Fourth Five-Year Review Report
Port Washington L-4 Landfill Superfund Site
Port Washington
Nassau County, New York
Prepared by:
United States Environmental Protection Agency
Region 2
New York, New York
September 2014
Walter E. Mugdan, Director
Emergency and Remedial Response Division
Date:
265557
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Table of Contents
Five-Year Review Summary Form v
Introduction 2
Site Chronology 2
Background 2
Physical Characteristics 2
Site Geology/Hydrology 3
Land and Resource Use 3
History of Contamination 3
Initial Response 3
Basis for Taking Action 4
Remedial Actions 4
Remedy Selection 4
Remedy Implementation 5
System Operations/Operation and Maintenance 7
Progress Since the Last Five-Year Review 7
Five-Year Review Process 8
Administrative Components 8
Community Involvement. 8
Document Review 8
Data Review 9
Site Inspection 10
Interviews 10
Institutional Controls 10
Technical Assessment 10
Question A: Is the remedy functioning as intended by the decision documents? 10
Question B: Are the (a) exposure assumptions, (b) toxicity data, (c) cleanup levels and (d)
remedial action objectives used at the time of the remedy still valid? 11
Question C. Has any other information come to light that could call into question the
protectiveness of the remedy? 12
Issues, Recommendations, and Follow-Up Actions 13
Protectiveness Statement 13
Next Review 13
Attachments: 14
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Figure 1 — Site Map 17
Figure 2 — Five Years of Downgradient Data for Well TW-2R (2008 — 2013) 18
Figure 3 — Graph of Downgradient Data for Well TW-2R (2005 to 2013) 19
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Five-Year Review Summary Form
SITE IDENTIFICATION
Site Name: Port Washington L-4 Landfill Superfund Site.
EPA ID:
NYD980654206
Region: 2
State: NY
City/County: Port Washington/Nassau County
NPL Status: Final
Multiple OUs?
Yes
Has the site achieved construction completion?
Yes
Lead agency: EPA
[If "Other Federal Agency", enter Agency name]: N/A
Author name (Federal or State Project Manager): Kevin Willis
Author affiliation: EPA RPM
Review period: 4/14/2009 to 9/14/2014
Date of site inspection: 2/10/2014
Type of review: Statutory
Review number: 4
Triggering action date: 4/14/2009
Due date (fiveyears after triggering action date): 4/14/2014
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Issues/Recommendations
Ol (s) without Issues/Recommendations Idcnlil'icd in the hive-Year Review:
01, 02
Issues and Recommendations Identified in the Five-Year Review:
OU(s): 3
Issue Category: Operations and Maintenance
Issue: VOC concentrations in downgradient wells remain elevated
Recommendation: Update conceptual site model and modify extraction
system to capture landfill leachate.
Affect Current
Protectiveness
Affect Future
Protectiveness
Party
Responsible
Oversight
Party
Milestone Date
No
Yes
PRP
EPA
9/30/2016
Protectiveness Statement(s)
Operable Unit: Protectiveness Determination: Addendum Due Date
01 Protective (if applicable):
N/A
Protectiveness Statement:
The OU1 gas collection system is protective of human health and the environment.
Operable Unit: Protectiveness Determination: Addendum Due Date
02 Protective (if applicable):
N/A
Protectiveness Statement:
The OU2 landfill cap remedy is protective of human health and the environment.
Operable Unit: Protectiveness Determination: Addendum Due Date
03 Short-term Protective (if applicable):
N/A
Protectiveness Statement:
OU3 is protective of human health and the environment in the short term, however, to be
protective in the long term, the groundwater extraction system must be modified to contain the
groundwater contaminant plume emanating from the L-4 landfill completely.
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Sitewide Protectiveness Statement
Protectiveness Determination: Addendum Due Date (if applicable):
Short-term Protective N/A
Protectiveness Statement: The remedy is currently protective in the short-term. In order to be
protective in the long term, the L-4 groundwater extraction system must be modified to contain
the plume emanating from the L-4 landfill completely.
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Executive Summary
This is the fourth five-year review for the Port Washington L-4 Landfill Superfund site (L-4). The
site is located in the Village of Port Washington, Town of North Hempstead, Nassau County, New
York. The purpose of this five-year review is to review information to determine if the remedy is
and will continue to be protective of human health and the environment. The trigger for this
statutory five-year review is the date of the previous Five-Year Review report, which was April
14, 2009.
