Evaluation and Impact of Waste Water Handling Practices
At a Trona Processing Plant

Situation
Waste water handling practices at a trona processing plant had created a brine plume in a fractured bedrock aquifer that discharged into a nearby river. Saturated sodium carbonate brines were seeping from several unlined evaporation and holding ponds into the aquifer and moving toward the river. The effectiveness of an existing underdrain system required testing. Hydro Geo Chem, Inc. was retained to:

• Predict and evaluate the long-term effects on brine movement and surface water quality,
• Evaluate the existing underdrain system, and
• Develop an effective underdrain operation program.

Hydro Geo Chem’s Approach
Stable isotopes of hydrogen and oxygen were used to distinguish brine water from native, highly saline groundwater. Hydrogeologic and geochemical data were used to construct and calibrate groundwater flow and solute transport models in order to predict contaminant migration rates to the nearby river. The model was then used to develop effective water management strategies.

Results
The underdrain operation program, developed by Hydro Geo Chem is ongoing as are evaluations of the long-term effects on brine movement and surface water quality. Our fate and transport analyses eliminated the need for retrofitting liners in the pond, providing an estimated savings in excess of $1 million.