SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

- • Mr. Pat Mickelson • -2- 19 June 1992 Simpson Paper Company discharging effluent considered to be a designated waste, and 2) address what concentration of TDS in the effluent would not threaten to impact ground-water quality." Even though the purpose of the May 92 report changed from the determination of designated waste levels to the development of a model to track the disposition of mill effluent and predict effluent quality and its impact on receiving waters under reduced-TDS loading, the May 92 report provides sufficient information to make a determination under Chapter 15. That determination is that the Simpson discharge is a designated waste. The May 92 report demonstrates that ground water quality will continue to be degraded at the Simpson site. The model indicates that 1068 tons of salt (2363 tons discharged to land minus 1295 tons/yr extracted from ground water) at a discharge concentration of 1406 mg/l are added to the ground water system by Simpson each year. This salt either ends up as horizontal outflow from the site or deep percolation where it degrades lower aquifers. Figure 19 shows that ground water inflow to the semi-perched zone has a TDS of 415 mg/l and is degraded to 1840 mg/l before leaving the site. Intermediate zone degradation is attributed to salt inflow to the intermediate zone from offsite. However, this offsite degradation has not been demonstrated. Contours of TDS for the Intermediate Aquifer Zone in Figure 15 show TDS moving radially from the Simpson disposal area, not toward the Simpson site. A more plausible explanation is that the salt discharge from Simpson is degrading its own supply by recycling the salt discharge into the supply well (s) . On page 21, the report states that "The mound of high EC under the 'new' percolation ponds, and the skewed nature of the contours around production well 4 indicate that pumping induces migration of effluent toward the pumping well . " The May 92 report indicates that Ripon City wells are experiencing a long term TDS degradation. Simpson's discharge of salt to ground water over the years has no doubt affected Simpson water supply ::ells. Since there is evidence that some of Simpson's discharge flows northward, it is possible that Simpson's discharge may be the cause of degradation in the City' s wells. A reduction in the ratio of TDS-effluent to TDS-influent from 2.31 to 2.16 was analyzed to determine its effect on ground water. The results show that there will be an immediate improvement in the semi-perched zone, however the salt discharge will continue to degrade ground water. The continued degradation of ground water will be at a slightly reduced rate. Since the discharge from Simpson Paper is a designated waste, we propose to write Chapter 15 Waste Discharge Requirements to require the containment of these wastes. New waste discharge requirements are needed quickly since the current discharge is an unpermitted discharge. Simpson should consider alternative methods of salt disposal in order to comply with the requirements of Chapter 15 for the land disposal of wastes.