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of the irrigation system for this area in about 1910, these areas have been <br />intensively reworked for irrigated agriculture. Especially in the New Horizon <br />Mine 2 mining area, the surface water system is characterized by a <br />"disjointed" tributary drainage system almost completely controlled by return <br />flow ditches of the locai irrigation network. The perennial flow nature of <br />both Tuttle and Calamity Draws is largely due to the local irrigation <br />practices. Over the years this more or less constant source of water in these <br />drainage systems has encouraged the growth of vegetation. This has resulted <br />in the channels becoming more erosionally stable but more incised. <br />In the New Horizon Mine 1 area the Second Park Lateral Irrigation Ditch is in <br />continuous operation from mid-April through mid-Octoher. While this water is <br />primarily used for irrigation, important secondary uses include maintaining <br />water levels in stock ponds and domestic cisterns. During the non-irrigation <br />season the ditch is occasionally turned on to maintain the water levels in the <br />stock ponds and cisterns. <br />The flow in Tuttle Draw is primarily from irrigation return waters. <br />Occasional precipitation and snowmelt events contribute waters to this Draw. <br />Sediment Pond 001 discharges water to this drainage system regularly with <br />flows characterized by lows in April, averaging about 0.01 cfs, to highs in <br />September of 0.9 cfs. Sediment Pond 006 discharges significant flow to Tuttle <br />Draw beginning in May and continuing through August. Average flow for this <br />period is 0.4 cfs. In September discharges from Sediment Pond 006 rapidly <br />decline. In January through April the average discharge is insignificant. <br />This discharge has been monitored for ten years. These flows appear to be <br />greatly influenced by local irrigation practices. Impacts on water quality <br />from these ponds on Tuttle Draw are very limited due to the high dilution <br />ratios. These discharges occur upstream of surface water monitoring site <br />SW-N3. Measurements of water flow at SW-N3 show rates from 0.019 cfs to <br />9.35 cfs. Flows in Aprii 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 <br />upstream of SW-N3. Contributions from this source generally decline to near <br />zero during the non-irrigation period. These flows vary from 0.006 cfs during <br />April to 0.856 cfs in June. <br />Flows in Calamity Draw generally reflect local irrigation practices. Water <br />from the West Lateral Ditch's return irrigation flow is its primary source. <br />Very little supplemental flow is derived from precipitation and snowmelt <br />runoff. In 1987, measured flow rates in Calamity Draw varied from 0.605 cfs <br />in April to 13.4 cfs in July. Flow in Calamity Draw varied from 1.04 to <br />2.06 cfs during the non-irrigation period. Shallow ground water alluvial <br />sources provide a large portion of this low flow period's water. This ground <br />water flow is related to local irrigation practices but is consolidated into a <br />more uniform and regular flow by the permeabilities of these near surface <br />alluvial deposits. Sediment Pond 007 for the New Horizon Mine 2 mining site <br />will contribute water to the Calamity Draw system. The drainage system at the <br />New Horizon 2 site has been designed to provide adequate capacity and storage <br />times to completely control a 10-year 24-hour precipitation event. This <br />system will collect all runoff from the mine site and should actually lower <br />present total suspended solids (TSS) contribution from this area over the life <br />of the mine. Increased TOS levels in this water from mining disturbances are <br />expected but are projected to be within acceptable discharge levels and will <br />be mitigated by dilution. Regular monitoring of these flow rates and water <br />-6- <br />