Project Resource Planning

The most effective approach in this scenario is to assign the task to a team member with the required technical skills and provide mentorship for leadership aspects. This solution is optimal because:

1. It utilizes existing team members, which is crucial when resources are limited.
2. It ensures the technical aspects of the task are handled competently.
3. It provides an opportunity for skill development in leadership, which can benefit the team in the long run.
4. It balances immediate needs (technical expertise) with long-term growth (leadership development).

Dividing the task between two team members could lead to coordination issues and may not be feasible with limited resources.

Assigning the task to the most senior team member regardless of their skill set is risky, as they may lack the necessary technical expertise.

Creating a new role and hiring an external expert is not a viable option when resources are limited and would likely be too time-consuming for a critical task.

This approach aligns with project management principles of resource optimization, skill development, and effective task allocation.

The correct answer to this question is Bottom-Up Estimating. It's crucial when unexpected changes in the project's parameters come into play such as the change in the soil type in the question. Bottom-Up Estimating begins with the smallest individual tasks and then continues with estimating greater chunks of the project, thus it allows easy accommodation to changes or differences in conditions from initial assumptions. Expert Judgment and Three-point Estimating methods are less suitable for this kind of situation. Expert Judgment is a top-down approach where higher-level project details are estimated first which makes it difficult to account for unforeseen changes. The Three-point Estimating technique is useful when there are uncertainties in estimating task duration but it does not consider resources which is a key factor in this situation. Lastly, Parametric Estimating is also not the best option as it's based on statistical relationships between historical data and other variables. It's not as effective if an unexpected variable such as a change in soil type comes into the picture that wasn't in the initial conditions and comparisons.

In this case, the best method to revise the resource estimation is 'Bottom-Up Estimating'. This technique is used when the details about individual tasks are used to estimate the total project time and cost, which is applicable in situations where initial estimates have been overly optimistic. 'Parametric Estimating' could also be used, but it requires historical data and statistical relationships between variables which may not be readily available. 'Analogous Estimating' is less accurate as it is based on the comparison of similar past projects, and may not account for specific differences in the current project. 'Three-point Estimating' is less suitable because it is more complex and relies on estimating the best, worst, and most likely scenarios, then averaging these out, which is time-consuming and may not adjust the current estimates accurately.