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TABLE OF CONTENTS

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EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

SECTION 1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

SECTION 2.0 SITE CHRONOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

SECTION 3.0 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.1 Physical Characteristics and Land and Resource Use . . . . . . . . . . . . . . . . . . . . . . . . 33.2 History of Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.3 Initial Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.4 Basis for Taking Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

SECTION 4.0 REMEDIAL ACTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.1 Remedy Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.1.1 Operable Unit 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.1.2 Operable Unit 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.2 Remedy Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.3 System Operations/O&M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

SECTION 5.0 FIVE-YEAR REVIEW PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125.1 Community Notification and Involvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125.2 Document Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135.3 Data Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.3.1 Groundwater Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135.3.2 Surface Water Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155.3.3 Air Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.4 Site Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.5 Interviews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

SECTION 6.0 TECHNICAL ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.1 Question A: Is the remedy functioning as intended by the decision documents? . . . . 176.2 Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial

action objectives (RAOs) used at the time of the remedy still valid? . . . . . . . . . 186.2.1 Review of Risk Assessments and Toxicity Factors Serving as the Basis forthe Remedy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.2.2 Changes in Exposure Pathway and Risk Assessment Methods . . . . . . . . . 19

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TABLE OF CONTENTS (Cont’d)

Page6.2.3 Changes In Standards and TBCs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206.2.4 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3 Question C: Has any other information come to light that could call into question theprotectiveness of the remedy? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

SECTION 7.0 ISSUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

SECTION 8.0 RECOMMENDATIONS AND FOLLOW-UP ACTIONS . . . . . . . . . . . . . . . . 22

SECTION 9.0 PROTECTIVENESS STATEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

SECTION 10.0 NEXT REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

TABLES

Table 1 Chronology of Site EventsTable 2 IssuesTable 3 Recommendations and Follow-up Actions

ATTACHMENTS

Attachment 1 Site Maps and Construction PhotographsAttachment 2 List of Documents Reviewed

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LIST OF ACRONYMS AND ABBREVIATIONS

ACRONYM DEFINITION

AOC Area of Containment

ARAR Applicable or Relevant and Appropriate Requirement

C&P Cardboard and Paper

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CFR Code of Federal Regulations

COPC Contaminant of Potential Concern

EMP Environmental Monitoring Plan

ERA Ecological Risk Assessment

FAWQC Federal Ambient Water Quality Criteria

FS Feasibility Study

HHRA Human Health Risk Assessment

MCL Maximum Contaminant Level

MNA Monitored Natural Attenuation

NCP National Contingency Plan

NPL National Priorities List

O&M Operation and Maintenance

OU1 Operable Unit 1

OU2 Operable Unit 2

PAH Polycyclic Aromatic Hydrocarbon

PCB Polychlorinated Biphenyl

RA Remedial Action

RAC Remedial Action Contract

RAO Remedial Action Objective

RCRA Resource Conservation and Recovery Act

RI Remedial Investigation

RIDEM Rhode Island Department of Environmental Management

RIRRC Rhode Island Resource Recovery Corporation

ACRONYM DEFINITION

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RISWMC Rhode Island Solid Waste Management Corporation

RD Remedial Design

ROD Record of Decision

SVOC Semivolatile Organic Compound

TSDF Transportation Storage and Disposal Facilities

VOC Volatile Organic Compound

USEPA United States Environmental Protection Agency

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EXECUTIVE SUMMARY

The Central Landfill Superfund Site (the Site), located in Johnston, Rhode Island, consists of twooperable units, Operable Unit 1 (OU1) and Operable Unit 2 (OU2). The Site is a 154-acrelicensed landfill in the central portion of a 610-acre parcel owned by the Rhode Island ResourceRecovery Corporation (RIRRC). OU1 addresses source control of contamination at the Site andOU2 addresses off-Site migration of contamination.

The selected remedy identified in the Record of Decision (ROD) for OU1 includes construction ofa multi-layer RCRA C cap; hydraulic containment and treatment of “Hot Spot” groundwater;implementation of deed restrictions on groundwater use and land development within the RIRRCproperty; long-term sampling of groundwater, surface water, and air; a detailed evaluation of theexisting landfill gas collection and combustion system; and installation of a chain link fence toprevent access.

The human health and ecological risk assessments conducted as part of the OU2 investigations didnot show any risks that warrant action under Superfund. The OU2 ROD concluded that nofurther actions were necessary other than those required by the OU1 ROD.

The trigger for this statutory review is the start of actual remedial action (RA) on-Siteconstruction at OU1 on August 31, 1998. This review is required by statute because the selectedremedy for OU1 results in hazardous substances remaining on-Site above health based levels.

The five-year review concludes that the remedy for OU1 is expected to be protective of humanhealth and the environment upon completion, and in the interim, exposure pathways that couldresult in unacceptable risks are being controlled. Institutional controls and access restrictions arein place and are successfully preventing exposures.

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Five-Year Review Summary Form

SITE IDENTIFICATION

Site name (from WasteLAN): Central Landfill

EPA ID (from WasteLAN): RID980520183

Region: 01 State: RI City/County: Johnston/Providence County

SITE STATUS

NPL status: : Final G Deleted G Other (specify)

Remediation status (choose all that apply): : Under Construction G Operating G Complete

Multiple OUs?* : YES G NO Construction completion date: __ / _/ _

Has site been put into reuse? G YES : NO

REVIEW STATUS

Lead agency: : EPA G State G Tribe G Other Federal Agency

Author name: James M. Brown

Author title: Remedial Project Manager Author affiliation: U.S. EPA

Review period:** 7 / 1 / 2003 to 9 / 30 / 2003

Date(s) of site inspection: Ongoing during construction.

Type of review:: Post-SARA G Pre-SARA G NPL-Removal onlyG Non-NPL Remedial Action Site G NPL State/Tribe-leadG Regional Discretion

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

Triggering action:: Actual RA Onsite Construction at OU1____ G Actual RA Start at OU#____G Construction Completion G Previous Five-Year Review ReportG Other (specify)

Triggering action date (from WasteLAN): 08 /31 /1998

Due date (five years after triggering action date): 08 /31 /2003* [“OU” refers to operable unit.]** [Review period should correspond to the actual start and end dates of the Five-Year Review in WasteLAN.]

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Five-Year Review Summary Form, cont’d.

Issues:

The 30% design for the Hot Spot Groundwater Containment and Treatment System has beenstarted but has not been completed. Not all the interim cap construction punch list itemshave been completed. The evaluation of the landfill gas collection and combustion system hasstarted but has not been completed.

Recommendations and Follow-up Actions:

The RIRRC needs to complete the 30% design for the Hot Spot Groundwater Containmentand Treatment System, punch list items and the evaluation of the landfill gas collection andcombustion system..

Protectiveness Statement(s):

The remedy for OU1 is expected to be protective of human health and the environment uponcompletion, and in the interim, exposure pathways that could result in unacceptable risks arebeing controlled. Institutional controls and access restrictions are in place and aresuccessfully preventing exposures.

Other Comments:

None.

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SECTION 1.0INTRODUCTION

This document is a comprehensive and interpretive report on the five-year review conducted for the CentralLandfill Superfund Site (the Site) in Johnston, Rhode Island. This work was conducted by the EPA withthe assistance of Metcalf & Eddy (M&E) under the Response Action Contract (RAC) (Contract No. 68-W6-0042).

