SECOND FIVE-YEAR REVIEW REPORT FOR

SYOSSET LANDFILL SUPERFUND SITE NASSAU COUNTY

SYOSSET, NEW YORK

Prepared by: United States Environmental Protection Agency

Region 2 New York, New York

January 2007

Table of Contents

List of Acronyms ..................................................................................................................................................... iv

Executive Summary ................................................................................................................................................. I

Five-Year Review Summary Form ............................................................................................................................ 2

1. Introduction .................................................................................................................................................. 4

11. Site Chronology 4

111. Site Background Sire Location and Physical Characteristics .................................................

History of Conlaminatio

............................................................................................................................................ 5

1V. Remedial Action 6 Remedy Selection OUI .......... ......... ...... ..... 6 Remedy Implementation OUI 6 Reme& Selection OU2 7 Remedy Implementation OU2 7 Sy~tems OperatiodOp 7 Institutional Conho/s lmplementat 8

V. Progress Since Last Five-Year Review ............................................................................ .. .... ..... 8

V1. Five-Year Review Process Adminisrrative Component Communiry Involvement Document Revie

Site Inspection ................... .. ..... .. ..... ....... ................................................................ 12

VII. Technical Assessme 12 Question A: Is the remedy . ....................................... ........... ........ 12 Qzrestion B: Are the exposure assumptions, toxicicy dare, cleanup levels, and remedial action objectives used at rhe rime ufthe remedy still vaii 13

14 Technical Assessment Summa~y .................... .. ....... .................................................................................... 14

VIII. Issues, Recommendations and Follow-up Actions ................................................................................... 14

IX. Protectiveness Statement ............................................................. .. .................................................... . 15

X. Next Review .. ................................................. 15 . . 11

Tables

Table I : Chronologv of Site Events

Table 2: Estimated Annual Monitoring Costs

Table 3. List of Documenls Reviewed

Table 4: VOCs resz~ltsfrom the 2005 Annub1 Monitoring Report detected in oflsite monitoring n,ells compared to Primary Drinking Water Standard (Maximum Contaminant Level) and New York Department of Environmental Conservation Ambient Water Quality Standards and Guidance Values Regulations (NYSDEC WQR)

Table 5: Metals resultsfrom the 2005 Annual Monitoring Report detected in on-sile monitoring wells compared to Primary Drinking Water Standard (Muximum Conraniinant Level) and New York Deparhnent of Environmental Conservation Ambient Water Quality Standards and Guidance Vahies Regulations (NYSDEC WQR)

Table 6: Comparison of fhe On-Site maximum detected mncentration of arsenic detected in the on-site monitoring wells lo [heir respective human health risk basedscreening criteria (Preliminary Remediation Goal), Primary Drinking Water Standard (Maximum Contaminant Level) and New York Department ofEnvironmentu1 Conservation Water Quality Regulations (NYSDEC WQR)

Table 7: Other Comments on Operation. Maintenance. Monitoring, and lnstitzrtional Controls

iii

CERCLA

CIC

coc

EPA

ESD

HDPE

MCL

NCP

NYSDEC

NYSDOH

O&M

ou

PRP

RD

RI

ROD

RPM

v o c s

List of Acronyms Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended

Community Involvement Coordinator

Contaminant of Concern

United States Environmental Protection Agency

Explanation of Significant Differences

High Density Polyethylene

Maximum Contaminant Level

National Oil and Hazardous Substances Pollution Contingency Plan

New York State Department of Environmental Conservation

New York State Department of Health

Operation and Maintenance

Operable Unit

Potentially Responsible Party

Remedial Design

Remedial Investigation

Record of Decision

Remedial Project Manager

Volatile Organic Compounds

Executive Summary

This second Five-Year Review for the Syosset Landfill Superfund Site (the Site) located in Syosset, Nassau County, New York, has been completed by EPA Region 2.

Based upon reviews of the two Records of Decision, Annual Ground-Water Sampling Results, and Site Inspection Reports as prepared by the Town of Oyster Bay, as well as a Site visit by EPA personnel in November 2006, EPA has concluded that the remedies as set forth in the decision documents for the Site continue to protect human health and the environment.

