Theme: 03. Green and Sustainable Remediation

Topic Area: 3c. Climate Resilience and Site Remediation

Formatted Title:

Addressing Unique Challenges and Flood Resiliency Measures for the Design and Construction of a Groundwater Conveyance System

Background/Objectives:

The American Cyanamid Superfund Site (a 435-acre site on the Raritan River in Bridgewater Township, New Jersey) was used for dye, chemical, and pharmaceutical manufacturing operations from 1915-1999. Historic operations included the use of impoundments for storage and disposal of waste resulting in impacts to site soil and groundwater. Site size and flood plain elevation present significant challenges that must be addressed as part of the remedy design, as it is prone to flooding and was significantly impacted by two major hurricanes (Floyd/1999 and Irene/2011). Previous Operable Units (OUs) at the site included installation and operation of a “temporary” groundwater extraction, conveyance, and treatment system. As part of the OU 4 remedial action, the following subcomponents were designed and constructed as part of the groundwater remedy: groundwater extraction and injection system (GWEIS), hydraulic barrier walls (HBWs), site-wide groundwater treatment facility (GWTF), and groundwater conveyance system (GWCS). Up to 720,000 gallons per day of overburden and bedrock groundwater can be treated in the new site-wide GWTF. The design and construction of the GWCS and associated infrastructure required consideration of multiple challenging site historical factors, geography, complexity, and anticipated future remedial activities. A proactive and collaborative design approach with multiple stakeholders led to successful construction and operation of the GWCS.

Approach/Activities:

The site consists of four, non-contiguous major areas (North, South, West, and Impoundment 8) that are intersected by public and private roads, a major stream, and railroads. The site is bounded on the south and west by the Raritan River and is subject to frequent and extensive flooding. The Record of Decision requires that flood resiliency measures be incorporated in the remedy design. Extraction wells are located throughout three of the major areas, and the site-wide GWTF is located separately. The GWCS force main routing accounted for: avoiding areas of concern, former building foundations and existing underground utilities; the use of existing utility structures and corridors; the use of available easements; and accessibility for testing, maintenance, and repairs. The design of associated infrastructure accounted for: protection during flood events; grading and construction of platforms above the 500-year flood elevation; and grading and elevations of utility enclosures to align with design goals for future remedial capping activities and eliminating confined space entry. The design also had to consider containment, operational flexibility, and hydraulic containment objectives. Multiple meetings with stakeholders were required to explore and refine concepts for the groundwater extraction system to address feasibility and operational goals. Reviews for safety, operability, and constructability were conducted during the design process to obtain stakeholder input and refine the design. The proposed remedial approach was approved by the New Jersey Department of Environmental Protection and United States Environmental Protection Agency in 2017.

Results/Lessons Learned:

Construction of the GWCS began in 2017 and was completed in 2019. Main obstacles during design and construction of the GWCS were encountered with former building foundations, underground utilities, the reuse of existing utility structures, retrofit of existing equipment while maintaining operations during construction, and work within an active parking lot. Operation of the system commenced in March 2019.

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Steven Giese