The purpose of this five-year review is to determine whether the remedies for the Central Landfill Site areprotective of human health and the environment. The methods, findings, and conclusions of this review aredocumented in this Five-Year Review report. In addition, Five-Year Review reports identify issues foundduring the review, if any, and recommendations to address them.

EPA Region I has conducted this five-year review pursuant to the Comprehensive EnvironmentalResponse, Compensation, and Liability Act (CERCLA) and the National Contingency Plan (NCP). CERCLA §121 states:

If the President selects a remedial action that results in any hazardous substances, pollutants, orcontaminants remaining at the site, the President shall review such remedial action no less oftenthan each five years after the initiation of such remedial action to assure that human health andthe environment are being protected by the remedial action being implemented. In addition, ifupon such review it is the judgement of the President that action is appropriate at such site inaccordance with section [104] or [106], the President shall take or require such action. ThePresident shall report to the Congress a list of facilities for which such review is required, theresults of all such reviews, and any actions taken as a result of such reviews.

The NCP 300.430(f)(4)(ii) of the Code of Federal Regulations (CFR) states:

If a remedial action is selected that results in hazardous substances, pollutants, or contaminantsremaining at the site above levels that allow for unlimited use and unrestricted exposure, thelead agency shall review such action no less often than every five years after the initiation of theselected remedial action.

The Central Landfill Site consists of two operable units, Operable Unit 1 (OU1) and Operable Unit 2(OU2). This five-year review addresses both operable units.

This is the first five-year review for the Central Landfill Site. This review is required by statute becausethe selected remedy for OU1 and OU2 results in hazardous substances, pollutants, or contaminantsremaining on-Site above health-based levels that would allow for unlimited use and unrestricted exposure. The trigger for this statutory review is the start of actual RA on-Site construction at OU1 on August 31, 1998.

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SECTION 2.0SITE CHRONOLOGY

The chronology of the Site, including all significant Site events and dates is included in Table 1.

Table 1: Chronology of Site Events

Event Date

Part of Site used a sand and gravel quarry/stone operation 1952 through 1955

Site operated as a refuse burning dump 1955 through 1962

Large volumes of liquid industrial wastes disposed of in“Hot Spot” area

mid to late 1970s

EPA issued RISWMC an Administrative Order to producea proposal for monitoring, sampling, testing, analysis, andreporting at the Central Landfill

June 1984

RIDEM an RISWMC enter into Consent Agreements toremedy violations of state Rules and Regulations for SolidWaste Management Facilities

August 1984

Final listing on EPA National Priorities List June 1986

EPA Issues Consent Order to the RISWMC forPerformance of OU 1 RI/FS

April 1987

Completion of Remedial Investigation for OU1 March 1993

Completion of Feasibility Study for OU1 December 1993

OU1 Record of Decision is signed June 17, 1994

Consent Decree entered by Federal Court for OU1 May 16, 1996

100% Final Cap Design approved by EPA November 11, 1997

Start of on-Site construction at OU1 (date that triggers afive-year review)

August 31, 1998

Completion of Remedial Investigation for OU2 March 2001

OU2 Record of Decision is signed September 26, 2002

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SECTION 3.0BACKGROUND

3.1 PHYSICAL CHARACTERISTICS AND LAND AND RESOURCE USE

The Central Landfill Superfund Site (the Site) is a 154-acre licensed landfill in the central portionof a 610-acre parcel at 65 Shun Pike, Johnston, Rhode Island, Providence County (see Figure 1,provided in Attachment 1 of this report). The Central Landfill is an active waste disposal facilityand is the largest waste disposal facility in Rhode Island, servicing the majority of communities inthe state. Central Landfill is owned by the Rhode Island Resource Recovery Corporation(RIRRC) [formerly the Rhode Island Solid Waste Management Corporation (RISWMC)].

The Central Landfill Superfund Site consists of two operable units, Operable Unit 1 (OU1) andOperable Unit 2 (OU2). OU1 deals with source control of contamination at the Site and OU2addresses off-site migration of contamination.

For OU 1 purposes, the Site is comprised of two areas: a 121-acre area known as the Phase I areaand a 33-acre expansion area known as the Phase 2 and 3 areas. The RIRRC has also expandedinto a 44-acre expansion area known as Phase 4, which is located south of the Phase 2 and 3 areas(see Figure 2, provided in Attachment 1 of this report).

The OU2 study area consisted of a 1,333-acre area that surrounds, but does not include the Site. Areas surrounding the Site are either undeveloped, residential, or commercial/industrial. RIRRCoperations at the property other than landfilling are located primarily east-southeast of the Siteand include a vehicle maintenance facility, materials recycling facility, and a landfill gas-to-energyplant. Businesses, not owned by RIRRC, within the OU2 study area, include a screw machineproducts manufacturer, a commercial welder, a demolition contractor, vehicle repair shop, refusetransfer station, cardboard and paper (C&P) recycling operation, refuse hauling company, and aformer hazardous waste/oil Transportation Storage and Disposal Facilities (TSDF) business. Residential properties within 2,000 feet of the Site were acquired by RIRRC. This propertyacquisition was primarily to the north and east along Bishop Hill Road, Central Avenue, andScituate Avenue. Homes within the acquisition area along Simmons Lake Drive (hydro-geologically downgradient of the Site) have all been demolished (USEPA, 2002).

The Upper and Lower Simmons Reservoirs are located southeast of the Site and were also part ofthe OU2 study area. The Almy Reservoir, located northeast of the Site, was also included as partof the OU2 study area. These reservoirs are designated as Class B surface waters by the RhodeIsland Department of Environmental Management (RIDEM), which means that they aredesignated for fish and wildlife habitat and recreational activities. The majority of thegroundwater within the OU2 study area has been classified by RIDEM as GA (suitable fordrinking water without treatment) or GA-NA (non-attainment). The groundwater below the Siteis classified as GC - suitable for certain waste disposal purposes (USEPA, 2002).

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The 610-acre property owned by RIRRC is partially fenced and vehicular entry is limited tosecured roadways. Security guards patrol the property 24 hours/day (USEPA, 2002).

Future land uses within the RIRRC-owned property is not likely to change significantly.

3.2 HISTORY OF CONTAMINATION

The Central Landfill has been owned and operated by the RIRRC since 1980. Prior to 1980, theSite was owned by the Silvestri Brothers. From 1952 to 1955, a portion of the Site was used as acombination sand and gravel/quarry stone operation. From 1955 to 1962, the Site was operatedas a refuse burning dump. The Site has been used as a solid waste disposal area since 1962(USEPA, 2002).

During the mid to late 1970's, an approximate 0.5 acre area, located within the Phase I area, wasused for disposal of large volumes of liquid industrial waste by the Silvestri Brothers. This area isreferred to as the Hot Spot (USEPA, 2002).

According to RIDEM waste manifests, industrial wastes were accepted and disposed of in theHot Spot during the period of December 3, 1976 through May 30, 1979. Between January 1978and May 1979, Industrial Waste Manifests were submitted to the RIDEM. The manifests indicatethat wastes disposed of at the Site include aqueous solutions of latex waste, acid waste, corrosivewaste, water soluble oils, and waste solvents such as methylene chloride, toluene, 1,1,1-trichloroethane, and tetrachloroethylene. Limited information was available concerning the typesand quantities of wastes that were disposed of prior to January 1978 because neither federal norstate hazardous waste regulations were in effect at that time (USEPA, 2002).

