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Final April 2009 <br />Groundwater <br />ARCADIS Monitoring Report <br />I Florence. California <br />MW-7. No other analytes measured at MW-7 exceeded the compliance standards, <br />human health standards, secondary drinking water standards or agricultural standards. <br />Per the requirements of the DRMS-approved GMP, if the results of two or more of the <br />selected analytes used for compliance (TDS, sulfate, potassium, sodium, iron, and <br />manganese) exceed their respective compliance values by more than 10% in <br />monitoring well MW-7, Holcim is required to modify the sampling frequency from <br />annual to semi-annual in this well. Sodium was the only parameter that exceeded its <br />compliance value. Furthermore, the sodium concentration of 236 mg/L is only 4% <br />` greater than the compliance value of 226 mg/L. Therefore, the sampling frequency for <br />w this well can remain annual. <br />Concentrations of metals and other constituents measured in groundwater at wells <br />MW-12 and MW-13 were compared to applicable CDPHE groundwater quality <br />standards (CDPHE 2008). Where multiple standards exist for a single constituent, the <br />most stringent standard was used. Aluminum, manganese and sulfate exceeded their <br />respective agricultural standards for groundwater at both of the groundwater <br />monitoring wells. Aluminum exceeded the agricultural standard for groundwater of 5 <br />mg/L at wells MW-12 and MW-13. Manganese exceeded the secondary drinking water <br />standard for domestic water supply of 0.05 mg/L at wells MW-12 and MW-13. Sulfate <br />exceeded the secondary drinking water standard for domestic water supply of 250 <br />mg/L at wells MW-12 and MW-13. Additionally, fluoride exceeded the agricultural <br />standard for groundwater of 2 mg/L at well MW-12 and selenium exceeded the <br />agricultural standard for groundwater of 0.02 mg/L at well MW-13. No other analytes <br />exceeded the human health standards, secondary drinking water standards or <br />agricultural standards. <br />Time series graphs of TDS, sulfate and manganese for MW-7 and MW-12 were <br />prepared (Figures 3, 4 and 5) to evaluate potential impacts of CKD disposal to the <br />groundwater. In addition, the potassium sodium ratio (K:Na) was plotted for these <br />same wells (Figure 6). The K:Na is a useful diagnostic tool in determining CKD impact. <br />Generally a K:Na value of greater than 0.5 is indicative of impact from CKD. The <br />graphs indicate that TDS and sulfate concentrations in MW-7 are continuing to <br />decrease through time. TDS and sulfate concentrations in MW-12 have remained <br />similar to the previous year's concentrations. In general, manganese concentrations in <br />MW-7 and MW-12 have continued to decrease since 2000. The concentrations found <br />in monitoring well MW-12, which is considered the background well, from the April <br />2009 sampling event (Table 2 and Figures 3, 4 and 5) are as high as or higher than the <br /> <br />cAdocuments and settingststobgy\rny documents\holcim1025911978_holcimreg version_final.docx <br />8