2019-03-11_REPORT - C2009087 (2)

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Ground Water Quality. Ground water samples were collected from 7 wells on an annual or biannual basis. The parameter lists used for all wells sampled this year are given on Table 4 (Ground Water Long Parameter List) and Table 4A (Ground Water Short Parameter List). All laboratory analyses since May 3, 1983 has been performed by ACZ Laboratory (ACZ) in Steamboat Springs, Colorado. ACZ performs all analyses by EPA or equivalent methods. Samples are delivered the day of collection to the lab in an iced cooler. The PSCM ground water monitoring program may be found on Table 2.04.7-T9, page 2.04-104 (Vol. 1) of the PSCM PAP. The following discussion of the analytical data collected during the reporting period is arranged by strata being monitored and coincides with the format (by aquifer type) in which the analytical data are presented in Appendix C. The discussion of water quality will be limited to a description of total dissolved solids (TDS) concentrations. A separate section, Comparison of Ground Water Quality to Water Use Standards, will discuss any samples that exceed water use standards. Data for each well begins with a listing of the water quality data collected during the past two years, followed by remarks explaining the sampling procedure. This is followed by a plot of TDS versus time for the entire period of record. The regression line on this plot is generated by a method known as Locally Weighted Scatter Plot Smoothing (LOWESS) (Cleveland, 1979). Unless otherwise noted, a smoothness factor (SF) of 1.0 (on a scale of 0 to 1) was used, which results in maximum "smoothing". Alluvium. In the Cow Camp Creek alluvium (below NPDES 004 Pond), water quality is measured at one well. Well 69 displays an overall decreasing TDS trend, however the past eight years of data exhibit a slight increase in concentration.