SITE INFORMATION AND CORRESPONDENCE_1993-2003

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WASTE DISCHARGE REQUIREMENTS ORDER NO.RS-2002-0213 • 10 U.S.DEPARTMENT OF DEFENSE DEFENSE LOGISTICS AGENCY DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN SHARPE GROUNDWATER REMEDIATION SYSTEM SAN JOAQUIN COUNTY 19. Approximately two years of the most recent effluent monitoring data were compiled for each of the three GWTPs, and these data are summarized in Attachment C, a part of this Order. Data for most pollutants was not of sufficient quality for comparison with adjusted water quality criteria. A Provision in this Order requires the Discharger to collect additional effluent and receiving water data for pollutants of sufficient quality for comparison with appropriate criteria. This Order may be may be re-opened if the data indicate concentrations of pollutants are or may be discharged at a level which will cause or have the reasonable potential to cause or contribute to an in-stream excursion above the appropriate criteria. 20. Previous Order No. 95-258 included daily maximum and monthly median effluent limitations for total petroleum hydrocarbons (TPH) (100 µg/L (ppb) and < 50µg/L (ppb), respectively) consistent with General Order 92-150,which regulated discharges of petroleum contaminated groundwater to surface waters. On 16 June 2000, General Order 92-150 was rescinded, and renewed General Order No. 5-00-119 was adopted. Renewed General Order No. 5-00-119 retained the effluent limitations for TPH of the previous Order(monthly median changed to 30- day median)based upon a combination of technology and water quality criteria. The 30-day median lim4ation of<50 µg/L (ppb)was established based upon commonly available treatment and analytical technology. The daily maximum effluent limitation of 100 µg/L(ppb)was established based upon taste and odor water quality criteria. These criteria still apply to the discharge, and TPH constituents have been detected in influent groundwater,prior to treatment, at concentrations up to 340 µg/L(ppb). Therefore, the daily maximum and monthly median effluent limitations for TPH have been retained and included in this Order. 21. Previous Order No. 95-258 included a monthly median effluent limitation for arsenic of 40 µg/L (ppb) and a daily maximum effluent limitation of 50 µg/L (ppb) to avoid potential health impacts from discharge to an empty canal. The Basin Plan states that waters shall not contain chemical constituents in concentrations that adversely affect beneficial uses. At a minimum,water designated for use as domestic and/or municipal supply shall not contain concentrations of chemical constituents in excess of maximum contaminant levels (MCLS). The new USEPA primary MCL for arsenic is 10 µg/L(ppb). The compliance date for water purveyors to meet the new MCL is 23 January 2006. Federal regulations at 40 CFR Section 122.44(d)(1)(vi)(A) allow the state to establish effluent limitations using an explicit state policy interpreting its narrative objectives. Use of the USEPA Primary MCL is appropriate to implement the narrative chemical constituent objective. As shown in Attachment C,results of effluent monitoring of the three GWTPs indicates concentrations of arsenic in the final effluent range from 13 µg/L (ppb) to a maximum recorded value of 21 gg/L (ppb) (North Balloon GWTP). As noted previously,the SSJID Canal, absent the discharge, is at times a seasonal and/or ephemeral waterbody. The effluent flow from the DDJC-Sharpe outfall to the SKID Canal may represent,at times,most of or all of the flow in the SSJID Canal. Considering these flow conditions and the results of effluent monitoring, the SSJID Canal at times likely contains concentrations of arsenic that exceed the new USEPA primary MCL of 10 gg/L(ppb), potentially impacting the municipal and domestic supply beneficial uses of the SSJID Canal and oten g P P Y P