The Site is an approximate one-acre portion at the north-west corner of the approximate seven-acre parcel of real property located at 672 Concourse Village West, Block 2443, Lot 78, in the South Bronx, New York. The adjacent properties include Primary School No. 156 and Intermediate School No. 151 to the north; New York and Harlem Railroad to the east; New York and Harlem Railroad and Cardinal Hayes High School to the south; and apartment buildings, Herk Elevators, Live Poultry and Nationwide Warehouse to the west. The Site is located in a topographic depression. the properties to the north and west are approximately 30 feet higher than the Site. To the north, Primary School No. 156 and intermediate School No. 151 are constructed on 30-foot-high concrete columns. The properties to the west are separated from the Site by a 30-foot-high retaining wall. The properties to the south are at approximately the same elevation as the Site. To the east of the Site, the ground again rises to approximately 20 feet above the Site. The Site has been a railyard since 1891, with a machine shop, paint area, carpenter shop, and electrical warehouse located to the west of the property. All of these buildings were demolished between 1951 and 1977, and the Site remains undeveloped to the present day. Remedial Investigation was completed in 2006, and the Remedial Action Work Plan was approved in July 2006. Remedial Action (RA) was initiated in August 2006. Excavation is completed. A draft Site Management Plan has been submitted.
Site Environmental Assessment
Shaw Environmental completed site investigation activities between March and September 2005. The findings of the Remedial Investigation (RI) identified soil and groundwater contamination above NYSDEC Recommended Soil Cleanup Objectives (RSCOs) and groundwater quality standards, specifically associated with volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs). The most elevated VOC and SVOC compounds detected include benzene, toluene, ethylbenzene, and xylenes (BTEX), and the polynuclear aromatic hydrocarbons or PAHs. The most significant contamination identified in soil and groundwater was confined to the northwestern portion of the Site (BCP area). Contamination was concluded to be associated with former upgradient MGP operations and a filling station. Concentrations of contaminants of concern in soil are as follow: Bezene (ND - 23 ppm), Toluene (ND - 9.6 ppm), Ethylbenzene (ND - 61 ppm), Xylene (0.14 - 160 ppm), Naphthalene (ND - 220 ppm), 2-Methylnaphthalene (ND - 57 ppm), Benzo(a)anthracene (ND - 7.4 ppm). NAPL was found at the site dispersed in the saturated zone between 5 to 10 feet bgs. Dissolved phase VOC contamination in groundwater ranges from 1.9 ppm to 16 ppm. Dissolved phase naphthalene in groundwater ranges from .28 to 2.5 ppm. MGP related contaminants were also found up gradient of the Site, and under the PS 156 school building. The concentrations of contaminants in soil are: naphthalene (120 ppm), ethylbenzene (7 ppm), xylene (4 ppm) and benzene (<1 ppm.) Since PS 156 is built on concrete stilts 30 feet above the ground, vapor intrusion is not a concern. Groundwater quality at the down gradient property line at the east and south of the property is generally non-detected for VOCs and SVOCs. The groundwater sampled from two wells near the southern border of the property contain very low concentration of Tetrachloroethene (9 ppb), vinyl chloride (9 ppb) and cis-1,2-Dichloroethene (13 ppb.) There may be an off-site source for these contaminanats. High level of BTEX compounds in groundwater has been identified to the west of the Site. This up gradient BTEX plume will be addressed by DEC under the Petroleum Remediaiton Program. High level of naphthalene and other VOCs was aslo found off-site in subsurface soil, north of the BTEX plume. The evidence suggest that residual MGP-related contaminants may be present just north of the Site and additional off-site investigation may be warranted. The Volunteer, New York City School Construction Authority has proposed a remedial action plan (RAP) to clean up the contamination found on the Site, and to solidify the MGP waste under PS 156. The
RAP was approved in July 2006. Intrusive work like drilling for jet-grouting of the hydraulic barrier wall created a few air particulates exceedances picked up by the Community Air Monitoring Program (CAMP) stations. In all cases, the mitigation procedures in the approved RAP was followed. Excavation was completed in October 2007. Final Engineering Report submittal and a Final Site Management Plan submittal is expected in December 2007. Off-site investigation of the BTEX plume source has begun using the Spills Fund on 173 East 156th Street property. A probable source of abandoned USTs has been identified and the potential responsible party has taken over the investigation at 180 E 156th Street. Off-site investigation of the MGP investigation has been initiated by Central Office.
Site Health Assessment
Soil and groundwater are contaminated at this site with volatile organic compounds. The proposed future use of the site will be four schools in one building. The proposed plan calls for the site to be covered by the building, a soil cap and pavement, and all grass areas will have a minimum of a two foot clean soil cap, which will prevent direct contact to residually contaminated soil. Also, engineering controls, such as a vapor membrane barrier and a sub-slab depressurization system, will be implemented during building construction as a preventative measure to minimize the potential for exposures associated with soil vapor intrusion.
2. The assurance that protective capping will take place on the open-space areas should be incorporated into the Remedial Action Work Plan.
3. The SCA and regulatory agencies should establish a robust, transparent, long-term Site Management Plan (for the life of the on- and off-site contamination), with an established process for addressing emerging exposures. The plan should include procedures for maintaining engineering controls, including vapor mitigation systems and protective caps (under the existing schools as well as on the new campus); institutional controls prohibiting soil disturbance; and long-term sampling protocols. In particular, groundwater monitoring adjacent to the hydraulic barriers should be extended until upgradient sources of contamination are eliminated. Contingency plans should be in place for addressing Technical, Logistical, and Regulatory contingencies, and there should be a schedule for periodic review of the protectiveness of the remedy.
4. New soil-gas sampling should be conducted subsequent to excavation to determine whether volatile compounds remain in the groundwater. If sampling detects VOCs above screening levels, then the SCA should undertake additional source remediation and commit to regular indoor air monitoring.
5. Enforceable timetables should be established for the remediation of all off-site contamination sources impacting the Mott Haven campus and adjacent, existing schools. The SCA should commit to secure a timetable for this work in writing from the DEC, and to taking actions to enforce its deadlines.
6. The SCA and Department of Education should evaluate installing heating, ventilation and air conditioning systems at P.S. 156 and I.S. 151
7. The dirt beneath the existing schools' platform should be capped with asphalt.
8. In situ solidification beneath P.S. 156, as well as any other remediation activity beneath the existing schools, should not take place when children and school employees are in the buildings.
9. Additional testing in and around P.S. 156 and I.S. 151 should be conducted to determine conclusively the source of PCE in the indoor air.
10. Elevator shafts should be carefully sealed so as to avoid acting as pumps for vapor intrusion.
11. New York City should establish a standard process for involving the affected public in the environmental review of school sites before preferred alternatives are selected. Furthermore, cleanup of school sites should be based on applicable standards that are no less stringent than those allowed for a restricted use/residential scenario.