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_lq_ The watershed proposed for location of the new refuse site is underlain by the Raton and Poison Canyon Formations. The strata dip into the slope of the watershed. The watershed is on a south facing slope with surface water flowing only in response to rainfall or snowmelt. Snow does not remain in the watershed for long periods due to the southerly exposure. No springs or seeps have been identified in the watershed. A trench was dug at the refuse disposal site and no ground water was encountered to a depth of 9.2 feet. Due to the above described conditions it is not expected that any ground water will contact the refuse pile. Infiltration of snow and rainfall through the surface of the pile will be negligible due to compaction of the refuse during placement. An underdrain will be installed by the operator. This drain should route most seepage that does occur into the surface drainage system and to the sediment pond. The channel of the Middle Fork of the Purgatoire River will be relocated around the proposed preparation plant. The present channel will be filled. The existing channel and proposed relocation both lie in an area that has been previously disturbed by placement of breaker refuse on the river floodplain. This refuse was placed directly on alluvial fill material. The waste piles were in existence prior to the enactment of the Colorado Mined Land Reclamation Act, C.R.S., as amended. Further discussion of this area can be found in Section VIII, Alluvial Valley floors of this document and in Section VIII of the original findings document. The operator has submitted a leachate study simulating quality of water seeping through the refuse in the flood plain. This study can 6e found in Section III, Part 4 of the permit revision application. This study was designed to specifically predict water quality dimunition which could occur by use of old refuse as fill material and direct placement of this old refuse in the existing channel. This study predicted impacts by accounting only for infiltration through the upstream head of the fill. These results showed insignificant impact to the surface water system. The Division studied the results of infiltration not only from the upstream head of the stream fill but also along the 800 foot sides of the filled channel. This would more accurately depict worst case conditions. This simulation showed more significant impacts to the surface water system but below levels that would affect usability of the surface water for irrigation. The operator has subsequently committed to an underdrain of 3 foot thickness It will be composed of cobble and gravel material previously dredged from the river bottom upstream of the area proposed for relocation. This underdrain will greatly diminish the possibility far alluvial ground water contact with the refuse material. The operator has also committed to compaction of the overlying refuse material to 90% of in place density. In order to assure the long-term operation of the underdrain, a granular filter should be placed to prevent fines in the refuse from filtering through and clogging the underdrain. The operator has not committed to the granular filter. Therefore, the following stipulation is needed.