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The MPCA updated two Petroleum Remediation Program (PRP) guidance documents: Soil and groundwater assessments performed during site investigations (c-prp4-01) and Vapor intrusion assessments performed during site investigations (c-prp4-01a).
In order to better understand and determine plume stability, Soil and groundwater assessments performed during site investigations (c-prp4-01) was updated to include using multiple lines of evidence to evaluate plume stability. All changes can be found in item 4 of Section B Remedial Investigations.
Vapor intrusion assessments performed during site investigations (c-prp4-01a) was updated to incorporate best management practices already required by other MPCA guidance documents. The following items are now included in the guidance document:
The only new addition to Vapor intrusion assessments performed during site investigations is a requirement that all soil gas samples collected during the initial soil gas assessment be analyzed for fixed gases. Fixed gases can be analyzed using the same canister as the volatile organic compound samples, so field staff do not need to change their current sampling procedures. Methane can be a product of petroleum degradation and is one of the drivers for reopening of sites evaluated during the MCPA’s vapor intrusion look back project. By requiring the fixed gas analysis at the onset of an investigation, we will be able to identify potential issues during the site investigation phase.
These changes are effective for all site work going forward.
If you have any questions, please contact Caroline McFadden at caroline.mcfadden@state.mn.us or 651-757-2075.
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