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Memo: Seneca II AHR -4- L April 8, 1986 4. The sulfate data for Station SW-S2-5 indicate an increase in concentrations from 1983 to 1985. Are there upstream sources of influence which cause this increase? If not, an attempt to explain this effect would be interesting in the discussion section for Little Grassy Creek. A statement is made that "...where water quality has changed, the concentrations are higher in 1984 due to a decreased dilution factor". This statement would apply to 1985 instead of 1984. An alternate explanation is that more sulfate is being leached from the same amount of disturbed area. Discussion of observed water quality conditions related to the amount of disturbed area or volumes might also be investigated in future AHR's. 5. On page 7-59 o the Seneca II permit application the statement is made: "As mining progresses into the Fish Creek watershed, these data will be checked to determine if there is a deteriorating effect on Fish Creek due to the mining of Seneca II". Mining has progressed into the Fish Creek tributary (aka Cow Camp Creek) and rather increased concentrations of sulfate and total dissolved solids is demonstrated by the 1985 data. The AHR could benefit by a comparison of recent data to baseline data, rather than going back only to 1983 as has been the case. A statistical summary of baseline data using SAS could be completed fairly easily once data has been entered in the data base for all of the stations. Certain adjustments or omissions may be required, however, due to changes in station locations, sampling, chemical analysis techniques and other variables as necessary. For instance, if the USDA-SEA Station 1001 is considered acceptable for comparison to Station SW-S2-6: Year Sulfate 1980 74 (mg/L mean concentration) 1983 272 1984 508 1985 1060 There appears to be almost a doubling of sulfate each year in the unnamed Fish Creek tributary. It will be interesting to see if sulfate will indeed level out over the next two years as stated in the 1985 report. The Division requests that PCC provide similar comparisons in next year's AHR. 6. The sediment-level survey of NPDES ponds as described in the report should be considered as a regular inclusion in future AHR's. Amore frequent interval than every three (3) years could provide valuable information on erosion rates but should be adequate for monitoring clean-out levels. The Division requests that Peabody consider including a brief section in future AHRs on sediment control under the surface water discussion. This could include general comments on maintenance of ditches, culverts, ponds, channels and rills and gullies that were required during the previous year. This additional information would be valuable for assessing the suspended-sediment aspect of surface water quality. /pjh 9082E