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GEOSYNTEC CONSULTANTS <br /> Mr. Robert S. Fagemess <br /> 14 August 2000 <br /> Page 2 <br /> The Permit prohibits discharge to the canal when both the electrical conductivity <br /> (EC) of the receiving water upstream of the WFS outfall and the EC of the discharged <br /> groundwater exceeds 700 µmhos/cm. Discharge to the canal is also prohibited when the <br /> sum of the receiving water EC and the discharged groundwater EC is greater than <br /> 700 µmhos/cm as measured approximately 245 ft downstream of the discharge location <br /> into the canal. Furthermore, discharge to the canal up to 60 gallons per minute (gpm) is <br /> also prohibited when the flow in the canal is less than 20 cubic feet per second(cfs). <br /> The 1999 irrigation season began in mid-March and Lateral 4 North began carrying <br /> irrigation water at full capacity. To check whether discharge of groundwater from WFS <br /> would be limited due to EC conditions, GeoSyntec began gathering EC measurements <br /> from the canal. <br /> On 4 May 1999, the EC in Lateral 4 North was measured at 500 µmhos/cm, which <br /> is below the 700 µmhos/cm limit set forth in the Order. By 9 June 1999, the EC <br /> increased to 900 µmhos/cm and did not fall back below 700 µmhos/cm for the <br /> remainder of the irrigation season that ended on 2 November 1999. The EC monitoring <br /> program indicated that there might be a 2-month window, from mid-March to mid-May, <br /> when the EC conditions in Lateral 4 North were sufficiently low (below 700 gmhos/cm) <br /> so that groundwater from the WFS Vernalis site could be discharged. <br /> The frequency of EC measurements between March and May 1999 was not <br /> sufficient to confirm that the EC in Lateral 4 North remained below 700µmhos/cm <br /> throughout the entire 2 months. As an alternative to discharging to the canal, <br /> GeoSyntec redesigned the groundwater extraction system to include carbon treatment <br /> followed by discharge to an on-site storage tank where the water could be used for <br /> liquid fertilizer production. Construction of the modified system was completed in <br /> December 1999. <br /> Discharging to the canal is preferred over discharging to a storage tank because it <br /> allows for continuous pumping. To more accurately evaluate whether the EC <br /> conditions in Lateral 4 North during the first two months of an irrigation season are <br /> sufficiently low to allow discharge to the irrigation canal, EC was measured twice daily <br /> !:\WFS\SHELL\VER\NPDESIIuly 2000 Inspection Rpt..doc <br /> r <br /> `, RECYCLED AND RECYCLABLE <br />