- Pulp Mill Effluent Outfall – Burnie
In conjunction with Consulting Environmental Engineers of Melbourne, OCEL were involved with the detailed design and development of installation procedures and monitoring of installation for the construction of a 1.0 m diameter diffuser 100 m long on the seaward end of an existing outfall in Emu Bay, Burnie, Tasmania. The pipeline was assembled on the wharf including the fitting of substantial concrete anchor blocks, and towed to site, then lowered into position over preexcavated anchor pits at the pipe anchor block locations. Anchor pits were rock filled and grouted to secure the pipeline. Connection to the existing pipeline was achieved using a diver installed steel junction box designed to
accommodate a degree of positional tolerance.
OCEL undertook the detailed design of a new wastewater outfall at Akaroa for Banks Peninsula District Council. As with many such jobs undertaken by this practice the design was strongly influenced by its applicability to a practical and economical construction method. On completion of the design it was proposed that OCEL also undertake the installation of the pipeline using company diving personnel and equipment. This was achieved successfully, the HDPE pipeline weighted and piled to the seabed for about one third of the Council’s previous estimate. The pipeline is 200 mm OD PE, discharging to Akaroa Harbour.
- WAPET Subsea Pipeline Tender
OCEL undertook the preparation of detailed assembly and installation procedures for Stolt Comex Seaway’s tender for the installation of approximately 35 km of bundled gas and product pipelines (150 and 500 NB) between WAPET’s Roller A and Thevenard Island. The work included the development of onshore pipeline assembly and launch procedures, off bottom tow method design and control, survey methods, subsea connection of towed strings, completion spool piece metrology and installation, and platform riser and valving installation and protection. The clients tender was unsuccessful. North Sea Subsea Installation Procedures
OCEL were engaged by Stolt Comex Seaway to design detailed installation procedures and substantial construction components for the installation of two 250 tonne water injection templates to be installed in 270 m of water for the Draugen Field in the Norwegian sector of the North Sea. A hangoff structure to support these components from the semisubmersible vessel Amethyst, and to assist with subsequent piling operations was designed and CAD drawings prepared and verified using ANSYS finite element analysis at the Contractor’s offices in Stavanger. Vessel response to environmental loads was assessed to establish operating limits, installation tolerances and dynamic loadings during installation. Approval of the procedure components and calculations by Lloyds was granted. On going follow up
was provided from the Christchurch office of OCEL.
Gary Teear returned to Norway to complete the offshore phase of the project as Senior Project Engineer. The template installation was successfully completed as designed using diverless remote control techniques.
- Georgetown/Temco Outfall, Tasmania
OCEL provided engineering expertise to Consulting Environmental Engineers of Melbourne in the joint development of a suitable outfall pipeline design and construction concept for an outfall to discharge combined domestic and industrial effluent to the Tamar Estuary. The outfall is required to perform in strong tidal currents which also affected the development of acceptable construction methods. The outfall of 250 mm diameter is 200 m long and discharges at a water depth of 30 m.
- Maui A-B Pipeline Options Study
In conjunction with Fitzroy engineering an alternative procedure for the fabrication and installation of the subsea pipeline to be installed between Maui A production platform and the new Maui B installation was developed. This procedure comprised the fabrication and launch of the pipeline in the sheltered waters of Golden Bay from where it could be bottom towed to the Maui site and installed. Although this procedure was not selected as the contract option it is still considered practical and economical for projects of this nature.
- Wellington City Council Outfall Options Study
Work was carried out in 1987/88 as subconsultants to Beca Carter Hollings and Ferner to investigate the options, feasibility and costs for constructing an ocean outfall in Fitzroy Bay to discharge treated wastewater from Wellington City. This project required seabed investigation, onshore survey of possible construction sites and the development of suitable construction techniques for both outfall construction and for a pipeline crossing the Wellington Harbour entrance.
