In New York, a property located on a bank of the East River and in a densely developed residential and commercial area, had its work cut out for it from an environmental remediation standpoint
The mission was to clean up the land and and then ultimately make one puzzle piece to a larger urban revitalization project that would be redeveloped as a public library and park ranger station.
The challenge was that the aromatic hydrocarbon-related coal tar at this urban brownfield site was not a remediation effort for the faint of heart. It would be tricky and painstaking. But in less than half a year's time, a process known as “S-ISCO” was implemented to make all the difference in the world in speed-to-completion time. S-ISCO is regarded as a safe and effective remedy for this type of coal-tar contamination, and it's accompanying aromatic hydrocarbon .
As a result, this five-month treatment project successfully contacted, desorbed and destroyed NAPL contaminants and reduced soil vapor contamination in a controlled process and, in doing so, avoided impacting the adjacent East River or the local community.
One of the team members on the cleanup was VeruTEK Technologies, which destroyed coal tar contamination at a former roofing products manufacturing site in New York City using Surfactant-enhanced In Situ Chemical Oxidation—the full name for S-ISCO. The urban site, surrounded by dense residential and commercial development along the shores of the East River, was contaminated with coal tar repurposed from a nearby manufactured gas plant (MGP) for the roofing manufacturing process.
VeruTEK conducted five months of S-ISCO injections that destroyed greater than 90% of coal tar-related contaminants including BTEX, PAHs and naphthalene in the targeted interval. The treatment consisted of injections of VeruSOL, VeruTEK’s patented plant-based surfactant and co-solvent mixture, and alkaline-activated sodium persulfate that were augmented by Wavefront Technology Solutions US Inc’s (Wavefront) Primawave pressure-pulsing injection enhancement technology, as well as the RemMetrik process to quantify subsurface contamination, optimize the treatment and measure its effectiveness S-ISCO was an integral part of the remedial implementation that will enable redevelopment of the Brownfield site as a public library and park ranger station.
The New York State Dept. of Environmental Conservation (NYSDEC) issued a Certificate of Completion to confirm the success of the cleanup. The successful destruction of MGP-related coal tar at the brownfield site demonstrates the effectiveness of S-ISCO as a remedy for MGP-related contamination.
Site Background
Located on a bank of the East River in a densely developed residential and commercial area in New York City, this 0.73-acre parcel is part of an urban revitalization project, and will be redeveloped as a public library and park ranger station.
As part of the history of roofing products manufacture at the parcel, MGP coal tar that was brought onto the site leaked into the subsurface, contaminating the soil and groundwater with benzene, toluene, ethylbenzene, and total xylenes (BTEX), naphthalene, and polycyclic aromatic hydrocarbons (PAHs).
Contaminant concentrations in the soil and groundwater exceeded the NYSDEC regulatory limits, including in a number of groundwater locations by orders of magnitude. The majority of contamination was present as residual non-aqueous phase liquid (NAPL) held within the pore spaces of the predominately sandy and silty soil that also included lenses of silt and silty clay. Traditionally these NAPL droplets, especially in fine soils such as the silts and clays present at this site, create a huge challenge to in situ treatments.
The S-ISCO technology was approved as part of the Brownfield Cleanup strategy for the site after the results of VeruTEK’s bench-scale treatability tests and pilot-scale field implementation demonstrated that the S-ISCO method could effectively contact and destroy contamination at the site, including sorbed NAPL. The laboratory and field-scale testing indicated that a S-ISCO treatment composed of VeruSOL-3 and alkaline-activated sodium persulfate was the optimal remedy for site contaminants, while the results of the pilot test also indicated that the incorporation of Primawave pressure-pulsing with S-ISCO injections enhanced the radius of influence and uniformity of dispersion for the injected chemistry.
Implementation
S-ISCO implementation took place between October 2010 and March 2011, and consisted of injections of VeruSOL-3, sodium persulfate and sodium hydroxide1 into 34 wells located in the areas in which the greatest contamination had been identified2. These wells were variably screened across 6 – 7 foot intervals between 10 and 22 ft bgs in order to target approximately 64,000 pounds of contamination. Injections took place at an average rate of 8 gallons per minute (GPM) per well to 4 wells at a time (32 GPM overall), and were augmented by the Primawave pressure-pulsing tool.
Monitoring
Monitoring was conducted before, during and after S-ISCO injections to track the progress and performance of the injected chemistry in the subsurface and to confirm that the treatment was not negatively impacting sensitive receptors, such as the adjacent river. Monitoring included: continuous tracking of water quality parameters using in situ data loggers; collection of groundwater samples for analysis in VeruTEK’s on-site laboratory; observation of all wells on and off-site for indications of NAPL; and collection of soil and groundwater samples for contaminant analysis.
Results
Approximately 5 months after the completion of injections, when the results of groundwater monitoring indicated that the sodium persulfate reactions had subsided, VeruSOL had largely degraded and pH conditions were approaching pre-injection levels, 114 soil grab samples were collected from the treatment area and analyzed for total VOCs and SVOCs3.
These results were used to calculate the mass of contamination remaining that was then compared to the mass calculated before treatment. This analysis indicated that the S-ISCO treatment destroyed 90.3% of the mass of total VOCs and SVOCs present before treatment, including more than 95% of the naphthalene present. Naphthalene, a principal component of coal tar, was one of the primary SVOCs affecting the site soils and groundwater; it accounted for almost 65% of the total pre-treatment contaminant mass. Table 2 shows additional reductions for priority contaminants, including benzene, toluene, ethylbenzene and total xylenes (BTEX).
Conclusions
The successful destruction of MGP-related coal tar at this urban Brownfield site demonstrates a clear success for S-ISCO and its safety and effectiveness as a remedy for MGP-related contamination. The five month S-ISCO treatment successfully contacted, desorbed and destroyed NAPL contaminants and reduced soil vapor contamination in a controlled process without impacting the adjacent water body (the East River) or the local community.
