A number of changes related to vapor intrusion are in various stages of development and implementation. The NJDEP Vapor Intrusion Guidance document is currently undergoing major revisions. It is the Department’s intent to issue a revised document by the end of 2009.
One change that is being implemented now deals with the investigative approach to vapor intrusion. Specifically, sub-slab soil gas and indoor air samples shall be collected concurrently for all buildings having sensitive populations. The Department considers sensitive uses to include, but not limited to, child care centers, schools, and residential properties.
As currently written, the Vapor Intrusion Guidance recommends that exceedances of the Ground Water Screening Levels triggering the collection of sub-slab soil gas samples. Then, if the Soil Gas Screening Levels are exceeded, indoor air samples shall be collected. The new change in policy will require the collection of both sub-slab soil gas and indoor air upon the initial trigger (usually an exceedance of a Ground Water Screening Level) of a vapor intrusion investigation.
To avoid the potential for cross-contamination between the soil gas and indoor air, the indoor air sample shall be collected first at the structure undergoing investigation. Once the indoor air sampling is completed, the investigator shall immediately collect the sub-slab soil gas sample. Using the typical 24-hour sampling timeframe, the indoor air sample shall be sampled on Day 1. Twenty four (24) hours later (Day 2), the indoor air sample canister is closed and the investigator shall drill the sample port and collect the sub-slab soil gas sample.
This policy change should be implemented immediately.
|
