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Section 13 <br />Geochemical Data and Analysis <br />infiltrates into the pile may be subsequently removed from the pile by evaporation or <br />transpiration or the water may move downward in the pile and become percolation. <br />Empirical information such as temperature and precipitation data and development <br />rock characteristics are used for the water balance evaluation. The procedure included <br />the following activities: <br />¦ Compile temperature and precipitation data from a location as close as possible to <br />the site; <br />¦ Estimate runoff and evapotranspiration (ET) for the rock pile; <br />¦ Estimate moisture holding capacity of development rock based on site specific <br />capillary moisture data obtained from soil water characteristic curve (SWCC) <br />testing; and <br />¦ Estimate percolation through the development rock pile using a water balance <br />approach. <br />Details of the estimation method are included in Attachment O of this report. <br />Development rock samples were collected for physical property analyses including <br />soil water characteristic curve (SWCC) testing. Geotechnical laboratory data for the <br />development rock samples, including SWCC testing data, are also provided in <br />Attachment O. Exhibit 13-1 presents the results of monthly percolation estimates for <br />an average precipitation year. <br />Exhibit 13-1. Estimated percolation through development rock areas for average precipitation. <br />Month Potential <br />ET (in.) Precipitation <br />in.) Actual <br />ET (in.) Runoff <br />(in.) Infiltration <br />(in.) Percolation <br />(in.) <br />October 3.36 1.51 1.36 0.15 1.36 0.00 <br />November 2.19 1.05 0.95 0.11 0.95 0.00 <br />December 0.48 0.85 0.48 0.09 0.77 0.00 <br />January 0.47 0.88 0.47 0.09 0.79 0.00 <br />February 1.94 0.76 1.30 0.08 0.69 0.00 <br />March 2.93 1.04 0.94 0.10 0.94 0.00 <br />April 3.70 1.01 0.91 0.10 0.91 0.00 <br />May 4.93 0.94 0.84 0.09 0.84 0.00 <br />June 5.72 0.47 0.43 0.05 0.43 0.00 <br />Jul 6.34 1.18 1.06 0.12 1.06 0.00 <br />August 5.74 1.35 1.22 0.14 1.22 0.00 <br />September 4.43 1.50 1.35 0.15 1.35 0.00 <br />Annual Total 42.33 12.55 11.29 1.25 11.29 0.00 <br />The estimate summarized in Exhibit 13-1 indicates that potential ET at the Sunday <br />Mines Group exceeds average precipitation by a ratio of approximately 3.4 to 1. <br />Under average conditions, available ET is adequate to evaporate water infiltrating the <br />surface of the rock piles. A temporary increase in stored soil moisture would occur <br />during the months of January and February, but this water would be removed from <br />13-6 <br />T:184986-13enison Mines\Task Order 4 - EPP Sunday Mines GroupT INAL EPPTINAL - Environmental Protection Plan Sunday Mines.doc