The main components of the selected remedy for the site included 1) construction of a perimeter
gas collection system (operable unit 1 (OU1)); 2) construction of a Title 6 New York Codes, Rules
and Regulations Part 360 landfill cap (OU2); 3) construction of a groundwater extraction and
treatment system (OU3); and 4) implementation of long-term landfill gas and water quality
monitoring.
Based upon a review of monitoring data, a site inspection, and other site information, the U.S.
Environmental Protection Agency (EPA) concludes that the OU1 and OU2 components of the
remedy for the Port Washington Landfill Superfund site have been fully implemented consistent
with the site's decision documents and are protective of human health and the environment. OU3
is protective of human health and the environment in the short term, however, in order to be
protective in the long term, the groundwater extraction system must be modified to contain the
groundwater contaminant plume emanating from L-4 completely.
With respect to sitewide protectiveness, the remedy is currently protective in the short term. In
order to be protective in the long term, the L-4 groundwater extraction system must be modified
to contain the plume emanating from L-4 completely.
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Introduction
This is the fourth five-year review (FYR) for the Port Washington L-4 Landfill Superfund site (L-
4), located in Port Washington, Nassau County, New York. This review was conducted by United
States Environmental Protection Agency (EPA) Remedial Project Manager (RPM), Kevin Willis.
The five-year review was conducted pursuant to Section 121 (c) of the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA), as amended, 42 U.S.C.
Section 9601 et seq. and 40 CFR 300.430(f)(4)(ii) and in accordance with the Comprehensive
Five-Year Review Guidance, OSWER Directive 9355.7-03B-P (June 2001). The purpose of five-
year reviews is to assure that implemented remedies are protective of public health and the
environment and that they function as intended by the decision document(s). This report will
become part of the site file.
After completion of the remedial action, contaminants remain on the site. This five-year review
is being conducted as a statutory requirement. In accordance with the Section 1.3.3 of the Five-
Year Review Guidance, a subsequent statutory five-year review is triggered by the signature date
of the previous Five-Year Review report. The trigger for this subsequent five-year review is the
date of the previous Five-Year Review report, which was April 14, 2009.
The site is divided into three operable units (OUs). OU1 addresses landfill gas and the remedy
includes a perimeter gas collection system. OU2 addresses the L-4 landfill and the remedy
includes upgrades to an existing cap and installation of a cap over additional wastes. OU3
addresses contaminated leachate/groundwater from L-4 and the remedy includes the extraction
and treatment of groundwater. This FYR addresses all three OUs.
Site Chronology
See Table 1 for the site chronology.
Background
Physical Characteristics
The Port Washington Landfill is located in the northwestern portion of Nassau County, in Long
Island, New York. The landfill is located on a 139-acre lot, owned and operated by the Town of
North Hempstead (TNH, the Town). This property contains two landfilled parcels separated by a
vacant area (see Figure 1). The L-4 parcel is a 53-acre inactive closed landfill on the western
portion of the property. It is the designated Superfund site. The L-5 parcel, a closed landfill on
the eastern portion of the property, is not considered to be part of the site, and is being addressed
under Title 6 New York Codes, Rules and Regulations (6 NYCRR) Part 360 municipal landfill
closure requirements.
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The EPA is concerned with contamination caused by the L-4 parcel, and affected properties
(including the groundwater plume that extends northward from L-4 under the adjacent former
Morewood Property and the groundwater contamination observed immediately west of the L-4).
Site Geology/Hydrology
The site is located on the Manhasset Neck of Long Island. This area is mainly composed of
Pleistocene sand deposits interbedded with thrusted clay layers. Groundwater generally migrates
toward the adjacent Hempstead Harbor to the east.
Land and Resource Use
The site is bordered by Hempstead Harbor to the east, an industrial park to the south, residential
property and the North Hempstead Country Club to the west and the Town-owned Harbour Links
Golf Club (the former Morewood Property). There are two potable water wells remaining in use
in the area. The Stonytown Well (Lloyd Aquifer) is located 3,000 feet southwest and hydraulically
upgradient of L-4 and the Hewlett Well (Magothy Aquifer) is located 3,000 feet south and
hydraulically upgradient of L-4.
The Southport Well (Magothy Aquifer), located 1,300 feet west and hydraulically upgradient from
L-4, and the two Bar Beach Wells (Upper Glacial Aquifer), located 4,000 feet north and possibly
hydraulically downgradient of L-4, have been taken out of service.
