Outfall projects present complex environmental, engineering, and construction challenges. Historically outfalls using trenchless methods have been used where traditional installation methods were not viable because of depth or ground conditions. The technical advances in the last 20 years, in both microtunnelling and HDD equipment and techniques, have now made their use viable for sewer outfalls; technological furtherance which the team at Terra Solutions embrace and utilise.
With the exception of relatively few, nearly all metropolitan areas in the world are located next to coastal waters. In addition, more than half the world’s population currently lives within 60km of a coastline. Therefore, tunnelled or directionally drilled outfall constructions are often an effective and sustainable way to improve the quality of life in coastal areas.
The advantages of trenchless installation of sewer outfalls over open cut trenching include:
- Environmental impact is greatly reduced – minimal surface disruption, lower emissions, no deterioration of seawater quality
- Impact on community & infrastructure is significantly reduced – roads, beaches and shipping can continue as normal, no disturbance of tourism, localised seabed impact
- Location of the launch site for the outfall is much more flexible; behind the foreshore, on top of a cliff etc.
- Higher lifetime of the pipeline due to less risk of settlement, higher seismic safety, cyclonic weather conditions and protection of pipeline (against shipping damage)
- Trenchless methods are less affected by bad weather, the only weather concerns are for the relatively short period during the final breakthrough and when installing the diffuser