PB94.-964101
EPA/ROD/R05-94/247
July 1994
EPA Superfund
Record of Decision:
Perham Arsenic Burial Site,
Per ham, MN
-------
-
DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Perham Arsenic Burial Site
Perham, Minnesota
STATEMENT OF BASIS AND PURPOSE
This decision qqcument presents the selected remedial action for
the Perham Arsenic Burial Site, in Perham, Minnesota, chosen in
accordance with the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA), as amended by
the Superfund Amendments and Reauthorization Act of 1986 (SARA),
the Minnesota Environmental Response and Liability Act of 1990
(MERLA), and, to the extent practicable, the National Contingency
Plan (NCP). The decision is based on the Administrative Record
for the Perham Arsenic Burial Site. The attached index
identifies the items which comprise the administrative record
upon which the selection of the remedial action is based.
The State of Minnesota has been consulted and concurs with the
selected remedial action.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this
site, if not addressed by implementing the remedial action
selected in this Record of Decision, may present an imminent and
substantial endangerment to public health, welfare, or the
environment.
DESCRIPTION OF SELECTED REMEDY
The selected remedial action for the Perham Arsenic Burial Site
addresses the source of the contamination by remediation of
groundwater. The major components of the selected remedial
action include:
*
Institutional Controls
*
Recovery Wells
*
Filtration
*
Alumina Adsorption
*
Infiltration Gallery
*
Municipal Water to Resident
-------
"~
STATUTORY DETERMINATIONS
Consistent with CERCLA and, to the extent practicable, the NCP, 40
C.F.R. Part 300, the selected remedial action 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 ~ction, and is cost-effective. The
remedy utilizes permanent solutions and alternative treatment
technologies to the maximum extent practicable and satisfies the
statutory preference for remedies that employ"treatment and reduces
toxicity, mobility, or volume as a principal element. Because"this
remedy will result in hazardous substances remaining on site above
heal th based levels, the five year review will apply to this
action.
J'\'\1~j) ~
~ Valdas V. Adamkus
Regional Administrator
3 - ~ I - 't LI
Date
~
-------
T:ITLE
I.
II.
III.
IV.
V.
VI.
VII.
.,
TABLE 01' CONTBll'1'S
PAGB _0.
SITE NAME, LOCATION AND DESCRIPTION.................. 1
SITE HISTORY AND ENFORCEMENT ACTrvITIES.............. 1
COMMUNITY RELATIONS HISTORY.......................... 6
SCOPE AND ROLE OF REMEDIAL ACTrvITIES................ 7
SUMMARY OF SITE CHARACTERISTICS...................... 8
SUMMARY OF SITE
RISKS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
VI:II. SOMMARY OF THE COMPARATIVE ANALYS:IS OF ALTERNATIVES... 24
DESCRIPTION OF
ALTERN'ATI'VES. . . . . . . . . . . . . . . . . . . . . . . . . . . 18
IX.
XI.
TIlE SEI.EC'I'ED R,EM:EDY................................... 27
STATUTORY DETERMINATIONS .............................28
i
-------
PIGtJRB .0.
FIGURE 1
FIGURE 2
FIGURE 3
FIGURE 4
FIGURE 5
FIGURE 6
FIGURE 7
.~
LIST OP PIGtJRBS
TITLB
SITE LOCATION MAP
LOCATION OF ARSENIC BURIAL PIT
ARSENIC ISOCONCEN!l'RATION MAP-SHALLOW
ARSENIC ISOCONCENTRATION MAP-DEEP
STRATIGRAPGHIC SEQUENCE
CONCEPTUAL PLAN OF TREATMENT-ALTERNATIVE 2
CONCEPTUAL PLAN OF TREATMENT-ALTERNATIVE 3
ii
PAGB .0.
2
3
9
10
12
20
22
-------
.~
LIS'l' OP 'l'ABLES
'l'ABLB HO. 'l'I'l'LE PAGB HO.
TABLE 1 TOXIC EFFECTS FOR CHEMICALS OF CONCERN lS
TABLE 2 TOXICITY VALUES FOR CHEMICALS OF CONCERN 16
TABLE 3 SUMMARY OF RISK AND HAZARD CALCULATIONS 17
.
TABLE 4 COST SUMMARY FOR AJ.TERNATIVE 2 21
TABLE S COST SUMMARY FOR ALTERNATIVE 3 23
.
ill
-------
AftACB1IDJ'1' 110.
ATTACHMENT 1
ATTACHMENT 2
ATTACHMENT 3
.... . .....'
LIST 01' AftAClDlDl'rS
MPCA LE'!-,l'J:;R OF CONCURRENCE
RESPONSIVENESS SUMMARY
INDEX OF THE ADMINISTRATIVE RECORD
~
iv
-------
-
DECISION SUMMARY
SITE NAME, LOCATION AND DESCRIPTION
I.
The Perham Arsenic Burial Site is located in the southwest corner
of the East Otter Tail County Fairgrounds in Perham, Minnesota.
The City of Perham is an agricultural-based village in north-
western Minnesota with a population of 2,086. (See Figure 1).
The East Otter Tail County Fairgrounds was used as a mixing
station and as a depository for pure (unmixed) lead arsenate and
unused arsenic-based grasshopper bait. In 1947, pure lead
arsenate and unused arsenic-based grasshopper bait were buried in
a shallow pit in the southwest corner of the fairgrounds. (See
Figure 2). The shallow pit area, and associated groundwater
plume which emanated from the pit area, are considered the Perham
Arsenic Burial Site (site). Adjacent fairground properties are
used for community and recreational purposes.
The topography around site is flat and gently slopes eastward
toward the Otter Tail River which is approximately 1.8 miles to
the east. The site surface consists largely of open, grassy
fields and dirt roads. Several brick, wood, and aluminum
buildings exist on the site. Subsurface features under the site
are characterized by a massive unit of glacial outwash sands and
gravel. In the Perham vicinity, a confining clay unit is
reported to exist within the glacial overburden, however, the
confining clay unit was not encountered during drilling at the
Perham site.
Groundwater in the vicinity of the site flows in an east to
southeast direction towards the Otter Tail River.
The City of Perham uses a municipal well system to supply
residents with potable water. A total of four municipal wells
are used to supply residential and commercial demands. Two wells
are located in the southern section of the city limits,
approximately 1/2 mile due west (hydraulically upgradient with
respect to groundwater) of the site. Two additional municipal
wells are located to the north approximately 1/2 to 3/4 miles
from the site. At the current operating conditions, the municipal
well system is not expected to influence contaminant migration at
the site.
II. SITE HISTORY AND ENFORCEMENT ACTIVITY
During the grasshopper infestation of the 1930s and 1940s, the
u.S. Department of Agriculture distributed lead arsenate to be
used as grasshopper bait to several counties in the state of
Minnesota. Technical grade lead arsenate was mixed with sawdust
and molasses to form the grasshopper bait. The bait was
dispersed around farm fields to prevent crop loss. The East
Otter Tail County Fairgrounds in Perham, Minnesota was a mixing
-------
-.
-- .
-
2
o
-- ,
.
:uMMMGU I.OC&'OI
'p
~. :I I
~ ~~ . ~ I I
E IU'~~' . A - i M ,
'. - -"'~ ;- ~'s......~.... I!
tM ....., ,Jar.. --~.~-_...-!'"
~I""'"""'" .~. . ..:.. "::..'~/ ..J"
.~: .~. ..L ... .......~:~ :'8f"8 .8 ;,.. .
:"~- ~ ... ..' .-.,.....'.Y ..,
.. 8... .. ,--' ....... ". ....;. ...~ ..Y .... t
.. .... ........ .,. .. ~.~ '.""..-/..''''YI' ~.
.. -."'. eo .. .. ... .. '. ",.. .X ...--.,
.. .. .... :.:..:.~.. :.... :..~J.:.,...~..;;tI ..:; .... .
".-.,. ,,--.... .......'" ......
.,.,""'''''..'' .......,. .,.~. '.. .
.th.~.::.'~..:' ~ .." ..:-..:.+."'...
.. --. .....:.,~.....~.". ...:..'. e...- .
;( p..,.t -...... .... '. ,- .. ......
. - ,.... ..'" ...... , .. ......
.....,.. 0." ..." -, "~.J '." ... .1 ..
..: 8. .. ... ..:.. tie.... ~.. #:.. .... ...
'I~................':': ........ ... :~. :.",~..A.~t~ ......;. ....;,..: ..
.. .. .. _=8,.- ~.... / _.8 . .... 8. .. '"
.. ... .-... ...~..... , .... fI!M-.... \;
.8 .. .. , .::... .. ..~.....~~..~ . ~ Pe~--
.. ~:... 'r::-. ,,~fI.""'-':'.. i""~ ... I""IUUII
. ...~.. .....~._.~~...~~.:.~/~,~~ '~
~.. . . ,/. .8J:.. . 8_~:" ~....,") .......
