As in all construction projects, the success of the project is largely dependent on the quality of the planning and preparation for the job. A study on the importance of planning in the construction industry quantified the influence of planning by showing that well-planned jobs come in 3% below budget while poorly planned jobs average 13% above budget. They also tend to be 3% ahead of schedule compared to 21% behind schedule with a much lower percentage of change orders.
These figures highlight the importance of planning in construction, and the complexities of trenchless projects amplify the negative impacts of bad planning and preparation.
Here are some simple steps for planning trenchless projects:
1. Project Scope
Clearly defining the scope of work is the first step to any successful trenchless construction project. The length of pipeline, product to be carried by the pipeline, the preferred material of pipe (e.g. Concrete, steel or plastic) and the expected route of the pipe all form part of the scope and help the contractor to understand the extent of the project.
2. Geotechnical Investigation and Report
Once a scope of work is defined, it is important to gather as much information as possible about the ground conditions and anything that can impact the ability to execute the project.
Geotechnical engineers use various techniques to identify potential underground hazards. Test wells are dug at various points along the route to obtain soil samples for analysis in a process called a geotechnical investigation. This investigation produces information that is then gathered into a report that informs engineers about the most appropriate trenchless technique for the conditions at hand.
Ground Penetrating Radar surveys help to identify other underground installations to prevent accidental intersections. During this phase, previous project files should also be examined to investigate the location of other installations as well as any problems they may have encountered during the execution of those projects.
A geotechnical report is compiled, which is used to help engineers make major decisions, like which trenchless method to use, what shoring will be required and how to overcome any groundwater issues.
3. Safety Planning
Safety plans should be developed before any construction activities are begun. Based on the geotechnical report and the decision about which trenchless method will be used, potential hazards can be identified along with appropriate steps to mitigate the risks. (Learn more in "Trenchless Operations Safety Do’s and Don’ts.")
A risk assessment is conducted along with the safety plan that covers safety and project risks. By identifying these risks up front, appropriate plans can be put in place to minimize their impact on the project should they materialize.
Safety plans should include a description of the shoring requirements for entry and exit pits. Site layout plans should be developed so that clear areas can be demarcated for storing lengths of pipe, crane locations, control rooms for monitoring the project etc.
Details of the need for workers in the entrance pit or inside the tunnel itself should also be defined. Workers should be well trained with regard to the hazards of the job and be supplied with all the required personal protective equipment (PPE)
4. Deviation Planning
In every project, complexities may be uncovered during execution that were not taken into account in the original plan. This can include unexpected changes to the ground conditions that were not picked up in the geotechnical report, or an encounter with another underground system that was not identified before, the latter is known as cross boring.
Each time a change to the original plan is required, the same level of planning must be applied to the new circumstances as was applied to the original plan. A new routing may be required because of the problem identified, but contractors should not rush ahead into this change without getting new geological information and a new assessment of safety risks.
Only when the deviation from the original plan is properly scoped and planned can the execution be carried out.
5. Contingency Planning
Contingency plans are alternative plans that are developed should any of the risks identified during the risk assessment materialize. These plans are put together right at the start of the project so that all the required actions are already prepared and can be executed with a minimum disruption to the project.
Examples of contingencies that should be planned for are drilling equipment failure (e.g. Is there enough technical expertise on site to repair it? Where will a replacement come from?), power supply failure (e.g. Is there a generator on standby?) etc.
Updating the Plan
Once a project begins, the day by day execution of the plan always deviates to a certain extent due to the practicalities of the job, rain delays etc. Projects are executed well when the plan is updated on a daily basis to reflect the progress to date and the constraints that are being experienced.
In this way, future bottlenecks can be identified early and extra resources can be allocated to keep the project on track. The better the plan and the better the day by day monitoring of the project, the more successful a trenchless project will be in terms of schedule, budget and safety.