Between May 1979 and February 1981, approximately 5 to 10 acres in the northeast portion ofthe Site received large volumes of untreated liquid sewerage sludge. That area was subsequentlycovered with about fifteen feet of landfill debris and daily soil cover. Since 1980, the wastestream has been as high as 6,000 tons per day. In 1991, solid waste disposal averagedapproximately 2,500 tons per day (USEPA, 2002).

On August 10, 1984, and again on August 28, 1984, RIDEM and RISWMC entered into ConsentAgreements to remedy violations of the state Rules and Regulations for Solid Waste ManagementFacilities. The August 10 Agreement addressed several solid waste violations including the needfor a closure plan for the entire Site. The August 28 Agreement addressed the concerns of theNovember 9, 1983 Notice of Violation.

In 1984, the Site was proposed for inclusion on EPA’s National Priorities List (NPL). In June1984, EPA issued an Administrative Order to RISWMC pursuant to the authority granted EPAunder Section 3013 of the Resource Conservation and Recovery Act (RCRA). The Orderrequired RISWMC to produce a proposal for monitoring, sampling, testing, analysis, andreporting at the Central Landfill. The Order was based on EPA’s determination that the landfillmay have presented a substantial hazard to human health and the environment.

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The Site was added to the NPL in June 1986 (USEPA, 2002).

3.3 INITIAL RESPONSE

In 1986, RIRRC (formerly the RISWMC), in conjunction with the RIDEM and the Town ofJohnston initiated a project to provide public drinking water to area residents. The project wascompleted in 1990. A 12-megawatt landfill gas to electricity facility has been constructed at theSite and has been in operation since 1990. RIRRC expended approximately $23,000,000acquiring residentially zoned property located within 1,000 feet of the licensed landfill area andoffered residents within the next 1,000 feet the option of selling their property to the RIRRC. This property acquisition was mandated by the Rhode Island Legislature.

After the Site was listed on the NPL, the EPA and RIRRC entered into a Consent Order toperform a remedial investigation and feasibility study (RI/FS) in April 1987. Field work for theOU1 RI began in January 1986 and was completed in November 1991. The RI was completed inMarch 1993. During the field investigations, the project was divided into Operable Units 1 and 2. The FS for OU1 was completed in December 1993.

Field work for the OU2 RI was conducted between June 1992 and July 1998 and also inDecember 2000. The OU2 RI, including the baseline risk assessment report, was completed inMarch 2001.

3.4 BASIS FOR TAKING ACTION

The following summarizes the contaminants detected as part of the OU 1 RI at the Site:

Groundwater. Several volatile organic compounds (VOCs), semivolatile organic compounds(SVOCs), and inorganics were detected in groundwater samples collected around the perimeter ofthe landfill area. Groundwater in the vicinity of the hot spot area contained much higher levels ofVOCs and SVOCs. Groundwater samples from wells close to the 610 acre property line containonly slightly elevated levels of a few VOCs, SVOCs, and inorganics.

Soil. VOCs, SVOCs, pesticides, and metals were detected in locations downgradient of the Site. Compounds that were considered contaminants of potential concern (COPCs) for the humanhealth risk assessment included several polycyclic aromatic hydrocarbons (PAHs) and metals.

Sediment. VOCs, SVOCs, pesticides/polychlorinated biphenyls (PCBs), and metals weredetected in samples from locations in the Almy and Upper Simmons Reservoirs, Cedar SwampBrook, Quarry Stream, associated wetlands areas, and four landfill Sedimentation Ponds. Compounds that were considered COPCs included several PAHs and metals.

Surface Water. VOCs, SVOCs, pesticides/PCBs, and metals were detected in samples fromlocations in the Almy and Upper Simmons Reservoirs, Cedar Swamp Brook, Quarry Stream,

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associated wetlands areas, and four landfill Sedimentation Ponds. Compounds that were considered COPCs included one VOC, one pesticide, and several metals.

A human health risk assessment (HHRA) was performed for the Site in 1993 by CDM FederalPrograms Corporation (CDM FPC, 1993). The risk assessment concluded that there were nocomplete exposure pathways for human receptors under present Site conditions but there wereunder future use conditions. The OU1 HHRA concluded that there were no significant risksassociated with exposure to estimated future concentrations in the surface waters of the UpperSimmons and Almy Reservoirs. However, the HHRA indicated that there was insufficient data tocompletely characterize the human health risks associated with recreational use of these two waterbodies. The OU1 HHRA concluded that there is potential future risk to human health fromingestion and dermal contact of groundwater beyond the toe of the landfill but within the RIRRC-owned property. The source of this groundwater contamination was determined to be the 121-acre Phase I area of the Central Landfill. These conclusions formed the basis of the selectedremedy for OU1 which focused on controlling the source of groundwater contamination.

The HHRA for OU2 concluded that contaminants present in soil, surface water, and sedimentwithin the OU2 study area and groundwater outside of the RIRRC-owned property do not pose asignificant risk to human health. The HHRA assumed that residents downgradient of the Sitewere not and will not be using groundwater as a drinking water source, since institutional controlswere required as part of the OU1 remedy to prohibit use of the groundwater. The EcologicalRisk Assessment (ERA) performed for OU2 concluded that there is no significant risk to aquaticbiota including fish, planktonic and epiphytic organisms, and benthic organisms in the Upper andLower Simmons Reservoirs from contaminants present in surface water and sediments. Also,there are no significant indirect impacts to fish and wildlife, which depend on those species forfood. These determinations were the basis of the no further remedial action decision for OU2.

SECTION 4.0REMEDIAL ACTIONS

4.1 REMEDY SELECTION

This section outlines the selected remedies for Operable Units 1 and 2.

4.1.1 Operable Unit 1

The EPA Record of Decision (ROD) for Central Landfill OU1 was signed on June 17, 1994. Theremedial action objectives (RAOs) listed in the ROD are:

• Minimize the effects of landfill contaminants on groundwater quality; specifically, reduceto a minimum the amount of precipitation allowed to leak through the waste column andinfiltrate to the groundwater;

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• Eliminate future risks to human health through direct contact with landfill contaminants bymaintaining a physical barrier;

• Minimize migration of contaminants in groundwater so that groundwater is not injuriousto the aquatic ecological system of receiving water bodies (Upper Simmons Reservoir,Cedar Swamp Brook, and Almy Reservoir);

• Minimize risks to human health associated with potential future consumption of and directcontact with groundwater;

• Comply with state and federal applicable or relevant and appropriate requirements(ARARs); and

• Minimize potential impacts of implementing the selected source control alternative onadjacent surface waters and wetlands.

The selected source control remedy for Central Landfill OU1, as identified in the ROD, consistedof the following components:

• Constructing a multi-layer RCRA C cap over the existing 121-acre Phase I area andincorporating the existing 32 acres of RIDEM approved cap on the side slopes;

• Hydraulic containment and treatment of groundwater in the Hot Spot area of the landfilland discharging the treated groundwater to either on-site surface water or the CranstonWaste Water Treatment Plant;

• Implementing deed restrictions on groundwater use and land development within propertyowned by the RIRRC ;

• Initiating a long-term program of sampling and analysis of groundwater, surface water,and air;

• Conducting a detailed evaluation of the existing landfill gas collection and combustionsystem;

• Installing a chain link fence to prevent access; and

• Conducting five year reviews.

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4.1.2 Operable Unit 2

The ROD for Central Landfill OU2 was issued by EPA in September 2002. The ROD concludedthat because the baseline risk assessments for OU2 revealed no unacceptable human health orecological risks related to the Site, no further remedial actions other than those required by theOU1 ROD were necessary.

