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C Oil Exploration and Production Wastes Initiative Discussion of Results - Four E&P wastestreams were sampled during the course of this initiative: produced water; drilling waste; oily sludges; and foam treatment waste. Due to the limited volume of foam waste available at the time of sampling, data pertaining to this wastestream was generated based on analysis of only two samples. Foam treatment data are discussed in this section, but a formal conclusion will not be drawn regarding the waste's characteristics based on limited data. As previously stated in this report, the primary objective of this initiative was to examine and characterize the E&P wastes, and determine if they are properly managed in California. As such, each wastestream sampled is evaluated independent of the others to enable DTSC to draw general assumptions of each wastestream. All data points obtained for a particular wastestream are pooled together regardless of the sampling site to form a sample population representative of that wastestream. This approach is appropriate when considering the scope of this initiative, which was not to compare and contrast individual facility data, but to characterize and obtain information for the wastestream as a whole. The sample population was noted to have a large variation, which generated a standard deviation value that is greater than the mean. Factors contributing to the large variation are regional differences in formations, and diversity of waste management practices among oil producers. Geological characteristics of each region will have specific, naturally occurring variations. To a large extent, a wast tream's composition will also be affected by the type of operation and waste management practices of the generator. For example, the benzene concentration in produced water samples varies from ND to 2,100 ug/I. It was noted that produced water samples that were collected from pipelines to the agricultural canal displayed the lowest benzene concentration, with values ranging from below detection limits to 0.6 ug/I. SCD attributes this finding to the purification processes that produced water is put through (e.g., water treatment plants), prior to disposal into the canal to meet standards imposed by RWQCB permits under which the water is disposed. Thus, the extent of treatment of the waste prior to disposal is a determining factor in the concentration of the contaminants. Because waste management practices vary with each facility, the contaminant levels in the waste will vary also. For some tests (e.g., SVOCs), a large variation occurred because the majority of samples analyzed displayed ND values, with few samples displaying values above detection limits. As a result of this variation, the calculated mean value was lower than the standard deviation. Statewide Compliance Division May 2002 -35-