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Waste Site Cleanup & Reuse in New England
  Serving Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont & 9 Tribal Nations
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 Site Type: Long Term/National Priorities List (NPL) Click to see more about Site Type and how it is used?


Map this site in Cleanups in My Community
 Westborough,  Massachusetts
 Worcester County
 Street Address: Otis Street
 Zip Code: 01581

 EPA ID #: MAD980732341
 Site ID #: 0100751
 Site Aliases:

 Site Responsibility: Federal, Potentially Responsible Parties

 Proposed Date 12/30/1982
 Final Date 09/08/1983

Site Description
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The 23-acre Hocomonco Pond site located in Westborough, Massachusetts is bordered on the northwest by Hocomonco Pond, a 27 acre shallow, freshwater pond which has long been used for recreational purposes. From 1928 until 1946 the site was used as a wood-treating and preservation operation. The business consisted of saturating wood products (e.g. telephone poles, railroad ties, pilings and fence posts) with creosote to preserve them. During the treatment process, excess creosote and wastes where discharged to an unlined pit, referred to herein as the "former lagoon".

The former lagoon was excavated on the site to intercept and contain spillage and wastes from the wood treatment operations. As this lagoon became filled with creosote waste, sludges and water, the contents were then pumped into two low depressions located east of the site operations, near the west side of Otis Street. These depressions are referred to as "Kettle Pond". The available records indicate that no creosote was used or stored on the site after March 26, 1946. The last use of the site was as a cement plant where dry cement was distributed in bulk. The sediments, surface water and groundwater had shown creosote contamination. As of 2000, approximately 18,000 people and 6,534 households are located within the town of Westborough. Residential areas are located less than a half mile northeast and southeast of the site, although the adjacent property use is commercial.

Threats and Contaminants
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The groundwater, soil, and sediments from the pond and its shore were contaminated with creosote, which contains carcinogenic polyaromatic hydrocarbon (PAH) compounds. Pure creosote exists as a pool of dense non-aqueous phased liquids (DNAPL) approximately 120 feet below the ground surface. To prevent a potential exposure to the contaminants located 120 feet below the ground surface, no groundwater production wells are allowed at the site. Preventing direct exposure to the creosote and the removal of contaminated sediments has addressed unacceptable risk(s).

Cleanup Approach
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The site is being addressed in long-term remedial phases which focused on source removal and control, constructing a landfill, constructing a cap on the former lagoon, sediment removal and placement and removal of DNAPL.

Response Action Status
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Interim Source Control In the 1970's, a storm drain pipe was installed across the Site which, unknowingly at the time, had been excavated through the on-Site lagoon. This caused the transport of liquid contaminants to Hocomonco Pond. The parties potentially responsible for site contamination completed relocation of the storm drain pipe located along the east side of the former lagoon in 1990.

Landfill and Groundwater Treatment In 1985, final cleanup remedies were selected in a Record of Decision (ROD) for the Site. During pre-design studies conducted in 1988 to 1992, a significant amount of contamination was discovered in the deeper soils at the Kettle Pond area, which caused the original remedy to be re-evaluated. An Explanation of Significant Differences (ESD) was issued in 1992 which modified the Kettle Pond remedy. The potentially responsible parties began constructing the remedies in the fall of 1993. Remedial activities consisted of excavating the top 4 to 5 feet of contaminated sediments and soils within the Kettle Pond area (4,500 cubic yards). The top 6 inches of contaminated sediment, extending approximately 20 feet from the shore line, was excavated from Hocomonco Pond (2,300 cubic yards) and an associated discharge stream located beyond a culvert running under Otis Street was dredged (500 cubic yards). All excavated soil and sediment were placed in a double lined landfill constructed on-Site. It was seeded with grass and completed in 1996. Also in 1996, soil from the former tank farm area was excavated (3,660 cubic yards) and composited in the former lagoon area, located just west of the landfill. The former lagoon area was then capped and seeded with grass. A groundwater treatment plant was designed and constructed on-Site to recover DNAPL and treat associated groundwater. It began operation in 1994. In March 1996, an in-situ bioremediation system was integrated with the groundwater treatment plant. However, the bioremediation system operated for only a couple of weeks before it was suspended due to heavy fowling from naturally occurring iron. The persistence of the DNAPL pool below the groundwater table creates a limitation that makes groundwater remediation technically impracticable. A second ESD establishing a Technical Impracticability (TI) Waiver was approved by EPA and MassDEP in September of 1999. The TI waived the groundwater clean up goals within two defined TI zones. One of the conditions of the TI waiver includes long term sampling and monitoring of sediments and groundwater, and continued recovery of DNAPL. The groundwater treatment plant ceased operations in 2003. Since that time, passive recovery of DNAPL has been performed. The decision to continue passive recovery was documented in a third ESD issued in September of 2013. Currently, about 60 to 100 gallons of DNAPL are recovered on a monthly basis. Since 1995, more than 65,000 gallons of DNAPL have been removed.

