United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R02-88/071
September 1988
3EPA
Superfund
Record of Decision
Upjohn Manufacturing Company, PR
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REPORT DOCUMENTATION i- TSPORT NO. 2.
PAGE EPA/ROD/R02-88/071
4. Title and Subtitle
3UPERFUND RECORD OF DECISION
•^Jpjohn Manufacturing Company, PR
Mpirst Remedial Action - Final
^. Author(s)
9. Performing Organization N»me and Address
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
401 .M Street, s.W.
v^ashington, D.C. 20460
3. Recipient's Accession No.
5. Report Date
09/30/83
6.
8. Performing Organization Rept. No. ]
10. Project/Task/Work Unit No.
11. Contract(C) or Grant(G) No.
(CD
(G)
13. Type of Report & Period Covered
300/000
14.
15. Supplementary Notes
f
k
16. Abstract (Limit: 200 words)
The Upjohn Manufacturing-Company (UMC) site is located in the Barceloneta industrial
park on the north coast of Puerto Rico. Land use in the surrounding area is industrial,
agricultural, and rural residential. The site is in a sparsely populated rural region
and lies above the island's largest aquifer, which serves as a source of drinking water
for over 12,000 area residents. In addition, the aquifer discharges to a wetland area
the north, whicn' supports a large aquatic and bird population. The site lies in a
imestone region characterized by karst terrain developed by dissolution of the existing
limestone formations, and typified by closed depressions, sinkholes, and subsurface
conduits. Between August and September 1982, UMC dispatched approximately 15,300
gallons of a manufacturing by-product waste mixture estimated to be comprised of 65
percent carbon tetrachloride and 35 percent acetonitrile to a leaking underground
storage tank (UST), resulting in the release of all of the waste into tne ground.
Investigation by UMC determined that carbon tetrachloride contamination had migrated
offsite approximately 2 miles to the nortn and occupied an area of about 2.1 mi .
Consequently, five local water supply wells were closed in 1932 due to the potential for
carbon tetrachloride contamination, and UMC provided a permanent alternate water supply
to users. In 1933, UMC began implementing remedial actions to remove carbon
(See Attacned Sheet)
f s???nr""or'
Upjohn Facility, PR
First Remedial Action - Final
Contaminated Media: gw
Key Contaminants: carbon tetrachloride
b. Identifiers/Open-Ended Terms
COSATI Field/Group
Availability Statement
19. Security Class (This Report)
Hone
20. Security Class (This Page)
None
21. No. of Pages
86
22. Price
(See ANSI-Z39.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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\
KA/ROD/R02-88/071
John Facility, PR
First Remedial Action y Final
16. ABSTRACT (continued)
tetrachloride from the soil and ground water: this included the installation and
operation of a vacuum extraction system until March 1988; ground water pumpage from the
AH Robins well adjacent to and north of the site until 1985; installation and operation
of a second ground water contaminant recovery extraction well, UE-1, on the UMC facility
in 1984, with air stripping and residual discharge to a sinkhole; and placement of a
concrete cap over the tank farm. In 1987, because of residual ground water
contamination that has remained both on and offsite, EPA ordered UMC to continue its
remedial activities including resuming operation of the vacuum extraction system,
pumping extraction well UE-1, and ground water monitoring, as well as determining the
feasibility of restoring all or portions of the aquifer to health-based levels. This
ROD.addresses the residual ground water contamination resulting from the 1982 UST leak
at the UMC facility. The possibility of residual contamination in the soil as a
continuing source of carbon tetrachloride contamination in the ground water will be
addressed by the EPA RCRA program and will not be a part of this remedial action. The
primary contaminant of concern affecting the ground water is carbon tetrachloride.
The selected remedial action for this site includes: ground water pump and treatment
from the UE-1 and AH Robins wells using air-stripping, followed by discharge of the
treated water to'an existing sinkhole; ground water pump and treatment using air
^tripping from the public supply well followed by distribution to the public water
Bipply system; installation and operation of two to four additional offsite extraction
wells with air stripping and recharge to the ground water; installation of chloride
monitoring wells near the coastline to monitor potential salt-water encroachment; and
long-term ground water monitoring. Because it is not known whether contaminant levels
in the aquifer can be reduced to the MCL, EPA will re-evaluate this remedy within five
years of operation to determine the allowable contaminant levels that must be met before
the extraction wells are shut down. If a decision is made that any portion of the
aquifer will not be restored, a waiver from the MCL for reasons of technical
impracticability will be evaluated at that time. The estimated capital cost for this
interim remedial action is $2,200,000-$6,200,000 with annual O&M of $400,000-$700,000.
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DECLARATION STATEMENT
RECORD OF DECISION
SITE NAME AND LOCATION
Upjohn Manufacturing Company
Barceloneta, Puerto Rico
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for the Upjohn Manufacturing Company (UMC) Site, in Barceloneta,
Puerto Rico, developed in accordance with CERCLA, as amended
by SARA, and to the extent practicable, the National Contingency
Plan. This decision is based on the administrative record
for this site.
The Commonwealth of Puerto Rico has concurred on the selected
remedy.
DESCRIPTION OF THE SELECTED REMEDY
This ROD addresses the residual carbon tetrachloride (CC14)
groundwater contamination resulting from the 1982 underground
tank leak at the UMC facility. The response action will
address the principal threat posed by the groundwater contam-
ination at the site.
The major components of the selected interim remedy include:
" Continued pumpage of ground water extraction well UE-1 at
840 gpm with treatment by an upgraded air-stripping system
and discharge to an existing sinkhole located northwest
of the UMC facility.
0 Pumpage of the AH Robins well at 450 gpm plus the
installation and pumpage of two new extraction wells each
at 800 gpm, with treatment by the UE-1 air-stripping
system and discharge to the existing sinkhole.
" Continued pumpage of the Garrochales #3 public supply
well (not currently treated) at 2000 gpm with treatment'
by air stripping and subsequent distribution to the
public water supply system. An evaluation of replacing
this Well with an artesian well will be conducted during
design. Because this well is not an integral part of the
remediation scheme, it may be taken out of service if it
is replaced.
9
" If the two new extraction wells prove to be effective at
removing contaminants from the aquifer, additional
extraction wells will be added, in a phased approach,
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with treatment by air stripping and recharge to the
groundwater. It is estimated that two to four additional
wells will be installed and pumped at approximately 800
gpm each.
0 Installation of chloride monitoring wells near the
coastline to monitor potential salt water movement.
0 Long-term monitoring of groundwater to track contaminant
movement and assess performance of the groundwater extraction
wells.
0 A reevaluation of the interim remedy within five years of
operation to determine whether it should be continued or
modified.
DECLARATION
Consistent with the Comprehensive Environmental Response, Com-
pensation, and Liability Act of 1980 as amended bV the Superfund
Amendments and Reauthorization Act of 1986, and tjhe National Oil
and Hazardous Substances Pollution Contingency Plan, 40 CFR Part
300, I have determined that the selected interim remedy is
protective of human health and the environment consistent with
the purpose of this remedial action. For groundwater extracted
and treated, the remedy attains federal and state requirements
that are applicable or relevant and appropriate. Consistent
with the scope and purpose of this interim remedy, this
action is cost effective and utilizes permanent solutions and
alternative treatment technologies to the maximum extent
practicable. This action satisfies the statutory preference
for remedies that employ treatment that reduces toxicity,
mobility, or volume as a principal element.
Because this remedy will result in hazardous substances remaining
on-site above health-based levels, a review will be conducted
within five years after commencement of remedial action to ensure
that the remedy continues to provide adequate protection of human
health and the environment.
Date
William J.
Acting Reg
, P.E.
inistrator
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ROD DECISION SUMMARY
SITE NAME, LOCATION, AND DESCRIPTION
The Upjohn Manufacturing Company (UMC) site is located on the
north coast of the island of Puerto Rico in the Barceloneta
industrial park, a rural region approximately 1.6 miles west of
"Cruce-Davila," which is the local name for the intersection of
State Roads 2 and 140 (see Figure 1). This area lies on a five-
mile wide coastal plain with regional topography sloping gradually
down to the north and to the Atlantic Ocean which lies about 3.7
miles to the north. Small hills known as mogotes surround the
facility. Across the road from the UMC property is the AH Robins
Company and the Tiburones community. Nearby to the north is the
Cambalache State Forest (see Figure 2).
The site is located in the north coast limestone region of Puerto
Rico. This sparsely populated area lies above the island's
largest aquifer, which serves as a source of drinking water to
over 12,000 area residents who rely on public and private wells.
The region is traversed by six rivers whose headwaters!are found
in the volcanic terrain to the south, and which flow northerly to
the Atlantic Ocean. The UMC site lies in the drainage area
bounded to the west by Rio Grande de Arecibo and to the east by
Rio Grande de Manati. The Cano Tiburones forms the northern
boundary.
The region is characterized by a tropical, mature karst terrain
which includes closed depressions, sinkholes (dolines), subsurface
conduits and an absence of surface water bodies. The karst
developed by dissolution of the existing limestone formations.
Blanket sands fill the depressions or valleys between the mogotes,
at depths ranging from approximately 3 feet to greater than 100
feet.
The Aymamon and Aguada formations comprise the unconfined water
table aquifer which has high values of permeability. The total
thickness of these formations is approximately 709 feet and 1086
feet, respectively. The water table can be found approximately
300 feet below the spill site at UMC within the Aymamon Formation
(see Figure 3). Below the Aguada Formation lie the Cibao and
Lares formations which comprise the confined artesian aquifer.
The total thickness of each of these formations is approximately
1004 feet and 1017 feet to 1657 feet, respectively (see Figure 4).
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The Aymamon limestone is subject to high degrees of weathering
and dissolution into underground cavities, usually following
vertical regional faults. Two sets of vertical faults intersect
in this region at right angles, leaving residual hills -and sinkholes.
Due to the cavernous nature of the formation, the transmissivity
and productivity of the Aymamon limestone is high. Although
vertical transmissivity is reduced by the inter-bedded clay
layers, it is locally facilitated by sinkholes.
The Aguada formation is a more massive, less cavernous, and more
resistant limestone with a lower lateral and vertical transmissivity
than the Aymamon.
In the vicinity of UMC, groundwater within the water table aquifer
generally flows to the north or slightly northeast, towards its
discharge point into the Cano Tiburones, and ultimately the
Atlantic Ocean. However, with flooding conditions, the general
groundwater flow has been observed to be toward the northwest.
SITE HISTORY AND ENFORCEMENT ACTIVITIES
In mid August 1982, UMC resumed, after one yea,r,, a batch production
process for the manufacture of the antibiotic 'Clindamycin, at •
their Barceloneta facility in Puerto Rico. This process generates
a waste mixture of carbon tetrachloride (CC14) and acetonitrile.
Between August 16, 1982 and September 3, 1982, nine batch processes
were run. Approximately 15,300 gallons of this mixture were
dispatched to an underground tank (identified as FA-129) (see
Figure 5) before it was realized in mid September 1982 that the
waste tank was empty and that the waste product had been released
into the ground. The chemical components of the waste stream
that entered the leaking underground tank were never carefully
quantified. However, it is believed that the composition of
material in the tank was 65% CC14 and 35% acetonitrile. Inspection
of the failed tank revealed that it had ruptured in at least three
locations. Inspections of most of the remaining tanks in the
tank farm indicate the possible leakage from these tanks prior to
the loss of waste stream in 1982. Possible spills from loading
and unloading stations near the tank farm as well as from maintenance
work on pipe and tank fixtures may have contributed to the contam-
ination at the site, which may have been occuring before August
1982.
Five local water supply wells (Garrochales #1 and #2, Tiburones,
AH Robins, and Hillside Motel) were shut down due to CC14 contam-
ination or the threat of contamination resulting from the spill.
Acetonitrile was not detected in any well. UMC, along with
several local industries, provided a temporary alternate water
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supply to the users of those water supply wells until a permanent
alternate water supply was provided for by UMC., UMC replaced the
Puerto Rico Aqueduct and Sewerage Authority (PRASA) public supply
wells, Garrochales #1 and #2, with a new water supply well, the
Garrochales #3 well. To date, water from this well has not been
provided with any type of treatment before being distributed •
through the PRASA water supply system.
Results of soil and groundwater investigations conducted by UMC
following the spill indicated the presence of CC14 contamination
in the soil and groundwater. Soil investigations delineated the
zones of highest contamination within the unsaturated zone in and
around the tank farm. Investigations revealed that most of the
CC14 remained within the upper blanket sand deposits 25 to 100
feet below the ground surface in the unsaturated zone. Exceptions
were noted, however, where elevated levels of CC14 were found in
very deep deposits of the blanket sands at depths ranging from 100
to 210 feet below the ground surface.
Considering the impracticality of excavating soil to such depths,
a vacuum extraction sysltem was installed by UMC at the site in
1983, which removed CC1J4 vapors from the soil. Each vacuum
extraction well in the system was in operation until nondetectable
levels of CC14 vapors were observed over a period of time. The
system was shut down in its entirety in March 1988.
Groundwater investigations conducted by UMC included the installation
of 22 groundwater monitoring wells (MW-1 through MW-23, excluding
MW-2), from November 1982 through December 1983, in the vicinity
of UMC (see Fig. 6). Samples from these wells were used to
determine groundwater quality, flow direction and rate of movement.
Based on data collected from the monitoring wells, it was determined
that the CC14 contamination in the groundwater had migrated off
site approximately 2 miles to the north. Acetonitrile was not
detected in the water table aquifer nor in the underlying artesian
aquifer. Trace amounts of CC14 were occasionally detected in the
underlying artesian aquifer, but the mean concentration was less
than 0.5 parts per billion (ppb).
In 1983, UMC, with the support and oversight of the major regulatory
agencies on the island, began implementation of remedial actions
in attempts to remove the CC14 from the soil and groundwater.
These actions included: the pumpage of the AH Robins well, the
.first well outside of the UMC facility at which CC14 associated
with the UMC spill was detected, as a means of recovering the
contaminated groundwater; the installation and operation of a
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vacuum extraction system, an innovative technology, within the
UMC tank farm soils to remove CC14 vapors from the unsaturated
zone; the installation and operation of a second groundwater
contaminant recovery extraction well, UE-1, located on the UMC
facility; and placement of a concrete cap over the tank farm to
eliminate precipitation infiltration and reduce the migration of
CC14 from the soil into the groundwater.
The UMC site was placed on the National .Priorities List (NPL) in
September 1983. In May 1984, UMC drafted a Remedial Investigation/
Feasibility Study (RI/FS) Report which documented the soil and
groundwater investigations as well as the remedial actions taken
by UMC to remove CC14 from the soil and groundwater and to provide
alternate water supplies. EPA did not accept the 1984 draft
RI/FS Report prepared by UMC because the extent of groundwater
contamination had not been fully defined and the FS was not
performed in accordance with the National Hazardous Substances
Pollution Contingency Plan (NCP).
The use of the AH Robins well as a groundwater contaminant recovery
well was discontinued in 1985 because of the greater effectiveness
of well UE-1, which became operational in 1984.
UMC has continued to operate well UE-1 as a groundwater extract-
ion well, discharging treated water from an air-stripping unit to
an existing sinkhole, and has continued to sample selected ground-
water monitoring wells and threatened water supply wells on a
monthly basis.
Both soil and groundwater treatment systems were effective in
removing contaminants from the environment. However, residu'al
CC14 contamination has remained in the groundwater on site and
has migrated off site as well. It is possible that residual CC14
may also exist in the unstaturated zone on site.
On June 26, 1987, EPA issued an Administrative Order on Consent
to UMC which required UMC to perform additional remedial investigative
studies as well as prepare a feasibility study with respect to
the site in order to, among other things, gather further information
about the groundwater contamination at the site and address
alternatives for its remediation. The order also required UMC to
continue to pump its groundwater extraction well (UE-1) and its
vacuum extraction wells, conduct groundwater monitoring," and
perform certain other actions. One of the primary objectives of
this order was to ensure that the feasibility study to be prepared,
would conform to the requirements of the Comprehensive Response
Compensation and Liability Act of 1980, as amended by the Superfund
Amendments and Reauthorization Act of 1986 (CERCLA), and the NCP.
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Pursuant to the June 26, 1987 Administrative Order, UMC submitted
an RI Report, a draft FS Report and, after receiving comments
from EPA, an amended FS Report. However, EPA found these reports
to be deficient. EPA thus tasked its contractor, Camp Dresser &
McKee Federal Programs Corporation (CDM-FPC), to perform additional
groundwater sampling to define further the extent of CC14 contam-
ination and to verify existing data from UMC, and to prepare a FS
Report to address the residual groundwater contamination. The
CDM-FPC FS Report was completed and accepted by EPA in June 1988.
COMMUNITY RELATIONS
The 1988 Draft FS Report, prepared by CDM-FPC, was released for
public comment along with the Proposed Remedial Action Plan
(PRAP) on July 12, 1988. The 30-day comment period concluded on
August 10, 1988. A public meeting was held on July 21, 1988 at
the Barceloneta Mayor's Office to discuss the FS and PRAP, answer
questions, and solicit citizens' comments. A response to each
significant comment received during the public comment perioa is
included in the attached Responsiveness Summary. i
.1 *
SCOPE and ROLE of RESPONSE ACTION
This ROD addresses the residual CC14 groundwater contamination
resulting from the 1982 underground tank leak at the UMC facility.
The response action will address the principal threat posed by
the contaminated groundwater at the site.
It is possible that residual CC14 contamination may exist in the
unsaturated zone which may represent a continuing source of CC14
contamination to the groundwater. This possible source will be
addressed separately by the EPA RCRA program and will not be part
of this ROD.
SITE CHARACTERISTICS
Extent of Contamination
The chemical components of the waste stream that entered the
leaking underground tank were never carefully quantified. UMC
reported the composition of material in the tank to be 65 percent
CC14 and 35 percent acetonitrile. Chloroform and methylene
chloride are decomposition products of CC14; therefore, it is
likely these compounds were also present in the spill ana/or in
the soil and/or groundwater soon after the spill.
Qualitative analyses by UMC of the vented fumes and collected
liquids from the vacuum extraction system in the soil indicated
the presence of CC14, and traces of acetonitrile, acetone,
chloroform, methylene choride and methane. This indicated that
these same substances were also present in the unsaturated
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zone beneath the tank farm at UMC. Since CCJ.4 was the major
constituent of the chemicals detected, it is the only chemical
that was quantitatively analyzed by UMC in the unsaturated zone
and, for the most part, in the saturated zone.
