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Dopaco, Inc. • - 2 - • 30 January 2013 + <br /> 800 W. Church St., Stockton <br /> San Joaquin County <br /> with soil and grab groundwater samples from 15' logs to 40' bgs, and deeper if <br /> necessary, to provide vertical delineation of toluene. A mobile lab will be onsite to <br /> support the above field decisions. Figure 4 MS Project Schedule of Milestones shows <br /> the fieldwork to be completed and an investigation report submitted by 29 March 2013. <br /> The following table from my 18 September 2012 letter shows the CPT-MIP-2012-13 <br /> groundwater sample results by depth and tolueneNOCs concentrations in micrograms <br /> per Liter (ug/L). <br /> De th Toluene 2-Butanone 4-Meth -2 Pentanone Acetone <br /> 18.5' 410,000 <63,000 <63,000 <63,000 <br /> 32'-33' 510,000 74,000 250,000 <71,000 <br /> 32'-33' 500,000 170,000 340,000 110,000 <br /> 1 =duplicate sample <br /> In a phone discussion with GC on 4 December 2012, the primary reason given for <br /> grouting up boring DMW-2 (BH-2) in November 2012 were GC concerns that <br /> contamination of the underlying sandy aquifer unit might occur if the boring was <br /> advanced through overlying contaminated soils. Since the DH-2 had already been <br /> grouted and the remobilization for one monitoring well was not cost effective, I agreed to <br /> not install DMW-2, and said that the vertical extent of contamination needed to be <br /> demonstrated per my 18 September 2012 letter. We also discussed installing additional <br /> wells if necessary at a later date. <br /> The Workplan is approved with the condition that DC contact me during the field work, <br /> to discuss their plans to conduct or not conduct deeper sampling, or to add step out <br /> boring locations. Please procure the necessary borings permit and give myself and the <br /> San Joaquin County Environmental Health Department at least 3 working days notice <br /> prior to initiating fieldwork. <br /> Groundwater monitoring will be conducted quarterly for DMW-1, DMW-3, and DMW-4, <br /> with the next monitoring report due 30 April 2013. Laboratory analyses for groundwater <br /> monitoring and for the soil and grab groundwater samples will be USEPA Method <br /> 8015M for TPHd and USEPA Method 8260B with a full VOCs scan. Reductions in <br /> monitoring frequency or analytes, if appropriate, may be recommended in the following <br /> monitoring report due 30 July 2013. <br /> You may contact me with questions by phone at (916) 464-4615 or by email at <br /> b rton waterboards.ca. ov. <br /> ?James L. L. Barton, P. G. <br /> Engineering Geologist <br /> UST Program <br /> cc: see attached list of interested parties <br />