4.2 REMEDY IMPLEMENTATION

In a Consent Decree entered on May 16, 1996, the RIRRC agreed to perform and pay for theRemedial Design/Remedial Action (RD/RA) and operation and maintenance for the CentralLandfill Site.

The design and implementation of the remedial actions for OU1 are discussed below, bycomponent, as identified in the ROD. The remedial actions have not yet been completed.

Construction of the Landfill Cap

Four preliminary investigations were conducted to obtain supplementary information needed forthe landfill cap design including a site survey, verification of Record Drawings for the existingcap, geotechnical investigation, and mapping of leachate seeps. Following the completion of theinvestigations, RIRRC conducted the design of the landfill cap in 1996 and 1997. The 100%Final Cap Design Report was submitted on August 1, 1997 and was approved by EPA onNovember 3, 1997. A 100% Cap Design Addendum was approved by EPA on November 11,1997 (USEPA, 2002).

The RIRRC entered into a contract with ENSR Construction Services (ENSR) in August 1998 toperform capping activities in the Phase I area (approximately 88 acres of new capping). The 88acre capping project is comprised of five areas (areas 3, 4, 5, 6 & 7). Areas 1 and 2 (33 acrestotal) are currently capped with a RIDEM approved cap that is being incorporated into the newcap (see Figure 2).

ENSR mobilized in August 1998 and began placement of the cap in Area 3 (approximately 15acres) in September 1998. ENSR was not able to complete the cap in Area 3 prior to wintershutdown. Incomplete items included drainage swales, Area 3 downchute and permanentvegetation over completed cap areas. Areas where construction was not complete were stabilizedduring the winter shutdown and construction picked up in Spring 1999. In January 2000, ENSRcompleted construction for the remainder of Area 3 and approximately half of Area 4 (10.5 acres,now referred to as Area 4 – North). Following completion of Area 3 and Area 4 – North theRIRRC terminated its contract with ENSR. The RIRRC bid the remaining portion of Area 4 inApril 2000 and entered into a contract with C. Pezza & Sons, Inc. (Pezza) to complete theremaining portion of Area 4 in June 2000.

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In July 2000, Pezza commenced work on landfill cap placement in Area 4- South (approximately11 acres), as well as completing various punchlist tasks identified in Area 4 – North at the end ofthe 1999 construction season. Pezza was unable to complete all work in Area 4 during the 2000construction season and suspended work in December 2000. Once again the uncompleted areaswere stabilized during the winter shutdown. A relatively new product known as Eco-Aegis wasapproved for application on the landfill to protect disturbed areas over the winter shutdown. This product, consisting of mulch, tacifier, seed and fertilizer, proved beneficial as an alternativemethod of protecting uncompleted areas and also for filling in areas that were previously seededbut showed sparse or no growth.

Pezza returned in Spring 2001 to complete placement of the landfill cap in Area 4 – South. M&Eoversight engineers along with the Louis Berger Associates (LBA) quality assurance manager andrepresentatives of the RIRRC and their engineering consultant, Pare Engineering Corporation(Pare) prepared a punchlist consisting of cap-related items in Areas 3 & 4 requiring additionalwork to comply with the approved landfill cap plans and specifications. Pezza completed severalof these items prior to the end of their contract in November 2001, with the RIRRC agreeing tocomplete the remainder.

In August 2001, the RIRRC notified EPA that they would be continuing solid waste landfillingactivities in Phase II areas that overlap areas 5 and 6 and 7 of the Phase I area. Landfillingactivities in these areas of Phase II continued until the summer of 2003. In accordance with the1996 Consent Decree, RIRRC installed an Interim Impermeable Barrier (Interim Cap) to preventprecipitation and runoff from entering the un-capped portions of the Phase I area. The InterimCap design, consisting of a geosynthetic clay liner, 12” drainage sand layer, 6” plantable soil layer,and permanent vegetation was approved by the EPA in October 2001. The approval process alsoincluded evaluation of an existing “shiplap barrier” (a leachate diversion system) placed along theinterface of the Phase I and Phase II areas during filling of the Phase II area by the RIRRC.

In October 2001, the RIRRC entered into a contract with Fleet Construction (Fleet) to install theInterim Cap (approximately 14 acres). With the exception of punchlist items, the Interim Capwas completed in January 2002. Punchlist items were added to the outstanding list of items forAreas 3 & 4 and RIRRC agreed to complete these items when weather permitted in Spring 2002. Photographs of the cap construction are provided in Attachment 1.

In September 2003, RIRCC entered into a contract with J.H. Lynch & Sons to completeplacement of the RCRA cap in Areas 5, 6 and 7 (approximately 54 acres) of the Phase I area. Construction activities are expected to commence in September 2003 and are required to becomplete in November 2005.

Hydraulic Containment and Groundwater Treatment System for Hot Spot Area

As specified in the OU1 ROD and SOW, this component of the remedy involves extractingcontaminated groundwater from the Hot Spot area in order to prevent contaminated groundwater

1The initial Remedial Design Work Plan submitted by GZA in [August 2001] was revisedto incorporate EPA comments and resubmitted as a Revised Remedial Design Work Plan.

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from migrating beyond the Area of Containment and treating it before it is discharged to eitheron-site surface water or the Cranston, Rhode Island wastewater treatment plant.

The compliance boundary for groundwater is defined in the SOW as the toe of the 154-acre PhaseI, II, and III areas. The Area of Containment (AOC) is defined in the SOW as “an areadowngradient of the Hot Spot where chlorobenzene is present in the groundwater atconcentrations greater than or equal to 1 ppm, except that the eastern boundary of the AOC isdefined as the toe of the slope of the landfill.”

The deadline for completion of the hydraulic containment and groundwater treatment system isJuly 16, 2006, which is 10 years following EPA approval of the prime contractor for the capdesign (July 16, 1996). The deadline for the 30% design was July 16, 2002. The 30 % design hasbeen started but has not been completed.

A Revised Remedial Design Work Plan for the Hot Spot Groundwater Containment andTreatment System was prepared by GZA GeoEnvironmental, Inc. in June 2002 (GZA, 2002b).1 This report outlines activities to be performed to ensure that the groundwater containment systemis designed in a manner that effectively controls the groundwater and is consistent with therequirements of the ROD. Activities to be performed include the installation of six additionalmonitoring stations along the flow path that passes through the Hot Spot to the Phase I toe ofslope and a single round of comprehensive groundwater screening and analytical testing. The sixboreholes were installed and borehole geophysical testing was conducted during July and August2003. Packer testing and groundwater sampling are planned for September 2003 (GZA, 2003c).As of September 5, 2003, the activities were considered by GZA to be approximately 47%complete.

A minimum of two extraction wells are also planned to better assess the properties of the bedrockand to obtain samples for bench scale treatability tests. Bench scale tests will be performed toverify the suitability of an ultraviolet oxidation system for treatment of Hot Spot groundwater. Several discharge options will be evaluated including evaporation, subsurface injection, surfacewater discharge, and discharge to the Cranston POTW. Although the ROD listed only twodischarge options (onsite surface water or the Cranston POTW) the ROD did include performance standards that must be met for the additional foregoing options for discharge as well.

Institutional Controls and Installation of Chain Link Fence To Prevent Access

The institutional controls and access controls for the Site are currently in place as described below.

