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Evaluation of Potential Subsidence Impacts of Longwall Mining in the Spruce Stomp Lease Area <br />to Aquatic Life and Water Supply <br />uses for these segments which include Aquatic Life Cold (1), Recreation (Existing Primary <br />Contact Use for Segment 4 and Potential Primary Contact Use for Segment 5), Water Supply and <br />Agriculture. This segment is not identified as impaired or requiring monitoring and evaluation <br />on Colorado's Section 303(d) List of Impaired Waters and Monitoring and Evaluation List. <br />Table 6 summarizes the water quality data at West Fork Terror Creek and the identified numeric <br />standards for this water body. <br />Based on water quality and flow data provided by Bowie, West Fork Terror Creek temperatures <br />ranged from —0.7 °C to a maximum reported temperature of 26.7 °C, which is well above the <br />standard mean weekly average temperature of 17 °C. Flow was not observed concurrent with the <br />high observed water temperature, making it difficult to explain the cause of this exceedance. <br />The mean observed water temperature, 8.2 °C is in attainment of the chronic temperature <br />standard. <br />The total suspended solids (TSS) maximum value of 122 milligrams per liter (mg/L), as reported <br />by Bowie's water quality sampling reports, is low considering personal communication with <br />Bowie personnel who report that for much of the spring, West Fork Terror Creek has high <br />turbidity, described as similar to "chocolate milk." WWE has observed muddy spring runoff in <br />other drainages in the North Fork River Valley. During WWE's April 2012 site visit, visibility <br />was approximately 2 feet and the water was markedly turbid. During subsequent visits during <br />summer and fall 2012, the creek was typically clear and lacking observable turbidity. The mean <br />reported TSS value of 23 mg/L is consistent with clear water which could support cold -water <br />aquatic life. Reports from the 1970s and 1980s identify West Fork Terror Creek as erosive and <br />"milky" (West Water Engineering, 2011). It is not clear whether these accounts coincide with <br />particular activities which were occurring during that period or if they are indicative of the <br />ambient water quality. Generally, TSS and turbidity are positively correlated with stream flow. <br />Relatively higher TSS and turbidity levels would be expected during spring runoff and during <br />years with higher than average flow. Conversely, low flow years, such as 2002, will generally <br />have relatively lower TSS and turbidity. While other provided water quality parameters do not <br />appear to be problematic for the water's designated uses, the reviewed water quality data do not <br />121 - 014.000 Wright Water Engineers, Inc. Page 10 <br />January 2013 <br />