A scientific report from the Forest Department establishes that flowback fluid stored in large tanks gives different results depending on how deep in the tank samples are taken. At the deepest level, the solution has the greatest toxicity. While this may seem funny at first, it has serious implications in regards to regulation. If samples are taken from the top of a tank, the possibility to easily circumvent regulation does exist.
A natural gas well in West Virginia was hydraulically fractured and the ﬂowback was
recovered and stored in an 18-foot-deep tank. Both in situ ﬁeld test kit and laboratory
measurements of electrical conductivity and chloride concentrations increased substantially
with depth, although the laboratory measurements showed a greater increase. The ﬁeld
test kit also underestimated chloride concentrations in prepared standards when they
exceeded 8,000 mg L-1, indicating that laboratory analyses or other more accurate methods
of detection should be used to determine chloride concentrations in ﬂowback when they may
be approaching West Virginia regulatory levels (12,500 mg L-1) that disallow disposal by land
application. The gradation of chloride with depth also has implications for procedures used
to collect ﬂ owback samples from reserve pits or tanks before disposal to ensure the resulting
composite chloride concentration is representative of the total volume.