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RIRRC filed a Declaration of Covenants and Environmental Protection/Conservation Easementon property it owns at the 612-acre parcel. The Covenant prohibits the use of groundwaterexcept for remediation purposes, prohibits the installation of groundwater wells or the use ofexisting groundwater wells and prohibits the alteration of the groundwater flow in any way(USEPA, 2002).

The Town of Johnston adopted a Town ordinance on February 10, 2003 that, among other things,prohibits the use of groundwater wells and prohibits the Building Inspector from issuing permitsfor the construction of groundwater wells in any location where access to Town public water isavailable; where the well or proposed well is located in certain described areas including wheregroundwater has been classified by the State as GAA non-attainment, GA non-attainment, GB,GB non-attainment or GC; and where it is located in the OU2 areas recommended for institutionalcontrols.

The 612-acre property owned by RIRRC is partially fenced and vehicular entry is limited tosecured roadways. Security guards patrol the property 24 hours/day. Long-Term Groundwater, Surface Water, and Air Monitoring

Long-term monitoring of groundwater and surface water is currently being conducted inaccordance with the Revised Environmental Monitoring Plan (EMP) which was prepared by GZAGeoEnvironmental in May 1997 (GZA, 1997). This revised plan replaces the EnvironmentalMonitoring Plan prepared by GZA GeoEnvironmental in December 1994. The plan wasdeveloped to address OU1 current and post-closure groundwater and surface water monitoringrequirements in addition to several other regulatory requirements. The revised EMP wasimplemented beginning in August 1997.

Groundwater and surface water sampling are conducted on a quarterly basis. An expandedannual monitoring round is conducted during August of each year.

Quarterly monitoring will continue to be performed during implementation of the remedial actionsand for a period of five years subsequent to the completion of remedial actions. At that time, areview of 10 years worth of data will be conducted, and if no statistically significant increase incontaminant concentrations is observed since implementation of the remedial actions, themonitoring frequency will be reduced to semi-annually.

Long-term monitoring of air is also currently being conducted in accordance with the RevisedEMP (GZA, 1997). Quarterly sampling of ambient air for VOCs is conducted at a minimum offour locations: one upwind of the Phase I, II, and III areas and three downwind of these areas.

Refer to Section 5.3 for a review of groundwater, surface water, and air monitoring data and trends.

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Evaluation of the Existing Landfill Gas Collection and Combustion System

The Performance Standards For Emissions To Air, specified in the 1996 Consent Decree requiresthe RIRRC to demonstrate that the landfill gas collection and combustion system, which collectsand treats gas from the Phase I area of the landfill, does not result in an unacceptable humanhealth risk and complies with all federal and state ARARs.

Documentation describing how the RIRRC will demonstrate compliance with the PerformanceStandards For Emissions To Air has not yet been submitted to the EPA for review and approval. However, a significant amount of evaluation was performed by RIRRC as part of a recent CleanAir Act enforcement case against the RIRRC. Also, a recent review of air data and a recentATSDR Health Consultation ( see Section 5.3.3 of this Report) have not shown any unacceptablehuman health risks associated with air emissions from the Central Landfill.

For a long-term protectiveness finding, however, RIRRC must complete this evaluation anddemonstrate compliance with the performance standards.

4.3 SYSTEM OPERATIONS/O&M

When construction is complete, long-term monitoring, and operations and maintenance (O&M)activities will be conducted by the RIRRC in accordance with the Environmental Monitoring Planand Operations and Maintenance Plan, prepared pursuant to the 1996 Consent Decree and theROD.

SECTION 5.0FIVE-YEAR REVIEW PROCESS

This section describes the activities performed during the five-year review process and provides asummary of findings.

5.1 COMMUNITY NOTIFICATION AND INVOLVEMENT

A summary of the most significant community involvement over the past five years is providedbelow:

In the fall of 1999, the Central Landfill Action Committee (CLAC) was formed. Established as acitizen advisory group, the purpose of the CLAC was to bring together appropriate federal, state,and local authorities with local residents to work together to address and correct non-Superfundrelated on-going solid waste practices impacting the community. The committee was alsoestablished as a forum for open and ongoing dialogue between agency representatives andresidents on other environmental concerns in the community.

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The CLAC met bi-monthly. During the meetings the committee discussed possible solutions toover 75 environmental issues associated with solid waste disposal activity at the Central Landfilland nearby facilities. Although the purpose of the CLAC was not Superfund related, the status ofthe Superfund remedial actions were occasionally discussed.

In February and March 2001, EPA Site managers held separate meetings with the ProvidenceWater Board, officials from the towns of Scituate, Cranston, and Johnston, and US SenatorLincoln Chaffee to discuss groundwater behavior and landfill operations at the Site, and to reviewthe status of OU2 investigations.

In late April and May 2001, EPA held public meetings in each of the communities surrounding thelandfill. EPA presented information on the groundwater investigations to residents at these publicmeetings.

On August 30, 2001, the Agency held a public hearing to discuss the OU2 Proposed Plan and toaccept oral comments. A transcript of this meeting and the comments and the Agency’s responseto comments are included in the Responsiveness Summary, which is part of the OU2 Record ofDecision.

Soon after the review and approval of this five-year review report, a notice will be placed in alocal paper announcing that the five-year review report is complete and that it is available to thepublic at the following Site repositories.

Marion J. Mohr Memorial Public Library1 Memorial DriveJohnston, RI 02919

EPA – Region 1 (New England) Records Center One Congress Street Boston, Massachusetts 02114-2023

5.2 DOCUMENT REVIEW

This five-year review consisted of a review of relevant documents for both Operable Unitsincluding the RODs, Consent Decree for OU1, and O&M and monitoring plans and reports. SeeAttachment 2 for a list of documents that were reviewed.

5.3 DATA REVIEW

5.3.1 Groundwater Monitoring

Groundwater monitoring has been conducted on an approximately quarterly basis since 1980(GZA, 2003b). The current monitoring program, described in a document titled Revised

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Environmental Monitoring Program, Central Landfill, Johnston, RI (GZA, 1997), was designedto satisfy the requirements of the OU1 Consent Decree Scope of Work (October 1, 1996). Theobjectives of the groundwater monitoring are to 1) measure the effect of capping the landfill onthe concentrations of contaminants migrating beyond the compliance boundary and 2) ensure thatthose concentrations are not increasing or adversely affecting human health or the environment. Since the landfill cap is still under construction, and the Hot Spot groundwater containmentsystem is still being designed, the monitoring has thus far been used primarily to judge whetherwater quality at the site is deteriorating.

Under the OU1 Groundwater Monitoring Plan, 28 locations are sampled each quarter. During thesummer (typically August) sampling round, an additional 9 to 12 locations are sampled. Most ofthe monitored wells are open to the shallow bedrock, since that is the zone in which the highestconcentrations of contaminants have typically been detected at multi-well clusters. The othermonitored wells are open to the overburden and to deeper bedrock zones. Due to occasionallandfill operational mishaps that damage certain wells, not all wells are sampled during eachmonitoring event.

