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rvis. viuni vuuunnuw - c <br /> NuStar Terminals Stockton Facilij <br /> of TPHg at 120,000 micrograms per liter (Ng/L), while PS/MW-14 contained the highest levels <br /> of TPHd and benzene at 12,000 Ng/L and 7,700 Ng/L, respectively. ST/MW-1 contained the <br /> highest concentrations of toluene at 4,100 Ng/L, ethylbenzene at 1,200 Ng/L, MTBE at <br /> 94,000 pg/L, and TBA at 4,600 Ng/L. The highest concentration of TPHg in the lower zones <br /> was detected in downgradient monitoring well ACA-213 at 5,400 pg/L at a depth of 51 feet bgs. <br /> Pursuant to MRP No. No. R5-2007-0818, NuStar is proposing to terminate sampling for <br /> TAME, ethyl tertiary butyl ether (ETBE), DIPE, ethanol, and methanol in seven wells based on <br /> a history of non-detects (NDs). We concur that the monitoring requirements for these <br /> oxygenate compounds in these wells have been fulfilled and therefore may be removed from <br /> the sampling program. <br /> On 21 May 2009, Central Valley Water Board staff met with you and representatives of Ash <br /> Creek to discuss a path forward for the follow-up vertical delineation investigation proposed in <br /> the 30 January 2009 Vertical Groundwater Investigation Results Report (Investigation Report) <br /> and resolve comments presented in our 22 April 2009 letter. That letter directed NuStar to <br /> submit a Work Plan to vertically delineate all COCs at the four proposed boring locations (P-A <br /> through P-D) to ND and to install monitoring wells into the D-zone (about 90 feet bgs) where <br /> D-zone grab groundwater sampling was proposed. In addition, we requested that location P-D <br /> be relocated north to the area of NS-11. We also differed with NuStar's request to conduct <br /> laboratory analytical method 8015M using silca gel cleanup. <br /> At the completion of the meeting the Central Valley Water Board staff concurred with NuStar's <br /> proposal to (1) eliminate boring P-D, (2) perform lower zone (about 90 feet bgs) grab <br /> groundwater sampling at locations P-A and P-C, and (3) perform a comparative laboratory <br /> analysis for TPHd using three variations of Method 8015 B that will include no filtration, <br /> filtration by glass beads, and silica gel cleanup. The results of the deep grab groundwater <br /> sampling will be used to develop a strategy for proceeding with well installation in the <br /> 90-foot bgs water bearing zone. NuStar agreed to submit a work plan to perform the proposed <br /> sampling and well installations by 19 June 2009, as requested by Central Valley Water Board <br /> staff. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4811 or <br /> b etayl o rCc)wate rb o a rd s.ca.g ov. <br /> BRIAN TAYLOR, PiG. <br /> Engineering Ge9togist <br /> cc: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton <br /> Ms. Rita Koehnen, Port of Stockton, Stockton <br /> Ms. Vikki Goodenow, NuStar Energy L.P, San Antonio Texas <br /> Ms. Amanda Spencer, Ash Creek Associates, Inc., Portland, OR <br /> Mr. Jeremy Hughes, LFR, Granite Bay <br /> Mr. Rusty Benkosky, Stantec Consulting Corporation, Rancho Cordova <br />