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' 18 November 2004 <br /> AGE-NC Project No 97-0301 <br /> Page 5 of 6 <br /> Generally,a steep downward vertical gradient was observed from wells MW-S,MW-9,and <br /> ' MW-12_y d etween the Second Water Zone, Third Water Zone, and Fourth Water Zone, <br /> a very slight upward vertical gradient was observed between the First Water Zone and the ff <br /> ' Second Water Zone (Figure 3) <br /> Analysis of ground water samples collected from MW-1 and MW-7 suggest the dissolved <br /> plume is comprised of TPH-g, BTEX, and 1,2-DCA The core of the First Water Zone <br /> dissolved gasoline plume appears to be currently distributed near the location ofwells MW-1 <br /> ' and MW-7, and contained within network of wells consisting of MW-2, MW-3, MW-4, <br /> MW-6, MW-9A, MW-10A, MW-11A, and MW-12A(Figure 4) <br /> ' - Substantial concentrations of dissolved TPH-d and TPH-k have previously been detected in <br /> water samples collected from wells MW-1 and MW-7, indicating a limited distribution of <br /> TPH-d and TPH-k in the area assessed <br /> BTEX and 1,2-DCA concentrations in ground water samples MW-1 and MW-7 were <br /> substantially above their respective Maximum Contaminant Levels in drinking water <br /> AAME, <br /> til A - h 1� UUyLtiVery low concentrations of MTBBOW.-rd ave been detected at wells <br /> MW-1, �V�.VV ;M ;M L i;and MW-7,pN a1 g that there is only a minor <br /> '. impact of these components <br /> - Based on the past four quarterly ground water monitoring events, the lateral and vertical <br /> ' extent of dissolved petroleum hydrocarbons appears to be limited o First Water Zone wells <br /> MW-1 and MW-7 at the site and approximately,*feet,as of e" VK <br /> 5.0. RECOMMENDATIONS <br /> ' Based upon data collected during June 2004, AGE recommends <br /> ' - Continued ground water monitoring utilizing wells MW-I through MW-12,the third quarter <br /> 2004 ground water monitoring event was performed on 30 September 2004 The fourth <br /> quarter ground water monitoring event should take place in December 2004 <br /> - If applicable,conduct future ground water monitoring events concurrently with the Cal-Tank <br /> Lines site (3105 South El Dorado Street) <br /> - No additional ground water monitoring wells/soil borings are warranted at this time and the <br /> existing monitoring well network maybe sufficient to complete a site Corrective Action Plan <br /> (CAP) and/or Problem Assessment Report (PAR) <br /> 1 <br /> ' Advanced GeoEnvi ron mental,Inc <br /> 1 <br />