| Violation ID |
Occurred Date |
Violation Type |
(-) Violation Description |
Corrective Action |
Status |
Classification |
Source |
| 1137758 |
11/12/2024 |
OEV |
E.coli Instantaneous Maximum limit is 400 MPN/100 mL and reported value was 866.4 MPN/100 mL at EFF-001C. |
Staff contribute the exceedance to the quick change in the season where temperatures fluctuated daily from warm to cold temperatures impacting the biology of the activated sludge system. Staff adjusted operations of the treatment plant to adjust for the seasonal change; however, the reactions from plant biology reaction were slower to adjust. Staff rotated and cleaned EFF-001A (ASP) contact chamber and cleaned the EFF-001C (Outfall) channel to reduce the likelihood additional contributions were a result of unknown external influences. |
Violation |
U |
eSMR |
| 1134941 |
09/30/2024 |
CAT2 |
Cyanide, Total (as CN) Monthly Average limit is 4.3 ug/L and reported value was 6.6 ug/L at EFF-001C. |
VSD Staff are continuing to evaluate the potential causes of cyanide through study sampling and process modifications to determine the appropriate solutions and reduce the likelihood of recurrence of exceeding the permit limitations. |
Violation |
B |
eSMR |
| 1134942 |
09/23/2024 |
CAT2 |
Cyanide, Total (as CN) Daily Maximum limit is 8.5 ug/L and reported value was 8.7 ug/L at EFF-001C. |
VSD Staff are continuing to evaluate the potential causes of cyanide through study sampling and process modifications to determine the appropriate solutions and reduce the likelihood of recurrence of exceeding the permit limitations. |
Violation |
U |
eSMR |
| 1130955 |
07/31/2024 |
CAT2 |
Cyanide, Total (as CN) Monthly Average limit is 4.3 ug/L and reported value was 05.1 ug/L at EFF-001C. |
At the beginning of June, the plant faced an upset with high solids in the chlorine contact chamber. Staff have continued to make operational changes throughout the month to resolve the operational upset. Staff are contributing the high initial July value to the plant still being in the recovery phase from the upset. The second elevated value is assumed to arise from the semi-annual process strategies of switching clarifiers in the primary and secondary systems in the same week when attempting to recover from the upset ¿ delaying the recovery phases.
VSD Staff are continuing to evaluate the potential causes of the cyanide through study sampling and resolve the concerns regarding the treatment upset and process modifications to determine the appropriate solutions.
|
Violation |
U |
eSMR |
| 1129969 |
06/30/2024 |
CAT2 |
Cyanide, Total (as CN) Monthly Average limit is 4.3 ug/L and reported value was 6.3 ug/L at EFF-001C. |
Staff attributed the high cyanide result to a plant upset that occurred in the beginning of June resulting in high solids in the chlorine contact chamber and increased total nitrogen values. Operations staff made operational changes throughout the month to resolve the operational upset.
VSD Staff are continuing to evaluate the potential causes of the cyanide results and resolve the concerns regarding the treatment upset to determine the appropriate solutions.
|
Violation |
B |
eSMR |
| 1119622 |
07/31/2023 |
OEV |
E.coli Instantaneous Maximum limit is 400 MPN/100 mL and reported value was 1413.6 MPN/100 mL at EFF-001C. |
The first August monthly E. coli sample was collected 3 days later (Thursday), and the result was 160.7 MPN/100mL, indicating that treatment conditions were being met and the high result from Monday was most likely due to the abnormal weather event. |
Violation |
U |
eSMR |
| 1117522 |
04/04/2023 |
CAT2 |
Cyanide, Total (as CN) Monthly Average limit is 4.3 ug/L and reported value was 6.4 ug/L at EFF-001C. |
VSD staff are continuing to evaluate the potential causes of cyanide results by investigating the different forms of available cyanide, test methods, matrix interferences and solutions, sampling handling and preservation. |
Violation |
U |
eSMR |
| 1112886 |
12/31/2022 |
CAT2 |
Cyanide, Total (as CN) Monthly Average limit is 4.3 ug/L and reported value was 6.1 ug/L at EFF-001C. |
To determine if the cyanide results were due to external factors (i.e., pretreatment), preservation techniques (i.e., NaOH, pH adjustment) or generated by the treatment processes, a cyanide study was performed on 12/19 and 12/27. Staff collected samples from INF-001 (Influent), Secondary Final Clarifier effluent (pre-chlorination), EFF-001A (ASP), and EFF-001C (Outfall) samples. The samples included an unpreserved, preservation with NaOH to pH >10, and pretreatment with sulfamic acid prior to NaOH preservation to pH >10 (reduce Nitrate, Nitrite interferences). These samples were also sent to 2 different contract laboratories to eliminate any additional biases.