Five-Year Review Summarv Form

I Site Name (from WasteLAN): Syosset Landfill Superfund Site I

I Region: 2 1 State: NY I CitylCounty: SyosseVNassau

( NPL Status: O Final . Deleted Other (specify)

Remediation Status (choose all that apply): Under Construction Operating

Complete

I Multiple OUS? rn YES NO I Construction completion date: 09/18/1998 I I Has site been ~ u t into reuse? YES NO NIA

Lead agency: EPA u State Tr~be 0 Other Federal Agency

Author name: Sherrel D. Henry

I Author title: Remedial Project Manager I Author affiliation: EPA I I Review ~eriod:*' 11/21/2001 to 11/21/2006 I

Date@) of site inspection: 11/21/2006

Type o f review: Post-SARA Pre-SARA NPL-Removal only Non-NPL Remedial Action Site O NPL Statenribe-lead Reaional Discretion W Statutoiv

Review number: 1 (first) rn 2 (second) 3 (third) Other (specify)

Triggering action: Actual RA Onsite Construction at OF #- Actual RA Start at OF#-I- Construction Completion Previous Five-Year Review Report Other (soecifv)

I Triggering action date (from Wasteland): 11/21/2001 I I Due date (five years after triggering action date): 11/21/06 I

Does the report include recommendation(s) and follow-up action(s)? yes no Acres in u s e or avai lable f o r use: restricted:= unrestr icted:

Five-Year Review Summary Form cont'd.

Issues, Recommendations and Follow-up Actions:

The selected remedy, described in two RODS, has been h l l y implemented. There are ongoing operation, maintenance, and monitoring activities included in the selected remedy. As was anticipated by the decision documents, these activities are subject to routine modification and adjustment. Table 7 includes suggestions for improving, modifying and/or adjusting these activities. New York State requires annual certifications that institutional controls are in place and that remedy-related operation and maintenance (O&M) is being performed. Annually, the potentially responsible parties will need to certify that the existing institutional controls remain in place and that remedy-related O&M is being performed.

Protectiveness Statement:

The implemented remedy for the Syosset Landfill Superfund Site protects human health and the environment. There are no exposure pathways that could result in unacceptable risks and none are expected as long as the site use remains consistent with the site's access and institutional controls and those controls are properly monitored and maintained.

I. Introduction

The U.S. Environmental Protection Agency (EPA) conducted this Five-Year Review for the Syosset Landfill Superfund Site (the "Site") pursuant to Section 121(c) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended, 42 U.S.C. S9601 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 a Five- Year review is to ensure that implemented remedies protect public health and the environment and continue to function as intended by the Site's decision documents. This document will become part of the Site file.

EPA addressed the Site using two separate components called operable units (OUs). EPA designated the on-property effort as OU1 and the off-site work as 0U2. This is the second Five- Year Review. In accordance with 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 Five-Year Review is the date of the previous Five-Year Review Report, which was November 2 1,2001.

II. Site Chronology

Table 1, which is attached, summarizes the Site-related events running from the disposal of hazardous wastes at the Site though the cleanup process.

III. Sife Background

Site Locationand Physical Characteristics

The Site is located in Syosset, in the Town of Oyster Bay ("the Town"), Nassau County, New York. The Site is rectangular in shape and covers approximately 38 acres. The Site is relatively flat and at a similar elevation to the surrounding area. There are two recharge basins owned by Nassau County which border the Landfill to the north and northeast. Both basins collect storm water runoff from the neighboring residential area for recharge to the underlying groundwater aquifers. The offices and facilities for the Town's Department of Public Works are located adjacent to the landfill to the east and occupy 15 acres. The Town controls access to the Site, and the entire landfill area is enclosed by a six-foot high chain-link fence. The Site is bounded by the Long Island Expressway and Miller Place to the southeast, property formerly occupied by Cerro Conduit Company to the southwest, and the Long Island Railroad to the northwest. A residential area and the South Grove Elementary School border the Site to the northeast.

Land and Resource Use

The landfill is owned by the Town and is located in a densely populated residential and industrial area. Total population of Syosset is estimated to be 10,400 people. All the residents around the Syosset Landfill get their drinking water from public supply wells. These or similar uses are expected to continue well into the future.

History of Contamination

The Town operated the landfill from approximately 1933 to 1975. Between 1933 and about 1967, no restrictions were imposed on the types of wastes accepted at the landfill. Categories and types of wastes included: commercial, industrial, residential, demolition, agricultural, sludge material and ash. After about 1967, waste disposal at the landfill became restricted, though disposal of wastes (including industrial wastes) continued. Several large companies have been identified as generators of large quantities of waste that were disposed at the landfill over a period of years. Types of waste disposed included heavy metals, solvents, organics, oils, plasticizers, and polychlorinated biphenyls.

