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dominated waters to sodium-chloride and sulfate dominated waters. Other parameters that tend to <br />increase as the Arkansas River flows east of Pueblo are stream temperature, nitrite (NOA nitrate <br />(NOA and suspended solids (Cain 1984). These parameters are associated with the municipal and <br />industrial wastewater discharges, (which have the greatest impact water quality immediately east <br />of Pueblo), and agricultural activities within the basin (Cain 1984). <br />Lewis and Brendle (1998) sampled three locations between Pueblo Reservoir and the John Martin <br />Reservoir near Las Animas and found that streamflow and specific conductance were primarily <br />affected by Pueblo Reservoir operations. The mixing of seasonally high and low conductance <br />waters was found to narrow the annual range of specific conductance values by increasing and <br />decreasing the dilution potential of the river (Lewis and Brendle 1998). The Pueblo Reservoir <br />regulates Streamflow in the Upper Arkansas. <br />Historical data indicate that degradation of surface water quality has likely occurred in the area <br />related to irrigation return flows, municipal and industrial discharges, and surface water <br />impoundments. Water quality data have been collected by the USGS from three stream gaging <br />stations located in the vicinity of the mine identified on Figure H-1. These stations are located <br />downstream from the mine on the Saint Charles River and upstream and downstream of the <br />confluence of the Saint Charles River with the Arkansas River. Data from these stations were <br />reviewed to assess existing water quality in the watershed. <br />Gaging stations are located on the Saint Charles River at Vineland (07108900), and on the <br />Arkansas River at Moffat Street in Pueblo (07099970) and at Avondale (07109500). Table 1 <br />indicates the average annual and peak flow discharge at the identified gaging stations. Table 2 <br />presents mean values (where available) collected at the gaging stations for parameters of concern <br />. relevant to the proposed mining operations. These values are indicative of the water quality <br />upstream of the mine site on the Arkansas River and downstream of the mining operations on <br />both the Arkansas River and the St. Charles River where any impacts would be realized. The two <br />gaging stations on the Arkansas River are included in segment la of the Lower Arkansas River <br />Basin within Region 7 and have the same designated uses but have varying water quality <br />standards as compared with segment 6 of the Saint Charles River (CDPHE 2002). <br />• <br />7