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' Mr. Nuel Henderson Page 2 of 5 ' the site rose an average of 0.81 feet since the fourth quarter event in November 2004. The potentiometric surface was above the top of the screened intervals in monitoring wells MW4 ' through MW 13B, MW 15B, MW15C, MW 16B and vapor wells VW 1 and VW4. Vapor well VW5 was dry. ' During this event an upward vertical gradient component was present across the site. Wells screened deeper than 60 feet had higher potentiometric surface elevations than shallower wells ' in close proximity. Examples are well pairs MW11MW6, MW31MW7, MWI5AIMW15B and MW 16A/MW 16B. This is the first time an upward gradient component has been observed in the MW 16 well pair. A potentiometric surface map generated using the February 22, 2005 ' groundwater elevation data for most groundwater monitoring wells, regardless of screen depth, is shown on Figure 2. The gradient across the site according to this interpretation was approximately 0.001-0.002 feet per foot in an easterly to northeasterly direction. Figure 3 is a ' gradient map utilizing data from the shallower wells only (screened above 60 feet). Gradient is approximately 0.0015 ft/ft in a southeasterly direction. The gradient computed from the deeper wells only (screened below 60 feet) ranges from approximately 0.001 - 0.003 ft/ft. ' Flow direction in the deeper zone ranges from southeasterly to northeasterly (Figure 4). Groundwater monitoring data are summarized in Table 1. Monitoring data sheets and well construction details are included in Attachment A. ' On February 22 23 and 24, 2005 a Ground Zero technician collected groundwater samples • from monitoring wells MW1 through MW5, MW7 through MW9, MW12, MW13B, MW14, ' MW15A through MW15C, MW16A and MW1613; and from vapor wells VW1 and VW3. ' A minimum of three well casing volumes was purged from each well prior to sampling. During the purging process, physical parameters (pH, electrical conductivity, and temperature) were monitored. Subsequent to parameter stabilization, and 99-100% recovery of initial depth ' to groundwater measurements, groundwater samples were collected and placed in an iced cooler for transport to Argon Laboratories (ELAP #2359) under chain of custody protocol. ' Analysis consisted of gasoline oxygenates, EDB and 1,2-DCA by EPA Method 8260B, TPHg by EPA Method 8015B and BTEX by EPA Method 8021B. Purge water was transferred into marked 55-gallon drums approved by the Department of Transportation (DOT). The waste is stored onsite within a secured area. Purge logs are included in Attachment A. ' GROUNDWATER ANALYTICAL RESULTS Groundwater Monitoring Wells TPHg and benzene were detected in all sampled wells except MW7, MW9, MW12, MW15A, ' MW15B (were only TPHg was detected), and MW15C. Dissolved TPHg and BTEX levels in the remaining monitoring wells were within historical ranges, and appear to be stable to . decreasing. TPHg and BTEX concentration data are summarized in Table 2. Attachment B ' G:1GROU"ZEIROEKIQMR1200511 gm2005.doc