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INTEROFFICE MEMORANDUM <br />TO: JANET BINNS <br />FROM: ROB ZUBER <br />SUBJECT: SENECA IIW, SL -05, TSS AND SEDIMENTOLOGY EVALUATION <br />DATE: 4/21/2014 <br />Janet — <br />Regarding the water quality items from the SL -05 adequacy, I have the following comments <br />(numbers correspond to those in the DRMS adequacy letter of 9/4/2013, not to the numbers in the <br />Peabody response of last month). <br />Items 8a and 8b: Peabody response is sufficient. <br />Item 9a: SCC provided pond capacity data as requested. However, for some ponds (namely 005, <br />009, and 017) the capacities have declined significantly in recent years, and further evaluation or <br />explanation is necessary to show that Phase 2 release of the area is justified despite these <br />decreases in pond capacities. Is there any other data related to pond capacities that indicates a <br />trend of decreasing sediment loading into the ponds? <br />Item 9b: Because the SEDCAD analyses for Pond 006 indicate that the post- mining sediment <br />load is somewhat higher than the pre- mining sediment load (and thus the sediment loading <br />requirement of Rule 3.03.1(3)(b) is not met), the Division requests that SCC provide a <br />comparison to an analysis of the worst -case scenario (or similar) for the Pond 006 area; this could <br />be the results of a new SEDCAD run or specific reference to existing information in the Seneca <br />IIW PAP. Also, the Division has observed that the sub - watershed particle size distributions in the <br />SEDCAD run for pre- mining conditions contain many values of 0 %. It is possible that if non- <br />zero (realistic) values were included in these tables, then the results of pre- mining sediment loads <br />might match post- mining sediment loads. <br />'•9 <br />