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002625 . . concentration has been due to influent quality and quantity fluctuations. As part of the oplimization efforts, an equalization tank has been installed in order 10 have more consistent flow and concentration to the FBR system. Since the operation of the new Kerr-McGee FBR system began, the perchlorate load to Las Vegas Wash continues to drop. According to Nevada Department of Environmental Protection, the perchlorate load to Las Vegas Wash prior to remediation was approximately 1,000 pounds per day. (1999). It was reduced to approximately 500 pounds per day after first remedial facilities were constructed and since operation of the FBR system the load has further dropped and is in the range of 120 to 130 pounds per day, as of September 2004. The perchlorate removal rate is approximately 1,810 pounds per day at this time. As of September 2004, approximately 1,370 tons of perchlorate has been removed from the environment. 'The perchlorate concentration at the Willow Beach monitoring station has dropped to about 2 ppb as of September 2004. However, we may see higher concentrations later this year due to Lake Mead's turnover; but the concentration is not predicted to be higher than 6 ppb. You may recall that in January of this year the State Office of Environmental Heal1h Hazard Assessment (OEHHA) set the perchlorate Public Health Goal (PHG) al6 ppb. The AMPAC plume is a deep plume and has not yet contributed to the contamination of Las Vegas Wash, until recently. The proposed remediation system for this deep plume is still in the design process. According to Nevada Department of Environmental Protection, the design process will be completed by the end of November 2004, and the first treatment system for the leading edge of the AMP AC plume will be operational by spring 2005. Topock Gas Compressor Station Hexavalent Chromium-6 Contamination Site Status The Arizona Department of Environmental Quality (ADEQ) in a letter dated September 9, 2004 to the California Regional Water Quality Control Board (RWQCB), has made comments on three orders issued by the RWQCB and specifically on the issuance of the Notice of Exemplion (NO E) to CEQA. A summary of the ADEQ concerns include the following: o Chromium 6 has been detected in water supply wells located in Arizona on the east side of the Colorado River and the chromium 6 plume may have reached Arizona. The chromium 6 plume has not yet been delineated on the east side of the Colorado River. o The remediation activities have been conducted without the knowledge of the ADEQ, al1hough public outreach efforts have been conducted by the PG&E in Arizona. 9