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U-Haul#709-50 Preliminary Site Conceptual Model Blaes Environmental December 15,2006 46 Ievels were measured to the nearest hundredth of a foot (0 01 ft) using a Heron electronic water-level sounder The water level depth and time of measurement were recorded on a standard field data sheet The water levels are tabulated with previous monitoring data in Table 5 Groundwater depth measurements were performed in accordance with Blaes Environmental groundwater monitoring procedures Groundwater elevations measured at the site on September 18, 2006 ranged from approximately 28 76 feet below mean sea level in well MW-2A to approximately 31 29 feet below mean sea level in well MW-I IB (Table 5) Groundwater measurements from U-HauI's "A" and "B" well casings were used to derive a groundwater gradient map illustrating groundwater conditions at the site for all wells that did not have submerged screens The average groundwater flow direction across the U-Haul site using the September 18, 2006 data from the selected U-Haul "A" and "B" well casings appears to be radiating outward from a high located near the center of the site at an average gradient of 0 014 feet per foot across the site (Figure 7) A groundwater gradient map was not generated for the "C" horizon as all screened intervals in the "C" wells were submerged In addition to water level depths, Blaes Environmental also measured dissolved oxygen (DO) levels in all well casings prior to and during purging activities using a YSI-85 DO meter 44.2 Groundwater Sampling On September 19 and 20, 2006, Blaes Environmental collected 25 groundwater samples from the on-site and off-site monitoring wells that contained water The groundwater Ievels at the site are subject to a wide range of seasonal fluctuation as seen on the Hydrograph presented as Figure 8 During the first quarter of 2006, groundwater levels were too low to allow sufficient water column in the "A" casings to warrant the collection of groundwater samples Also, free product was detected in well MW-3B and did not allow for sampling of that well for this event Groundwater sample collection involved purging approximately three well volumes of groundwater from each casing and allowing the groundwater to recharge to 90% of its original level prior to sample collection Purging was performed during this event with a 1 5-inch ProActive "Mini-Monsoon" 12-volt, battery-operated groundwater pump The pump was decontaminated before and after purging each well with a liquid detergent wash (Liquinox®) and a tap-water rinse Periodic parameter readings were Page 13