discharge involved with the selected remedy. The fact that
groundwater, rather than surface water is being treated has
little bearing on the applicability of these requirements.
With regard to the timing issue, EPA identified these
requirements as being applicable prior to the issuance of
this ROD. The NCP, 55 I.!s1. ~. 8757, March 8, 1990, to be
codified at 40 C.F.R. S 300.430(f) (1) (ii) (B), expressly
provides for compliance with all modified or newly
promulgated ARARs in effect prior to the time the ROD is
signed.
Preferred ~lternative
The settling Parties commented that EPA's preference for
Remedial Alternative 6, is arbitrary and capricious because
Alternative 5 meets all the criteria that EPA uses to
evaluate alternatives and is less costly than Alternative 6.
Thus, Alternative 5 is the most cost-effective remedy for
Phase II.
EPA Res~onse - As more fully explained in Section 8.0 of
this ROD, EPA's selection of Alternative 6 was based on an
analysis of the alternatives developed for this operable
unit against the nine evaluation criteria identified in the
NCP. .
14
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EPA believes that Alternative 6 offers distinct advantages
over Alternative 5. While it is true that Alternative 6
will be slightly more complicated to implement, since it
involves the cooperation of offsite parties, this dis-
advantage is far outweighed by the fact that Alternative 6
puts in place a mechanism to deal with contamination that is
found in offsite wells. For a relatively small amount of
additional cost, Alternative 6 provide a means to monitor
offsite wells. Costs associated with offsite treatment
would be incurred only if contamination is actually detected
. in offsite wells. While we recognize that offsite
contamination has not been detected to date, EPA believes
-that the additional investment for offsite monitoring (and
treatment, if required) is justified when compared to the
overall protection of human health and the environment that
this alternative offers over Alternative 5.
In summary, EPA's selection of Alternative 6 was based on
the nine evaluation criteria identified in the NCP. Thus
EPA's selection of Alternative 6 is not arbitrary an
capricious.
-,
15
" ..
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o/tda~
DEPARTMENT OF THE ENVIRONMENT
2500 Broening Highway, Bahimore, Maryland 21224
Area Code 301 . 631-
WIlliam Donald Scheef.r
Governor
Martin W. WII.", Jr.
Secretary
september 26, 1990
Mr. Thomas C. Voltaggio
Acting Division Director (3HWOO)
Hazardous Waste Management Division
u.s. Environmental Protection Agency
Region III
841 Chestnut Building
Philadelphia, Pennsylvania 19107
Dear Mr. Voltaggio:
The Hazardous and Solid Waste Management Administration
(HSWMA) has completed its review of the Record of Decision for
Operable Unit II at the Maryland Sand Gravel and stone Site. HSWMA
concurs with EPAs selected remedy, Alternative six which requires
onsite and off-site groundwater monitoring with deferred off-site
and onsite treatment, if necessary.
We also concur with EPAs modification to one action level in
the selected remedy which would "trigger" implementation of pumping
and treatment operations. We understand that this modification has
resulted in a c~ulative carcinogenic risk of 10.4 for onsite.
locations and 10. for off-site locations.
','
In addition to concurring with the selected remedy for
Operable Unit II, we request that EPA expedite the implementation
of the F0CU88ed Feasibility Study (FFS) for Operable Unit III. The
continued presence of the sludge and contaminated soils will have
an impact on the selected remedies for Operable Units I and II
until they are removed.
-------
Mr. Thomas C. Voltaqqio
Paqe 2
We look forward to continuinq our cooperative relationship
with EPA on this project as we implement remediation at this site.
Sincerely,
1<
-A-~
Ronald Nelson, Director
Hazardous and Solid Waste
Management Administration
RN: kl j
cc:
Dr. virqina Bailey
Mr. Harold L. Dye, Jr.
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