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Waste Site Cleanup & Reuse in New England
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  DOVER MUNICIPAL LANDFILL


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 Dover,  New Hampshire
 Strafford County
 Street Address: TOLEND RD
 Zip Code: 03820
 Congressional
 District(s):

01
 EPA ID #: NHD980520191
 Site ID #: 0101125
 Site Aliases:

 Site Responsibility: Federal, Municipal, State, Potentially Responsible Parties

 NPL LISTING HISTORY
 Proposed Date 12/30/1982
 Final Date 09/08/1983

Site Description
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The Dover Municipal Landfill is a 50-acre inactive landfill located on Tolend Road, in the Mallego Plains section, in the western corner of Dover, NH. Owned and operated by the City since 1960, the landfill initially accepted domestic refuse from Dover, but by the mid-1960s, took in industrial wastes and loose trash from both Dover and Madbury. Buried materials include leather-tanning wastes, organic solvents, municipal trash, and sludge from the Dover wastewater plant. It is believed that drums were no longer accepted after 1975. In 1977, the State installed monitoring wells around the area and found that organic solvents were entering the ground water, posing a potential threat to nearby residential wells and public water supplies for Dover and Portsmouth. The State and the Dover City Council ordered the landfill closed in 1980. The site is in a rural, residential area. There are 50 homes within 1 mile of the landfill, and the surrounding area is used for hunting and berry picking. Two water supplies are potentially at risk: the Calderwood municipal well, located a 1/2 mile north of the site, which supplies 20 percent of Dover's water; and the Bellamy Reservoir, located 1/3 mile south of the site, which supplies the cities of Portsmouth, Newington, New Castle, Greenland, and portions of Rye, Madbury, and Durham. Both of these water supplies remain unaffected by the landfill. Leachate from the landfill is entering the Cocheco River via ground water discharging to the river, 400 feet away from the site at the closest point.

Threats and Contaminants
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The ground water is contaminated with Volatile Organic Compounds (VOCs) and arsenic. Two residential wells were historically contaminated with organics from the site; however, a water line was installed in 1981 such that water is no longer being consumed from the area surrounding the site. Sediments in drainage trenches around the site and the Cocheco River are contaminated with arsenic. The Cocheco River receives leachate from a drainage ditch that originates at the landfill; VOCs have also been detected in the surface water. People using the site for recreational purposes could come into direct contact with, accidentally ingest, or inhale contaminated materials. Drinking contaminated ground water and swimming or wading in the drainage ditch or the Cocheco River also could expose people to harmful chemicals. Nearby wetlands are potentially threatened by site contamination. Contaminated ground water is flowing towards the Bellamy Reservoir and Cocheco River. The only unacceptable risk to human health or the environment from the site is drinking contaminated ground water.

Cleanup Approach
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The site is being addressed in two stages: initial actions and a long-term remedial phase aimed at cleanup of the entire site.

Response Action Status
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Initial Action A water line was installed in 1981, after contamination was found in a few private wells, to connect those residents on Tolend Road to a separate water source.

Entire Site In 1984, the State began a study of the site to assess the nature and extent of contamination. The parties potentially responsible for the site contamination (the "Group") assumed responsibility for the study in 1988. The EPA selected final cleanup remedies for the site, as documented in a 1991 Record of Decision (ROD). The cleanup remedies included: recontouring and capping the landfill, treating leachate, extracting and treating the southern plume of contaminated groundwater, and allowing the eastern plume of groundwater to clean itself through natural attenuation. The design of these cleanup remedies began in 1992, however, they were delayed while the Group, the state, and EPA evaluated alternative technologies. An in-situ bioremediation alternative was pilot tested from 1997 until 2002. In 2004 the EPA issued an Amended ROD.

Bioremediation Pilot In 1997, the parties began examining the use of bioremediation to address ground water contamination at the site. Due to the complexity of ground water at the site, EPA agreed to extend the bioremediation pilot beyond its original two years to December 2001. The ultimate conclusion of that study, in 2002, was that the hydrogeology was not conducive to distributing materials needed to support bioremediation and that the EPA lacked confidence in the bioremediation remedy, as pilot-tested, to address contaminants at the site.

2004 Amended Record of Decision Examination of the results of the Bioremediation Pilot generated an alternative remedy that required further evaluation for potential use at the site. As such, the Group produced a Revised Focused Feasibility Study (RFFS) to examine this alternative remedy, and an additional alternative proposed by EPA, against the 1991 ROD. EPA evaluated that RFFS which contained two alternative approaches to cleanup the entire site and the 1991 ROD remedy. EPA issued an Addendum that further clarified the analysis provided in the RFFS. Based on its review of the data and the remedies evaluated, the EPA moved forward with a Proposed Plan outlining a remedy change for the site. EPA signed an Amended Record of Decision (AROD) on September 30, 2004.

