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monitoring wells along Foidel Creek but these changes are likely attributable to the discharge of <br />mine water to the surface system and recharge to the alluvium. <br />Subsidence lmpacts on Ground Water Oualitv <br />The PHC predicts no significant ground water quality change. Data presently indicates no <br />significant quality change in ground water due to subsidence. However, water which is Bumped <br />in the SWMD shows a significant change in quality, in particular iron and TDS. It is unclear at <br />this time whether the cause is the rubblized `'gob" azea or whether other factors are involved. <br />Ongoing monitoring and analysis may lead to a better understanding of these quality changes. <br />Surface Water <br />Impacts of Mine Water Discharee <br />The PHC predicts material damage suspect levels could be exceeded for TDS and sulfate on <br />Middle Creek below Foidel confluence, Fish Creek, and Trout Creek below Middle Creek. 1998 <br />AHR data indicates a clear increase in conductivity when discharge began again at the FCB after <br />a two year hiatus. Site 1002, site 27A, and site 1003, all downstream of the FCB, returned EC <br />values near 2000 umhos/cm, well above the previous levels of 800-1000 umhos/cm. This <br />corresponds with the discharge of high TDS mine water from sump areas in the SWMD. The <br />PHC revision currently under review (TR-32) includes discussion of the potential impacts of this <br />mine water and evaluates stream loading based on potential future conditions. Lower Middle <br />Creek, lower Fish Creek, and lower Trout Creek below Fish Creek could all be affected to levels <br />exceeding material damage standards. Other than the late fall 1998 episode of mine water <br />discharge, the mine did not discharge water to the surface streams. The data clearly indicates <br />this fact. Fish Creek conductivity ranges from about 800-1100 umhos/cm, Trout Creek <br />conductivity ranges around 600-700 umhoslcm, and site 900 conductivity on Foidel Creek is <br />approximately 2000 umhos/cm. <br />Stream Standards Comparisons <br />Current PHC information concerning applicable receiving stream standards is not provided in <br />enough detail to evaluate actual data reported in the 1998 AHR. TR-32 will address this <br />deficiency. <br />Dischar eg of Ephemeral Runoff from Disturbed Areas <br />Excluding mine water discharge, any water quality or quantity effects from surface water runoff <br />from the mining disturbance are not detectable in the monitoring data at this time. Sediment <br />ponds treat runoff to meet effluent limits prior to entering streams. Suspended sediment levels <br />on Foidel Creek averaged 19 mg/1 upstream of mining disturbed areas and 25 mg/1 downstream <br />of mining distwbance, indicating virtually no change. <br />Streamflovv-Groundwater Relationships <br />