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West Elk Mine term increase would have no effect on the crops. The 500 mg/L level at which there may be • limited restrictions for irrigation is applicable to the average concentration of the source irrigation water. The instantaneous concentration of the source water can exceed 500 mg/L without adverse impact to irrigated crops. The more relevant analysis is to consider the annual salinity loading to the North Fork, which is presented in the CHIA, and remains valid. To protect agricultural and municipal uses in the lower Colorado River Basin, Colorado participates in the multi-state, basin-wide approach for managing salinity (TDS) in the Colorado River. There are no Colorado stream standards for TDS based on stream classifications. TDS is controlled to maintain the following flow-weighted annual values for TDS: Below Hoover Dam: 723 mg/L; below Pazker Dam: 747 mg/L; at Imperial Dam: 879 mg/L. The Colorado regulation recognized that periodic increases above the criteria are in conformance with the standazds, provided that, when conditions return to normal, concentrations aze expected to be at or below the criteria level. The normal range for TDS in irrigation water is between 0 to 2,000 mg/L. Continued and prolonged imgation with water having a TDS concentration between 500 mg/L and 2,000 mg/L may impose slight to moderate requirements for management practices (leaching and drainage) or crop selection (use of less sensitive crops) in order to avoid crop yield reductions. Because crops are affected only when TDS in root-zone water builds up to excessive levels, occasional excursions of TDS in irrigation water above 500 mg/L are generally not significant, as long as the average annual value is lower. Dr. Robert Weiner of WWE has evaluated the concentrations of the individual constituents which collectively constitute TDS in mine discharges. Dr. Weiner has determined that the pond dischazge water is predominantly sodium carbonate/sodium bicazbonate in nature. Aside from high concentrations of sodium, none of the other parameters, including the heavy metals, aze found in significant concentrations. As for sodium, there are no applicable numeric standards or criteria. Elevated sodium levels can have negative implications for irrigated soils that are clayey in nature. This is because high sodium can cause such soils to "seal." The sodium adsorption ratio Table 55 Re resentative TDS Standards/Criteria TDS Standards or Criteria TDS (m /L) Seconds Drinkin Water Stantlard 500 <450: None Restrictions for Irrigation 450-2,000: Slight to Moderate >2,000: Severe Restrictions for Livestock <1,000: None 1 000 - 3 000: None for Acclimated Livestock Restrictions for Recreation No restrictions High TDS can cause deposits in heat exchangers and Restrictions for Industrial Use boilers. (Ambient North Fork water would require treatment . A vatic Life No TDS standards 2.05-199 Revised November 1004 PRIO