2004 Selected Remedy In the 2004 AROD, EPA chose to replace the landfill cap originally selected in the 1991 ROD with a strategy of leaving the landfill uncapped and allowing infiltrating rain water to move contaminants to and through an air-sparging trench that would remove or destroy the contaminants. Ground water that exits on the other side of the air-sparging trench would meet drinking water standards for the chemicals of concern at the site.
Additionally, portions of the 1991 ROD were retained and will be implemented, as follows:

1) Arsenic-contaminated sediments will be removed as appropriate.
2) Ground water in the Eastern Plume, migrating towards the Cocheco River, will be addressed through monitored natural attenuation.
3) Ground water in the Southern Plume, migrating towards the Bellamy Reservoir, will be addressed by pumping the contaminated ground water out, treating it to drinking water levels, and discharging that treated water.

Monitoring of ground water, surface water, sediments, and indoor air will ensure that the remedy is protective of human health and the environment. Institutional controls will ensure that ground water is not used for drinking water purposes.


On-going Site Monitoring The present monitoring program seeks to track known contaminants such as volatile organic compounds (VOCs) and arsenic in various media which historical sampling has shown to be contaminated. The monitoring program also seeks to periodically check other contaminants that either have not been contaminants at the site or have diminished in concentration, such as mercury and semi-volatile organic compounds, respectively. Media that have been shown not to be contaminated by site contaminants, such as outdoor air, are also periodically monitored.
Ground water, surface water, and sediments are sampled twice a year, once in the spring and again in December. The December 2011 sampling was delayed for more thorough sampling prior to start-up of the groundwater extraction system in January 2012.


Cocheco River Pre-Design Investigation The Cocheco River contains sediments that have historically shown small amounts of arsenic associated with the landfill. In Autumn 2005 and 2009, the Group characterized risk to human health and the environment from sediments. The analysis included toxicity tests that measure the survival of freshwater insects.
The reports to EPA found no excess risk to human health or impairment from the sediments. As part of the 2009 Consent Decree, sediment sampling will continue to assess risk to human health and the environment.


Indoor Air Pre-Design Investigation EPA issued a letter on September 23, 2009 finding that there was no risk from contaminant vapors originating from groundwater based on three years of groundwater monitoring.

Northwest Landfill Remedy Historical surface water sampling in a small ditch on the northwest corner of the landfill had detected a potential source of volatile organic compounds. Although the concentration was below surface water standards, the concentrations were significant with respect to ground water. Therefore, EPA directed that an investigation be performed by the Group to find the source of contaminants in this area to protect ground water.
A drilling and sampling program in the Winter of 2006 found an area that contained very high concentrations of VOCs that could serve as a large source of most of the groundwater contamination in the landfill area. It became apparent that attacking this contamination would yield benefits in terms of shortening the remedy cleanup time, minimizing the migration of contamination, and reducing the cost. Following a pilot test in winter of 2007, EPA, the State, and the Group determined that a soil vacuum extraction system would best recover contaminants from this area. The operation of the soil vapor extraction system began in the Spring of 2009. The quarterly progress report issued on October 10, 2011 found that the soil vacuum extraction system had removed 41,812 lbs of contaminants from the subsurface at that time.

The air sparging/vacuum extraction recovery system was shutdown for evaluation of rebound and natural conditions and not operated during summer 2012. Quarterly monitoring will be performed to determine if remedial goals for this area have been attained.


Southern Plume Management of Migration Remedy Ground water monitoring in the area south of the landfill prior to 2004 indicated that contaminants may be migrating towards the Bellamy Reservoir. The Group conducted a pre-design investigation in 2006 to further characterize the contamination and to help design a remedy to intercept and treat the contaminants.
The report to EPA found that contamination had not migrated to the reservoir. Based on the findings of the report, the Group designed a management of migration remedy that is located near the toe of the landfill slope to minimize the spread of contamination and focus on the higher concentrations. A pilot-scale remedy began operation in April 2008 and full-scale operation began during the Summer of 2008. Recovery is discontinued during the Winter and resumes operation in the Spring. The quarterly progress report issued in October 2011 found that the system has removed 14.5 lbs of contaminants from groundwater in the Southern Plume.

Operation of this remedy was halted during the summer of 2012 to evaluate the performance of the just-constructed source control remedy which began recovering contaminated groundwater along the southern and eastern sides of the landfill in February 2012. Monitoring will be performed to determine if further operation of the Southern Plume is required.


