Table 1.

Estimated frequency of some potential contamination mechanisms from hydraulic fracturing jobs or wells

Potential contamination mechanism	Approximate frequency (1)
Spills	2.6% (0.4–12.2%) of wells
“Frac hit” of nearby well	1% (0.4–4%) of wells
Well integrity failure	0.5% (0.1–2%) of jobs

See also SI Appendix, Table S22.