The vacuum extraction system operated in various configurations
until it was shut down in March 1988, when analysis of vented
soil vapors revealed nondetectable levels of CC14 from the vacuum
extraction wells. Although the system was successful in removing
CC14 vapors from the unsaturated zone down to nondetectable levels,
the system was not capable of removing CC14 which had adsorbed to
the soil particles. Given CCl4's high retardation factor and
kinematic viscosity which enables the chemical to exist in the
unsaturated zone in a separate, pure liquid phase, it would be
expected that some CC14 is presently adsorbed to the organic
carbon of the blanket sands and will remain a persistent secondary
source of contamination as the pure CC14 product solubilizes in
the water between the soil particles over time and migrates into
the aquifer. The amount and location of CC14 which presently
exists in the unsaturated zone is unknown. ,
From 1982 to 1987, UMC sampled"selected groundwater monitoring
and water supply wells for CC14 on a regular basis. These data
was used to track the movement of contamination resulting from
the 1982 spill.
CC14 contaminant data from groundwater monitoring wells in the
immediate vicinity of the UMC facility showed that concentration
levels had decreased significantly since the time of the incident.
Monitoring wells 1, 8 and 10 which exhibited the highest concen-
tration levels of CC14 in 1983, greater than 30,000 ppb, had
decreased to less than 150 ppb in 1987. Natural aquifer flushing
and dilution would have contributed to this decrease in concen-
tration levels.
Groundwater data collected from 1982 to 1987 revealed the general
direction of the migrating CC14 contamination to be north/northwest
The areal extent of the contamination measured in 1987 encompassing
concentrations of 5 ppb or greater was approximately 2.1 square
miles (see Figure 7).
1988 groundwater samples collected by EPA's contractor, CDM-FPC,
were analyzed for Target Compound List (TCL) volatile organics,
metals and cyanide through the EPA Contract Laboratory Program.
Wells that were sampled are located on Figure 8. Samples collected
from stainless steel monitoring wells MW-101, 102 and 103
(constructed in 1987) were analyzed for both TCL metals'and
dissolved metals.
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Results from 1988 data, presented in Table I/ show CC14 concen-
trations exceed the Maximum Contaminant Level (MCL) of 5 ppb for
CC14, established under the Safe Drinking Water Act, in monitoring
wells 1, 16, 18, 21, 22, 23, 101 and Vaqueria Sabaria (1305), a
stock well. Samples collected from a spring, La Cambija (#52),
which feeds into the Cano Tiburones were also found to contain
CC14 concentrations in excess of 5 ppb. Monitoring wells 16,
18, and 23 contained the highest CC14 concentrations of 140, 160
and 170 ppb, respectively. These wells also contained the
highest levels of chloroform, although the levels were less
than the Puerto Rico Department of Health maximum contaminant
level standard for any single organic chemical. Acetonitrile
was not detected at any of the sampling locations.
Acetone was detected in groundwater samples from monitoring
wells 1, 21, 23 and 101 at corresponding concentrations of 61,
41, 26 and 37 ppb. The fact that acetone was also found in the
field blanks, however, indicates this compound may be residual
from decontamination of the sampling equipment and, therefore,
not indicative of groundwater contamination.
D
Toluene was detected at 24 ppb in we'll 48, which is no longer
in use as a domestic well. However, this concentration was
below the recommended MCL, proposed in the Federal Register
on November 13, 1985 pursuant to the Safe Drinking Water Act.
High concentrations of iron, calcium, magnesium, sodium and
potassium were detected in many of the wells. These ions are
naturally found in carbonate limestone aquifers that are not in
contact with salt water.
Arsenic and selenium were found in abandoned well 51, at elevated '
levels which exceeded primary drinking water standards. In
addition, lead concentrations at well 54 exceeded primary
drinking water standards. Well 54 is currently used for irrigation
purposes. The presence of arsenic, selenium and lead in the
groundwater may be attributable to contamination originating
from local industries.
Levels of chromium in excess of the MCL of 50 ppb were found at
monitoring wells 101, 102 and 103. Dissolved metal concentrations
in these wells were, however, considerably lower than the
corresponding total metal analysis. Since excessive levels of
chromium were only detected in 3 out of 26 locations sampled in
January 1988, EPA does not believe that the metals detected
(particularly chromium) are necessarily indicative of groundwater
contamination. EPA believes that the presence of metals may be
attributable to well development. However, it is also possible
that chromium may be a result of contamination originating from
local industries.
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The highest CC14 concentrations detected in January 1988 by EPA
coincide with the highest concentrations found in 1987 by UMC.
Currently, the leading edge of the extent of CC14 contamination,
however, appears to be located considerably south of the
Garrochales #3 well (see Figure 9).
The zone of contamination addressed in the 1988 draft FS report
was interpreted by superimposing the yearly maximum CC14
concentration gradients from 1983 through 1987 (see Figure 10).
This effort has revealed a consistently higher level of CCl^
contamination in the area between UMC and well #54.
Concentration gradients constructed from the 1988 groundwater
data indicate that the major portion of the residual CC14
contamination currently existing in the groundwater is within
this same zone that has historically revealed the highest CC14
concentrations.
Data provided by the United States Geological Survey (USGS)
indicate that there are no private wells used for drinking
water located within the zone of contamination. Wells within
the zone of contamination are located on Figure 11.
Based on the current location of the groundwater wells, the
bulk of residual CC14 contamination currently existing in the
groundwater has been identified within the diffuse component of
the flow, to extend approximately 8,500 to 9,500 feet north of
the UMC site (see Figure 12).
A small portion of CC14 contamination detected in well #305 and
in a spring feeding into Cano Tiburones was not evaluated in
subsequent remediation schemes since the contamination is
already appproaching a point of discharge from the aquifer.
At the point of discharge, CC14 concentrations are expected to
decrease, possibly to less than the MCL of 5 ppb for CC14, due
to dilution and volatilization of the contaminants.
Pathways of Migration
CC14 has a moderate to strong tendency for adsorption to soil
particles. Some adsorption of CC14 and chloroform to the organic
carbon of the blanket sands is expected. The denser-than-water
nature of pure CC14 liquid may cause the chemical to flow faster
than water through the blanket sands and sink through the water
table of the Aymamon aquifer. Some degradation of CC14 to
chloroform is expected.
CC14 may remain in the blanket sands or limestone aquifer as a
secondary source of contamination as pure liquid, dis'solved
chemical, or contaminated soil and soil air. As precipitation
percolates downward through the blanket sands, CC14 may be
I
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flushed downward through the sands. This periodic flushing may
cause pulses of contamination to enter the aquifer system
during rain events.
Most of the acetonitrile probably went into solution in the
water between the soil particles with some lost to volatilization
and diffusion. Once dissolved/ it would have moved through the
soil and into the underlying Aymamon aquifer. Little acetonitrile
should remain in the soil. That which reached the limestone
aquifer may have been flushed relatively rapidly.
Chloroform may exist as a degradation product of CC14. Further
degradation may occur, but volatilization from soil or groundwater
is a more likely removal pathway. Chloroform w'ill not be as
retarded by organic matter in soil as CC14. It I] is unlikely
that chloroform would exist in a pure liquid steite in the
blanket soils or Aymamon aquifer. ;
;l
. I
Groundwater flow in the karstic Aymamon aqui fer 'occurs as a
combination of flow through the dissolution channels (conduit
flow) within the limestone and flow through the {'surrounding
intact limestone (diffuse flow). Hydrogeologica'il studies
conducted in the Barceloneta area indicate that 'jdif fuse flow is
more prevalent in the immediate area than conduit flojw. Because
of this, contaminant recovery using groundwater'extraction wells
is feasible, given properly located wells.
Any contamination present in the groundwater 'in a dissolution
channel will be rapidly transported through the aquifer.
Contamination present in the groundwater of the limestone will
move much slower. Such differences in velocity .and flow direction
will spread or disperse contaminants as they move away from a
contaminant source.
In addition, the limestone may serve as a reservoir for contam-
inated water, resulting in a persistent, low level source of
contamination to the dissolution channel flow from the limestone,
causing a temporal dispersion of the contamination.
Groundwater Characteristics
The aquifer system is dynamic, changing rapidly in flow amount
and direction with changes in rainfall amount or pumping. The
shift in flow amount or direction may cause widespread dispersion
of contaminated water throughout the aquifer. This spatial and
temporal dispersion of contaminants leads to difficulties in
designing aquifer remediation systems and in estimating aquifer
clean up times.
Another significant feature of the water table aquifer is the
presence of salt water within the Aymamon and Aguada Formation.
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Any remedial activities that include new or increased groundwater
pumping must be evaluated in terms of the potential for "causing
the salt water interface to move further inland.
Salt water encroachment can be expected if pumpage exceeds the
natural storage capacity of the aquifer. Also, pumping wells
should be designed to avoid local up-coning of salt water
beneath the wells. Any pumping of groundwater should include
eventual recharge back into the aquifer to maintain the balance
of freshwater flow.
i
The USGS recommends a maximum pumpage lirifit of the Aymamon
limestone aquifer in this area of 6 million gallons per day
(mgd) during periods of normal or surplus; precipitation to
prevent salt water intrusion. ,,;
' i
EPA has proposed a groundwater classification system for addressing
groundwater use. The unconfined Aymamon/Aguada aquifer has been
classified as Class II groundwater. This,! classification is
outlined in "Guidelines for Groundwater Classification under
the EPA Groundwater Protection Strategy" 'j- Finlal Draft (Office
of Groundwater Protection WH-550G). ; |
The draft Puerto Rico Groundwater Strategy classifies all
groundwater as Class II, unless otherwise demonstrated. For
this reason, and due to the fact that the water table aquifer
is not irreplaceble, the Class II characteristic (current or
potential source of drinking water) is being used. This implies
that remediation levels be considered to .provide protection of
public health and that active restoration of the groundwater be
achieved over a reasonable period of time with greater emphasis
placed on shorter time frames.
SUMMARY of SITE RISKS
At the UMC site, CC14 and acetonitrile were known to be present
in the waste stream, and are therefore considered the contaminants
of concern for the site. Acetonitrile was not detected at any
sampling location in 1988. Chloroform would be expected to be
present as a degradation product of CC14. Chloroform was
detected at only three well locations.
The primary exposure mechanism and public health risk at the
UMC site is attributable to the ingestion or other domestic
use of contaminated groundwater downgradient from the UMC
site. Although the primary exposure route is through ingestion
of groundwater, other exposure mechanisms such as inhalation
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of volatile components during showering, dermal contact during
bathing, and inhalation of volatiles released by the air-stripping
unit presently operating at the site (for plant workers only)
for the UE-1 groundwater extraction well also exist.
Land use in the zone affected by contaminant migration is
industrial, agricultural and rural residential. At least
several manufacturing plants, the communities of Tiburones and
Garrochales, a Job Corps facility and.a motel are affected.
All users of the unconfined aquifer in the affected zone are
potentially endangered. However, as stated previously, according
to USGS, no private wells within the zone of contamination
currently utilize the groundwater for drinking water purposes.
All contaminated and threatened potable wells were shut down
shortly after discovery of the spill in 1982. UMC replaced the
water supplies to the users of these wells. Artesian well
users have not been endangered in the past and the potential
for future endangerment is small. The Garrochales f3 well,
which replaced the #1 and #2 wells, .is currently the only user
of the unconfined aquifer for potable water in the affected
zone. Private wells located north of the Garrochales #3 well
currently use the unconfined aquifer for watering livestock and
for irrigation purposes.
Other potentially endangered populations include workers at the
UMC plant potentially exposed to contamination through inhalation
of vapors from the UE-1 air stripper. Also, users of the Cano
Tiburones could potentially be exposed through surface water
contact and use.
Ingestion of contaminated fish and contaminated crops (including
meat from livestock) are exposure pathways with little potential
for adverse human health effects. Concentrations of contaminants
and 'bioconcentration factors for CC14 are low, resulting in
minimal uptake by fish and crops, thus resulting in a low potential
for exposure.
Noncarcinogenic effects associated with ingestion of groundwater
and inhalation of volatilized groundwater contaminants were
examined through comparison of chronic daily human intake
values (an estimated dose which a human receives) to the
acceptable intake value for chronic exposure (the estimated
dose level believed to be safe). There are unacceptable chronic
noncarcinogenic risks for children living in the area affected
by the UMC site and ingesting groundwater. For adults,
unacceptable risk would, be produced by ingestion of groundwater
at the AH Robins well. No unacceptable noncarcinogenic risk
exists for inhalation of contaminants from the air stripper at
the UMC site.
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The risk of cancer from exposure to a chemical is described in
terms of the probability that an individual exposed for his or
her entire lifetime will develop cancer. This value is calculated
by multiplying the chronic daily intake by the carcinogenic
potency factors reported in the Superfund Public Health Evaluation
Manual (USEPA, October 1986). Cancer risks were calculated
for the chronic exposures which may occur at the UMC site.
These results are presented in Table 2.
The results indicate that chronic ingestion of the groundwater
contaminated with CC14 would produce unacceptable carcinogenic
risks to residents. The risk ranges from 2.3 x 10-4 at the AH
Robins well to 5.8 x 10-5 at the Cano Tiburones. Plant workers
may experience unacceptable carcinogenic risk by breathing
volatiles from the on-site air stripper. The risk calculated
is 1.6 x 10-5 under specific exposure conditions.
Actual CC14 concentrations in the groundwater exceed applicable
or relevant and appropriate requirements (ARARs) throughout the
affected portion of the unconfined aquifer and in the surface
water of the discharge zone. The MCL of 5 ppb for CC14 is an
ARAR for the site. Levels of CC14 in air do not exceed threshold
limit values.
The Cano Tiburones,' the discharge region of the contaminated
aquifer, is a herbaceous wetland area laced with drainage
canals. The Cano supports a large population of migratory
and native birds and waterfowl. There are sizable fish and
aquatic invertebrate populations, with recreational fishing
for channel catfish and fresh water shrimp. The Cano Tiburones
discharges into Arecibo Bay and the Atlantic Ocean.
Risks to the environment may result from chronic toxic effects of
contaminants on aquatic life of the Cano Tiburones. However,
currently, the highest amount of CC14 detected in the groundwater
(at MW-23 during January 1988) is less than the lowest observed
effects levels (LOEL) for CC14 in freshwater and salt water.
Future concentrations of contaminants entering the Cano
Tiburones are also expected to be less than the LOEL. Therefore,
impacts to aquatic life from existing and future concentrations
of contaminants are expected to be low. Risk to terrestrial
wildlife is likely to be small, since there is little contact
by wildlife with contaminated air or water.
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DEVELOPMENT OF ALTERNATIVES
The remedial alternatives for the UMC Site were developed and
evaluated using CERCLA, the NCP, a December 24, 1986 memorandum
from J. Winston Porter entitled "Interim Guidance On Superfund
Selection of Remedy" - OSWER Directive No. 9355.0-19 and the
July 24,1987 "Additional Interim Guidance for FY '87 Records of
Decision."
A range of potential available remedial technologies were
developed that cou],d be used to remediate the site. Remedial
technologies involving treatment which permanently and signif-
icantly reduces the; toxicity, mobility or volume of the hazardous
substances as a principal element, are to be preferred over
remedial technologies not involving such treatment. These
technologies were initially screened on a technical basis.
Initial screening•included the following:
'• !
0 Implementability ;r constructability and time to achieve cleanup,
0 Applicability - physical and chemical suitability for site
conditions.
Based on the screening, individual remedial technologies
appropriate to site conditions were developed.
Technologies that are not considered appropriate for utilization
at the-UMC site are- listed below.
In-Situ Treatment of Groundwater
0 Carbon Adsorption - 0014's low molecular weight and low
boiling point make carbon adsorption an undesirable treatment
technology. In addition, the presence of dissolved solids in
the groundwater and the. potential for scaling would cause
problems in the spent carbon regeneration process which would
significantly increase handling costs of the spent carbon.
0 Open Basin Aeration - Although this type of air-stripping
technology is currently used by UMC for their UE-1 extraction
well, it was not recommended for future use because of 'the
lesser degree of control and removal efficiency afforded to
the system, when compared with packed column aeration.
0 Biodegradation - Biological destruction of the CC14 was not
recommended because of the required time for metabolization to
take place. Because the contamination is in a karstic formation
where the groundwater flow moves quickly, the possibility is
great that water would reach a potable well before destruction
occurred.
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- 14 -
0 Vacuum Extraction - Applications for vacuum extraction
technologiesfor volatiles removal from the groundwater zone
have not been demonstrated based on available literature.
The application to saturated-zone volatile removal is expected
to be conceptually infeasible because of problems with
withdrawal of groundwater into extraction wells and the
limited stripping efficiency available because of the relatively
small air to water surface interface area1 compared to other
technologies, such as conventional air-stripping towers.
i ' '
Off-site; Groundwater Treatment/Discharge
[j
0 Discharge to POTW - Pumping groundwater from extraction
wells directly to a treatment plant, from which it is discharged
into tl|ie ocean, results in net exporting of groundwater from
the aquifer. This would cause salt water to intrude into the
aquifer, reducing available drinking water supplies, and
would create strong institutional and public opposition.
As a result; this option is judged to be unfavorable.
Technologies that are considered appropriate for utilization at
the UMC site are listed below.
On-site Groundwater Treatment/Discharge
0 Air-stripping - This technology has been shown to be an
effective method of removing volatile constituents from
groundwater. It is a partitioning process in which the
volatile organic contaminants are transferred from a dis-
solved state in the aqueous phase to the air phase through a
water to air transfer process. The most widely used method
of air stripping is packed column aeration. This type of
aeration is recommended for use at the UMC site.
0 Pretreatment for Scaling - Problems have been encountered
during operation of the air stripper connected to the UE-1
groundwater extraction well. It has been reported that the
stripper operates ineffectively as a result of scaling. UMC
recently installed, and is presently operating, a pretreatment
system to prevent scaling. A liquid polyphosphate scale and
corrosion inhibitor, Nalco 7399, is added to' the groundwater
before treatment. Several other chemicals used for inhibition
are available that are approved for use in potable water,
should the pretreatment system currently operating need to be
replaced. Small scale piloting will then be conducted to
determine the most appropriate chemical for the system.
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" Reinjection - Reinjection of extracted groundwater must be
done to maintain the freshwater/salt water balance of the
hydrogeological system to prevent salt water intrusion.
Reinjection of the volume of water anticipated is feasible
given the porous nature of the karst formation and the thickness
of the unsaturated zone.
DESCRIPTION OF ALTERNATIVES
Listed, below are descriptions of the four alternatives evaluated
in the CDM-FPC FS.
ALTERNATIVE 1 - No Action
This alternative (see Figure 12) involves the cessation of all'
active pumping to contain or otherwise control the spread of
CC14 contamination. Well UE-1 would be removed from service
and would either be permanently sealed or modified for an
alternate use. The Garrochales #3 well would continue to pump
at 2000 gallons per minute (gpm) without treatment and would
continue to be used as a potable water source. A long-term,
rigorous groundwater monitoring program and tracking of the
downgradient migration of CC14 contamination would be implemented.
