Question - Water

1. In relation the Lower Molonglo Water Quality Control Centre (LMWQCC), why is the 2012 reported capacity significantly reduced from the 1973 design capacity.
2. What is Icon Water doing to improve treatment capacity at LMWQCC.
3. What were the actual estimated bypass flows for the past 10 years.
4. What were the water quality tests done upstream and downstream of where the effluent is discharged into the Molonglo River and also in the Murrumbidgee River, and of the effluent discharged, before during and after the bypass.
5. Does the Environment Protection Authority (EPA) require this monitoring; if not, why not.
6. Was the bypass dam empty before both events; if not, why not.
7. Does the EPA get daily updates of the bypass dam volumes during wet events; if not, why not.
8. If LMWQCC can treat up to 190ml per day, why wasn’t the bypass dam of volume 147ml able to be emptied in about two days.
9. What is Icon Water doing to reduce stormwater ingress to the sewer network, especially as the sewers react to stormwater ingress almost as quickly as the normal stormwater system.
10. What is the population that LMWQCC can treat if the treatment capacity has not increased in 50 years.

(1)   Icon Water advises that the Lower Molonglo’s original design capacity was 270,000 equivalent persons (EP). The original plant was designed to be augmented in three stages to an ultimate capacity of 1,000,000 EP. In 2010, Icon Water augmented the Lower Molonglo Water Quality Control Centre (LMWQCC), increasing capacity to treat up to 100 megalitres per day, which is equivalent to approximately 550,000 EP.

In 2012, Icon Water undertook a capacity assessment which highlighted that the plant was sensitive to primary treatment variability, particularly sludge settleability, which significantly impacted the secondary treatment process capacity. This report made several recommendations for operational approaches to improve overall performance, which have been implemented. 

(2)   Icon Water advises that since the 2012 review, Canberra’s population has grown more rapidly, and Icon Water is beginning to see the impact of a changing climate on the wastewater system. This has brought forward the requirement for augmentations of some systems at LMWQCC. 

Several major projects were initiated in the 2013‑2018 and 2018‑2023 regulatory periods to increase capacity in the secondary treatment and solids handling systems. They are now included in Icon Water’s 2023‑2028 pricing submission for construction. These projects are currently moving from concept design phase to planning and detailed design, having been through a rigorous options assessment to identify suitable technologies that are able to satisfy Icon Water's operating and performance requirements. The projects have been developed with an ultimate design horizon of 2070 and a forecast population of 1,000,000 EP. 

(3)   Icon Water advises that since the completion of the LMWQCC bypass storage dam, there have been 11 release events associated with major wet weather events: 

During these major wet weather events the releases of partially treated effluent typically constituted less than 1 per cent of the river flow.

(4)   Icon Water collects routine fortnightly and monthly data from the receiving river systems. Tests are those parameters prescribed in Environmental Authorisation EA0009 for LMWQCC, including chemical, physical, and biological characteristics. 

The samples are collected from sites located both up and downstream on the Molonglo River and for the Murrumbidgee River downstream of the Plant. It is unsafe to collect samples when river flows are high, which typically coincides with discharges from the bypass dam.

(5)   As above, the water monitoring tests are prescribed in Environmental Authorisation EA0009 for LMWQCC. Further, under EA0009 (see https://www.accesscanberra.act.gov.au/s/epa-public-registers) an Environment Management Plan (EMP) is required under conditions 17.1-3. The EMP is required to identify all activities that may have an adverse impact on the environment or the potential to cause environmental harm, and detail the mechanisms employed to prevent or minimise the impact of these activities.

(6)   Icon Water advises that the Bypass Storage dam is emptied as far as infrastructure allows at all times. Volume in the dam leading into the wet weather events of each of the above-mentioned releases was 2 per cent or less. It is worth noting that to protect the Storage Dam Return Pumps, which are used to pump from the storage dam back to the inlet of the treatment plant, from potential damage they automatically shut down at 3 metre water depth, which is approximately 1 per cent of the dam storage. 

