PB95-963926
EPA/ROD/R03-95/218
May 1996
EPA Superfund
Record of Decision:
Naval Air Development Center (O.U. 3),
Bucks County, Warminster Township, PA
3/10/1995
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RECORD OF DECISION
NAVAL AIR DEVELOPMENT CENTER
DECLARATION
SITE NAME AND LOCATION
Naval Air Development Center
Warminster Township
Bucks County, Pennsylvania '
STATEMENT OF BASIS AND PURPOSE
This Record of Decision (ROD) presents the selected remedial
action for Operable Unit Three (OU-3) at the Naval Air
Development Center Site in Warminster Township, Bucks County,
Pennsylvania (the "Site"), chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA) of 1980, as amended, 42 TJ.S.C. § 9601 et sea, and,
to the extent practicable, the National Oil and Hazardous
Substances Pollution Contingency Plan (NCP),. 40 C.F.R. Part 300.
This decision is based on the Administrative Record for this
Site.
In January 1993, the facility was renamed Naval Air Warfare
Center (NAWC) Aircraft Division Warminster..
The Commonwealth of Pennsylvania has neither concurred nor non-
concurred with the selected remedy as of the date of this Record
of Decision. The concurrence/non-concurrence letter from the
Commonwealth will be added to the .Site Administrative Record upon
receipt.
ASSESSMENT OF THE SITE
Actual or threatened.releases of hazardous substances from this
Site, if not addressed by implementing the response action
selected in this ROD, may present an imminent and substantial
endangerment to public health, or welfare, or the environment.
DESCRIPTION OF THE SELECTED REMEDY
The selected remedy for OU-3 is the. third response action
addressing the Site. OU-3 consists of contaminated groundwater
attributable to Area C at the Site. (Previous response actions
have been selected and/or implemented to address Operable Units
One and Two, which consist of contaminated groundwater
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attributable to Areas A and B, and contaminated drinking water
supplies, respectively.) The objective of the selected remedy
for OU-3 is to restore contaminated groundwater attributable to
Area C to a level protective of human health and the environment.
Future actions at the Site will address disposed waste, soils,
additional groundwater, and other media, as necessary to protect
human health and the environment.
The selected remedy for OU-3 includes the following major
components:
• Installation, operation and maintenance of groundwater
extraction wells
• Installation, operation and maintenance of an onsite
groundwater treatment system which includes precipitation,
filtration, air stripping and carbon adsorption, and/or
other necessary means of treatment
• Periodic sampling of treated water to ensure the
effectiveness of the treatment system
• Discharge of treated water to an unnamed tributary of Little
Neshaminy Creek
• Installation, operation and maintenance of a vapor phase
carbon adsorption unit (if such a unit 'is necessary to
control air emissions)
• Offsite treatment and/or disposal of solid residuals
generated during water treatment and control of air
emissions (if necessary)
• Monitoring of groundwater in monitoring wells and
residential wells
• Installation and periodic sampling of observation wells to
ensure the effectiveness of the groundwater extraction wells
• Periodic review of hydrogeologic data to evaluate the
effectiveness of the groundwater extraction wells
• Modification of the groundwater extraction well system
and/or groundwater treatment system as necessary based on
periodic evaluations
STATUTORY DETERMINATIONS
Pursuant to duly delegated authority, we hereby determine,
pursuant to Section 106 of CERCLA, 42 U.S.C. § 9606 that the
selected remedy is protective of human health and the
environment, complies with Federal and State applicable or
relevant and appropriate requirements directly associated with
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this action, and is cost-effective. This remedy utilizes
permanent solutions and alternative treatment (or resource
recovery) technologies to the maximum extent practicable, and it
satisfies the statutory preference for remedies that employ
treatment that reduces toxicity, mobility or volume as their
principal element. Subsequent actions are planned to address
other threats posed by the conditions at the Site.
A review will be conducted within five years of the initiation of
the remedial action and every five years thereafter, as required
by Section 121(c) of CERCLA, 42 U.S.C. Section 9621(c), to ensure
that the remedy continues to provide adequate protection of human
health and the environment.
Date
Thomas C. Ames
BRAC Environmental Coordinator
Naval Air Warfare Center, Warminster
Date
Thomas C. VoItaggi^f Director
Hazardous Wa^te/Management Division
EPA Region III
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Concurrences
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RECORD OF DECISION
TABLE OF CONTENTS
SECTION PAGE
I. SITE NAME, LOCATION, AND DESCRIPTION 1
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES 3
III. HIGHLIGHTS OF COMMUNITY PARTICIPATION 10
IV. SCOPE AND ROLE OF THIS RESPONSE ACTION 11
V. SUMMARY OF SITE CHARACTERISTICS AND EXTENT OF
CONTAMINATION 11
VI. SUMMARY OF SITE RISKS 21
VII. DESCRIPTION OF ALTERNATIVES 25
VIII. COMPARATIVE ANALYSIS OF ALTERNATIVES 27
IX. SELECTED REMEDY ' 30
X. STATUTORY DETERMINATIONS 34
XI. DOCUMENTATION OF SIGNIFICANT CHANGES .37
XII. RESPONSIVENESS SUMMARY 38
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FIGURES
NUMBER
PAGE
1 NAWC Site Location Map . 2
2 NAWC Waste Disposal Locations Map 5
3 Area C Detail 6
4 Area C Well Locations 17
TABLES
NUMBER
1 Summary of Waste Management and Site Operations . . . .
2 Frequency of Occurrence and Distribution of Positively
Detected Substances in Area C Monitoring Wells . . . .
3 Summary of Noncarcinogenic Risks - Area C Groundwater
4 Summary of Carcinogenic Risks - Area C Groundwater . ,
PAGE
19
24
24
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RECORD OF DECISION
NAVAL AIR DEVELOPMENT CENTER
DECISION SUMMARY
I. SITE NAME, LOCATION, AND DESCRIPTION
The Naval Air Development Center is a 734-acre Naval facility
located in Warminster Township, Bucks County, Pennsylvania (see
Figure 1 for Site Location Map). In January 1993, the Naval
facility was renamed Naval Air Warfare Center (NAWC) Aircraft
Division Warminster. The Site lies in a populated suburban area
surrounded by private homes, various commercial and industrial
activities, and a golf course. On-site areas include various
buildings and other complexes connected by paved roads, the
runway and ramp area, mowed fields, and a small wooded area.
The longest runway, which is currently the only active runway, is
generally located along the topographically highest area at the
Site. Many of the primary NAWC buildings are located west of the
airstrip, along Jacksonville Road, a public road which traverses
the Site from north to south. A housing development for military
enlisted personnel is within the southeastern portion of the
Site. A wastewater treatment plant (WWTP) owned and operated by
NAWC is located in the northwestern corner of the Site.
Commissioned in 1944, NAWC's main function is research,
development, testing, and evaluation for Naval aircraft systems.
NAWC also conducts studies in anti-submarine warfare systems and
software development. Under the Defense Base Realignment and
Closure Act of 1990 (Public Law 101-510), the NAWC will be
closed. All activities will be relocating to Patuxent River,
Maryland, with the exception of an enlisted men's housing area in
the southwestern corner of NAWC (see Figure 2). Current
schedules indicate the NAWC will be relocated by September 1997.
NAWC currently has approximately 2,000 employees, and 1,000
people reside at the enlisted men's housing area year round. The
closest off-base home is about 200 feet away from the NAWC
property line. Residential development is located along the
length of the southern property line of NAWC and to a lesser
extent, along the northern property line. Industrial development
is located along the west and northwest perimeter of NAWC
property. Groundwater is used extensively as a source of water
by both residents and industry in the immediate vicinity of the
Site. The Site is located on a ridge, generally oriented east-
west, with elevations ranging from 297 feet at the northwestern
property boundary to 377 feet at the eastern boundary. Onsite
slopes are gentle and average three to five percent.
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1000 2000 3000 4000 5000 6000 7000 FEE!
CONTOUR INTERVAL 10 FEET
NATIONAL GEODETIC VERTICAL DATUM OF 1929
20* MlliU
0*02'
ADAPTED FROM THE U.S.G.S. HATBORO. PA 7.5 MINUTE QUADRANGLE (1966, PHOTOREVISED 1983)
FIGURE 1
NAWC WARM1NSTER
SITE LOCATION MAP
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NAWC is situated on an upland area divided between two local
drainage basins, the Little Neshaminy Creek Basin on the north
and the Southampton Creek Basin on the south. The northern 65
percent of the Site (including Area C) drains toward the north
through several swales and storm sewers into small unnamed
tributaries of the Little Neshaminy Creek. The southern 35
percent of the facility drains toward the south to the headwaters
of Southampton Creek, a tributary of Pennypack Creek. Both local
drainage basins lie within the regional drainage basin of the
Delaware River. Several of the tributaries of Little Neshaminy
and Southampton Creeks originate at, or near, the outfall points
of culverts adjacent to the NAWC property boundary.
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
This section describes the history of waste disposal, and CERCLA
investigations and response actions at the Site.
A. HISTORY OF WASTE DISPOSAL
Historically, wastes containing hazardous substances have been
generated by NAWC during aircraft maintenance and repair, pest
control, fire-fighting training, machine and plating shop
operations, spray painting, and various materials research and
testing activities in laboratories. The wastes generated have
included paints, solvents, sludges from industrial wastewater
treatment, and waste oils. From 1940 to 1980, these wastes were
disposed of in pits, trenches, and landfills located on current
NAWC property. In addition, wastes generated by NAWC were burned
in a fire training area until 1988.
To date, eight (8) areas on current NAWC property have been
identified as areas used for the disposal of wastes containing
hazardous substances. A brief summary of these eight areas is
provided in Table 1. Figure 2 provides the locations of these
eight waste disposal areas. None of these areas are currently
used for waste disposal. For investigative purposes, sites 1, 2
and 3 have been grouped into Area A, sites 5, 6 and 7 have been
grouped into Area B, and sites 4 and 8 have been grouped into
Area C. Figure 3 depicts site 4 and site 8, and other
miscellaneous areas which collectively comprise Area C. Below is
a description of the history of Area C.
