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.<11) Califor -.I Regional Water Quality C 9trol Board <br />Central Valley Region <br />Karl E. Longley. ScD, P.E., Chair <br />I.inda S. Adams <br />i ./ <br />Sacramento lain Office <br />I 1020 Sun (_ enter Drive 200. Rancho ordova. California 956RE <br />'.‘ <br />Phone (916) 364-32QI • FAN (016)464-4645 <br />http //w'.i i i iterhoards ca gm /central alley <br />\ED Arnold <br />Schwarzenegger <br />(ioverilor <br />DEC 0 6 2007 <br />5 December 2007 <br />Ms. Donna Sartini-Gardner <br />1206 W. Struck Ave. <br />Orange, CA 92867 <br />ENVIRONMENT HEALTH <br />PERMIT/SERVICES <br />Mr. Ronald Jr. and Ms. Bonnie Barber <br />10411 Small Rd. <br />Manteca, CA 95336 <br />DOCUMENT REVIEWS, DONNA GARDNER PROPERTY, 26056 N. THORNTON ROAD, <br />THORNTON, SAN JOAQUIN COUNTY (REGIONAL BOARD CASE # 390412) <br />I reviewed the Static Water Levels Study (Study), submitted 27 August 2007 and the Quarterly <br />Report — Third Quarter 2007 (Report). submitted on 1 November 2007 by your consultant <br />Advanced GeoEnvironmental Inc. (AGE). The Study provides the results of an evaluation of <br />the Thornton Municipal Supply Well No. 2 (Well 2) pumping effects on the water levels in the <br />monitoring wells at the site, in order to determine whether a hydraulic connection exists <br />between the shallow and deep aquifers at your site. The Report contains the results of <br />July 2007 groundwater monitoring event with AGE's recommendation to reduce the list of <br />analyses to Total Petroleum Hydrocarbons as gasoline (TPHg), benzene (B), toluene (T), <br />Ethylbenzene (E), and Xylenes (X), since fuel additives have not been detected since 2005 <br />and lead scavengers have never been detected by groundwater monitoring. <br />The Study involved the use of electronic dataloggers to measure water level changes in <br />monitoring wells MW-4 and MW-6, and in Well 2 (enclosed Figure 2). One datalogger was <br />also suspended above the water column in MW-4 to measure changes in atmospheric <br />pressure, in order to calibrate data for corrections due to changes in atmospheric pressures. <br />Tidal changes and precipitation influences were also evaluated for effects on water levels. In <br />relation to Well 2, MW-4 is located less than 75 feet to the south (downgradient) while MW-6 <br />is 220 feet to the south. Well 2 has 30-inch conductor casing and a sanitary seal extending <br />from surface to 70 feet below ground surface (bgs) separating it from shallow groundwater <br />(9 to 30 feet bgs); is screened from 135 to 150, 160 to 185, and 225 to 235 feet bgs; and <br />shows a 21 foot drop (to 44 feet bgs) from the static water level when pumping. MW-4 drilling <br />logs show silts and sandy silts from 16.5 to 28 feet bgs (total depth). The Study concludes "A <br />perceptible, but probably insignificant response (to pumping of Well 2) appears to occur in the <br />water levels of MW-4...". while a smaller and more delayed response occurred in water levels <br />in MW-6. <br />The Report states that depth to water varied from 10 to 15 feet below ground surface at the <br />site. Shallow groundwater flow direction at the site was towards the southwest, away from <br />Well 2. Well 2 is sampled quarterly and has never been impacted by petroleum hydrocarbons. <br />In contrast since 1991, TPHg and BTEX have consistently impacted shallow groundwater <br />sampled from MW-4. In July 2007, groundwater results for MW-4 were TPHg, 5,300 ug/L; <br />T, 6.8 ug/L; E, 110 ug/L; and X, 53.5 ug/L, which represent the highest Site concentrations for <br />these petroleum hydrocarbon constituents since 2002. The remaining five monitoring wells <br />were non-detect for all constituents. <br />Comments: <br />California Environmental Protection Agency <br />%," necycled pap".