Initial Response

The landfill was closed on January 27, 1975 because of a suspected groundwater pollution problem. In 1981, the Town installed a passive gas venting system along the property line shared by the landfill and the South Grove Elementary School to prevent off-site gas migration. The system consisted of a gravel-filled gas venting trench and a series of PVC gas vent riser pipes on both sides of the gas venting trench. The effectiveness of the trench was verified by comparing the levels of gas contaminants within the riser pipes on both sides of the trench. Typically, contaminant levels on the school side of the trench were low, while levels on the landfill side of the trench were higher. A Combustible Gas Indicator was used to monitor for methane. The data were submitted to New York State Department of Environmental Conservation (NYSDEC), New York State Department of Health (NYSDOH), Nassau County Department of Health (NCDOH), and the Syosset Central School District on a monthly basis.

Busisfor Taking Action

In January 1983, Environmental Resources Management-Northeast (ERM) prepared a report summarizing the results of a study perfonned for the NCDOH. The report concluded that the groundwater quality was being impacted by landfill leachate. ~ levated heavy metal concentrations including arsenic, cadmium, chromium and lead were detected at levels exceeding New York State Primary Drinking Water Standards. One public drinking water well which is down gradient of the Site was closed due to taste and odor problems. The Site was placed on the Superfund National Priorities List in September 1983.

On June 19, 1986, EPA and the Town entered into an Administrative Order on Consent (Index No. I1 CERCLA-60203). The Order required the Town to conduct a Remedial Investigation (RI) and Feasibility Study at the Site with provisions for performing off-site investigations as deemed

necessary. As indicated below, EPA designated the on-property effort as OU1 and the off-site work as 0U2.

IK Remedial Actions

Remedy Selection OUI

EPA issued a Record of Decision (ROD) for the Site on September 27, 1990. The major components of the selected remedy include the following:

Implementing New York State landfill closure requirements as specified in 6 NYCRR Part 360, solid waste management facilities regulations, which included construction of a geosynthetic membrane cap on the top surface of the landfill; Providing long-term air and groundwater quality monitoring; Monitoring and maintaining the passive gas venting system installed under a previous implemented response action, including routine inspection and repairs; Establishing institutional controls in the form of deed restrictions on future uses of the landfill; . Installing an additional passive gas venting system, designed so that it can easily be converted to an active system should conversion become necessary; and Maintaining the existing boundary fence around the perimeter of the landfill property to continue to restrict access to the landfill.

In addition, because leachate indicator chemicals were identified in groundwater beneath and down gradient of the landfill, the ROD also specified that a supplemental remedial investigation be conducted to study the potential off-site impacts of the landfill, designated as OU2.

Remedy Implementation OUI

The OU1 ROD was implemented pursuant to a Consent Decree entered into by EPA and the Town. This Consent Decree was entered by the U.S. District Court for the Eastern District of New York on February 20, 1991. The Town hired Lockwood, Kessler & Bartlett, Inc. (LKB) to perform the Remedial Design and Remedial Action.

In November 1994, the Town initiated the first of two construction contracts. The first contract consisted of a Preload Program which involved placing clean fill material on portions of the landfill to heights of four feet in excess of the final capping subgrade (bottom elevations). The second construction contract consisted of a Capping and Closure Program. The landfill cap and gas venting sand layer were placed on top of the cap subgrade which was constructed under the Preload Program. The Capping and Closure Program was completed in November 1997. EPA conducted a final inspection with NYSDEC and the Town on November 5, 1997. In October 1999, EPA issued its approval of the Remedial Action Report, signifying that the remedial action

had been completed in accordance with the ROD and Remedial Design, and the project entered the operation, maintenance, and monitoring phase.

Three different surface covers have been placed over the cap to allow for the reuse of portions of the Site property. Asphalt was used in areas identified for vehicle parking and equipment storage; recycled concrete was utilized in areas designated for composting and material storage; and, a vegetative cover was used in buffer areas.

The paved areas of the Site are being utilized by the Town's Highway Division and include a salt storage facility, a miscellaneous equipment storage facility, a vehicle parking facility and a Sanitation vehicle facility. The recycled concrete area is being utilized as the Highway Division material storage facility.