Quarterly and annual monitoring reports are prepared. As required by the plan, the reportsinclude comparisons between contaminant concentrations and Maximum Contaminant Levels(MCLs) as well as evaluations of trends in contaminant concentrations. For the preparation ofthis five-year review, two reports from the monitoring program were primarily reviewed: themost recent annual report (GZA, 2003a), which includes results from the four sampling roundsbetween August 2001 and May 2002, and the most recent quarterly report (GZA, 2003b), whichincludes results from the November 2002 sampling round. The reports indicate that in 2001 and2002, a number of organic and inorganic contaminants were detected at concentrations exceedingMCLs in wells beyond the compliance boundary (i.e., toe of the landfill) but within the RIRRC-owned property except for one exceedence in a residential well beyond the property boundary. Inalmost all cases, the apparent violation of the MCL was supported by the statistical analysis, inwhich the upper confidence limit at a 95 percent confidence level was calculated and alsocompared to the MCL. Organic contaminants for which MCLs were exceeded included benzene,chlorobenzene, 1,2-dichlorobenzene, and 1,4-dichlorobenzene. These contaminants weredetected primarily south of the Phase I area and southeast of the Hot Spot. The concentrations ofnumerous inorganic contaminants also exceeded MCLs (e.g., beryllium, cadmium, lead).

The analyses of trends in the concentrations of the detected contaminants in the two reportsrevealed that both increasing and decreasing, statistically-significant trends existed at various wellsthroughout the Site as of 2002. As stated above, organic contaminants are less widespread at theSite, occurring mostly to the south and east of the Phase I area. In the annual report, whichincluded data through May 2002, no increasing trends were indicated for any of the four primaryorganic contaminants (benzene, chlorobenzene, 1,2-dichlorobenzene, and 1,4-dichlorobenzene); atthat time, decreasing trends were identified for benzene at one well (MW90-32) and forchlorobenzene at two wells (MW90-32 and MW92-43). However, in the most recent quarterlyreport, which includes data through November 2002, increasing trends emerged for severalorganic contaminants, including benzene at MW02-B and MW02-B1; chlorobenzene at

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MW90-34B and WE85-6B (below MCL); and 1,2-dichlorobenzene and 1,4-dichlorobenzene atMW90-34B. These upward trends in concentrations of organic contaminants may or may notpersist as remedial activities and data collection continue.

Despite the recent identification of increasing trends in the concentrations of several organiccontaminants in wells south and east of the Phase I area, no evidence was found of large-scaleprogressive deterioration of water quality in the recent monitoring reports. However, there wasalso no indication that the partial capping of the Site has to date resulted in any significantimprovements in downgradient water quality. Continued monitoring will demonstrate whether the increasing trends in contaminant concentrations persist, or if water quality stabilizes orimproves as the remedial action is completed.

5.3.2 Surface Water Monitoring

The current surface water monitoring program, described in a document titled RevisedEnvironmental Monitoring Program, Central Landfill, Johnston, RI (GZA, 1997), was designedto satisfy the requirements of the OU1 Consent Decree Scope of Work (October 1, 1996). Theobjectives of the surface water monitoring are to 1) measure the effect of capping the landfill onthe concentrations of contaminants migrating from the Phase I landfill and Hot Spot area tosurface water locations; and 2) ensure that those concentrations are not increasing or adverselyaffecting human health or the environment. Since the landfill cap is still under construction, andthe Hot Spot groundwater containment system is still being designed, the monitoring has thus farbeen used primarily to judge whether surface water quality is deteriorating.

Surface water samples are collected at five locations each quarter. Two are upstream locations,on Quarry Stream at the outlet from Pond 4 and on Cedar Swamp Brook at the outlet from awater body known as the “swimming hole”. The other three consist of two downstream locationson Cedar Swamp Brook, at the inlet and outlet from Pond 2, and one downgradient location atthe outlet from Pond 3. Samples for the analyses of metals, except for iron, are filtered with a0.45 micron filter. Since some locations are seasonally dry, not all locations are sampled duringeach monitoring event.

Quarterly and annual monitoring reports that include the results from the surface water samplingare prepared. As required by the plan, the reports include comparisons between contaminantconcentrations and Federal Ambient Water Quality Criteria (FAWQC) as well as evaluations oftrends in contaminant concentrations. For the preparation of this five-year review, two reportsfrom the monitoring program were primarily reviewed: the most recent annual report (GZA,2003a), which includes results from the four sampling rounds between August 2001 and May2002, and the most recent quarterly report (GZA, 2003b), which includes results from theNovember 2002 sampling round. The reports indicate that in 2001 and 2002, a number ofinorganic and organic contaminants were detected, but only the inorganics were found atconcentrations exceeding FAWQC. The inorganic contaminants, which were found in bothupstream and downstream samples, included beryllium, copper, total iron, lead, silver, thallium,and zinc. In many cases, the apparent violation of the FAWQC was supported by the statistical

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analysis, in which the upper confidence limit at a 95 percent confidence level was calculated andalso compared to the FAWQC. However, in many cases the concentration was less than thestatistically-determined background Prediction Limits.

The analyses of trends in the concentrations of the detected contaminants in the two reportsrevealed that no metals or VOCs showed increasing statistically-significant trends at the surfacewater sampling locations. No evidence was found of large-scale progressive deterioration ofsurface water quality in the recent monitoring reports. Continued monitoring will show if surfacewater quality stabilizes or improves as the remedial action is completed.

5.3.3 Air Monitoring

Long-term monitoring of air is also currently being conducted in accordance with Revised EMP(GZA, 1997). Quarterly sampling of ambient air for VOCs is conducted at a minimum of fourlocations: one upwind of the Phase I, II, and III areas and three downwind of these areas.

Quarterly ambient air monitoring results for VOCs were reviewed (GZA 2000-2003). To date,no VOCs have been detected at the landfill above levels that are considered protective of on-siteworkers.

In response to odor complaints and health concerns from area residents, the Agency for ToxicSubstances and Disease Registry (ATSDR) and the Rhode Island Department of EnvironmentalManagement (RIDEM) conducted an exposure investigation in Johnston, RI, to determinewhether air emissions from the Central Landfill present a public health hazard to nearby residents. This investigation was conducted from July 2000 through May 2001. The results of theinvestigation (ATSDR 2002) are summarized in the following paragraphs.

In 1999, RIDEM asked ATSDR to review environmental sampling data collected near the CentralLandfill to determine whether the levels of VOCs presented a health hazard to nearby residents. ATSDR reviewed air sampling data collected for VOCs and hydrogen sulfide downwind of theCentral Landfill (ATSDR 2000). ATSDR completed a health consultation in June 2000, whichconcluded that the levels of VOCs measured were below levels of health concern. However,ATSDR identified information gaps that prevented a more thorough evaluation. The identifieddata gaps included the levels of hydrogen sulfide and gaseous combustion products (i.e., nitrogendioxide, sulfur dioxide, and formaldehyde) in residential areas during odor events and periods ofstable atmospheric conditions. ATSDR and the RIDEM set out to fill the identified data gaps.

From July 2000 through October 2000, the ATSDR and the RIDEM monitored hydrogen sulfide,VOCs, and sulfur compounds in residential areas north, northeast, and east of the landfill. FromJuly 2000 through August 2000, the RIDEM and ATSDR measured levels of sulfur dioxide andnitrogen dioxide outside two residences and a municipal building. In March 2001, the RIDEMinstalled an air monitoring station at a location northeast of the landfill (Wood Lake Park) tomeasure gaseous products of landfill gas combustion (nitrogen dioxide, sulfur dioxide and

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aldehyde).

The ATSDR concluded that the levels of VOC and hydrogen sulfide measured do not present ahealth hazard to nearby residents. No sulfur compounds were detected above their limits ofdetection ( 5 parts per billion or less). However, canister holding times exceeded the ATSDRrecommended time limit of 48 hours for reduced sulfur compounds. Therefore, these canistercollected sulfur compounds were not considered in their health consultation.

