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Mr. Mike Huggins February 9,2009 Groundwater Monitoring Plan Page 4 of 8 Granite Construction Company,Vernalis Plant south and cast of the Teichert Vernalis plant(Liese Schadt[LSCE]personal communication with P. Mercurio [Teichert], October 2002). Further;reduced usage of local surface water supplies by local interests,which may have caused a corresponding increase in local groundwater pumpage,has been reported(Liese Schadt [LSCE]personal communication with J. Muller [Teichert],October 2002). Groundwater Quality The groundwater in the vicinity of the project site is reported to be of moderate quality,with elevated nitrate concentrations(over 20 mg/L)and groundwater from the deep aquifer containing proportionally more sulfate than shallow aquifer water(Hotchkiss and Balding, 1971). Local monitoring efforts conducted by Teichert since 1994 are in agreement with the above observations (Attachment 4). Specifically,the electrical conductivity(EC)of samples retrieved from two shallow wells (Hall and Faulkner domestic wells)(see Figure 2)typically ranges between 900 and 1,000 pS/cm and.has been stable during the period of record(Figure 11). The EC of samples retrieved from deep wells typically ranges between 800 and 950 VS/cm and has also been stable during the period of record. The EC of Brown's#1 (water quality monitoring stopped in 2004 when the wellhead was vandalized)exhibits the greatest variability. Finally,samples retrieved from the Granite#3 well (sampling commenced in 2006)have EC values of about 1,000 pS/cm. Time series plots of major cation concentrations(sodium,calcium,and magnesium)and anion concentrations (bicarbonate,chloride,and sulfate)prepared for individual wells are in agreement with ' the EC measurements and exhibit stable hydrochemical groundwater conditions (Figures 12 to 16). Concentrations of major cations and anions were averaged over the period of record and plotted in milliequivalents per liter(meq/L). The plot shows that calcium,sodium, and bicarbonate are the most prevalent ions in both the shallow and deep zones (Figure 17). Shallow groundwater has greater chloride concentrations than deep groundwater and its hydrochemical facies is of Ca-NalHCO3-C1 type. Deep groundwater has greater sulfate concentrations than shallow groundwater and its hydrochemical facies is of Ca-Na/HCO3-SO4 type. Groundwater retrieved from the Granite#3 well has proportionally more sulfate and is of Ca-Na/SO4-HCO3 type. Nitrate(as nitrate)c tufa s ' shallow groundwater samples retrieved/fro well increased from a ut 15 30 mg between 1994 and 1996, decreased to bout 20 mg/L 'n 1999, and have remained rela ively s ince then with concentrations typically belo in the last few years (Fi ure 18). With the exception of the early monitoring record(1994-96),nitrate concentrations in z ell have typically been lower than in the Hall well,with a similar long-term trend. 1 he highest nitrate oncentrations(u to 50 mg/L were observed in samples retrieved from the South �. racy#1 well prio to commencement activities in,1997/98."Since the beginning of the m itoring re in 1994, concentrations have decreased to below 35 mg/L in 2008. Nitrate concentrations observed in the South Tracy#3 well are approximately 10 mg/L lower than in the South Tracy_#1 well,but show similar seasonal fluctuations(its record extends from 2004 to the present). During its period of record(1994-2001), nitrate concentrations in samples retrieved from the Brown's ' New well were stable, fluctuating between 6ar�d 11 mg/L, and concentrations in the Granite 43 well are similarly low. The greatest long-term variability and seasonal variability is exhibited by the Brown's #1 well. Nitrate concentrations initially increased from 12 to 30 mg/L in 1994, decreased to 12-16 mg/L in 1997-98,and since then increased to 48.5 mg/L(May 2004). The last nitrate concentration obtained from this well was 38.8 mg/L(December 2004). Since nitrate concentrations began increasing in 1999, seasonal fluctuations also increased. © LUHOOh FF G SGALMANINI C O N S U L- i N G ENGINEERS