..... ... ~ . .. it'" . . ~
.. .-. .. .# '.,.......
.. . .,- I .- ~
.- , ....'
.. .-, .If""" . "'
. ~
'...
".
- .
...................
-..
....
SOURCE: U.s.a.s. PERHAM, UN-OTTER TAIL CO.
7.S MINUtE SERIES PHOTORE\1SED 1973
SCALE
1: 24000
t
o
, 1&1
-
~
o
i
sa:....r
,-nn
,~
I
'aDO 0
-=-=-
,
-
1~
-
.5
-+
.
FIGURE 1
SITE LOCATION
MAP
PERHAN ARSENIC BURIAL SI'TE
.......... ..
-------
d
"
~
".- ,
~
..
(
.
I
I
".
\
"-
'-
"[8-1
/
. / '
. .' ,.
Of ncr
i "- "_AS
I w{ll
I
I
.----
-.
~--'-
-" -------
'J1';5
I..
BLACK IOJ' ROAO/PAA1C..C
M(W-'A
U(JAl
8UI.OING
IIA"..[R.S CONSIRUCIKIN
W[ tAL BUIlDING
,/"/
,/"/'
/'
rRMI[
IIUIU*C
----
---
JCf-' ~
'C'-IA~ '+
'365-...... ~
acJAl
8UUJlNC
- - ._--~-~~,-~-;--l~-~---~
+
U( w - 9
o
SCAU ,. - .so.
0 85 30 10
-----
-----
---I fo---
Do 0
-1---4-
.,,-~,...........
~~L"')
~~
"""'-"'"'""'-""'.
"-....,,-"'-'
-500-
---
c:::
l£GEND
J
PA'4D ROAD
,",AVO !lOAD
au(,"
8UILDINC
f'(NC[
~
W[ 011 POND
WARSH (SWAMP)
nl([S
BRUSH. SHRUBS
INOD CONJOUR
N1'[RU[DlAI( COH1OU11
II[f'R(SSION CONtOUR
nnD IUYATION
Plomlt IltIMlIOM
MOCHI . DJOY
MONI'OItINC W[U
.... em ~
....,ORN: W[U
MOCAU' . (1JO'(
SOIl IIORINC
rI'8'
.u
.. MEW - .
+ fet - S
.
UII-J
GlOII08WI[/
CLAy eN'
AR5[NIC PI'
M:~ MnCAU 81 8IIDY
:W~
...
-------
-
4
station for the arsenic-laden grasshopper bait. In 1947, lead
arsenate and unused grasshopper bait were buried in a shallow pit
in the southwest corner of the fairgrounds. It is reported that
between 200 and 2,500 pounds of grasshopper bait containing over
50 pounds of technical grade lead arsenate is thought to have
been buried in the pit in burlap bags, wood or other decomposable
material.
Groundwater samples from monitoring wells have
quarterly or semi-annually since 1980 by state
agencies. Analytical data does not indicate a
decrease nor inc~ease in arsenic concentration
monitoring began.
been collected
and federal
significant
levels since
The following is a chronological summary of the history of the
Perham Arsenic Burial Site, including site investigation and
remedial activities.
1931:
1932:
1936-
1947:
1947:
1971:
1972:
The Grasshopper Control Campaign Committee was founded
by the Minnesota Department of Agriculture, University
of Minnesota Agricultural Extension Service and State
Entomologist.
Five hundred railroad cars of arsenic bait were
delivered to 55 of Minnesota's 87 counties.
The U.S. Congress spent $27.3 million on grasshopper
control, $1.9 million of which was spent in Minnesota.
Grasshopper control was terminated. Remaining lead
arsenate and remaining arsenic bait were buried in the
southwestern corner of the fairgrounds in Perham. It
is estimated that approximately 200 to 2,500 pounds of
grasshopper bait containing over 50 pounds of technical
grade arsenic were buried in the pit.
Hammers Construction Company purchased land from the
City of Perham and erected an office and a construction
warehouse, adjacent to the arsenic pit.
In May, a 31-foot deep, 1.25-inch I.D. galvanized steel
well was installed for Hammers Construction Company.
In June, eleven employees became sick as a result of
drinking water from the well. Two employees suffered
permanent effects.
In July, water samples were collected for arsenic
analysis from Hammers' well, seven private wells that
were within 120 to 1000 feet of Hammers' building, and
three municipal wells within 1/2 mile of the site. The
maximum arsenic concentration found in Hammers' well
-------
1974:
1980:
1982:
1983:
1984:
.,
5
was 11,800 parts per billion (ppb). The well was
capped and city water was extended to the building.
In August, the Minnesota Department of Agriculture
collected soil samples at the burial site. Analytical
results detected arsenic concentrations up to 12,600
parts per million (ppm).
In October, the Minnesota Department of Agriculture
collected additional soil samples at the site to
further define the extent of buried arsenic.
Minnesota Department of Health continued a semi-annual
groundwater sampling program for private and municipal
wells within the site's vicinity.
In September, U.S. EPA began soil sampling and
monitoring well installation. The investigation
discovered that arsenic-contaminated groundwater
extended approximately 600 feet downgradient (east) of
the burial pit on the fairgrounds. Elevated levels of
soil contamination were found in a 15 by 40 foot area
just north of Hammers Construction Company's property
and well.
The burial pit was capped with a clay cover to reduce
the amount of rainwater infiltration thus reducing
leaching of the arsenic.
The Minnesota Pollution Control Agency (MPCA) issued a
Request for Response Action (RFRA) to East Otter Tail
County Fairboard and the City of Perham. The site was
included on the MPCA's Permanent List of Priorities and
on the U.S. EPA's National Priorities List (NPL).
MPCA completed the first Remedial Investigation/
Feasibility Study (RI/FS) for the site. In 1984 the
following remedial action was proposed, and in 1985, it
was implemented.
1.
Excavation of approximately 200 cubic yards of
arsenic wastes and contaminated soils containing
greater than 500 ppm, with subsequent disposal at
an approved hazardous waste disposal facility.
Backfilling the excavated pit with clean fill
material.
2.
3.
Reestablishment of the clay cap and impermeable
membrane to minimize leaching of any residual
arsenic.
-------
-
6
4 .
Continuation of groundwater monitoring until
levels of arsenic in the monitoring wells fell
below the federal drinking water maximum
contaminant level (MCL) of 50 micrograms per liter
(ug/L) .
1989:
After completion of this
groundwater was expected
monitoring has continued
present.
The Agency for Toxic Substances and Disease Registry,
U.S. Public Health Service, conducted a Health
Assessment for the site and recommended post-remedial
sampling of the groundwater to define the extent of the
arsenic plume.
initial remedial action
to attenuate. Groundwater
on a semi-annual basis to the
Because arsenic concentrations in groundwate'r have not
significantly decreased, as assumed at the time of the
1985 remedial action, the EPA developed a RI/FS Work
Plan to define the extent of the arsenic plume, and
determine whether residual soil contamination remained.
1992/
1993
EPA conducted a two phase RI of the site, which
included the installation of twenty-five (25)
monitoring wells and twelve (12) soil borings.
The Potentially Responsible Party (PRP) search for the site
listed several persons and entities who could have exposure
CERCLA 107. However, to date, no general or special notice
letters have been issued.
under
III. COMMUNITY RELATIONS HISTORY
Since the discovery of arsenic in Hammers' well, the Perham
Arsenic Burial site has been a topic of conversation for the
citizens of Perham. Citizens of Perham, members of Perham's
municipal government, and civic organizations in Perham were
active in lobbying the state legislature for passage of a
Superfund law.
U.S. EPA and MPCA have kept Perham residents informed of all
developments at the site. News releases, news media contact, and
meetings have provided the community with information of various
remedial events throughout the clean up process. Investigations
regarding soil contamination were discussed with city staff and
officials, and members of the Arsenic Action Committee on October
11, 1983. When the investigation commenced, MPCA issued a news
release on the project, and members of MPCA staff were
interviewed by local reporters. The City of Perham newspaper,
The Enterprise Bulletin, provided frequent coverage of MPCA's
progress.
-------
..... - ......
7
At the conclusion of the first RI/FS in 1984, MPCA held a public
meeting to discuss investigation results and invite comments on
the proposed remedy to clean up soils. On July 19, 1984,
approximately 30 people attended the meeting at which MPCA, U.S.
EPA, and MPCA's contractors presented information and responded
to questions. The meeting was covered by regional as well as
local news media. Fact sheets outlining the results of the RI/FS
and the Minnesota Superfund were available at the meeting.
On March 31, 1992, U.S. EPA and MPCA personnel visited Perham to
meet with the city manager, city engineer, school district
members, county fair board members, newspaper editor, and
adjacent property owners. During the meetings attendees were
informed of the upcoming investigation and the rationale for it.