(7)   The ACT EPA advises that it is notified of bypass events at LMWQCC through Icon Water contacting the ACT EPA on call officer by phone. This notification is covered by condition 7.1 of EA0009: 

In the event that an incident has caused, is causing or is likely to cause material or serious environmental harm, whether the harm occurs on or off the site, the Authorisation holder, their employee or agent must report the incident to the Authority immediately after it becomes known to the Authorisation holder or to their employee or agent in accordance with the below clause. 

The incident must be reported to the Authority by telephoning Access Canberra on 132281 during and outside business hours. 

Icon Water advises that it notifies the ACT EPA, NSW EPA and other relevant regulators and downstream stakeholders of the commencement of partially treated effluent being released to the environment, and on the cessation of the release, as part of Icon Water’s incident management and restoration approach. Icon Water also notifies the public at commencement of releases through media releases and other notification channels including social media. A detailed incident report is provided to the ACT EPA post event including calculations of release volumes once validated data is available.

(8)   Icon Water’s Sewerage network continuously conveys raw wastewater into LMWQCC. Following wet weather, the wastewater inflows to LMWQCC are elevated above normal, even when bypass to the storage dam is not being used. The volume of partially treated effluent stored in the Bypass Storage Dam is gradually returned to the inlet of the treatment plant for re-treatment. Icon Water operators must balance the ongoing flow entering the plant from the network and the return flows from the bypass to not exceed maximum treatment capacity and therefore this can take more than two days to empty. 

(9)   Bureau of Meteorology water balance and water outlook models of the ACT predict that deep soil moisture content reached 30-year record high levels in 2021-2022. Inflows to LMWQCC historically reflect the deep soil moisture and have also seen record high inflows in late 2022. 

Inflow and Infiltration (I&I) is a characteristic of all sewerage networks. Icon Water monitors industry best practice in identifying the levels of I&I within the network and assessing where it is economically viable to institute remedial works to actively target I&I. Specifically, Icon Water uses sewer gauging to identify catchments with the largest proportional flow to the services population which allows a targeted I&I reduction approach. Flow monitoring at sewer pump stations has also been utilised in this space to consider broader sewer catchment impacts. Individual inspections of existing backflow devices around the network have been undertaken to accelerate maintenance of these assets if required.

Icon Water has an extensive sewer flow gauging network across Canberra, which allows not only the monitoring of network demand over time but also the breakdown of demand from different areas of the city. The gauging network is a key tool in being able to track network performance trends over time. With regards to I&I, this allows Icon Water to analyse the system response to rainfall and assess performance against industry benchmarked metrics. More targeted network interventions and maintenance activities across smaller catchment areas can then be conducted to address I&I issues when they occur. 

Icon Water’s sewerage network has historically had low rates of I&I due to its relatively young network age.  Implementing additional cost-effective controls in this space is difficult as I&I identification and remediation works have high costs attached and small defects in the network can be numerous and very difficult to locate accurately. Other than the I&I management techniques mentioned above, Icon Water’s overall maintenance and targeted renewals programs also provide benefits of managing this issue. During the 2018-2023 regulatory period Icon Water will have renewed approximately 50 kilometres and cleaned or inspected approximately 1,400 kilometres of sewer mains. Additionally, Icon Water will have completed approximately 900 targeted localised sewer main repairs on reticulation, branch lines and service connections. 

(10)   As noted in the response to question 1, LMWQCC’s original design capacity was 270,000 EP which was intended to be augmented in three stages to an ultimate capacity of 1,000,000 EP. In 2010, LMWQCC was augmented, increasing its treatment capacity to 100 megalitres per day which is equivalent to approximately 550,000 EP. Icon Water have several projects underway to further augment this capacity to cater for approximately 790,000 EP. These projects are planned for construction during the 2023 – 2028 regulatory period.  

Icon Water has also recently completed a review of its Wastewater System Strategy which considers infrastructure required to support long term population growth over a 50-year planning horizon.