1.1.2 Site Description

1.1.2.1 Location

The Former Synergy Site is adjacent to the north and eastern bank of the Sugar River near the center of the Town of Claremont on the western side of the intersection of North Street and State Route 11.  The Lower Cul De Sac Place property has also been referred to in the past as 59 Broad Street.  The approximate latitude and longitude is N 43º22’28” and W 72º20’15”, respectively.  The north, northeast and eastern edges of the Site border a steep rise up to North Street and the Sugar River borders the western edge.  The southern portion is bordered by an asphalted Cul De Sac, which continues up to Broad Street.  Residential and commercial buildings are on the far side of North and Broad Streets.  A revitalized mill containing a hotel, restaurant, and various commercial enterprises are across the Sugar River to the west.

1.1.2.2 Description of Threat

This Site is the location of a defunct manufactured gas plant (MGP) which is heavily impacted by an oily waste product (coal tar).  The product appears to be the residual from the historic manufactured gas process.   Coal tar is a brown or black liquid, which smells of naphthalene and aromatic hydrocarbons and is among the by-products when coal is carbonized to make coke or gasified to make coal gas.  Visual observation, field instrumentation, and laboratory data indicate that approximately two-thirds of the Site is impacted by coal tar.  The oily product is perched on bedrock, is leaching into the adjacent Sugar River, and has been detected in numerous surface soil samples above state standards.  Minimal disturbances of surface sediments in the river caused visible sheening.  Constituents of the product include semi-volatile organic compounds (carcinogenic and non-carcinogenic polynuclear aromatic hydrocarbons [PAHs]) and to a lesser degree, volatile organics and inorganics.

1.1.3 Preliminary Removal Assessment/Removal Site Inspection Results

During the 2010 preliminary assessment/site inspection (PA/SI), soil core samples were collected in 10 locations throughout the property at varying depths from 0-9’ below grade and two sediment samples were collected at the river’s edge at approximately 1’ below grade.  In all 12 locations, 1 or more PAHs were detected at levels higher than the New Hampshire Department of Environmental Services (NH DES) Method 1 S-2 Soil Standards.  These standards apply to sites where exposure may occur to a receptor that comes in contact with the contaminated soils in a work environment or in a passive recreational setting.  In many cases, the concentrations detected were an order of magnitude higher than the S-2 standards and in some cases, 2 orders of magnitude higher.

The Department of Health and Human Services (DHHS) has determined that benz[a]anthracene), benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene,  and indeno[ 1,2,3-c,d]pyrene are known animal carcinogens. The International Agency for Research on Cancer (IARC) has determined the following: benz[a]anthracene and benzo[a]pyrene are probably carcinogenic to humans; benzo[b]fluoranthene, benzo[k]fluoranthene, and indeno[ 1,2,3-c,d]pyrene are possibly carcinogenic to humans.  EPA has determined that benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, dibenz[a,h]anthracene, and indeno[ 1,2,3-c,d]pyrene are probable human carcinogens. 

Other hazardous constituents that have not been determined by DHHS, IARC, or EPA to be carcinogenic, but also exceeded the NH DES Method 1 S-2 Soil Standards were fluorene, 2-methylnapthalene, naphthalene (PAHs); 1,2,4-trimethylbenzene, ethylbenzene (volatile organics); and arsenic and lead (inorganics).

All constituents identified above are listed in 40 CFR §302.4, table 302.4, CERCLA List of Hazardous Substances.

As previously mentioned, the Site is adjacent to the Sugar River.  When samples were collected at the rivers’ edge during the original PA/SI, a slight disturbance of shallow sediment resulted in a sheen to the water.  During the second EPA assessment in 2012, divers were used to collect sediment and water samples and to help determine if the site was discharging groundwater (and accompanying coal tar) to the river or if the river was recharging to the site.  While performing these tasks, a number of oily rainbow sheens and some free product (and accompanying odors) were seen emanating from the work areas. Slight disturbance of the sediment caused by either walking or probing appeared to have caused the release of coal tar that was perched on bedrock or settled into rock fissures.  According to city officials, at times of low river flow such as late summer, coal tar can routinely be seen emanating from the river bed at the edge of the Site property.  The river is classified by the State of New Hampshire as a class B waterway, considered to be fishable and swimmable.  There are at least two water intakes (non potable) within 1 downstream mile.

Surface soil sampling (0-3”) conducted in 2012 showed that state standards for PAHs were exceeded in 11 of 12 samples for a minimum of at least one constituent.  A petrochemical odor of varying intensity is usually present throughout the site, depending on the time of day and year as well as temperature, wind conditions, and humidity.