The ATSDR concluded that they anticipate no adverse health effects from the measured levels of nitrogen dioxide. Although sulfur dioxide levels exceeded the ATSDR Minimal Risk Level(MRL), they were below the EPA health based quality standard of 140 part per billion. ATSDRconcluded that they anticipate no adverse health effects from the measured levels of nitrogendioxide. ATSDR also concluded that the measured levels of aldehyde were below ATSDR andEPA health based comparison values, and therefore they do not present a health hazard to nearbyresidents.

5.4 SITE INSPECTION

Construction has not been completed. The Site is routinely inspected as part of the EPA’songoing construction oversight.

5.5 INTERVIEWS

Site interviews were not performed as part of this five-year review.

SECTION 6.0TECHNICAL ASSESSMENT

This section discusses the technical assessment of the remedy and provides answers to the threequestions posed in the EPA Guidance (USEPA, 2001).

6.1 Question A: Is the remedy functioning as intended by the decision documents?

Construction of the landfill cap and Hot Spot pump and treat system have not yet been completed. The review of documents, ARARs, risk assumptions, and oversight of construction activitiesindicates that the remedy is being constructed in accordance with the ROD, and is expected to beprotective when it is completed.

Long-term sampling of groundwater and surface water is being conducted on a quarterly basis. Based on the monitoring data reviewed, increased trends were identified for several organiccontaminants in wells south and east of the Phase I area. However, no evidence was found oflarge-scale progressive deterioration of groundwater or surface water quality. Future

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groundwater and surface water monitoring data and trends should be reviewed as part of the nextFive-Year Review in order to determine whether increasing trends in contaminant concentrationspersist or if water quality stabilizes or improves as the remedial action is completed.

The institutional controls and access controls are currently in place. The institutional controlsinclude a Town of Johnston ordinance that prohibits the use of groundwater wells and prohibitsthe Building Inspector from issuing permits for the construction of groundwater wells in anylocation where access to Town public water is available and where the well or proposed well islocated in certain described areas including where groundwater has been classified by the State asGAA non-attainment, GA non-attainment, GB, GB non-attainment or GC and where it is locatedin the OU2 areas recommended for institutional controls. Also, RIRRC filed a Declaration ofCovenants and Environmental Protection/Conservation Easement on property it owns at the 612-acre parcel, which prohibits the use of groundwater except for remediation purposes, prohibits theinstallation of groundwater wells or the use of existing groundwater wells, prohibits the alterationof the groundwater flow in any way, and prohibits any activities that would interfere with theintegrity of the cap. The 612-acre property owned by RIRRC is partially fenced, vehicular entryis limited to secured roadways, and security guards patrol the property 24 hours/day.

6.2 Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedialaction objectives (RAOs) used at the time of remedy selection still valid?

Physical conditions at the Site have changed in that Phase II and III landfilling operationsconcluded in July 2003. As explained in Section 4.2 above, some areas of Phase II overlapportions of the Phase I area which prevented completion of the cap and required installation of animpermeable barrier between the two phases. This change did not affect the protectiveness of theremedy since institutional controls are in place to prevent use of groundwater as drinking water. The RIRRC has also expanded into a 44-acre expansion area known as Phase 4, which is locatedsouth of the Phase II and III areas (see Figure 2, provided in Attachment 1 of this report).

6.2.1 Review of Risk Assessments and Toxicity Factors Serving as the Basis for the Remedy

The OU2 human health risk assessment was completed in 2001. This risk assessment wasperformed using current risk assessment methodology to evaluate current and potential future off-site exposure pathways that exist or are anticipated to exist at the site. A small number of toxicityvalues have changed since 2001. Of the compounds whose toxicity values have changed since2001, only benzene is of potential importance for this site. The change is minor and would notaffect the conclusions of the risk assessment or the protectiveness of the remedy.

The OU1 human health risk assessment (CDM FPC, 1993) was conducted using methodologywhich would partially comply with current EPA risk assessment guidance. The primarydiscrepancies between current guidance and previous guidance exist in the areas of toxicityvalues, which have been significantly refined since 1993, and risk assessment methodology used

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to select COPCs. In addition, the risk assessment characterized risks based on maximum detectedconcentrations. Current guidance prescribes the use of the 95% upper confidence limit for riskcharacterization. Use of the maximum detected concentration may result in an overestimate ofrisk. The following provides an evaluation of these discrepancies and their impact on theprotectiveness of the remedy.

6.2.2 Changes in Exposure Pathways and Risk Assessment Methods

The OU1 human health risk assessment did not evaluate adult or child exposures to soils withinthe landfill area under the assumption that a complete exposure pathway did not exist between thecontaminants and the receptor (i.e., contaminants exist either below a cap or in only small areas ofpotential accessibility). This assumption is still valid and will continue to be valid as long as theintegrity of the landfill cap is maintained and a physical barrier (i.e., fence) is provided to preventdirect contact with exposed soils. In addition, adherence to a health and safety plan minimizesimpacts to workers who contact soil contaminants.

The OU1 risk assessment also did not evaluate exposures to contaminants in air since measuredcontaminant levels on-site or in downwind areas were consistent with or only slightly above thosemeasured at upwind locations. Therefore, no air COPCs were selected. Using current riskassessment methods, the measured air concentrations would have been quantitatively evaluatedeven though consistent with “background” levels because background is no longer used to selectcompounds as COPCs. Current methods dictate the screening of maximum detectedconcentrations against health-based criteria (e.g., Region 9 Preliminary Remediation Goals). Thisscreening has been performed as part of this five-year review and indicates that most detectedcompounds are below risk-based criteria. Those that exceed the screening criteria would beassociated with cancer and noncancer risks below regulatory levels of concern.

Adult and child recreational exposures within Upper Simmons Reservoir and Almy Reservoirwere quantitatively evaluated as part of the OU1 risk assessment. However, because measuredsurface water data was not available at the time, these surface water bodies along with thecurrent/future exposure pathways were re-evaluated as part of the OU2 risk assessment whichconcluded that no unacceptable risks exist. Future on-site groundwater use was also evaluated in the risk assessment. On-site groundwater isnot currently used as a source of potable water, but may be used as a future resource in GA-designated areas. This assumption continues to be valid. The OU2 risk assessment evaluatedpotential off-site impacts to groundwater, and institutional controls are in place preventing the useof groundwater in GA-designated areas. Unacceptable risk was estimated for this future exposurescenario using methods and exposure assumptions largely consistent with current guidance. Aslong as institutional controls remain in place, the remedy is protective with respect togroundwater.

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6.2.3 Changes in Standards and To Be Considereds

Although changes have occurred in the Applicable or Relevant and Appropriate (ARARs), and ToBe Considereds (TBCs) since the ROD was signed, these changes do not affect the remedy’sprotectiveness. These changes are summarized below:

1. The adoption of a new lower Maximum Concentration Level (MCL) standard forarsenic in groundwater (changing the standard from 50 ppb to 10 ppb). The MCL for thearsenic standard was changed as a result of an amendment to the Safe Drinking Water Act in1996 which required EPA to review drinking water standards for arsenic and propose a new MCLby a date certain. The proposed MCL was 10 ppb. After some delay and further review, EPAaffirmed the 10 ppb standard for arsenic in drinking water and the arsenic drinking water rulebecame effective on February 22, 2002. Although this new rule applies to certain drinkingwater systems, the Superfund program also adopted this new standard and is treating it as itwould any other MCL-based contaminant concentration level in it decision making process forsite contamination.. In the OU1 ROD, the Safe Drinking Water Act MCLs and non-zero MCLGsare cited as action specific, relevant and appropriate regulations to measure the performance ofthe cap rather than groundwater cleanup values. This means that at the completion of the remedy,MCLs must be met at the edge of the waste area. The change to the arsenic standard affects onlythe performance time line, not the protectiveness of the remedy in that concentrations levels needto fall to the new standard of 10 ppm at the compliance boundary. In the interim, becauseinstitutional controls prohibit the use of groundwater, the remedy remains protective. For theOU2 ROD, the new MCL was used in the risk assessment; therefore the no action conclusionremains sound.