Also, a tentative schedule for completion of the RI/FS, Proposed
Plan, public meeting, and Record of Decision was discussed.
Meetings with various city and private personnel were held in
July 1992, February 1993, and January 1994. An RI Fact sheet was
issued explaining the findings of the investigation in January
1994.
Following completion of the second RI/FS in 1994, the U.S. EPA
published a Proposed Plan for remedial action, on February 15,
1994. The RI/FS Report, Proposed Plan for remedial action and
the Administrative Record, have been placed in an Information
Repository located at the Perham Public Library, 100 3rd Street
NE, Perham, Minnesota. Consistent with Section 113 of CERCLA,
the Administrative Record includes all documents such as the work
plan, data analyses, public comments, transcripts, and other
relevant information used in developing remedial alternatives for
the site. These documents were made available for public review
and copying at the Perham Public Library.
To encourage public participation in the remedy selection
process, consistent with Section 117 of CERCLA, the U.S. EPA set
a 30 day public comment period from February 15, through March
16, 1994, on the Proposed Plan. A Public Meeting was held on
February 22, 1994, to answer questions regarding the Proposed
Plan and to accept verbal public comment on the Proposed Plan.
Interested parties provided comments on the alternatives
presented in the Proposed Plan and elaborated upon in the FS.
The remedy for the Perham site described herein was selected
after a detailed review of public comments received. The
attached Responsiveness Summary addresses those public comments
received.
IV.
SCOPE AND ROLE OF REMEDIAL ACTIVITIES
In 1985, the first remedial action for the site was implemented.
Approximately 200 cubic yards of arsenic wastes and contaminated
soils were excavated and disposed of at an approved hazardous
waste disposal facility. The excavated pit was backfilled with
clean fill material. A clay cap and impermeable membrane to
minimize leaching of any residual arsenic was installed.
Groundwater monitoring was implemented and scheduled to continue
-------
-
8
until levels of arsenic in the monitoring wells fell below the
MCL.
Because the source of arsenic contamination had been removed and
surface water infiltration into the pit area was limited, the
arsenic plume was expected to eventually dissipate. Groundwater
samples, which have been collected twice a year since 1984, show
that arsenic contamination has not decreased significantly since
that time. '
The RI/FS conducted in 1992/1993 was designed to determine the
present extent and movement of arsenic contamination in the
groundwater and whether residual levels of arsenic contamination
were present in the soil. The 1992/1993 RI/FS concluded that
arsenic is present in the groundwater at concentrations ranging
from below detection limit (2 ppb) to 1260 ppb within a 600 X 400
foot plume. (See Figure 3). The vertical extent of
contamination is approximately 85 feet below grade.
Figure 4) .
(See
Residual soil level results indicate that arsenic concentrations
are below published background concentrations for soils in
Minnesota. U.S. EPA and MPCA agree that no further action on
soils is necessary.
The remedial action selected for the site will eliminate the
threats associated with ingestion and direct contact with
contaminated groundwater. The remedial action, in combination
with the 1985 remedial action regarding arsenic contaminated
soils at the site, should be considered a complete site remedy.
When this remedial action is completed, no further remedial
action is expected, other than groundwater monitoring. The
monitoring of groundwater would be conducted to assure that the
arsenic concentration in groundwater remains below the cleanup
level. Since the time to achieve the cleanup level is estimated
to take longer than five years, a five year review would be
necessary.
v.
SUMMARY OF SITE CHARACTERISTICS
A. Soil Contamination
The source of contamination at the site was arsenic-laden
grasshopper bait and technical grade lead arsenate buried in a
pit located in the southwest corner of the East Otter Tail County
Fairgrounds. The arsenic was buried approximately 3 to 6 feet
below grade. The dimension of the burial pit was 10 by 20 feet.
Soils around the pit area also became contaminated with arsenic.
The burial pit and surrounding soils are the only confirmed
source of contamination. An additional source was reported under
the Hammers construction company building. During the 1992/1993
investigation, borings were completed to determine if residual
soil contamination existed below the pit area and under Hammers'
building. Results of the soil investigation indicate that
-------
HQTES:
I ML WCUS ARC BELOW THE METHOD DETECTION
LMT UNLESS NOTED.
2. ISOCUNCCNTRATKM UNITS M ugA
ifvn*
TCI-4A t44 ugA
TCI-3A 1090 ugA
UtW-IA 4 ugA
MEW-B: 5 ugA
HEW-IDA: 3 ugA
UtW-l}A: 3 ugA
MEW-M: 69 ugA
UCW-19: 3 ugA
i«r«-» /
tot L. Irl ift
'. "- rnviD RO«O
UCICAII ft toot
wtu
FIGURE A
PERHAM ARSENIC BURIAL SHE
PCRHAtl. UMNCSOIA
A| ISOOONOMTRAnON HAP
MAT. Itf3 - DgP «niS
IWM cirt usrwc
UONIIORINC
-------
U0JE&.
I. Mi NOLS ARC KLOW THE METHOD OCTCCnON
UMT (MUSS NOTED.
2. ISOCONCOHTMTWN UMTS M ugA
LEGEND
". PAVI D ROAfl
tOUM |M C» «C M. I IK. • M
FIGURE 3
PERHAM ARSENIC BURIAL SIT
PEMHAM. MINNESOTA
A* ISOCONCCNTRADON MAP
MAT. IH3 - SHAU.OW BCU.S
UCTCALT * CDOT
-------
.... .. -. ~
11
arsenic levels were below published background concentrations for
soils in Minnesota and are not considered a direct contact threat
or a source of groundwater contamination.
Due to the presence of lead in the unmixed lead arsenate, soil
samples were also analyzed for lead. Lead analysis indicated
that levels found were slightly above background levels in one
soil boring. However, concentrations of lead in that boring did
not pose an unacceptable risk.
B. Groundwater Contamination
Contaminated groundwater, resulting from water infiltrating
through the former pit area prior to removal of unmixed lead
arsenate and arsenic bait, is the media of concern. Arsenic in
groundwater is at concentrations ranging from below detection
limit (2 ppb) to 1260 ppb within a 600 X 400 foot plume. The
vertical extent of contamination is approximately 85 feet below
grade. Analytical results at the site indicated that 99% of the
arsenic in groundwater is in the arsenate (As +5) state. Arsenic
in this state strongly adsorbs and does not tend to move far.
This appears to be the situation at the site. In 46 years, the
edge of the plume has migrated approximately 600 feet
downgradient of the initial source.
Because lead was in the unmixed lead arsenate, groundwater
samples were analyzed for lead. Concentrations of lead in
groundwater across the site do not indicate a clearly definable
plume. ,However, since lead is site related, it was evaluated in
the baseline risk assessment (BRA). The BRA determined that lead
concentrations at the site did not pose an unacceptable risk.
The groundwater recovery well network will be designed to capture
the arsenic plume. Lead concentrations encompassed within this
plume will be recovered and treated along with the arsenic.
Groundwater samples were collected and analyzed for the
Analyte List (TALs), to confirm the presence or absence
inorganic analytes. Results indicated that arsenic was
contaminant of concern.
Target
of other
the only
C.
Geology/Hydrogeology
Site geology consists of a massive unit of outwash sands and
gravels. Thickness of the outwash deposits under the site are
greater than 122 feet below grade. A confining clay unit is
reported to exist within the glacial overburden, however, the
confining clay unit was not encountered at the site. (See
Figure 5) .
Groundwater in the vicinity of the site flows in an east to
southeast direction towards the Otter Tail River which is
approximately 1.8 miles to the east of the site. Groundwater
levels at the site are approximately 22 to 24 feet below grade.
-------
I ~
Q
-
:) .
; ,
t:
c
Q
~~ ELEV. O'
WIW-"
I
I ~.."
20" - ...
2.%- r-' ~--_.&._-----
i I
I
I .0.
---------
,.
10' sumcw.
SAND
ICNCI8 AGWD
SAUATa) SPTOSw
MaoIDS ,-
100.
~ Iff
II
;
0
f
CI.
c
1CXr
t!
c
Q
12D'
12Z"
~
II
8
x
~
(
W ..
c c::.
Q .
.
.
; !
I .
c ~
! .:
18
...
110'
2nII SMD ACUPIII
......_Y CAPAILI 01 SUSTAINI80
SI.8STM8UI. GUAN1I1D 01 WAD
,.
8lt
~[
lIS&.
....,.: DIIPaT ~ 8IID AT - 81E
t
... . LOCA'IICIN!
01 1MIIE UII1S ME
M81U8rt. NIIJ
IA8D CIN
"",,1ICIN ....
- (1m)
.:~ KE'l'CALF ac EJ)I)Y
F1GURE 5,
PERHAM ARSENIC BURIAL SITE
PERHAM. MINNESOTA .
