2021-05-06_HYDROLOGY - M1977344

• Permit No: M1977344
• IBM Index Class Name: Hydrology
• Doc Date: 5/6/2021
• Doc Name: Water Monitoring - Groundwater
• From: Arcadis
• To: DRMS
• Email Name: TC1
• Email Name: MAC
• Media Type: D
• Archive: No

G:\COMMON\Holcim\25510\05 Correspondence\response to DRMS TR 10 review of Na letter\sueker revision 20141118\2014 1119 Response to TR 10 review letter .docx

Mr. Timothy A. Cazier
November 19, 2014
Page:
3/6
and sodium concentrations from the Portland plant and eight other Holcim plants in
the United States from 2005 and 2006. Potassium concentrations on average
exceed sodium concentrations by a factor of approximately 11. Sodium, potassium,
and chloride are all highly leachable constituents and behave conservatively in the
environment; that is, they are minimally affected by geochemical conditions in the
receiving groundwater (for example pH, redox, cation exchange capacity). It
therefore follows that concentration of these constituents in the groundwater, if
leakage from the landfill was occurring, should mimic the concentrations in the CKD
(thus, potassium concentrations should greatly exceed sodium concentrations).
Based on several years of groundwater monitoring data from the site this is not the
case. While chloride is not part of the GMP, previous analyses of chloride suggest
the same conclusion. Table 3 presents some historical chloride, potassium , and
sodium concentrations in MW -7 between 1998 and 2009. Chloride concentrations
ranged from approximately 25 to 42 mg/L during that time period, compared to 7 to
17 mg/L for potassium in that well over the same time frame, and 112 to 236 mg/L for
sodium. If these concentrations were a result of leaching from the CKD, potassium
and chloride concentrations should be much higher than sodium concentrations
rather than the opposite. These conclusions are illustrated with graphs of
groundwater sodium concentrations versus K:Na and Cl:Na values for groundwater
samples (Figure 3). As shown in Figure 3, groundwater K:Na values are below 0.25
and Cl/Na values are below 0.3, both of which are more than an order of magnitude
below the K:Na >10 and Cl:Na >20 values expected for CKD and CKD leachate.
CKD leachate testing data also suggests that the landfill is not the source of sodium
in groundwater at MW -7. Table 4 is a summary of Synthetic Precipitation Leaching
Procedure (SPLP) test data for CKD and alkali bypass dust generated from the
Portland plant, from 2002 and 1999. While the data set is limited, the results of both
tests show that the concentrations of sodium (158 and 159 mg/L) are less than the
recent and historical concentrations of sodium in groundwater at MW -7. Based on
these results it is not feasible that releases from the landfill could be the cause of the
increasing sodium concentrations in groundwater at MW -7. Furthermore, the
elevated chloride concentration in the alkali bypass dust from the SPLP test (4,600
mg/L) relative to the sodium concentration (158 mg/L) results in a Cl:Na value of 29,
generally consistent with the chloride to sodium ratio values greater than 20 in the
CKD composition analysis results (Table 1).
Groundwater data were evaluated further to better understand the potential cause of
increasing sodium concentrations at MW -7. Figure 4 demonstrates little relation
between sodium and sulfate concentrations for groundwater monitoring locations
with the exception of MW -7, which shows a strong inverse relation between sodium
and sulfate concentrations. These results suggest that water with different