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The flow in Tuttle Draw is primarily from irrigation return waters. Occasional precipitation and <br /> snowmelt events contribute waters to this Draw. Sediment Pond 001 discharges water to this <br /> drainage system regularly with flows characterized by lows in April, averaging about 0.01 cfs, to <br /> highs in September of 0.9 cfs. Sediment Pond 006 discharges significant flow to Tuttle Draw <br /> beginning in May and continuing through August. Average flow for this period is 0.4 cfs. In <br /> September discharges from Sediment Pond 006 rapidly decline. In January through April the <br /> average discharge is insignificant. This discharge has been monitored for ten years. These flows <br /> appear to be greatly influenced by Local irrigation practices. Impacts on water quality from these <br /> ponds on Tuttle Draw are very limited due to the high dilution ratios. These discharges occur <br /> upstream of surface water monitoring site SW-N3. Measurements of water flow at SW-N3 show <br /> rates from 0.019 cfs to 9.35 cfs. Flows in April were measured at 0.665 cfs and at 9.35 cfs in <br /> September. The West Return Ditch is also tributary to Tuttle Draw just upstream of SW-N3. <br /> Contributions from this source generally decline to near zero during the non-irrigation period. These <br /> flows vary from 0.006 cfs during April to 0.856 cfs in June. <br /> The New Horizon !/line 2 site is just west of the town of Nucla and is located in the mildly sloping <br /> upland area of both Tuttle Draw and Calamity Draw, approximately in the middle of First Park. <br /> Especially in the New Horizon Mine 2 mining area, the surface water system is characterized by a <br /> "disjointed" tributary drainage system almost completely controlled by return flow ditches of the <br /> local irrigation network. <br /> West Lateral Irrigation Ditch - The West Lateral irrigation ditch is part of the Colorado Co-operative <br /> Company's main ditch system that originates on the San Miguel River just upstream of Cottonwood <br /> Canyon (about 12 miles upstream of Naturita). Construction of the main ditch commenced in 1896, <br /> and water began flowing to the First Park area via the ditch in the spring of 1904 (Mercer, 1967). <br /> The main ditch, as well as the main laterals, is basically an unlined open-channel excavated in <br /> shallow soils and sandstone. Where the ditch crosses drainages, pipes and aquaducts have been <br /> constructed to carry the flow. The main ditch has an average gravity run of four feet per mile from <br /> the San Miguel River to the First Park area(Mercer, 1967). For a more historical discussion on the <br /> Colorado Co-operative Company's development of the regional ditch system, the reader should refer <br /> to Section 2.04.3, Site Description and Land Use Information. <br /> The West Lateral splits off the main ditch near the northern boundary of the Nucla Townsite. The <br /> West Lateral follows a ridge-top course westward from Nucla through the New Horizon Mine 2 PR- <br /> 05 area to the main north-south county road, then winds south and southwest until the conveyed <br /> irrigation water is used by the various shareholders located along the ditch's course. A total of 18 <br /> diversions have been identified on this lateral; many consist of wooden "splitte boxes" that divert <br /> a consistent proportion of the irrigation water from the lateral to fields via small ditches and <br /> channels. Some diversions simply consist of pipes and hoses that also route irrigation water to <br /> slightly lower elevation fields. <br /> The West Lateral irrigation ditch is an unlined open channel. Where the ditch courses on the <br /> ridge-top separating Tuttle Draw to the north and the Calamity Draw Valley to the south, the ditch <br /> has been excavated through shallow soils into the highly fractured and weathered sandstone. Over <br /> 5 <br />