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March 26, 2019 <br /> HWA Project No. 2015-061-21 Task 600-7 <br /> Boulevard right of way. Due to the anticipated differential settlement along the roadway, we <br /> recommend that all subsurface utilities be constructed using fused HDPE piping. Specific <br /> recommendations associated with each utility type are provided below. <br /> 4.4.1 Non-Grade Sensitive Utilities <br /> Non-grade sensitive utilities such as electrical, methane collection, communication, gas and <br /> water can be installed as grade supported utilities within the roadway. The utilities are expected <br /> to settle with the roadway over time, roughly as shown in Figure 5. All of these utilities and their <br /> associated conduits should be constructed as fused HDPE piping to increase flexibility. Utilities <br /> such as power and communication should be installed with sufficient wire slack to allow for the <br /> settlement and associated elongation of the conductor wire as the ground settles. This may <br /> require that additional wire be looped in pull boxes to allow for the anticipated elongation. <br /> Utility piping and conduits should be designed with sufficient pipe penetration into manholes and <br /> pull boxes such that they don't pull out as the ground settles. <br /> 4.4.2 Flexible Connections <br /> Flexible connections capable of tolerating large differential settlements over short distances will <br /> be required at all points where utilities transition from grade-supported to pile-supported. <br /> Flexible connections should be designed to tolerate both rotation and elongation associated with <br /> the anticipated settlements. Based on the potential variability of within the refuse, utilities could <br /> experience deflections associated with up to 30-inches of defection and 30 inches of elongation <br /> at the transition points from grade supported to pile supported. Therefore, flexible utility <br /> connections designed to tolerate rotation and elongation of up to 30-inches should be used at all <br /> points that utilities transition from grade- supported to pile-supported. Flexible connections <br /> capable of withstanding the deflection associated with less than 30-inches of rotation and 30- <br /> inches of elongation could be used. However, the design life of the connection would be <br /> reduced, the potential for connection failure would increase, and required maintenance of the <br /> connections would increase. If flexible connections capable of tolerating less than 30-inches of <br /> differential settlement and the associated elongation are used, we would recommend that the <br /> connections are constructed with access vaults to allow for easy access and replacement when <br /> needed. <br /> 4.4.3 Sanitary Sewer <br /> If the sanitary sewer system was constructed conventionally, within the roadway right of way, it <br /> would be subject to the same differential settlements as the roadway. These differential <br /> settlements would result in the development of significant sags along the sewer system that <br /> would likely impede flow and result in significant future maintenance or replacement costs. <br /> Therefore, we recommend that the sanitary sewer system be moved outside of the roadway and <br /> structurally supported by the proposed adjacent pile supported buildings. Supporting the sewer <br /> system with the pile supported buildings will allow for the system to maintain desired grades, <br /> regardless of anticipated site settlements. <br /> Geotechnical Report Revision 3 26 2019.doc 14 HWA GEOSCIENCES INC. <br />