GENERAUZED STRA l1GRAPHIC SEQUENCE
-------
-
13
The glacial outwash aquifer at the site is characterized by
to coarse sands and gravels, admixed or interbedded, with
sporadic silty areas. The sustained yield rating for this
aquifer is estimated to be 100 to 500 gallons per minute.
fine
D.
Groundwater Use
Water supplies obtained from the aquifer present in the Perham
vicinity are used for industry, agriculture (irrigation),
municipal, and residential demands for potable water.
The nearest residential well currently in use as a domestic water
source is located approximately 700 feet to the south of the
former arsenic pit, perpendicular to the groundwater flow
direction. The well was sampled and analyzed on three separate
occasions during the course of the RI. Arsenic concentrations
detected in the residual well averaged 6 ppb. Lead
concentrations were below the instrument detection limit. The
background concentration for arsenic was determined by analyzing
groundwater samples collected from the upgradient well MEW-8.
Background arsenic concentration is 5 ppb. Therefore, arsenic
concentrations in the residential well are at background levels.
VI.
SUMMARY OF SITE RISKS
A. Human Risks
Information contained in the BRA of the RI Report indicates that
current and future potential health risks to individuals at the
site are related to exposure of arsenic contaminated groundwater
via ingestion and dermal contact. A current and future
residential use scenario was used for arsenic in groundwater.
Arsenic is classified as a Group A Human Carcinogen.
Concentrations of chemicals of concern (arsenic & lead), on which
the risk assessment was based, were determined by following U.S.
EPA guidance which requires a 95% upper confidence limit on the
arithmetic mean, assuming a log-normal distribution. Exposure
point concentrations were determined by either the maximum
concentration within the contaminant plume, or the 95% upper
confidence limit, which ever was lower. Maximum concentrations
of arsenic from the existing residential well were used as the
existing groundwater exposure source.
Exposure pathways considered were ingestion and dermal contact
while showering with arsenic contaminated groundwater.
Potentially exposed populations under the current use scenario
identified the closest residential well. Under future use
scenario, primary receptors were children and adults that would
reside directly on site and would receive their drinking water
from a groundwater well installed on site. Exposure intake
variables used in the risk assessment were selected so that the
combination of all intake variables resulted in an estimate of
the Reasonable Maximum Exposure (RME) for each pathway.
-------
.~
14
Cancer potency factors (CPFs) have been developed by u.s. EPA's
Carcinogenic Assessment Group for estimating excess lifetime
cancer risks associated with exposure to potentially carcinogenic
chemicals. CPFs, which are expressed in units of (mg/kg-day)-1
are multiplied by estimated intake of potential carcinogen
(mg/kg-day), to provide an upper-bound estimate of the excess
lifetime cancer risk associated with exposure at that intake
level. The term "upperbound" reflects the conservative estimate
of the risks calculated from the CPF. Use of this approach makes
underestimation of the actual cancer risk highly unlikely. CPFs
are derived from the results of human epidemiological studies or
chronic animal bioassays to which animal-to-human extrapolation
and uncertainty factors have been applied.
Reference doses (RFDs) have been developed by U.s. EPA for
indicating the potential for adverse health effects from exposure
to chemicals exhibiting noncarcinogenic effects. RFDs, which are
expressed in units of mg/kg-day, are estimates of lifetime daily
exposure levels for humans, including sensitive individuals.
Estimated intakes of chemicals from environmental media (e.g.,
the amount of a chemical ingested from contaminated drinking
water) can be compared to the RFD. RFDs are derived from human
epidemiological studies or animal studies to which uncertainty
factors have been applied (e.g., to account for the use of animal
data to predict effects on humans). These uncertainty factors
assure that the RFDs will not underestimate the potential for
adverse noncarcinogenic effects to occur.
Excess lifetime cancer risks are determined by multiplying the
intake level with the CPF. These risks are probabilities that
are generally expressed in scientific notation (e.g., 1XIO-6).
An excess lifetime cancer risk of 1X10-6 indicates that, as a
plausible upper bound, an individual has a one in a million
chance of developing cancer as a result of site-related exposure
to a carcinogen over a 70-year lifetime under the specific
conditions at the site.
Toxicity value information used in the risk assessment for
chemicals of concern at the site are summarized in Tables 1 & 2.
The findings of the non-carcinogenic hazard assessment
demonstrated that the total non-carcinogenic hazard indices for
the future adult and child receptor populations exceed the
criterion value of 1.0, and are above acceptable levels. Results
indicate that ingestion of arsenic in groundwater is the exposure
route primarily responsible for the increased hazard.
Unacceptable cancer risk estimates calculated in the risk
characterization were associated with ingestion of groundwater
for both the adult and child future receptor populations. (See
Table 3).
-------
15
"~
Table 1 ," CrtticaJ To* errecu for Chemicals of Concem at the Pemam Site
~
nc
NONCAACENOGENIC EFFECTS
ORAL I INHAU. TION
k8r8tatI8 NA
"n
C8nIr8I neNDUS
tD' "
C8fIIr8J ft8fYOUS
CARCINOGENIC EFFECTS 2
ORAl INHAU.t10N
akin ""8ty tr8Ct
A A
NA NA
B B
L8U
(1) Soun:8: Annual FY-1992 HlaIIh Etr8CtlAu8llm8nt S&8'nnwy Tabl8l
(2) U.s. EPA WIigN of Evid1nc8 for CarQuogtftl:
~ A. HWMn Cala8Dg8n
~ B. Probabll tUnan Carcinogen
~ C. POI_II Hwnan Carcinogen
Group D. Not Clallifiabll
Group E. Evidence 01 Noncarcinog.nicitf
NA-Not Applicabll
-
~
-------
\0
".
Table 2
TOXICItY v_un FOR CHEMIC.S Of CONCERII AT PERHMI ARSENIC III"" ..
Arsenic
lHd
-_.- ._--
NONCARaNOQ(NC
. .. .
..... MUJSJID OIW.ID(
........ ,..,..... ...
-- ~ ~- ~_.,
'.-04 , CICIE - o. aISE-O. a
NA HA NA
fI08
. 0_. --..,.
I8IIQ
O""CAl
~
I5E -0.
~
-s..um.. u s (P~.,.....ed "'1rI--""'" ff'S) ....... --...... ,...
us (P"t4888hltl8dl. III ,_U""~J).Arn8lFY-I""'_"~~ 1-
..~. ....,..I8\~d.1JhIt ""..AoH
"I Ad8utIed "'I~ --..-... --. - . "'..........
~.... d ",..."MiLA"."""'''''_:
~I_..""" Aq . PII M8c.. ......,.... - ~I~ 1I8d DaM AD
Ibl ~8td cnllCIIIIcIr ..... wed... 'I'""- . - 1 '" ...........
~..... d end,.",,$d .......... ...QF:
1oW.-......4 CSft-" P" ~ .,....'"", - MIoItIMI*8CIF
lei 081~..._.'" """-*81-..-''''''''' . W.r...........
b '0I8C""'8n08e end o.-~. Ul~ ~HI8Ih"'"
-.A_lID
~
II8CHDIC CHUiIC
:T"£
-. -----
0fW.
.OPE FACrOA
~~-,
, tOE.OO
NA
~I!l~!.~'-
AOJU8rEO OAM.
.....,
aGPEFACIGR ..
-I
, ".00
NA
8HIIA1IaN
8I8'E FM:IaII
~-I
,'.."
NA
aw.
AMOirr'1UII'I
FM:lOA
~~tcI
PC
V-IE
~
015 1000-OJ
O~ -!-~-OJ
."
-------
17
.~
Table 3
Summary of Risk and Hazard CaJculations
1
" ..::~~:{~~:f.~1?f::':.~:;~~?
R~ Rsk H~
Inge.tIOn 1.69E-04; 7.31E-01 ,
Dermal 1.38E -071 S.97E -041
~,~~~::_~:;;t:;:;W,A1i~
iTota1 1.69E-041 7.32E-011
MatrIX
, Grounawater
~~~.",;.~;;~>",..~-,~~:~
~~'0;:~s.'~~i~~"":; '(. ..". I J " .; ,...~~~~ . \" A~ "~fi"'.., - .. /~~~ ~ >A
Lr:...-.-.._~...~"";",.::'.).- t.,~..:~........ ,.~.........:"'an"'.'("~~t:""'."'~)\' ~.. .c-:
; Matrix
I
I GroundWater
I
:A0ut8
,Ingenon
, Dermal
Risk
6.34E-021
5.18E-OSI
Hazara
2.741:+021
2.241:-01 !
... . ,'.....""
,......~....:~\~;:"'.
:" ;::: -:.~t~&1{~.:.;. :';'. '..... .,...::0'
'"'',''' '-'" ", "',""':"
.. ".. ...,~ . "~~':';'~"~~::':::':~"~"'" "
. .::.:.:....'" - ..:.~ '.;..
