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i Mr Terry Tarditi April 5,2005 ' Page 3 iAnalytical laboratory Kif£Analytical,Inc, Davis,California. ' (Cahfornia Department of Toxic Substances Control Certification No 2336) Sample exceptions None Shallow groundwater gradient: Flat Shallow groundwater flow direction. N/A Average depth-to-water 69.11 feet Average change in shallow groundwater elevation from 4th qtr(2004) to Is,qtr (2005) 3 32 feet ' DISCUSSION Based on the first quarter's data,the groundwater hydraulic gradient remains relatively flat,a reasonable hydraulic gradient could not be measured, as shown in Figure 2 This flat hydraulic gradient is helping retard further lateral migration of constituents of concern of which has been documented by the field investigation iresults summarized in Brown and Caldwell's Subsurface Investigation Results and Site Conceptual Model,June 28,2005 The on-site supply well has been sampled on a quarterly basis since November 2002 and has never contained any detectable concentrations of any constituents of concern Therefore,samples from this well are not included in the discussions below i ' BTEX. The reporting limits for all constituent concentrations in MW-1 were increased to 50 micrograms per liter(pg/L) from 25 µg/L due to known high concentrations of MtBE The dilutions were necessary because the MtBE ' concentrations were out of the calibration range for the target analyte Samples from MW-1 are analyzed multiple tunes by the analytical laboratory to bring the correct dilution into the calibration range The reporting limits remained the same for wells MW-2 and MW-3 and decreased from 10µg/L to 0 5 µg/L for MW-4 BTEX concentrations were below their respective reporting limits m all of the wells These results are consistent with previous quarters Per the PHS/EHD's request,BC has worked with the analytical laboratory to detertinme when it is feasible to quanufy the BTEX constituents without damaging the equipment, especially in samples from MW-1. • I Thu rtp01t aw prepared to actn►daruti rvtth t&rtandar&of t&eRurmunnrta!rovuxlhng rrtdwity at t&A me tt suf prspmed It abawwld oat ht rehtd*=by potxt a&r A"t&W far trhoi,t tt xW prepa+rd and t&a av#to the exhot of the mea of aak poub aw awhm,-a Thu repot der ttatgoaraotte tbat oo addtttaoal estmrortraeotal t»otamtoaA=bryond MW detmbtd of thu tepee Mal at As trte ' P•\27000\127960 T do T TnwJu xg\Reports\lst-05gtr doe