By removing well UE-1 from service and terminating the current
treatment and recharge of effluent/ partial control of the
contamination would be eliminated. Contaminants remaining in
the unsaturated zone in the immediate area of UE-1 would continue
to slowly percolate into the water table. Contaminants already
in the groundwater, yet located outside of the effective
pumping radius of UE-1, would continue to migrate downgradient
in the prevailing direction of groundwater flow. Contaminants
currently being removed by UE-1 would also be entrained in the
groundwater. A portion of the CC14 contamination would be
intercepted by Garrochales f3; the remainder of the contamination
would eventually discharge into Cano Tiburones, and subsequently,
the Atlantic Ocean.
This alternative would not assist ,in restoring the aquifer*
Aquifer restoration would be achieved only through natural
flushing and dilution.
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-16-
CC14 concentrations may be expected to decrease as the contaminant
mass moves north and is diluted by uncontaminated groundwater.
The amount of dilution occuring is difficult to quantify since
existing data are insufficient to estimate the vertical extent
of the CC14 contamination. Whether dilution will be sufficient
to reduce bulk contaminant concentrations in the aquifer below
the MCL of 5 ppb cannot be determined. The time required to meet
the MCL of 5 ppb through natural aquifer flushing cannot be
determined since the soil beneath the site may represent a
continuing secondary source of CC14 contamination, arid the
persistence of CC14 in this type of geological environment is
not fully known.
Rigorous groundwater monitoring would be implemented to aid in
identifying potential receptors before contamination occurs
thereby allowing prudent advance action to be taken in order to
minimize potential health risks. Details of the monitoring
program would be developed in the remedial design phase.
If pumpage of UE-1 were discontinued, the only remaining principal
groundwater withdrawal from the aquifer would be from the
Garrochales #3 well which operates at 2.88 mgd which, by itself,
is well below the projected 6 mgd safe yield predicted by USGS.
Therefore, Alternative 1 would pose no threat of potential salt
water encroachment.
Implementation of Alternative 1 involves removing well UE-1
from service. This is expected to take approximately four
months.
The institutional constraints posed by Alternative 1 would
include licensing requirements for the permanent abandonment
and sealing of well UE-1.
The estimated cost breakdown for Alternative 1 is as follows:
Capital: $ 35,000
O&M : 0
Long-term Groundwater Monitoring: $440,000 .
Net Present Worth: $475,000
Costs for wellhead treatment or alternative water suplies are
not included in this alternative.
ALTERNATIVE 2 - Partial Contaminant Control
Under Alternative 2 (see Figure 13), the present operating
conditions would be maintained: well UE-1 'would continue to
pump at 840 gpm, and the Garrochales #3 well would continue to
pump at 2000 gpm. In addition, wells UE-1 and Garrochales #3
(not currently treated) would be treated by air stripping.
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- 17 -
Treated groundwater from well UE-1 would be discharged into an
existing sinkhole located northwest of the UMC -facility; treated
groundwater from the Garrochales #3 well would continue to
serve as a source of potable water. Long-term groundwater
monitoring and tracking of the downgradient migration of the
CC14 contamination would be implemented.
Under this alternative, well UE-1 would continue to provide
minimal control of the CC14 contamination. The Garrochales 13
well would intercept a portion of the contamination. Contam-
inants in the aquifer outside the zones of capture of wells
UE-1 and Garrochales #3 would continue to migrate to the north
towards Cano Tiburones. The highest concentrations of CC14,
detected north (downgradient) of the zone of capture of well UE-1,
could be expected to bypass UE-1 and Garrochales #3 and eventually
"discharge into Cano Tiburones and the Atlantic Ocean.
Partial aquifer restoration would be achieved under Alternative
2 through pumping and treating wells UE-1 and Garrochales #3.
However, because these wells are only capable of controlling a
small portion of the contaminants, aquifer restoration would
primarily rely on natural aquifer flushing.. Dilution of contaminant
concentrations would occur as the contamination migrates down-
gradient. However, the amount of dilution occuring is difficult
to quantify since existing data are insufficient to estimate
the vertical extent of the CC14 contamination. It cannot be
determined whether dilution would be sufficient to reduce bulk
contaminant concentrations in the groundwater below the MCL of
5 ppb.
The time required to attain the MCL cannot be determined for
two reasons: the soil beneath the site may represent a continuing
secondary source of CC14 contamination, and the persistence of
CC14 in this type of geologic environment is not fully known.
Alternative 2 represents a net export of groundwater of 3.1
mgd, which is less than the maximum withdrawal rate of 6 mgd,
as recommended by USGS. Therefore, this alternative poses no
threat of potential salt water encroachment.
Alternative 2 would require upgrading the existing air stripping
treatment unit on well UE-1 as well as the installation of a new
air-stripping treatment unit on the Garrochales #3 well. This
would take approximately two years. Air releases from the
treatment units would comply with air emission standards regulated
under the Clean Air Act and Rule 419 of the Regulation.for
Control of Atmospheric Pollution established by the Puerto Rico
Environmental Quality Board (PREQB). Due to the high natural
hardness and alkalinity of the groundwater, the current aeration
system on well UE-1 has encountered significant operating
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-18-
difficulties. This alternative also provides for pretreatment
of the extracted groundwater before it enters the aeration
system, which would improve the effectiveness and reliability
of the system.
The long-term use of the existing wells and upgraded existing
and new treatment units would have substantial operation and
maintenance requirements.
Groundwater monitoring would be implemented to aid in identifying
potential receptors before contamination occurs thereby allowing
prudent advance action to be taken in order to minimize potential
health risks. Details of the monitoring program would be
developed in the remedial design phase.
The estimated cost breakdown for Alternative 2 is as follows:
Capital: ? 946,000
O&M (30-year present worth) ? 1,722,000 , '
Long-term Monitoring $ 440,0.00
Net Present Worth $ 3,108,000
ALTERNATIVE 3 - Moderate Contaminant Control
Alternative 3 was developed for the purpose of controlling only
the most heavily contaminated portion of the aquifer. This
alternative involves continued pumpage, with treatment, of
wells UE-1 at 840 gpm, AH Robins at 450 gpm, and Garrochales #3
(previously untreated) at 2000 gpm, with the installation and
operation of two new groundwater extraction wells (E-l and
E-2), each operating at 800 gpm (see Figure 14). Under Alternative
3, the Garrochales #3 well would continue to be used as a
potable w t s u f wing wellhead treatment; groundwater
from wells UE-1 and AH Robins would be treated and discharged
to an existing sinkhole located northwest of the UMC facility;
the two new extraction wells would also be treated and discharged
to that sinkhole. Long-term groundwater monitoring would be
implemented. Chloride monitoring wells would be installed to
monitor potential salt water encroachment.
The installation of the two new extraction wells would be
accomplished using a phased approach, whereby hydrogeological
and water quality data from the first well would be evaluated
prior to the installation of the second well. This procedure
would provide a better understanding of the hydrogeology and
would allow for an effective placement of the wells.
The highest concentrations of CC14 would be extracted by the
two extraction wells, E-l and E-2, located in the center of
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- 19 -
the contaminated zone. The recommended locations at which
wells E-l and E-2 would be placed lie in the general area
between monitoring wells MW-16 and MW-21, where contaminant
concentrations are expected to be greatest. The two new
extraction wells, along with the AH Robins well and the UE-1
well, would be expected to remove a significant portion of the
most heavily contaminated groundwater. The two new wells are
capable of capturing approximately 30% of the total flow across
the contaminant zone. However, contaminants present in ground-
water downgradient of the two new wells would continue to
migrate towards the Garrochales #3 well and the private wells,
at concentrations of CClq as high as 170 ppb, as detected at
monitoring well MW-23 during the January 1988 sampling event.
Due to the physical barrier posed by the Cambalache State
Forest, two air-stripping systems would be required. The first
air-stripping system (an upgrade of the existing system) would
be located at the UMC property and would receive flow from
wells UE-1 (840 gpm), AH Robins (450 gpm), and the two new
extraction wells (800 gpm each). The discharge from this
treatment system would go to a sinkhole in the vicinity of the
UMC plant. The second air stripping system would be located
near the Garrochales #3 well and would service only this well
(see Figure 15). Both air-stripping systems would include
pretreatment. Sufficient land for the second system would have
to be acquired and dedicated. The flow from the Garrochales #3
well system would be used for potable purposes.
Air releases from the treatment units would comply with air
emission standards regulated under the Clean Air Act and
Rule 419 of the Regulation for Control of Atmospheric Pollution,
established by PREQB.
A chloride monitoring well network would be constructed down-
gradient of wells E-l and E-2 (see Figure 15). The chloride
monitoring wells would locate and monitor the shape and migration
of the fresh water/salt water interface prior to and during
cleanup operations. The exact location of the chloride monitoring
well network will be determined during remedial design when
sufficient data will be collected to determine the location of
the salt water interface.
A long-term groundwater monitoring program would be required
for Alternative 3 since a large portion of the contamination
would continue to migrate toward Cano Tiburones. Detai-ls of
the monitoring program would be developed in the remedial
design phase.
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- 20 -
Alternative 3 would be moderately effective in treating the
CC14 contamination to concentrations equal to or less than the
MCL of 5 ppb. However, since it relies partially on aquifer
flushing and partially on pumping and treating at the extraction
wells, EPA cannot determine whether the MCL will be attained.
The time required to attain the MCL cannot be estimated since
it is expected that the soil contaminated with CC14 would
continue to represent a persistent secondary source, and the
persistence of CC14 *n this type of geological environment is
not fully known.
A well-planned field program is needed in designing a remediation
system in the Aymamon aquifer to address both the uncertainties
caused by the incomplete data and the complexity of contaminant
transport in this karst setting. The extraction well config-
uration under Alternative.3 would require modification during
the predesign stage to optimize CC14 capture.
This alternative would require groundwater withdrawals of 7 mgd,
which exceed the recommended maximum pumpage limit of the
Aymamon limestone of 6 mgd, established by USGS. The potential
for salt water intrusion would be substantially reduced by
recharging treated groundwater back into the aquifer through
an existing sinkhole near the UMC site, as proposed under
Alternative 3.
Implementation of Alternative 3 would require upgrading the
existing treatment unit on well UE-1, the installation of a new
treatment unit on the Garrochales #3 well, the installation of
two new extraction wells, chloride monitoring wells, and the
development of permanent easements. Subject to the possible
applicability of Section 121(e)(l) of CERCLA, permits may be
necessary for the chloride monitoring wells. These items are
expected to take approximately 2 years to implement.
Moderate institutional constraints would be imposed during
implementation of Alternative 3. The installation of water
wells would require the services of a drilling contractor
meeting the licensing requirements of the Puerto Rico Department
of Natural Resources (PRDNR). In addition, permits for the
chloride monitoring wells may be required by PRDNR.
The estimated costs of this alternative are as follows:
Capital $ 2,205,000
O & M (30-year present worth) $ 4,186,000
Long-term Monitoring $ 440,000
Net Present Worth $ 6,831,000
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- 21 -
ALTERNATIVE 4 - Extensive Contaminant Control
This alternative was developed for the purpose of controlling
the bulk of residual CC14 contamination in the aquifer.
Alternative 4 includes continued pumpage, with treatment, of
wells UE-1 at 840 gpm, AH Robins at 450 gpm, and Garrochales #3
(currently untreated) at 2000 gpm, with the installation and
operation of a network consisting of seven new extraction wells
each operating at .1000 gpm (see Figure 16). Under Alternative
4, the Garrochales #3 well would continue to be used as a
potable water source following wellhead treatment; groundwater
from wells UE-1, AH Robins and E-l, a new well, would be treated
and discharged to an existing sinkhole located northwest of the
UMC facility; the remaining six extraction wells would be
treated and discharged to recharge wells located downgradient
of the extraction well network. Long-term groundwater monitoring
would be implemented. Chloride monitoring wells would be
installed to monitor potential salt water intrusion.
In order to intercept the bulk of the 'CC14 contamination and
allow an adequate degree of safety in the system, a well
extraction network would be required. The network proposed
under Alternative 4 includes the addition of seven new extraction
wells. The installation of extraction wells would be
accomplished using a phased approach, whereby hydrogeological
and water quality data from each well would be evaluated
prior to the installation of subsequent wells. In addition
to providing a better understanding of the hydrogeology, this
procedure might also demonstrate that fewer wells are required
to intercept the bulk of contamination.
The recommended zone in which the extraction wells would be
placed lies just north of the leading edge of CC14 contamination.
It is expected that the wells would be located within the zone
of contamination by the time the alternative is implemented
(estimated at 2.5 years). In addition, an extraction well,
E-l, would be placed in the general area between monitoring
wells MW-16 and MW-21 where contaminant concentrations are
expected to be greatest. The recommended recharge well zone
would lie between the extraction well zone and the point of
discharge at La Cambija spring. The recharge well zone should
not be close enough to the extraction well zone to interfere
with the movement of groundwater to the extraction wells. The
location of the salt water interface, and therefore, the zone of
recharge wells, would be determined more precisely during the
design phase. Details as to the placement of the extraction
wells depend on-groundwater data, flow rate and the extent and
location of contamination. These details would also be -addressed
during the design phase.
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Groundwater from this extraction system would first be treated
to levels of CC14 no greater than the MCL of 5 ppb through the
use of two air-stripping systems. The discharge from one treatment
system would go to an existing sinkhole in the vicinity of the
UMC plant. The discharge from a second treatment unit would be
recharged through wells located downgradient of the Garrochales
#3 well.
Due to the physical barrier posed by the Cambalache State
Forest, two air-stripping systems would be necessary. The
first air-stripping system (an upgrade of the existing system)
would be located at the UMC property, and would receive flow
from wells UE-1 (840 gpm), AH Robins (450 gpm) and extraction
well E-l (1000 gpm). The other system would be in the vicinity
of the Garrochales #3 well and would handle flows from the
remaining 6 new extraction wells (1000 gpm each) as well as the
Garrochales #3 well (2000 gpm) (see Figure 17). Both treatment
systems would include pretreatment measures. Sufficient land
for the second systemi would have to be acquired and dedicated.
The flow in excess of 2000 gpm that is used for potable purposes
would be returned to the aquifer through recharge wells»
Air releases from the treatment systems would comply with air
emission standards regulated by the Clean Air Act and Rule 419
of the Regulation for Control of Atmospheric Pollution established
by PREQB.
A chloride monitoring well network would be constructed down-
gradient from the extraction wells proposed under Alternative 4
(see Figure 17). In addition, the extraction wells would be
monitored for chloride concentrations to determine if upconing
is occurring. The chloride monitoring wells would locate and
monitor the shape and migration of the fresh water/salt water
interface prior to and during cleanup operations.
The network of seven extraction wells could be capable of
providing control of almost the entire CC14 contamination
exceeding the MCL of 5 ppb. Although there is uncertainty in
predicting zones of capture and pumping effectiveness of the
wells, the uncertainty is considerably reduced by locating a
greater number of wells than the absolute minimum.
A well-planned field program is needed in designing a remediation
system in the Aymamon aquifer to address both the uncertainties
caused by the incomplete data and the complexity of contaminant
transport in.this karst setting. Therefore, the well configuration
under Alternative 4 would require modifications during the
predesign stage to optimize CC14 capture.
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Long-term groundwater monitoring would be required under this
alternative. Details of the monitoring program would be developed
in the remedial design phase.
Alternative 4 is significantly more effective relative to all
other alternatives considered in terms of its capacity to treat
contaminants to concentrations equal to or less than the MCL of
5 ppb. This alternative relies mostly on pumping extraction
wells to restore the aquifer, rather than natural' flushing.
The time required to attain the MCL of 5ppb for CC14 cannot be
estimated since it is expected that the soil contaminated with
CC14 will continue to represent a persistent secondary source,
and the persistence of CClq in this type of geological environment
is not fully known.
This alternative could potentially require groundwater withdrawals
of approximately 14.8 mgd, which exceed the recommended maximum
pumpage limit, of the Aymamon limestone of 6 mgd, established by
USGS. However, the potential for salt water encroachment would
be substantially reduced by recharging treated groundwater back
into the aquifer through the existing sinkhole and through deep
recharge wells.
Alternative 4 would require upgrading the existing air-stripping
treatment unit on well UE-1, the installation of a new treatment
unit on the Garrochales f3 well, the installation of 7 new
extraction wells, recharge wells and chloride monitoring wells,
and the development of permanent easements. Subject to the
possible applicability of Section 121(e)(l) of CERCLA, permits
may be required for the chloride monitoring wells and the
recharge wells. These items are expected to take approximately
2.5 years to implement.
Moderate to significant institutional constraints would be
imposed during the implementation of Alternative 4. The
installation of water wells would require the services of
a drilling subcontractor meeting the licensing requirements
of the PRDNR. In addition, permits may be required by PRDNR
for the chloride monitoring wells and the recharge wells.
The estimated costs of this alternative are as follows:
Capital $ 6,199,000
O & M (30-year present worth) $ 7,882,000
Long-term Monitoring $ 440,000
Net Present Worth $14,521,000
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SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
In this section, the four alternatives are compared against
each other in relation to the following nine criteria:
1. Overall protection of human health and the environment;
2. Compliance with ARARs;
3. Long-term effectiveness and permanence;
4. Reduction of toxicity, mobility or volume of hazardous
substances;
5. Short-term effectiveness;
6. Implementability;
7. Cost;
8. State acceptance; and
9. Community acceptance.
1. Overall Protection of Human Health and the Environment
Protection of human health and the environment is the central
mandate of CERCLA. Alternatives 2, 3 and 4 provide for protection
of human health by treating the Garrochales #3 well, as a
precautionary measure, to levels meeting the MCL of 5 ppb for
CC14. These alternatives equally minimize potential risk to
human health associated with the consumption of contaminated
groundwater from the Garrochales #3 well, currently the only
well within the ione of contamination being used for potable
water.
Compared to Alternatives 1 and 2, Alternatives 3 and 4 are more
protective of the downgradient private wells used for irrigation
and livestock, with Alternative 4 providing the most protection.
Also, Alternatives 3 and 4 compared to Alternatives 1 and 2 are
more protective of unauthorized new potable wells installed
within the zone of contamination from potential risk. Unauthorized
installations would be in violation of PRDNR permitting regulations
However, their occurrence is possible.
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- 25 -
Alternatives 3 and 4 provide for greater protection of.the
environment than Alternatives 1 and 2 because of the extraction
wells proposed under Alternatives 3 and 4, which are capable of
removing significant portions of the contaminants from the
aquifer, and thereby expediting aquifer restoration. The
volume of contaminants entering Cano Tiburones would be
significantly reduced under Alternatives 3 and 4. Alternatives
1 and 2 would allow uncontrolled migration of contaminants
towards Cano Tiburones. Due to dilution though, contaminant
concentrations at that discharge area would be expected to be
very low, quite possibly below the MCL of 5 ppb. However,
Alternatives 1 and 2, which provide minimal reduction, if any,
of contaminants in the aquifer, would leave the aquifer unusable
for potable water purposes for a longer period of time.