History of Contamination
Prior to the Town's purchase of the landfill property in 1973, the site area was used as a sand and
gravel mining operation that began in the 1880s. After the mining operation had terminated, and
prior to development by the Town, the area was used by the Ail-American Sand and Gravel
Corporation as a landfill for construction debris. Landfilling at L-4 began in March 1974 with the
disposal of incinerator residue, residential and commercial refuse, and construction debris.
Initial Response
During the winters of 1979, 1980 and 1981 furnace explosions occurred in homes directly west of
the landfill. In 1981, air monitoring was performed in the area by the Nassau County Fire
Commission. The results of the air monitoring revealed excessive levels of methane in several
area residences. As a result, the Town initiated remedial measures to prevent the uncontrolled
migration of subsurface gases to the west of the landfill. A system of both active and passive gas
vents were utilized to collect vented gases and to flare them in a horizontal combustion unit to
destroy the hazardous chemicals commonly detected in sanitary landfill gas.
In 1981, the Nassau County Department of Health also tested for and discovered volatile organic
contaminants (VOCs), primarily chlorinated hydrocarbons, in the Southport Well. As a result, the
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well was removed from service as a potable water supply. The Town stopped accepting waste at
L-4 in 1983. Since then, the Town has continued to monitor the landfill's immediate environment
for both methane and hazardous chemicals.
The site was given final status on EPA's National Priorities List (NPL) in September 1983. The
New York State Department of Environmental Conservation (DEC) assumed the role of lead
agency for the site until February 1984, when DEC requested that EPA assume that role.
In October 1985, EPA developed a work plan to conduct a remedial investigation (RI) and
feasibility study (FS) at L-4. EPA then issued a notice to the Town of their liability as a potentially
responsible party, requesting that the Town either conduct or finance the RI/FS. In December
1985, the Town elected not to perform the specified work, although it wished to remain active in
the RI/FS process; EPA utilized funding provided through CERCLA to implement the RI/FS.
EPA began field investigations in December 1986, which included the installation of eleven
groundwater monitoring wells, four landfill gas monitoring wells, five landfill gas pressure
monitoring wells, and the deployment of an on-site meteorological station. EPA then commenced
a one-year monitoring period of these wells. The surface of L-4 was tested to estimate the amount
of landfill gas emitting from the surface of the landfill.
Basis for Taking Action
The media of concern at the site include groundwater and soil gas. There is a groundwater plume
containing VOCs, heavy metals and leachate indicator parameters (e.g., ammonia and total organic
carbon). Gases from the landfill were migrating into the adjacent residential community.
A human health risk assessment was conducted during the RI/FS. It was found that site
contaminants, predominately arsenic, vinyl chloride, 1,1-dichloroethane, and 1,1-
dichloroethylene, trichloroethylene and tetrachloroethylene posed an unacceptable risk from
exposure to and use of contaminated groundwater in the vicinity of the site. The risk assessment
also concluded that contaminant vapors posed a potential risk to residences adjacent to the landfill.
Remedial Actions
Remedy Selection
Based upon the findings of the RI/FS, EPA signed a September 1989 Record of Decision (ROD)
for the site selecting the following remedy:
Closure of L-4 in accordance with the 6 NYCRR Part 360 requirements for New York
State sanitary landfills;
- Rehabilitation of the existing active gas venting system;
- Extension of the existing active gas venting system around the entire perimeter of L-4;
Addition of a second gas combustion unit as standby;
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- Placement of extraction wells in the Upper Glacial Aquifer in areas with elevated levels of
groundwater contamination;
Treatment of extracted groundwater from the Upper Glacial Aquifer through metals
removal and air stripping prior to discharge to an aquifer recharge basin;
Treatment of groundwater at the Southport Well through air stripping should the Port
Washington Water District decide to use the Southport Well as a potable water source;
Installation of groundwater monitoring wells to define further the extent of the L-4 leachate
and VOC plumes, as well as to refine the placement of the proposed extraction wells;
Installation of additional groundwater and landfill gas monitoring wells around L-4 to be
used in conjunction with the existing landfill gas and groundwater monitoring network in
order to monitor L-4 comprehensively;
- Development and conduct of a comprehensive monitoring plan for L-4, including
performance monitoring of the gas venting system;
- Development and conduct of an operation and maintenance plan for remedial actions
selected in the ROD, as well as those previously employed for L-4.
