SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Mr.Robert Mihalovic • - 2 - • 27 September 2004 Soil Source Areas In 1997 and 1998, the site assessment soil sampling showed high concentrations of ammonium in shallow soil along the west side of the warehouse adjacent to the railroad spur. Seven of the eight samples obtained along this west side contained ammonium ranging from about 2,000 mg/kg to 7,000 mg/kg as illustrated in Figure 3-3 of the February 2000 Feasibility Study Report prepared by CH2MHill. In our 6 March 2000 letter, Central Valley Regional Water Quality Control Board (Regional Board) staff stated that this area would need to be addressed in the future, and in an 8 May 2001 telephone discussion,Mr. Gerald Vogt of CH2MHill suggested that the three-year evaluation would be an appropriate time to revisit remediation of this area. At this three-year juncture, Koppel needs to propose and implement a remediation strategy for this land between the railroad spur and the warehouse. In spite of the dramatic reductions of nitrate concentration attributable to the phytoremediation, this remediation process is not likely to bring the nitrate levels down to cleanup goals as long as there is a reservoir of ammonium in soil available to convert to nitrate and move through the soil profile to groundwater. Please provide a schedule to deliver a cleanup plan addressing this area by 29 October 2004. Off-site Nitrogen Directly to the north of the Koppel site, the former Cal Farm Supply facility is also undergoing assessment and remediation for nitrate in groundwater. In 1997, Cal Farm Supply installed MW-6 between Cal Farm Supply and Koppel, as shown in attached Figure 1, Cal Farm Facility. Samples obtained between 1997 and 1999, when the well was inadvertently destroyed, were an order of magnitude higher than any other groundwater sample obtained from the Cal Farm site. The concentrations of nitrate (as nitrogen) in this well are much closer in magnitude to those observed in the Koppel's proximate well, KP-2, as shown in Table 1. Groundwater elevations obtained by Koppel suggest that MW-6 is upgradient of KP-2, whereas groundwater elevations obtained by Cal Farm Supply suggest that MW-6 is downgradient of Koppel. Regional Board staff believe that the nitrate observed in MW-6 is not related to Cal Farm Supply,but was related to Koppel's activities. By 1 December 2004, Koppel needs to submit a work plan to install a monitoring well in the vicinity of Sonora Avenue north of Koppel's facility in order to assess whether the nitrate plume identified at Koppel is adequately defined to the north. Table 1. Nitrate-N concentration (mg/1) comparisons between MW-6 and nearby monitoring wells. MW-6 KP-2 MW-2 MW-3 Date (Cal Farm) (Koppel) (Cal Farm) (Cal Farm) December 1997 216 200 75 13 June 1998 367 192 63 14 September 1998 329 210 64 22 March 1999 249 158 48 18 Draft Monitoring and Reporting Program In the Evaluation Report, Koppel proposes that the monitoring frequency be reduced from semi-annually to annually in the first quarter. Koppel has been monitoring 14 shallow monitoring wells and 3 deep monitoring wells since 1999, and four of these since 1996. Since the trees have been established, very few of the monitoring wells exhibit seasonal fluctuations in nitrogen concentration. The wells that do show a correlation between groundwater elevation and nitrogen concentration exhibit the maximum concentration during the dry season. While Regional Board staff concur with Koppel's proposal for