Alternative 4 is capable of providing the most contaminant
removal and control of migration, and thereby restoring the
aquifer more quickly than the other alternatives.
o
With respect to environmental degradation due to potential salt
water encroachment, Alternatives 1 and 2 compare favorably to
Alternatives 3 and 4 because they propose no major changes in
the hydrologic balance. Alternatives 3 and 4 require groundwater
withdrawals of approximately 7 mgd and 14.8 mgd, respectively,
which exceed the recommended maximum pumpage limit of the
Aymamon limestone of 6 mgd, established by USGS. However, the
potential for salt water intrusion under Alternatives 3 and 4
would be substantially reduced by recharging treated groundwater
back-into the aquifer. There is less potential for salt water
encroachment under Alternative 3 than under Alternative 4
because the net loss of groundwater through evapotranspiration
is lower for Alternative 3 since less water is recirculated.
2. Compliance with ARARs
Section 121(d) of CERCLA requires that remedial actions comply
with all applicable or relevant and appropriate Federal and
State requirements for the hazardous substances, pollutants or
contaminants that are present on-site, as well as any action-
specific requirements (e.g., design, construction, etc.) and
locational requirements.
The air-^stripping systems proposed under Alternatives 2, 3, and
4 are equally capable of meeting Federal and State requirements
for air emissions. These systems are also equally capable of
treating extracted groundwater to levels no greater than the
MCL of 5 ppb, before the treated water is either recharged to
the aquifer or discharged from the Garrochales #3 well to the
PRASA public water supply system.
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EPA cannot determine whether complete aquifer restoration
(meeting MCLs) in this type of geological setting within a
reasonable period of time is possible using the technology of
groundwater extraction. Therefore, EPA cannot predict whether
the groundwater extraction well systems proposed under Alternatives
3 and 4 would attain the MCL of 5 ppb for CCl^ and thereby
restore the aquifer within a reasonable period of time.
Nevertheless/ complete aquifer restoration is the long-term
objective. Alternatives 1 through 4 will be comparatively
evaluated in this section for their potential to meet the ARAR,
the MCL of 5 ppb for CC14 throughout the aquifer, within a
reasonable period of time.
Alternative 1 relies totally on natural aquifer flushing and
dilution to reduce CC14 contaminant levels in the aquifer to
the MCL of 5 ppb. EPA does not believe that natural aquifer
flushing will restore the aquifer within a reasonable amount
of time. Since pumping well UE-1 has little impact dn contaminant
removal and control of migration, Alternative j.2 relies very
heavily on natural aquifer flushing and dilutilon to reduce
contaminant levels to the MCL of 5 ppb. Alternatives 1 and 2
are not expected to be capable of reducing CC14 contaminant
levels in the aquifer to the MCL of 5 ppb within a reasonable
period of time.
Alternative 3 proposes two additional extraction wells, which
would be capable of reducing contaminant levels and controlling
migration 'of the most heavily contaminated portions of the
aquifer, while allowing some contaminant migration. Alternative
3 relies partially on natural aquifer flushing and partially on
pumpage of two extraction wells to reduce contaminant concentration
levels in the aquifer to levels meeting the MCL of 5 ppb, and
is therefore more capable than Alternatives 1 and 2 of restoring
the aquifer within a reasonable period of time.
Alternative 4 proposes a network of seven new extraction wells
which would be capable of reducing contaminant levels and
controlling migration of the bulk of the residual contamination.
Alternative 4 relies mostly on the extraction wells to reduce
contaminant concentration levels in the aquifer to the MCL of 5
ppb, and is therefore the most capable of all four alternatives
to restore the aquifer within a reasonable period of time.
While it is unclear whether the goal of total aquifer restoration
within a reasonable period of time is an attainable one-,
Alternatives 3 and 4 would at least be capable of attaining the
MCL of 5 ppb for GC14 in portions of the aquifer.
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3. Long-term Effectiveness and Permanence
Long-term effectiveness and permanence addresses the long-term
protection and reliability of an alternative. Permanence is a
relative term and is therefore expressed in the degree of
permanence associated with an alternative with respect to other
alternatives being evaluated.
Long-term groundwater monitoring would be implemented for each
alternative to measure effectiveness and to identify potential
receptors.
Alternatives 2, 3 and 4 all provide for long-term protection of
the Garrochales #3 public supply well which minimizes risk
associated with consumption of contaminated groundwater by
wellhead treatment.
Since Alternatives 1 and 2 provide for only minimal, if any,
containment of contaminants in the groundwater near the source,
downgradient private wells currently used for watering livestock
and irrigation purposes are at a substantial risk of becoming
contaminated. Alternatives 3 and 4 are capable of removing
more contaminants from the aquifer, and at a faster rate than
Alternatives 1 and 2, which rely mostly on dilution and natural
aquifer flushing. Therefore, Alternatives 3 and 4 would be
more effective at restoring the aquifer and minimizing risk to
downgradient private wells.
Alternatives 3 and 4 are much more effective than Alternatives
1 and 2 in terms of the capacity to treat contaminants in the
aquifer°to concentrations equal to or less than the MCL due to
the number of extraction wells and the quantity of water treated
and reinjected.
Since pumping well UE-1 has little impact on contaminant migration,
it is assumed that CCl^ would migrate from the UMC site to Cano
Tiburones in approximately the same time period under Alternative
2 as it would under Alternative 1. Aquifer restoration under
Alternatives 1 and 2 would rely almost totally on natural
aquifer flushing.
Although PRDNR currently controls new well installations through
its permitting requirements, maintaining these institutional
controls for the duration of the aquifer restoration period
would be more difficult under Alternatives 1 and 2 than under
Alternatives 3 and 4. A greater amount of time is required to
cleanse the aquifer through natural aquifer flushing than with
the aid of extraction wells. Because of this, future users of
the aquifer would be at risk of consumimg higher levels of CC14-
contaminated groundwater under Alternatives 1 and 2 than they
would consume under Alternatives 3 and 4.
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While Alternatives 3 and 4 may not be able to attain the MCL of
5 ppb everywhere in the aquifer, these alternatives may provide
for attainment of the MCL in some portions of the aquifer/ and
at the very least, would lessen the potential cancer risk to
future users of the aquifer by reducing contaminant levels to a
greater extent than they would be reduced by natural flushing.
Alternative 4 would be capable of removing the most contaminants
from the aquifer, providing the most control of migration of
contaminants, and restoring the aquifer in the shortest period
of time, in comparison to Alternatives 1, 2, and 3 and would
therefore be the most capable of all the alternatives to meet
the MCL in the aquifer.
4. Reduction of Toxicity, Mobility or Volume of Hazardous
Substances
This evaluation criterion relates to the performance of a
remedial alternative in terms of eliminating or controlling
risks associated with the toxicity, mobility or volume of a
hazardous substance.
Alternatives 3 and 4 reduce the level of toxicity, volume and
mobility of contaminants to a much greater extent than Alternatives
1 and 2. Under Alternative 1, contaminants possibly remaining
in the unsaturated zone in the immediate area of well UE-1
would continue to slowly percolate into the water table; contam-
inants already in the groundwater, yet located outside of the
effective pumping radius of well UE-1, would continue to migrate
downgradient; and contaminants currently being removed by well
UE-1 would also be entrained in the groundwater. As such, the
total contaminant volume and mobility would increase by an
incremental amount. The t.oxicity level of CC14 would remain
unaffected. Alternative 2 slightly reduces the level of toxicity,
mobility, and volume of CC14 contamination through pumpage and
treatment at the UE-1 extraction well.
Under Alternatives 3 and 4, the mobility and volume of CC14 in
the groundwater are reduced by pumping and treating at the
existing wells and proposed extraction wells. The level of
toxicity is reduced through treatment. Reducing the level of
toxicity in the aquifer will reduce the cancer risk posed to
future unauthorized users of the aquifer, should institutional
controls fail.
Alternative 4 is capable of providing for the most reduction of
toxicity, mobility and volume of contaminants and would remove
contaminants from the aquifer the fastest, in comparison to
Alternatives 1, 2 and 3.
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5. Short-term Effectiveness
The short-term effectiveness criterion measures how well an
alternative is expected to perform, the time to achieve performance,
and the potential adverse impacts of its implementation.
The time required to meet the MCL of 5 ppb in the aquifer
cannot be determined for any of the alternatives due to the
fact that the soil beneath the site may represent a persistent
secondary source, and also because the persistence of CC14 in
this type of geological environment is not fully known. However,
the time required to meet the MCL would be substantially longer
under Alternatives 1 and 2 than under Alternatives 3 and 4,
which, in addition to natural aquifer flushing, rely on ground-
water extraction wells to actively remove contaminants from the
aquifer.
Alternatives 2, 3 and ,4 compa're equally in the time needed to
provide protection 'to. Lsers of the Garrochales #3 well. All
three alternatives propose connection of the well to an air-
stripping treatment unit.
Implementation of Alternatives 1 and 2 would have very minor
short-term impacts to workers and to the environment since
little construction would be involved.
Implementation of Alternatives 3 and 4 could pose some risk to
workers. Due to the possible release of contaminant vapors
during drilling and installation of the wells, workers may be
required to use Level C protection. Since the projected work
areas are remote from residences or industrial facilities, it
is not expected that any contaminant release during construction •
would affect the general populace. The operation of the ground-
water extraction wells would also not be expected to result in
an uncontrolled contaminant release.
Under Alternatives 3 and 4, the proposed well locations are
somewhat removed from existing roads. This would require land
to be cleared and grubbed,'and road construction.
Because Alternative 4'involves more construction than Alternative
3, the short-term adverse impacts of Alternative 4 to the
environment would be greater.
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6. Implementability
Implementability addresses how easy or difficult, feasible or
infeasible, it would be to carry out a given alternative. This
covers implementation from design through construction and
operation and maintenance.
Alternatives 1 and 2 would be relatively easy to implement in
comparison to Alternatives 3 and 4. Alternative 1, being the
easiest to implement, involves removing well UE-1 from service
which would take approximately four months. Operation and
maintenance, as well as operator experience, would be minimal.
Alternative 2 would be relatively easy to implement since it
only requires upgrading the existing air-stripping treatment
unit on well UE-1 and the installation of an air-stripping
treatment unit on the Garrochales #3 well, which would take
approximately two years. The long-term use of the existing
wells and new treatment units would have greater operation and
maintenance requirements than would Alternative 1.
T
Alternatives 1 and 2 would rely on PRDNR more heavily than
Alternatives 3 and 4 to maintain control and prevent future
well installations in the aquifer for drinking water purposes
until complete remediation is achieved.
Alternatives 3 and 4 would be relatively difficult to implement
Both alternatives would have substantially greater operation
and maintenance requirements than Alternatives 1 and 2, and
would require trained personnel to monitor system behavior and
perform routine maintenance.
The proposed extraction well locations in Alternatives 3 and 4
are somewhat removed from existing roads. Additional labor
would be required for land clearing and grubbing and road
construction. In addition, these alternatives require an
extension of electrical utilities.
Moderate to significant institutional constraints would be
imposed during the implementation of Alternatives 3 and 4.
The installation of water wells would require the services of a
drilling subcontractor meeting the licensing requirements of
the PRDNR. In addition, permits may be required by PRDNR for
chloride monitoring wells proposed under Alternatives 3 and 4,
and for recharge wells proposed under Alternative 4, subject to
the applicability of Section 121(e)(l) of CERCLA.
Alternative 4 would be the most difficult to implement in
comparison to Alternatives 1, 2 and 3, due to the greater
number of extaction wells and recharge wells proposed.
I
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The .degree of technical implementability would be the same for
Alternatives 2, 3 and 4 because the same technologies (ground-
water extraction with treatment and recharge to the aquifer)
are proposed under each alternative. The equipment and resources
under Alternatives 2, 3 and 4 are readily available. Additional
extraction wells proposed under Alternatives 3 and 4 would be
constructed by the cable tool or dual tube reverse air rotary
drilling method, both of which are widely used to construct
production wells in this type of limestone.
7. Cost
The cost evaluation of each alternative is based on the capital
cost (cost to construct), long-term monitoring, operation and
maintenance (O&M), and present worth costs.
Table 3, below, presents the estimates of capital costs, long-term
groundwater monitoring costs, O&M costs, and net present worth
costs.
TABLE 3 - COST ESTIMATES
ALTER-
NATIVE
Capital
Costs
($1,000)
Long-Term
Groundwater
Monitoring
($1,000)
Annual
O&M
($1,000)
O&M *
30-year
Present Worth
($1,000)
Net Present
Worth Cost
($1,000)
1
2
3
4 '
35
946
2,205
6, 199
440
440
440
440
151
368
691
1, 722
4,186
7,882
•
475
3, 108
6,831
14,521
* For costing purposes, O&M was projected to continue for 30 years.
8. State Acceptance
This evaluation criterion addresses the concern and degree of
support that the state government has expressed regarding the
remedial alternatives being evaluated.
The Commonwealth of Puerto Rico believes that Alternative 3, as
modified in the EPA's Proposed Remedial Action Plan, is the most
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environmentally sound and cost-effective alternative. The
Commonwealth is most interested in restoring the aquifer to the
maximum extent practicable. A concurrence letter from PREQB (see
Attachment 1) is attached to this Record of Decision.
9. Community Acceptance
This evaluation criterion addresses the degree to which members
of the local community might support the remedial alternatives
being evaluated.
The community expressed opposition to Alternatives 1 and 2, with
the exception of UMC, which favored a modified version of
Alternative 2 with the replacement of water supplies wherever
needed. Alternative 2 would protect the Gar'rochales #3 well,
but would allow contaminants to migrate towards Cano Tiburones.
Alternative 1 would neither protect the Garrochales |3 well nor
prevent contaminant migration into Cano Tiburones.
The community is in favor of a timely restoration of the aquifer to
the maximum extent practicable.
THE SELECTED REMEDY
The overall goal of the cleanup action at the UMC site is to
restore the groundwater to its beneficial uses (or health based
levels) within a reasonable period of time. However, the EPA
is currently unable to select a restoration remedy that it can
say with confidence will achieve this goal, because of the
unavailability of sufficient information to determine how long
it will take to restore the aquifer.
Therefore, the EPA is selecting an interim remedy. The
purpose of this interim remedy is to:
0 re.duce contaminant concentrations and maximize
removal of contaminant mass, and •
o
determine the feasibility of restoring all or
portions of the aquifer to health-based levels.
This interim remedy, which is a modified version of Alternative
3, will include the following components:
0 Continued pumpage of groundwater extraction well
UE-1 at 840 gpm with treatment of the groundwater to
levels no greater than 5 ppb of CCL4 by an upgraded
air-stripping system and discharge to an existing
sinkhole located northwest of the UMC facility.
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0 Pumpage of the AH Robins well at 450 gpm plus the
installation and pumpage of two new extraction wells
each at 800 gpm, with treatment of the groundwa'ter to
levels no greater than 5 ppb of CC14 by the UE-1 air-
stripping system and discharge to the existing sinkhole.
Continued pumpage of the Garrochales #3 public supply
.well at 2000 gpm with treatment of the groundwater to
levels no greater than 5 ppb of CC14 by air-stripping
and subsequent distribution to the public water supply
system. During remedial design, an evaluation will be
made of replacing treated water from the Garrochales #3
well with an alternate water supply from the artesian
aquifer. Since the pumpage of the Garrochales #3 well
is not an intregal part of the remedial scheme, this
well may be taken out of service if an artesian well
is installed.
0 If the two new extraction wells prove to be effective
at removing contaminants from the aquifer, additional
extraction wells will be added in a phased approach
with treatment by air stripping and recharge to the
groundwater. It is estimated that two to four additional
wells will be installed and pumped at approximately
800 gpm.
0 Installation of chloride monitoring wells near the
coastline to monitor potential salt-water encroachment.
0 Long-term monitoring of groundwater to track contaminant
movement and assess performance of groundwater extraction
wells.
In analyzing potential remedies for -the site, EPA favored
Alternatives 3 and 4 as being more protective of human health
and the environment than Alternatives 1 and 2. Evaluation of
Alternatives 3 and 4 according to the nine criteria, with emphasis
placed on the complex hydrogeological conditions present at the
site, lead EPA to select a modified version of Alternative 3 as
an interim cleanup remedy for the site.
Alternative 4, with its network of seven extraction wells, is
capable of removing the most contaminants, providing for the
most control of contaminant migration, and restoring the aquifer
the fastest, thereby providing the most protection of human
health and the environment of Alternatives 1 through 4.. However,
due to the complex hydrogeology underlying the site, uncertainties
exist regarding the effectiveness of groundwater extraction
wells at removing contaminants from the aquifer. Given the
costliness of Alternative 4, which is approximately twice the
cost of Alternative 3, it is uncertain whether the actual level
of contaminant removal would be gkeat enough to justify the
cost of the alternative. Therefore, EPA cannot determine that
Alternative 4 would be a cost-effective alternative.
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On the other hand/ Alternative 3, which proposes two extraction
wells, is capable of reducing contaminant concentration levels
in the most heavily contaminated portions of the aquifer,
providing for partial control of contaminant migration, and
restoring the aquifer faster than Alternative 1 and 2 which
rely almost exclusively on natural flushing and dilution.
Also, the cost of Alternative 3 is moderate in relation to
Alternative 4. However, Alternative 3 would allow a large
portion of contaminants, with CC14 concentration levels at
least as high as 170 ppb, to migrate towards Cano Tiburones.
This alternative is only capable of intercepting approximately. -
thirty percent of the total flow across the contaminant zone.
At this time, EPA believes that the optimal groundwater extraction
system for the site consists of a system which is somewhat
between Alternatives 3 and 4. EPA, however, cannot determine
the optimal number of wells nor predict their effectiveness
without first operating the wells. EPA is thereby selecting a
modified version of Alternative 3, which includes the installation
of additional extraction wells if the two new extraction wells
initially installed prove to have an effectiveness, in terms of
their removal of contaminants, which is commensurate with the
costs of installing, operating and maintaining the wells.
The exact number of additional extraction wells that would be
installed if the two new extraction wells installed initially prove
to be effective, the pumping rates of these wells, and the
exact location of the wells cannot be determined at this time.
However, it can be estimated that approximately two to four
additional wells may be installed that would pump at approximately
800 gpm each.
EPA believes that the modified Alternative 3 is cost-effective
in that extraction wells would be added sequentially, up to a
total of approximately four additional wells, aside from the
initial two, provided that the wells were shown to be effective
or have a high probability of success at removing contaminants
from the aquifer. Construction and implementation of the
initial groundwater remediation system (upgrading the UE-1 air
stripper, installing an air stripper to the Garrochales #3 well
and installing two new extraction wells and chloride monitoring
wells) is similar in scope to Alternative 3 of the FS. If four
additional extraction wells were installed, the expanded remedy
would entail a remedy similar in scope to Alternative 4.
