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I~ Memo to Harry Posey -2- January 24. 1997 dump compared to the increase in metals concentration that may be caused by the change in geology of the stream bed and gulch walls. It should also be noted that there are differences other than geology between upper Windy Gulch, where the background samples were collected, and lower windy Gulch, where the ostensive source samples were collected. Above the background sampling location, Windy Gulch flows through well vegetated grassy meadows and woodlands at a relatively shallow gradient. Below the location where the background sample was collected, Windy Gulch enters a sparsely vegetated canyon dominated by talus slopes and steep gradients. Surface water sample SW-16 and steam sediment sample 5E-16 were collected just above the confluence of Windy Gulch and Willow Creek. This sampling site is located approximately 3000 feet southeast of the Bulldog Mine 9360' portal, and is approximately 450' lower in elevation. SW-16 and 5E-16 are much higher in metals than SW-15 and 5E-15. I do not believe that the higher metals concentrations can be attributed solely to the presence of the 9360' mine dump, in fact, 2 suspect that the 9360' dump is only a minor contributor of metals to Windy Gulch at this time, for the following reasons: 1. Windy Gulch is passed through a long 30" culvert with an intake above the 9360' dump and an outlet approximately 30' above the downstream margin of. the dump, thus the dump is largely isolated from the stream. This could change in the future if the culvert becomes plugged, so the Bulldog Mine reclamation plan called for Homestake to construct an.overflow channel capable of non-erosively passing the 100 year flood in Windy Gulch. As far as I know, the culvert under the dump is still fully operable, and there has never been flow in the overflow channel up to this time. 2. Part of the Windy Gulch overflow channel is constructed through mine waste; the mine waste was sampled and subjected to acid-base accounting with the results showing a 5:1 ratio of neutralizing potential to acid generating potential based on pyritic sulfur. Also, the mine waste exposed in the overflow channel was plated with native talus borrowed from a location near the 9700' portal. The Division required that only durable, non-altered and non-mineralized talus be utilized in the construction. 3. Windy Gulch is an ephemeral stream, and the 9360' dump is above the ground water table. No seepage has been observed issuing from the dump during site inspections by the Division of Minerals and Geology. More likely contributors to the metals loading in lower Windy Gulch