Remedy Selection 0U2

The 0 U 2 RI was conducted from October 1992 to March 1994 and consisted of an off-site ground- water study and an off-site subsurface gas study. The purpose of the off-site groundwater study was to determine the extent and thickness of a leachate plume emanating from the landfill. The purpose of the off-site gas study was to determine the extent of off-site subsurface gas migration from the landfill. The RI including the risk assessment concluded that no additional action was needed to protect public health and the environment.

Remedy Implementation 0U2

EPA issued a No Further Action ROD on March 28, 1996. EPA, in consultation with NYSDEC, determined that off-site contamination from the landfill does not pose a significant threat to human health or the environment; therefore, remediation was deemed not to be necessary. However, the 0 U 2 ROD also specified that the environmental monitoring program selected as part of the OU1 remedy include sampling for both on-site and off-site groundwater.

Systems OperatiodOperation and Maintenance (O&M)

Pursuant to the two RODS, and as otherwise approved by EPA, the necessary O&M activities currently include:

Annual ground water quality monitoring at 11 monitoring wells to ensure that the landfill continues to be protective to public health and the environment; Groundwater elevation monitoring at 21 monitoring wells to determine if changes occur in the direction of ground water flow; Inspection of the landfill to insure that no erosion damage has occurred; and Submittal of quarterly reports.

Table 2 provides an estimate of annual monitoring costs.

Institutional Controls Implementation

Institutional controls have been put in place at the Site. Counsel for the Town has provided EPA with a copy of the cover page of the Consent Decree bearing the stamp of the Nassau County Clerk's Office, showing that the Consent Decree was recorded in that office on December 6, 1990. The Counsel has also provided EPA with a copy of restrictive covenants placed on the real property at the Site by the Town of Oyster Bay, filed with the land records on March 23, 2004. These items complete the institutional controls requirement of the 1990 ROD.

I/. Progress Since Last Five-Year Review

The first Five-Year Review was signed in November 2001, pursuant to OSWER Directives 9355.7-02 (1991), 9355.7-02A (1994), and 9355.7-03A (1995). The first Five-Year Review concluded that the implemented remedy continued to be protective of public health and the environment. There were no recommendations, follow-up actions, or issues presented in the first Five-Year Review. Additional monitoring, which has occurred since the first Five-Year Review, is discussed in this report.

VI. Five-Year Review Process

Administrative component.^

The Five-Year Review Team consisted of: Sherrel Henry (Remedial Prqject Manager [RPM]), Robert Alvey @ydrogeologist), Marian Olsen (risk assessor), and Leilani Davis (attorney).

Community Involvement

The EPA Community Involvement Coordinator for the Site, Cecilia Echols, published a notice in the Jericho Tribune, a local newspaper, on October 13, 2006, notifying the community of the initiation of the Five-Year Review process. 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 public health and the environment and is functioning as designed. It also indicated that once the Five-Year Review is completed, the results will be made available in the local Site repository. The notice also solicited public comments or questions related to the Five-Year Review process or to the Site.

In addition, the notice included the RPM's mailing address, e-mail address, and telephone number for any public comments or questions.

Document Review

The documents, data, and information which were reviewed in conducting this second Five-Year Review are summarized in Table 3 (attached).

Monitoring and Data Review

The primary objectives of the implemented remedy are to control the source of contamination at the Site, to reduce and minimize the migration of contaminants into the groundwater and to minimize any potential human health and environmental impacts resulting from the exposure to contamination at the Site. These objectives were accomplished by the installation of a containment system. A long-term monitoring program was designed to ensure that the implemented remedy remains effective.

The long-term monitoring program, which is being conducted by the Town, includes the quarterly inspection of the landfill cover system; monitoring of the gas venting system for methane gas; annual inspection of groundwater level monitoring and collection of groundwater samples from selected wells; and an annual ground survey at key cross sectional locations throughout the landfill during the first three years of the post-closure period to monitor the landfill surface slope and potential settlement impacts.

Cover System Inspection

The cover system consists of the following three types of 24-inch barrier protection surface layers:

Type 1

2 inches asphalt concrete top course 5 inches asphalt concrete base course 17 inches clean fill

6 inches recycled concrete 18 inches clean fill

6 inches topsoil with a vegetative cover 18 inches clean fill

The landfill cover system is inspected for asphalt pavement cracks, surface material erosion, erosion of vegetative cover, and areas of surface settlement. The results of the inspections are reported in the Post-Closure Checklist Reports which are generated by the Town quarterly. The Towns most recent quarterly checklist dated September 2006 indicated that several of the paved, recycled concrete and vegetative cover arcas of the landfill cap have developed surface cracks

(i.e., ruts). Further, three areas were identified where pooling of water occurs after rainfall. The pooling does not currently indicate a concern for the cap, but should be monitored. During the site inspection on November 21,2006, it was observed that the surface cracks had been sealed.