Based on the risk assessment, the following Remedial Action Objectives (RAOs) were
developed for the site:
- Protect human health and the environment by controlling sources of contamination at the
site. The contaminants of concern for this site included the complete list of chemicals on
EPA's listing of hazardous chemicals of concern. This list was eventually narrowed to
contaminants detected above drinking water standards (1,1-dichloroethene, cis - 1,2-
dichloroethene, PCE, vinyl chloride, TCE and arsenic).
- Eliminate the potential exposure pathways.
- Restore lost resources. This includes the restoration of the aquifer and the loss of the local
water district's capacity to provide public water.
Remedy Implementation
In October 1990 EPA entered into a Consent Decree with the Town for implementation of the
September 1989 ROD. In September 1990, the Town tasked their existing contractor, LKB
Associates, Inc. (LKB), to implement the provisions in the ROD, whereby LKB produced the
initial action plans for site remediation. This included the plans for monitoring the affected
groundwater and soil gases on- and off-site. Following a change in the Town's administration, the
Town's contracted support was reevaluated. In October 1992, the Town entered into an agreement
with Blasland, Bouck & Lee, Inc. (BBL) who began performing the remedial design of the above-
described remedial activities and further groundwater investigations of the contamination related
to L-4.
Gas Migration Mitigation
Design work for the rehabilitation of the existing active gas venting system was finalized in June
1993 and the remedial action work began immediately thereafter. This phase of the site remedy
was undertaken first in order to ensure protection of the adjacent residences. A contingency plan
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was developed by the Town, in cooperation with EPA, NYSDEC, and the local resident's Citizen
Advisory Council (CAC), to establish the operational parameters of the facilities to assure the
protectiveness of the system. Under this contingency plan, a negative air pressure is to be
maintained in the gas monitoring wells immediately outside of the L-4 boundary, and if a power
failure were to occur, the modified landfill gas extraction system would be the first system to
receive power.
The construction of the extension of the active landfill gas extraction system was completed in
December 1999. This system circumscribes the northern and eastern edges of L-4 where soil gas
monitoring had detected some minor migration of landfill gases.
Capping and Closure of L-4 Cell
The remedial design (RD) for the closure of L-4 in accordance with the 6 NYCRR Part 360
requirements for New York State sanitary landfills was completed on March 31, 1995. The
remedial action (RA) work commenced with the Town's emplacing the subgrade for L-4. On
December 14, 1995, BBL subcontracted the remaining cap construction activities to Breco
Mechanical Group, Inc., who mobilized to the site on January 22, 1996. Construction was
completed for the L-4 cap and the final walkthrough inspection was held September 30, 1997.
L-4 Groundwater Extraction and Treatment
The expanded groundwater investigation required by the ROD began in September 1990 with a
monitoring plan designed by LKB. Once BBL was contracted, the first of the additional
monitoring wells was installed west of L-4. The first Supplemental Groundwater Investigation
Report was finalized in March 1994. In 1996, it was decided that sufficient data had been gathered
to design a groundwater extraction and treatment system to extract the contamination at its source,
but that additional investigation would be necessary to determine the fate and transport of the
plume of contamination migrating northward from L-4 that would not be captured by the
groundwater extraction and treatment system. The results of the groundwater investigation were
presented to EPA in the Phase II Groundwater Investigation Report in January 1997. Further data
gaps were recognized and additional monitoring wells were installed into the former Morewood
Property, north of L-4, in order to characterize the related plume.
The design of the L-4 groundwater extraction and treatment system began July 16, 1996.
Additional groundwater modeling was deemed necessary to calculate the capture zone necessary
to contain the observed contamination, which was completed as the system design developed. The
RD was approved by EPA in October 1997 and construction began immediately. The construction
of the pump and treat system was completed by January 1999.
Subsequently, the Town petitioned to power down the oxidizer for the gaseous effluent of the
groundwater extraction system. This effort was approved by EPA and the NYSDEC in February
2001 once the Town showed that all ambient air standards would be met with this modification to
the system.
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Negotiations between the Port Washington Water District and the Town resulted in replacing the
Southport Well with the construction of another public supply well outside of the local vicinity.
This well was constructed approximately two miles from the site due to State water use restrictions
for this part of Long Island. Construction of this well was completed in July 2000.
