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i Mr.*James Barton,RWQCB May 14,2008 Work Plan for Additional Site Assessment Former Dolly Madison Bakery,Stockton,California Page 4 subsurface investigations of neighboring . properties. Clay' and silt mixtures have predominately been noted between approximately 90 and 120 feet bgs. Hydrogeology Groundwater flow direction beneath the site has only been evaluated during one monitoring event, completed during the first quarter 2008. Information obtained from this monitoring event is discussed in the following subsections of this document. - Shallow Water Bearing Interval. Depth to groundwater beneath the site has fluctuated between approximately 18.5 and 25 feet bgs between 1997 and 2004. Depth to groundwater was measured at approximately 19 feet bgs in February 2008. An east groundwater flow direction, at an average gradient of 0.002 ft/ft, was observed at the time of the first quarter 2008 groundwater monitoring event (February _14, 2008). A groundwater elevation contour map for February 14, 2008 is presented as Figure 6. Mid-Depth Monitorifig Wells Depth to groundwater in the mid-depth monitoring wells ranged from 19.07 feet bgs to 22.80 feet bgs (well,MW-14) at the time of the first quarter 2008 monitoring event. The groundwater level observed at well MW-14 is nearly four feet lower than the groundwater levels observed at wells MW-8 and 'MW-9 and may be anomalous. A groundwater elevation contour map using measurements collected from the mid-depth monitoring wells at the time of the February 14, 2008 groundwater monitoring event is depicted on Figure 7. A southeast groundwater flow direction, at an average gradient,of 0.03 ft/ft, is illustrated on this figure. Deeper Water Bearing Interval Depth to groundwater in the deeply screened monitoring wells ranged from 19.00 to 19.57 feet bgs at the-Aime of the first quarter 2008 monitoring event. Figure 8 presents a groundwater elevation contour map for the lower water bearing interval using the measurements collected on February 14, 2008. Northeast groundwater flow, at a relatively low groundwater gradient(0.001 ft/ft), is depicted on Figure 8. Hydrogeology.at Neighboring UST Sites Monitoring of shallow groundwater flow direction has been completed at several sites in the neighborhood immediately surrounding the subject site for multiple years. Given the close proximity of these sites to the former Dolly Madison property, information collected on KATimothy.Kong Property\Work P1ans\Kong-mayO8wor1cp1an.doc