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Ms. Amy Terrell <br /> Page 2 <br /> October 28,2004 <br /> Disking of soil west of the warehouse and subsequent addition of a nitrogen-deficient <br /> carbon source to the soil has been suggested by the RWQCB as a means of facilitating <br /> volatilization and nitrification of ammonium and subsequent denitrification of the nitrate. <br /> Because asphalt currently covers the area between the warehouse and the railroad spur, <br /> asphalt would have to be removed before the soil could be disked and amended.As stated <br /> in the previous paragraph,invasive work such as asphalt removal would not be feasible <br /> while the railroad lines west of the warehouse remain active. Further,routine disking that <br /> would be necessary to promote volatilization and treatment of ammonium would be <br /> difficult to implement given the current uses of the site. <br /> Several other concerns relate to in situ treatment of ammonium in the soil. Ammonium is <br /> relatively immobile in the soil and is retained by the soil cation exchange capacity. <br /> Treatment processes that result in nitrification of ammonium to nitrate without immediate <br /> denitrification or plant uptake of the nitrate will result in leaching and increased <br /> concentrations of nitrate in the groundwater. In addition,although in situ denitrification has <br /> been tested at the site,in situ nitrification has not been evaluated.Finally,because of the <br /> difficulty of mixing and amending soil deeper than 2 feet,in situ treatment involving <br /> disking would not be effective for subsurface soil. <br /> Based on the information presented in the preceding paragraphs,it is recommended that no <br /> action be taken at this time to address ammonium in soil west of the warehouse. <br /> Ammonium is tightly bound to the soil matrix and does not leach to groundwater at <br /> significant concentrations,as indicated by ammonia concentrations detected in groundwater <br /> since 1996.Ammonium that does leach from the soil matrix or is converted to nitrate over <br /> time will be removed from groundwater downgradient of the warehouse through <br /> phytoremediation.The ammonium and nitrate will be remediated by the poplar,paulownia, <br /> mulberry,sycamore,black locust,and willow trees located in original test grove, <br /> turnaround area,former bagging plant,and stormwater pond planting locations at the site. <br /> The need for remedial action to address ammonium in soil west of the warehouse will be re- <br /> evaluated in the future should activities at the warehouse and railway change or cease for a <br /> period of time that would allow a remedial action to be performed.The RWQCB will be <br /> notified if and when uses of the site change that would allow a remedial action to take place <br /> west of the warehouse. <br /> Draft Monitoring and Reporting Program <br /> The draft MRP submitted with the September 27,2004,letter indicates that any wells <br /> installed subsequent to the issuance of the MRP will be monitored quarterly for at least one <br /> year prior to following the monitoring schedule identified for the other site monitoring <br /> wells. However,the extent of groundwater contamination and seasonal trends in analyte <br /> concentrations have largely been determined by analytical data collected during the past <br /> eight years of monitoring at the site. Koppel PRPs feel that quarterly monitoring of new <br />