Therefore, the Selected Interim Remedy is estimated to cost:
Capital Annual
Cost ($K) o&M ($K)
Initial System , $2,200 $400
I
Expanded System $6,200 $700
(Plus Initial System)
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The effectiveness of the two initial new extraction wells .will
be assessed based on the CC14 concentrations detected in the
extraction wells and in existing and future monitoring wells.
Additional extraction wells will be added based upon the
effectiveness of the two extraction wells initially installed.
Extracted groundwater from the additional wells will be treated
by air stripping by either the upgraded treatment unit proposed
for well UE-1, or by the new treatment unit proposed for the
Garrochales #3 well. These treatment units will be modified,
if needed, to handle any additional flow exceeding the capacities
of the units. Treated effluent will be discharged into the
aquifer, either through the existing sinkhole or through deep
recharge wells.
Each extraction well, including UE-1 and AH Robins, with the
exception of Garrochales #3, will operate until CC14 levels
have stabilized and are not being reduced. Once this is achieved,
pumping will be discontinued at the well and the well will be
monitored for a period of time. The contaminant concentration
levels are expected to rise within these wells after a period
of nonpumping, or resting, at which time pumping of the well
will be resumed. This cycle of pumping and resting will continue
for each extraction well until it is determined that contaminant
levels in the extraction wells are-not rising above the MCL of
5 ppb after successive resting periods. However, since it is not
known whether contaminant levels in the aquifer can be reduced to
the MCL, EPA will reevaluate this remedy within five years of
operation (should the contaminant levels in the aquifer not meet
the MCL within this time period) to determine the allowable
contaminant levels that the extraction wells must meet before
being shut down.
As stated above, operation of the extraction wells will continue
for approximately 5 years at which time a full remedy evaluation
will be conducted. 'The purpose of this evaluation would be to
determine the practicability and cost-effectiveness of cleaning
up all or part of the aquifer and to specify the type of further
action to be taken. ' If a decision is made that any portion of
the aquifer will not be restored, then a waiver from the MCL
for reasons of technical impracticability will be evaluated at
that time.
It is expected that some CC14 has remained adsorbed to the
organic carbon in the unsaturated zone and will remain a •
secondary source of contamination to the groundwater as the
|>ure CC14 solubilizes in the water between the soil particles
Pver time. The amount and location of residual CC14 which
presently exists in the unsaturated zone is unknown. The
possible residual contamination of the unsaturated zone and its
likelihood as a source will be addressed separately by EPA's
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RCRA program, which may require further investigation and response.
Therefore, the scope of the Selected Interim Remedy will not
address possible contamination of the unsaturated zone.
THE STATUTORY DETERMINATIONS
Protection of Human Health and the Environment
Drinking water in the Barceloneta area is currently provided by
the PRASA public supply system. Impacted and threatened water
supply wells were shut down shortly after the discovery of the
spill in 1982. According to USGS, no private domestic wells
within the zone of contamination are currently being used for
drinking purposes. However, private wells currently .utilize site
groundwater for watering livestock and irrigation.
The only well at the site currently being used for potable water
is the Garrochales 13 public water supply well. Historic as well
as recent sampling of this well indicates the presence of CC14 at
levels less than the MCL of 5 ppb. There is the possibility,
however, that CC14 levels exceeding 5 ppb will appear at the
Garrochales #3 well in the future.
The Selected Interim Remedy will prevent potential risk of ingestion1
of contaminated groundwater with wellhead treatment at the
Garrochales 13 well. This well will be treated, as a precautionary
measure, to levels no greater than the MCL of 5 ppb before the
water is distributed through the PRASA public water supply system.
The proposed groundwater extraction wells are capable of removing
contaminant mass from the aquifer, thereby reducing contaminant
concentration levels, and will provide for at least partial
control of contaminant migration. The first two extraction wells
to be installed are capable of controlling and reducing contaminant
levels of the most heavily contaminated portion of the aquifer.
Contaminants not controlled by the propos.ed extraction wells
(either the initial two or the additional wells) will migrate
towards Cano Tiburones. However, dilution is expected to reduce
contaminant concentrations to low levels by the time that the
contaminants reach their discharge point from the aquifer.
The Selected Interim Remedy will provide for protection of
human health and the environment through its capability to
remove contaminant mass and reduce contaminant concentration
levels within the aquifer. A reduction of CC14 contaminant
concentration levels will result in the following measures protective
of human health and the environment:
0 reduction of cancer risk levels which will decrease the
reliance on institutional controls over future potable well
installations in the aquifer,
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0 protection of presently unimpacted portions of the aquifer
contaminant levels less than the MCL of 5 ppb ) ,
0 prevention of further contamination of presently impacted
portions of the aquifer,
0 a possible attainment of the MCL of 5 ppb for CC14 in large
portions of the existing impacted areas, and
0 reduction of risk to Cano Tiburones and the life it supports.
The Selected Interim Remedy is not expected to cause any adverse
short-term or cross-media impacts.
Attainment of ARARs
Table 4 lists both Federal and State potential ARARs as. well as
criteria, guidances and advisories which were considered for
groundwater cleanup.
MCLs, established pursuant to the Safe Drinking Water Act, are
legally enforceable standards for drinking water. EPA considers
the MCL for CC14 of 5 ppb to be a relevant and appropriate require-
ment with respect to the groundwater at the site and an applicable
requirement at the tap.
Water to be distributed to the PRASA public supply system must
meet the MCL of 5 ppb for CCl,^. Water to be recharged into the
aquifer either through recharge wells' or natural sinkholes should
also contain CC14 levels no greater than the MCL of 5 ppb.
An additional ARAR to be met is Air Emission Standards, regulated
under the Clean Air Act. Air-stripping volatiles from the
extracted groundwater requires controls pursuant to Rule 419 of
the Regulation for Control of Atmospheric Pollution, established
by PREQB. This rule limits the rate of discharge of volatile
organic contaminants (VOCs) into the atmosphere to 3 pounds per
hour or 15 pounds per day (based on mass balance) whichever is
less. Off-gas treatment will be required for the air-stripping
systems operated under the Selected Interim Remedy if VOC concen-
trations exceed these limits.
Groundwater leaving the proposed air-stripping systems will
meet the MCL of 5 ppb of CC14 before being recharged back
into the aquifer and before being distributed through the
PRASA public water supply system. Air emissions from the
treatment units are not expected to exceed PREQB limits.
However, if they should, off-gas treatment will be implemented.
t
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Due to the unknowns associated with the underlying geology which
may limit the effectiveness of groundwater contaminant recovery
extraction wells, and due to the possibility of a persistent source
of contaminants existing in the unsaturated zone, EPA cannot deter-
mine at this time whether the Selected Interim Remedy will attain
the ARAR, the MCL of 5 ppb for CC14, in the aquifer within a reason-
able period of time. The Selected Interim Remedy may be able to
attain the MCL in portions of the aquifer. However, because of
this uncertainty, the Selected Interim Remedy will be reevaluated
within a five-year operational period.
The Selected Interim Remedy is expected to remove contaminant mass
from the aquifer and partially control contaminant migration. The
Selected Interim Remedy is capable of restoring the aquifer to a
larger extent and in a shorter time period than if the aquifer were
allowed to flush by natural means.
Cost-E f_f_e c t^yeness
EPA believes that the Selected Interim Remedy provides overall
effectiveness proportionate to its costs. The Selected Interim
Remedy will be designed to maximize the removal of contaminant mass
from the aquifer. VVhether the Selected Interim Remedy can completely
or partially restore the aquifer within a reasonable period of time
cannot be determined at this time. However, EPA believes the
benefits in terms of protection of human health and the environment
which can be attained strictly through contaminant mass removal are
worth the costs involved.
Utilization of Permanent Solutions and Alternat ive Treatment
Technologies or^ 'Resource Recovery^echnorqgTes 'to the Maximum
Extent Pra ct icable
For the reasons specified in the Selected Remedy section, the
modified version of Alternative 3, as an interim remedy, represents
the best balance of the nine criteria and is determined to be the
most appropriate remedy for the site at this time. The Selected
Interim Remedy utilizes permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable.
Preference for Treatment a.s a _Pri^ncip_a 1JE1 ement
The Selected Interim Remedy satisfies the statutory preference for
remedies employing treatment that permanently and significantly
reduces the toxicity, mobility or volume of hazardous substances.
The Selected Remedy includes the installation and operation of
groundwater extraction wells for contaminant recovery. Contaminated
groundwater pumped from the extraction well's will be treated with
air-stripping units before being recharged into the aquifer and
before being distributed through the PRASA public water supply
system. This pumping and treatment of the groundwater is expected
to permanently and significantly reduce the toxicity, mobility and
volume of the hazardous substances in the groundwater at the site.
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Atlantic Ocean
Upjohn Manufacturing
"^- ' Companyjg^gjL"
^fjj) Jarred a / /
.\l:'r.T«**»rt|7»
»nvironm«nt»l eng,n«*rs. scientists.
pltnntrs A mintgament consu/ltnn
Figure 1
Location Plan
Upjohn Manufacturing Company
Barceloneta, Puerto Rico
-------
* A R R C(C HALES
CAMBALACHE STATE
FOREST
71 bur on ts
L. *—°-
LOCATION PLAN
FIGURE 2
-------
Upjohn Manufacturing Company
N
Adapted From: Torres, USGS, 1984
600
400
200
m
m;
Sea H
Level o
2
-200 2
m
-400
0 MILES
10
76543
DISTANCE FROM SHORE LINE
-r-
2
0 KILOMETERS
SOURCE: Modified From Geolec, 1984
pl»nnett A m»n»g»m^nt consultants
Figure 3
Generalized Ground Water Movement Across North-South Cross-Section
Through Upjohn Manufacturing Company
Upjohn Manufacturing Company
BarceJ^fca, Puerto Rico
-------
1200 -
Upjohn
Manufacturing
Company
uj
-300 -
1200
900
600
-300
i* iv
i;
LEGL'ND;
t-':':'i-':':X;i Quaternary Deposits
| | Camuy Formation
ID Aymanion Limestone
Aguada Limestone
Montebello Member
Cibao Formation
Cibao Formation
T *n 1 r
10 ') a ;
Distance From Shore Line
Lares Limestone
San Sebastian Formation And Volcanics
Contact
Water Table
Potcntiomctrlc Sufacc On Cibao Formation
And Lares Limestone
Kilometers
SOURCE: Modified From Ceotec, 1984
environmental trginetit. jcmnfrjls.
planners A management consultants
Figure 4
Geologic Sequence
Upjohn Manufacturing Company
Darceloneta. Puerto Rico
-------
SCALE 1:213
FA-123C
FA-123B
FA-120B
FA-110
FA-109
FA-120
FA-125
FA-122
FA-108
FA-123
FA-137
FA-136
FA-135
AVE-13
Failed Tank
SOURCE: Modified From Geotec. 1984
9fivironm»nt»l *ngm*»r3. scientists.
m»n»y»m«nt consulttnn
Figure 5
Vacuum Well Locations Within Tank Farm
Upjohn Manufacturing Company
Barceloneta, Puerto Rico
-------
\
6 A R R 0
C H A L E S
J
> ;
MW23
PCWSKUNf
MW2I
iMW20
MWI93
MWI6
MW22« /
A.H.
MW7'
MW
Me
17
MWI1
MW5«
MW60 I MWI2<
•MW3
.^
MW
m
MW01
,MWI5
FIGURE 6
KILOMETERS
-------
• /.
Contour
Contour Intervals Are In Concentrations Of
1000 0 1000 2000 >"•".;"•' ^ %JYV"':<
scale feet
SOURCE: USGS 1:20.000
•"•i;/.Barceloneta, Puerto Rico. Quadrangle 1982
^ ^-~s* t ,
»nvironm»ntat engin&trs. scientists.
planners & manag«rr>«nt consultants
Figure 7
Interpreted Limit Of CC^ Contamination, 1987
Upjohn Manufacturing Compajiy
Barceloneta. Puerto Rico
-------
ATLANTIC OCEAN
^^^^KM^^^T-^^
*^-#$&£-.:.' "^fe^D ^i>-
•=•'• •-?•.,•-••-.$#- . --- v- • \-r /'tf^^SF^u*-
- •• ; >' " "V. .~~;.. ."-" x-- # ••' ' • •'?rC . • —' ... '"5wa-«s~i.!...Wj "-J>~%5?T •• /-^s^T^f •>; •
^^^^cr^~^^^^S^^^^:^
\ if^ • ' ? ;••'"'. ^"^^—^~~*~ >'; ' ^''''^^'^r-^V*''
_^__—A/ ;-•• ^-^__ ;-_ • •\f/r^i\ / ):'? • '
:.ou^^^^;:^H ^-1—^•x,,l: ^-^' \1! :-:-f-:iJ,,-:-:
r.J\ ''••', ,' -Lj[r_
:'> tJ Ramon Rosa 3; ./~-
!-7^"i'i~-l:(?^ Upjohn Artesian —
^.fc: • , i ... • • •• •• •' ^.\^,.~ *-r»i«'"> v-iiivoiaii- . ^ ^t ^yMW—10 VXLH^-
r^Fl, •". l'^ Ufjoh." Man"facturlng Company•*^--.::».~-/.'"ir^^
^^-;NCl^ Barceloneta, Puerto Rico. Quadrangle 1962
Well Locatio
Upjohn Manufacturing
Barceloneta, Pu
-------
s.
ATLANTIC
*T^ri1hrfc^
;;;. /:Ijlil Nlli ifUK t -lr-
'
Represents CCU Concentrations
5 ppb In 1988 HT
[" ""] Interpreted Limit Of 5ppb
. J Concentration (1987)
Manufacturing Cpmpany\_
1000 0 1000 2000 ^^ffryx* '^fy*x^'ffi%.
scale feet j^".' Lx^.-j—^Xv.,-—•KX^a'rcVlb'neta'. "Puerto Rico, Quadrangle 1982
•ov»ronmenra' tngm«*rs. scientists
pitnn^n 4 mtn»gofr>ent consutlants
Figure 9
A Comparison Of The 1987 And 1988
Interpreted Limits Of CCI4 Contamination
Upjohn Manufacturing Company
Barceloneta. Puerto Rico
-------
>«s *•."—«
LEGEND:
Maximum 30,000 ppb
00(4 Concentration
(1983-1987)
Maximum 5,000 ppb
00(4 Concentration
(1983-1987)
. Maximum 1,000 ppb
CCI4 Concentration
(1983-1987)
__ mm Maximum 500 ppb
CCl4 Concentration
(1983-1987)
Interpreted Limits Of Residual
CCI4 Contamination
(Composited From 1983 To
Concentration)
Interpreted Limit Of 5 ppb
CCI4 Concentration
(1988)
Existing Well
MAP SOURCE: USGS 1:20,000;' J,
Barceioneta, Puerto Rico, Quadrangl
1000 01000 2000 y^ ;
J^TUJ'S"
...A/- -^ \__.| -' ' v'yg>^:f ••A__LJ_
,!/.-•' ; ;—/•• I's-'t'r^zS^^—
Upjohn Manufacturing Comp
scale
feet
environmental •ng/n»«rs. scmnnsts.
planners & m*ntg«
-------
ATLANTIC
O C E A N
^r^^\'\\ !/|| i j \iUusGs-3 ^^ : . -'' /; ;•; ^ i__^
^^^
•-.^:v *•' .-:; •^•"'iL-rl' -' -^••^'-r" \/_\xi.. .Ki :1 j | : j ,/i / \i.'• \ \\—]__
•.;••— i .-:',-_.'P^T1 : • ». .-1 «ainc.... i'.... •' '..-..I. : •: / •:••••• ; i
Existing Wells
No Access Wells
MAP SOURCE: USGS 1:20, OOO^!/
Barceloneta, Puerto Rico, Quad'rangle 1982
i '
1000 oiooo
scale
Marquez
Manufacturing Comftanyr-T>-'
',• :^, /-.-»*• -•: ... . ...... . . -, , ' < I"
-1 -' '•-. ^ U p j o h n ••;'"" -^l^' V^- r>;v^<-
& mtn»gom«nl consultants
Figure 11
Location Of Wells Within Zone Of Contamination
Upjohn Manufacturing Company
Barceloneta. Puerto Rico
-------
ATLANTIC OCEA N
r 7 j£ &~fei' "£"} '^/7'^^T-j'^-T^r' C' \ V££ £7" •£-'- ""•'^
A/^Y^^^S ^ \1 .<^-rV$*-' / /f~^f-
S-~^ >.--' y^1^/- ^i^ >L? ,\/ / |x^.,/.T'4 i v V-
// ^^^^>,A:^J. i X>/%^..L.L ..^••-
vCVi i Tjfi ,
:/i i/ !! i I i j I I .!;{La Cambjja^ . , /
..^^•--r^u-::"-.---,..--.-, --- V'^ ^_ —^'\^^^j^_^/^
— 1 " V . \ i: I ' ' i.. ' i :
;»;; «q^--.-.>c. ,"—J~~^.-'—^-^_
: i'"'".'-•." ../•>/ Wl-4
• I ' -..--• ..-V ../TT^t-.
,••*•! r—-'~ -»'7*suAVi',^.
Residual CCU Contamination
Existing Pumping Well
/vr"?! A'3 e
Upjohn Manufacturing Companyx
MAP SOURCE USGS 1:20,000' j:y
Barceloneta, Puerto Rico, Quadrangle 1982
1000 01000
scale feet
environmental engineers, scientists,
planners & management consultants
Figure 12 ^
Schematic Layout - Alternative 1
Upjohn Manufacturing Company
Barceloneta, Puerto Rico
-------
O C E A
,•;• V\ V«'
••->. rvx &•
-'i «•« •' /sv/V.Sjr C4\'l\vi i-'^i-WfV'-A.f\fA''C^ f >'/•'-1 '-v
^^MMM^^IP'^
.--. •;«!> ^,i*w via .iSs&yit-tit-.frr'^-r- •:^r/-s5£uyi'1^v.-f r-ro'• /fry^;
'..•f\i'-*jl
_ r*.//V?.\.ii
LEGEND:
Residual CCU Contamination
Existing Pumping Well
SOURCE USGS 1:20,000f "
Barceloneta, Puerto Rico, Quadrangle 1982
1000 0 1000 2000 .
'^Y^r\_y''j ^'-
scale feet JT7 I!^iJWjxC^\|^
^.*^»'>^-Upjohn Manufacturlng_CompanyV
Schematic Layout - Alternative! 2
Upjohn Manufacturing Company
Barceloneta, Puerto Rico
environmental angino^n.
planners & management consultants
-------
ATLANTIC OCEA N -v<4
_,! \ ' - > X- A °^Q4--^rfM.l2;
; : rM"*T
i^^r^-vrr
\.U.
s~»
I ( o
PuxU?