Enforcement HighlightsA Consent Decree was filed in the U.S. District Court in 1987, requiring the potentially responsible parties to design and construct the selected remedy.

Environmental Progress
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Grading, capping, soils removal, relocating a storm drain pipe, constructing a landfill, dredging of sediments, removal of DNAPL and monitoring of groundwater have made the Hocomonco Pond site safe by preventing contact with contaminants that pose an unacceptable risk.

Current Site Status
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Currently EPA and MassDEP are evaluating requirements for the future Long Term Monitoring requirements for sediments, groundwater and the continued recovery of DNAPL from over 120 feet below the ground surface. EPA and the MassDEP have been working with the property owner (the Town of Westborough) to develop potential protective redevelopment/re-use plan for the Hocomonco site.

In the near future, the Town of Westborough would like to preserve the site as open space and to redevelop the property into a passive recreational walking and/or biking trail along the shore of Hocomonco Pond that meanders through the site. The Town is also exploring the possibility of using the site to construct solar panels. Long term groundwater and sediment monitoring and DNAPL recovery will continue to ensure that the remedies are and will remain protective for human health and the environment. The First Five Year Remedy Review was completed in September of 2004, the Second Five Year Review in September of 2009, and the Third Five Year Review in September 2014. They conclude that the remedies for the Hocomonco Pond site are expected to remain protective of human health and the environment once the deed restrictions are in place. The property remains fenced at the perimeter and there has been no evidence of trespassing.

Site Photos
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SDMS 452919

SDMS 452920

Links to Other Site Information
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Disclaimer Instructions about PDF

Newsletters & Press Releases:
Press Releases about this project  
A Cleanup Update, August 19. 1999 (155KB)  

Federal Register Notices:
Final NPL Listing  

Administrative Records:
Administrative Record (AR) Index, OU 01 Record of Decision (ROD), September 30, 1985 (417 KB)  
Administrative Record (AR) Index, Explanation of Significant Differences, October 2013 (513 KB)  
Administrative Record (AR) Index, Record of Decision (ROD), Operable Unit (OU) 1, September 30, 1985, (574 KB)  

Reports and Studies:
Five Year Review Report, September 21, 2004  
Second Five Year Review Report, September 30, 2009 (10.3 MB)  
Third Five Year Review Report, September 25, 2014 (3.99 MB)  

Decision Documents:
View Records of Decision (RODS) on-line (EPA HQ)  
Record of Decision (ROD), September 30, 1985 (8.72 MB)  
Explanation of Significant Differences (ESD), July 22, 1992 (776 KB)   
Explanation of Significant Differences (ESD), September 21, 1999 (618 KB)  
Explanation of Significant Differences (ESD), September 30, 2013 (4.98 MB)  
Institutional Controls at this Site  

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

Site Repositories
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Westborough Public Library, West Main Street, Westborough, MA 01581

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

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EPA Remedial Project Manager: Jim DiLorenzo
Address: US Environmental Protection Agency
5 Post Office Square, Suite 100
Mail Code OSRR07-4
Boston, MA 02109-3912
Phone #: 617-918-1247
E-Mail Address: dilorenzo.jim@epa.gov

EPA Community Involvement Coordinator: Pamela Harting-Barrat
Address: US Environmental Protection Agency
5 Post Office Square, Suite 100
Mail Code ORA01-1
Boston, MA 02109-3912
Phone #: 617-918-1318
E-Mail Address: harting-barrat.pamela@epa.gov

State Agency Contact: Jay Naparstek
Address: MA Department of Environmental Protection (MA DEP)
One Winter Street
Boston, MA 02108
Phone #: 617-292-5697
E-Mail Address: jay.naparstek@state.ma.us


Serving Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, & 10 Tribal Nations
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Last updated on Wednesday, November 4th, 2015
URL: http://www.epa.gov/region1/superfund/sites/hocomonco