Environmental Investigation by Con Edison

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Environmental Investigation by Con Edison

• Former E115th Street Gas Works

November 13, 2007
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Presentation Overview

• Former MGP Site History
• Investigation Activities and Results
• Next Steps

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(No Transcript)
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Former E.115th Street Gas Works (1895 1936)
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Former Gas Works Structures

• Coal Yard/Coal Bins
• Oil Tanks
• Generators
• Purifying Houses
• Gas Holders

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Manufactured Gas Plant (MGP) Substances of
Concern

• Coal tar
• Purifier waste
• Volatile organics benzene, toluene,
  ethylbenzene, xylene (BTEX)
• Semivolatile organics polycyclic aromatic
  hydrocarbons (PAHs)

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Site Investigation Activities

• Indoor air quality assessment conducted in July
  and December 2002
• Remedial Investigation performed in August and
  September 2003
• Remedial Investigation Report approved by the
  NYSDEC in August 2004
• Supplemental Remedial Investigation conducted in
  August 2004 (on-site) and January 2005 (Harlem
  River)
• Supplemental Remedial Investigation Report
  approved by NYSDEC in September 2005.

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July 2002 Indoor Air Quality Assessment

• Purpose assess potential MGP contamination
  beneath the school building and its potential
  impacts on indoor air quality
• Scope included
• --Indoor air samples from basement and first
  floor (13)
• --Soil gas samples from basement and near
  building (5)
• --Air samples outside of building (4)
• --Soil samples from basement and near
  building (4)
• --One groundwater sample near building

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July 2002 Indoor Air Quality Assessment Results

• All indoor air results were within typical
  background indoor air range no indication of MGP
  impacts
• Soil gas samples contained elevated VOC levels
• Soil and groundwater results indicated presence
  of subsurface impacts beneath and near school
  building

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December 2002 Indoor Air Quality Assessment

• Purpose evaluate indoor air quality under winter
  conditions
• Scope 13 indoor air samples from areas sampled
  in July 2002
• Results VOCs indicative of cleaning products,
  gasoline and paint detected in some samples at
  levels above background no discernable MGP
  impacts observed

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Remedial Investigation (August 2003- January
2005)

• Purpose delineate subsurface MGP impacts within
  the school property and off-site
• Scope included
• ---Indoor air quality assessment (August 2004)
• ---Soil and groundwater sampling inside and
  around the school building
• ---Sediment sampling in the Harlem River

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August 2004 Indoor Air Quality Assessment Results

• Indoor air quality generally within typical
  background range
• Low levels of VOCs indicative of cleaning
  products and gasoline present in some samples
• VOC levels consistent with previous sampling
  events no discernable MGP impacts observed.

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Remedial Investigation Results

• Some organic compounds and metals found in
  surface soil at slightly elevated levels,
  however, within typical background range
• MGP residuals (coal tar) found at depths of 6
  feet to 42 feet
• Elevated levels of MGP constituents detected in
  groundwater
• MGP impacted sediments found in Harlem River at
  depths 14 feet to 27 feet below sediment surface.

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Community Outreach

• Citizen Participation Plan
• Fact Sheets and Public Notices at every phase of
  investigation
• Update meetings were held with NYCDOE, school
  administration, UFT and faculty
• Public Meeting for Parents on March 30, 2004
• Internet Content at www.coned.com/publicissues
• Toll-Free Hotline [phone]

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Community Outreach
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Next Steps

• Conduct pilot testing of remedial alternatives
  under consideration.
• Finalize Remedial Alternatives Report (draft
  submitted to NYSDEC, DOE and Mayors office in
  January 2007)
• Prepare Remedial Action Work Plan for NYSDEC
  review and approval
• Implement approved remedy following public
  review and comment