We have important tunnel ventilation equipment at Lane Cover River West and Scotts Creek. If wastewater levels rise above a certain point at these sites, control gates or penstocks open and channel the overflow into the tunnel.
If the tunnel capacity nears 70 million litres in wet weather, the airflow is reversed. The ventilation fan at North Head is automatically turned off and ventilation fans at Lane Cove and Scotts Creek start up. As the tunnel fills, air is extracted by the Lane Cove and Scotts Creek fans.
Air discharged from the Lane Cove and Scotts Creek sites passes through 3 filters before being released into the atmosphere. The filters include a pre-filter, a granular-activated carbon filter and a final filter.