I'~*%:::::::::::' ,:j:~~;i-"~~~f.~p~L:::
I'".' , '.-..1,."',","'''".,.....,,,,-,,,,, :y,';'," ',':'
Hazara
5.991:+021
3.67E-011
: Total
, Matrix
: Groundwater
I
'Route
,Ingedan
IDermat
Risk
2.31E-021
1.42£-051
F,'~'~'(~~~~~~~~"'~~;'~~~",~-::""~"'~~~~r~~:~~s::;':~~
2.31E -021
S.99E +02 1
ITataJ
.
-------
-
18
B. ENVIRONMENTAL RISKS
The ecological assessment in the RI concluded that environmental
impacts on surface soil (0-2') and subsurface soil (2-10') were
important because most exposure to site contaminants would occur
through soil. Exposure pathways from on site soils involve three
indicator species. Selected indicator species are not expected
to be negatively impacted by contamination on site. Although
concentrations of lead exceeded Minnesota background levels, a
comparison of ingestion and uptake rates with toxicological
values indicated that the risks associated with lead were at an
acceptable level.
Conclusions made from site observation during the RI indicate
that no signs of stress on indicator species (grasshoppers) or
vegetative stress (yellow sweet clover) were observed.
VII.
DESCRIPTION OF ALTERNATIVES
The objective of the FS and the Proposed Plan was to evaluate
remedial alternatives consistent with the goals and objectives
of CERCLA, as amended by SARA.
Health and environmental risks identified in the BRA for the
site provide the basis for establishing the remedial action
objectives for the site. The BRA indicates that the one
significant contaminant pathway is exposure associated with
ingestion of contaminated groundwater. All remedial action
alternatives in the FS involved a combination of extracting
groundwater and various treatment options. A treatability
study was conducted in the RI phase. Results of the study
were used to develop the treatment component of remedial
alternatives.
A.
Alternative 1
No Action
In this alternative, no remedial action would be performed at
the site. No efforts would be undertaken to contain, remove,
monitor, or treat contaminants in the groundwater at the site.
Evaluation of the no action alternative provides a baseline
against which action alternatives can be compared and
evaluated.
B.
Alternative 2
Institutional Controls, Recovery Wells, Precipitation,
Filtration, Alumina Adsorption and an Infiltration Gallery
Alternative 2 involves institutional controls (e.g., deed
restrictions), recovery wells, groundwater treatment by
precipitation, filtration, and alumina adsorption, with treated
groundwater discharge via an infiltration gallery.
-------
-
19
Institutional controls (deed restrictions) would regulate the
present and future use of groundwater at the site.
Institutional controls may be altered or entirely removed once
the remedial objectives are satisfied.
Groundwater recovery wells would be installed to remove
arsenic contaminated groundwater from the aquifer which exceeds
the cleanup level.
The groundwater treatment process under alternative 2 consists
of equalization tanks, pH adjustment units, a precipitation
unit, a continuous backwash filter, and two activated alumina
adsorption units. A backwash holding tank and a dewatering
unit would be included for dewatering sludge obtained from the
precipitation and filtration processes. (See Figure 6).
Treated effluent would be discharged to the aquifer through an
on-site infiltration gallery.
Residual wastes generated under alternative 2 are solids
associated with precipitation and filtration and spent alumina.
In the FS, residual wastes were assumed to be hazardous and
would require disposal at a hazardous waste facility. However,
analytical results may indicate that residual wastes can be
disposed of as non-hazardous waste. Cost estimates used in the
FS assumed that residual wastes were hazardous. The estimated
total present worth cost of this alternative is $ 2,681,894.
(See Table 4).
c.
Alternative 3
Institutional Controls, Recovery Wells, Filtration, Alumina
Adsorption and an Infiltration Gallery
Alternative 3 involves institutional controls (e.g., deed
restrictions), recovery wells, groundwater treatment by
filtration, and alumina adsorption, with discharge of treated
groundwater via an infiltration gallery.
Alternative 3 is very similar to alternative 2 except that
precipitation is not included. A continuous backwash filter
would be used to remove the suspended solids. Arsenic and/or
lead adsorbed to suspended solids extracted by the recovery
well network would be removed through filtration. Activated
alumina adsorption would be used to remove the dissolved-phase
arsenic. Since precipitation is not included in alternative 3,
only two pH adjustment units would be required. (See Figure 7).
Treated effluent would be discharged to the aquifer through an
on-site infiltration gallery.
Residual wastes generated under alternative 3 (filtered solids
and spent alumina) were assumed to be hazardous and require
disposal at a hazardous waste facility. Cost estimates in the
-------
....
I
,
EQUIUZAIION
IANKS W/UlX[R
(12' DIAMETER)
~
~
C
D
METERING PUNP NO.1
o
SHElTER [QUFPED
Nnt UCHT DUN
BRlDCI: CRAN[
..
.- _...
ARSENIC REMOVAL lANK
BACkWASH PUMP
CONtINUOUS BACI(WASH
FIltER (9' DlAU[TER)
SPEN I ALUMINA DEWA TERING
TANK W/M:NRH WAtER PUIoIP
B£N£A JH (10' DIAMEtER)
.'
, " .'
. .::
'I'
,I.
...
III
ft
;
o A
.' I!I
~ I
~
~
I
M:~ MJ:1'CAU' 81 EDDY
FIGURE 6 AL TERN A fl\IE 2
PERHAM ARSENIC SI TE
..
CONCEPTUAL SITE PLAN OF
WASTEWA TER TREA TMENT METHOD
. ----"-"----
I
II BACK wASH HOlDING
WEll BELOW SLAB
Lh-':::=:::=:::=
I..
pH AD~S1UENT
TANKS WI'IXDt
(6' DIAMETER)
F'lOCCULATOR/PlA It
5U»ARATOR -/
SlUDGt PU"
B£NU JH TANK
ARSENIC REMOVAL UNITS
(10' DlAMEI£R)
cf fiNAL pH AO.Al5"'ENT
TANK W'MIXfA
(e' DIAMETER)
r-----,
I I
I ALUMINA I
STORACI:
AREA
I . I
HEC TRleAl Mee
ME I£RING PUMP NO 2
CON'ROt PANEl
o
$lUDCI:
DEWA T[RING
UNIT
ACID / CAUSIIC
HOlDING AREA
BACKWASH HOlDING
TANK W'SlUDGE PUMP
8OI£Ant TANK
(t' DIAMETER)
'20' -0"
INSIO( OF IfI£RIOR CONCR[I£ CURB
SCAL£: I". 10'
-------
21
TABLE 4 PRESENT WORTH SUMMARY FOR AL TERN~TIVE 2
:
:11.", EdIM8
BYiIc8ing S1oo.800 1 SOl 61 SOl S1oo.8001 S15.'2O 1 "5.82D
. FDUrI08IIOn S17.0501 SOl '! SOl $17.0501 12.551 III"
1Cl- S10.7ool SOl ,I SOl 110.7001 IUIDI Staas
I S tI.D551 I I
EJdr8c:aan Well S...", SO , :1 118.0551 12.401 .,...
If""_. G8II8ry lZUClI SO 8 IZI.M8 S4.M2 UU87
o
T..... ".700 1 sol 8 SOl 118.700 113.451 ....,.
. ...... -.IDOl S8ADO I 8 -I 111'.'08 117.18 ..8.171
I
. SIudI8 fI\nnp8 15.400 I 1801 8 11.,",7 17:Jtl7 SlJIII SlAGS
. 122.400 I 1...00 I I
MIDra 8 17.8281 130.028 S4" 8M-
I I ,I sol
: PlatIDnn tar Mi.., S13,3501 sol Sl:U5D IZJ1D3 IILSD
SIudge 08w88nng Unt S15.1OO1 S1.1ool 61 15.2431 S2O.8431 a.128 IZU70
,
I I
. PIdDnn tar SIudIJ8 0. .At..11 Unit 12.700 I SO! 8 SOl 12.700' S4D8 a.1011
LOT Equip--. . 1227.5DO 118.5DO . 171.8481 1308.1" S48.1ZZ ssu.cna
Adla rMrs CAUniM) "44.oaD 10 . 10 1144.oaD 12'''' .,--
.. fI fir. a 181 Plot 8tudI88 ...000 . . SO UO.1XlD ...... .....
I
tT1I1 ~r I.. IIO.GDD . . 10 IIO.GDO 11- -
......... CanIraI US.540 . . SO 1ZS.540 . IUS' 111.D'7'
"'*" & V8h88 " 18.oaD . 8 10 1II8.oao 117'" "IIMD
EI8ottG8I ,,85.DOD 10 8 10 ,'II.oaD au. "..78D
........ I~. S82.DDO . 8 SO SIZ.DDO 11.- 171.-
BuIIdIn9 08"'--' S8I8ge (S3D.GDD'I so 8 SO
of ScI8p ......
EI8ato Pow8r . Sl4,470 8 U07.211 U07.211 ...... ~.
