Post Point Alternate Outfall
This project required to replacing the outfall which conveys treated effluent water from the Post Point Waste Water Control Facility to an offshore discharge point in Bellingham Bay (Puget Sound). There were three (3) main components to this project: 1) perform modifications to the effluent tanks at the treatment facility to allow for the new pipeline alignment and controls, 2) installation of the land portion of the outfall, and 3) installation of the marine (offshore) portion of the outfall. The landline consisted of 650 LF of 60” Reinforced Concrete Pipe (RCP) and three (3) 10 ft diameter manholes. This required an extensive dewatering and treatment package, settlement monitoring, installation under active mainline railroad tracks (jack and bore) and through Marine Park (owned by the Port of Bellingham).
LARGE DIAMETER HDPE MARINE PIPING
The most unique component of the project was assembling and installing the marine pipeline. This required fusing 620 LF of 54” HDPE pipe and fittings (elbow, access tee, blind flange, and 54” Tideflex Valve) on shore. To fuse this diameter of pipe required a McElroy MegaMc No. 2065 fusion machine (only 11 of these machines were known to exist in the Country at this time). The welding was performed by a certified large diameter butt-fusion technician provided by Forrer Supply Company. With support from Strider, the fusing operation was completed; start to finish, in two (2) days.
After assembly the pipeline was deployed offshore, fitted with ballast blocks for weight, and sank into place (depth approximately 30 ft deep). The installation required temporarily relocating many aquatic plants (eel grass), underwater trenching, backfilling, and restoration. In addition to our forces as the general contractor, installation of the offshore pipeline required a marine contractor (General Construction Company), several underwater divers, and a team of engineers and scientists.