Colorado Public Works Journal, Spring-Summer 2020

Spring-Summer 2020 51 question of how to locate the drilling rig, in the middle of the run, considering the narrow easement and steep rocky terrain. To minimize cost, and to eliminate the need for a second mobilization, the two sections were combined into a single 3,700 foot drill. Brierley Associates were brought in to evaluate the geotechnical as- pect of the longer HDD run, IFR calculations and pull force calcula- tions for this option. With questions surrounding the viability of this option, considering the change in elevation and the sandstone and alluvium profile of the area, the decision to move to a single drill was innovative and challenging, but also effective for reduced distur- bance and increased potential for time savings. With good data to support the single drill, the project scope was altered. The new plan, for a single 3,700 foot drill, incorporated a 10-inch OD HDPE pipe, which would be installed as a single length of pipe. Onward and Upward In early March, Global Underground Corp mobilized to the Wood- moor site, and began the water line installation process. Situated at the bottom of the hill, the drilling crew began drilling for the water line. This automated process, has proven to be efficient and relatively problem free for the Well 21 project. However, like every project, there have been challenges to overcome. The drilling crew was further challenged by the sandstone and sandy soils that they were drilling through. The presence of sand in the drilling fluid caused rapid wear on the equipment used in the drilling process. The additional sand was not unexpected, but did demand alterations to how the drilling fluid was managed, and additional equipment was needed to complete the pilot hole. The project did experience some delays due to weather, but it was pointed out by Mr. Shaffer that one of the biggest benefits to HDD is that it is a process that can be done in the winter. Trenching in the winter is generally difficult, even in normal soils, due to frost. Because HDD can be done below the frost line, and especially at the depth necessary for this water line, work was able to progress, despite cold weather and snow. The Benefits The Well 21 water line is expected to be on line in late May or early June. This timing is perfect for providing additional raw water supply, during higher demand summer months. However, Woodmoor staff shared that there are other benefits to the HDD portion of the project, including the ability to complete pipeline installation during the win- ter, and minimal impacts to the environment, and zero encroachment on private properties. The HDD portion of the Well 21 project was completed on March 23, 2020. The rest of the pipeline is expected to be completed by June 1st, 2020. Final completion of the entire project is anticipated to be June 15th, 2020. Despite the newest challenges presented by the global COVID-19 pandemic, this project is moving along well, and is anticipated to be complete on schedule and within budget. The Well 21 project ran through a narrow easement, which was only about 20-feet wide in some places, between homes. The decision to install the water line by HDD allowed the Utility to avoid numerous customer disruptions, removal of trees, removal of fences and other encroachments, and the existing natural landscape was preserved as well as heightened probability of a project completion date on time or sooner than expected. These benefits, were incredibly important to gaining public buy-in for the project. They were also important factors considered by the District Board when selecting a project scope that was not the easiest option nor the lowest priced.

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