Client: Former Gasoline Retailer

Project: UST Closure / Oxygen Release Compound Remedial Action

Location:  New York

Description:  The property was a former gasoline service station that was constructed in 1929 and operated into the late 1990s.  In recent years, it was used solely as an auto repair shop.  The property was situated in an area of mixed commercial and residential use.  Prior to the tank closure activities, ground water sampling at the property (through the use of temporary sampling points) showed concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX) contaminants at 22,900 parts per billion (ppb) in ground water.  Additionally, soil contamination was also documented at levels exceeding the New York State Department of Environmental Conservation (NYSDEC) Soil Cleanup Criteria.

A 2,000-gallon and 4,000-gallon UST were known to be present at the property when the tank closure activities commenced.  The two USTs were removed from the site in accordance with New York State and federal protocols, and disposed of properly at a scrap recycling yard.  Two additional sand-filled 1,000-gallon USTs were discovered during the tank closure activities.  No physical evidence of residual petroleum product was noted in the two sand-filled USTs, and they were subsequently removed from the excavation and disposed of at a scrap recycling yard.   

Over 700 tons of petroleum-impacted soils were removed from the property, and post-excavation samples indicated compliance with NYSDEC soil regulations; however, significant ground water  impacts remained, and had to addressed to achieve site closure.  A Remedial Action Report (RAR) was submitted to the Westchester Country Department of Health (WCDH), and the client received a No Further Action letter (NFA letter) for soils, based on the UST closure activities and soil excavation work. 

Representatives from the NYSDEC and the WCDH approved a plan proposed by EWMA to apply Oxygen Release Compound (ORC) into the tank excavation, at the soil/groundwater interface zone, in an attempt to greatly accelerate the natural biological degradation of petroleum products contamination in ground water.  After applying the ORC into the excavation and backfilling the area, monitoring wells were installed and sampled per NYSDEC requirements.  Initial results, following the application of ORC, indicated that the initial 22,900 ppb concentration of BTEX compounds had been reduced to 2,200 ppb.  The most recent round of ground water sampling (3 rounds in total) indicated that total BTEX concentrations are now down to 75 ppb, indicating that the application of ORC had accelerated the natural biodegradation of the petroleum.  The alternative cleanup approach, a costly pump and treat system, would have likely taken years to bring total  BTEX concentrations down to similar levels.  The complete removal of residually contaminated low permeability soils down to shallow bedrock, in combination with the ORC application, circumvented many years of costly pump and treat remediation, and allowed site development to move forward.

Based upon the sampling results, the WCDH approved a natural attenuation program for monitoring ground water at the property.  The property has achieved compliance with New York state environmental cleanup standards and is being redeveloped.