WWRC 90-05
Assessment of Potential Environmental Impacts of Saline Oil-Field Discharges into Salt Creek and the Powder River, Wyoming
Abstract
Environmental and regulatory concerns are increasing over the
possible effects of discharging co-produced waters from oil fields to
natural receiving waters. These discharges, known as oil-field brines,
are typically high in total dissolved solids and have a variety of
organic and inorganic constituents. Relatively little is known about the
toxicity and persistence of these discharges in the receiving waters.
This study was undertaken to assess the effects of oil-field brines on
water quality in Salt Creek and downstream in the Powder River of
Wyoming. Methods included (1) laboratory toxicity tests of ambient
stream waters with fathead minnows and Ceriodaphnia dubia, (2) chemical
characterization of the salt load and organic compounds introduced along
the stream gradient, (3) preliminary assessment of the contributions of
salt, organic compounds and other constituents to toxicity, and (4) a
qualitative stream fauna survey.
Oil-field brines discharged from the upper Salt Creek oil field have
toxic effects on surface waters in Salt Creek and the Powder River,
especially during low flow. Toxicity could not be attributed to organic
compounds or trace elements, as measured in this study. Salinity,
alkalinity and pH correlated well with observed toxicity, but could not
be singled out individually because of a high degree of covariance.
Suitable habitat for macroinvertebrates was scarce at most sample sites,
and the qualitative survey of stream fauna was of minimal use in
detecting effects from oil field discharge waters.
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