What constructability factors should be reviewed before bidding for a crossing under a road, railroad, river or sensitive urban area?

Q: What constructability factors should be reviewed before bidding for a crossing under a road, railroad, river or sensitive urban area?

Before putting out to tender a trenchless crossing under a road, railroad, river or sensitive urban area, it is advisable to review the geometry of the route, the real implementation space, the quality of the geotechnical information, the presence of water, the services affected, the permits, the associated civil works, the logistics and the final acceptance criteria. In this type of actions, many changes and cost overruns are not only due to the construction method, but also to an insufficient definition of the actual execution environment. Therefore, constructability must check whether the design can be executed safely, compatible with the site constraints and consistent with the planned sequence of work. When this review is done well before bidding, uncertainties, modifications and conflicts during execution are reduced.

Before bidding for a crossing with trenchless technology, It is important to check not only whether the route is feasible on paper, but also whether it can actually be executed in the field with safety, sufficient access, geometric control and a realistic sequence of works. In this type of actions, many deviations in time and cost do not originate in the excavation method, but in an insufficient definition of the implementation, geotechnics, permits, affected services and reception criteria. For this reason, the previous review from the technical assistance and engineering area is key to detect incompatibilities before bidding.

Geometry of the layout and space available to execute the project

The first point to be reviewed is whether the geometry of the crossing can actually be built in the site conditions. It is not enough to define length, profile and cover: it is also necessary to check if there is enough space to install equipment, organize maneuvers, manage stockpiles and correctly execute the attack and reception phases. This check is particularly important when the solution requires vertical wells, The size, location and accessibility of the site determine the safety, logistics and performance of the work.

Geotechnics, water table and soil behavior

Another essential constructability factor is the quality of the geotechnical information. Before bidding, it is advisable to check whether the available soundings and tests truly represent the ground to be traversed and whether they make it possible to anticipate material transitions, fills, boulders, rock, soft soils or the presence of water. This information is decisive to make the right choice between a solution of pipe ramming or a system of microtunneling, and to assess whether the intended method is consistent with the actual risk of the crossing.

Affected services, environmental restrictions and permits

In a crossing under a road, railroad, river or sensitive urban environment, constructability depends both on the subsoil and the operational context. Therefore, before bidding, it is necessary to review in detail the affected services, easements, access limitations, possible time restrictions, environmental constraints and permits required by the owner of the infrastructure crossed. A project can be technically feasible and still not be constructible in terms of time or cost if these variables are not defined with sufficient precision.

Associated civil works and actual execution sequence

It is also important to check whether the associated civil works are well resolved and coordinated with the planned trenchless method. Constructability depends not only on the main equipment, but on everything that makes its operation possible: excavation and support, working platforms, drainage, energy, internal circulation, sludge management, assembly areas and access. If this sequence is not well studied before bidding, even a technically correct solution can generate implementation or production problems right from the start.

Tolerances, control and acceptance criteria

Another aspect that is often reviewed too late is how the finished work will be accepted. Before tendering, the criteria for shaft control, slope, depth, allowable tolerances and the required final documentation should be defined. When these parameters are not fixed at the design stage, discrepancies increase during execution and at final acceptance. A good constructability review should also anticipate how the actually executed result will be measured, validated and documented.

Why this pre-review reduces changes and cost overruns

Reviewing constructability before bidding allows to detect incompatibilities between layout, environment, permits, logistics and execution method before mobilizing equipment and civil works. This improves the comparability of bids, reduces open assumptions and reduces the risk of modifications, delays and cost overruns during execution. In complex works, this prior review is not an administrative step: it is a technical and contractual control tool from the beginning.