1. Site 4
Site 4 is currently a grass-covered area covering 7 acres just
north of the main runway along Kirk Road. Site 4 is the largest
of the waste disposal locations referenced above and is less than
100 feet from the NAWC property line and Kirk/Newtown Roads.
Private residences are located within approximately 200 feet of
site 4. Surface drainage from site 4 discharges via two
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TABLE 1
SUMMARY OF WASTE MANAGEMENT AND SITE OPERATIONS
NAWC WARMINSTER, PENNSYLVANIA
SITE
NO.
1
2
3
4
5
6
7
8
DATES OP
OPERATION
1940 to
1955
1965 to
1970
1955 to
1965
1966 to
1970
1955 to
1970
1960 to
1980
1950 to
1955
1961 to
1988
TYPES OF WASTES
Paints, oils, asphalt, roofing
material, unspecified chemicals,
firing range wastes
Industrial wastewater sludges
Solvents, paints, roofing
materials, and unspecified
chemicals
Non-industrial solid wastes,
paints, waste oils, waste
metals, construction debris,
solvents, and sewage treatment
sludge
Paints, solvents, scrap metal,
and 30 drums of asphalt
Paints, solvents, demolition
wastes, waste oils, other
flammable wastes, and grease
trap wastes
Industrial wastewater sludge
Aviation fuel, lubricants,
coolants
METHOD OF
OPERATION
Burn pit
within an
eroded
ravine
2 disposal
trenches
Burn pit
7 disposal
trenches
6 to 8
disposal
trenches
Unknown
number of
disposal
pits or
trenches
2 disposal
trenches
Firef ighting
training
area
POTENTIAL HAZARDS
Various solvents,
driers, pigments, PAHs,
creosote, phenols,
asbestos, binders, lead
Biological wastes,
heavy metals
Various solvents,
driers, pigments,
asbestos, binders
Various solvents,
driers, pigments, lead,
PAHs, biological
wastes, heavy metals
Various solvents,
driers, pigments,
creosote, phenols, PAHs
Various solvents,
driers, pigments, lead,
PAHs
Biological wastes,
heavy metals
PAHs, PCBs
ADAPTED bROM SMC MARTIN 1991 (TABLES 1-1 AND 4.3-4)
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OPEN FIELDS
AND SCATTERED
PRIVATE HOMES
RESIDENTIAL
DEVELOPMENT
INDUSTRIAL /
COMMERCIAL
AREA
^
°A° ~^:^r:^
RESIDENTIAL
DEVELOPMENT
FIGURL 2
MAWG WAK'MIMSTER
WASTE HiSF'OSAL LOCATIONS MAP
ADAPTED FROM HALLIBURTON NUS
PHASE II Rl REPORT FOR OU--1
(APRIL I99i) (riGURF: 1-2)
_spp • 1000
SCALC 111 rrn
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SCt'SCC: ADAPTED FRQ^ HALLIBURTON NUS Rl REPORT TOR QU-3 (AUGUST 1994KFIGURE 1-21
GEND
MONITORING WELL .
PRODUCTION WELL
A SOIL BORING
^-/FORMER
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culverts to two separate unnamed tributaries of Little Neshaminy
Creek located north of Kirk and Newtown Roads.
Site 4 reportedly was operated from 1966 to 1970. Up to seven
trenches on site 4 reportedly were used to dispose of non-
industrial solid waste, paints, waste oils, waste metals,
construction debris, solvents, and sewage sludge from the sewage
treatment plant. Each trench was reported to be approximately 12
feet wide, 1000 feet long, and nine feet deep. (The actual
dimensions of the trenches are unknown.) Based on this estimate,
a total of approximately 25,000 cubic yards of waste were
deposited, with each trench holding approximately 3,600 cubic
yards of waste. It is not known whether wastes were segregated
prior to disposal or were placed randomly into each trench.
2. Site 8
The fire-fighting training area (site 8) is at the end of an
abandoned runway running north off of the main airstrip.
Directly to the northeast of site 8 are Kirk Road and Werner
Park. Site 8 is about 300 feet from the NAWC property line and
400 feet from private residences on Kirk Road. A cement drainage
culvert receives runoff from site 8 and discharges this runoff to
an unnamed tributary of Little Neshaminy Creek which bounds
Werner Park to the west.
The training area consisted of a 75- by 75-foot portion of the
abandoned runway surrounded on three sides by a double soil berm.
The berms were approximately 3 to 5 feet high. Site 8 was used
for fire training exercises from 1961 to February 1988.
Typically, flammable materials were poured on ponded water or
debris on the runway, ignited, and extinguished to simulate fire-
fighting procedures. Aviation fuel, scrapped cars and aircraft,
and other debris were reportedly stored and burned within site 8.
An estimated 3,000 gallons of aviation fuel were disposed
annually at site 8. Historical aerial photos indicate that fire-
training activities extended about 100 feet further down the
abandoned runway during, earlier years. Historically, residents
along a unnamed tributary of Little Neshaminy Creek complained
about white fire fighting foam in the creek after fire-fighting
training exercises were held.
In October 1986, the Pennsylvania Department of Environmental
Resources (PADER) recommended excavation and disposal of fire
residuals and contaminated soils at site 8. By October 1988, the
double soil berms had been removed. NAWC personnel reported that
these berms, fire residuals, trapped liquids, and soil from
eroded areas, had been analyzed and removed. The berm material
was deposited in an area adjacent to site 8 and the area was
regraded.
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3. Miscellaneous Areas
A review of aerial photos and field observations indicate at
least two additional areas within Area C which may be a source of
hazardous substance releases. A pistol range was formerly
located about 800 feet south of site 8 (see Figure 3). Aerial
photos indicate standing liquids within a pit in the former
pistol range. The pit has since been filled in and no other
evidence of the former range is apparent at this time. Another
potential area of concern is a small complex of maintenance
buildings located approximately 400 feet southeast of site 8 (see
Figure 3). Based on field observations, these buildings
currently appear to be used primarily for storage and maintenance
of lawn care equipment.
B. CERCLA INVESTIGATIONS AND RESPONSES
The EPA completed CERCLA Preliminary Assessment (PA) and PA/Site
Inspection (SI) Reports in 1979 and 1985, respectively. In 1986,
the Site was proposed for inclusion on the National Priorities
List (NPL). On October 4, 1989, the Site was placed on the final
NPL. On September 20, 1990, the Navy and EPA signed an
Interagency Agreement (IAG) which established a procedural
framework for developing and implementing investigative and
response actions at the Site in accordance with CERCLA and the
NCP.
In response to the inclusion of the Site on the NPL and in
accordance with the IAG, the Navy has investigated hazardous
substance releases at the Site in three phases: a Phase I RI,
Phase II RI and a Focused RI, which is currently in progress.
The Phase I Remedial Investigation (RI) was initiated in late
1988 and was completed on September 11, 1990 with the release of
the Phase I RI Report. Phase I initiated the investigation of
sites 1 through 8 by screening these sites for volatile organic
compounds (VOCs) via soil gas analysis and detecting any buried
materials through electromagnetic surveys. The sites were also
investigated through soil borings and the installation and
sampling of shallow monitoring wells installed to monitor
overburden and shallow bedrock aquifers. In addition, test pits
were excavated, nearby wells were inventoried, and a bedrock
fracture-trace analysis was conducted.
The Phase II RI was initiated in late 1991. Phase II work
included the installation of additional overburden and shallow
bedrock monitoring wells, sampling and analyzing groundwater, and
an evaluation of aquifer characteristics through water-level
monitoring, slug and step-drawdown tests and a pumping test.
Four off-site wells were sampled during the Phase II RI.
Both the Phase I and Phase II RI investigated the nature and
extent of shallow groundwater contamination within the vicinity
of sites 1, 2, and 3 (collectively referred to as Area A), sites
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5, 6, and 7 (Area B) and sites 4 and 8 (collectively referred to
as Area C).
Based on the results of these investigations, the Navy completed
Remedial Investigation and Feasibility Study Reports addressing
contaminated groundwater in overburden and shallow bedrock
attributable to Areas A and B (identified as Operable Unit One or
OU-1) in April of 1993. The Navy subsequently issued a Proposed
Plan addressing OU-1 on April 26, 1993 and jointly signed a
Record of Decision (ROD) with EPA for OU-1 on September 29, 1993.
The ROD for OU-1 selected an interim remedy which included the
pumping and treatment of groundwater to limit the migration of
contaminated groundwater attributable to Areas A and B.
Beginning the week of April 28, 1993, the Navy initiated the
sampling of offsite wells to assess the impact of contaminated
groundwater attributable to NAWC on offsite groundwater users.
Through September 30, 1994, the Navy had sampled more than 500
wells over several rounds of quarterly sampling. Seven (7)
residential wells sampled exceeded EPA Removal Action Levels,
while an additional thirty-nine (39) residential wells exceeded
Maximum Contaminant Levels (MCLs) (developed pursuant to the Safe
Drinking Water Act). At least part of this contamination is
potentially attributable to the Site. In response, the Navy has
conducted a CERCLA removal action, installing a water treatment
system in each residence where either EPA Removal Action Levels
or MCLs have been exceeded.
The EPA determined this offsite groundwater contamination may
present an imminent threat to human health. In response, the EPA
and the Navy have conducted additional CERCLA removal action work
which provided residences exceeding EPA Removal Action Levels, as
well as residences in the immediate path of the groundwater
contamination, with connections to public water supply systems.
Residences addressed by these actions include all residences on
Kirk Road. The work completed under this Removal Action is
considered to be Operable Unit Two (OU-2).
A Focused RI was initiated in October 1993 to further investigate
the nature and extent of contaminated groundwater attributable to
Areas A, B, and C. In addition, the Focused RI initiated the
investigation of groundwater in the vicinity of the main building
complex at the base (identified as Area D).