Air-Sparging Trench Pre-Design Investigation In the 2004 AROD, EPA selected an air-sparging trench to serve as the source control remedy which would intercept and destroy or capture contaminants flowing from the landfill to the ground water surrounding the site. This remedy would have required a wall over 3,000 feet long and as deep as 100 feet in some areas and was quite complex.
The Group performed pre-design investigations over the Summer of 2007. Following a review of the pre-design data and discussions between EPA, the State, and the Group, it was determined that the air-sparging trench remedy may be ineffective at attaining the performance objectives set forth in the 2004 Amended ROD. Based on these considerations, EPA issued an Explanation of Significant Differences on June 30, 2009.


June 30, 2009 Explanation of Significant Differences EPA issued an Explanation of Significant Differences in 2009 which changed only the air-sparging trench component of the overall remedy to a ground water extraction system. Subsequently, the Group designed a groundwater extraction system along the edge of the landfill and began implementation of that system, the Source Control Remedial Action, during the Spring of 2011.

Source Control Remedial Action -- Ground Water Extraction System On September 30, 2010 EPA approved, with changes, the Source Control Remedial Design for ground water extraction along the edge of the landfill. Construction of the remedial action began during autumn of 2010, was discontinued over the winter and resumed in the Spring of 2011. The system started operation in February 2012 to shake-down the components. A final construction report was submitted by the Dover Group and the EPA issued a Preliminary Closeout Report, finding that all active, remedial construction was complete on September 6, 2012. The final construction consisted of the installation of 17 extraction well clusters with associated infrastructure that will extract contaminated groundwater from the subsurface and discharge it to the Dover Wastewater Treatment Plant for treatment and disposal. Design flows are for greater than 100 gallons per minute. During the period from February 2012 to October 2012 more than 12 million gallons of water have been removed from the site.

Eastern Plume Pre-Design Investigation In 1991, EPA determined that the Eastern Plume of contaminated ground water would be allowed to naturally attenuate after the Source Control remedy was built. Therefore, no active remedy was proposed for this area of the site. EPA's 2004 AROD did not alter the 1991 decision.
The Dover Group will monitor groundwater in the Eastern Plume, consistent with the approved sampling plans sufficiently to allow EPA and the State to determine the success and extent of natural attenuation of contaminants in the Eastern Plume.


Enforcement HighlightsThe State and City Council ordered the landfill closed in 1980. The potentially responsible parties entered into a Consent Decree in 1993 to perform the Record of Decision (ROD) remedy, capping the landfill, and pumping and treating contaminated ground water. The provisions of that Consent Decree and ROD were put on hold, by a 1997 Administrative Order on Consent between all parties, in order to determine whether a bioremediation remedy was superior in comparison to the 1991 ROD remedy. EPA and the State determined that the bioremediation remedy was not superior; however, found that an alternative remedy was superior to the original remedy.
EPA issued an Amended Record of Decision in September 2004 outlining the decision to keep the original source control remedy as a contingent remedy, and selected a new source control remedy that would intercept contaminants at the landfill's perimeter and treat contaminated ground water. EPA, the State and the PRP Group have negotiated a new Consent Decree to implement the remedy outlined in the 2004 Amended Record of Decision. The Second Consent Decree for this site was signed by the Regional Administrator on April 15, 2008, lodged on May 15, 2008, and was entered by the Court on November 14, 2008.

During negotiations on the terms of the Second Consent Decree, the Group agreed to voluntarily continue with many of the investigations and pilot tests needed to move the site closer to implementation of the final remedy. These investigations enabled the implementation of the Southern Plume groundwater extraction and the Northwest Landfill soil vacuum extraction remedies.

EPA also determined that a portion of the Source Control remedy needed to be changed to better intercept contaminants and issued an Explanation of Significant Differences (ESD) on June 30, 2009. EPA also changed the Statement of Work to the Amended Consent Decree to reflect the changes brought about by the 2009 ESD.

Environmental Progress
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By installing a water line to residences along Tolend Road and other areas near the site, the Dover Municipal Landfill does not currently present an immediate risk to these nearby residents. More than 41,000 pounds of contaminants were removed from groundwater in the northwest portion of the landfill and 14 pounds of contaminants were removed from the aquifer in the Southern Plume. Groundwater extraction which began in February 2012 is removing between 70 and 100 gallons of contaminated groundwater from the landfill area every minute. Monitoring will continue to ensure that contaminants are being intercepted and declining in areas outside of the landfill.

