2014-08-11_HYDROLOGY - M1977208 - Laserfiche WebLink

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CEM-005 is a difficult well to monitor. It is approximate 400 feet below grade and is screened at the Carlile-Fort Hays- Smokey Hills contacts. These formations have low permeability, porosity, and hydraulic conductivity. As a result,this well has historically been dry or has not had sufficient recharge after purging to collect a water sample for analysis. The May 15 and June 17,2014 samples are the first samples that have been attempted to be collected from this well. In May and June 2014,some water was present in the well and a due diligent effort was made by the field team to collect samples. Even though purge volumes were low and recharge volumes were very small,samples were collected and sent to the laboratory for analysis.' Unfortunately,it is not believed that this water was representative of the formation water, but was water that was pooled in the bottom of the well over the last quarter. To obtain sufficient sample volume,the field team reported that visibly turbid water was included in the May 15,2014 sample,which most like contributed to the high TDS results. As shown in the Stiff diagram in Figure 3,the high chloride content is associated with corresponding high sodium concentrations. A high concentration of sodium chloride in groundwater is typically attributable to three factors: road salting,saltwater(i.e.,sea water) intrusion, or naturally occurring salt within the formation. It is believed that sodium chloride is naturally occurring in this case.CEMEX has not salted the roads in the vicinity of the wells and there is no source of saltwater near CEM-005. Therefore, it is believed that the sodium chloride is naturally occurring. The presence of relatively high concentrations of sodium chloride is very similar to historical concentrations of sodium chloride observed in CEM-001. Like CEM-005,CEM-001 monitors groundwater at the Carlile-Fort Hays-Smokey Hills contacts. Figures 4 and 5 show historical Stiff diagrams for CEM-001 that illustrate a consistent high sodium chloride signature in 2014(Figure 4)and in 2007 (Figure 5)as documented in the TR-8(Brown and Caldwell,Technical Revision No.8. August 31, 2007). In an effort to obtain a more representative sample from CEM-005 to verify the chloride(and sodium)concentrations, the well was baled again on June 26, 2014 and monitored for recharge through June 30, 2014. However there was no sufficient water available to sample. ,t catcmm eicarba,ete n C403 caioum emamoate (a,CaCO3) (as C.0O3) Alagnesium Camonale IaPaSom Wgneshrm Carbonate Potassium • GlonEe Uavun . CND Polaswum ,� • ChWde $C(IIVm ---- a SuHate Sodom Sulata Figure 4. Stiff diagrams showing the cation-anion signatures for CEMr-001 for February, May,and June 2014(red). The signature is consistent with the signature obtained from the CEM-005 sample on May 15, 2014,shown in Figure 3. .r<:• ems• ;rrsa.s�az- 3:wt»•rat:ag' rrco r.x' Figure S. Stiff diagrams showing the CEM-001 cation-anion signatures for samples collected in March, May,June,and July 2007(Brown and Caldwell,Technical Revision No.8. August 31,2007). 1 Typically,groundwater is purged from a well prior to sampling. It is standard practice to remove a volume of groundwater equal to three well casings,or until field parameters stabilize(e.g.,temperature,pH,specific conductance,turbidity)then the well is allowed to recharge prior to sampling. This practice is designed to obtain a groundwater sample that is representative of the formation,rather than residual water that has been standing in the well and well sump. Standing water in a monitoring well is not representative of the formation. 3