Drainage System Inspection

The storm water drainage system consists of perimeter drainage ditches which collect storm water runoff from the Landfill and transmit it to storm drains which discharge into three Nassau County recharge basins. The perimeter drainage ditches consist of rip-rap lined and asphalt- lined perimeter collection ditches that intercept runoff at the foot of the landfill.

The Town's most recent quarterly checklist, dated September 2006, indicated that the majority of the rip-rap lined drainage ditches have been filled with silt and are over vegetated. However, during the site inspection on November 21,2006, it was observed that the drainage ditches had been cleared of all vegetation and silt material.

Gas Venting System Inspection and Methane Monitoring

The landfill gas venting system consists of 38 property line gas vent wells, 16 perimeter gas vent wells, and 26 landfill ridge gas vent wells. Each ridge vent well is protected by a six-foot diameter concrete ring. Inspection of the gas vents revealed that the upper portion of one of the property line gas vents was detached from the well casing pipe. The Town's most recent quarterly checklist, dated September 2006, indicated that the concrete rings that protect four of the ridge vent wells have been damaged and arc in need of repairs. In addition, one ring contained trash that could attract vectors and two of the ridge wells are abutting stockpiled materials which could cause future damage to the ring. However, during the site inspection on November 21,2006, the concrete ring containing the trash had been cleared and stockpiled materials next to the two ridge wells were moved to another location.

The gas vents are monitored for methane gas on a quarterly basis in accordance with the requirements of the O&M Manual to determine compliance with 6 NYCRR Part 360 provisions for levels of combustible gas. The O&M manual stipulates that if monitoring indicates the existence of combustible gas in excess of the lower explosive limit (i.e., 5% gas-in-air) within the property line gas vent, subsurface borehole monitoring for methane gas must be conducted at the property line. As noted in the most recent quarterly report, no methane gas was detected in any of the vents.

Groundwater Elevation Level Monitoring

Water levels within the aquifer fluctuate seasonally. Based on the results of the groundwater level elevation monitoring, the direction of groundwater flow has not changed since the R1.

Groundwater Quality Monitoring

The Town is required to perform annual groundwater sampling at the Site to track groundwater flow and quality conditions to ensure that the landfill continues to be protective of human-health and the environment.

Currently, long-term monitoring data indicate that the landfill is not a significant source of VOCs to the groundwater. The Syosset Landfill, 2005 Annual Post-Closure Groundwater Monitoring Report detected four VOCs in three of the five on-site downgradient wells (SY-2D, SY-3, SY- 3D) above the detection limits but below their respective guidance values (e.g., maximum contaminant levels [MCLs], NYSDEC water quality regulation [WQR], etc.). All other VOCs were below detection limits. These results suggest that groundwater quality immediately downgradient of the Landfill is continuing lo improve with time. The 2005 monitoring information appears consistent with the monitoring conducted in previous years.

The 2005 Report found VOCs in one off-site downgradient well (PK-101). With the exception of chlorobenzene, which was detected at a concentration of 10 micrograms per liter (ugll), the concentrations of the other VOCs were below their respective standards. Table 4 provides a comparison of the detections above standards, well location, and standards.

The 2005 Report also found non-site related VOCs in two off-site downgradient wells (RW-121 and RW-12D, see Table 5). Contaminants exceeding their respective standards include vinyl chloride, I ,I -dichloroethane, cis-l,2-dichloroethene, benzene, 1,2-dichloroethane, trichloroethylene, tetrachloroethene, chlorobenzene, 1,4-dichlorobenzene, and 1,2- dichlorobenzene. These results are consistent with the conclusions from the 1996 ROD that identified these VOC contaminants as not related to the Site, as described in the following quote from the ROD:

"... The VOC concentrations detected in oJjsite monitoring wells, with the exception of R W-I2I. during the 0U2 RI were found to be consistent with regionally degradedgroundwater quality.