Current Site Status
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The activities that are expected to occur in the remaining portion of 2012 and through 2013 include:

1. Continued operation of groundwater extraction system.
2. A public meeting (date to be determined during Winter 2012-2013) will be held to discuss progress and future efforts.
3. The existing environmental monitoring plan will be modified to determine the success of remedial efforts and ensure minimal risk to public health and the environment.
4. Quarterly Reports detailing remedial progress will continue to be issued in January, April, July and October of each year.

Site Photos
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SDMS 452943
Aerial photo taken from GoogleEarth in 2008 (aerial photography date is unknown). The Bellamy Reservoir is the dark area in the lower left corner and the Cocheco River winds from the north to southeast in the upper, right-hand corner of the photo. The 50 acre landfill is the cleared area in the middle of the photo. The yellow line is the Dover/Madbury boundary. Ground water flow is generally to the east and the Cocheco River although there is a small component to the south and the Bellamy Reservoir.

View of housings for source control groundwater extraction wells (EW) 13, 14, and 15. Below is EW 11 and the office building.


Links to Other Site Information
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Disclaimer Instructions about PDF

Newsletters & Press Releases:
Press Releases about this project  
Please Edit this Label  

Federal Register Notices:
Final NPL Listing  
Federal Register Notice of Lodging of Second Consent Decree, May 23, 2008 (2.97 MB)  

Administrative Records:
Record of Decision (ROD) Administrative Record (AR) Index , September 10, 1991 (763 KB)  
Index Only: Administrative Record, OU01 Record of Decision (ROD) Amendment, September 30, 2004 (113 KB)  
Index Only: Administrative Record, OU01 Explanation of Significant Differences (ESD), July 1, 2009 (241 KB)  
Record of Decision (ROD) Administrative Record (AR), September 10, 1991 (241 KB)  

Reports and Studies:
Amended Proposed Plan, June 2004 (292 KB)   
Site Management Plan, April 5, 2005 (3.49 MB)  
Site Management Plan Addendum, January 20, 2010 (1.54 MB)  
Source Control Focused Feasibility Study, February 20, 2009 (Opening file is 31.2 MB with links to external PDF file)  
Southern Plume Management of Migration, Interim Remedial Action (RA) Report with Approval Letter, September 14, 2009 (9.37 MB)  
Data Transmittal for the Spring 2010 Environmental Monitoring Plan and Third Groundwater Management Permit Monitoring Event, October 13, 2010 (15.1 MB)  
Draft Source Control Remedial Action Work Plan (SCRAWP), December 29, 2010 (14.6 MB)  
Final Source Control 100% Remedial Design (RD) Report, December 29, 2010 (77.5 MB with links to additional PDF files)  
Quarterly Progress Report, January to March 2011, April 10, 2011 (82.2 MB)  
Final Source Control Remedial Action Work Plan, March 24, 2011 (44.2 MB)   
Environmental Monitoring Plan and Groundwater Management Permit First Monitoring Event (Spring) 2011, December 19, 2011 (41.2 MB)  
Preliminary Close-Out Report (PCOR), September 6, 2012 (1.7 MB)  
Quarterly Progress Reports, January 2009 - present   

Decision Documents:
View Records of Decision (RODS) on-line (EPA HQ)  
Record of Decision (ROD) Amendment, OU01, September 30, 2004 (7.7 MB)  
Explanation of Significant Differences (ESD), OU01, June 30, 2009 (2.94 MB)  

Settlement Documents:
Second Consent Decree with Notice of Lodging, May 13, 2008 (34.12 MB)  

Other Links:
NPL Site Narrative at Listing:  
Site Progress Profile  

Site Repositories
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Dover Public Library, Carnegie Building, 73 Locust Street, Dover, NH, 03820

OSRR Records and Information Center, 1st Floor, 5 Post Office Square, Suite 100 (HSC), Boston, MA 02109-3912 (617) 918-1440


Contacts
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EPA Remedial Project Manager: Darryl Luce
Address: US Environmental Protection Agency
5 Post Office Square, Suite 100
Mail Code: OSRR07-1
Boston, MA 02109-3912
Phone #: 617-918-1336
E-Mail Address: luce.darryl@epa.gov

EPA Community Involvement Coordinator: Rodney Elliot
Address: US Environmental Protection Agency
New England Regional Laboratory
11 Technology Drive
Chelmsford, MA 01863-243
Phone #: 617-918-8372
E-Mail Address: elliott.rodney@epa.gov

State Agency Contact: Andrew Hoffman
Address: NHDES 29 Hazen Drive, PO Box 95
Concord, New Hampshire 03302-0095
Phone #: 603-271-6778
E-Mail Address: andrew.hoffman@des.nh.gov

 


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