System Operations/Operation and Maintenance
An Operation and Maintenance (O&M) Manual was approved for the site operations in March
2000. The O&M manual outlined the regular maintenance procedures the Town is to follow during
the operation of the remedial systems at the site. O&M activities include the maintenance of the
groundwater extraction and treatment system, maintenance of the soil gas extraction system,
maintenance of the landfill cap and cover, and monitoring site conditions by means of semi-annual
sampling of the monitoring well network. This program was modified in 2011 to provide for
annual sampling of the monitoring well network.
Progress Since the Last Five-Year Review
The last five-year review was completed on April 14, 2009 and concluded that:
The OUI remedy (perimeter gas extraction system) which mitigates the migration of landfill gases
into the adjacent community has continually operated well and is fully protective of human health
and the environment.
The OU2 L-4 remedy (landfill cap) continues to be in well-maintained condition and is fully
protective of human health and the environment.
The OU3 implemented remedy (groundwater extraction and treatment system) was returned to
service in spring 2009. The OU3 remedy was expected to be protective of human health and the
environment upon completion of the groundwater extraction and treatment system refurbishment,
and in the interim, exposure pathways that could result in unacceptable risks are being controlled.
The five-year review also identified the need to complete the following activities:
- Return the groundwater extraction and treatment system to operation;
- Replace monitoring wells destroyed during the Harbor View Estates construction; and
Abandon numerous unused monitoring wells.
L-4 Extraction and Treatment System
During this five-year reporting period the groundwater extraction and treatment system has been
rebuilt and has been operating since the construction was completed in April 2009. Review of the
last five years of data continue to show fluctuating contamination observed in monitoring well
TW-2R downgradient of L-4, a well that was thought to be beyond the capture zone of the
extraction and treatment system. It should be noted that prior to its refurbishment, the groundwater
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extraction and treatment system had some periodic operational problems that were suspected to
have resulted in these fluctuating levels. However, because contaminant levels are still elevated
and fluctuating at TW-2R, EPA believes that the contamination observed in this well may be
indicative of incomplete containment of the groundwater contaminant plume emanating from L-4
(see Figures 2 and 3). EPA will ask the Town to address this issue and modify the groundwater
extraction system as appropriate to contain the L-4 groundwater contamination plume completely.
Harbor View Estates Monitoring Wells
The Town replaced the monitoring wells destroyed by the construction of the Harbor View Estates
in September 2011. These new wells have been incorporated into the groundwater sampling plan.
Sampling results from these wells are discussed in the Data Review Section.
Abandonment of Unused Monitoring Wells
The Town has begun the well abandonment process by decommissioning an approved subset of
the unused monitoring wells. This effort has been temporarily postponed because changes in area-
wide groundwater use suggest that it may be necessary to put some of these wells back into service.
Five-Year Review Process
Administrative Components
The five-year review team consisted of Kevin Willis (RPM), Robert Alvey (Hydrogeologist),
Charles Nace (Ecological Risk Assessor), and Julie McPherson (Human Health Risk Assessor) of
the EPA.
Community Involvement
The EPA Community Involvement Coordinator (CIC) for the Port Washington L-4 Landfill site,
Cecilia Echols, published a notice on the Town of North Hempstead's official website on
September 16, 2014 notifying the community that a five-year review was being conducted. The
notice indicated that EPA would be conducting a five-year review of the remedy for the site to
ensure that the implemented remedy remains protective of human health and the environment and
is functioning as designed. It was also indicated that once the five-year review is completed, the
results will be made available in the local site repositories. In addition, the notice included the
RPM and the CIC's addresses and telephone numbers for questions related to the five-year review
process for the Port Washington L-4 Landfill site.
Document Review
The documents, data and information which were reviewed in completing this five-year review
are summarized in Table 2.
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Data Review
Groundwater data have continually been collected by the Town since the last FYR. A meeting
was held on July 7, 2011 between the Town and their consultants, Jignesh Shah from NYSDEC,
and Kevin Willis from EPA, to discuss the ongoing sampling at the Port Washington Landfill. The
Town presented a combined sampling program that would sample the entire landfill facility (L4
and the former Morewood property for EPA and L-5 for NYSDEC) on an annual basis. Wells that
have historically not been contaminated were removed from the sampling plan. Both NYSDEC
and EPA agreed to the proposed approach.
