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Discharge from the Terry Tunnel is highly variable and is dependent upon surface water inflow <br /> to mine workings from precipitation and snowmelt. Monitoring and treatment of the Terry <br /> Tunnel effluent is only conducted from late spring to early fall because the tunnel portal is <br /> inaccessible during the winter. Discharge from the Terry Tunnel is typically low during the <br /> winter months. Treatment consists of lime addition between the portal and the first of two <br /> sedimentation ponds. Pond No. 1 has been lined with recompacted fines. An "H" flume has been <br /> installed below Pond No. 2 for flow rate measurements. The NPDES discharge requirements <br /> for the Terry Tunnel effluent are less stringent than for the American Tunnel. <br /> 4.3 Present Surface-Water Hydrology <br /> 4.3.1 Surface-Water Flow <br /> The measured flow rate (1987-1991) of the North Fork of Cement Creek just above Gladstone <br /> ranges between 15.7 mgd at the end of May to 0.23 ingd at the end of October (see Appendix <br /> Q. Just below Gladstone this Oow is augmented by the flow of the South Fork of Cement <br /> Creek which is not measured, nd by the flow from the American Tunnel portal which is <br /> approximately 3.1 mgd (measur October 2-3, 1991). <br /> 7 <br /> The measured flow (1987-1991) 01 f Eureka Creek above the Terry Tunnel portal varies from 5.2 <br /> mgd at the end of May to 0.05 mgd at the end of October. This flow is augmented by flow <br /> from the Terry Tunnel which ranges from 2.0 mgd in early June to 0.12 mgd in late October. <br /> The flow in Eureka Creek is also augmented by flow from McCarty Basin and downstream <br /> tributaries. <br /> sanjuan\suns)\110361\oct9I.Rpt 49 <br /> a simon Lni n=mnunou <br />