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Remedial Status Report-Tosco(Former BP)Station No 11193 November 13,2001 PERFORMANCE TEST In conjunction with the August 3, 2000 initial purging event, GR collected depth to groundwater (DTW) measurements to qualitatively evaluate the radius of influence generated by the purging of groundwater from monitoring wells MW-1 and MW-2 Seven groundwater monitoring wells in the vicinity were , monitored during and after purging in order to characterize the effect of purging on the static groundwater levels Initial Pumping Effectiveness The initial intent was to purge one half of 5,000 gallon target volume from MW-1 and one half from MW-2 to test each well MW-1 was purged first and produced approximately 2,500 gallons of groundwater in approximately 2 hours MW-2 was then purged for approximately two hours, during which it produced approximately 500 gallons of water Purging was resumed in MW-1 for approximately 70 minutes to collect the remaining 2,000 gallons making up the entire 5000 gallon total (vacuum truck capacity) As a result, the majority of the groundwater purged came from MW-1, which appears to have hydraulic communication with the UST pit J Static Groundwater Level Observations During purging, GR personnel collected DTW measurements from monitoring wells MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, VW-1 and MW-10 The distances from MW-1 to the observation wells ranged from 47 4 feet to MW-2 and 125 feet to MW-6 Monitoring well locations are shown on Figure 2 DTW readings were collected periodically, beginning prior to initiation of groundwater purging until 20 minutes after completion of purging activities by which time the static water table was reestablished Groundwater level data are summarized in Table 2 Purging was initiated in MW-1, located adjacent to the southeast of the UST pit This well was purged for 120 minutes, during which approximately 2,500 gallons of groundwater were removed During this purging, the static groundwater level declined in nearly all observation wells on site Well MW-2 had an initial static groundwater level of 12 35 feet bgs which lowered to 13 25 feet (0 9 foot difference) after 116 minutes of purging MW-1 The next greatest magnitude effect was at MW-5, with a drop of 0 5 foot Lesser changes in static groundwater levels were measured at all other observation wells on this site Groundwater level changes appear to be related to the distance from the observation well to the purging , well After 120 minutes purging in MW-1, the vacuum truck moved to purge well MW-2 Purging was restarted from MW-2 at 126 minutes after start of the test The well was purged dry within 20 minutes of starting (146 minute total) MW-2 was purged for a total of 108 minutes (234 minute total time), generating approximately 500 gallons of groundwater Only minimal changes in the static groundwater levels were noted in nearby observation wells Drawdown in the observation wells after 230 minutes ranged from none in MW-4 and MW-5 (80 feet and 52 feet from MW-2, respectively), 0 06 feet in MW- 3 (68 feet to MW-2), and 0 02 feet in MW-1 14020504-2 2