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ekienvironment & water well to well and between monitoring events. Coliform bacteria are widespread in the environment and occur in large numbers within soil and background water. 3.2.2 TDS At the Mossdale LAA A23, recycled wastewater was last applied in September 2009 and therefore present-day TDS concentrations and concentration trends likely represent background conditions. The TDS concentration in compliance well MWM-12, located in LAA A23, was the same as measured in Fall 2022 (2,880 milligram per liter (mg/L)). The TDS concentrations in samples from this well have been generally decreasing since Fall 2018. TDS concentrations decreased in most CLSP compliance wells (CLSP-1, CLSP-3, CLSP-9, CLSP-12, and MWM-19). The sample from CLSP-8 increased by 330 mg/L and the sample from CLSP-11 increased by 250 mg/L in comparison to Fall 2022 concentrations, however TDS concentrations measured in both well samples were within their historical ranges. The TDS concentration in the sample from River Islands well MWR-32 decreased by 620 mg/L since that last time it was sampled (Spring 2022) and is within the range of its historical concentrations (4,610 mg/L), however the result exceeded the proposed groundwater limitation (4,495 mg/L). The TDS concentrations in samples from this well showed statistically significant upward trends prior to recycled water applications to LAA A31,and since 2016 the concentrations have shown greater variability between sampling events; the variability can be explained in part by rainfall conditions. The TDS concentration in the sample from River Islands compliance well MWR-28 (1,720 mg/L) decreased by 910 mg/L since the last time it was sampled (i.e., Spring 2022). The TDS concentrations in MWR-28 have been variable, yet generally decreasing since First Quarter 2015. The TDS concentrations in all CTF wells decreased (KMW-2, KMW-4, KMW-6, KMW-8, and KMW- 10) relative to the concentrations in the Fall 2022 samples. The Spring 2023 TDS concentrations in the sample from KMW-9 (980 mg/L) increased by 60 mg/L relative to the concentration in Fall 2022; however, the concentration remains below the historical maximum (1,590 mg/L). The TDS concentration in KMW-11 (3,020 mg/L) increased 110 mg/L relative to the concentration observed in Fall 2022; however,the concentration remains below the historical maximum (3,820 mg/L). Measured variations in dissolved constituents in CTF monitoring wells including TDS are likely influenced in part by former up-gradient unlined gypsum and wastewater ponds at an agricultural chemical production facility(see Finding 42 of the WDRs) and application of recycled water in 1313-1. 3.2.3 Nitrate as N The Spring 2023 NO3-N concentration in the sample from Mossdale compliance well MWM-12 (5.7 mg/L) increased 1.8 mg/L relative to the concentration measured in the Fall 2022 sample; however, the concentration did not exceed the historical maximum observed in this well (7.7 mg/L). City of Lathrop 13 13 July 2023 EKI B90088.03