6. Site management – Step 7 (when warranted)

With the rapid aerobic degradation, most structures will screen out and site management other than possible land use controls are typically not needed. As discussed in Sections 4 and 5, unacceptable risks associated with petroleum are typically limited to:

• NAPL that is within the separation distances described in Sections 4 and 5,
• NAPL or a dissolved source of petroleum-contaminated groundwater above the applicable VIAC entering a structure, or
• A direct pathway for vapors to migrate into a structure, such as an underground conduit line (see Attachment C.4, Section 3.2).

When warranted, most strategies and approaches are dependent upon site-specific factors and cannot universally be applied across the entire property. 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 will remain. Furthermore, the need for land or resource use restriction will be highly dependent on site conditions, if a vapor source remains, and how and where representative soil gas samples are collected in relation to the vapor source.

For petroleum, Attachment D.4 can be used as a guide for the evaluation and when land or resource restrictions or an alternate evaluation will be necessary. Detailed management strategies including the use of either a land and 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 the VIAP regardless of if the vapor source only contains petroleum and describes additional approaches that may be appropriate for only petroleum.