Overcoming the Challenges of Continuous NAPL Remediation

During the years 1988 to 1992, approximately 57,500 gallons of product was released into the environment at a bulk loading and storage facility for gasoline and other refined petroleum products. The area was constructed in the early 1900s and occupies approximately forty acres, a portion of which is under the purview of Antea Group’s client. Approximately 12,625 gallons of product was recovered during initial abatement activities.

Environmental investigations at the site have been ongoing since 1986.  Investigations consist of the installation of approximately 136 soil borings and the construction of 105 observation/recovery wells. Groundwater at the site is being monitored bi-annually. In addition, an automated LEL monitoring system was installed to observe explosive vapors in the combined sewer system. This sewer system bisects the property and may provide an exposure pathway for contaminants. At present, the combined sewer system is being monitored continuously and sampled bi-monthly. Coordination of all these activities is no small challenge.

Remediation is being undertaken through a light non-aqueous phase liquid (LNAPL) recovery system. This recovery system uses 11 recovery wells equipped with air-operated pumps to remove LNAPL from the subsurface. LNAPL is then collected on-site and properly disposed of. Over 11,000 gallons of LNAPL have been recovered from the site and properly disposed of to date.

A soil vapor extraction (SVE) system is also utilized at the site. The SVE system comprises 11 wells connected to a regenerative blower, with vapor treatment provided by a catalytic oxidizer. With this system, over 950 gallons of LNAPL has been recovered from the site and destroyed. 

Additional remediation activity involves a groundwater treatment system which treats all groundwater and surface water associated with the project site. The water is treated with an air stripper and activated carbon filters, and then discharged into a river in accordance with an NPDES permit. Over 3,500,000 gallons of water have been treated at the site and discharged to date.

A Remedial Investigation Work Plan has been generated for the part of the site operated by Antea Group’s client, which consists of a site conceptual model. The site conceptual model was developed to identify and evaluate potential exposure pathways for on-site and off-site receptors. Based on current and historical data, further remedial investigations are necessary at the site. The investigations will include the installation of approximately 65 additional soil borings and the construction of approximately 25 additional observation wells.

The remediation systems utilized at the site are currently automated. They will continue to remove LNAPL and remediate groundwater for several years.