Contaminant levels in groundwater would normally be expected to be higher at a source (Landfill) and lower at any downgradient location. This was not the case with RW-121. C . ,wen the fact that R W-121 is located at the westernmost edge ofthe landfill, and adjacent to an industrial area located west ofthe Long Island ailr road tracks the VOCs detected in this well may be derivedfrom a source other than the Landfill. An Industrial Survey was performed to determine ifpotential sources of VOCs exist in the vicinity of the landfill. The Industrial Survey identtifiedfive off-site properties which' may be polenlial sources of the VOCs detected in Well R W-121. These properties are located on Robbins Lane and Aerial Way, between 1,400 and 2,1 00 feet southwest of Well R W-121. Based on the resultsj~om the survey, it was found that each of these properties used one or more ofthe VOCs detected in the RW-I21 Well. Regional hydrogeologic data suggests that the potential off-site sources ident13ed in the industrial survey are located hydraulically upgradient of Well R W-121 and may have impacted the well ... "

Metals were also identified in on-site and off-site wells above standards. A summary of this data is provided in Table 5. Arsenic was identified above the federal MCL of 10 ugll in wells SY-3 and SY-3 at concentrations of 28.7 and 22.6 ug/l, respectively. Iron was also identified in site wells at concentrations above the New York State Water Quality Standard (300 ug/l) and EPA's Secondary Standard of 50 ug/l. However, the upgradient well (SY-6) had concentrations of 9,220 ug/l and the concentrations of the on-sitc wells ranged from 1,230 ug/l (in well SY-2D) to 14,100 ugll (in well SY-3). This suggests there may be a regional problem. In addition, manganese was also identified above the State Watcr Quality Standard of 300 ug/l in wells SY- 2D (859 ugll), SY-3 (1,690 ugil), SY-3D (1,430 ugll) and SY-5 (1,410 ugil). However, upgradient well SY-6 identified concentrations of 11 1 ugll. Other metals detected included chromium and nickel.

Sire Inspection

The Site was inspected by the RPM, the hydrogeologist, and the risk assessor onNovember 21, 2006. The inspection team also included representatives from the Town and its consultants.

No interviews were conducted for this review.

Institutional Controls Verification andEffictiveness

The Site is owned by the Town, used by the Town, and the Town restricts access. The Town has given EPA a copy of restrictive covenants placed on the real property at the Site by the Town which was filed with the land records on March 23,2004. No further verification or review of institutional controls effectiveness was considered necessary at this time.

Other Comments on Operation, Maintenance, and Institutional Controls

Table 7 (attached) summarizes several observations and offers suggestions to resolve these issues.

VIZ. Technical Assessment

Question A: Is the remedy functioning as inlended by /he decision documenfs?

The primary objective of the implemented remedy is to control the source of contamination at the Site, to minimize the migration of contaminants into the groundwater, and to minimize any potential human health risks resulting from the exposure to contamination at the Site. This objective was accomplished by the installation of the landfill cap (OUI) and the implementation of a ground water monitoring program (OU2).

In general the landfill cap is well-maintained, mowed, and operating as designed. Data continue to indicate no detections of VOCs or low detections below the applicable or relevant and

12

appropriate requirements (ARARs), except in one off-site well that detected VOC contaminants found not to be associated with the Landfill. Table 4 shows contaminants detected during the 2005 annual groundwater monitoring. Based on review of the documents and site inspection, the remedy is functioning as intended by the ROD; thus, the remedy has remained protective.

Quesfion B: Are the exposure assumpfions, toxicity data, cleanup levels, and remedial action objectives used at the time of the remedy still valid?

There have been no changes in the physical conditions of the Site over the past five years that would change the protectiveness of the remedy. The entire landfill is currently fenced including a locked gate and guards to prevent entry onto the site. Access to the site and potential exposures are limited by the current on-going use of the facility for sanitation and highway activities that prevent trespassing.

Soil and groundwater use at the Site are not expected to change during the next five years, the period of time considered in this review. The risk assessment identified arsenic as the Chemical of Concern for the site based on groundwater ingestion. Several other volatile organic compounds and metals were identified in the 1990 risk assessment (e.g., vinyl chloride, benzene, toluene, and xylene) but they did not exceed the risk range. The risk assessment evaluated potential exposures to public workers at the site, children and faculty at the nearby school, community residents, and trespassers. Accidental ingestion and direct contact with contaminated groundwater were identified as potential health exposure pathways of concern. At the current time, residents obtain their drinking water from a municipal supply that meets appropriate standards.

