76 11th Ave, NY, NY 10011

Chelsea

brownfield, VOCs, "Vapor Intrusion"

U.S. Drug Enforcement Administration, New York Division and ConEd
Site Description[1] 
Location: The 17th Street Development Project site encompasses the entire block between 17th and 18th Streets, and between 10th and 11th Avenues in the lower west side of Manhattan. Site Features: The site is flat and currently used as a parking lot, with no distinguishing features other than a former elevated rail line that cuts across the eastern edge of the site. The elevated rail line was recently converted to use as a city park - High Line Park. Current Zoning/Use(s): This site is currently zoned for commercial/residential. Surrounding Uses: The surrounding land use is historically commercial, but new residential development has been proceeding rapidly in recent years. Historic Use: Prior to its use as an Manufactured Gas Plant (MGP), the property experienced very little development, consisting of the construction of five houses which were torn down after about 20 years to make room for expansion of the MGP operations. The plant began distribution of coal gas in November 1834 and operated continuously until it shut down in 1901 or 1902. This site is one parcel in the larger Consolidated Edison W 18th Street Former MGP site, ID No. V00530. Most of the gas making and purification facilities of the MGP were located on this parcel. In 1932, the railroad acquired the property. Some of the buildings were razed and a rail yard was built. The remaining buildings were used for other uses. Later, the tracks were removed, the remaining buildings razed and the site used as a parking lot. In the 1950s an automobile fueling and service station was built on the west end of the site. In the 1980s the service station was demolished and since then the site has been used exclusively as a parking lot. 17th Street Development Corporation is the BCP Volunteer for this block/site only. The remainder of the former MGP site remains under the Con Edison Voluntary Cleanup Agreement. Site Geology and Hydrogeology: Between 50 and 80 feet of unconsolidated materials overlie schist bedrock at the site. The fill deepens significantly from east to west. Overburden consists of three distinct stratigraphic units. The top unit is fill, generally highly permeable, ranging from 13 to 45 feet thick. The upper 5 to 10 feet of fill contains significant man-made materials and the remnants of former structures and debris. Below that fill is mostly fine to medium or fine to coarse sand with trace brick, ash wood fibers and concrete. Buried in the fill along the western border of the site is timber cribbing that formed the shoreline and bulkhead at one time. Below the fill is a Silty-Clay Unit which forms a low permeability aquitard. Water and other liquids such as coal tar do not readily pass through this layer. It varies in thickness from 40 feet to as little as 2 feet. Below the Silty-Clay Unit is the Sand Unit, a moderately permeable aquifer ranging from 20 to 40 feet thick. Permeability is far greater in a horizontal direction than vertical. The water table is located approximately 9 feet bgs and nearly flat. Flow is generally toward the Hudson River to the west. In some areas, groundwater flow is influenced by man-made factors such as the Hudson River bulkhead, sheet pile walls, utilities, and by various man-made flows such as leaking water lines, drains, sewers, and building dewatering systems.

Site Environmental Assessment
Nature and Extent of Contamination: The Consolidated Edison investigations indicate that a significant amount of coal tar contamination is associated with the former MGP structures on this property. Soils saturated with coal tar are found at depths between 1.5 feet and 35 feet below ground surface. Wells spontaneously accumulate up to 8 feet of mobile tar. Groundwater and subsurface soil are contaminated with BTEX and PAH. Special Resources Impacted/Threatened: The heaviest concentration of coal tar is found along the western, downgradient edge of the site. MGP contamination appears to have migrated from this property primarily to the north and west, but has not yet been observed in the Hudson River 160 feet to the west of the site. Tar accumulates spontaneously (without pumping) in monitoring wells at the western property line, so off-site migration can occur readily. Off-site groundwater or soil gas contamination will be addressed as part of the overall remedy for the larger West 18th Street MGP site. Significant Threat: This site presents a significant environmental threat due to the presence of tar moving off-site in the direction of the Hudson River 160 feet away.

Site Health Assessment
People are not drinking the contaminated groundwater because the area is served by a public water supply that is not contaminated by the site. Direct contact with contaminated soil is unlikely since it is located under pavement. Volatile organic compounds in the groundwater and/or soil may move into the soil vapor (air spaces within the soil), which in turn may move into overlying or nearby 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. Although no buildings currently occupy the site, future site development is likely to include at least one structure and the potential for soil vapor intrusion will be evaluated. Any concerns related to soil vapor intrusion in nearby buildings will be addressed under the voluntary agreement for the West 18th Street MGP Site.

Contaminants of Concern
Type of Waste Quantity of Waste
ARSENIC UNKNOWN
benzene, toluene, ethylbenzene and xylenes (BTEX) UNKNOWN
COAL TAR UNKNOWN
CYANIDES(SOLUBLE CYANIDE SALTS) UNKNOWN
LEAD UNKNOWN
MERCURY UNKNOWN
Polycyclic Aromatic Hydrocarbons (PAHs), Total UNKNOWN
  1. DEC Environmental Site Remediation Database.  Site Name: "17th Street Development Project".

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