Investigative work addressing Area C under the Focused RI has
been completed. The results of this work are summarized in an RI
Report for OU-3 dated August 1994, where OU-3 has been defined as
contaminated groundwater attributable to Area C.
In August 1994, the Navy also released a Focused Feasibility
Study (FFS) Report for OU-3 at the Site. The FFS for OU-3
developed several remedial alternatives for addressing
contaminated groundwater attributable to Area C.
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III. HIGHLIGHTS OF COMMUNITY PARTICIPATION
Since 1988, the plans and results of CERCLA investigations and
actions have been presented to a Technical Review Committee (TRC)
for the Site. The TRC includes representatives of the Bucks
County Health Department, Warminster Township, the Warminster
Township Municipal Authority, Upper Southampton Township, the
Upper Southampton Water and Sewer Authority, Northampton Township
and the Northampton Municipal Authority. Beginning in December,
1993, the TRC became the Restoration Advisory Board (RAB). In
accordance with Sections 113 and 117 of CERCLA, 42 U.S.C.
Sections 9613 and 9617, the Navy, in conjunction with EPA, issued
a Proposed Plan in August 1994, presenting the preferred remedy
for OU-3. The Proposed Plan and RI and FFS reports for OU-3 were
among those documents included in the Administrative Record. The
Administrative Record is available for review by the public at
the following information repositories:
NAWC Public Works Environment Staff Office
Jacksonville Road (Building 2)
Warminster, Pennsylvania 18974
Bucks County Library
150 South Pine Street
Doylestown, Pennsylvania 18901
An announcement of the public meeting, the comment period, and
the availability of the Administrative Record for the preferred
remedy for OU-3 was published in the Philadelphia Inquirer,
Intelligencer. Public Spirit, and Courier Times on September 1
and 2, 1994. Additionally, the Proposed Plan and the Notice of
Availability were mailed to local municipal and government
agencies in the vicinity of the Site.
The public comment period for the Proposed Plan was from
September 1, 1994 to September 30, 1994. A public meeting was
held at McDonald Elementary School, Street Road, Warminster,
Pennsylvania on September 8, 1994 to present the RI, FFS and
Proposed Plan, address concerns, and accept both oral and written
comments.
A transcript of the meeting was maintained in accordance with
Section 117(a)(2) of CERCLA, 42 U.S.C. § 9617(a)(2). Responses
to significant oral comments during the public meeting are in the
transcript of the meeting, which is now part of the
Administrative Record. Responses to comments received during the
public comment period are included in the Responsiveness Summary
section of this ROD.
This Record of Decision presents the selected remedial action for
OU-3 at the Site chosen in accordance with CERCLA and, to the
extent practicable, the National Contingency Plan (NCP).
All documents considered or relied upon in reaching the remedy
selection decision contained in this ROD are included in the
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Administrative Record for the Site and can be reviewed at the
information repositories.
IV. SCOPE AND ROLE OF THIS REMEDIAL ACTION
Section 300.430(a)(1)(ii)(A) of the NCP, 40 C.F.R. Section
430(a)(1)(ii)(A) provides that CERCLA NPL Sites "should generally
be remediated in operable units when early actions are necessary
or appropriate to achieve significant risk reduction quickly,
when phased analysis or response is necessary or appropriate
given the size or complexity of the Site, or to expedite the
completion of a total cleanup." In the case of NAWC, the Navy
has organized work to date into three operable units. These
operable units (OUs) are as follows:
• OU-1: Contaminated groundwater attributable to Areas A and B
• OU-2: Contaminated off-site private wells
• OU-3: Contaminated groundwater attributable to Area C
The Navy and EPA have already selected an interim remedy for OU-1
in a ROD signed on September 29, 1993, while a removal action for
OU-2 has been selected by EPA in a Removal Action Memorandum
signed on July 14, 1993. The Navy initiated construction of the
remedy for OU-1 in January 1995. The EPA initiated construction
of the removal action for OU-2 in June 1994 and completed
construction of this removal action in December 1994.
This ROD selects a remedy for OU-3, contaminated groundwater
attributable to Area C at the Site. This groundwater presents an
unacceptable threat to human health and sufficient information is
available to select a remedy at this time. The objective of the
remedy for OU-3 is to restore contaminated groundwater
attributable to Area C to a level consistent with Federal and
State Applicable or Relevant and Appropriate Requirements
(ARARs), including drinking water standards, and to a level that
is protective of human health and the environment.
Other media associated with the Site, including disposed wastes,
soils, other groundwater, surface water and sediment, will be
further investigated under the Phase III RI. Additional remedial
actions will be proposed and selected as soon as adequate
information exists to support the selection of a remedy for a
particular medium or group of media. Any such medium (or group
of media) will also be designated as an operable unit by the Navy
and EPA.
V.
Summarized below are the primary findings of the RI with regard
to contaminated groundwater attributable to Area C.
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A. SITE CHARACTERISTICS
1. Soils and Geology
The Site is located in the Piedmont Physiographic Province,
Triassic Lowlands Section, of southeastern Pennsylvania. The
land forms have been modified by erosion to form moderate slopes
and gently rounded hills with a dendritic drainage pattern.
Soils observed within Area C during RI work have ranged from 2 to
15 feet in thickness. Soil types observed included orange-red,
brown and maroon-red mixtures of silt, clay and sand, with finer-
grained soils dominant. The U.S Soil Conservation Service (SCS)
has mapped the soils at site 4 as Duncannon silt loam and
Chalfont silt loam (USDA, 1975). The Duncannon silt loam is
reported to have moderate permeability, and the Chalfont silt
loam is described as having slow permeability. The SCS has
mapped the soil at site 8 as Urban Land - Landsdale Complex,
indicating that these soils were reworked from their natural
state.
The soils at Area C lie over highly weathered bedrock which
starts at 5 to 15 feet in depth. The weathered bedrock gradually
grades into competent bedrock. The surface of the competent
bedrock has a northerly slope across Area C. A minor trough in
the bedrock surface is located between sites 4 and 8. This
trough corresponds to a subdued topographic low which extends off
of NAWC property to the north to the small stream that drains
Area C.
The bedrock belongs to the late Triassic age middle arkose member
of the Stockton Formation. The Stockton Formation underlying
Area C consists of alternating lithologic units of predominantly
gray and brown, fine-grained arkosic sandstone and red-brown
siltstone/mudstone. Individual beds or defined sequences of rock
units of predominantly one lithologic type range from a few feet
to approximately 50 feet in thickness across the area. Major
lithologic units can be traced over significant portions of Area
C, although the thinner beds within a unit are often difficult to
correlate and may pinch out over distances of several hundred
feet.
Within Area C, a bedrock strike of north 70 degrees east and a
dip of 9 degrees to the northwest have been measured based on
correlations between geophysical logs from well borings. This
strike and dip matches up well with regional information
regarding the bedrock structure. The direction of slope of the
ground surface across Area C generally mimics the direction of
dip of the underlying bedrock; however, the beds dip more steeply
than the ground surface. Based on projections made using the
measured bedrock strike and dip, the lithologic units encountered
at depth within the northern portion of Area C outcrop in or
adjacent to the southern, topographically higher part of Area C.
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In particular, some of the deeper units encountered outcrop along
the runway area at the top of a hill south of Area C.
Fractures have been encountered at various depths in well borings
within Area C. Both the coarser-grained sandstone units and the
fine grained siltstones/mudstones were fractured to varying
degrees. No generalizations regarding the frequency of
fracturing relative to rock type have been identified, however
the fractures in the sandstones generally were more likely to
produce significant quantities of water than the siltstone/
mudstone fractures. Both cross-cutting fractures and bedding
plane fractures were identified through interpretations of
drilling and geophysical logs, and borehole camera tapes.
No direct observations of fracture orientations have been made
due to the absence of any outcrops in the area; however, it is
typical for well developed, systematic joint sets to occur within
lithologic units along orientations parallel and perpendicular to
bedrock strike, and of 45 to 60 degrees from bedrock strike.
2. Hydrogeology
The Stockton Formation forms a multi-aquifer system of relatively
discrete water-bearing zones separated by thicker, less permeable
zones. Transmissivity and groundwater movement within water-
bearing zones are greater parallel to bedding than across
bedding. Vertical or nearly vertical fractures cutting across
bedding and the weathering of various beds are expected to permit
varying degrees of leakage between the main water-bearing zones,
particularly near the surface. Groundwater in the Stockton
Formation occurs locally under both confined and unconfined
conditions.
Within water-bearing zones in the fine- and medium-grained
sandstone of the Stockton Formation, groundwater is transmitted
through primary intergranular porosity, as well as along
fractures, joints, and bedding planes (secondary porosity). The
shale and siltstone beds are commonly too fine-grained to
transmit large amounts of groundwater through primary porosity,
and fractures and joints are typically not well developed in
these fine-grained beds. Consequently, the shale and siltstone
beds often act as confining layers to groundwater. Fracture
permeability is generally better developed in the sandstone
layers compared to the shale and siltstone layers of the
formation. This, along with greater primary permeability, allows
the sandstone layers to function as the most productive water-
bearing units of the Stockton Formation.
Groundwater in Area C occurs primarily with the bedrock (Stockton
Formation) underlying the Site. Groundwater occurrence and
movement through the Stockton Formation is primarily through
secondary porosity (fractures) that exists within the rock mass.
These fractures include both bedding plane partings and fractures
that extend through individual rock units. In addition to the
13
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secondary porosity, there is likely some minor primary porosity,
especially in the sandstone units, that contributes to
groundwater occurrence and movement. In general, the coarser-
grained (sandstone) units were observed to yield water more so
than the finer-grained (siltstone and shale) units, although
significant water-yielding fractures were encountered in all rock
types.