Pjlmiv MU^I
' •• I ! I 11 1 A -\ ' »
i [.-La CambiJaC
•.v."::r.v.V-"'"4J * "" ——-••*-= TA\
i r T '
.- ai
•rV'-'"': : ' ;
"•-'•'\ ,; ..i-.->^. i
11-"*--*s ' ""***•....«.-•-
I
i j _\r-^ ;
.''•:«•.?..-•• £^ ^! 's i1
•""—P..,.
jl!' i Ld^^—-x
-i-s— -,--f .^ -p-^j"
/•I
'/: :
C :- i:
4^nr
\(
LEGEND:
Residual CCI4 Contamination
^i£r
; Sinkhole'
S>»\*-Upjohn Manufacturing Company'
grtvironm«ntal 9ngtr>«+rs. scientists.
planners & managemtnt consulttnfs
Figure
Schematic Layout - Alternative
Upjohn Manufacturing Company
Barceloneta, Puerto Rico
-------
N
:/%
v :/ '•«.,
X :'
:-- -
Cambalache Forest
*^.-^KS ^^L/Vc.^^/rp'1. ^o^o-^ .-;V"T
> x«VX.t=~ii-i 3.^1 (/ rV/5c .S ~^r ^ / ( > ,-- 1 Ji
. -^z^^nS; WS?:; ?P
TdlfeJff^Ll^^*
' .-^•i^Vft/'^1' ^=; 'h^'^ \^^ ^.."' ->*v).
.:Cf- ^ff,^V\'v "A-ft''!1S\??rW:.5'\'!f'.'" \A •/&*!•
• ^i; ^^-^' \ -B «^j -' ^/y/- —' -S
? ^tC^^^ ^€%>: SP^r^^f
t^^fel^^f^^^f?:
.;•> - \ * '— ^^-rN^ A /^5\^ "i , "~
'•• '^^WXx.
'1 • ? - '-'
Upjohn Manufacturing Company
^•ii // ^r. "^.\ .^^ i u,-^
South Air Stripping System
LEGEND:
Residual CCI4 Contamination
IP Existing Pumping Wells
^ Proposed Extraction Wells
D Proposed Chloride Monitoring
Network
0 1000 '-H:i;
l.^r'v'
1000
.>^d ~ ->m-- li^V^MAP SOURCE: USGS 1:20,000
scale feet ^j .K^- x^ j^^ p.' ZTr^-.-Barceloneta, Puerto Rico, Quadrangle 1982
environmental cng/neers,
planners & management consultants
Figure 15
Proposed Layout For The Ground Water Treatment
Systems And Associated Piping-Alternative 3
Upjohn Manufacturing Company
Barceloneta, Puerto Rico
-------
• —: \ " - U • - < r"
? - T-&—:^ Tt^r-y^ -:
'i'r! ' ^\
irH
n?^
*^t^U^ &CJ£ V * II _aV vv.4 Contamination
Existing Pumping Wells
Proposed Extraction Wells
Proposed Zone Of
Recharge Wells
Proposed Zone Of
Extraction Wells (E-2 - E-7)
>AH Robins
: Sinkhole1
/.
Barceloneta,.Puerto Rico, Quadrangle 1982-]
'1000 01000 2000 '&'"
c~
scale feet
Manufacturing CompanyV
Figure 16
Schematic Layout - Alternative 4
Upjohn Manufacturing Company
Barceloneta Puerto Rico
-------
N
tr L3\
AH Robins
rSinkhole
UE-1 )/xfcl**
\ r \ . f / _ * -Li
Upjohn Manufacturing Company.":
South Air Strlppfng
O Existing Pumping Wells
• Proposed Extraction Wells
A Proposed Recharge Wells
D Proposed Chloride Monitoring
Networks
1000 0 1000 -^! 1) J
scale feet
MAP SOURCE: USGS 1:20,000
r^.-Barceloneta, Puerto Ric'o, Quadrangle 1982
onvfronmental engineers, scientists.
planners A management consultants
Figure 17
Proposed Layout For The Ground Water Treatment
Systems And Associated Piping-Alternative 4
Upjohn Manufacturing Company
Ba reel on eta, Puerto Rico
-------
•TABLE 1
GROUND WATER WELLS AND SPRING SAMPLED (1988)
Well No.
Sampled
Mtf-1
MW-9
HW-16
MW-18
MW-19
MW-20
MW-21
MW-22
MW-23
MW-101
MV-102
MW-103
Pollera #43
Job Corps #54
Garrochales 3, #54a
Vaqueria Martinez #47
#48
Morales #49
#50
#51
La Cambija #52
Rosa Delgado #53
PRASA Garrochales #135
Julio Reyes #179
Jossie Morales #301
Vaqueria Sabana #305
Specified
Sampling Depth
(below grade)
(320')
(310')
(320')
(320')
(400')
(345')
(280')
(290')
(235')
(235')
(235')
(280')
Concentration
Level
(ppb)
55
ND
140
160
2.9
ND
59
44
170
29
ND
2.4
4.7
0.7
1.4
ND
ND
ND
ND
ND
13.0
ND
ND
ND
ND
6.4
ND - CC14 was not detected using a minimum detection limit of Ippb.
(313/22)NY-SS
-------
TABLMF (CONT'D)
COMPOUNDS DETECTED IN THE GROUND WATER SAMPLES TAKEN IN THE VICINITY OF UHC, (JANUARY 1986) (1)
aa*s*snss=s3K=3c=»»s=3s=^3so=c=sn=n===3,T=s=c==sscs=======================s============
SAMPLE NO. TB-01 TB-02 TB-03 TB-04 TB-05 18-06 TB-07 TB-08 TB-09 TB-10 TB-11
ORGAN I CS:
acetone 10.0 U 10.0 U 10.0 U 30.0 55.0 30.0 U 30.0 U 25.0 U 10.0 U 10.0 U 36.0
1,1,1-trichloroethane 5.0 U 5.0 U 3.0 J 3.0 J 500.0 E* 330.0 * 540.0 * 310.0 D* 170.0 * 6.0 21.0
SBBSSS2SS35S8=£SSS&SC=BSSSa==ES=Z=========S=S£=£====z====5=z==============£S=s=£==z=== ==========3=2 S=»==S==============S====S====3==S===============
Notes:(1) All values are in ppb unless noted otherwise
U Indicates element was analyzed for but not detected. The number shown is the detection limit.
J Indicates an estimated value; result is less than the specified detection limit.
B Indicates the analyte was found in the blank. Indicates possible blank contamination.
E Estimated value or not reported due to the presence of interference.
* Exceeded State and/or Federal Guidelines or Criteria.
TB Trip Blank
-------
TABLE 1 (CONT'D)
COMPOUNDS DETECTED IN THE GROUND WATER SAMPLES TAKEN IN THE VICINITY OF UMC, (JANUARY 1988) (1)
SAMPLE NO. FB-01
ORGANICS:
acetone 990.0
2-butanone . 50.0 U
1,1,1-trichloroethane 25.0 U
benzene 25.0 U
toluene 25.0 U
INORGANICS:
aluminum 1380.0
antimony ' 22.0 U
barium 17.0 J
calcium 505.0 J
chromium 29.0
cobalt 5.1 J
copper 5.0 J
iron 1160.0 *
magnesium 4290.0 J
manganese 5.4 J
mercury 0.2 U
sodium 38.0 J
thallium 10.0 U
zinc 8.1 J
FB-02
10
10.
5
0 U
0 U
0 U
5.0 U
5.0 U
2.
68.
7.
5.
9.6 J
22.0 U
.0 U
.0 J
.0 U
.0 U
5.0 J
13.0 U
21.0 J
2.0 U
0.2 U
33.0 J
10.0 U
12.0 J
FB-03
62.0
10.0 U
2.0 J
5.0 U
5.0 U
19.0 J
22.0 U
2.0 U
27.0 J
7.0 U
6.1 J
5.0 J
14.0 J
58.0
2.0 U
0.2 U
26.0 J
10.0 U
6.2 J
FB-04
37.0
11.0
4.0 J
5.0 U
21.0
8.0 U
22.0 U
2.0 U
16.0 J
7.0 U
5.0 U
8.3 J
13.0 U
21.0 J
4.2 J
0.34
67.0 J
10.0 U
6.1 J
FB-05.
10000.0
10.0 U
370.0 E*
2.0 J*
5.0 U
8.0 U
22.0 U
.0 U
2
27.0
7
5
5
0 U
0 U
0 J
13.0 U
58.0 J
2.0 U
0.2 U
26.0 J
10.0 U
8.3 J
Notes:(1) Alt values are in ppb unless noted otherwise
U Indicates element was analyzed for but not detected. The number shown is the detection limit.
J Indicates an estimated value; result is less than the specified detection limit.
B Indicates the analyte was found in the blank. Indicates possible blank contamination.
* Exceeded State and\or Federal Guidelines or Criteria
E Estimated value or not reported due to the presence of interference.
FB-06
20.0 U
20.0 U
420.0 J*
10.0 U
10.0 U
21.0 U
15.0 U
2.0 U
66.0 J
5.0 U
4.0 U
4.0 U
8.0 U
11.0 J
4.1 J
0.2 U
55.0 J
10.0 J
2.0 U
FB-07
30.0 U
30.0 U
400.0 '
15.0 U
15.0 U
32.0 J
15.0 U
2.0 U
12.0 U
5.0 U
4.0 U
4.0 U
8.0 U
4.6 J
2.0 U
0.2 U
245000.0
10.0 J
2.0 U
========== ==3====== ===;s ============£==
FB-08
110.0.
10.0 U>
8.0
5.0 U
5.0 U
45.0 J
15.0 U
2.0 U
31.0 J
5.0 U
4.0 U
4.0 U
9.6 J
26.0 J
2.7
0.
38.0
10.0
J
.2 U
J
J
2.9 J
FB-09
250.0
10.0 U
6.0
5.0 U
5.0 U
21.0 U
37.0 J
2.0 U
12.0 U
5.
4.
4.0 U
8.0 J
6.3 J
.0 U
.0 U
2.0 U
0.2
55.0
10.0
2.0 U
-------
TABLE"1 (CONT'D)
CONFOUNDS DETECTED IN THE GROUND WATER SAMPLES TAKEN IN THE VICINITY OF UHC, (JANUARY 1968) (1)
*a«-s*iiii = s;»ccss = Cj;s = s = B = = = = = c = = = = = = s = ssss = = = s-----S--3-- = = = nC5S = = S = = =1= = = S = = = S==SE = S3SS = = = = = = = = = = = =
WELL NO. DW-48 DW-49 AW- 50 AU-51 SU-52
ORGAN ICS:
2-butanone 9.0 J 10.0 U 10.0 U 10.0 U
carbon tetrachloride 0.2 U 0.2 U 0.2 U 0.2 U
toluene . 24.0 S.O U 5.0 U 5.0 U
INORGANICS:
aluninun 8.0 U 32.0 J 202.0 21.0 U
arsenic 10.0 U 10.0 U 35.0 205.0 *
barium 12.0 J 62.0 J 56.0 J 26.0 J
cadmiun 4.0 U 5.0 U 4.0 U 5.0 U
calcium 112000.0 83400.0 115000.0 75900.0
chromium 7.4 J 5.0 U 12.0 5.5 J
cobalt 5.0 U 4.0 U 5.0 U 4.0 U
copper 5.0 J 4.0 U 14.0 J 4.0 U
iron 60.0 J 99.0 J 1450.0 * 198.0 J
lead 5.0 U 5.0 U 5.0 U 6.8
magnesium 23000.0 15400.0 15700.0 7120.0
manganese 8.3 F 6.3 F 117.0 * 2.5 J
mercury 1.2 0.2 U 0.2 U 0.2 U
potassium 8050.0 2710.0 J 2560.0 J 1220.0 J
selenium 5.0 U 5.0 U 5.0 U 37.0 *
sodium 185000.0 53000.0 74300.0 35900.0
thallium 100.0 U 10.0 J 100.0 U 10.0 J
vanadium 11.0 J 3.0 U 11. OJ 3.6 J
line 25.0 111.0 75.0 440.0
Notes: (1) All values are in ppb unless noted otherwise.
U Indicates element was analyzed for but not detected. The number -shown
10.0 U
13.0 *
5.0 U
21.0 U
10.0 U
15.0 J
5.0 U
142000.0
6.2 J
4.0 U
80.0 U
14.0 J
6.9 F
134000.0
7.3 F
0.2 U
43400.0
5.0 U
2580000.0
10.0 J
3.0 U
12.0 J
is the detection
IW-53
10.0 U
0.2 U
5.0 U
21.0 J
10.0 U
19.0 J
4.0 U
111000.0
7.0 U
5.0 U
5.0 J
229.0
5.0 U
15700.0
10.0 J
0.2 U
5130.0
5.0 U
143000.0
100.0 U
8.3 J
10.0 J
limit.
DW-135 LS-179
10.0 U
0.2 U
5.0 U
21.0 U
10.0 U
20.0 J
5.0 U
88900.0
5.0 U
. 4.0 U
4.0 U
18.0 J
5.0 U
6290.0
5.9 J
0.2 U
1330.0 J
5.0 U
29400.0
10.0 J
3.0-J
196.0
10.0 U
5.0 U
5.0 U
578.0
10.0 U
78.0 J
4.0 U
142000.0
7.0 U
5.0 U
26.0
2260.0 *
5.0 U
18300.0
19.0 U
0.2
2460.0 J
5.0 U
89400.0
50.0 U
8.3 J
9.5 F
AW-301 LS-305
10.0 U
0.2 U
• 5.0 U
307.0
10.0 U
74.0 J
7.4 *
61500.0
14.0
13.0 J
11.0 J
3880.0 *
28.0 J*
27100.0
623.0 *
0.2 U
15600.0
5.0 U
88000.0
100.0 U
4.0 U
4200.0
10.0 U
6.4
5.0 U
8.0 U
10.0 U
21.0 J
4.0 U
93600.0
7.0 U
5.0 U
5.0 J
14.0 J
5.0 U
16300.0
39.0
0.29
5170.0
5.0 U
74700.0
100.0 U
4.0 U
53.0
J Indicates an estimated value; result is less than the s pec \ fed detection limit.
B Indicates .the analyte was found in the blank. Indicates possible blank
F Failed quality control review per EPA
* Exceeds State or Federal Guidelines and/or Criteria.
DU Domestic Well
AU Abandoned Well i
SW Surface Water
IW Irrigation Well
LS Livestock Well
contamination.
-------
TABLE 1 (CONT'D)
COMPOUNDS DETECTED IN THE GROUND WATER SAMPLES TAKEN IN THE VICINITY OF UHC (JANUARY 1988) (1)
WELL NO. MW-23 HW-101 MW-102 MW-102 DUP. HW-103
ORGANICS:
acetone
chloroform
carbon tetrachloride .
INORGANICS:
aluminum
antimony
barium
cadmium
calcium
chromium
cobalt
copper
iron
lead
magnesium
manganese
nickel
potassium
sodium
vanadium
zinc
niccAi ucn MCTAI c.
l/lddULVCU PICIHL9.
aluminum
barium
calcium
chromium
cobalt
copper
iron
magnesium
manganese
nickel
potassium
sodium
zinc
833SKBSK8833S.C3S33S5S33ES
26.0
10.0
170.0 *
115.0 J
22.0 U
12.0 J
4.0 U
111000.0
7.0 U
5.0 U
5.0 J
182.0
5.0 U
33200.0
7.5 J
16.0 U
9100.0
326000.0
4.7 J
12.0 J
Notes:(1) All values are in ppb unless
37.0 F
4.0 J
29.0 •
85.0 J
22.0 U
19.0 J
4.0 U
108000.0
2980.0 *
19.0 J
56.0 J
25700.0 *
5.0 U
10600.0
70.0 *
814.0
3120.0 J
87700.0
30.0 J
32.0
8.0 U
2.0 U
99000.0
7.0 U
5.0 U
5.0 U
45.0 J
9330.0
3.5 J
68.0
3240.0 J
75000.0
6.7 F
noted otherwise
10.0
5.0
0.2
25.0
15.0
14.0
5.0
104000.0
1240.0
26.0
36.0
15600.0
5.0
11800.0
156.0
1350.0
4460.0
91400.0
5.8
9.4
8.0
2,0
86600.0
9.9
5.0
5.0
74.0
2850.0
25.0
421.0
1700.0
17300.0
U
U
U
J
U
J
U
*
J
F
U
*
J
J
J
U
U
J
U
U
J
J
U
6.0 U
U Indicates, element was analyzed for but not detected. The
J Indicates an estimated value;
result is less
B Indicates the analyte was found in the blank.
• Exceeded State
MW Monitoring Well
DW Domestic Well
IU Irrigation Well
and/ or Federal
nunber
than the specifiec
Indicates
Guidelines or Criteria.
10.0 U
5.0 U
0.2 U
132.0 J
15.0 U
15.0 J
5.0 U
104000.0
831.0 *
14.0 J
22.0 J
7790.0 F
5.0 U
11800.0
122.0 *
888.0
4640.0 J
91800.0
3.0 U
16.0 J
8.0 U
2.0 U
88300.0
7.0 U
5.0 U
5.0 U
34.0 J
2960.0 J
16.0
379.0
1700.0 U
18200.0
6.0 U
shown is the
10.0 U
5.0 U
2.4 *
243.0
22.0 U
20.0 J
4.0 U
78500.0
350.0 *
9.2 J
17.0 J
7440.0 *
5.0 U
2990.0 J
54.0 *
472.0
1700.0 U
8990.0
10.0 J
30.0
8.0 U
10.0 J
65300.0
7.0 U
5.0 U
5.0 U
97.0 J
2920.0 J
20.0
224.0
1700.0 U
8240.0
7.8 F
detection limit
DW-43 IW-54
10.0
5.0
4.7
8.0
116.0
8.3
4.1
109000.0
7.0
5.0
5.0
32.0
5.0
18800.0
2.0
16.0
7710.0
176000.0
9.0
33.0
FB-01
59.0
2.0
82.0
7.0
5.0
5.0
21.0
71.0
2.0
16.0
1700.0
198.0
U
U
*
U
J
J •
1
U
U
J
J
U
U
U
J
J
U
J
U
J
U
J
J
U
U
U
J -
10.0 U
5.0 U
0.7 •
445.0 F
22.0 U
11.0 F
4.0 U
96400.0
28.0
5.1 J
68.0 J
6510.0 *
85.0 •
11600.0 F
236.0 *
16.0 U
3920.0 J
68700.0
20.0 J
872.0
FB-02
8.0 U
2.0 U
70.0 J
7.0 U
5.0 U
5.0 U
13.0 U
20.0 J
2.0 U
16.0 U
1700.0 U
•88.0 J
6.7 J 6.7 J
_
PW-54A
10.0 U
5.0 U
1.4 *
8.7 F .
22.0 U
11.0 F
4.0 U
103000.0
7.0 U
5.0 U
5.0 J
13.0 U
5.0 U
11900.0 F
2.0 U
16.0 U
3960.0 J
80300.0
7.9 J
8.3 J
FB-03
21.0 J
2.6 J
32.0 J
7.0 U
5.0 U
5.0 U
24.0 J
62.0 J
2.0 U
16.0 U
1700.0 U
54.0 J
20.0
DW-47
10.0 U
5.0 U
0.2 U
21.0 U
22.0 J
9.3 J
5.0 U
117000.0
9.0 J
4.0 U
4.8 J
242.0
34.0 J*
8490.0
19.0 F
9.0 U
1820.0 J
1150000.0
3.0 U
74.0
detection limit.
possible blank contamination.
