SITE INFORMATION AND CORRESPONDENCE 1980-1999

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• i a 1-hour average and 0.01 mg/l (11 µg/1) as a 4-day average. Given the reasonable potential for exceeding a water quality standard,the Tentative Permit must also contain a mass limit for chlorine. C. A Defensible Reasonable Potential Analysis And Mass Limit For Electrical Conductivity Must Be Included In The Permit. EPA regulations at 40 CFR § 122.44(d)(1) establishes the basis for determining if there is an excursion of a numeric or narrative water criteria. The permit writer should use the maximum observed effluent concentration, or a statistically projected worst-case value,to calculate a projected in-stream concentration,under critical stream conditions. The Information Sheet discloses that only data collected between January 1998 through September 1999 was used to evaluate electrical conductivity. The Discharger's data demonstrates that, over the last two years, the EC of the effluent ranged from 550 to 700µmhos/cm. This time frame was during a relatively wet period and is clearly inadequate to evaluate potential impacts during critical conditions (i.e. droughts). The Information Sheet states that the Basin Plan objective for EC in the San Joaquin River at Jersey Point strives for an EC of between 740 and 2,200 µmhos/cm depending on flow conditions. However,Jersey Point is across the Delta close to the confluence of the San Joaquin with the Sacramento River. It is an area of high salinity. We believe that it inappropriate to use salinity at Jersey Point to evaluate impacts to the back sloughs in the vicinity of the Discharger's outfall. Recent data provided to the San Joaquin River Dissolved Oxygen TMDL demonstrates that substantial Sacramento River water is drawn thru the Cross Delta Channel into the Stockton Deep- Water Channel and San Joaquin River upstream of Stockton (personal communication, Chris Foe). In other words, total dissolved solids discharged into the White Slough are drawn to those areas of the Delta identified as impaired because of EC. There is little dilution in Dredger Cut and at least five agricultural intakes are in the immediate vicinity of the outfall. Limits must be included in the permit that are protective of nearby agricultural intakes. Since the Delta is impaired because of EC, mass limits for dissolved solids must be included in any permit issued. DeltaKeeper notes that Finding 5 in the Tentative Permit states that the Discharger's self monitoring reports indicate that total dissolved solids in waste water applied to fields ranged from 430 mg/1 to 1658 mg/1 and that the specific conductance ranged from 620µmhos/cm to 1694 µmhos/cm. Reclamation Specification D-11 states that"[s]tormwater runoff from the irrigation field shall not be discharged to any surface water drainage course within 30 days of the last application of reclaimed water. Salt leached during rain events may be discharged(or migrate through groundwater)into Dredger Cut in concentrations that exceed water quality standards. DeltaKeeper,Tentative NPDES Permit,Lodi, 17 December 1999,Page 4.