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<br />pr<l.ctice provided a backup sample in ca<>e of freezer failure or shipmcnl loss. In the singlc case <br />of Michigan Cn.--ck the backup sample was later shipped to DRI for analysis. It yielded 46.0 ppl. <br />still a high value but well bdov. the 112.5 ppt of the original. The reason for this difference is <br />unknown. However. Dr. Joe McConnell (personal communication) of DRI cautioned lhat \\ith <br />such low concentrations a very liny volume v.ith enhanced Ag could sharply incn.:asc thc total <br />sample concentration. This phenomenon is called the "nugget effect." Dr. McConnell is familar <br />with the South Park area and nearby mountains. i Ie raised the possibilit}- of some contamination <br />by wind-blown dust at Michigan Cn.'Ck in view of knov.n high silver concentrations in the <br />vicinity. In the abSt."t1cc of more definitive information. the two Michigan Creek samples are <br />simply averaged to 79 ppt. <br /> <br />The samL' n:sults arc shown in FigufC I. a generalized topographical map showing Agl <br />generdlor and silvcr-in.sno\.... sampling locations. Nine of the ten target sitL'S \\l;:'fC choscn b) <br />Western Weather Consultants. thc seeding contractor. as likely to be impacted by seeding. The <br />Sundance location. with one of the higher Ag values at 11.9 ppt. "as sclccted by the authors to <br />provide better spatial coverage of the main target area. <br /> <br />The intended target area boundaries (not sho"n) approximatcly followed the 10.000 ft <br />contour around the region containing the ten target sampling sites. The only Agl generators well <br />within the target. starting from the north. wen: numbers 35 (at onl) 8-140 ft). 33. 39. ~O and 41. <br />Gencrator numbers either just inside or outside the target boundary. going around the valley <br />containing gencr<l.tors 31. 32. 34 and 37. were numbers 30. 38. 36. 28. and 27. GcneratofS 1. 8 <br />and 12 were near the southern target boundar:... which again followed the 10.000 ft contour. <br />Ob\"iou.<;ly all targct snow-sampling locations \\erc within thc target. Somc extensions of the <br />target area wcre not sampled for Ag lx."(;au~ of limited access. Thesc includcd the higher terrain <br />extcnding south of the 1\tO most southern snow sampling locations (Frcemont Pass and Hoosier <br />Pass) to well beyond the southern boundary of Figun:: 1. the mountains extending southeast of the <br />Sundan~ snow course. and the region between Vail Mountain and generator 30. The <br />northeastern-most extent of the target was less than 10 miles northeast of the" Arrow SNOTEL. <br /> <br />Section 2. which was written before the DRI silvcr-in-snow analysis. noted that Ag <br />concentrations near or less than 10 ppt are unlikely to be associated ....ith meaningful Sl..~-ding- <br />caused snowfafl augmentation. The conclusion for that section statl.-d that. "Sl.'3..wnal samples <br />\\ith les.s than 10 ppt silver can be interpreted as evidencc of poor targeting \\ith little resulting <br />snowfall augmentation. A routinely targcted ope-rational project should produce at least the 30-100 <br />ppt values observed in the randomized BRE." One of the ten targct stations (Michigan Creek) met <br />that criterion. with about 79 ppl. although two additional sitl..."S may have lx'Cn atTectoo minimally by <br />seeding. <br /> <br />IQ <br />