2012-12-21_HYDROLOGY - M1977344 - Laserfiche WebLink

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ARCADIS Per the GMP, an explanation and a proposed remedial action are required when an upward trend continues. Based on the September 2012 sampling results the concentrations of sodium and total iron in MW -7 remain greater than the compliance value. Historically concentrations of sodium and total iron in MW -7 have fluctuated in groundwater samples but remain on the same order of magnitude. Although sodium concentrations exceed the compliance value, the potassium to sodium ratio (K:Na) is a more useful diagnostic tool in determining CKD impact than sodium concentrations. The basis for this is well documented in the "EPA Report to Congress on Cement Kiln Dust Waste ", published in 1993 (RTC). Based on the data presented in the RTC, the K:Na ratio in bulk CKD samples ranges from approximately 3 to 8 in dry kilns and 2 to 3 in wet kilns. As such, it is likely that an elevated K:Na concentration ratio would be present in groundwater in cases where CKD has leached to groundwater. The groundwater case studies presented in the RTC confirm that this is the case. Generally a K:Na value of greater than 0.5 is indicative of impact from CKD. Including the September 2012 results, the K:Na in MW -7 has been less than 0.16 with an overall decreasing trend (see attached Figure 3), indicating that there is no discernable impact from CKD. The cause of the increasing sodium concentration is not known, but this trend is not caused by the CKD landfill. With regard to iron concentrations, ARCADIS recommends that Holcim request the DRMS reevaluate the MW -7 compliance standard for iron since 4.5 mg /L is more likely a total value than a dissolved value. However, this was not defined in the GMP. The recently issued DRMS MW -13 compliance standard of 0.13 mg /L is for dissolved iron. The dissolved iron concentration in well MW -7 is 0.09 mg /L (see Attachment 3).Although well redevelopment has improved the recharge in MW -7, field records show that the turbidity remains high in the groundwater. Total suspended solids from the formation adjacent to the well screen at MW -7 are likely causing the total iron results. As such, dissolved iron is a more appropriate standard. ARCADIS recommends continuing semi - annual sampling of MW -7 to determine whether the K:Na concentration ratio approaches 0.5. If so, further investigation into the cause of the increase should be completed. If the sodium concentration stabilizes or decreases, then we recommend reducing the sampling frequency back to annual and requesting a change in the criterion. Furthermore, ARCADIS recommends that the compliance value for iron be modified to dissolved iron, and that DRMS reset the value based on the available data. C Users I>usko Documents Hol cull 2012 MW -7 Redexelop Summary Letter 2012 1217 Holcim Portland Well De, Samplme Summary Letter doc Mr. Justin Andrews December 17, 2012 Page: 4/5