Based upon the results of the cyanide study, staff have not determined whether the cyanide is being generated during the chlorination phase of disinfection treatment or during effluent sample storage at high pH (pH > 12) which allows cyanide to be generated in the sample bottle itself. Staff will be monitoring the chlorination process to determine the threshold limit to reduce the possibility of generation of the disinfection by-product cyanide and evaluating sample storage detention times from the time the sample was taken until the sample was analyzed even when using approved sample preservation protocols to determine whether these results were just false positives in the cyanide analysis.
|
Violation |
U |
eSMR |
| 1110647 |
10/31/2022 |
CAT2 |
Cyanide, Total (as CN) Monthly Average limit is 4.3 ug/L and reported value was 5.5 ug/L at EFF-001C. |
To determine if the cyanide results were due to external factors (i.e., pretreatment), preservation techniques (i.e., NaOH, pH adjustment) or generated by the treatment processes, a cyanide study was performed on 11/14. Staff collected samples from INF-001 (Influent), Secondary Final Clarifier effluent (pre-chlorination), and 4 -EFF-001C (Outfall) samples. The EFF-001C samples included an unpreserved, preservation with NaOH, and pretreatment with sulfamic acid prior to NaOH preservation (reduce Nitrate, Nitrite interferences). These samples were also sent to 2 different contract laboratories to eliminate any additional biases.
Based upon the results of the cyanide study from 11/14; staff have not determined whether the cyanide is being generated during the chlorination phase of disinfection treatment or during effluent sample storage at high pH (pH > 12) which allows cyanide to be generated in the sample bottle itself. Staff will be monitoring the chlorination process to determine the threshold limit to reduce the possibility of generation of the disinfection by-product cyanide and evaluating sample storage detention times from the time the sample was taken until the sample was analyzed even when using approved sample preservation protocols to determine whether these results were just false positives in the cyanide analysis. |
Violation |
U |
eSMR |
| 1108186 |
08/31/2022 |
OEV |
E.coli Instantaneous Maximum limit is 400 MPN/100 mL and reported value was 648.8 MPN/100 mL at EFF-001C. |
On August 30, 2022, operations staff received a plant alarm for low chlorine residual on the ASP contact chamber. Staff identified settled solids on the surface of the secondary clarifier and in the ASP contact chamber. Staff put a clean secondary clarifier and contact chamber online and took offline the processes being affected. Staff also increased the chlorine dosing setpoint to account for the increased solids being received from the secondary clarification process. |
Violation |
U |
eSMR |
| 1108185 |
08/02/2022 |
OEV |
E.coli Instantaneous Maximum limit is 400 MPN/100 mL and reported value was 547.5 MPN/100 mL at EFF-001C. |
Operational changes were made to increase solids to improve treatment after the E.coli incident in July due to a loss of solids under aeration. The increase of solids in the activated sludge system resulted in a strain on maintaining dissolved oxygen concentrations in the system. To improve treatment efficiency with the summer conditions, operational changes were made to reduce the detention time of the solids by reducing the number of aeration basins online increasing oxygen availability. The modification temporarily led to a loss of solids and a rise in ammonia concentrations impacting the disinfection efficiency. In response to the incident, operations staff are monitoring the solids inventory for performance and have switched the contact chambers and increased the chlorination setpoint to increase disinfection. Staff will continue to monitor the conditions in making every effort to reduce the likelihood of future violations. |
Violation |
U |
eSMR |
| 1107380 |
07/26/2022 |
OEV |
E.coli Instantaneous Maximum limit is 400 MPN/100 mL and reported value was 1096.3 MPN/100 mL at EFF-001C. |
In response to the incident, operations staff are increasing the solids concentration to improve performance and have switched to the offline chlorine contact chamber to increase disinfection efficiency. The laboratory results for coliform sampling the week prior the July 26th exceedance were all in compliance with the NPDES permit. Staff will make every effort to avoid this violation in the future. |
Violation |
U |
eSMR |
| 1103585 |
03/17/2022 |
DMON |
On 03/17/2022, 24-hour composite samples sent to Babcock Labs for analysis of carbonaceous BOD (cBOD) and total suspended solids (TSS). However, Babcock Lab sample receiving logged the EFF-001A (ASP) sample for cBOD and Total Dissolved Solids (TDS). VSD was not aware of this mistake until the final laboratory report was submitted to staff on 04/18/2022 (32days later).
|
VSD staff contacted Babcock Labs and informed them of the error. Babcock laboratory staff have updated the parameter list for VSD and have retrained staff on checking COC for accuracy. VSD Staff have been given online access to the Babcock portal for more recent up-to-date status tracking. Please see attached QA Letter from Babcock regarding their resolution to the issue.
|
Violation |
U |
eSMR |
| 1092203 |
06/15/2021 |
DMON |
Total Suspended Solids (TSS) analysis was not performed on the 24-hr composite sample at Location EFF-001A within 40 CFR 136 holding time requirements of 7days. Analysis occurred after the holding time requirement and has been flagged on the lab report. |
Communication with the contract laboratory has been updated to improve the needs of the treatment plant to reduce the possibility of reoccurrence of the event; when district laboratory staff are unable to analyze the samples internally. |
Violation |
U |
eSMR |
| 1092204 |
06/15/2021 |
DMON |
Total Suspended Solids (TSS) analysis was not performed on the 24-hr composite sample at Location INF-001 within 40 CFR 136 holding time requirements of 7days. Analysis occurred after the holding time requirement and has been flagged on the lab report. |
Communication with the contract laboratory has been updated to improve the needs of the treatment plant to reduce the possibility of reoccurrence of the event; when district laboratory staff are unable to analyze the samples internally. |
Violation |
U |
eSMR |
|
Report displays most recent five years of violations. Refer to the Interactive Violation Report for more data.
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