Laserfiche WebLink
<br /> <br /> <br />6-1 <br />DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this docu ment. <br />Section 6 <br />Interpretation of Results <br />Many naturally occurring factors can affect surface and groundwater quality. The primary influences <br />affecting groundwater include the source and chemical composition of the recharge water, the <br />geological and mineralogical properties of the water bearing unit, chemical processes occurring <br />along the groundwater flow path, and the amount of time the water has remained in contact with the <br />geologic unit (residence time). Surface water quality can be affected by the source of the water <br />(groundwater or precipitation), interactions with surface sediments or exposed lithologies, biological <br />processes, and evaporation. All of these factors can affect the type and quantities of dissolved <br />constituents in surface and groundwater sources. <br />Water quality data were evaluated to identify potential interactions between the surface water and <br />groundwater systems at the Site. Geochemical plots were generated to compare major ions <br />chemistry spatially and temporally. Plots of key water quality parameters with time were generated to <br />identify trends between surface and groundwater quality. <br />6.1 Major Ion Water Chemistry <br />The most abundant dissolved constituents measured in water are major ions including cations <br />calcium (Ca2+), magnesium (Mg2+), sodium (Na+), and potassium (K+); and anions bicarbonate <br />(HCO3-), chloride (Cl-), and sulfate (SO42-). Measuring the concentrations of the major ions can provide <br />information on the chemical quality of the water and the processes that may be occurring. <br />Piper diagrams are a graphical representation of the chemistry of water samples (Piper 1944). Water <br />quality data concentrations were converted from milligrams per liter (mg/L ) to milliequivalents per <br />liter (meq/L) based on the valence (charge) and atomic weight of the ion. The relative percentage of <br />each ion are calculated (% meq/L) then plotted on the diagram. The cations and anions are shown <br />by separate ternary plots. The apexes of the cation plot are calcium, magnesium, sodium, and <br />potassium. The apexes of the anion plot are sulfate, chloride, and bicarbonate, and carbonate. The <br />two ternary plots are then projected onto a diamond. Piper diagram divides water into four basic <br />types according to their placement near the four corners of the diamond. Piper diagrams can be <br />used to determine if water quality data have a similar origin by plotting several samples onto one <br />diagram. Piper diagrams can also be used to evaluate the evolution of water samples to indicate <br />mixing of more than one water source, ion exchange, or dilution. <br />The Piper diagrams of the groundwater data indicate slight differences in the water chemistry of the <br />Codell Sandstone. Groundwater data for Well 1 and Well 3 plot in the calcium-sulfate type and Well 4 <br />data plot in the sodium-chloride type (Figure 6-1). Surface water quality data are in both the calcium- <br />sulfate and sodium-chloride type (Figure 6-2). Surface water data from location SW RC2 also has a <br />wider spread in water quality data while the data from the other surface water quality locations <br />cluster together. Plotting all of the data on one Piper diagram shows that the surface water quality <br />mostly falls within the range of the groundwater data with the exception of chloride and one surface <br />water samples collected from SW RC2 during the March 2023 sampling event (Figure 6-3).