..... SO Sls.aDO . SlIMS II' .181 11.211 171.-
CtwIlllc8ll 80 "0.000 . 147.- 141- 81.'. ......
AIumN UIIIg8 80 "'" 1217.. aI7.D11 S4U8 -.,.
W_'1Iudge DIICIGI8I 80 IZS". 8 '"0.'07 '"0.107 1",8" It...
- (AIuInN& ~
AnltJti181 ~lIftMt tar L8d1D1188a88 11.114 . . 10 11.114 1171 ItMl
88mI-Amu88 W81.......... . 1""'0 , IM.80Z 114.102 Sl4.2S8 ""'87
e.... DI8~ ""'i.~ 80 SU40 , 118.304 "UD4 12.78 1I1JM1
1:.1.,...;.. SII.GDO so . , SO m.231 SlU8 88UZ4
Sub8III8I 11.288.48<1' S2Z0.545 11.D51.238 1 1~2oa 1348.1'1 a.8''-
.
Ta181 "-II -.. .......... a c.-.'" .a.W-~ S2.II' ....,
SolIdI ...
....-A8- 7~ fII8InnI..... "'''''' . LOT Eqyll _II""'" two". r r .... ...-....-
-------
".
I
EOUUZA 110N
TANKS W/WIIlA
(12' DIAUrJ[R)
i
..
C
,
- - ---.. ----
~
''''...
- - .
'f
. .
"i.
SHEl TER [QUIPPED
"'1M LICHT DUlY
BAlOG[ CRANE
COH11NUOUS BACkWASH
F1l TER (9' DlAWED)
SPENT AlUMINA DEWAtERING
TANK W/REtURN WATER PUMP
BENEAtH (10' DIAMETER)
ARSEIIC REMOVAL TANK
8AQ(WASH PUMP
EmUENT PUMP
NO.1
EfflUENT PUMP
NO.2
fiNAL pit AOAlSNEHT
TAHIC WI'III£R
(I' DlAMET[R)
o
'---I
I I
I AlUMINA I
STaRAG[
AREA
I
UECJR1CAl
UCC
UEJ[RING PUMP NO.2
CONTR
-------
. TABLE 5
I
IIt8tft
I BuildIng
I Four-' - m
I
Ie...
r:. 1'1. W818,a....
....... G8II8ry
T...
......
aIudg8 P\8np8
......
, PI8I8Dnft tor Mi8r
Sludge De _iii'll UM
I PI8IIann tor .... D&
tL-oO unit
LOT £quI! .1*111 .
& If H rM 18 "UniI8)
t II JIM ... Plat .....
r-
Mil.
.. . ~ .. CoreaI
PIpIng .. v... .
EJ8ctta8I
L"'~- '.
..... OM I'~r 1'" e--..
of ..... M8I8I
EI8c8tD '--
.....
M8IIn8 UI8g8
w..,.....,. DIII88 (AUIdI18)
",..~ AJJ ....... L8dI DII,088
""-An1'u8 Well.....
--Dllc""""~4
E.~-"II
SIII8D8It
23
PRESENT WORTH SUMMARY FOR ALTERNATIVE 3.
Caod8I
Cut
. Aftnu8I I Duruon I Pfn8m WOfV'II Total eo."'IIJ8I11Jy I TOI8I Coat"
O&M Coat I (YMISI I O&M PreunI Wortftl [' 5 .., I ~ t
114.0001
$'4.8201
$'0.7001
$".0551
I
IZLMII
I
S8UOO1
SII.tOO I
13.100 I
I
I
12t.Ooo!
$11.2001
$15.1001
,
$2.700 I
,
1115.000 I
'toM.ODD
121.000
ssa.ooo I
azt.MO
"07.'10
"SUCD
SS8.locr
I
(ROJIOOJ
S 1.1501
SlUoo
11.1IU14
101
I
101
I
10
10
10
10
~
~
SUOO
10
$ 1.200 I
sol
114.1GO
80
10
.
.
.
.
10
10
so
SO
S84A1O
111.000
so
.
',0.000
-.-
.
12Z.'.
.
so
.
S""'O
SU40
.
1211'"
. TOI8I"-II Wcdt tor AIIm8IM. a (with HuMfaUl W_""'"
SoId8 ......tndud8"ClD8tofHIJ:I~au .~ 'f' ...
~...... 7.aca
fII8nnIRt ...... II . ,....
61
61
81
81
'I
,
,
,
S3UH
11.430
8
II
$~'.62I
10
15.720 1
6!
81
,I
101
I
SlI.115
.
,
.
,
,
.
.
,
,
,
U07 .-
., .lIS
.
.
147.115
1217 .DI8
.
,
1tGUZ'
so
.
,
IM.IOZ
."...
,
IUsa. nil
12.548.7711
101
SOl
!
so;
184.0001
St4.8201
110.7001
s18.au1
I
128.141
SIZ.8OO
S 12.1GO
S2.Z8
".-
SZAOI
14'"
112.-
.18.-
S1I4
S4.2IN
IUIIO
A.'"
sa
...."
121-
IUOO
If...
18.1-
.tem.
IZZ.711
....
......
--
If.'.
....
".....
"71
s,...
11.7-
"D.,.
uuoo
"7.158
1tz.=5
,,1M3
8IUI7
8aZ2G
"..
"714
au2G
"U80
I
124.5181
1S.IOS
aos.nz
"lUCID
_.100
_.100
.....
ItIS.Z34
It,.....
-.as
tilt ..
171.280
....."
""IS
Itlt .410
.t..
1t.,'If
at-
877A11
na..... 8U48.7'11
. LOT ~ -.........-.......
so
so
so
"za.DSt
1S.D30
128.121
111 .200
$21.320 1
I
S2.700 1
8Z84.115
so
.toM-
I2UOO
so
10
sao.aoo
at .140
so
10
8107.110
.'SUCD
10
so
S58.IOO
10
SS07 .-
., .181
147'-
UI7-
.tauzr
'1.114
1M.1D2
11....
10
887 ,S84
12.218.321
-------
.~
24
FS considered disposal at a hazardous waste facility. The
estimated total present worth cost of this alternative is
$ 2,548,776. (See Table 5).
VIII.
SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES
In order to determine the most appropriate alternative for the
site, the alternatives were evaluated against each other.
Comparisons were based on nine evaluation criteria.
Threshold criteria must be met before an alternative can be
carried forward. The threshold criteria are: overall
protection of human health and the environment and compliance
with applicable or relevant and appropriate requirements.
The recommended alternative will provide the best balance with
regard following five criteria: long-term effectiveness and
permanence; reduction of toxicity, mobility, and volume through
treatment; short-term effectiveness; implementability; and
cost.
The two modifying criteria: state & community acceptance, are
evaluated after comments on the recommended alternative are
received.
A. Overall Protection of Human Health and the Environment
The No Action alternative (Alternative 1) does not provide
protection of human health and the environment.
Alternatives 2 and 3 were determined to provide high levels of
overall protection because remedial actions, when completed,
would clean arsenic in groundwater to an acceptable level of
protection. Short-term protection would be provided by the
implementation of deed restrictions, which would immediately
restrict current use of groundwater at the site.
B.
Compliance with ARARs
Alternative 1 would fail to meet ARARs because arsenic in
groundwater would continue to exceed the MCL. Remedial actions
taken under alternatives 2 and 3 would comply with all ARARs
except Minn. Rule 7060 Underground Waters. Minn. Rule 7060
applies to the discharge of treated effluent through a
infiltration galley. A variance from Minn. Rule 7060 would be
required.
ARARs specific to remedial actions under alternatives 2 & 3
are: Safe Drinking Water Act, 40 CFR 41, maximum contaminant
levels (MCLs), Minn. Rule 7060, Underground Waters, and RCRA
Subtitle C requirements regarding generation, transportation,
treatment, and disposal of hazardous wastes generated in the
course of remedial action.
-------
.,
25
c.
Long-Ter.m Effectiveness and Per.manence
The No Action alternative offers no protection against future
exposure of site contaminants to humans and the environment,
and no means by which to reduce the levels of arsenic.
Therefore, alternative 1 would be ineffective for the long-
term.
The remedial actions under alternatives 2 and 3 are expected to
provide reliable long-term protection of human health and the
environment. Impacted groundwater would be permanently removed
from the aquifer and treated on site. In the long term, this
would reduce or eliminate the unacceptable human health risk
which arsenic contaminated groundwater poses. Groundwater
treatment would be effective in reducing arsenic concentrations
equally for alternatives 2 and 3. Groundwater treatment is an
irreversible process with regard to removal of dissolved-phase
arsenic, therefore, it would be a permanent remedy.
Groundwater modeling indicates that arsenic removal to the MCL
(50 ppb) would be achieved in approximately 6 years.
D.
Reduction of Toxicity, Mobility, and Volume
Alternative 1 employs no remediation, and therefore achieves no
reduction in contaminant toxicity, mobility, or volume.
