2015 Issue

48 Backfill Materials. Based on the geotechnical investigations com- pleted it was apparent that much of the pipe zone backfill material would need to be imported. This can represent a significant amount of the construction cost. During the design phase the contractor was able to identify local sources of material and actually provide submittals on the characteristics of available materials. This meant during the construction phase there was no arguing or question- ing of the backfill materials that would be considered acceptable. Traffic Control. For pipeline projects designed in traffic congested roadways it is not uncommon for the design en- gineer to provide preliminary traffic control drawings, detour routes and specifications that outline the contrac- tors requirements and constraints for maintaining traffic during construction. This is primarily done to establish working limitations, and traffic control requirements that will be enforced during construction. For a traditional design bid build project, the final details of the traffic control and detour plans are left for the contractor to negotiate with the jurisdictional agencies during construction. The CMGC delivery approach al- lowed the contractor to prepare traffic control plans and obtaining the city’s approval prior to the award of the construction contract. This eliminated the pricing risk associated with traffic control and also provided early information to the public involvement team that could be used to help prepare residents for construction. Negotiation and Review of Open Book Construction Costs. Dur- ing the design phase the Contractor provided open book cost estimates at the 30 and 60 percent design phase and a GMP fol- lowing the 90 percent submittal. The design engineer also provided independent cost estimating at each submittal phase. The District elected to not share the details of engineers cost estimate with the contractor but indicated to the contractor if they felt certain items were priced fairly or not and also indicated if they desired to reduce costs of major components of the project. The contractors open book costs allowed the District and their design engineer to see in detail how the contractor was pricing the work and provided opportunities to work with the contractor to identify potential cost savings as well as adding value to certain aspects of the project. Some of the cost saving ideas included backfill material selection, insurance and bonding requirements, and assigning final road res- toration requirements to Layton City who had already established a low cost paving contract with another contractor. Added value items included the use of higher quality isolation valves, increas- ing the diameter and pressure class of the HDPE pipe installed at the Hobbs Ravine Crossing, and setting aside contingencies for unknown utility conflicts and relocations. Figure 10 below shows the engineer and contractor’s costs estimates during design phase. Figure 10. Engineer and CMGC Construction Cost Estimates SUMMARY AND CONCLUSIONS Many of the critical drinking water facilities installed along the Wasatch Front have reached or exceeded their intended design life and are starting to fail. Rehabilitating and replacing the East Layton Pipeline presented significant challenges due to the fact that the pipeline could not be taken out of service for extended periods of time. This represents a similar situation for most major pipelines that serve as the backbone of water infrastructure systems. Over the last 50 to 60 years residential development along the pipeline corridor has greatly reduced the ability to access the existing pipelines for maintenance, repairs, and replacement. Replacing the East Layton Pipeline on a new separate alignment allows the District to meet water demands for the next 10 to 15 years and the opportunity to take the old pipeline out of service for repairs and rehabilitation. Once the old pipeline is rehabilitated a parallel pipeline systemwill provide the District with more reliability and redundancy to meet water demands for the next 50 years. Using the CMGC project delivery approach the District was able to engage an experienced design engineer and contractor that were able to address significant project challenges associated with constructing a large diameter pipeline through residential streets. Together the project team was able to identify cost savings and added value ideas throughout the design and construction phase that allowed a quality project to be completed within budget and without major surprises or cost increases during construction. Figure 9. Pipeline Construction in Residen- tial Streets CULINARY PIPELINE | continued from page 47