Minor quantities of groundwater are also encountered within the
lower portions of the thin veneer of soils and weathered rock
overlying competent bedrock. The observed saturated thickness of
the soils and weathered rock (i.e., overburden) within Area C
ranged from approximately 3 to 12 feet. Due to the overall
clayey nature and resulting low permeability of the overburden,
groundwater movement through the overburden is likely to be
restricted in comparison to the migration through the underlying
fractures in bedrock. Limited hydraulic conductivity testing of
the overburden has resulted in hydraulic conductivity estimates
ranging from 0.2 to 2.3 ft/day, and yields from overburden
monitoring wells are typically less than 1 gallon per minute
(gpm).
3. Hydrology
An unnamed tributary of Little Neshaminy Creek is located north
of site 4, in Munro Park. This stream originates at the base of
the storm sewer drain east of site 4 and runs east to west
through Munro Park immediately north of residences along Kirk
Road.
During base flow conditions, this stream appears heavily silted
and has an estimated maximum flow rate of seven to 10 gpm. The
uppermost part of this stream is small and intermittent and
during dry periods, water in the stream tends to be limited to
pool areas. The stream channel is well developed despite the low
and intermittent flow rates. Channel width is 3 to 5 feet and
channel depth is 1 to 2 feet. Sediments in the stream are
primarily sands and cobbles with some silts.
Site 8 is drained by a concrete swale that discharges directly to
an intermittent stream through a culvert beneath Kirk Road north
of site 8. The intermittent stream is channelized and flows to
the north for approximately 750 feet until it joins the unnamed
tributary of Little Neshaminy Creek that originates near site 4.
In addition, a groundwater seep on the western perimeter of site
4 drains to a second culvert under Kirk Road, which also
discharges to the same unnamed tributary.
4. Meteorology
The climate of the area is humid continental and is modified by
the Atlantic Ocean. Temperatures average 76 °F (24.4°C) in July
and 32°F (0°C) in January. The average daily temperature for the
14
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NAWC location is 53.3T (11.8°C). Precipitation averages 42.5
inches per year (106.25 cm per year), and snowfall averages 22
inches per year (55 cm per year). The distribution of
precipitation is fairly even throughout the year. The relative
humidity for the Site averages 70 percent. The mean wind speed
for this area is 9.6 mph, with a prevailing direction of west-
southwest.
5. Ecology
Open land, woodland, and wetland habitats are all found within or
near Area C. These habitats include mowed fields and lawns,
nonforested overgrown land, wooded areas, forested wetlands,
scrub/shrub wetlands, and streams with associated riparian areas.
There are no known threatened or endangered species on or near
Area C; however, some such species could traverse Area C.
Mourning doves, pheasants, and various songbirds such as
sparrows, red-winged black birds, gold finches, cardinals, blue
jays, and robins are present throughout the Site. Canada geese
and ducks have been observed in the streams south of Area B and
north of Area A. Snakes, leopard frogs, and muskrats have also
been observed in or near these streams. Snails, earthworms,
amphipods, and larval insects have also been observed. Small
fish or minnows tentatively identified as creek chubs are present
in each of the streams from which surface water and sediment
samples were obtained. White-tailed deer, groundhogs, rabbits,
and squirrels are common on NAWC property. Raccoon tracks have
been observed in several adjacent streams.
A Wetlands Assessment for NAWC (NUS, 1994) has identified off-
base areas receiving surface drainage from Area C as wetlands.
The discussion above is based on available information. A
complete ecological assessment shall be completed for Area C (and
the entire Site) as part of the RI for the Site.
6. Groundwater Use
Groundwater is the primary source of residential, industrial and
commercial water supplies in the immediate vicinity of the Site.
The groundwater is provided either through individual, privately
owned wells or by larger supply systems which have their own
wells. The location of former private wells in the immediate
vicinity of Area C is provided in Figure 4. (All of these
private wells have been connected to a public water system as
part of a removal action addressing OU-2.) There are
approximately thirty-five (35) domestic wells and one municipal
water supply well within 3200 feet of Area C at this time.
15
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B. NATURE AND EXTENT OF CONTAMINATION
The findings of the RI with respect to contaminated groundwater
attributable to Area C are provided in detail within the RI
Report for OU-3. A summary of the major findings for OU-3 are
presented below.
Monitoring Wells
All monitoring wells in the vicinity of Area C are depicted in
Figure 4. These wells monitor groundwater from 7 to 172 feet in
depth and are located both on and off NAWC property.
Groundwater level measurements indicated that groundwater in
overburden and shallow bedrock is flowing north from Area C to
offbase areas along and north of Kirk Road.
Table 2 summarizes the analytical results for samples collected
from these wells from January 1994 through May 1994.
Tetrachloroethylene (PCE) and acetone were the two organic
contaminants detected at significant concentrations and
frequency. A level of 2 micrograms per liter (/xg/1) of PCE was
detected in monitoring well HN-25I, which is located
approximately 500 feet from the NAWC property boundary.
Samples were also collected to identify both total (unfiltered)
and dissolved (filtered) concentration of inorganics. Arsenic,
beryllium and thallium were all detected at elevated levels.
However only thallium appeared to be at a concentration above
natural, background levels.
2. Offsite Private Wells
As part of the RI for OU-3, the private residential wells along
Kirk Road and the NAWC property boundary were sampled from May
1993 through July 1994. The wells sampled include those noted
as residential wells RI through R9 in Figure 4. Seven of these
wells contained PCE at levels over 5 /xg/1, the Maximum
Contaminant Level for this compound in public water supplies.
Based on groundwater flow measurements, these levels appear to be
attributable to Area C. However, based on available data, the
specific location of the release within Area C is unknown. As
previously stated, all homes on Kirk Road are now connected to a
public water supply system.
16
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SOURCE: ADAPTED FROM HALLIBURTON NUS Rl REPORT FOR OU-3 (AUGUST 199WIGURE 2-
MONITORING WELL1 '
PRODUCTION WELL .. '
SOIL BORING
• RESIDENTIAL WELL; •
408 ' ' -800
- FIGURE 4
AREA C - WELL LOCATIONS
NAWC WARMINSTER. PA
-------
3. Surface Water
The quality of surface water being discharged from Area C has not
been fully characterized at this time. However, preliminary data
(see Draft Phase II RI Report, NUS (1992)) suggests there are no
impacts of concern on the tributary of Little Neshaminy Creek.
The Phase III RI, scheduled to begin in 1995, will complete the
investigation of surface water which may be impacted by Area C.
Any remediation determined necessary will be addressed in a
future OU.
18
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TABLE 2
FREQUENCY OF OCCURRENCE AND DISTRIBUTION
POSITIVELY DETECTED SUBSTANCES - AREA C MONITORING WELLS
NAWC, WARMINSTER, PENNSYLVANIA
Ad
Au
Chemical
ORGANICS
Acetone
Toluene
Tet rachl oroethene
Diethylphthalate
Di-n-butylphyhalate
Endosulfan II
TOTAL METALS
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Macrnesium
Manqanese
Mercury
Potassium
Sodium
Thallium
Vanadium
Zinc
Frequency
of
Detection
9/24
2/34
10/34
1/22
4/22
1/22
30/34
1/34
17/34
34/34
4/34
8/34
34/34
4/34
2/34
21/34
23/34
12/34
34/34
31/34
5/34
32/34
34/34
1/34
2/34
13/34
Range of
Positive
Results
(MQ/L)
8-74
1-2
1-29
1
1-2
0.24
45.9-20,900
47.3
3.0-13.6
40.8-593
1.1-1.5
3.2-4.4
11,900-67,700
8.0-15.5
4.1-16.5
6.6-79.2
107-35,200
1.0-11.9
4,710-33,700
13.5-1,840
0.13-0.22
865-2,360
5,370-35,200
5.1
20.9-21.7
8.4-225
Location
of
Maximum
HN23-S
DG-22
HN24-S
HN24-I
HN25-S,!
HN28-S
HN29-X
HN29-I
HN28-S
DG-4
BG-6/HN25-S
HN25-S
DG-15
HN29-X
HN23-X
HN29-X
DG-4
BG-6
HN29-X
HN29-X
HN25-S
BG-2
HN24-I
HN29-I
NH29-X
DG-6
opted from - Halliburton NUS Corporation Remedial Investigation Report for Operable Unit 3,
gust 1994
19
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TABLE 2 (Continued)
FREQUENCY OF OCCURRENCE AND DISTRIBUTION
POSITIVELY DETECTED SUBSTANCES - AREA C MONITORING WELLS
NAWC, WARMINSTER, PENNSYLVANIA
Ad
Au
Chemical
DISSOLVED METALS
Aluminum
Antimony
Arsenic
Barium
Cadmium
Calcium
Copper
Cobalt
Iron
Lead
Magnesium
Manganese
Mercury
Potassium
Sodium
Vanadium
Zinc
Frequency
of
Detection
1/34
12/34
4/34
34/34
2/34
34/34
11/34
10/24
13/34
2/34
34/34
28/34
1/34
31/34
34/34
2/34
23/34
Range
of Positive
Results (/xg/L)
372
35.2-64.7
3.7-10.9
45.7-552
4.3-5.5
9,070-64,000
6.1-17.3
2-118
5.6-18,200
1.7-15.9
2,790-28,000
1.4-1,380
0.33
747-2220
5,380-34,600
3.6-3.8
3.5-47.0
Location
of
Maximum
BG-2
HN26-I
HN28-S
DG-4
HN25-S
DG-15
HN34-S
22.8
DG-4
MW01
HN29-X
DG-15
BG-6
BG-2
HN24-I
HN26-I
DG-6
opted from - Halliburton NUS Corporation Remedial Investigation Report for Operable Unit 3,
gust 1994
20
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VI. SUMMARY OF SITE RISKS
This section summarizes available assessments of risk posed by
contaminated groundwater attributable to Area C to human health
and the environment. These assessments are based on RI
information generated to date. The risk assessment process is
designed to be conservative. The methods used for the risk
assessment are consistent with current U.S. EPA guidance as
outlined in:
Risk Assessment Guidance for Superfund - Volume 1 -
Human Health Evaluation Manual (Part A) .