With alternatives 2 and 3 the use of a groundwater recovery
well system would reduce the volume of arsenic contamination in
groundwater.
E.
Short-Ter.m Effectiveness
The No Action alternative is not effective in the short term.
Groundwater use would still pose an unacceptable risk at the
site.
Assuming that residual wastes generated under alternatives 2
and 3 are considered RCRA characteristic for arsenic,
transportation from the site to a hazardous waste landfill
would be necessary. Off~site transport of residual wastes may
present some risks to residents, if an accidental spill or
release of these materials would occur.
When compared to alternative 3, alternative 2 would have a
greater amount of residual wastes generated because of the
precipitation unit. Therefore, short-term risks associated
with transportation are greater in alternative 2 than
alternative 3.
Construction activities associated with the implementation of
alternatives 2 and 3 will not result in any health risks to
nearby residents or employees of nearby commercial facilities.
Site workers could be exposed to impacted groundwater during
remedial activities. However, impacts to site workers during
remediation will be controlled with the use of the appropriate
-------
.~
26
personal protective equipment (PPE), and by ensuring that site
workers have the appropriate training. No significant
environmental impacts are expected for either alternative.
It is expected that both alternatives 2 and 3 can be
implemented within 16 to 24 months.
F.
Implementability
The No Action alternative has no technical feasibility
considerations.
Alternatives 2 and 3 are technically feasible. Alternative 2,
when compared to alternative 3, may be more difficult to
implement due to the installation of a precipitation unit.
Both alternatives utilize proven technologies which are
commonly used in the wastewater and water treatment industry.
Treated groundwater under both alternatives 2 and 3 would be
discharged by means of an infiltration gallery which would
require a variance from the MPCA.
G.
Cost
The No Action alternative has no cost associated with it.
The capital and O&M costs associated with alternative 2 are
higher than costs associated with alternative 3 because of the
precipitation unit. In addition, due to a greater volume of
residual wastes generated from the precipitation unit,
transportation and disposal costs are greater under alternative
2 than under alternative 3.
The cost benefit of alternative 3 over alternative 2 derives
from the difference between solids removal from filtration vs
filtration and precipitation.
Results indicated that installation and O&M costs associated
with the precipitation unit were greater than the increased
costs of filtration, if the precipitation unit is not
installed. In addition, another residual waste stream is
created from the filtration and precipitation alternative.
H.
State Acceptance
Alternative 1 is unacceptable to the MPCA. The MPCA has been
consulted and concurs with the selected remedial action.
I.
Community Acceptance
Based on available information, community acceptance of
alternative 1 is unacceptable. Community acceptance of the
-------
..... - ,-. .
27
remaining alternatives is addressed in the attached
Responsiveness Summary.
IX.
THE SELECTED REMEDY
Alternative 3
Institutional Controls, Recovery Wells, Filtration, Alumina
Adsorption and an Infiltration Gallery
Alternative 3 involves institutional controls (e.g., deed
restrictions), recovery wells, groundwater treatment by
filtration, and alumina adsorption, with discharge of treated
groundwater via- an infiltration gallery.
Institutional controls in the form of a deed restriction will
restrict groundwater use at the site.
Vertical groundwater recovery wells will be installed to remove
arsenic contaminated groundwater above the clean up level (50
ppb) .
A continuous-backwash filtration unit will be used to remove
arsenic (suspended solids phase) in extracted groundwater.
Groundwater would then be treated on site by activated alumina
adsorption units. Extracted groundwater would flow through an
activated alumina bed contained in a vessel. Arsenic would be
adsorbed onto the activated alumina. A treatability study
conducted in the RI indicated that alumina absorption is the
most efficient method of removing dissolved phase arsenic from
groundwater at the site.
The used alumina filter media and filtered solids may require
disposal in hazardous waste landfill. Residuals generated
under alternative 3 were considered to be a hazardous waste in
the FS for the site. Final determination as to whether the
residual waste is considered RCRA hazardous will be based on
the laboratory analytical results. Cost estimates for this
alternative assumed that residual waste would be transported
and disposed of as RCRA hazardous waste.
Treated effluent would be discharged to the aquifer through an
on-site infiltration gallery. The infiltration gallery could
be placed either upgradient or downgradient of the extraction
system, depending on the desired effect upon the impacted
portion of the aquifer. If the infiltration gallery is placed
upgradient, the groundwater gradient should increase,
accelerating the rate of groundwater flow though the
contaminated area and reducing the clean up time required.
To determine approximate time to achieve then MCL for arsenic,
the FS took into account the fact that after arsenic (suspended
solid & dissolved phase) is removed, some desorption of arsenic
from the aquifer may occur. The removal rate for the suspended
solid and dissolved phase arsenic combined with desorption
-------
.~
28
calculations provides a total arsenic removal time of
approximately 6 years. The estimated total present worth
of this alternative is $ 2,548,776. Costs are summarized
Table 5.
cost
in
The Safe Drinking Water Act establishes MCLs for drinking water
quality. The MCL for arsenic is currently 50 ppb. The MCL for
arsenic is applicable at the residential drinking water tap.
The MCL for arsenic is considered relevant and appropriate for
establishing cleanup levels in the groundwater at the site
because under a future residential use scenario, groundwater
from the site may be used for residential drinking water.
The Minnesota Department of Health (MDH) Recommended Allowable
Drinking Water Limits, MDH Release #3, 1/91, of 0.2 ppb for
arsenic is a guideline to be considered. This potential clean
up level does not take into account the fact that arsenic is
present in background concentrations at 5 ppb. u.S. EPA and
MPCA agree that this guideline is not considered appropriate
for establishing clean up levels at the site.
According to ATSDR, the MCL for arsenic may be lowered in the
future. In that case, the five year review for the site would
address this potential change in cleanup level.
In response to a comment received during the public comment
period, u.S. EPA plans to provide municipal water to the
residence located approximately 700 south of the site.
Although the present groundwater flow direction is east, a
change in flow could put that resident at risk. The long-term
effectiveness and cost benefits associated with a municipal
water supply hook up are greater than implementing a quarterly
monitoring program which would be required under a long-term
monitoring plan.
XI.
STATUTORY DETERMINATIONS SUMMARY
1.
Protection of Human Health and the Environment
The selected remedy satisfies the requirement of CERCLA Section
121(b) and (d), 42 U.S.C. ~ 9621(b) and (d), that a remedial
action be protective of human health and the environment.
Based on the results of the Remedial Investigation (RI), the
medium of concern at the site is groundwater, and the
contaminant of concern is arsenic. The pathway for exposure to
the affected human population is through ingestion of, and
dermal contact with, contaminated groundwater. The pathway for
exposure to other populations is the ultimate anticipated
migration of contaminated groundwater to the Otter Tail River.
The remedy contemplates the removal and treatment of all
groundwater contaminated with arsenic at levels above MCLs.
This will eliminate the risk to all affected populations.
Pending completion of remedial action, institutional controls
would prevent use of groundwater at and in the vicinity of the
site, and any well installation that would have an impact on
-------
.~
29
groundwater flow direction. The arsenic is contained in a
defined plume that is traveling at a relatively slow rate, and
no effect on nonhuman populations pending completion of the
remedy is anticipated.
Any short-term risks associated with implementation of the
selected remedy would be eliminated by using sound construction
and waste transportation practices. Additionally, air
monitoring will be conducted during the remedial action to
assess any possible exposure through inhalation. Therefore, no
unacceptable short-term risks or cross-media impacts will
result from implementation of the selected remedy.
2.
Attainment of ARARs
The selected remedy complies
and appropriate requirements
Section 121 (d) (2), 42 U.S.C.
for the site are as follows:
with all applicable or relevant
(ARARs), as required by CERCLA
~ 9621 (d) (2). ARARs identified
a.
Chemical Specific
Safe Drinking Water Act Maximum Contaminant Levels (MCLs)
(applicable)
Resource Conservation and Recovery Act Identification and
Listing of Hazardous Wastes, 40 C.F.R. Part 261
(applicable)
b.
Location Specific
(none)
c.
Action Specific
Minn. Rule 7060.0600-0900 [prohibition on waste filtration
galleries, and variance from the prohibition where
necessary to protect public health, safety or welfare, or
where strict conformity with the prohibition would be un-
reasonable] . (applicable)
Resource Conservation and Recovery Act Generator
Standards, 40 C.F.R. Part 262 (applicable)
Resource Conservation and Recovery Act Transporter
Standards, 40 C.F.R. Part 263 (applicable)
While not ARARs because the contemplated activity will occur
off-site, it is noted that it may be necessary to ensure that
residual wastes from the treatment process are disposed of at a
hazardous waste facility that complies with RCRA Subtitle C
requirements and, if the pertinent standard for arsenic is
exceeded, RCRA land disposal restrictions (LDRs), 40 C.F.R.