The risk assessment considered the land use industrial. The current and anticipated future use of this property is not expected to change from industrial. Direct contact exposures at the site were intenupted through the installation of the Part 360 cover. The capping of the landfill with a barrier cap intenupts potential ingestion and direct contact with contaminated soil. The fence around the Site limits potential direct contact by trespassers. Institutional controls, in the form of deed restrictions, have been implemented to further restrict development of the site and maintain the cap and industrial land use designation. Potential exposures to methane gas have also becn addressed through the establishment of a passive gas system on the landfill.

The 2005 Annual Post-Closure Groundwater Monitoring Report indicates concentrations of arsenic above the current MCL of 10 pgll. The MCL for arsenic was exceeded on-site at monitoring wells SY-3, SY-3D, and SY-5, at concentrations of 28.7 pgll, 22.6 pgll and 18.0 pgll, respectively. Other groundwater samples for arsenic on-site and off- site were below the MCL. At the current time, the groundwater at the Site is not being used for ingestion and the exposure pathway has been interrupted. Residents in the community receive drinking water from municipal supplies. The ROD established the federal MCLs and New York State Department of Environmental Conservation Water Quality Regulations (WQR) as the cleanup criteria for the groundwater contaminants of concern. Table 6 compares the maximum concentration of arsenic found in groundwater at the site with the EPA Region 9 Preliminary Remediation Goals assuming residential exposures for children and adults over a 30 year period based on future groundwater use. The toxicity data from arsenic were updated in 1998 after the Risk Assessment and Records of Decision were signed. The changes in toxicity values do not impact the

protectiveness of the remedy. At the current time, arsenic is being reassessed through the Agency's Integrated Risk Information System, the Agency's consensus database for toxicity information. It is recommended that arsenic be evaluated at the next 5 year review.

Soil vapor intrusion was not further evaluated based on the recommendation in the "2002 OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soil (EPA530-D-02-004)" that indicates where contaminants are found at depths greater than 100 feet, evaluation of soil vapor intrusion is not appropriate. The wells evaluated in this assessment were screened at depths greater than 100 feet. In addition, the primary chemical of concern, arsenic, is not volatile. In addition, the cap design includes a gas venting layer that includes one vent per acre.

Overall, based on the past remedial actions, ongoing monitoring, and maintenance of the landfill cap, the remedy remains protective.

Question C: Has any other information come to light that could call into question the prolectiveness ofthe remedy?

There is no information that calls into question the protectiveness of the remedy.

Technical Assessment Summary

Based upon the results of this second Five-Year Review process, it has been concluded that the remedy is hnctioning as intended by the Site's remedial decision documents. The specific points are as follows:

. The cap is intact and in generally good condition; . The fence around the Landfill is intact and in good repair; . The monitoring wells required for O&M are securely locked and functional; and . There is no evidence of trespassing or that vandalism has occurred.

VZII. Issues, Recommenrlntions and Follow-up Actions

The selected remedy, described in the two RODS, has been fully implemented. There are ongoing operation, maintenance, and monitoring activities included in the selected remedy. As was anticipated by the decision documents, these activities are subject to routine modification and adjustment. Table 7 includes suggestions for improving, modifying andlor adjusting these activities. New York State requires annual certifications that institutional controls are in place and that remedy-related O&M is being performed. Annually, the potentially responsible parties will need to certify that the existing institutional controls remain in place and that remedy-related O&M is being performed.

ZX. Protectiveness Statement

The implemented remedy for the Syosset Landfill Superfund Site protects human health and the environment. There are no exposure pathways that could result in unacceptable risks and none expected as long as the site use remains consistent with the site's access and institutional controls and those controls are properly monitored and maintained.

X . Next Review

The next Five-Year Review for the Site will be completed before January 201 1, five years from the date of this review.

Approved:

Pavlou, Director Emergency and Remedial Response Division

1-157-0 7 Date

Table 1 : Chronology of Site Events

2001 -November

Table 2: Estimated Annual Monitoring Costs

Sampling and Analysis ...................................................................................................... $50. 000

Site Inspection and Maintenance ........................................................................................ $75. 000

Total Estimated Annual Monitoring Costs .......................................................................... $125. 000

Table 3. List of Documents Reviewed

The following documents were reviewed in completing the second Five-Year Review:

Interim Remedial Investigation Report, August 1989; Record of Decision for OU1 (Landfill), September 1990; Record of Decision for 0 U 2 (Groundwater Study), March 1996; Annual Operation and Maintenance Summary Report for 2003; Annual Operation and Maintenance Summary Report for 2005; Annual Operation and Maintenance Groundwater Monitoring Report for 2005; Post-Closure Checklist Reports; and EPA Guidance for conducting Five-Year reviews.

