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resulting in average TSS values <8. The finer fraction, which appears to contribute to most of the total metals concentrations, r still may be retained in the pond discharge. The retention of i! the fine fraction may be due, in part, to disturbance from the periodic underground mine discharge. The discharge probably reduces the .gravity settlement ,,efficiency of the pond, and turbulence would tend to keep fine material in suspension. Re- routing of the mine discharge to the Area 2 pit would provide surge control and minimize disturbance in Pond D. 5) The total metals concentrations in the pit overflow are predominantly related to the disposal of waste rock from the underground mining operation. This conclusion is based on two observations. Firstly, total zinc concentrations in samples taken from the oit prior to waste rock disposal were considera~b_ly lower th t resent en ro ~'~CZSmm~)-: Se o'er y~-if er quality ana yses from the Wedge sump and the Pond F Spring are taken as representative of groundwater which has infiltrated through backfill material, then this source does not make up a r large proportion of the pit overflow water since zinc aI7 ~,ls~s concentrations show ver different characteristics. Backfill water has a large proportion o o a zinc concentration in a dissolved state, whereas in it Ovate the zinc is almost entirely in a suspended state. Diss ed concentrations of zinc in backfill water are typically an orde of magnitude ~~gher than in pit water. ~~- ~..c Flo ~I~~ 6) The underground mine contributes up to 99% of the .total suspended solids entering Pond D. The primary source of the • W~~ ~ ,?total zinc load flowing into Pond D is the underground mine 11 ~~bfe,inflow, although the pit overflow does contribute a. large amount. FwQ°~7 The pit._overflow appears to be. the major source of..the total silver load, with the underground mine contributing a large proportion. 'The contribution of the underground mine may be _ significantly underestimated, particularly in the latter samples due to. the method of sampling, which allowed settlement of ~ suspended material. E - .. 7) It is likely that a large amount of fine suspended material resides in_the near-surface zone of the Area 2 Pit since gravity settlement is not very efficient at removing this fraction and _ the pit water is periodically disturbed by dumping of waste rock material. A series of samples taken at various depths in the pit would verify this hypothesis. If this proves to be correct then a baffling system which would minimize the overflow of near- surface water from the pit into Pond D should reduce the total zinc and silver loading. 8) A full e~=luation of the ambi>nt stream water quality monitoring data is not completed at this time, however it is apparent that existing data indicate that ambient ccncentrations of a number of parameters are significantly higher than current sream standards for Segment 13 of the Yampa River. An increase in the standard for parameters which are prese.ii:ly included (or