| 1138316 |
11/10/2024 |
Deficient Monitoring |
The NPDES permit requires WQCP to monitor pH at the E-001 site. Since June 1, 2023, WQCP has implemented real-time pH monitoring at E-001 using a HACH Digital pH sensor (model #: DPD1P1), with data transmitted to SCADA via the HACH controller (model#: SC200). In November 2024, technical issues with the controller caused data transmission failures on 7 days, resulting in 3 days with data gaps more than 60 minutes and the total time of data gaps during the calendar month more than 7 hours and 26 minutes. These conditions are specified for compliance determinations using a continuous monitor (Order No. R2-2019-0021, Table 4, footnote 1). Despite the missing data, the effluent pH remained within the compliance range of 6-9 s.u., as confirmed by the upstream pH analyzer, located after the aeration basins and before the secondary clarifiers. The upstream analyzer typically records pH values similar to those measured at E-001 and demonstrated consistent compliance within the 6.0¿9.0 range throughout the month. A thorough investigation was conducted by the Lead Plant Mechanic Kenneth de Leon and Lead Operator Ryan Estrada. Hardware, communication, environmental, and SCADA-related causes were ruled out (see table below). However, software glitches or bugs remain a possible, undetermined factor. It was observed that when the analyzer sent a warning signal to the controller, data transmission between the controller and SCADA is paused. |
Violation |
N |
eSMR |
South San Francisco-San Bruno WQCP |
432955 |
R2-2019-0021 |
N |