Table: - VOCs results from the AnnualMoniloring Reports detected in on-site moniloring wells compared to Primary Drinking Water Standard (Maximum Contaminant Leve[) and New York Deparlment of Environn~enlal Conservation Ambient Water Qualify Standards and Guidance Values Rqulalions (NYSDEC WQR).

I I I I I I I

VOCs

chlorobenzene

Vinyl chloride

Cis- l,2-dichloroethane

Benzene

1,2-dichloroethane Trichloroethene

Tetrachloroethene

1,4-dichlorobenzene

1,2-dichlorobenzene

Primary Drinking

Water Standard -

MCL

NYSDEC WQR

(ug/l)

Footnotes: Contaminants detected in the RW-121 and RW-12D were found not to be from the Landfill

PK- 101 (ug/l)

RW-121 (ug/l)

RW-12D (u!dl)

-5 : -Metals results from the 2005 Annual Monitoring Report detected in on-site monitoring wells compared to Primary Drinking Water Standard (Maximum Conlamutant Level) and New York Department of Environmental Couservaiion Ambient Water Qualily Standards and Guidance Values Regulations (NYSDEC WQRA

I 1 I I

I On-site Wells / Off-site Wells

vocs (ugll)

arsenic

Drinking Water

Standard - MCL (uzfl)

10

manganese

i ron

Chromium I I Mercury 1 2

1 I 1 I 1 I I I

Footnotes: Values are National Secondary Drinking water regulations, which are non-enforceable guidelines regulating contaminants that may cause cosmetic or aesthetic effects in drinking water.

300

3 00 50

50 * 300 * 100

1 0.7 I I I I I I I I I

NYSDEC WQR

( ~ g / l )

1 0.90

Nickel

80.2

4,080

SY-2R

1 100

1,900

1,230

1317

MW SY-2D

1,660

14,100

MW SY-3

28.7

1,480

9,180

MW S Y 3 D

22.6

1,360

1,610

PK- IoS

61.1

PK-I01 PK-

Footnotes: C: Value is based on a Cancer endpoint

Table: - Comparison of the On-Site maximum concentration of arsenic detected in the on-site monitoring wells to the respective human health risk based screening criteria (Preliminary Remediation Goal), Primary Drinking Water Standard (Maximum Contaminant Level) and New York Department of Environmental Conservation Water Quality Regulations (NYSDEC WQR).

Source: Region 9 Preliminary Remediation Goals (PRGs) are human health risk based screening criteria. These values are equivalent to a cancer risk of 1 x lo4 or a hazard index of 1. Refer to: htt~:llw.epa.qovlReqion9/wastelsfundl~rqlindex.htm

Metals (mgll)

Arsenic

National Drinking Water Standards (MCLs) are legally enforceable standards that apply to public water systems. Refer to: http:llwww.epa.qovlcqi-binlepaprintonlv.c@

New York State Department of Environmental Consewation Water Quality Regulations (NYSDEC WQR) are the ARARs established in the ROD. Refer to: http:/lwww.dec.state.nv.us/websitelreqslpart703.html

Region 9 Preliminary Remediation

Goal

@dl) 0.045

Groundwater ~ ~ ~ i ~ ~ r i ~ ~

Report

2005

Maximum Detected

Concentration

@dl) 28.7

Primary Drinking

Water Standard -

MCL

10

NYSDEC

WQR (udl)

25

Location

SY-3

Table 7: Other Comments on Operation, Maintenance, Monitoring, and Institutional Controls

Comment

Monitoring Well SY-6D was reported to be damaged and obstructed.

Monitoring Well SY-7 could not be located during the annual groundwater monitoring event. The general area of the well is known, and it is believed to have been paved over.

Monitoring Well SY-9 has frequently been "dry" and unable to be sampled. It does not have a sufficiently deep screen interval to be useful.

Suggestion

Monitoring Well SY-6 should formally be designated the sampling location instead of Monitoring Well SY-6D which should be formally abandoned in accordance with NYSDEC requirements.

The well should be located and repaired.

This Well should be formally abandoned in accordance with NYSDEC requirements and be removed from the sampling program. .