Abstract:
An increase in cost overruns of the water distribution network projects can lead to severe inaccuracy in budget planning, lack of material provision, and failure to deliver the project within scheduled completion time and within the desired quality. Hence, the success or failure of any project is governed by several factors, largely depending on the accuracy of cost estimation in the early stages. To achieve this goal, three objectives have been set as follows; identify and evaluate the factors affecting the accuracy of the cost estimates in the water distribution network projects through a questionnaire and by implementing a statistical “Importance Index (IMPI) approach to rank the factors based on a Frequency and Severity Analysis; introduce and develop an Artificial Neural Network (ANN) model to analyze the relationship between the cost overrun and the factors affecting the cost estimate and finally, implement a comparison to analyze and discuss the factors in regards to the results of the statistical approach and the ANN Model. Accordingly, with the support of a literature review on related topics, a questionnaire has been developed to get the required research data. A total of 57 completed responses were collected and analyzed. The first part of the analysis is a descriptive analysis of the respondent’s attributes. The second part consists of ranking 26 factors using the Importance Index (IMPI) approach in regard to Frequency and Severity analysis. Moreover, interviews were made with WDD’s project engineers to rank the factors for 35 completed projects. Accordingly, an Artificial Neural Network (ANN) model using a Multi-layer Perceptron network was developed and trained to derive the best model to determine the factors causing cost overruns. Results showed that geographic conditions, not accurate site investigation/survey, additional unplanned work/change in scope, project urgency, unforeseen events/conflicts, padding of the estimate due to uncertainties, estimator’s insufficient knowledge/understanding of the network features/components, time allowed for the estimator to prepare the cost estimate, not clear and detailed design drawings, project is in coordination with other utilities, and material availability are the top factors affecting the cost estimate of the water distribution network projects.