The Holyoke Gas Works operated from 1852 until 1951, playing an important role in the industrial development of the city of Holyoke, Massachusetts. During its operation, over 15 billion ft~3 of gas was generated and approximately 10 million gallons of tar was produced. A legacy of these activities included episodic releases of tar to the Connecticut River, resulting in the deposition of hardened, asphalt-like tar patches on the river bottom. Approximately 1200 yd~3 of tar has been identified in twelve discrete patch areas scattered up to 2.2 miles downstream of the gas works. Owing to the presence of the shortnose sturgeon, a federally protected endangered species, removal of the tar deposits has been mandated by the National Oceanographic and Atmospheric Administration, in addition to the Massachusetts Department of Environmental Protection. Remediation is complicated by significant technical and logistical challenges, including: defining attainable clean up goals; limited site access imposed by concrete and earthen flood barriers, industrial outfall structures, and bordering wetlands; and large variations in river velocity and depth. Various studies were conducted to evaluate these issues and prepare a final remediation design. Two remedial approaches utilizing conventional excavation equipment in either submerged or dewatered enclosures have been developed. Both scenarios require flow diversion or water containment measures such as Portadams? and silt curtains. Other concerns include the need for barges, cranes, and water pumping and treatment facilities to support removal activities.
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