Site investigation during upgrade design for two million-gallon+ drinking water tanks identified hazardous waste levels of lead and PCBs that require assessment and remediation and coordination under the Massachusetts Contingency Plan MCP and EPA’s Toxic Substances Control Act (TSCA).

Initial testing to pre-characterize soil for off-site disposal during tank upgrade activities identified lead and PCBs concentrations that exceeded the applicable Massachusetts Contingency Plan (MCP) reportable concentrations. Subsequent assessments to delineate contamination identified some soil as a characteristic hazardous waste due to leachable lead concentrations and PCB concentrations that exceeded the MCP Imminent Hazard (IH) and EPA’s Toxic Substances Control Act (TSCA) regulatory thresholds. Contaminant delineation to address the potential (IH) identified elevated concentrations to extend onto neighboring properties and Nobis supported the Town with immediate response actions to isolate workers, trespassers, and residents from contaminated soil.

Site reporting included complex contaminant distribution mapping throughout several soil horizons, MCP Phase I ESA report, an IRA Plan, an IRA Completion Report, and TSCA notification letters. Outreach included coordination with neighbors for site assessment, condition reporting, and implementation of Site controls During the IRA.

Nobis is performing site assessments and remedial planning in response to active involvement with EPA. Remedial and reuse planning tied to the remedial action are ongoing and based on collaboration with the Town and water tank upgrade design engineer to develop a cost-effective solution to be implemented during construction activities to upgrade the water tanks.

challenges

  • The water tank site poses increased safety concerns due to a dense subsurface network of water conveyance related to public water supply and communications infrastructure related to telecom companies that lease the water tanks as “towers” for cell, data, and communications antennas and appurtenances.
  • Potential hazards from elevated PCB concentrations extend into Site areas frequently impacted by construction and maintenance workers, and by residents at neighboring properties.
  • Contaminant distribution extended into complex site areas including areas of shallow bedrock, steep slopes, and heavily vegetated forest. EPA-approved remediation plans require an intense sampling effort if assessment data is to be used to verify contaminant cleanup.

solutions

  • Geophysical surveys, complex coordination with site tenants for utility mark out, and use of vacuum extraction and hand tools to advance borings and collect soil samples were protective of high value and imperative infrastructure. Nobis leveraged a site survey to accurately locate utilities and sample locations for precise remediation planning.
  • Nobis coordinated hazard communication, IRA implementation, and public outreach with the Town to implement site controls and notify workers and neighbors about Site conditions.
  • Nobis collected over 300 samples from 150 difficult-to-access locations to identify contaminant distribution and potential IH areas, support the remedial design, and establish a sample set suitable for use for remedial confirmation.

results

Nobis successfully advanced borings and implemented Immediate Response Actions to address potential IH conditions and regulated concentrations of lead and PCBs on a municipal water tank site and adjoining residential property. Site conditions such as dense utility networks and difficult topography complicated sample collection, however, Nobis’ specialized sampling approach promoted accessibility to sample locations and was protective of delicate infrastructure.

Nobis coordinated assessment activities with EPA and MassDEP to develop a cost effective approach to data collection that could minimize sampling to be performed during remedial activities. Nobis is working with the Town and design engineer to develop an economical remedial approach to be implemented during construction activities to upgrade the water tanks.