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as water does not floe upgradient, monitoring at the loadout is tied to water uses or use • <br />potentials adjacent to [he loadout and downstream or doungradient where there is hydraulic <br />communication potential. Up- versus downgradien[ monitors in the alluvium and stream are <br />nice conceptually, but offer no additional interpretive insight if there are <br />heterogeneities in the hydrologic units or components being compared. this is the case at <br />the loadout. Both the alluvium and streamf low are heterogeneous spatially as a result of <br />lithologic changes, irrigation floes, and dryl and farming and Lewis shale seeps and flows. <br />thus, downgratlien[ monitors are more than adequate for assessing impact trends. <br />The impact assessment methodology will employ Mann-Kendall non parametric [fend tests <br />(Kendall, 1975) and sen slope plots (Gilbert, 1987). Mon-parametric statistical analyses <br />will be used because eater quality data typically is not normally distributed and [he <br />non parametric tests are more resistant [o the effects of outliers. The analyses will <br />focus on detecting persistent degradational trends. Impacts associated with irrigation <br />floes and dryland farming floes or seeps should be seasonal in nature (exhibits some <br />parameter concentration oscillations) but should not shoo persistent worsening. The coal <br />stockpile and sanitary usage is year round and one should expect to see persistent <br />degradational changes if impacts are truly being caused by the loadout. <br />• <br />Impact significance is linked to rater uses and use potential. One cannot degrade a rater <br />source [ha[ is already degraded [o the point [here is no use utility. this is the case of <br />the alluvial aquifer opposite and immediately doungradient of the loadout. Stream eater <br />quality at and dornstream of [he loadout does have a rater use potential (marginal at <br />times) and the use potential is livestock drinking water. The trentl analysis technique <br />will totes on analyzing parameter data sets rhere there is very limited or no censoring <br />(less than detection limit) and particularly those parameCers far rh ich there are <br />, TDS, Cl, antl B). If persistent degradational impacts are <br />livestock standards (i.e., sO <br />G <br />determined, the impact significance shall be assessed based on the magnitude of change <br />adjacent to the loadout and the potential downstream extent of the measurable degradation <br />(i.e., could this magnitude of concentration increase significantly affect a dornstream <br />hydraulically connected water source). In [he case of the alluvial aquifer, there is no <br />downstream use, but there is flood irrigation being practiced approximately 1.5 miles <br />belor the loadout. the principal source of water for the Hood irrigated fields is the <br />Yampa River via Ilalker Ditch; however, there is [he potential for Dry Creek rater to also <br />enter calker Ditch. It is unknown at this time as to whether there is upward flow from <br /> • <br />the alluvium into the Dry Creek streamflow in the lower reaches of Dry Creek, but the <br />6 Revisetl OG/18/9< <br />