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� S�SWuCs <br /> +?J 2 <br /> Ground Zero Analysis, Inc. d��r "� I 4stnq.iU4 (p �' ' <br /> 1172 Kansas Avenue " r <br /> T Modesto,California 95351 p&, 9 .I n Jp,,� '3 V S n�1 Y" <br /> ..,,.fy. (209)522-4119/Fax(209)522-4227 'J <br /> 10 <br /> � e I rA 1 d <br /> IV p� r v <br /> vMayXS2013 ' fvin, r -f1i l �� I ' Os.l �p „1P �o) �µ/ ddtj �. <br /> J V � e <br /> Project No.: 425.2 ,J 5 tU <br /> Project Name: George's Service Z tU ti <br /> Ms. Vicki McCartney 11� " - U�t Q9G� S O' IuYterf. <br /> San Joaquin County Environmental Heath Departments /I <br /> 600 East Main Street <br /> ,t Stockton, CA 95202 S�� s �( all <br /> tj <br /> RE: Additional Air Sparge Well Installation Work Plan 9 q <br /> George's Service, 1600 Durham Ferry Road, Tracy, CA <br /> Hello Vicki: <br /> Operation of Phase I and Phase II of the air sparging system began on March Ist and August 24th I25 ; <br /> 2012 and has been in continuous operation since. Currently, air is being injected into five (5)of <br /> the Site's wells including OS-1, OS-2, AS-1, AS-2 and AS-3. One (1) year of monthly <br /> performance groundwater monitoring has shown that the air sparging system is effective at / <br /> increasing the dissolved oxygen (DO) levels in the groundwater as observed in select wells (OW- <br /> 1 & OW-2). Refer to the attached Table 1 for performance groundwater monitoring data <br /> collected from March 2012 thru May 2013. <br /> It is noted that minimal effect has been observed in the core of the groundwater plume, notably <br /> in the vicinity of AS-1 and monitoring well MW-2. Contaminant concentrations in the vicinity <br /> of the injection wells are also being reduced, as observed in OW-1. Refer to the attached Table 4 <br /> 2. p�yk 0 Nb1t V10. <br /> Some of the special relationship of sparge wells to observation wells do not readily lend to <br /> measuring the effectiveness of the air sparge system. For example - AS-1 with MW-1 & 101; .yt <br /> these monitoring wells are not ideally spaced for measuring the results of sparging. ��r Avow <br /> To address the contaminants in the core of the plume, Ground Zero Analysis, Inc. (GZA) <br /> recommends that three (3) additional air sparge wells be installed within the high concentration tt. <br /> portion of the groundwater plume(>5,000 pg/L TPH-G) as shown in Figure 2. <br /> Figure 1 is a site map including the TPH-G concentration contours created using the 2"d Quarter <br /> 2013 groundwater monitoring data collected on May 1", 2013. Figure 2 is a site map including <br /> the locations of the three (3) proposed air sparge wells (AS-4, AS-5 &AS-6). <br />