6.13 Sewerage and Septic System Pathogens

MidCoast Council operates eight Sewerage Treatment Plants (STPs) in the Manning catchment, at Gloucester, Wingham, Dawson wetlands (Brimbin), Harrington, Manning Point, Old Bar, Coopernook and Lansdowne.

Most of the region is unsewered, relying on on-site sewage management (OSSM) systems including traditional septic systems and pump-to-sewer systems. MidCoast Council (MCC) has the responsibility to ensure that all onsite sewage management systems are approved, installed and managed so that they comply with the requirements under the Local Government Act 1993 and do not pose a risk to the environment or public health.

Failing systems or mismanagement of OSSMs present a pathogen risk to groundwater and receiving waters, with consequent health risks for the oyster industry, potable water and recreation. 59

Sewerage and STP run-off have been found to affect water quality in the Manning, particularly during high rainfall events.60 While the highest faecal input comes from livestock, human pathogens have the highest safety risk.

Pathogens (faecal coliforms and E. coli) from sewerage and septic systems are an

issue for the local oyster industry, particularly at Pelican Bay, Scotts Creek and the South Channel. In the Manning oyster fishery, rainfall exceeding 25mm in 24 hours is a trigger for closure of harvest areas due to the potential decrease in salinity and increase in faecal coliforms that can result from significant rainfall stormwater run-off.6162 Depuration requirements add time and cost to the harvest-to-market process. Critical risk on-site sewage management systems for the oyster industry are located within 100 meters of the shoreline and adjacent to a shellfish harvest area.63

Pathogens from human sources pose a risk to raw water quality for potable water

extracted from the Manning catchment at Barrington and Bootawa. MidCoast Council’s water services team (formerly MidCoast Water) held drinking water risk workshops in May 2016 and July 2020, both of which identified bacteria, viruses and protozoa as high to extreme risk for raw untreated water64. Water Treatment Plant and operational policies (e.g. selective extraction from the river) produce safe drinking water (L. Andersons pers. comm. Aug. 2020).

Pathogens present a hazard for passive and secondary recreation, with popular activities including swimming, boating and kayaking. This is rarely an issue. After the 1-in100-year flood in March 2021, water quality testing by the Environment Protection Authority gave the all-clear for swimming in the Manning and Dawson Rivers less than two weeks after the flood.

Stakeholders include: NSW Food Authority, MCC Water Services, MCC Environmental Health and Natural Systems teams, Environment Protection Authority (EPA), Department of Primary Industries - Fisheries, oyster farmers, MCC Water Services (rate payers, water

59 (Swanson, 2019) 60 (Williams, 1987) 61 (Bullock,, 2018) 62 (Parsons, 2010) 63 NSW Fisheries Spatial Data Portal - https://www.dpi.nsw.gov.au/fishing/spatial-data-portal 64 (Bligh Tanner, 2016)