U.S. EPA, December 1989.
Risk Assessment Guidance for Superfund - Volume 1 -
Human Health Evaluation Manual (Part A) .
Supplemental Guidance - Standard Default Exposure
Factors, U.S. EPA, March 25, 1991.
Dermal Exposure Assessment: Principles and
Applications.
U.S. EPA, January 1992.
Due to a removal action by EPA (under OU-2), residents are not
exposed to contaminated groundwater apparently attributable to -.
Area C at this time. As a result, this risk assessment assesses
risks to potential future users of contaminated groundwater
attributable to Area C.
A. HUMAN HEALTH
As part of the RI, a risk assessment was conducted with available
data to estimate the potential risks to human health posed by the
contaminated groundwater attributable to Area C. Since there is
no current exposure to contaminated groundwater attributable to
Area C, only potential exposure of residents to this contaminated
groundwater is evaluated below..
The following exposure pathways were determined to present a
potential risk to human health:
• Ingestion of the groundwater as a drinking water
source.
• Dermal exposure to the groundwater (e.g., through
handwashing, showering, and bathing).
• Inhalation of contaminants in groundwater (i.e.,
volatile compounds emitted during showering).
Potential human health risks were categorized as carcinogenic or
noncarcinogenic. A carcinogenic risk increase from exposure
should fall within a range of 1 X 10"6 (an increase of one case
of cancer for one million people exposed) to 1 X 10~4 (one
additional case per 10,000 people exposed). Noncarcinogenic
21
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risks were estimated utilizing Hazard Indices (HI), where an HI
exceeding one is considered an unacceptable health risk. Federal
Maximum Contaminant Levels (MCLs) for public drinking water
supplies were also utilized to assess potential risks posed by
exposure to groundwater.
Carcinogenic and noncarcinogenic risks posed by exposure to
contaminated groundwater attributable to Area C were estimated
for adult residents and child residents. To assess these
carcinogenic and noncarcinogenic risks, primary organic and
inorganic contaminants of concern were selected based on their
occurrence and distribution, mobility, persistence and toxicity.
An important component of the risk assessment process is the
relationship between the intake of a contaminant and the
potential for adverse health effects resulting from that
exposure. Dose-response relationships provide a means by which
potential human health impacts may be quantified. The dose-
response relationships for carcinogenic and noncarcinogenic
effects are described as reference doses (RfDs) and cancer slope
factors (CSFs), respectively. The RfD is developed by EPA for
chronic and/or subchronic human exposure to hazardous chemicals
and is usually expressed as a dose per unit body weight per unit
time (mg/kg/day). CSFs are applicable for estimating the
lifetime probability of developing cancer as a result of exposure
to known or potential carcinogens, are generally reported in
units of I/(mg/kg/day), and are derived through an assumed low-
dosage linear relationship of extrapolation from high to low
dose-responses determined from animal studies. RfDs and CSFs
used to calculate estimated risks in this case are identified in
the Rl.
The RI Report for OU-3 contains a detailed risk assessment for
contaminated groundwater attributable to Area C at the Site in
overburden and shallow bedrock. The assumptions utilized in
conducting this assessment are identified therein. These
assumptions include exposure input parameters which estimate the
exposure of an individual to a contaminant over time.
In conducting this risk assessment, it is acknowledged that there
are uncertainties associated with the evaluation of chemical
toxicity and potential exposures. For example, uncertainties
arise in the derivation of RfDs and CSFs and estimation of
exposure point concentrations.
Summarized below are the results of the risk assessment for
contaminated groundwater attributable to Area C.
1. Area C
Cumulative, total estimated risks to human health due to
potential exposure to noncarcinogenic and carcinogenic
groundwater contaminants attributable to Area C at the Site are
summarized in Tables 3 and 4, respectively.
22
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The risk assessment for contaminated groundwater attributable to
Area C (OU-3) found the carcinogenic risk for hypothetical
exposure to this groundwater was an estimated 1.2 X 10"4. The
carcinogenic risk associated with PCE, the only organic
contaminant contributing to this risk, was 3.1 X 10"6. The
carcinogenic risks for arsenic and beryllium were calculated at
8.7 X 10"5 and 3.3 X 10"5, respectively. However as previously
noted in Section V.B.I, the detected levels of arsenic and
beryllium appear to be attributable to natural, geologic
conditions. While thallium and acetone were both detected at
levels above background, there was no carcinogenic risk
associated with these substances.
The total Hazard Index and Hazard Indices for each substance were
calculated using unfiltered monitoring well sample results.
Using this data, the total Hazard Index was determined to be well
in excess of one, primarily due to elevated levels of manganese,
and to a lesser extent, antimony and thallium. However, it
appears that manganese and antimony are naturally occurring and
at background concentrations. No organic compounds were
significant contributors to the Hazard Index. As a result
thallium is the only contaminant attributable to Area C that has
been determined to present an unacceptable non-carcinogenic risk.
The overall carcinogenic risk attributable to groundwater
contaminated by Area C could potentially be considered
acceptable. However, PCE has been detected in residential wells
formerly used for drinking water and bathing purposes at levels
ranging up to 31 jug/I, in excess of the Maximum Contaminant Level
MCL) of 5 /xg/1 for PCE. Based on this information and the
conclusions of the risk assessment described above, PCE and
thallium are the groundwater contaminants attributable to Area C
that present a threat to human health.
Actual or threatened releases of hazardous substances from NAWC,
if not addressed by a response action, may present potential or
actual threats to public health, welfare, or the environment.
23
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TABLE 3
SUMMARY OF POTENTIAL NONCARCINOGENIC RISKS
AREA C GROUNDWATER
Exposure Route
Ingestion
Dermal Cont
Inhalation
Total Risk
Receptor
Adult Resident
11.6
NA
NA
11.6
Child Resident
27.0
4.9E-3
NA
27.0
TABLE 4
SUMMARY OF POTENTIAL CARCINOGENIC RISKS
AREA C GROUNDWATER
Exposure Route
Ingestion
Dermal Cont
Inhalation
Total Risk
Receptor
Adult Resident
1.2E-4
NA
4.4E-8
1.2E-4
Child Resident
5.7E-5
1.9E-7
NA
5.7E-5
Adopted from Halliburton NUS Corporation, Phase II Remedial Investigation Report, OU-3 August 199
24
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B. ENVIRONMENT
Limited surface water investigations conducted during the Phase II
RI suggest that contaminated groundwater attributable to Area C is
not impacting the quality of an unnamed tributary of Little
Neshaminy Creek. However, the investigations to date are
incomplete. Additional investigations shall be performed as needed
to determine whether contaminated groundwater attributable to Area
C presents an unacceptable risk to human health and the environment
due to impacts on surface water.
C. CONCLUSIONS
Contaminated groundwater attributable to Area C at the Site has
been determined to present an unacceptable risk to human health.
Actual 'Or threatened releases of hazardous substances from the
Site, if not addressed by implementing the remedial action selected
in this ROD, may present an imminent and substantial endangerment
to public health or welfare, or the environment.
VII. DESCRIPTION OF ALTERNATIVES
An FFS was conducted by the Navy to identify and evaluate remedial
alternatives for contaminated groundwater attributable to Area C.
Applicable engineering technologies for achieving the remedy
objective to eliminate unacceptable risk associated with exposure
(or potential exposure) to groundwater contaminants attributable to
Area C were initially screened in the FFS based on effectiveness,
implementability, and cost. The alternatives meeting these
criteria were then evaluated and compared to nine criteria required
by CERCLA and the NCP. Three remedial alternatives were developed
for OU-3. Costs and implementation times were estimated for each
alternative described in this section.
A. ALTERNATIVE 1: NO ACTION WITH GROUNDWATER MONITORING
The NCP requires that the "no action" alternative be evaluated at
every Site to establish a baseline for comparison with action
alternatives. Under this alternative, no remedial action would be
undertaken to address contaminated groundwater attributable to Area
C. Monitoring of groundwater in overburden and shallow bedrock
aquifers would be conducted for 30 years.
For cost estimation purposes, an estimated total of 16 wells would
be sampled quarterly for an estimated 30-year period. The
frequency of sampling may be reduced after a reliable trend has
been established. Because this alternative would result in
contaminated groundwater remaining at the facility, five-year
reviews would be required to monitor the effectiveness of this
alternative. The present worth of this alternative is estimated to
be $1,853,000 over a 30-year period, with a capital cost of $69,696
and an annual operation and maintenance (O&M) cost of $116,000.
25
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B. ALTERNATIVE 2: GROUNDWATER EXTRACTION, TREATMENT AT AREA C, AND
DISCHARGE TO SURFACE WATER IN THE VICINITY OF AREA C
Under this alternative, contaminated groundwater attributable to
Area C at the Site would be extracted using a series of extraction
wells. The extraction well network would be located as necessary
to maximize the effectiveness of the system. The extracted
groundwater would be pumped to an on-site treatment system
constructed specifically to treat groundwater and located within
Area C. Water treatment would include precipitation, filtration,
carbon adsorption, and/or other treatment methods as necessary to
meet effluent limits consistent with National Pollution Discharge
Elimination System (NPDES) requirements under the Federal Clean
Water Act and Pennsylvania Clean Streams Law. Organic and
inorganic treatment residuals would be disposed offsite as required
by treatment, storage and disposal regulations under the Federal
Resource Conservation and Recovery Act (RCRA), including Land
Disposal Restrictions (LDRs) under 40 C.F.R. Part 268, Pennsylvania
Hazardous Waste Management (25 Pa. Code, Article VII) and Residual
Waste Regulation (25 Pa. Code, Article IX) . (A detailed inventory
of all applicable or relevant and appropriate requirements (ARARs)
for the alternatives being evaluated is provided in Section X.B.)
The treated water would be discharged to an unnamed tributary of
Little Neshaminy Creek located immediately north of Area C and Kirk
Road.
