Trenched vs. Trenchless Methods

Trenching and trenchless methods are two fundamentally different approaches to excavating and installing underground utilities or pipelines. The key differences include:

1. Excavation Method:

• Trenching: Trenching involves open excavation, where a trench or ditch is dug in the ground to accommodate the utility or pipeline. This method requires the removal of a significant amount of soil to create a trench. It is a traditional and widely used method for installing underground infrastructure.
• Trenchless: Trenchless methods, as the name suggests, do not require open excavation. Instead, they employ specialised equipment and techniques to install utilities or pipelines with minimal surface disruption. Trenchless methods are considered more environmentally friendly and less disruptive.

2. Disruption and Surface Impact:

• Trenching: Trenching can be highly disruptive to the surface and surrounding environment. It often involves digging up roads, sidewalks, landscaping, and other structures, leading to traffic disruptions and the need for extensive surface restoration after the installation is complete.
• Trenchless: Trenchless methods cause minimal disruption to the surface. Since there is no open trench, there is no need to disrupt roads or landscapes extensively. This makes trenchless methods especially advantageous in urban areas or locations with sensitive environmental concerns.

3. Soil Removal and Disposal:

• Trenching: Trenching generates a substantial amount of excavated soil that needs to be removed and disposed of properly. Soil disposal can be a logistical and cost-intensive aspect of trenching projects especially in contaminated conditions.
• Trenchless: Trenchless methods often do not generate as much excavated soil, and in some cases, there may be none at all. This reduces the need for soil removal and disposal, making trenchless methods more efficient in this regard.

4. Project Duration:

• Trenching: Projects can be time-consuming, especially in highly urbanised areas when extensive excavation and surface restoration are required. Projects may take longer to complete due to the nature of open trenching and the logistics of maintaining surface access.
• Trenchless: Trenchless methods are generally faster in urbanised areas or across complex topography for pipeline installation because they can be remotely operated and bypass problematic areas. Projects can be completed more efficiently, reducing the duration of disruptions.

5. Suitability for Different Conditions:

• Trenching: Trenching is suitable for a wide range of soil conditions and depths. It is commonly used for laying utilities in rural areas and where surface disruption is not a significant concern. Trenched excavations are generally unsupported, this can become problematic in non-cohesive geotechnical materials or excavations below the water table. In these cases trenches may collapse inwards, or require support structures which can become costly.
• Trenchless: Trenchless methods are adaptable to various soil conditions and are particularly beneficial in urban environments, densely populated areas, or locations with complex geological features. The range of different trenchless methods available have been developed to cover different geotechnical conditions and project constraints.

In summary, trenching involves open excavation and is more disruptive to the surface, while trenchless methods minimise disruption and remotely excavate and install services between one location and another. The choice between the two methods depends on factors such as project requirements, location, environmental considerations, and cost-efficiency.