SITE INFORMATION AND CORRESPONDENCE

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( KLE/NF-ELDER B14M ft p'..fth,SpluMoni. • 11. As shown in Table 8, nitrate-nitrogen was detected in the groundwater samples from MW-2 and MW-5 at concentrations of 58.9 mg/I and 49.7 mg/I, respectively. Well MW- 2 is located at approximately the southeast corner of the nursery property. Both concentrations are in excess of the State of California Maximum Contaminant Level [MCL] for nitrate-nitrogen of 10 mg/I in drinking water as expressed in §64431 of Title 22 of the California Code of Regulations [CCR]. These results are significant for two reasons. First, because this is the third of four groundwater monitoring events that revealed nitrate-nitrogen in the monitoring well upslope (upgradient) of the nursery above the MCL. Secondly, the concentration of the nitrate-nitrogen in this upgradient well (MW-2) is significantly higher than the concentration in the downgradient well (MW- 5). 12. Based on the limited investigation and monitoring data obtained, it is unknown if the shallow perched water is continuous between MW-2 and MW-5. Based on the limited investigation and monitoring data obtained, it is unknown why the concentrations increased in the upslope well (MW-2) while the concentration decreased in MW-5 (downgradient well) between the March 1998 and present. Especially since Norman's Nursery began irrigating on April 20, 1998 and has irrigated all but three days since May 16, 1998. It is unknown what the source of the perched water and nitrate-nitrogen is, that existed upslope of the nursery. Natural recharge, springs, vernal pools and the cattle grazing may be the explanations. Furthermore, the cause of the decrease and/or dilution of the nitrate-nitrogen in the groundwater near MW-5 are also unknown. 13. Total annual precipitation near the site has recently been [as high as] approximately 35 inches. 14. During three of the four quarterly monitoring events conducted to date, the • concentrations of nitrate-nitrogen in all of the sample locations were consistent. In fact, the concentrations of nitrate-nitrogen upstream of the nursery's basin were frequently greater than the water within the basin (or its discharge, as applicable). The only exception was at the beginning of the irrigation season (Third Quarter 1998) prior to the nursery's reinstitution of treatment of their tailwater with KI-Nitrifier. 15. Kleinfelder recommends that the groundwater monitoring be continued. 16. Since surface water quality does not appear to be impacted significantly by Norman's Nursery's activities throughout the year (4 quarters) of monitoring that has taken place at the subject site, Kleinfelder recommends a decrease in the frequency of monitoring. Therefore, on behalf of Hakeem, Ellis & Simonelli and Norman's Nursery Kleinfelder recommends that the Monitoring & Reporting Program No. 97-811 be revised in the following manor: Norman's Nursery should continue to treat the tailwater within Basin B using KI- Nitrifier(or comparable treatment alternative) - daily surface water flow monitoring and observation should continue - weekly surface water sampling and analysis should be reduced in frequency to monthly - monthly surface water sampling and analysis should include all surface water sampling points detailed in M&RP No. 97-811 - additional surface water sampling for analysis should be conducted within 2 to 8 hours of the opening of the culverts and the release of any water to Potter Creek • 117226.E02/STO12R0696 Page 10 of 43 September 14, 2012 Copyright 2012 Kleinfelder