Swansea Channel Maintenance Dredging

Maintenance Dredging and Beach Nourishment

Principal: NSW Public Works

Location: Swansea Channel, NSW

Contract Value: $1,500,000

Completion Date: January 2015

Swansea Channel is the marine gateway to Lake Macquarie on the New South Wales (NSW) Central Coast. Creating and maintaining a more reliable boating access to the lake was considered desirable for social and economic reasons. Neumann Contractors was selected by New South Wales (NSW) Crown Lands to undertake a larger scale “once off” maintenance dredging campaign to achieve this, with smaller subsequent campaigns for ongoing maintenance.

Scope of Work

The aim of the dredging campaign was to create a stable navigation channel to reduce the frequency of periodic follow-up dredging. All sand dredged from the channel was pumped to a designated area at Blacksmiths Beach where it was de-watered & spread as part of beach nourishment & dune rehabilitation works.

  • Dredging a 60m wide channel 3.5m deep
  • Transfer of approximately 80,000m3 of sand up to 3.5km to Blacksmiths Beach

Challenges

  • Presence of sensitive environmental ecosystems
  • Involvement of numerous stakeholders and interest groups;
  • Proximity to local residents;
  • limited time frame to complete the dredging
  • Installing 3,500m of pipeline from the Channel to the beach including an 80m section through an existing box culvert
  • Pumping the material up to 3,500m through a series of booster pumps
  • Spreading the material evenly along the beach at the nourishment
  • Maintaining safe navigational access for all boating traffic in this very popular and busy recreational waterway.

Swansea Channel Gateway to Lake Macquarie 

Extract from Dredging the Swansea Channel by NSW Trades and Investment Crown Lands (written prior to works)

Macquarie is a major recreational asset for residents and visitors. Lake Macquarie is widely recognised as a premium recreational waterway. Much larger than Sydney Harbour, with expansive reaches and steady wind conditions for sailing, smooth waters for wake boarding and skiing, multiple bays to cruise and explore, uncrowded natural shorelines and protected moorings for picnics and holidays.  Swansea Channel is the marine gateway to Lake Macquarie, connecting an otherwise enclosed estuarine system to the sea.  Safe passage through Swansea Channel provides opens access to ocean sailing, connecting lake sailors with the broader yachting community.  It also ensures an accessible safe haven for vessels to avoid pending storms.  In recognition of the waterway’s importance the NSW Government is undertaking a large scale dredging project to deliver a safe navigable channel.

Channel Form 

The proposed channel form is shown schematically in Figure 1 and is designed to provide adequate under keel clearance for vessels drawing up to 2.5 metres and an allowance for progressive sand infilling.  To achieve a channel base width of 60 metres, depth of 3.5 m below approximate mean water level (0.0 m AHD) and stable side slope, up to 100,000 cubic metres of sand will be dredged from the channel over a distance of 1.8 kilometres. Ongoing smaller periodic dredging campaigns in future years would be carried out as required to maintain the channel form.

Figure 2 shows the areas within the preferred alignment where sand is to be removed to meet required channel widths and dredge depths.

Large Scale Maintenance Dredging 

The once-off Large Scale Maintenance Dredging Campaign will start in November and is expected to be completed by late December 2014. The project will be delivered by NSW Trade & Investment Crown Lands with funding from Transport for NSW. The dredging activity will be carried out as follows: Late October 2014 Set up of dredge equipment and establish a contractor’s compound (Naru Point carpark) Install temporary dredge pipeline to carry sand from Swansea Channel to Blacksmiths Beach. The pipeline will be laid within existing stormwater channel under Naru Crescent and Pacific Highway. Construction of a dewatering area at Blacksmiths Beach Early November 2014 to late December 2014 Dredge up to 100,000 m3 of sand The sand will be used to nourish and reconstruct the dunes on a section of Blacksmiths Beach. This entails dewatering of the sand/water slurry, shaping the dry sand into a dune using an excavator and/or small dozers. Once the new dune shape has settled, then revegetation can begin.

End of Extract from Dredging the Swansea Channel by NSW Trades and Investment Crown Lands