DNAPL Recovery System

DNAPL Recovery System

Significant Facts

  • Installed a network of 28 wells for DNAPL recovery and monitoring
  • Conducted hydro-fraction and steam sparking to enhance DNAPL Recovery
  • Dedicated pneumatic recovery pumps

Project Summary

True Blue completed installation of two dense non-aqueous phase liquid (DNAPL) coal tar recovery systems at a former gas works site in Holyoke, MA. The DNAPL recovery systems were installed as a Comprehensive Remedial Response Action in accordance with the Massachusetts Contingency Plan (MCP) 310 CMR 40.0870.

The first recovery system was installed adjacent to a raceway along the property’s northern boundary. The system consisted of three recovery wells equipped with dedicated pneumatic pumps. These pumps were plumbed directly into a systems control shed where the DNAPL was collected in a recovery tank pending off-site disposal.

The second recovery system, located in the southeastern portion of the Old Gas Works site, consisted of a steam-enhanced recovery system with pneumatic pumps plumbed to an above ground storage tank.
Prior to installation, True Blue conducted hydraulic fracturing within the recovery horizon to create a sub-gradient conduit within the lithostratigraphic unit to facilitate steam sparging and DNAPL recovery.

True Blue work included the expansion of the recovery system with the installation of twenty-two (22) additional recovery wells. The new wells included three bedrock recovery wells and nineteen overburden wells. Each of the new recovery wells are fitted with dedicated pneumatic recovery pumps. Each recovery well is plumbed with polyethylene air hoses and NAPL recovery lines, which are connected to a manifold located at the system control shed. All air and recovery lines were bundled and placed inside heat traced underground PVC conduits.

Inside the shed, the recovery line manifold is plumbed to discharge to the recovery tank. The recovery tank is fitted with both a high level shut off mechanism and auto-dialer alarm system. Secondary containment minimizes the possibility of an uncontrolled release.