At the time of the last FYR, the rebuilding of the L-4 groundwater extraction and treatment system
was not yet completed. The refurbished system includes new extraction well pumps and a new
electrical control system. The system was completed shortly after the previous FYR was published
and began operating in 2009. The monitoring wells to replace the wells destroyed during the
construction of the Harbor View Residential Facility were also replaced in September 2011.
L-4 Groundwater Extraction and Treatment System
Since its 2009 refurbishment, the L-4 groundwater extraction and treatment system has been
operating continuously. The influent into the groundwater treatment system has shown very low
VOC concentrations (below MCL levels for PCE and TCE) and the VOC concentrations have
been nondetectable after treatment. The chloride numbers are increasing to just above drinking
water standards, which is likely due to the regional potable water pumping exceeding the NYSDEC
water budget.
Groundwater Monitoring Data
Monitoring well TW-2R has historically been showing VOC concentrations that have fluctuated
within a consistent range between 50 and 100 ppb total VOCs. The conclusion from earlier
reviews of these data was that the fluctuations of VOC contamination downgradient of the L-4
groundwater extraction system were largely due to the system being in disrepair. Analysis of the
data since the system has been refurbished suggests that the downgradient contaminant
fluctuations are not indicative of mechanical failure, but possibly due to an incomplete hydraulic
containment by the extraction well array. EPA will ask the Town to undertake an evaluation of
the capture zone of the existing array of extraction wells and modify the system as appropriate.
In addition, EPA will also require that the Town include wells TNH 26, TNH 27, and EPA-102 in
the sampling plan and that all wells in the monitoring network be sampled semi-annually. EPA
will also be evaluating the site data with the recent area-wide observations that the water-use
changes in the Manhasset Neck has changed the area's groundwater flow dynamics creating salt-
water intrusion into the local aquifer system.
Summary
Since the extraction and treatment system has been restarted, groundwater monitoring wells still
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show persistently high levels of contaminants downgradient of the extraction system. If the capture
zone produced by the array of extraction wells were complete, it would be expected that the
downgradient contamination levels, particularly at monitoring well TW-R2, would steadily
diminish. As that is not occurring, further study and analysis is warranted. If the influence of the
capture zone of the existing extraction wells is insufficient to contain the groundwater
contamination above MCLs, the system must be modified to attain containment of the groundwater
contaminant plume emanating from the L-4 landfill.
Site Inspection
A site inspection was conducted on February 10, 2014. The following parties were in attendance:
Kevin Willis, EPA, Region 2 RPM
Paul Carpenter, Town of North Hempstead
During the site inspection, all equipment was fully operational. Review of operational records
showed that the L-4 groundwater extraction and treatment system has been fully operational since
being refurbished, except for brief periods of maintenance and repair. The redundancies in the
landfill gas extraction system have allowed for its continuous operation and the system remains
fully protective of the adjacent community.
Interviews
The EPA RPM spoke with Igor Sikiric, Commissioner of Solid Waste, and Paul Carpenter, both
of the Town about any concerns relayed by local citizens. None were reported. The Port
Washington Water District (PWWD) had toured the site with the Town officials and had left with
no concerns raised.
Institutional Controls
The remedy for the site did not include specific institutional controls (ICs), but New York State
mandates that no drinking water wells will be installed in the area and other local ordinances and
mechanisms are in place to prevent exposure. In addition, L-4 is owned by the municipality, and
EPA believes that the municipality will act appropriately to enforce the ICs which prevent wells
from being installed and therefore prevent exposure.
Technical Assessment
Question A: Is the remedy functioning as intended by the decision documents?
The remedy selected for the site included (1) closing of the landfill in accordance with 6 NYCRR
Part 360, (2) rehabilitation of the existing gas collection system and installation of additional active
vents around the perimeter of the landfill, (3) replacing lost drinking water capacity due to the
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closure of the Southport well and (4) installation of additional extraction wells.
The remedial action objectives as identified in the 1989 ROD, are (1) control the sources of
contamination at the site, (2) eliminate the potential exposure pathways and (3) restore lost
resources.
The remedy selected to address the soil is currently in place. L-4 has been closed and capped in
accordance with 6 NYCRR Part 360 and is currently being maintained by the Town. The cap is
inspected annually by EPA to ensure that the landfill cover has not been compromised. As a result
of the remedy and follow up maintenance of the landfill cap, the exposure pathway to potential
receptors via exposure to landfill soil has been interrupted. The source control remedy as identified
in the ROD is currently functioning as intended.