Part 268, because these wastes may contain arsenic in
concentrations prompting such protectiveness.
-------
.~
30
3.
Cost Effectiveness
The selected remedy provides overall cost-effectiveness, as
required by CERCLA Section 121(b), 42 V.S.C. ~ 9621(b). The
incremental benefit of the precipitation component of the
second alternative has been determined not to justify the
increased cost of adding this component. Rather, the cost
benefit achieved by extraction and treatment via filtration and
alumina adsorption of arsenic-contaminated groundwater is
greater than that achieved by extraction and treatment via
, filtration, precipitation and alumina adsorption.
4. Utilization of Permanent Solutions and Alternative
Treatment Technologies or Resource Recovery Technologies to the
Maz~ Extent Practicable
The selected remedy utilizes permanent solutions and treatment
technologies to the maximum extent possible, as required by
Section 121 (b) (1) of CERCLA, 42 V.S.C. ~ 9621 (b) (1). The
remedy contemplates on-site treatment of arsenic-contaminated
groundwater through filtration and alumina adsorption. When
the remedial action is complete, the contamination will be
removed to levels at or below the MCL for arsenic, and the
unacceptable threat to human health and the environment would
thereby be eliminated.
It also provides the best balance of factors considered under
the nine evaluation criteria. The remedy is a permanent one,
intended to leave no residual risk to the affected populations
once the clean-up levels have been met. In the short-term, the
remedial construction and remedial action phases are expected
to be relatively brief and, through the employment of sound
engineering practices, should present no threat to human health
or the environment.
The affected municipality and the State of Minnesota both
support the selected remedy. U.S. EPA has fully apprised the
City of Perham of the proposed course of remedial action and
has secured the cooperation of the Minnesota Pollution Control
Agency, and anticipates no controversy at any phase of the
proposed remedial action.
5.
Preference for Treatment as a Principal Element
The selected remedy uses groundwater recovery and on-site
treatment through alumina adsorption as its principal element
to eliminate the principal threat of ingestion of groundwater
at the site. This requirement of CERCLA Section 121(b) is
therefore satisfied.
-------
ATTACHMENT 1
MPCA LETTER OF RESPONSE
.~
-------
.~
Minnesota Pollution Control Agency
Mrcn 31, 19'
.
. 0Ue&1&il CuUDt)', MiDDesou, Aecorcl of DeciI10D
AutoioD Control Agcacy (MPCA) bas received aDd reViewed the R.ecord of DecisiOD
.-erIuun Aneaic Superi\aDci Site iD OtI8rIDiJ Coum)', MUmoaotL 1bc; MPCA WDQU1 \\1di
Jf Altemative 3 for remedial actioa It this sile. The ICIeded ranedi&l actioa iDc1udes the
.onapoacGU:
- ID8'dan1oaa1 controts;
. aroUnd water-extractioft Uttough recovery wcUs;
. fi1tra1ioa to remove suspeaded lO1ids~ .
. a1umiDa adsorption In FI!rMYe diasolwd phue anezUC;
. di8cbarp ofueated groumt ~tter 1broup aD iDfi1traticm p11er)'; 8Dd
- QDI r81ide,1 hookup to tho muW,ipal wa&cr supply,
EI&imated preaem warda cast oftbB remedial a=ca is 52.5 millioD. Estimar.ed pracat WOI1h coit of
operatiOD aDd Iftaiftbtl'l~ 5173.000 per year for aix yeara.
The MPCA bclicws mat tbe selec:ta! remedial action for !lie Perham Ar8eaio .ite provUloa tho belt "'-1_-
amq the altemaziws \\. ewluued IpiDIt the aiae criteria let imh in the NatioIIaI CoariDpacy PIm
~. y
~W .
r~ uru." rr
CWW:ch .
=: Thomas Bloam., V.S. EDviroameDta1 p~w Agcuc;y
go L8fayd8 Ad. N.: 61. Paul. MN 551aH184; (812) 286«SOO (VOICe); (812) 212-6332 (TTY)
A8gtonaI Otfica: Duluth. B~nerd . D8troIt L.Ik8I. Maf8h1J1. Racf8f8r
.quIII OpportunIty ~. Prtnt8cI on ~ PIIP8f DaIII8InIng .... 1ft ftD8rl frDm PlP8f rIOJCIId bV........
-. .- -. . '.". ."-
. .
'_._'~"- -.-
. "
~."-.- ----.~~.-..- ._. -'. .--. _.. ... .
-------
..." ~....'
ATTACHMENT 2
RESPONSIVENESS SUMMARY
I.
OVERVIEW
The public reacted agreeably to the proposed plan for
remediation of groundwater at the Perham Arsenic Burial Site.
Questions posed during the public meeting on February 22, 1994,
were mostly directed toward the technical aspects of the site.
Questions also were asked about absorption and desorption
properties of arsenic at the site. All questions and concerns
were addressed during and after the public meeting. One oral
comment was received during the public comment portion of the
public meeting, and is addressed in this responsiveness
summary.
II.
BACKGROUND ON COMMUNITY INVOLVEMENT
Through news releases, news media contact, and meetings with
public and private citizens of Perham, U.S. EPA and MPCA have
kept Perham residents informed of all developments at the site.
In 1983, issues associated with the RIfFS, were discussed with
city staff and officials, and members of the Arsenic Action
Committee. Through meetings with city personnel, fact sheets,
articles published in the city newspaper, and the public
meeting, recent remedial activities have been presented.
III.
SUMMARY OF PUBLIC COMMENTS AND LEAD AGENCY RESPONSE
One comment regarding the site was made during the public
comment portion of the public meeting. Written comments on the
proposed plan were not received. A response to the comment is
available in this Responsiveness Summary.
In addition to the formal comments made on the proposed plan,
discussions with state personnel, during the public comment
period, were held. The discussions were in regard to the
adjacent residential well and the possibility of providing
municipal water to the adjacent residence. The possible hook-
up to the municipal water supply would act as a safeguard,
should groundwater flow direction change in the future. Public
and state comments are addressed in this response.
Comment
1. My name is Tom Hammers. I think it's imperative and my
comment is that this mess get cleaned up as soon as possible.
This pit is a killer. It crippled my uncle, I've got permanent
disability, and I believe it caused the cancer that killed my
dad.
This thing is a killer and
cleaned up. We've got to make
it's as cleaned up as it could
somebody 50 years from now.
I think we ought to get it
sure we understand and know that
possibly be so it don't kill
-------
-
2
Response
Results of the most recent investigations indicate that the pit
area no longer poses a threat. However, arsenic contaminated
groundwater, which originated from water infiltrating through
the former pit area, does pose an unacceptable risk. u.s. EPA
and MPCA plan to begin remedial design phase of the clean up in
September of this year. The site clean up schedule allots one
year for design, followed by a construction and start up period
ranging from sixteen months to two year. Completion of the
remedial action is scheduled for the fall 1997.
Comment
2. Taken from Conversation Record with between Thomas Bloom,
u.s. EPA and Todd Goeks, MPCA, dated March 11, 1994.
Todd and I spoke about the possibility of providing
municipal water to the resident just south of the site. We
agreed that currently there is no threat to the resident from
the groundwater plume on site. However, if in the future, a
farmer were to install a high-yield agricultural type well in
the farm fields south of the resident, the groundwater plume
from the site could be pulled south towards the residential
well.
I told Todd that I have already discussed the possible hook
up with Bob Louiseau, the City Manager. I told Todd that he
(Bob Louiseau) told me that since there is already a water
supply line running along adjacent to the street, the hook up
operation would be an easy one. .
Todd and I also discussed the fact that it may be more cost
effective to hook the resident up to a municipal drinking water
supply, than to monitor the well quarterly as part of the
remedial action monitoring plan.
Response
u.s. EPA agrees that if groundwater flow conditions change at
the site due to installation of an agricultural well to the
south of the adjacent resident, the resulting change in plume
direction could put the adjacent resident at risk. U.S. EPA
concurs with the state on this issue and plans to include the
hook up to municipal water supply for the adjacent resident in
the remedial action.
-------
.~
ATTACHMENT 3
INDEX OF THE ADMINISTRATIVE RECORD (REVISION 1)
DATE DOCUMENT TITLE AUTHOR RECIPIENT TYPE
10/92 FINAL RI/FS WORKPLAN M&E USEPA PLAN
11/92 FINAL QAPP M&E USEPA PLAN
11/93 FINAL REMEDIAL INVESTIGATION M&E USEPA REPORT
11/93 FINAL ALTERNATIVES ARRAY M&E USEPA REPORT
2/94 FINAL FEASIBILITY STUDY M&E USEPA REPORT
2/15/94 PROPOSED PLAN USEPA PUBLIC PLAN
2/22/94 TRANSCRIPT OF PUBLIC MEETING USEPA PUBLIC TRANSCRIPT
------- |