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0 ARCADIS BBL <br />MEMO <br />To: Copies: <br />Jim Finley, Telesto Solutions Inc. Tom Kelley <br />From <br />Anne Thatcher <br />Date: ARCADIS BBL Project No.: <br />7-17-07 63521.0004 <br />Subject: <br />Avian Risk Due To Ingested Water At San Luis Mine <br />ARCADIS U.S., Inc. <br />14142 Denver West Parkway <br />Suite 350 <br />Golden <br />Colorado 80401 <br />Tel 303.231.9115 <br />Fax 303.231.9571 <br />Battle Mountain Resources, Inc. (BMRI) is proposing to use ground water pumped from the backfilled <br />West Pit at the San Luis Mine for irrigation at the Salazar Ranch. Ground water levels in the West Pit are <br />maintained at a constant level, which requires year round pumping. The irrigation season is typically from <br />April to October of each year. Thus, BMRI will need to store pumped ground water in ponds for a portion <br />of each year. As currently planned, two irrigation ponds will be constructed within the West Pit area for <br />purposes of storing irrigation water during the period November to March each year. <br />The objective of the screening level ecological risk assessment (SLERA) is to conservatively evaluate the <br />potential for adverse effects to the avian receptors through exposure to surface water constituents at the <br />San Luis Mine under current conditions. <br />SLERA Methodology <br />In the SLERA, a preliminary estimate of risk was conducted. To this end, a screening-level exposure and <br />toxicity assessment and a preliminary risk characterization will be performed. For the SLERA, USEPA <br />guidance (USEPA 1997) was followed by biasing the exposure toward conservatism (i.e., an <br />overestimation) of exposure and therefore, an overestimation of risk. This included using maximum water <br />concentrations as the exposure point concentrations (EPICS). Therefore, if the screen concludes that <br />p:Wr*cb&2124wmwd(sadds)lsmkiMpwManerdmnt-west pit man tlv5repat8pdfslappendocf-faunftffor=luisn9mmwoJuy17,2W.doe Page: <br />1/5