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~~. ~1. III IIIIIIIIIIIIIIII <br />(„~l~, ,~- ti~~ - ~~ ¢ 999 <br />~~ - ~.e Pmt V` ~-Y- ~,~. ~:~ . <br />INTERNAL MEMO ~~ <br />DATE: April 14, 1997 <br />TO: Jim Stevens <br />FROM: Harry Posey <br />RE: HCI Reports: Cresson Operation <br />The following memo addresses what I feel are shortcomings in the <br />HCI documents regarding discharge from the Carlton Tunnel at <br />Cresson. This memo does not address completely the potential <br />surface water quality problems in either Arequa Gulch or Squaw <br />Gulch. These will be covered in later work. <br />In reviewing these reports, I compared the modeling results or <br />other data provided with surface water quality standards for Four <br />Mile Creek. I also compared the results with ambient groundwater <br />conditions (insofar as I had data) and with drinking water <br />standards. The latter paragraph appeals for more discharge data <br />from either the Carlton or the Roosevelt Tunnel in order to make a <br />more complete assessment. <br />Basically, I have two findings. <br />a. The model inputs for acid rock drainage potential appear to <br />underestimate the surface (3-dimensional) and areal dimensions <br />of acid generating material. <br />b. The models do not predict the Zn (or other metal) discharge <br />values due to insufficient data. <br />I. BACKGROUND <br />HCI has produced two modeling studies for CC&V. These are referred <br />to as HCI (1993) and HCI (1994). <br />The HCI (1993) report includes PHREEQE modeling which predicts the <br />pH of a mixture of acid solution from pyritic waste rock and the <br />current (1992) Carlton Tunnel water. This report purports to show <br />that the resultant pH will meet water quality standards. I <br />disagree both with some of the input assumptions, and with the <br />interpretation of some of the results. I do agree however with <br />some of the results. <br />