Concurrent with the design, construction, and operation of the
extraction well network and treatment system, monitoring and
investigations would be conducted both on and off NAWC property as
necessary to fully identify the nature and extent of groundwater
contamination attributable to Area C and to assess the
effectiveness of the system. Monitoring of groundwater associated
with Area C would be conducted throughout the implementation of the
remedy. The extraction well network and treatment system would be
modified as necessary based on the results of the monitoring and
investigations.
To estimate the cost of this alternative, the following assumptions
were made: a series of 8 extraction wells would be installed; a
total flow of 52 gallons per minute (gpm) would be pumped to an
adjacent treatment plant within Area C; and on-site and off-site
wells would be constructed and monitored on a quarterly basis for
an estimated 30 years. (Additional costs would be incurred if
additional extraction wells were installed and additional
groundwater were extracted and treated.) Based on these
assumptions, the present worth of this alternative was estimated at
$5,075,000, with a capital cost of $1,545,393 and an operation and
maintenance cost of $229,629 annually. This alternative could be
constructed in 12 months or less.
26
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ALTERNATIVE 3: GROUNDWATER EXTRACTION, TREATMENT AT AREA C OR AREA
A, AND DISCHARGE TO SURFACE WATER AT AREA A SYSTEM OUTFALL
Under this alternative, contaminated groundwater attributable to
Area C at the Site would be extracted using a series of extraction
wells. The extraction well network would be located as necessary
to maximize the effectiveness of the system. The extracted
groundwater would be pumped to an on-site treatment system at Area
C or Area A. If pumped to Area A, the extracted groundwater would
be treated either by the treatment system constructed within Area
A pursuant to the ROD for OU-1 or by an additional and separate
system constructed within Area A pursuant to this ROD. If such
treatment is conducted by a separate additional system .within Area
A or a system within Area C, it is projected to include, at a
minimum, precipitation, filtration and carbon adsorption. If
treated by the treatment system constructed within Area A pursuant
to the ROD for OU-1, water treatment would include air stripping.
Organic and inorganic treatment residuals would be disposed offsite
and handled as required by treatment, storage and disposal
regulations of RCRA, including LDRs under 40 C.F.R. Part 268, 25
Pa. Code, Article VII and 25 Pa. Code, Article IX. (A detailed
inventory of all applicable or relevant and appropriate
requirements (ARARs) for the alternatives being evaluated is
provided in Section X.B.)
Regardless of the location of the treatment system, the treated
water would be discharged to the outfall of the treatment system
constructed within Area A pursuant to the ROD for OU-1. (Treated
water from a treatment system at Area C would be conveyed to Area
A for discharge to this outfall.)
Concurrent with the design, construction, and operation of the
extraction well network and treatment system, monitoring and
investigations would be conducted both on and off NAWC property as
necessary to fully identify the nature and extent of groundwater
contamination attributable to Area C and to assess the
effectiveness of the system. Monitoring of groundwater associated
with Area C would be conducted throughout the implementation of the
remedy. The extraction well network and treatment system would be
modified as necessary based on the results of the monitoring and
investigations.
The present worth of this alternative was estimated to range from
$4,944,000 to $5,224,000 with a capital cost ranging from
$1,186,852 to $1,839,690 and an operation and maintenance cost
ranging from $214,729 to $244,444 annually. This alternative
could be constructed in 12 months or less.
VIII. COMPARATIVE ANALYSIS OF ALTERNATIVES
To help select a remedial action, CERCLA and the NCP require that
remedial alternatives be evaluated under the nine criteria
discussed below.
27
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A. OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
Alternatives 2 and 3 would protect both human health and the
environment by capturing and treating contaminated groundwater
attributable to Area C at the Site and restoring the quality of the
aquifer to levels protective of human health and the environment.
Any additional monitoring necessary to determine the full nature
and extent of groundwater contamination attributable to Area C
would be conducted concurrently with the design, construction, and
operation of the groundwater extraction and treatment system.
Alternative 1 would not restore the quality of contaminated
groundwater attributable to Area C to levels protective of human
health and the environment.
B. COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS (ARARs)
ARARs for both Alternatives 2 and 3 are identified in detail within
Sections IX and X. Based on available information, it is unknown
whether Alternative 2 could meet all ARARs (see Section VIII.F).
Alternative 3 is expected to meet all ARARs. Since no remedial
action would be taken under Alternative 1, there are no ARARs
associated with remedial activity under this alternative.
C. LONG-TERM EFFECTIVENESS AND PERMANENCE
Alternatives 2 and 3 provide a permanent remedy and both would be
effective over the long term in addressing groundwater
contamination at Area C. Both alternatives require groundwater
monitoring to evaluate their effectiveness. Operation and
maintenance of the treatment plant and monitoring of the treated
discharges would be required for both alternatives.
Alternatives 2 and 3 would also be effective over the long-term for
remediating all contaminated groundwater attributable to Area C at
the Site by preserving the capacity of the OU-1 treatment system
currently being constructed within Area A to the extent necessary.
Alternative 2 would do so by establishing a separate treatment
facility within Area C; Alternative 3 would provide for a separate
treatment system within Area A for treating groundwater from Area
C, if appropriate.
Alternative 1 would not provide a permanent remedy and would not be
effective over the long term.
D. REDUCTION OF TOXICITY, MOBILITY, OR VOLUME
Alternatives 2 and 3 would all reduce the toxicity, mobility and
volume of groundwater contaminants by treatment. The treatment
systems for these alternatives would generate residuals that would
require further treatment or disposal.
28
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Alternative 1 would not use treatment to reduce the toxicity,
mobility, or volume of groundwater contaminants.
E. SHORT-TERM EFFECTIVENESS
There would be no additional risks to the public or the environment
under Alternatives 2 and 3. In the case of these alternatives,
workers would be required to wear protective equipment during
activities where they may be exposed to hazardous materials.
Under Alternative 1, groundwater contaminants would continue to
present potential unacceptable risks to human health.
F. IMPLEMENTABILITY
For Alternatives 2 and 3, the remedial technologies and process
options proposed for groundwater extraction and treatment are all
demonstrated and commercially available.
Alternative 2 includes the discharge of treated groundwater to the
unnamed tributary of Little Neshaminy Creek north of Kirk Road.
Due to the low flow rate of this tributary, it is unknown whether
this discharge could meet NPDES requirements to be developed by
Commonwealth of Pennsylvania.
Under Alternative 3, available information indicates that extracted
groundwater could be treated to meet the NPDES requirements of
concern.
No remedial action is included under Alternative 1.
G. COST
The present worth of Alternative 1 is $1,853,000. The present
worth of Alternative 2 is $5,075,000. The present worth of
Alternative 3 ranges from $4,944,000 to $5,224,000.
H. STATE ACCEPTANCE
The Commonwealth of Pennsylvania concurs with the selected remedy
for OU-3 at this Site, Alternative 3 with treatment at Area A (see
Section IX.).
I. COMMUNITY ACCEPTANCE
A public meeting on the Proposed Plan was held on September 8, 1994
in Warminster, Pennsylvania. Comments received orally at the
public meeting and in writing during the public comment period are
referenced in the Responsiveness Summary (Section VIII of this
ROD) . Comments from the local community generally reflected a
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preference for Alternative 3: Treatment at Area A or Area C, and
Discharge to Surface Water at Area A System Outfall.
One comment suggested the location of the treatment plant under
this alternative be limited to Area A.
IX. SELECTED REMEDY
A. GENERAL DESCRIPTION
The Navy and EPA have selected the following remedy for OU-3:
Groundwater Extraction. Treatment at Area A. and Discharge to
Surface Water at Area A System Outfall, as the remedy for
contaminated groundwater attributable to Area C. The selected
remedy is as described under Alternative 3 in Section VII with the
following modification: the location of the treatment system shall
be limited to Area A.
The selected remedy is believed to provide the best balance of
trade-offs among the alternatives with respect to the response
criteria. Based on available information, the Navy and EPA believe
the selected remedy would be cost effective and would comply with
applicable or relevant and appropriate requirements.
The selected remedy for OU-3 includes the following major
components:
• Installation, operation and maintenance of groundwater
extraction wells to recapture and treat contaminated
groundwater attributable to Area C at the Site
• Installation, operation and maintenance of an onsite
groundwater treatment system within Area A which includes
precipitation, filtration, air stripping, carbon
adsorption, and/or other necessary means of treatment
• Periodic sampling of treated water to ensure the
effectiveness of the treatment system
• Installation, operation and maintenance of a vapor phase
carbon adsorption unit (if such a unit is necessary to
control air emissions)
• Discharge of treated water to the outfall of the Area A
plant which is being constructed pursuant to the OU-1 ROD
• Offsite treatment and/or disposal of solid residuals
generated during water treatment and control of air
emissions (if necessary)
• Periodic monitoring of groundwater in monitoring wells
and residential wells
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• Installation and periodic sampling of observation wells
to ensure effectiveness of the groundwater extraction
wells
• Periodic evaluation of hydroge'ologic data to ensure the
effectiveness of the groundwater extraction system
• Modification of the groundwater extraction well system
and/or groundwater treatment system as necessary based on
periodic evaluations
The FFS estimated the present worth of this remedy from $4,944,000
to $5,224,000 over a 30-year period, with a capital cost of between
$1,186,852 and $1,839,690 and an annual O&M cost of between
$214,729 and $244,444.
Performance standards associated with the components above are
described below.
B. PERFORMANCE STANDARDS
1. Groundwater Extraction Wells
The number, location and design of the extraction wells shall be
sufficient to (1) prevent further migration of the contaminated
groundwater attributable, to Area C and (2) capture all
contaminated groundwater attributable to Area C. Capture of the
contaminated groundwater will be ensured by maintaining inward and
upward gradients across the lateral and vertical boundaries of the
contaminant plume.
Observation wells will be located and constructed to gather data to
confirm these gradients and to characterize changes in contaminant
concentrations within the plume and to ensure that previously
uncontaminated portions of the aquifer are not adversely impacted
by the extraction system.