PU Public Water Supply
FB Field Blank
F Failed quality
control review
per EPA
_-_ ______..
***" ~
--------------
~
_
_
-------
TABLE 1 (CONT'D)
COMPOUNDS DETECTED IN THE GROUND UATER SAMPLES TAKEN IN THE VICINITY OF UHC (JANUARY 1988) (1)
=ossB*BsaEBS=sss=s-c===z=s===s:=== = = = c = ===Kri!==r===:=ss==s:3Scs==== = = = = = = = = s =
WELL NO. MW-01 HW-09 MU-16
ORGAN ICS:
acetone 61.0 F
chloroform 2.0 J
carbon tetrachloride 55.0 *
INORGANICS:
aluminum 9.4 F
barium 8.3 F
calcium 88200.0
chromium • 8.2 J
copper 5.0 J
iron 73.0 F
magnesium 3540.0 F
manganese 2.5 F
potassium 1700.0 U
sodium 7280.0
vanadium 4.0 U
zinc 12.0 J
Notes:(1) All values are in ppb unless
10.0 U
5.0 U
0.2 U
142.0 J
5.8 J
115000.0
17.0
4.0 U
415.0 J*
2030.0 J
, 12.0 J
489.0 U
4840.0 J
5.2 J
10.0 J
noted otherwise
10.0 U
11.0
120.0 *
93.0 J
2.0 U
87600.0
7.0 U
15.0 J
324.0 F
9110.0
4.6 J
1700.0 U
59800.0
5.5 J
18.0 J
U Indicates element was analyzed for but not detected. The number
J Indicates an estimated value;
result is less
B Indicates the analyte was found in the blank.
* Exceeded State and/or Federal
MU Monitoring Well
F Failed quality control review
than the specified
MU-16 DUP.
10.0 U
12.0
140.0 •
52.0 J
2.0 U
62700.0
23.0
19.0 J
466.0 *
8660.0
9.0 J
1700.0 U
57100.0
4.0 U
22.0
MU-18
10.0
21.0
160.0
21.0
7.6
93200.0
5.0
4.0
15.0
3310.0
2.7
489.0
18800.0
3.0
6.3
U
*
U
J
U
U
J
J
J
U
U
J
HU-19
10.0
5.0
2.9
22.0
7.8
89200.0
9.1
4.0
47.0
4030.0
3.8
489.0
22600.0
3%0
5.8
U
U
*
F
J
J
U
J
J
J
U
U
J
MU-20
10.0 U
5.0 U
0.2 U
127.0 J
3.7 J
88500.0
9.9 J
5.1 J
227.0 J
2710.0 J
17.0
489.0 U
10400.0
3.6 J
18.0 J
MU-21
41.0 F
2.0 J
' 59.0 *
162.0 J
19.0 J
126000.0
7.0 U
5.0 J
287.0
57400.0
2.0'U
14500.0
570000.0
6.8 J
9.3 J
MW-22
10.0
4.0
44.0
77.0
9.6
107000.0
15.0
4.0
288.0
20400.0
8.2
3720.0
577000.0
3.0
10.0
U
J
*
J
J
U
J
J
U
J
shown is the detection limit.'
detection limit
.
Indicates possible blank contamination.
Guideline or Criteria
per EPA
£====5=
-------
TABLE 2
SUMMARY OF CARCINOGENIC RISKS FROM CARBON TETRACHLORIDE
EXPOSED
POPULATION
Adult resident
!
Plant Workers
EXPOSURE
ROUTE
Ingestion
Inhalation
Inhalation
EXPOSURE
MEDIUM
Groundwater
*
Ambient Air
Ambient Air
EXPOSURE
POINT
AH Robins
Cambalache
Forest Area
Garrochales
Area
Cano Tiburones
i
Nearest
Residence
Air-Stripping
Unit
CANCER RISK
2.3 x iO-4
i1.
. 8 . 8 x l'iO-5
i|
6.9 x l'p-5
; i
5.8 x ljb-5
;)
3.9 x 1^0-7
1.6 x 10-5
i
-------
TABLE 4
SUMMARY OF POTENTIAL APPLICABLE OR RELEVANT AND APPROPRIATE
STATE AND FEDERAL REGULATIONS AND GUIDELINES AND CRITERIA
TO BE CONSIDERED FOR POTABLE DRINKING WATER *•
COMPOUNDS PRIM. SEC.
ORGAN I CS:
acetone
benzene
2-butanone
carbon tetrachloride
chloroform
toluene
1,1,1-trichloroe thane
INORGANICS:
aluminum
antimony
arsenic 50.0
barium 1000.0
beryl 1 ium
cadmium 10.0
calciun
chromium
cobalt
copper 1000.0
iron ' 300.0
lead 50.0
magnesium
manganese 50.0
mercury 2.0
nickel
potassium
selenium 10.0
silver 50.0
sodium
thai I ium
vanadium
zinc 5000.0
===============================================
PRDOH - Puerto Rico Department of Health
MCLG MCL PRDOH PRDCH
RULE #50 NHCR
0.0 5.0 5.0
0.0 5.0 50.0
50.0
2000.0** 50.0
200.0 200.0 100.0
50.0 50.0
1500.0 1000.0
5.0 . 10.0
120.0 50.0
1300.0
20.0 . , 50.0
3.0 2.0
45.0 10.0
50.0
=================================================
NHCR - Regulations for maximum level of contamination.
* all units in- parts per billion
(ppb).
** Proposed Recommended Maximum Contaminent Level, Fed. Reg. 11/13/85
===============================================
===4==============================================
-------
ATTACHMENT 1
COMMONWEALTH OF PUERTO RICO / OFFICE OF THE GOVERNOR
r Environmental
Quality Board
September 23, 1988
Mr. Carlos E. O'Neill
Acting Director
Caribbean Field Office, EPA
1413 Fernandez Juncos Avenue
Santurce/ Puerto Rico 00909
RE: UPJOHN MANUFACTURING,CO.
BARCELONETA, PUERTO RICO
Dear ,'Mr. O'Neill: ',\
•j
The Environmental Quality Board received the Proposed Plan for Remedial
Action for Upjohn Manufacturing Co., Barceloneta which included a modified
Alternative 3 as the recommended alternative by the Environmental
Protection Agency (E.P.A).
This alternative is a modification of Alternative 3, Moderate Control
of the Contaminant/ as presented in the Feasibility Study for this
facility. It involves continued pumpage with treatment of well UE-1, A.H.
Robins and Garrochales 3 with the installation and operation of two new
extraction wells. Under this alternative Garrochales 3 would continue to
be used as a potable water source following well-head treatment;, ground-
water from UE-1 and A.H. Robins would be treated and discharged to an
existing sinkhole located northwest of the Upjohn facility; the two
extraction wells would also be treated and discharged to that sinkhole.
Long-term ground water monitoring would be implemented. If the two new
installed wells prove to be effective in controlling and removing the
contaminants as well to protect the aquifer from saline instruction, E.P.A.
maintain the option of install additional extraction .wells.
After the corresponding evaluation, this Board concurred with E.P.A.
that this is the most environmental sound and safe alternative.
OFFICE OF THE BOARD: 204 DEL PAROUE ST. CORNER OF PUMARADA ,' WJLING ADDRESS: PO BOX 11488.
SANTURCE. PUERTO RICO 00910 ' TELEPHON^ T>SV*n
-------
Nevertheless/ we want to emphasize the importance of long-term groundwater
monitoring at Garrochales 3 to assure the quality of the drinking water
that would be serve to the comnunity.
Should you have any question/ please contact me at (809)122-1151.
Sincere!;?
Heri
A'
s, Ph. D
esident
cc: Mr. Pedro A. Gelaberti
Mr. Jose Font ',}.
Mr. Santos Rohena J
Mr. Juan Merced Matep
JP-bss
-------
RESPONSIVENESS SUMMARY
UPJOHN MANUFACTURING COMPANY SUPERFUND SITE
BARCELONETA, PUERTO RICO
A. OVERVIEW
On July 12, 1988, the U.S. Environmental Protection Agency (EPA)
Region II Office began a 30-day comment period on the 1988 Feasibility
Study (FS) and the proposed alternative for remediation of the
Upjohn Manufacturing Company (UMC) Superfund site in Barceloneta,
Puerto Rico. Prior to the public comment period, EPA had selected
a preferred alternative for the UMC site. The preferred alternative
outlined in the proposed remedial action plan (PRAP) consisted of
extracting contaminated groundwater by pumping two existing wells
(UE-1 and A.H. Robins), installing two new groundwater extraction
wells for the same purpose, and continuing to use the Garrochales
#3 public supply well as a drinking water source after installing
an air stripper to remove any contamination. Additional extraction
wells could be installed if the two initially installed wells are
effective at removing contaminants. Extracted water from the
UE-1, A.H. -Robins, and new extraction wells would be treated .by
air stripping and recharged back into the aquifer. The preferred
(alternative also called for long-term groundwater monitoring.
Based on comments received during the public comment period,
local residents and officials support the active control of
contaminants through groundwater extraction. Citizen concern
centered mostly on the effect of the contamination on the nearby
river, Cano Tiburones, and the time frame for remediation. UMC
felt that EPA should select the alternative proposed by the
company's FS, specifically, to continue pumping only the UE-1 well
to extract contaminated groundwater from the aquifer and to replace
contaminated water supplies wherever necessary.
These sections follow:
0 Community Involvement in the Selection Process
0 Summary of Major Comments Received During the
Public Comment Period and Agency Responses
0 Attachment 1: Proposed Remedial Action Plan
0 Attachment 2: Proposed Remedial Action Plan
(Spanish Version).
0 Attachments 3-7: Written Comments
-------
-2-
B. COMMUNITY INVOLVEMENT IN THE SELECTION PROCESS
On the evening of July 21, 1988, EPA held a public meeting at the
Mayor's Office in Barceloneta, Puerto Rico to present the findings
of the FS and the PRAP for the UMC site. Because Spanish is the
primary language of the majority of the local residents, the
meeting was held in Spanish to foster public involvement. A
member of the EPA Caribbean Field Office staff summarized and
translated questions to and responses from non-Spanish speaking
EPA representatives at the meeting. In addition to being available
at the information repositories, copies of the PRAP, in English
and Spanish, were handed out at the meeting. The two-and-a-half
hour public meeting was attended by approximately 35 persons.
Earlier in the day, EPA held a briefing for Commonwealth and
local officials which was attended by approximately 20 people.
Questions raised during both the public meeting and the briefing,
and written questions and comments received by EPA during the
public comment period are addressed in Section C of this respon-
siveness summary.
C. SUMMARY OF MAJOR COMMENTS RECEIVED DURING THE PUBLIC
COMMENT PERIOD AND EPA'S RESPONSE TO COMMENTS
Both verbal and written comments received during the UMC comment
period on the draft FS and PRAP are summarized below. The comment
period was held from July 12 to August 10, 1988. The comments
are categorized by topic, and similar questions have been con-
solidated and summarized.
Remedial Alternative Preferences
1. The Puerto Rico Department of Natural Resources (PRDNR) is in
favor of EPA's preferred alternative with the following exceptions:
0 The Garrochales #3 well should only be used for aquifer
remediation, with reinjection of treated water into the
aquifer. This well should not be used as a source of potable
water.
o
A new potable water source should be supplied from the
artesian aquifer by either installing a new well or by
using the Tiburones well.
-------
-3-
EPA RESPONSE; During the remedial design phase -of the imple-
mentation of the selected alternative EPA will evaluate the
possibility of replacing treated water from the Garrochales 13
well with an alternate water supply from the artesian aquifer.
Since the pumpage of the Garrochales 13 well is not an integral
part of the remediation scheme called for under the selected
alternative, this well may be taken out of service should an
artesian well be installed. Issues such as the safe yield of the
Cibao/Lares formation, its water 'quality, whether connections to
a public distribution system exist, and optimum placement of an
artesian well would take time to address, as would the actual
installation of the well. Because of the time required to implement
a new water supply from the artesian aquifer, EPA believes the
Garrochales #3 well water should be air stripped, as a precautionary
measure, until the new system is provided for, if ever, or until
carbon tetrachloride (CC14) levels in the aquifer meet the Maximum
Contaminent Level (MCL) of 5 ppb for CC14-
Thei Mayor of Barceloneta was strongly opposed to providing water
to jthe Garrochales community from the Tiburones artesian well.
Therefore, this option will not be further evaluated.
B. The United States Geological Survey (USGS) prefers Alternative
3 because it will achieve greater aquifer restoration without
seriously threatening the aquifer from salt water encroachment,
and strongly supports a long-term groundwater monitoring program
and recharge of treated groundwater into the aquifer. USGS
rejects Alternative 4 because it significantly increases the
potential for salt water encroachment in the Garrochales area.
EPA RESPONSE; EPA's selected alternative is a modification of
Alternative 3, which will include a long-term groundwater monitoring
program and recharge of treated groundwater into the aquifer.
EPA recognizes the importance of protecting the water table
aquifer from salt-water intrusion, and will request .the full
involvement of USGS during the review process for this project.
3. UMC recommends the continued operation of the UE-1 groundwater
extraction well with treatment by air stripping and recharge
through the existing sinkhole, continued groundwater monitoring,
and the provision of alternative sources of potable water if
required. UMC believes current groundwater conditions at the
Garrochales #3 well do not justify treatment, and, if they did,
that replacing the Garrochales #3 well with an artesian well is
feasible and could be implemented quickly and at a lower cost.
-------
-4-
EPA RESPONSE; EPA rejects UMC's recommendation to operate only
the existing groundwater extraction well, UE-1, and not to install
additional extraction wells. The UE-1 well is only capable of
removing contaminants and controlling migration within its cone
of depression. Any contaminants present in the aquifer downgradient
of AH Robins will not be controlled by the UE-1 well and will .
continue to migrate to Cano Tiburones. UMC's recommended action
would rely very heavily on natural aquifer flushing and dilution
to restore the aquifer and would render the aquifer unusable for
a longer period of time than would EPA's selected alternative.
The Garrochales #3 well lies in the pathway of contaminant migration,
Historic as well as recent sampling of this well indicates the
presence of CC14 at levels less than the MCL of 5 ppb. However,
the possibility exists that CC14 contaminant levels in this well
could rise in the future. For this reason, EPA believes treatment
of the Garrochales #3 well, as a precautionary measure, is justified,
EPA will evaluate replacement of the Garrochales #3 well with an
. artesian well during the design phase of the selected alternative.
(See response to comment fi above.)
Technical Questions/Concerns
4. Several people asked how long each alternative would take to
remove all of the contaminants from the aquifer.
EPA RESPONSE; Due to the complex nature of the hydrogeology in
the area and the possibility that residual CC14 contamination may
exist in the unsaturated zone and may represent a persistent
source of contaminants to the groundwater, it is not possible to
determine the exact or approximate time frames for total aquifer
remediation, if at all feasible, for any of the four alternatives.
It is believed that active pumping of the aquifer as proposed
under Alternative 2 and to a much greater extent under Alternatives
3 and 4 will remove contaminants more quickly from the aquifer
than the No Action Alternative. How much faster cannot be
determined.
5. A member of the community asked why EPA proposed two and not
three or seven new groundwater extraction wells.
EPA RESPONSE; Alternative '3 includes the installation of two
extraction wells. Alternative 4 includes the installation of
seven extraction wells. Because of the uncertainty of the effect-
iveness of groundwater extraction wells at removing contaminants
in this type of geological setting, EPA did not feel it would be
prudent to select Alternative 4. In addition, Alternative 4 is
very costly in comparison to the other alternatives. EPA cannot
say that Alternative 4 is'a cost-effective alternative given its
-------
-5-
cost and the questions regarding the effectiveness of/ the extraction
well system called for under Alternative 4.. Instead,,; EPA is
selecting a modification of Alternative 3, which includes the
installation of two extraction wells. If these two extraction
wells are shown to be effective at removing contaminants from the
aquifer, additional extraction wells will be installed for added
contaminant removal.
6. UMC asked how EPA would determine whether the groundwater
extraction wells proposed under the preferred alternative were
effective and what would be done if the wells were ineffective.
EPA RESPONSE; The effectiveness of the proposed extraction wells
in removing contaminants and controlling mig-ration of contaminants
in the aquifer will be assessed by the improvement in the quality
of the water downgradient of the contamination and the water
pumped from the extraction wells. If any extraction well is
determined to be ineffective at removing contaminants from the
groundwater, an evaluation will be made at that time as to whether
the well will remain in service.
7. UMC asked how salt water intrusion and vertical Upconing would be
addressed under the preferred alternative.
EPA RESPONSE; The selected alternative includes a monitoring
well network which will be installed to monitor the chloride
content of the groundwater. These monitoring wells will identify
salt water intrusion. In addition, the recharging of treated
groundwater as called for under the selected alternative will
significantly reduce the potential for salt water intrusion.
Vertical upconing of salt water will be addressed by monitoring
the extraction wells, including Garrochales #3, for chloride
content.
The information presented in the FS is a preliminary design and
will be fully developed during the design phase. It is EPA's
intention that extensive refinement of the monitoring network
design will occur during the design of the remedial action and
that the Commonwealth agencies will participate extensively in
the conceptual design and design review processes of the project.
Such issues as frequency of sampling and horizontal/vertical
placement of the wells are design choices and will be appro-
priately addressed during the design phase. It is suggested that
groundwater monitoring wells in the area of concern be sampled
and analyzed for conventional water quality parameters.
-------
-6-
8. UMC is unsure as to what the preferred alternative includes in
terms of the air-stripping systems and pretreatment;for these
systems. UMC has recently installed a pretreatment'/ system for
its air stripper. UMC believes its air stripper has been operating
reliably and that there is no justification to upgrade the system.
EPA RESPONSEt The selected alternative includes the upgrade of
the existing open basin aeration system to a packed column
aeration system, as well as the installation of a new packed
column aeration system for the Garrochales #3 well. These systems
would be designed to reduce CC14 contaminants in the effluent to
levels no greater than the MCL of 5 ppb. Pretreatment measures
will also be taken with respect to each aeration unit to reduce the
formation of scale. Packed column aeration has been selected
over open basin aeration because of the greater control, reliability
and removal efficiency afforded by the system.
EPA was unaware of UMC's recent installation of a pretreatment
system to its currently operating aeration system. During design,
EPA will review UMC's plans and specifications as well as operational
history of its pretreatment and aeration systems to reevaluate
the need for modifications to these systems.
