Laserfiche WebLink
WATER QUALITY E. aXATIONS AT STATION A72 ON THE AA.,,.AS RIVER USING <br /> CONTROL CHARTS <br /> Preliminary evaluations by WQCD and SGC have identified that the critical water- <br /> quality parameter at A72 is dissolved zinc (Zn). Attachment 1, printed from a <br /> spreadsheet file provided to Geochimica by WQCD, presents monitoring data for flow <br /> and Zn concentrations of samples at A72. To the data provided in the WQCD <br /> spreadsheet, Geochimica has added four data points, representing measurements at A72 <br /> in 1994 and 1995. These data also were provided by WQCD; a copy of the data sheet <br /> from which these measurements were taken accompanies Attachment 1. <br /> The approach set out below draws heavily on M.G. Natrella, 1966, Experimental <br /> Statistics: National Bureau of Standards Handbook 91, Chapter 18, "The Place of <br /> Control Charts in Experimental Work" (abbreviated as NBS91). Additional relevant <br /> material on control charts is found in Section 5.4 of J.R. Thompson, 1989, Empirical <br /> Model Building. New York: John Wiley , and in many standard texts on quality <br /> control, such as Chapter 3 of J.P. Dux, 1990, Handbook of Quality Assurance for the <br /> Analytical Chemistry Laboratory (2nd Ed.). New York: Van Nostrand. <br /> ISSUES <br /> 1. What constitutes "reference water quality" at a monitoring location, such as A72, <br /> that integrates surface water flow from upgradient, tributary streams? <br /> 2. How can one determine that water-quality samples obtained in the future at Station <br /> A72 represent the "reference water quality" of the Animas River at A72? <br /> 3. How could one determine the effects on water quality of reclamation activities in <br /> the Animas River basin above A72, compared to today's "reference water quality"? <br /> PROPOSED APPROACH <br /> Definition of "Reference Water Quality" <br /> 1. Water flowing past Station A72 represents the response of the Animas River Basin <br /> above A72 to meteorological, hydrologic, geologic and geochemical processes. <br /> 2. The water can be characterized by a set of variables. Two such variables that <br /> characterize river water at A72 are flow (Q) and concentration of zinc (Zn). <br /> 3. Sampling for flow and water quality constitutes a measurement process. <br /> 4. Measurements of flow and water quality in a river over time are considered to <br /> represent independent samples because subsequent states of the river system do not <br /> depend on results of previous sampling. <br /> Geochimica, Inc. 2 ANIMAS RIVER/9-Jun-95 <br />