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Mr. Jeff Baker - 2 - 18 September 2008 <br /> Tesoro Companies, Inc. <br /> Monitorin Wells <br /> TS/MW-1A TSIMW-1B TSIMW-1C TS/MW-1D TSIMW-2D <br /> Micro rams per liter(wq/L <br /> TPHq 1.900 3.300 840 <50 9.500 <br /> TPHd 2.600 1.000 580 520 2.500 <br /> Benzene 9.6 1,400 270 1.6 5.300 <br /> Toluene 0.69 6.7 1.2 <0.50 29 <br /> "!benzene 13 <2.5 <0.50 <0.50 < 15 <br /> Total xylenes 23 8.8 1.3 <0.50 54 <br /> MTBE 6.0 92 130 4.7 < 15 <br /> TBA 15 250 450 5.4 1.700 <br /> TAME <br /> .50 <2.5 1 <0.50 <0.50 < 15 <br /> Explanation <br /> TPHg —total petroleum hydrocarbons as gasoline <br /> TPHd —total petroleum hydrocarbons as diesel <br /> MTBE —methyl tertiary butyl ether <br /> TBA—tertiary butyl alcohol <br /> TAME—tertiary alcohol methyl ether <br /> < — less than <br /> The benzene concentration of 5,300 pg/L in TS/MW-2D represents the continuation of an <br /> overall increasing trend that started in December 2005. Depth to groundwater typically varies <br /> from five to nine feet bgs. Laboratory results for soil samples collected between 60 and 119 <br /> feet bgs during the advancement of boring TS/MW-2D in June 2005 show that very low <br /> concentrations of TPHg, TPHd, benzene, toluene, and TBA are sorbed to the soi12 at depth. <br /> The Evaluation considered 11 remedial options consisting of three vadose zone technologies <br /> (excavation, soil vapor extraction, and bioventing) and eight groundwater technologies (air <br /> sparging, bio sparging, bioremediation, dual phase extraction, groundwater extraction, in-situ <br /> chemical oxidation, enhanced bioremediation, and monitored natural attenuation [MNA]). <br /> Tesoro considers the primary media of concern to be D zone groundwater at depths greater <br /> than 80 feet bgs and therefore has determined that there is no need for vadose zone cleanup <br /> technologies. Based on this objective and the Evaluation, Tesoro recommends submitting a <br /> pilot study work plan to test the injection of oxygen and/or nutrients or various oxidants into the <br /> subsurface. Laboratory analytical and stratigraphic data from the well installation will serve as <br /> the basis for preparing the pilot study work plan. <br /> For installation of TS/MW-3D, Tesoro proposes to advance the boring to 135 feet bgs, collect <br /> soil samples for lithologic identification, and submit select soil samples for laboratory analysis. <br /> Grab groundwater samples will be collected at coarse-grained units encountered during <br /> drilling. If coarse-grained units are not encountered, only one grab groundwater sample is <br /> proposed for collection at the total depth (TD) of the boring. If coarse-grained units are <br /> encountered below 115 feet bgs, the boring will be advanced to as deep as 135 feet bgs and <br /> then backfilled with grout or bentonite to 115 feet bgs for well installation. If an aquitard is <br /> encountered, the boring will be terminated just beneath 115 feet bgs. <br /> 2 Additional Site Assessment Report, 19 August 2005, SECOR <br />