9. UMC believes EPA's FS disregards possible contamination from
other sources, such as the Arecibo Landfill and the Cambalache
State Forest, both of which are included on EPA's CERCLIS list.
UMC states that if it is true that alternate sources are contri-
buting to the CC14 contamination and that these sources cannot be
remediated, then it is likely that EPA's preferred alternative will
not meet the MCL of 5 ppb for CC14 throughout the aquifer. UMC
asserts that if these sources can be remediated, then such remediation
may be less costly than and as effective as the EPA preferred
alternative in restoring the aquifer. Investigation of alternate
CC14 sources should be conducted and remediation of these sources
considered, UMC says, before the EPA preferred alternative is
adopted and implemented.
EPA RESPONSE; The Arecibo Landfill site and the Cambalache State
Forest site are both included on EPA's CERCLIS list, which lists
non-operational potential hazardous waste sites in the country.
Preliminary assessments and site inspections were performed for
both sites. Presently there are insufficient data and evidence to
support the conclusion that these sites are contributing to the
CC14 contamination in the groundwater at the UMC site.
Groundwater remediation should not be delayed until possible
'additional sources of contamination are fully investigated. The
information gathered to date indicates that releases from the UMC
facility are, at the very least, one of the primary sources of the
groundwater contamination affecting the site. Should, additional
-------
-7-
information indicate the contribution of CCJ-4 contaminants from
other sources, EPA will, if necessary, reevaluate the selected
alternative to determine whether modifications to the remedy
are appropriate. However, even assuming, arguendo, that releases
from other sources have also contributed to the~groundwater
contamination affecting the site, UMC is jointly and severally
liable with such other PRPs (if they exist) for the groundwater
contamination at the site.
10. UMC claims that all CC14 has been removed from vadose zone soils,
as .documented in the UMC Vacuum Assessment Report, dated March 23,
1987, and unless there is reason to reject this report, the EPA FS
should be revised to reflect the success of the vacuum extraction
system. UMC further states that it should not be stated that
CC14 remains in the soil and acts as a persistent secondary
source of contamination to the groundwater.
EPA RESPONSE; The vacuum extraction system would only have been
able to remove the vapor fraction of the CC14 and that portion o±
the liquid that was readily converted to vapor. Most of the of CC14
that was sorbed to soil particles would not have been removed.
Results of the soil sampling conducted by' UMC at four locations
where CC14 concentrations were once highest, as presented in the
UMC Vacuum Assessment Report of 1987, are not conclusive evidence
- that no more CC14 remains in the unsaturated zone. Also, the
consistently high levels of CC14 detected in the on-site well Uh.-l
give weight to the argument that a source of CC14 does exist in
the unsaturated zone.
11. UMC believes EPA's preferred alternative is technically infeasibie,
due to the presence of conduit flow which makes remediation
difficult, and is not justified. Compliance with the MCL of 5
ppb in karst terrain is technically impracticable from an engineering
perspective, UMC believes. UMC also asserts that the locations tor
the proposed extraction wells are remote, which will cause difficulty
in gaining access for their installation and maintenance.
EPA RESPONSE; Karst terraines have differing characteristics
world wide. This portion of the karst of Puerto Rico is known to
be dominated very strongly by diffuse flow. A study of the hydro-
geology in the Barceloneta area of Puerto Rico (both literature
and field studies) has shown that springs fed by diffuse flow
predominate in the Cano Tiburones (Quinlan, 1986, Beck, 1987,
Field; 1988). An examination of the springs in the Cano Tiburones,
the water level measurements in wells in the area, and the ability
of existing water wells to show measurable levels of CC14, lead
to the conclusion that diffuse flow is the dominant flow component
in the immediate area. Because of this, contaminant recovery
using groundwater extraction wells is feasible, given properly
located wells. Although conduit tlow may exist, the selected
alternative will be designed to primarily address the diffuse
component of the flow, although the conduit component of the tlow
may also be intercepted by the well system. To some extent, the
success of the UE-1 groundwater extraction well at removing
contaminants from the aquifer lends support to the technical
feasibility of extraction wells for contaminant recovery at,this
site.
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Although the overall goal of the clean up action is to meet the
MCL of 5 ppb for CC14 throughout the aquifer, EPA is not asserting
at this point that the selected alternative will achieve this. It
may be technically infeasible or impracticable to do, given the
unknowns of the hydrogeology. However, the selected alternative
is capable of removing contaminant mass from the aquifer, thereby
reducing contaminant levels, and in doing so, will provide for the
following protective measures to human health and the environment:
".reduction of cancer risk levels which will decrease the
reliance on institutional controls over future potable
well installations in the aquifer,
0 protection of presently unimpacted portions of the aquifer
(CC14 levels less than the MCL of 5 ppb),
9 prevention of further contamination of presently impacted
portions of the aquifer,
0 possible attainment of the MCL of 5 ppb,for CC14 in
large portions of the existing impacted areas, and
0 reduction of risk to Cano Tiburones and the lite it
supports.
EPA agrees with UMC's claim that the locations of the proposed
extraction wells under the selected alternative are remote,
which may cause difficulty in gaining access for their installation
and maintenance. EPA, however does not consider this difficulty
sufficient justification to reject the selected alternative.
12. UMC claims that the cost/benefit analysis for .the preterred
alternative was inadequately performed by EPA. In addition, UMC
asserts that the preferred alternative is not cost-ettective
because there is no documented risk to human health and the envir-
onment from the 1982 UMC incident.
EPA RESPONSE; When selecting a remedy, EPA performs a cost-
effectiveness analysis, and in doing so, judges an alternative
first on its degree of effectiveness. Of the. alternatives
which provide for the required degree of effectiveness, the least
costly is selected.
EPA believes that the selected alternative is' cost-effective.
Extraction wells will be added sequentially, up to a total of
approximately four additional wells aside from the initial two
new wells, provided the wells are shown to be effective"or have a
high probability of success at removing contaminants from the
aquifer.
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An endangerment assessment /report, dated September 12, 1988, was
prepared for the UMC site. Y This report documents the existence of
potential risks to human health and the environment from the 1982
UMC incident if no further remedial action were to be taken.
Risks to human health exist if institutional controls restricting
aquifer use fail, and new wells are installed for drinking purposes.
In addition, risks to the environment exist due to the fact that
the groundwater is contaminated. As a result of this contamination,
the aquifer, as a resource, is lost without remediation.
13- UMC believes EPA erred by using the MCL tor CC14 as an applicable
or relevant and appropriate requirement (ARAR) based upon its
classification of the aquifer as Class I groundwater.
EPA RESPONSE1 EPA has reconsidered its prior classification of the
aquTfer as Class I groundwater and has reclassified the aquifer a
Class II groundwater (current or potential source of drinking
water). Although the water table aquifer is replaceable (i.e.,
wells can be pumped from the confined aquifer for potable water),
it still remains a potential drinking water source. Therefore,
MCL's are still appropriate remediation levels.
UMC believes that the rationale for EPA's selection of the preferred
alternative is simply that the technology is available.
EPA RESPONSE: This statement is not true. There are unacceptable
existing and/or threatened environmental and public-health impacts
that make EPA's selected alternative necessary and appropriate.
15. UMC believes that due to the heterogeneous nature ot the'aquiter,
the success of one extraction well does not ensure that the location
selected for the next well will be as effective.
EPA RESPONSE; EPA agrees with UMC's statement to a certain extent.
However, EPA believes that with a very carefully conducted oftice
and field investigation, including a lineament and fracture trace
analysis, extraction wells could be placed with a relatively high
degree of confidence that these wells would be successful at
removing contaminants from the aquifer. The well system called
for under the selected alternative, as an interim remedy, will be
evaluated within 5 operational years to determine the practicability
and cost-effectiveness of cleaning up all or portions of the
aquifer and to specify the type of further action to be taken.
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16. UMC claims that the\EPA FS acknowledges that because of potential
salt water intrusion1, problems, USGS and PRDNR would take the position^
that EPA's preferred alternative would not meet the substantive
requirements of a pefpnit. UMC also says that USGS has questioned
the effectiveness of) chloride monitoring and groundwater recharge
in preventing salt water encroachment.
•.y
EPA RESPONSE; It is incorrect that the EPA FS "acknowledged" the
likelihood that USGS and PRDNR would probably not grant a permit.
Both USGS and PRDNR reviewed and submitted comments on EPA's FS and
PRAP. Their comments have been incorporated into this Responsiveness
Summary. Neither USGS nor PRDNR commented that the selected alter-
native would not meet the substantive requirements of a permit, nor
did USGS question the effectiveness of the chloride monitoring and
groundwater recharge systems called for under the selected alter-
native in preventing salt water encroachment. The chloride monitor-
ing and groundwater recharge systems presented in the FS and ROD
will be extensively refined during design with the full participation
of USGS and PRDNR.
17. UMC criticizes EPA's preferred alternative by stating that EPA
cannot quantify the degree to which the remedy will speed up the
restoration of the aquifer.
EPA RESPONSE; EPA believes that the selected remedy, which is
capable of removing contaminant mass and reducing contaminant con-
centration levels within the aquifer, will restore the aquifer more
quickly than attenuation which relies totally or predominantly on
natural movement and dispersion of the contaminants. EPA does not
believe that quantification of the time frame for restoration is
needed to justify our posi-tion that the selected remedy is more
protective of public health and the environment than the alternatives
which rely on natural processes or limited extraction of groundwater.
18. UMC claims that one measure of cost-effectiveness is the, cost to
remove each gallon of CC14, and that the preferred alternative
proposed to spend as much as 14.5 million dollars to remove the
estimated 50 gallons of CC14 remaining in the aquifer.
EPA RESPONSE; EPA does not believe that UMC's measure of cost-
effectiveness, referred to above, is a sound approach to evaluating
costeffectiveness. In addition, UMC's argument assumes that there
are only 50 gallons of CC14 left in the groundwater. UMC has not
presented a sound basis to support this claim.
19. UMC claims EPA's FS does not fully identify explanations for the
mass balance discrepancy, that is, the fact that the amount of CC14
removed from the soil and groundwater is greater than the amount of
CC14 released from the ruptured tank. UMC states that there are
additional explanations as follows: 1) inaccuracy of the measurement
of vented CC14 vapors removed, and 2) inaccuracy in the'estimate of
the amount of CC14 lost. UMC believes these events are much likelier
reasons for mass balance discrepancies than the possibility of a
previous spill, as stated in the EPA FS. UMC says that all tanks
previously located in the tank farm area were inspected following
the spill and that results indicate that none could have contributed
to significant quantities of CC1 in the soil and groundwater.
4
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In addition, UMC refers to sampling and analysis of the AH Robins
well in May 1981, which did not reveal any CC14 in the groundwater.
UMC implies that a previous leak from the UMC tank farm would
probably have been detected in the Ah Robins well during the 1981
sampling.
EPA RESPONSE ; EPA believes that UMC ' s additional explanations tor
the mass balance discrepancy are possible. However, these explan-
ations are no more probable than the explanations presented in the
EPA FS . EPA was unaware that inspections were performed on every
tank in the tank farm. The 1984 Geotec RI/FS Report only included
inspection reports for thirteen tanks in the tank farm. Inspection
reports for tanks FA-102, 103, 105 and 128, which were used to
store CC14 at one time or another, were not included. The Geotec
report indicated the possibility of additional spills or leaks near
the tank farm from loading and unloading stations and from mainten-
ance work on pipe and tank fixtures within the tank farm. A possi-
bility also exists that the ruptured tank could have been slowly
leaking for a period of time before its failure was discovered.
With regards to the sampling of the AH Robins well, it is possible
that additional tank leaks and/or spills could have occurred between
May 1981 and August 1982, or that leaks/spills that occurred belorlt
May 1981 had not yet impacted the AH Robins well. I
*
UMC claims EPA ' s FS does not contain alternative methods of remediation
as required by the National Contingency Plan (NCP). UhC also states
that EPA's "No Action" alternative is not truly a "No Action"
alternat ive.
EPA RESPONSE; Although not present in the EPA FS report, EPA
considered alternative treatment technologies for addressing the
residual groundwater contamination. These technologies are presented
in the Record of Decision.
EPA believes that its No Action alternative is a bona f^de No Action
alternative. The fact that it would involve changing the~"status
quo" by ceasing the pumping of well UL-1 does not mean that the
alternative is not a No Action alternative.
21. UMC claims that, since only approximately 50 gallons of material
from the spill remain in the aquifer, at mos.t, EPA's preferred
alternative will only speed up the restoration of the aquifer by an
insignificant degree.
EPA RESPONSE ; UMC presents . no technical argument for its belief
that only 50 gallons of material from the spill remain in the
aquifer. In addition, EPA believes that the selected alternative
is capable of significantly speeding up restoration of- the aquifer.
The selected alternative, as an interim remedy, will be reevaluated?
within five years of operation of the- well system to determine the
system's capability of restoring all, or portions of, the aquifer.
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22. A community member wanted to inform EPA that rainwater runoff
discharges into two sinkholes in the area; one at Cruce-Davila,
and the other at the UMC facility, and was concerned whether the
preferred alternative included discharge into one of these sinkholes
EPA RESPONSE; The selected alternative includes discharge of
treated groundwater into the sinkhole located at the UMC facility.
EPA does not consider the rainwater runoff discharging into this
sinkhole to be of any concern.
23. A community member inquired as to the location of the sampling
point where CC14 was recently detected at the Cano Tiburones.
EPA RESPONSE; La Cambija spring, which feeds into Cano Tiburones,
is where recent sampling conducted detected 13 ppb of CCl4« This
spring is located approximately 2000 feet south of Cano Tiburones.
24. A community member told EPA that in order to comment adequately
on the preferred alternative, exact locations of the extraction
wells, discharge points and monitoring wells would be required.
EPA RESPONSE; The exact locations of these items will be determined
during the design phase of the project. The FS report illustrates
only conceptual locations of where these items would be placed,
as can be seen on Figure 15 in the FS report. EPA does not
believe that actual locations are crucial to being able to comment
on the selected alternative.
Extent of Contamination
25. EPA was asked what is _being done currently to control contaminated
water and how far the'area of contamination extends.
EPA RESPONSE; Since 1984,-UMC has been operating the UE-1 ground-
water extraction well, which extracts contaminated groundwater,
treats this water with an air stripper, and discharges treated
water into an existing sinkhole. The UE-1 well is only capable
of controlling a small portion of the contamination, that portion
nearest to the UMC property. This well has no control over the
contamination which currently exists outside of the well's cone
of depression. Based on 1988 sampling data, it .appears that the
contamination within the diffuse component of the groundwater flow
extends approximately 8500 to 9000 feet north of the UMC property
and may encompass approximately one square mile. This delineation
is based solely on the location of the wells which limits the
accuracy of delineating the extent of contamination. EPA believes
the CC14 contamination which exists within the conduit flow portion
of the aquifer may extend beyond what is reported above.
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26. A community member asked if the contamination was moving south from
the site.
EPA RESPONSE: Historic as well as recent sampling of the groundwater
indicates that the contamination is migrating to the north, as is
expected, following the direction of regional groundwater flow.
27. A community member asked if the contaminated groundwater could
rise up and contaminate the soil.
EPA RESPONSE; It is possible that contaminated groundwater could
rise high enough to pollute the overlying soils. This possibility
depends on the depth of the soil profile and the rise of the
groundwater. EPA believes that this is an unlikely possibility,
and if it has occurred, would not affect dissolved groundwater
concentrations significantly.
28. A community member asked EPA to explain why the Garrochales #3
well was not contaminated if the UMC site and the Cano Tiburones
were both contaminated and the Garrochales #3 well lies, between
them. , ' • •
EPA RESPONSE; Recent as well as historic sampling of the
Garrochales #3 well indicates CC14 contamination at levels below
the MCL of 5 ppb. It is possible that given the varied groundwater
flow paths typical of karst formations, some of the contaminated
groundwater could have bypassed the Garrochales #3 well and
migrated to the Cano Tiburones.
29. The President of the Municipal Assembly.of Barceloneta asked
if any sampling at Cano Tiburones in Arecibo was conducted to see
if contaminants from the 1982 UMC incident are migrating towards
Arecibo.
EPA RESPONSE; EPA was unaware of any sampling conducted at the
Cano Tiburones in Arecibo. EPA believes it is unlikely that the
migration of contaminants present in the groundwater, resulting
from the 1982 UMC incident, would pose a risk to the Cano Tiburones
in Arecibo. UMC informed the community at the public meeting
that it had conducted sampling in 1985 of the Cano in Arecibo and
did not detect the presence of CCl^ contaminants.
30. EPA was asked what the source of water was to the communities
of Boca, Punta Palmas and Palmas Altos.
EPA RESPONSE; EPA did not know the answer to this question. The
Mayor of Barceloneta informed the community at the public meeting
that the communities in question lie outside of the area which
was studied by EPA in the FS report..
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Effects on Human Health and the Environment
31. Several community members asked what effect CCl4 contaminants
would have on the Cano Tiburones and the aquatic life it supports.
EPA RESPONSE; Little sampling has been conducted in the past in
the Cano Tiburones to allow for an accurate determination of CC14
contaminant levels present. Sampling of one spring, La Cambija,
which feeds into Cano Tiburones, was conducted by EPA in January
1988. Results indicate CC14 levels at 13 ppb. The FS report
states that dilution of contaminants is expected to occur as the
contaminants migrate from their present locations and discharge
into Cano Tiburones. The amount of dilution cannot be accurately
determined. However, it is expected that concentrations entering
the Cano would be low. The endangerment assessment report prepared
for the UMC site estimated through modelling that a maximum CC14
concentration level of 262 ppb would be detected in the -Cano
approximately 11.4 years after the spill occurred if no further
remedial action was to be taken. Chronic human ingestion of the
water in Cano Tiburones was estimated to result in a 5.8 x 10~5
cancer risk. Ingestion of contaminated fish is not expected to pose
a threat to human health due to the low bioconcentration, factor
of CC14 which results in minimal uptake by fish. Chronic toxic
effects of contaminants may adversely effect aquatic life of the
Cano. However, impacts to aquatic life from existing and future
contaminant concentrations are expected to be low.
32. What risk did local residents face in the past and what is the
current risk to residents from the contamination until the remedy
is implemented?
EPA RESPONSE; Shortly following discovery of the spill in September
1982, local water supply wells were sampled. Those found to be
contaminated or threatened were shut down. UMC provided alternate
water supplies. Therefore, any risk to local residents in the
past from drinking contaminated water would be low. At the
present time, the levels of CC14 in the Garrochales 13 well do
not exceed the MCL of 5 ppb. Human health is currently not at
risk. However, the endangerment assessment report documented
potential risk to human health if no further remedial action were
taken at the site to reduce contaminant concentration levels in
the aquifer.
Installation of an air stripper at the Garrochales 13 well would
be the first of the remedial actions called for under the selected
alternative to be implemented at the site. Design and installation
of the system would be placed on a priority basis to reduce any
potential exposure to contaminated water from this well.
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