Groundwater monitoring (see Section IX.B.6, below) and groundwater
investigations shall be conducted as part of the Remedial Design
and/or Remedial Action for OU-3 both on and off NAWC property, as
necessary, to fully identify the nature and extent of groundwater
contamination attributable to Area C and to assess the
effectiveness of the system. Monitoring of groundwater associated
with Area C shall be conducted during the entire course of the
implementation of the remedy. The extraction well network and
treatment system shall be modified as necessary based on the
results of the monitoring and investigations.
The groundwater extraction wells shall be operated as necessary to
reduce contaminant concentrations throughout the plume to
Groundwater Cleanup Levels determined pursuant to Section IX.B.2
(see below). Groundwater Cleanup Levels shall be achieved in all
monitoring wells within the plume. These monitoring wells shall be
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installed and monitored per an Operation and Maintenance Plan for
Groundwater Monitoring (see Section IX.B.6, below). The extraction
well system may be shut down when a statistical analysis of
groundwater sample results confirms that Groundwater Cleanup Levels
have been attained throughout the plume for twelve consecutive
quarters. If subsequent groundwater monitoring (as described in the
Operation and Maintenance Plan for Groundwater Monitoring) indicate
that contaminant concentrations are once again above Groundwater
Cleanup Levels, the extraction well system shall be restarted and
operated until the Groundwater Cleanup Levels have once more been
attained for twelve consecutive quarters.
2. Groundwater Cleanup Levels
The Groundwater Cleanup Levels for contaminated groundwater shall
be the background concentrations per Pa. Code Sections 264.90-
264.100. The Commonwealth of Pennsylvania also maintains that the
background cleanup standard is found in other legal authorities.
The background concentrations shall be determined by the Navy and
EPA in consultation with PADER during the Remedial Design in
accordance with the procedures for groundwater monitoring outlined
in 25 Pa. Code Section 264.97. Based on available information,
concentrations of PCE and thallium should be reduced to background
levels. Should additional investigations, sampling or groundwater
monitoring (see Section IX.B.6 below) identify any other
groundwater contaminants attributable to Area C which present a
threat to human health and the environment, Groundwater Cleanup
Levels shall also be established for these additional contaminants.
3. Groundwater Treatment System
The extracted groundwater will be pumped to an on-site treatment
system at Area A, where it will be treated either by the treatment
system constructed within Area A pursuant to the ROD for OU-1 or by
an additional and separate system constructed within Area A
pursuant to this ROD. If such treatment is conducted by a separate
additional system within Area A, it is projected to include, at a
minimum, precipitation, filtration and carbon adsorption. If
treated by the treatment system constructed within Area A pursuant
to the ROD for OU-1, water treatment will also include air
stripping. In either case, the treatment system for extracted
groundwater will meet effluent limits developed in accordance with
National Pollution Discharge Elimination System (NPDES)
requirements under the Federal Clean Water Act, NPDES requirements
under the Pennsylvania Clean Streams Law (25 Pa. Code, Chapter 92)
and Pennsylvania Wastewater Treatment Requirements (25 Pa. Code,
Chapter 95). Alternative treatment methods such as ion exchange,
reverse osmosis and UV/oxidation may be used as necessary to meet
the effluent limits. Upon being treated to meet these effluent
limits, the water shall be discharged to an unnamed tributary of
Little Neshaminy Creek through the outfall of the existing NAWC
Wastewater Treatment Plant. (This outfall will also be used to
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discharge treated water from the plant being constructed under OU-
1.)
The treated groundwater shall be monitored as necessary to assure
that prescribed effluent limits are being met prior to discharge.
An Operation and Maintenance plan shall be developed and
implemented to assure the continued effective operation of the
Groundwater Treatment System.
4. Treatment of Air Emissions
Any air emissions from the groundwater treatment system, including
air emissions from an air stripper (if necessary), will meet the
requirements of 25 Pa. Code, Chapter 127, Subchapter A, as well as
the National Emissions Standards for Hazardous Air Pollutants
(NESHAPS) and the National Air Quality Standards for Criteria
Pollutants under the Federal Clean Air Act. EPA Directive 9355.0-
28, which covers emissions from air strippers at CERCLA sites is a
standard to be considered in this case. Vapor-phase carbon
adsorption will be employed as necessary to meet these
requirements.
5. Water and Air Treatment Residuals
Spent carbon from the carbon adsorption unit, spent carbon from the
vapor-phase carbon adsorption unit associated with an air stripper
(if necessary) and sludge generated during the treatment of metals
will be handled in accordance with treatment, storage and disposal
requirements under RCRA, including RCRA Land Disposal Restrictions
(LDRs) in 40 C.F.R. Part 268, Pennsylvania Hazardous Waste
Management Regulations (25 Pa. Code, Article VII) and Residual
Waste Regulations (25 Pa. Code, Article IX).
6. Groundwater Monitoring
An Operation and Maintenance Plan for Groundwater Monitoring for
contaminated groundwater attributable to Area C shall be developed
and implemented. The Plan will be approved by the EPA in
consultation with PADER. Under the Plan, wells shall be monitored
at locations on and off current NAWC property. Monitoring shall
include residential and other privately owned wells as necessary.
Monitoring wells shall be installed off of current NAWC property as
necessary.
In addition, as part of the Remedial Design and/or Remedial Action,
additional groundwater investigations shall be conducted both on
and off NAWC property as necessary to fully identify the nature and
extent of contaminated groundwater attributable to Area C. These
investigations shall include any additional investigations
necessary to confirm that there are no additional contaminants of
concern. The extraction well network and treatment system shall be
modified as necessary based on the results of these investigations.
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7. Worker Safety
All work shall comply with Occupational Safety and Health
Administration (OSHA) standards governing worker safety in 29
C.F.R. Parts 1910, 1926 and 1904.
8. Five Year Reviews
Because contaminated groundwater will likely remain at the facility
after five years, a five-year review will be required. A five-year
review will be conducted within five years of the initiation of the
remedial action and every five years thereafter, as required by
Section 121(c) of CERCLA, 42 U.S.C. Section 9621 (c) , to ensure
that the remedy continues to provide adequate protection of human
health and the environment. A Five-Year Review Work Plan will be
developed and approved by EPA in consultation with PADER.
X. STATUTORY DETERMINATIONS
A. PROTECTION OP HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy is protective of human health and the
environment by capturing and treating contaminated groundwater
attributable to Area C at the Site. The selected remedy provides
that groundwater contaminants attributable to Area C will be
restored to background levels. The selected remedy will not pose
unacceptable short-term risks to human health and the environment
during implementation.
B. COMPLIANCE WITH ARARS
The selected remedy will comply with all applicable or relevant and
appropriate requirements specific to this action. These ARARs
include those identified in Section IX and those listed below:
1. Chemical-Specific ARARs
The groundwater contaminants attributable to Area C which present
a threat to human health and the environment will meet background
levels per 25 Pa. Code Sections 264.90 - 264.100, specifically 25
Pa. Code Sections 264.97(i) and (j) and 264.100(a)(9). The
Commonwealth of Pennsylvania also maintains that the background
cleanup standard is found in other legal authorities. The
background concentrations for contaminated groundwater shall be
established in accordance with the procedures for groundwater
monitoring in 25 Pa. Code Section 264.97, which are relevant and
appropriate for this remedy.
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2. Location-Specific ARARs
The substantive requirements of the Delaware River Basin Commission
(18 C.F.R. Part 430) are applicable. These regulations establish
requirements for the extraction of groundwater within the Delaware
River Basin.
3. Action-Specific ARARs
Federal Clean Air Act requirements, 42 U.S.C. §7401 et seq.. are
applicable and must be met for the discharge of contaminants to
the air. Pennsylvania's Air Pollution Control Act is also
applicable, as are Pennsylvania's Air Pollution Control
Regulations (25 Pa. Code Chapters 121-142).
25 Pa. Code Section 123.31 is applicable to the selected remedial
alternative and prohibits malodors detectable beyond the NAWC
property line.
Regulations concerning well drilling as set forth in 25 Pa. Code
Chapter 107 are applicable. These regulations are established
pursuant to the Water Well Drillers License Act, 32 P.S.§ 645.1
et seq. Only substantive requirements of these regulations need
be followed for onsite actions.
The groundwater collection and treatment operations will
constitute treatment of hazardous waste (i.e., the groundwater
containing hazardous waste), and will result in the generation of
hazardous wastes derived from the treatment of the contaminated
groundwater (i.e., spent carbon filters from carbon adsorption
treatment of water and from vapor-phase carbon adsorption
treatment of air emissions from air stripping operations). The
remedy will be implemented in a manner consistent with the
requirements of 25 Pa. Code Chapter 262 Subparts A (relating to
hazardous waste determination and identification numbers), B
(relating to manifesting requirements for off-site shipments of
spent carbon or other hazardous wastes), and C (relating to
pretransport requirements); 25 Pa. Code Chapter 263 (relating to
transporters of hazardous wastes); and with respect to the
operations at the Site generally, with the substantive
requirements of 25 Pa. Code Chapter 264, Subparts B-D, I (in the
event that hazardous waste generated as part of the remedy is
managed in containers) and 25 Pa. Code, Subpart J (in the event
that hazardous waste is managed, treated or stored in tanks).
The remedy will be also be implemented in a manner consistent
with 40 C.F.R. Part 264, Subpart AA (relating to air emissions
from process vents), 40 C.F.R. Part 268, Subpart C, Section
268.30 and Subpart E (regarding prohibitions on land disposal and
prohibitions on storage of hazardous waste) and 40 C.F.R. Part
264, Subpart AA (relating to air emission standards for process
vents).
25 Pa. Code Chapter 264, Subchapter F, regarding groundwater
monitoring is applicable to the selected remedy.
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Any surface water discharge of treated effluent will comply with
the substantive requirements of Section 402 of the Clean Water
Act, 33 U.S.C. § 1342, and the National Pollutant Discharge
Elimination System ("NPDES") discharge regulations set forth at
40 C.F.R. Parts 122-125, the Pennsylvania NPDES regulations (25
Pa. Code §92.31), and the Pennsylvania Water Quality Standards
(25 Pa. Code §§93.1-93.9) which are applicable to the selected
remedy.
