Projects » Downtown Seattle Utilities & Site Work

Projects » Downtown Seattle Utilities & Site Work

Client: GLY Construction


     Installation and Maintenance of approximately 1700 LF of 6” HDPE pumping 

           system with 4” pumps to handle and convey storm water to the pretreatment

          ponds.  (All HDPE welding was performed by NWC crews)

     Installation and Monitoring of Settlement Markers on Exsiting SPU Watermain

     Installation of 1560 LF of 30” Sani-Tite HP Storm Drain Pipe & 11 Storm Drain

          Manholes (Depth varied between 20’ to 9’ in depth)

     Installation of 400 LF of 24” Sani-Tite HP Storm Drain Pipe

     Installation of 100 LF of 18” Sani-Tite HP Storm Drain Pipe and 1 Storm Drain

          Catch Basin

     Dewatering System Installation (DGS) of well points at 5’ on center for the large

          diameter storm pipe

     Installation of 140 LF of Restrained Joint Sanitary Sewer Pipe

     Installation of 100 LF of 12” Sanitite Sewer Pipe

     Installation of 260 LF of 8” RJ Watermain @ a depth of 9’

     Installation of 105 LF of 12” RJ Watermain @ a depth of 7’

     Installation of 1000 LF of Electrical & Communication Ductbanks at depths  

          requiring extensive shoring  

     Installation of approximately 700 CY of CDF (Low Strength FTB) for ductbank


     Excavation, Shoring & Backfill of two 8x14 Electrical Vaults

        Excavation, Shoring & Backfill of three 5x7x7 Communication Vaults


The demolition of an existing foundation system along with structural excavation and structural backfill initiated a parking garage project preceding several additional projects. Prior to construction of a new building, the advanced master planned site improvement utility infrastructure needed to be installed, as well as the installation of ground improvement aggregates (stone columns).  NWC performed the handling and disposal of ground improvement spoils, excavation and grading of lined settling ponds and preceded the installation and maintenance of an HDPE forcemain pumping system for site storm water conveyance.  Prior to the installation of the stone columns, utility settlement markers were to be installed on SPU’s existing water main.  NWC installed approximately 1800 LF 30” Sani-tite HP Storm Drain Pipe and manholes, sanitary sewer, water main, and both electrical and communication duct banks.


The existing site consisted of a vacant research and development facility and covers over 40 acres.  This land adjacent to the water was built by fill from the Interstate 5 excavation when the freeway was being built, using this material to fill in the existing waterways. The non-native soil (fill) and the tidally influence required dewatering in order to install the storm drainage system. NWC utilized a vacuum well-point system to keep the trench dewatered to complete the project.