248 Flatbush Ave, Brooklyn, NY

North Slope

brownfield, CVOCs, VOCs, "Vapor Intrusion"

David and Gail Aronowicz
Site Description[1] 
Site Location: The BCP site is located at 248 Flatbush Avenue in Brooklyn, Kings County and is Block 936 and Lot 12. It is bounded to the east by Flatbush Avenue, to the south by NYCDDC's Eastern Parkway Project Resident Engineer's Field office, to the west by a courtyard for a restaurant, and to the north by a liquor store and restaurant. Site Features: The site is a one-story building with a full basement that encompasses the entire property. It is approximately 2,300 square feet and is currently vacant. There is no parking associated with the Site. The topography of the site is generally flat and the surrounding area slopes gradually to the northwest. Current Zoning/Use(s): The site was most recently used for commercial purposes. The buildings to the north appear to have residential apartments located on the floors above the businesses. Historical Uses(s): The building was constructed between 1888 and 1906 and most recently housed a dry cleaner and shoe repair facility for the last twenty years. Previous uses included clothing, book store and the sale of dry goods. Site Geology and Hydrogeology: Soils underlying the site are classified as Urban Land and consist of brown silty fine sand and brown to medium sand with some cobbles and trace fine to medium and coarse gravel. The nearest body of water is the Gownaus Canal located approximately 3,400 feet to the west-northwest of the site that flows into the Gowanus Bay. The site is serviced by city water provided by NYC Municipal Water.

Site Environmental Assessment
Soils - In 2005, an investigation focused on a reported historical leak of cooling water from the first floor dry cleaning machine into the basement boiler room. It was concluded that the subsurface soil beneath the boiler room was impacted by dry cleaning solvents based on elevated PID readings. The impacted soil appeared to be no deeper than 9 feet below the basement floor. Contaminated soil was excavated from the boiler room to a depth of 5 feet below the basement floor. Post-excavation samples resulted in trace levels of VOCs considerably below regulatory standards. Therefore, the excavated soils were disposed as non-hazardous waste and a manifest was not required. In April 2011, soil samples were collected and PCE was detected in five of the soil borings at concentrations ranging from 0.0026 ppm (SB-8B) to 0.18 ppm (SB-5B). These levels of PCE are well below the Part 375 unrestricted use SCO. Groundwater - In 2005, analytical results for groundwater indicated that PCE was present at concentrations of 285 ppb, which is above the regulatory standard of 5 ppb. In 2011, groundwater samples were collected from three temporary wells installed through the basement floor. Analysis of samples from TW-2 and its duplicate (DUP) detected PCE at 12 ppb and 69 ppb, respectively. Analysis of groundwater samples from TW-3 and its duplicate (DUP-3), and the re-analysis of DUP-3, identified PCE at 21 ppb, 25 ppb, and 19 ppb, respectively. Soil Vapor - In August 2011, on-site vapor intrusion investigation activities included the collection of three sub-slab soil gas samples, three indoor air samples and one ambient air sample. PCE was detected in the indoor air at concentrations ranging from 1.7 ug/m3 to 24.4 ug/m3, and in the sub-slab at concentrations ranging from 4,010 to 20,800 ug/m3. (Previously in 2007, the sub-slab concentrations ranged from 5,000 to 607,000 ug/m3.) According to the NYSDOH Matrix 2 for PCE, mitigation to minimize vapor intrusion and subsequent human exposures is recommended. In 2011, an off-site vapor intrusion evaluation also was performed at adjacent properties to ensure that no other receptors were being impacted. Six sub-slab, three indoor air, and one ambient air samples were collected at 250 Flatbush Avenue (Engineers Office), 252 Flatbush Avenue (Cash for Gold), and 80 St. Marks Street (on the other side of the adjacent Japanese Restaurant). At 250 Flatbush, PCE was detected in sub-slab vapor at concentrations ranging from 454 ug/m3 to 1,480 ug/m3, and in indoor air at 12.1 ug/m3. At 252 Flatbush, PCE was detected in sub-slab vapor at concentrations ranging from 185 ug/m3 to 450 ug/m3, and in indoor air at 2.67 ug/m3. At 80 St. Marks Avenue, PCE was detected in sub-slab vapor at concentrations ranging from 3,810 ug/m3 to 20,400 ug/m3, and in indoor air at 30.3 ug/m3. According to the NYSDOH Decision Matrix 2 for PCE, the indoor air and sub-slab results at 250 Flatbush Avenue and 80 Marks Street indicate that mitigation is recommended. The results at 252 Flatbush Avenue indicate that monitoring is recommended.

Site Health Assessment
Direct contact with contaminants in soil is unlikely because the site is covered with buildings. People are not drinking the contaminated groundwater because the area is served by a public water supply that is not contaminated by the site. Volatile organic compounds in the groundwater may move into the soil vapor (air spaces within the soil), which in turn may move into overlying buildings and affect the indoor air quality. This process, which is similar to the movement of radon gas from the subsurface into the indoor air of buildings, is referred to as soil vapor intrusion. Indoor air impacts that may be the result of soil vapor intrusion have been identified in one on-site building and three off-site structures. However, the levels of contaminants in the indoor air of these buildings do not exceed NYSDOH air guidelines. The NYSDOH has recommended that three of these structures (one on-site and two off-site) be mitigated to minimize the potential for vapor intrusion to occur in the buildings. Additional investigation in to the potential for vapor intrusion and subsequent human exposures at additional off-site structures is warranted.

Contaminants of Concern
Type of Waste Quantity of Waste
TETRACHLOROETHYLENE (PCE) UNKNOWN
  1.  DEC Environmental Site Remediation Database.  Site Name: "Cinderella 248 LLC".

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