The Occupational Safety and Health Act ("OSHA") regulations
codified at 29 C.F.R. Section 1910.170 are applicable for all
activities conducted during this remedial action.
25 Pa. Code Sections 261.24 and 273.421 are applicable
regulations for the handling of residual and other waste and for
the determination of hazardous waste by the Toxic Characteristic
Leaching Procedure ("TCLP") .
Transportation of any hazardous wastes off-site shall also comply
with the Department of Transportation ("DOT") Rules for Hazardous
Materials Transport (49 C.F.R. Parts 107 and 171-179) .
The following four Action-Specific ARARs apply to any air
emissions from the groundwater treatment system and/or air
stripping operations (if necessary):
The requirements of Subpart AA (Air Emission Standards for
Process Vents) of the Federal RCRA regulations set forth at 40
C.F.R. Part 264 are relevant and appropriate and applicable to
any air stripping operations which are conducted as part of the
selected remedy. These regulations require that total organic
emissions from the air stripping process vents must be less than
1.4 kg/hr (3 Ib/hr) and 2800 kg/yr (3.1 tons/yr).
25 Pa. Code Section 127.12(a)(5) will apply to new point source
air emissions that result from implementation of the selected
remedy. These Commonwealth of Pennsylvania regulations require
that emissions be reduced to the minimum obtainable levels
through the use of best available technology. ("BAT") as defined
in 25 Pa. Code § 121.1.
The substantive requirements of 25 Pa. Code Section 127.11 will
apply to the selected remedy. These Commonwealth of Pennsylvania
regulations require a plan for approval for most air stripping
and soil venting/decontamination projects designed to remove
volatile contaminants from soil, water, and other materials.
Volatile organic compound emissions from the air stripper will be
treated by vapor-phase carbon adsorption as required by 25 Pa.
Code Chapter 127, Subchapter A, as well as the National Emissions
Standards for Hazardous Air Pollutants (NESHAPs) and the National
Ambient Air Quality Standards for Criteria Pollutants (NAAQS)
under the Federal Clean Air Act. EPA Directive 9355.0-28, which
covers emissions from air strippers at Superfund sites, is a
standard to be considered.
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3. Standards To Be Considered
Pennsylvania's Ground Water Quality Protection Strategy, dated
February 1992.
EPA Directive 9355.0-28, which covers emissions from air
strippers at Superfund groundwater remediation sites.
Pennsylvania Bureau of Air Quality Memorandum, "Air Quality
Permitting Criteria for Remediation Projects Involving Air
Strippers and Soil Decontamination Units".
EPA's Ground Water Protection Strategy, dated July 1991.
EPA OSWER Directive 9834.11 which prohibits the disposal of
Superfund Site waste at a facility not in compliance with §3004
and §3005 of RCRA and all applicable State requirements.
C. COST-EFFECTIVENESS
The selected remedy is cost-effective.
D. UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE TREATMENT
TECHNOLOGIES OR RESOURCE RECOVERY TECHNOLOGIES TO THE MAXIMUM
EXTENT PRACTICABLE
The remedy utilizes permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable.
E. PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The remedy satisfies the statutory preference for remedies that
employ treatment that reduces toxicity, mobility, or volume as a
principal element.
XI. DOCUMENTATION OF SIGNIFICANT CHANGES
The preferred alternative in the Proposed Plan was Alternative 3:
Groundwater Extraction, Treatment at Area A or Area C, and
Discharge to the Area A System Outfall. Based on public
comments, the selected remedy is Alternative 3 with one
modification. In particular, under the selected remedy, the
location of treatment of contaminated groundwater attributable to
Area C will be limited to Area A and thus will not be within Area
C.
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XII. RESPONSIVENESS SUMMARY
A. OVERVIEW
In a Proposed Plan released for public comment on August 19,
1994, the Navy, with the support of EPA, identified Alternative 3
as the preferred alternative for OU-3 at the Site. Alternative 3
in the Proposed Plan was as described in Section VIII. of this
ROD.
The majority of written and oral comments received during the
public comment period were in support of Alternative 3 as
described in the Proposed Plan and Section VIII. of this ROD,
including the Bucks County NAWC Economic Adjustment Committee,
which is developing a reuse plan for NAWC in response to the
planned realignment of NAWC. In addition, in one case, a
preference was expressed for Alternative 3, but with the location
of the treatment plant limited to Area A. Based on these and
other comments received during the public comment period, the
Navy and EPA have selected Alternative 3, with the treatment
plant location limited to Area A as requested during the comment
period. Other comments and the associated responses of the Navy
and EPA are described below after a brief discussion of community
involvement to date.
B. COMMUNITY INVOLVEMENT TO DATE
In July 1989, NAWC prepared a draft Community Relations Plan for
RI/FS activities. Community relations activities to date have
been conducted in accordance with this plan. These activities
have included regular Technical Review Committee/Restoration
Advisory Board meetings with local officials, communications with
the media and the establishment of information repositories.
The Navy and EPA established a public comment period from
September 1, 1994 to September 30, 1994 for interested parties to
comment on the Proposed Plan, the RI Report, the FFS Report and
other documents pertaining to OU-3. These and all other
documents considered or relied upon during the final remedy
selection process for OU-3 are included in the Administrative
Record, which has been in two information repositories accessible
to the public since the beginning of the public comment period
for OU-3. A public meeting was held at McDonald Elementary
School, Street Road, Warminster, Pennsylvania on September 8,
1994 to present the RI/FFS Reports and Proposed Plan, address
concerns, and accept both oral and written comments for the OU-3
final remedy. Approximately 40 people attended this meeting.
This Responsiveness Summary, required by CERCLA, provides a
summary of citizens' comments identified and received during the
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public comment period and the responses of the Navy and EPA to
those comments. All comments received by the Navy and EPA during
the public comment period were considered by the Navy and EPA in
selecting the final remedy for OU-3. Responses to these comments
are included in the section below.
C. SUMMARY OF COMMENTS RECEIVED DURING PUBLIC COMMENT PERIOD AND
COMMENT RESPONSES
Comments received during the public comment period regarding the
final remedy for OU-3 have been summarized below with the
responses of the Navy and EPA to these comments. The comments
and associated responses have been organized by subject category.
Remedial Alternative Preferences
Comment 1: A number of written and verbal comments expressed
a preference for Alternative 3. As noted above,
one commentor expressed a preference for
Alternative 3 with the condition that the
treatment system be located within Area A. No
preference was expressed for another alternative.
Response; Based in part on these comments, the Navy and EPA
have selected Alternative 3, with the modification
that treatment shall be limited to Area A.
Comment 2: Several commentors asked whether the treated water
could be spray irrigated, reinjected into the
groundwater or trucked offsite for disposal.
Response; Due to the fractured nature of the underlying
bedrock and the associated unpredictability of the
impacts of irrigation or reinjection, these
approaches were not considered. Trucking the
water offsite for disposal would be cost
prohibitive.
Comment 3; One commentor suggested the Navy consider
reserving some (or all) of the treated water for
fire fighting purposes or for commercial,
residential, recreational and/or industrial use.
Response; To assure that the remedy for OU-3 is implemented
in a timely fashion, the Navy and EPA believe that
the tEeated water should at least temporarily be
discharged to the planned surface water outfall.
However, the Navy will consider alternative means
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Comment 4
of managing the treated water in the future, as
necessary. The public may provide any further
comments on this matter through the Restoration
Advisory Board for NAWC.
Some commentors expressed concern about the
quantity of water to be extracted and the
potential impact of this extraction on water
supply wells in use.
Response: With the total groundwater extraction rate at Area
C estimated at 50 gallons per minute (gpm), there
is little or no drawdown effect (or impact)
projected for water supply wells currently in use.
Comment 5:
Response;
Questions were raised as to why the treated water
was being conveyed to a location north of Bristol
Road and whether the Navy would be discharging
into the same line that the Warminster Municipal
Authority discharges to.
The Navy plans to use its existing, permitted,
treated-water discharge system, which conveys the
treated water to the unnamed tributary of Little
Neshaminy Creek via an existing pipeline for
discharge at a location north of Bristol Road.
The Warminster Municipal Authority wastewater
treatment plant located further west on Bristol
Road also discharges into Little Neshaminy Creek
but through a different unnamed tributary.
Remedial Design and Implementation
Comment 6;
Response;
Several commentors questioned if the extraction of
contaminated groundwater should begin if the
source of the contaminated groundwater has not
been identified and cleaned up, and expressed
concern regarding a brownish tint in ponded water
near site 4.
Since contaminants from Area C have already
migrated into the bedrock aquifer, pumping and
treatment of the groundwater is required in any
case. To address buried waste at site 4, the Navy
is conducting an Engineering Evaluation and Cost
Analysis (EECA) to assess cleanup options.
Remediation of the source at site 4 should prevent
any additional contaminant migration to
groundwater from the buried waste. The Navy also
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plans to conduct a complete investigation of any
surface water that may be impacted by site 4 in
coordination with the EECA.
Comment 7; A number of commentors wanted to know how the 30
year treatment period was arrived at.
Response: Thirty (30) years is only an estimate of the
number of years that may be needed to achieve the
groundwater cleanup goals. The actual number of
years will depend on the performance of the
extraction system and will be established through
the Five-Year Review process.
Comment 8; One comment expressed concern that the existing
pipe carrying the treated water would not have
sufficient capacity.
Response: Calculations have been made using standard
engineering formulas on the outfall pipe capacity.
With peak flows from the NAWC Sewage Treatment
Plant and the new OU-l/OU-3 treatment plants,
there is adequate capacity in the outfall pipe.
It is noted that the flows from the NAWC Sewage
Treatment Plant will be diminishing as the Navy
relocates personnel from Warminster to Patuxent
River, MD.
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