In 2003, DOE implemented the first phase of an interim action system at the site to address concerns regarding elevated ammonia levels in ground water while it evaluates long-term solutions to site contamination. Referred to as Configuration 1, the first phase consisted of 10 closely spaced extraction wells designed to remove ammonia from ground water before it discharges to critical habitat areas of the Colorado River. Configuration 1 extraction wells and a lined evaporation pond became fully operational in September 2003. Since then, ground water has been extracted from the shallow aquifer and pumped via pipeline to the evaporation pond. The evaporation pond covers approximately 4 acres and was constructed outside the 100-year floodplain, on top of the tailings pile.

Well PW02, which was installed in November 2000 as a monitoring well as part of the site characterization effort, is located about 2,000 feet northwest of Configuration 1 off the base of the tailings pile. This well was added to the ground water extraction system in April 2005 to increase the volume of water and contaminant mass removal.

Configuration 2 of the interim action was completed in 2004 with the addition of a series of 10 dual-purpose extraction and fresh water injection wells to the north of Configuration 1. This year, Configuration 2 has not been operating due to a loss in well efficiency. The project is evaluating options to improve its effectiveness.

Installation of Configuration 3 of the interim action was completed in August 2005 and consists of another series of 10 dual-purpose extraction and fresh water injection wells to the north of Configuration 2 along the river bank. Configuration 4, which is located to the south of Configuration 1 and consists of 10 dual-purpose wells, became operational mid-September 2006. As of October 29, 2009, more than 151 million gallons of ground water had been extracted through the interim action system.

Configuration 1 wells were restarted near the end of January 2009. PW02 was restarted for 2009 on March 12 and Configuration 3 wells were restarted on March 23. The well field reached a combined extraction rate of 100 gallons per minute (gpm) during the last week of March. The rate was intentionally reduced this summer when the high Colorado River stage created a natural hydraulic barrier to contaminant discharge to the river. The well field extraction rate is currently about 30 gpm. 

A land-applied spray evaporation system was installed in spring 2004 to enhance evaporation of water pumped from the interim action evaporation pond by using a sprinkler system installed on top and along the sides of the Moab tailings pile. The sprinkler system consists of micro-spray nozzles on 25-foot centers and operates in conjunction with the existing evaporation pond to maximize the evaporative capacity of the interim action system. The system is designed to evaporate the water before it infiltrates the tailings pile and to provide dust suppression. The sprinkler system was restarted for 2009 on February 26. As tailings are excavated from the pile and conditioned in preparation for shipment, the area covered by the spray evaporation system has been reduced. The project is investigating ways to maximize the existing sprinklers as the spray evaporation system is further reduced. Evaporation enhancement equipment has been placed on the pile to help evaporate water from the pond.

DOE continues to evaluate the effectiveness of the interim action system, which will likely become part of the final ground water remedy. See Ground Water Interim Remedial Action for project documents associated with the interim action.