2. Toxicity values for reference doses, reference concentrations, cancer slope factorsand inhalation unit risks have changed significantly since 1993 when the OU1 risk assessment wasperformed. These toxicity values were noted as TBCs in the RODs. Reference doses andreference concentrations were not available in 1993 for benzene, trichloroethene and vinylchloride, resulting in an underestimation of noncancer risk for the future groundwater usepathway. For cancer risk, differences were noted in the cancer slope factors and unit risk valuesused in the human health risk assessment for trichloroethene, arsenic and vinyl chloride. Thecancer toxicity values used in the risk assessment for arsenic and vinyl chloride were slightlymore conservative than current values, while that used for trichloroethene was slightly lessconservative. In addition, beryllium and nickel were evaluated as potential carcinogens; however,current information does not indicate that these inorganics have cancer-causing potential. Together, these differences result in a slight overestimate of groundwater cancer risk in 1993 thanwould be calculated today. Other differences between historical and current toxicity valuestended to be minimal. Since only a small number of toxicity values have changed since the 2001OU2 risk assessment was finalized, the impact of toxicity values on the OU2 risk assessment isdeemed to be minimal.

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6.2.4 Summary and Conclusions

Differences were noted between the OU1 human health risk assessment and current riskassessment practices. Because of the variable nature of the differences, some tending tounderestimate and others overestimate risk, the estimated risks are unlikely to be substantiallydifferent from risks estimated using current guidance.

Because OU1 soils are largely capped and groundwater exposures are prevented by institutionalcontrols, the remedy is protective of human health as long as the cap and institutional controls aremaintained. Since measured air levels are not of a concern for human health, the remedy is alsoprotective for on-site and downwind air impacts to off-site receptors. Since the OU2 riskassessment was performed using current risk assessment guidance and evaluated current andpotential future off-site exposure pathways that exist or are anticipated to exist at the site, theremedy continues to provide protectiveness against human health risks.

6.3 Question C: Has any other information come to light that could call into question theprotectiveness of the remedy?

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

SECTION 7.0ISSUES

Based on the activities conducted during this Five-Year Review, the issues identified in Table 2have been noted.

Table 2: Issues

Issues Affects CurrentProtectiveness

(Y/N)

Affects FutureProtectiveness

(Y/N)

The deadline for submittal of the 30% design for theHot Spot Groundwater Containment and TreatmentSystem on July 16, 2002 was not met.

N N

The Area 3, Area 4, Interim Cap punch list items havenot been completed.

N Y

Evaluation of the landfill gas collection and combustionsystem not complete

N N

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SECTION 8.0RECOMMENDATIONS AND FOLLOW-UP ACTIONS

In response to the issues noted above, it is recommended that the actions listed in Table 3 betaken:

Table 3: Recommendations and Follow-up ActionsIssue Recommendations

and Follow-upActions

PartyResponsible

OversightAgency

MilestoneDate

AffectsProtectiveness

Current Future

30% Design forthe hydrauliccontainment andtreatment system isnot complete.

RIRRC to complete30% Designsubmittal ASAP

RIRRC USEPA 05/01/04 N N

Area 3, Area 4,Interim Cap punchlist items

RIRRC to completepunch list ASAP

RIRRC USEPA 11/05 N Y

Complete theevaluation of thelandfill gascollection andcombustionsystem..

RIRRC to submit aplan for completingthe evaluationASAP.

RIRRC USEPA 05/01/04 N N

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SECTION 9.0PROTECTIVENESS STATEMENTS

The remedy for OU1 is expected to be protective of human health and the environment uponcompletion, and in the interim, exposure pathways that could result in unacceptable risks arebeing controlled. Institutional controls and access restrictions are in place and are successfullypreventing exposures.

SECTION 10.0NEXT REVIEW

The next Five-Year Review for the Central Landfill Superfund Site is September 2008, five yearsfrom the date of this review.

ATTACHMENT 1SITE MAPS

PHOTOGRAPHS

Area 3 Under Construction, July 1999

Area 3 Downchute Under Construction, July 1999

Area 4 South Landfill Cap Construction, November 2000

Landfill Cap Layers, November 2000. From right to left: 60 mil LLDPEgeomembrane, composite drainage net, vegetative support layer, topsoil,and seed and erosion control.

Interim Cap Construction, October 2001

Area 4 Completed, May 2002

ATTACHMENT 2LIST OF DOCUMENTS REVIEWED

CDM Federal Programs Corporation (CDM FPC). 1993. Baseline Risk Assessment Task 8Deliverable Central Landfill, RI/FS Oversight, Johnston, Rhode Island. November23, 1993.

GZA GeoEnvironmental, Inc. (GZA). 1997. Revised Environmental Monitoring Plan, CentralLandfill, Johnston, Rhode Island. Prepared for Rhode Island Resource RecoveryCorporation. May 1997.

GZA GeoEnvironmental, Inc. (GZA). 2002a. Monitored Natural Attenuation Work Plan, CentralLandfill, Johnston, Rhode Island. Prepared for Rhode Island Resource RecoveryCorporation. January 2002.

GZA GeoEnvironmental, Inc. (GZA). 2002b. Revised Remedial Design Work Plan - Hot SpotGroundwater Containment and Treatment System, Central Landfill, Johnston, RhodeIsland. Prepared for Rhode Island Resource Recovery Corporation. June 2002.

GZA GeoEnvironmental, Inc. (GZA). 2003a. Environmental Monitoring Program AnnualReport, EPA Mandated, May 2002, Central Landfill, Johnston, Rhode Island.Prepared for Rhode Island Resource Recovery Corporation. March 17, 2003.

GZA GeoEnvironmental, Inc. (GZA). 2003b. Environmental Monitoring Program QuarterlyReport, November 2002, Central Landfill, Johnston, Rhode Island. Prepared forRhode Island Resource Recovery Corporation. August 2003.

GZA GeoEnvironmental, Inc. (GZA). 2000-2003a. Ambient Air Monitoring Results. July 2000,October 2000, January 2001, April 2001, October 2001, January 2002, May 2002,July 2002, October 2002, January 2003, April 2003.

Agency for Toxic Substances and Disease Registry (ATSDR). 2000. Health Consultation -Central Landfill. April 2000.

Agency for Toxic Substances and Disease Registry (ATSDR), Division of Health Assessment andConsultation. 2002. Exposure Investigation, Central Landfill, Johnston, ProvidenceCounty, RI. November 20, 2002.

United States Environmental Protection Agency (USEPA). 1994. Record of Decision, CentralLandfill Superfund Site, Johnston, Rhode Island, Operable Unit 1. June 1994.

United States Environmental Protection Agency (USEPA). 2001. Comprehensive Five-YearReview Guidance. June 2001.

United States Environmental Protection Agency (USEPA). 2002. Record of Decision, CentralLandfill, Johnston, Rhode Island, Operable Unit 2. September 2002.