The remedy selected to address the groundwater has been implemented. The system has recently
been refurbished and has been operating continuously. The groundwater plume emanating from
the L-4 landfill has been continually and regularly monitored.
Concerns were raised in the previous FYR that concentrations of several constituents had increased
in the monitoring wells downgradient of L-4 as a result of the L-4 groundwater extraction and
treatment system being in disrepair. After the system was refurbished, evaluation of the data shows
that the concentrations of VOCs in monitoring well TW-2R remain elevated and continue to
fluctuate within the same range as levels that were present before the system was restarted. This
suggests that the system is not fully containing the contaminant plume emanating from L-4. EPA
will work with the Town to update the conceptual site model and modify the groundwater
extraction system to contain the landfill leachate completely.
The existing government controls prevent the installation of wells on the property. In addition,
residents are connected to a municipal water supply. Groundwater use is not expected to change
in this area within the next five years, the period of time until the next review.
Question B: Are the (a) exposure assumptions, (b) toxicity data, (c) cleanup levels and (d)
remedial action objectives used at the time of the remedy still valid?
Groundwater use is not expected to change during the next five years, the period of time considered
in this review. Currently, the residential properties within the potential downgradient plume area
are connected to the public municipal water supply. The landfill has been capped in accordance
with 6 NYCRR Part 360.
The toxicity values used to calculate the noncancer health hazards and the cancer risks have
changed. Some chemical toxicity values have changed and some new toxicity values were
developed for other contaminants since the site was originally assessed (1989, ARCS II). The
groundwater remedy selected Federal or State National Primary Drinking Water Standards MCLs
as cleanup levels. Concentrations of several VOCs continue to exceed their respective MCLs in
several monitoring wells.
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As noted in the 2004 FYR, the land use downgradient from the landfill has changed since the ROD
was signed. An elder care facility was constructed relatively close to the residential development
directly downgradient from the site. As a result of the 2004 FYR recommendations, soil vapor
intrusion was evaluated as a potential exposure pathway. Several homes within the development
were evaluated. The evaluation determined that vapor intrusion is not of concern in this area.
Groundwater VOC concentrations in wells under this area are consistent with the levels found in
the same wells when the Soil Vapor Analysis Study was done in 2008. EPA believes that the
Harbor View Residential Community remains unaffected by migration of VOCs emanating from
the plume of contamination that is migrating from L-4. In addition, since the last FYR, newly
constructed replacement wells, MW-28 S and D, closest to the development, have not shown VOC
contamination since their installation.
The following are the remedial action objectives identified for this site: (1) protect human health
and the environment by controlling the sources of contamination, (2) eliminating the potential
exposure pathways and (3) restoring lost resources. The remedial action objectives as described
in the ROD are still valid.
The ecological evaluation that was conducted for the previous FYR indicated that although there
were no references to an ecological risk assessment in the ROD or subsequent five-year reviews,
the primary concern from an ecological perspective would be discharge of contaminated
groundwater to surface water. As part of the 2009 FYR an evaluation of the historic groundwater
data from a downgradient well next to Hempstead Harbor was conducted and it showed that VOCs
in monitoring well TNH-18S, which is located west of Shore Road between the landfill and
Hempstead Harbor, had sporadic, low detections, suggesting that there was little to no migration
of compounds from the site. A conclusion was drawn that there were no adverse ecological impacts
due to site-related contaminants.
As part of this FYR evaluation, additional current and historical data (2004 through 2013) for well
TNH-18S were evaluated. The data show that the majority of the results are nondetectable for
VOCs, with a few sporadic low concentrations of VOCs detected. The concentrations of VOCs
that were detected are either estimated values below the detection limits or just above the detection
limits, but well below ecological screening values. This suggests that the conclusion reached in
earlier FYR that site-related contaminants in the groundwater are not migrating and discharging to
Hempstead Harbor, is still valid. Given that the contaminants in the groundwater do not discharge
to any surface water body, and the residual contamination in the landfill is capped, there are no
impacts to ecological receptors.
Question C. Has any other information come to light that could call into question the
protectiveness of the remedy?
Evaluation of the historical groundwater data seems to indicate that the L-4 groundwater
extraction and treatment system is not fully containing the contaminant plume emanating from
L-4. The system needs to be reevaluated and modified to contain the contaminant plume from
migrating past the groundwater extraction and treatment system completely.
