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Response 1985 AHR <br />Page 3 <br />Comparison of Detection Limits and Receiving Steam Standards. <br />Element <br />Detection Limit <br />Receiving Stream <br />Standard <br />Mercury <br />Cadmium <br />Molybdenum <br />Copper <br />Response: <br />0.0005 <br />0.005 <br />0.05 <br />0.02 <br />0.00005 <br />0.001 <br />0.01 <br />0.01 <br />In reference to mercury, the receiving stream standard is below the existing <br />detection limit for this element. The Colorado Department of Health; Water <br />Quality Laboratory indicates that 0.25 ug/1 is the lowest reportable <br />concentration using an AA, cold vapor method. TCC's lab will use USGS 1-2460- <br />78 automated cold vapor method to provide a future detection limit of 0.2 <br />ug/l. In reference the other parameters TCC will advise the lab to utilize <br />low level detection methodologies so that the detection limit meets the stream <br />standard. <br />MLRD Comment: <br />Well 006-81-31 has much higher salt levels than other Wadge overburden sites. <br />Has this well been examined to ascertain that it was completed properly? Do <br />you have any other explanations for the high salt concentrations? <br />Is well 006-81-30 an artesian well? The remarks column annotates the failure <br />to provide depth data with the comment "flowing". Please elaborate. <br />Response: <br />The reported results do not appear to be representative and TCC will <br />investigate the situation and advise the MLRD of the findings. Well 006-81-30 <br />is a flowing artesian well. <br />MLRD Comment: <br />The Foidel Creek alluvial wells do not show any definite effects from mining <br />from the hydrographs presented. However, future hydrographs should have an <br />expanded abscissa of 20 feet rather than 35 feet. It is expected that water <br />levels should rise in late summer with Foidel Creek's transition from an <br />ephemeral to a perennial stream. Salt concentrations in the aquifer declined <br />during the last two years at the downstream site, but increased at the two <br />upstream sites. <br />