California Air Resources Board

To assist CARB in assessing air impacts of well stimulation treatment operations in California, CalGEM requires operators to conduct air sampling during select operations. Third-party experts have analyzed the data collected so far to determine statistically significant differences between the measured data and potential implications for human health. Complete results are detailed in two companion reports posted below, with a result summary posted here.

The purpose of these analyses was to evaluate pollutant concentrations measured during well stimulation treatment events.

“Comparative Analysis of Air Monitoring Data Collected During Oil Field Well Stimulation Treatments,” Stringfellow & Associates, June 2020

The goal of the first study was to determine statistically significant differences in pollutant concentrations between hydraulic fracturing, cleanout activities, and nearby background concentrations.

• Report: Comparative Analysis of Air Monitoring Data Collected During Oil Field Well Stimulation Treatments
• Appendix A: List of Analytes Not Detected in Any Well Stimulation Event
• Appendix B: Tier 1 Comparisons Between Well Stimulation Activity
• Appendix C: Tier 2 Comparisons Between Well Stimulation Activity
• Appendix D: Tier 3 Comparisons Between Well Stimulation Activity
• Appendix E: Tier 4 Comparisons Between Well Stimulation Activity
• Appendix F: Comparison of Analytical Results Between Laboratories
• Appendix G: Tier 1 Comparisons Between Ambient, Background, Upwind and Downwind
• Appendix H: Tier 2 Comparisons Between Ambient, Background, Upwind and Downwind
• Appendix I: Tier 3 Comparisons Between Ambient, Background, Upwind and Downwind
• Appendix J: Tier 4 Comparisons Between Ambient, Background, Upwind and Downwind

“Analysis of Air Monitoring Data Collected During Oil Field Well Stimulation Treatments in California: Implications for Human Health,” PSE Healthy Energy, July 2020 [Updated 3/25/2021]

The goal of the second study was to determine the potential implications for human health associated with air pollutants identified during hydraulic fracturing and cleanout activities.

• Report: Analysis of Air Monitoring Data Collected During Oil Field Well Stimulation Treatments in California: Implications for Human Health
• Appendix A: CARB Air Sampling and Analysis Plan for Well Stimulation Treatment Operations
• Appendix B: Supplementary Tables for the Report

For questions regarding these Companion Reports contact Ms. Kathleen Kozawa, Manager, Program Assessment Section.