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Issues, Recommendations, and Follow-Up Actions
EPA has determined that the conceptual site model needs to be updated to understand better the
fate and transport of leachate in groundwater. Based on this evaluation, the groundwater extraction
and treatment system will need to be modified to contain the contaminant plume from migrating
past the groundwater extraction and treatment system completely.
Wells TNH 26, TNH 27 and EPA-102 need to be included in the monitoring network and all wells
in the monitoring network need to be sampled semi-annually. EPA will also be evaluating the site
data relative to the recent area-wide observations that the water-use changes in the Manhasset Neck
have changed the area's groundwater flow dynamics creating salt-water intrusion into the local
aquifer system.
Protectiveness Statement
The OU1 remedy (perimeter gas extraction system) which mitigates the migration of landfill gases
into the adjacent community has continually operated well and is fully protective of human health
and the environment.
The OU2 remedy (landfill cap) continues to be in well-maintained condition and is fully protective
of human health and the environment.
The OU3 remedy (groundwater extraction and treatment system) is protective of human health and
the environment in the short term, however, to be protective in the long term, the groundwater
extraction system will need to be modified to contain the groundwater contaminant plume
emanating from L-4 completely.
Next Review
The next five-year review for the Port Washington L-4 Landfill site should be completed within
five years from the completion date of this review
13
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Attachments:
Table 1 : Chronology of Site Events
Event
Date
Site placed on National Priorities List
September 1983
EPA developed Remedial Investigation Work Plan
October 1985
Record of Decision (ROD) signed by EPA
September 1989
Consent Decree between EPA and the Town of North Hempstead to
implement the ROD entered with the Eastern District Court
October 1990
Notice of contract award issued to LKB Associates, Inc. by the Town
of North Hempstead
September 1990
Supplemental Groundwater Investigation initiated
September 1990
Town reevaluated remediation contract and awarded the remediation
contract to Blasland, Bouck, and Lee, Inc.
October 1992
Remedial Design (RD) for active gas venting system approved by
EPA and construction initiated
June 1993
RD for L-4 landfill cap approved by EPA and initial construction was
initiated by the Town
March 1995
Final As-Built Drawings submitted by Blasland, Bouck, and Lee
June 1995
Remaining landfill cap construction activities awarded to Breco
Mechanical Group, Inc.
December 1995
Breco Mechanical Group, Inc. mobilized to site
January 1996
Determination made that adequate groundwater data were collected to
begin RD for groundwater extraction and treatment system
July 1996
Final inspection of landfill cap construction conducted by EPA,
NYSDEC and various contractors
September 1997
RD for groundwater extraction and treatment system approved
October 1997
Operation and Maintenance Plan submitted by Blasland, Bouck, and
Lee
December 1998
14
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Operation of groundwater extraction and treatment system began
January 1999
First Five Year Review Report signed by EPA
April 1999
Groundwater monitoring sampling performed
December 1989 to
Present
Quarterly Groundwater Monitoring Report submitted by Town of
North Hempstead
March 1998 to
Present
Monthly perimeter gas system monitoring performed
September 1994 to
present
Final Approval of Site wide Operations and Maintenance Manual
March 2000
Preliminary Closeout Report signed
July 2000
Second Five-Year Review Report signed by EPA
April 2004
Vapor Intrusion Study conducted
April 2007
Additional plume delineation/ monitoring well replacement
Work underway
Third Five-Year Review Report signed by EPA
April 2009
Refurbishment of groundwater extraction system
May 2009
15
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Table 2: Documents Reviewed
Author
Date
Title/Description
USEPA
June 1989
Remedial Investigation
Report
USEPA
September 1989
Record of Decision
USEPA
March 2000
O&M Manual for Remedial
Activities at Port Washington
L-4 Landfill
Town of North Hempstead
August 2001
Port Washington Landfill
Groundwater Treatment
System Off-Gas Evaluation
Report
Town of North Hempstead
August 2004 - Present
Progress Reports/Monitoring
Data
USEPA
April 2009
Third Five-Year Review
Report
16
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Figure 1 - Site Map
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Port Washington L-4 Landfill Superfund Site Map
Groundwater Sampling Locations
R & C Formation, Ltd.
Professional Groundwater and Evironmental Services
Port Washington Landfill
Tcwn of North Hempstead, NY
171 Deer Park Ave., Suite 3
Babylon, New York 11702
Prepared By: MY
Reviewed By: RNC
Figure 1
April, 2014
17
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