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Memo: Seneca II AHR - 3 - April 8, 1986 In addition, a footnote on the table which identifies the tri-annual sampling days would be beneficial for review purposes. An arrow or other symbol placed on the hydrographs would also assist in interpretation of how water quality relates to flow conditions from monitoring data collected. 6. On page 7-77 of the Seneca II permit application a statement is made "It is expected that as more flow data becomes available, verification of the (HYMO) model will be possible". Has PCC considered updating the model necessary with the flow data received recently in the continuing monitoring program? Surface Water Quality 1. In the discussion of water quality data for Pond 004 and SW-S2-6, exceedance of the 1 ug/L stream standard for cadmium (on Fish Creek tributaries) is noted on September 5, 1985. Pond 004 reports less than 5 ug/L, while at the surface station downstream a value of 8 ug/L is reported without any "less than" designation. This leads me to believe the detection limit for cadmium analysis is 5 ug/L and that indeed a value of 8 ug/L was observed. This is a very high concentration and far exceeds the standard. The dissolved manganese exceedance is similarly as large. PCC should discuss directly the sources and processes involved to explain these high concentrations. A further discussion would be appropriate in future reports if these concentrations continue to be observed. 2. On page 34 of the AHR, salinity is listed under the water-quality variables monitored at the NPDES discharges. A review of Appendix F shows that specific conductance, or electrical conductivity, is actually being monitored. Asa lab determination of "salinity" does exist (Method 209, APHA, "Standard Methods for the Examination of Water and Wastewater," 14th Edition, 1975), the use of the term salinity should be omitted to avoid any confusion of terms. 3. A comparison measurements and lab two. For instance a Date 03-06-85 06-06-85 09-04-85 EC (field) um os cm 660 1220 1470 EC (Lab) um os cm) 1140 1820 1770 The equivalence between field and lab data is not good, even when very close correspondence is not expected. PCC should address this discrepancy. The concentration of total dissolved solids determined by the lab on these dates would indicate that the lab determinations are accurate because TDS is about 0.6 times the EC values, as is usually the case. Because EC is a variable reported for NPDES self-monitoring, and because accurate data is desirable, PCC should consider identifying this problem with field measurements of conductivity and correcting it as soon as possible. of electrical conductivity (EC) values reported from field determinations shows considerable differences between the t Station SW-S2-5 on Little Grassy Greek: