Department of Environment Regulation
Annual Audit Compliance Report Form
Environmental Protection Act 1986, Part V
Licence holder: Water Corporation
Trading as: Merredin Wastewater Treatment Plant
ABN: 28 003 434 917
Registered address: 629 Newcastle Street, LEEDERVILLE, WA 6007 Reporting period: 01 / 07 / 2019 to 30/06/2020
Section B - Statement of Compliance with Licence Conditions
Did you comply with all of your licence conditions during the reporting period?(please tick the appropriate box)
•
Yes - please complete:• section C;
• section D if required; and
• sign the declaration in Section F.
~ No - please complete:
• section C;
• section D if required;
• section E; and
• sign the declaration at Section F.
Section C - Statement of Actual Production
Provide the actual production quantity for this reporting period. Supporting documentation is to be attached.
Prescribed Premises Category Actual Production Quantity
54 Inflow 500m3/day
Section D - Statement of Actual Part 2 Waste Discharge Quantity
Provide the actual Part 2 waste discharge quantity for this reporting period. Supporting documentation is to be attached.
Prescribed Premises Category Actual Part 2 Waste Discharge Quantity Not Applicable
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Annual Audit Compliance Report Form
Department of Environment Regulation
Section E - Details of Non-Compliance with Licence Condition
Please use a separate page for each condition with which the licence holder was non-compliant at a time during the reporting period.
Condition no: 1.3.5 (a) & (b) Details of non-compliance:
Date(s) of non-
com liance: 30/08/2019
On the morning of Friday, 30 August 2019 two civil operators attended the Merredin WWTP to carry out routine inspections and maintenance. Upon arriving at the WWTP they noted that the pond levels in 4, 5 and 6 were extremely high to the point where internal overtopping had occurred between pond 4 and 5 and between pond 5 and 6. All wastewater was contained with the treatment ponds infrastructure; there was no overtopping of ponds on the external embankments (no discharge to environment).
DETs and Civil operators opened the valve to the Shire of Merredin Overflow Holding Pond and the valve to shire re-use was opened further to ensure that pond levels were reduced as quickly as possible. Internal overtopping of pond 4, 5 & 6 had ceased by 2 September 2019. The levels of both the re-use wet well and the Shire of Merredin Overflow Holding Pond were then monitored regularly by a DET and civil operator over the following weeks to ensure that no overtopping of the Shire of Merredin Overflow Holding Pond to Cohn Creek occurred. The wet well level to re-use, the UV lamp's capacity and condition and the level on the Shire's re-use dam (Shire Dam No.1) was also monitored.
Free board of greater than 150mm was re-established (measured at the low points on the inner embankments of ends 4, 5 & 6 on around 25 Se tember 2019.
What was the actual (or suspected) environmental impact of the non-compliance?
NOTE - please attach maps or diagrams to provide insight into the precise location of where the non- compliance took place.
There are no discernible environmental impacts from the overtopping incident as there was no discharge to the environment beyond the confines of the containment infrastructure. The integrity of the containment infrastructure was maintained.
Cause (or suspected cause) of non-compliance:
It was determined that the valve to the re-use wet well had been "throttled back" some months prior, reducing flow to re-use at some point in July 2019. This restricted flow caused the ponds to bank up over time; routine maintenance/inspections had failed to pick up the rising levels. 52mm of rain had fallen during the month of August, with an 11 mm event occurring on 30 August 2019, this had si nificantl increased inflow and exacerbated the rate in which the ends filled,
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Annual Audit Compliance Report Form
Department of Environment Regulation
contributing to the overtopping event.Action taken to mitigate any adverse effects of non-compliance and prevent recurrence of the non-compliance:
District operations have "locked out" the valve and have established a protocol whereby permission will need to be granted before the valve is adjusted. SCADA alarms have been set on Pond no.6 to ensure that "high" and "high,high" pond level alarms are received at an operational level. SCADA "low" and "low, low" flow alarms have also been set on a point post UV to monitor the WWTP's outflow. Operational alerts are now received when flow is measured at less than 5.0L/sec. Investigations are currently underway to ascertain further opportunities to increase output from the WWTP to the Shire of Merredin's re-use dam.
Was this non-compliance previously reported to DER?
~ Yes, and
D
Reported to DER verbally Date: I I~ Reported to DER in writing Date: 02 I 09 / 2019
Section F - Declaration
I/We declare that the information in this Annual Audit Compliance Report is true and correct and is not false or misleading in a material particular1. I/We consent to the Annual Audit Compliance Report being published on the Department of Environment Regulation's (DER) website.
Signature2:
Name: (printed) Position:
Date:
Seal (if signing under seal):
General Manager 0 erations
Signature:
Name: (printed)
Position: Date:
1 It is an offence under section 112 of the Environmental Protection Act 1986 for a person to give information on this form that to their knowledge is false or misleading in a material particular.
2 AACRs can only be signed by the licence holder or an authorised person with the legal authority to sign on behalf of the licence holder.
Annual Audit Compliance Report Form
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