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Volume 4: Investigative approach for petroleum VIAP

Attachment D - Site management for petroleum

Most strategies and approaches for site management of PVI are dependent upon site-specific factors and cannot universally be applied across the entire facility. In several areas of the state, especially where groundwater is less than 10-feet below grade, the approach is very different than those where deeper vapor sources remain. Furthermore, the need for land or resource use restrictions will be highly dependent on-site conditions, if a vapor source remains, how and where the soil gas samples are collected, especially in relation to the vapor source, and if future land uses can be evaluated with appropriately collected soil gas samples.

For petroleum, Table D-1 can be used as a general guide for the evaluation of when land or resource use restrictions or controls, or an alternate evaluation, will be necessary. Detailed management strategies, including the use of either a land or resource use restriction, when they may or may not be appropriate, response activity, and more is further described in Volume 5 – Response Activity. Many of the site management activities are applicable to VIAP regardless of the hazardous substance released, however, Volume 5 – Response Activity also describes additional approaches that may be appropriate for only petroleum.

Table D-1 Vapor Source, Depth, and Common Site Management for Closure

Scenario – Assuming Vapor Source Not in Contact Data Required Outcome Actions for Closure of the VIAP for petroleum releases
Vapor Source of NAPL less than 10 feet below ground
  • Soil gas samples from sub-slab or at least 5 feet below ground (assuming the NAPL is not shallower than 5-feet below ground)
  • Soil gas sampling with the appropriate number and rounds of data is below applicable VIAC
  • ICs required to ensure that land use changes don’t result in exposure scenario that has not been evaluated (e.g., restrict construction to slab on grade)
Vapor Source of NAPL is 10 feet or greater
  • Data that supports a clean, biologically active soil between the NAPL and structure
  • Soil gas samples from a depth greater than 8 feet below ground
  • For all reasonable land uses, vapor source not in contact will be maintained
  • Soil gas sampling with the appropriate number and rounds of data is below applicable VIAC
  • No ICs required for PVI
  • Notice or other ICs maybe required for NAPL or other pathways
Vapor Source of NAPL is 25-feet or greater below ground surface and above the water table
  • Data that supports a clean, biologically active soil between the NAPL and structure
  • 15-foot vertical separation will be maintained
  • No ICs required for PVI
  • Notice or other ICs maybe required for NAPL or other pathways
Vapor Source of groundwater above applicable unrestricted residential VIAC is less than 8 feet below ground
  • Data that supports a clean, biologically active soil between the groundwater vapor source and the structure
  • Groundwater data and soil gas samples from sub-slab or at least 5 feet below ground (assuming no vapor source is shallower than 5-feet below ground)
  • Vertical separation screening distance of 5 feet or
  • Soil gas sampling with the appropriate number and rounds of data is below all applicable VIAC
  • ICs required to ensure that land use changes don’t result in different exposure scenario that has not been evaluated (e.g., groundwater in contact)
Vapor Source of groundwater above applicable unrestricted residential VIAC is 10 feet or greater below ground
  • Data that supports a clean, biologically active soil between the groundwater vapor source and the structure
  • Soil gas samples from a depth of at least 8 feet below ground
  • Soil gas sampling with the appropriate number and rounds of data is below all screening levels
  • No ICs required for PVI
  • Notice or other ICs maybe required for other pathways
Vapor source of groundwater above applicable unrestricted residential VIAC is 15 feet or greater
  • Groundwater data
  • Data that supports a clean, biologically active soil between the groundwater vapor source and the structure
  • 5-foot vertical separation will be maintained
  • No ICs required for PVI
  • Notice or other ICs maybe required for other pathways
NOTE: MLE evaluation, per NAPL guidance, that supports the presence or absence of NAPL is warranted for each scenario and a determination if an IC is required.
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