SITE INFORMATION AND CORRESPONDENCE

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KLE/NFELOER B 9P IroPI¢.R19ht5oluMani. • � ry t 17. Based on the laboratory reports for the surface water samples obtained, it appears that additional sources of nitrate-nitrogen exist upstream of Sample Location S1A. Kleinfelder recommends that the RWQCB review other potential sources of nitrates- nitrogen in the surface and groundwater within the area. 18. Past subsurface exploration of the property by Kleinfelder shows that soil beneath the site can be very generally summarized as a clayey gravel (with an inconsistently present 2-foot thick interbedded layer of sandy clay or clayey sand) present to a depth of approximately 17 feet). The clayey gravel is generally underlain by an approximately 5- 10 foot thick layer of silt or clayey silt. The silt layer is underlain by a silty sand which may contain interbedded layers of clay or clayey silt. 19. The area around the Escalon Bellota Road bridge over Potter Creek appears to be in connection with the shallow perched groundwater in that immediate area. If the two are in connection with each other, then water quality in the area of MW-5 could be influenced by the water quality within that area of Potter Creek. It is unknown if Potter Creek is a gaining or loosing stream in that area. Past water flow estimates on Potter Creek as a part of the Nursery's monitoring has also pointed to discrepancies in the creek's flow in that area. However, due to the consistent lack of perched water in the nursery's wells MW-4s and MW-4d, it appears that the area in which Potter Creek is in connection with the shallow perched groundwater is limited. 20. Significant flows of surface water apparently originating from the dry pasture two lots east of the nursery entered the southeast corner of the nursery from approximately May 21 to 28, 1999. The water was observed from the air by Ms. Linda Santos of Norman's Nursery. The water entered the nursery property and flowed into the triangular basin behind the nursery offices. Once it filled that basin (which had been at a much lower • level), the water flowed into the nursery's eastern canal and on to Sample Location S1. This additional water increased flow in sample location S1 approximately 10 to 60 times over that noted in previous days. The water appeared turbid where it entered the nursery property. The water had the potential to be adversely affecting surface water quality on the nursery. Therefore, on May 25, 1999, a sample of the surface flow was obtained near the nursery's eastern property line by Ms. Linda Santos of Norman's Nursery. The sample was transported to FGL Environmental Laboratory in Stockton, California for analysis. Chemical analysis showed no detectable nitrate-nitrogen (<0.1 mg/I) and no detectable ammonia-nitrogen (<0.2 mg/1) in the sample. However, the initial surge of the flow was not sampled. The weekly sample obtained from surface water monitoring location S-1 on May 29, 1999, did however, contain 11 mg/I of nitrate as nitrogen. The concentration of 11 mg/I is above the MCL and is an increase of approximately 10-times the concentration of the previous two weeks' samples. When the increased flow subsided, the concentrations of nitrate-nitrogen in S-1 decreased 10-fold to its previous concentrations. According to Ms. Linda Santos, increased flows of this type were noted during past summers by Norman's Nursery personnel, but apparently went unreported to nursery management and were therefore not reported to Kleinfelder or sampled. In December 1997, several borings were advanced on the Norman's Nursery site. The soil encountered in those borings can be very generally summarized as a clayey gravel (with an inconsistently present, 2-foot thick interbedded layer of sandy clay or clayey • sand) present to a depth of approximately 17 feet. The clayey gravel is generally 117226.E02/STO12R0696 Page 11 of 43 September 14, 2012 Copyright 2012 Kleinfelder