The project added a diffuser section to the existing outfall pipe for the Guam Waterworks Authority treatment plant.

As part of this project, Makai simulated the deployment of this system in approximately 150 ft water depth. From the simulation results, we worked closely with the contractor to develop the methods to safely deploy the system. The deployment team was successful in installing the diffuser section, and the outfall is fully operational.

See a video covering the deployment of this system here.

Makai worked directly for the marine contractor, Tideway (DEME), to provide final designs and installation guidance. This seawater supply system is designed to serve what will be one of the world’s largest natural gas-fired power plants. Design of the intake structures was driven by their shallow depth (5 meters) and the fact that breaking waves were present in the area. Makai was responsible for HDPE pipeline and installation specifications, intake system hydraulics including computational fluid dynamics analysis, intake tower and anchoring concrete structural designs and specifications, and contractor support during installation including design of lifting and staging assemblies.

The Lake Oswego Interceptor Sewer (LOIS) project, protects the water quality of Oregon’s Oswego Lake through seasonal changes in water temperature and in the event of an earthquake. The project replaced a 50-year-old corroded, undersized, and seismically vulnerable concrete cylinder sewer pipe under the lake with a larger, flexible, high-density polyethylene (HDPE) pipeline. LOIS is the first known buoyant gravity sewer in the world. LOIS’ submerged, buoyant stainless-steel access points provide entry points to the pipeline without affecting boat navigation, and the installation of removable access caissons allows cleaning and inspection equipment to be inserted into for infrequently required maintenance. Makai modeled and performed analysis for a 42-inch HDPE submerged, buoyant sewer interceptor. Makai used OrcaFlex to model the tension and stresses in hundreds of components (especially the tethers) to a very high degree of precision; the grade tolerance on the project was plus or minus ½ inch over several miles. Makai performed this work for Lake Oswego, Oregon and Brown and Caldwell Engineering. The project won two national awards. The Plastic Pipe Institute declared the Lake Oswego Sewer Interceptor Project as its Municipal Project of the Year, and the Association of General Contractors awarded their 2011 Grand Award to Advanced American Construction, Inc. for their work assembling the project.

The deep (115 meter) intakes provide cold water for air-conditioning buildings in downtown Toronto and the municipal drinking water system with a maximum capacity of 58,000 tons. The system provides water of higher purity than is provided by the current intakes that obtain water from shallower depths. Each HDPE pipeline is five km long and 1.6m (63″) in diameter. The pipelines were installed during the summer of 2003.

Makai has engineered the main seawater supply source for the Hawaii Ocean Science Technology Park (HOST Park) at Keahole Point, Hawaii. This supply system consists of a cold-water pipeline (55″ diameter, 3000′ deep, and two miles long), a 55″ diameter warm water intake pipe, a tunneled shoreline crossing, and a shore-based pumping station. The system is the world’s largest and deepest cold-water pipeline and has the capacity to deliver 27,000 gpm of 4 deg. C. water and over 40,000 gpm of warm water to the technology park. Makai received a national award from the American Society of Civil Engineers for this project as one of the six most outstanding CE projects in 2003.

Tafuna Outfall:  This polyethylene pipeline installed in 1996, is 24″ in diameter, 1500′ in length and extends from the shoreline to a depth of 95′. The pipeline is anchored along its entire length for protection against frequent hurricanes and the large waves and strong currents that accompany them. The anchoring systems used were a combination of rock bolts and Manta Ray sand embedment anchors.

Utulei Outfall:  This was a very challenging pipeline design and installation because of the extreme slope that existed along the course of the pipeline. The outfall pipeline is 24″ in diameter, 350′ in length, and it begins at the reef edge at a depth of 5′ and plunges to a depth of 165′. The pipeline has a free floating catenary section that spans the steep slope, and it is heavily anchored at the bottom in deep water.

Aunu’u Outfall:  This is a 6″ outfall, 400′ in length, designed to serve a small community of approximately 400 people. It is installed across a heavily exposed reef flat which is subject to high waves and currents. The pipeline is partially buried and is anchored to the reef with rock bolts.

Pago Pago:  In 1991, Makai designed and managed the construction of a long, medium depth outfall in Pago Pago Harbor, American Samoa. This 16″ polyethylene pipeline is 8500′ long and discharges near the mouth of the harbor at 176′ depth. It carries waste water from the Starkist Samoa and the Samoa Packing Tuna Canneries. The pipeline was installed using the controlled submergence techniques and was accurately laid on a curved route along the edge of the harbor. Concrete covers were designed to protect the pipeline at isolated locations from ship anchors and harbor traffic. The lifetime of the pipeline was maximized by minimizing the use of exposed metallic parts in the underwater construction. The pipeline was designed and installed in a short period and was completed ahead of schedule and well under budget.

Working under a subcontract to Hawaiian Dredging and Construction, on a NOAA/DOE program, Makai was responsible for the concept development, design and deployment planning for an 8′ diameter down-the-slope OTEC pipe test. Part of the test was the demonstration of diver-free installation techniques suitable for very deep, large diameter pipelines on the steep, 42 degree slope. The concept included a flexible pipe joint that conformed to the bathymetry. Pipe deployment was successfully accomplished as planned using heavy lift barges and closed-circuit underwater television. The design included instrumentation for the measurement of hydrodynamic loads on the pipe after installation. Makai subsequently analyzed the hydrodynamic data from this test project.

This project was a full demonstration of Ocean Thermal Energy Conversion (OTEC) and jointly funded by the State of Hawaii, Lockheed, Dillingham and Alfa Laval. Makai designed a 2′ diameter polyethylene pipe that served not only as an intake pipe from a 2000′ depth, but also as the “mooring line” for the 120′ x 35′ barge. The initial design for the barge layout, seawater intakes (cold and warm), effluent lines, and pumps was also done by Makai. Makai developed and planned the deployment scheme and participated in the at¬sea deployment. On August 2, 1979, Mini¬OTEC produced 50 kW of power and consumed 40 kW, for a net positive output of 10 kW. This was the first time that a positive output had been achieved from any OTEC facility. In 1980, the National Society of Professional Engineers awarded Mini-OTEC as being one of the ten outstanding engineering achievements in the United States that year.