A radiological characterization of remediated tank battery sites

Tank battery sites have historically been used for the initial processing of crude oil which separates water and sediment from the produced oil. Typically, one or more producing wells is connected to a tank battery site consisting of storage and separation tanks. Historical operating practices also included a production holding pit for increased separation of oil, water, and sediment. The sediment remaining in the pit is composed of an oily, viscous material called sludge. Under certain circumstances, this sludge may contain naturally occurring radioactive material. The methodology required for reclamation of the production holding pits consisted of removal of soil and sludge from the pits with controlled land-spreading to achieve biodegradation of the hydrocarbons. The purpose of this study was to perform a radiological characterization on representative tank battery sites that had been reclaimed in the above fashion. The average gamma radiation exposure rates encountered ranged from 2.1-7.2 pC kg-1 s-1. The average concentration of 226Ra for the tank battery sites ranged from 0.5-2.3, 0.5-2.8, and 0.3-3.2 Bq g-1 for soil depths of 0-15, 15-30, and 30-51 cm, respectively. Average radon flux measurements ranged from 29.7-211.8 mBq m-2 s-1. Measurements of the radon emanation coefficient of NORM ranged from 3-7%.