| The number of construction change orders has been increasing and they have become a time consuming and costly element in construction projects. Combined sewer overflow construction projects in the Detroit area have suffered numerous change orders leading to cost and time overruns. 12 combined sewer overflow construction projects experienced 208 change orders. These change orders were utilized to survey different causes of change orders, the frequency of their occurrence, the cost of change orders, and the time extension attributed to these change orders. Of these 208 change orders, 180 were additive change orders, and 28 were negative change orders. Cost escalation due to additive change orders for these 12 projects totaled {dollar}14,161,956, which is 7% of the total original cost of these projects. On the other side, cost reduction due to negative change orders totaled −{dollar}2,118,478.06, which is only 1% of the total original cost. It was observed that of the 180 additive change orders, 167 were additive change orders leading to cost escalation and, 33 were additive change orders resulting in time extension. The average time extension was 30% of the original project duration and the average cost escalation was 7% of the original project cost which demonstrate that change orders can affect significantly the original project cost and duration. It was found that there is a moderate degree of variation when the relationships between cost escalation and original project cost were examined. It was observed that quadratic relationships provide high correlation. Additional work, design revisions, and differing site conditions were the main reasons that had significant impacts. The most frequently reasons were: additional work (98 of 180); design revisions (40 of 180); and differing site conditions (15 of 180) and the most costly reasons are: additional work (48%); design revisions (31.9%); and Differing site conditions (7.8%). 22.3% of total time extension additive change orders was due to schedule modifications. It was found that the most frequently work disciplines were civil work (78 of 180); mechanical work (43 of 180); and electrical work (21 of 180). The most costly work disciplines were: civil work (57.7%); mechanical work (15.9%); and electrical work (10.2%). 29.3% of total time extension additive change orders was attributed to civil work. An additional 23.8% of total time extension was attributed electrical work. The most frequently project parties generating change orders were: the engineer (92 of 180); and the owner (63 of 180). The engineer generated 47.1% of the total cost escalation, and the owner generated 43.1%. 55.4% of total time extension additive change orders was generated by the owner. The present study also suggests several essential steps the owner, the engineer, and the contractor can take to avoid and minimize risks of change orders. |