- Green Island Wastewater Outfall
R W Morris and Associates Consulting Engineers Limited were engaged to develop, design and oversee construction of the outfall component of the Green Island Drainage Basin Wastewater Scheme. A new construction concept for the 500 metre long outfall was proposed following detailed investigations. The concept, which obviates the need to drive piles to secure or support the outfall, consists of twin 800 mm diameter high density polyethylene pipes connected to a flexible continuous concrete base slab, which was constructed on shore and launched by the bottom pull method to its final location. Detailed design was undertaken, contract documents prepared and tenders called. The project was completed with the final (inshore) section of the outfall launched in February 1988. The outfall discharges local body and meatworks wastes with a maximum capacity of 1.2 cumecs.
- Devonport Wastewater Outfall, Pardoe Beach, Tasmania
R W Morris and Associates Consulting Engineers Limited, in association with Dr I G Wallis, was engaged to provide specialist engineering advice to the designer of a new 1,400 metre long 0.9 metre diameter wastewater outfall at Devonport, Tasmania. Assistance has been provided mainly in the area of construction feasibility, techniques and procedures. The outfall is being built in stages by the local borough council, essentially using the dig and lay technique. An underwater diver operated excavator was utilised to dig the trench and lay the pipe. Subsequent involvement by OCEL as the staged construction proceeded included review of tenderers construction procedures and inspection and
reporting on progress during construction.
- New Plymouth Submarine Outfall
Brian Perry Limited were awarded a contract to construct a 575 metre long 950 mm diameter submarine wastewater outfall as part of the New Plymouth sewerage scheme. They engaged R W Morris and Associates Consulting Engineers Limited to provide engineering services during the planning and construction stages of the contract.
The construction alternative proposed by Brian Perry Limited involved the building of a trestle along the entire length of the submarine section of the pipeline, to provide support for a crane or hydraulic excavator digging the burial trench and to support a monorail which was used for the pipeline launch. R W Morris and Associates Consulting Engineers Limited assisted with the temporary works, including the trestle and monorail system, provided specialist advice on construction techniques, undertook design checks and provided engineering inspection services during the construction. The system proved to be so successful it was subsequently used for the construction of the new Timaru wastewater outfall.
- Maui A Submarine Gas and Condensate Pipelines
As part of an overall review of the lateral stability of the Maui A submarine gas and condensate pipelines, R W Morris and Associates consulting Engineers Limited were engaged by Shell BP and Todd Oil Services Limited to carry out a study of possible techniques that could be used to stabilise the pipelines over areas of rocky sea bed terrain.
A broad screening of possible support types was made and this showed that a concrete support was the most likely to satisfy the design requirements. It was proposed that the problems associated with pouring concrete underwater could be minimised by using an additive which enabled concrete to be poured underwater without segregation, be self levelling and self compacting.
Full scale tests of the support in two configurations were carried out at a site on the New Plymouth foreshore where bed conditions closely resembled those of the sea bed where the supports were required. These tests established the feasibility of the system and provided data for use in design calculations.
The completed report on the study discussed construction methods and presented preliminary cost estimates for using the system to stabilise the Maui A pipelines.
- Bunbury C Thermal Power Station Cooling Water System
R W Morris and Associates Consulting Engineers Limited in association with Maunsell and Partners Pty Limited, Perth, were engaged by the State Energy Commission of Western Australia to undertake a conceptual design and construction study of a cooling water system for the proposed Bunbury C Power Station. The study encompassed three intake locations and seven outfall locations together with the conduits to and from the power station. The various options were compared, construction methods evaluated and cost estimates prepared. Two preferred options for the total cooling water system were identified. The findings of this study were presented in a comprehensive report.
- Marsden B Offshore Cooling Water System
When New Zealand Electricity decided in 1975 to construct a new 250 MW thermal power station Bechtel Pacific Corporation Limited were appointed as project managers. R W Morris and Associates Consulting Engineers Limited was engaged by Bechtel Pacific Corporation Limited to design and supervise the construction of the cooling water system.
The cooling water system consisted of two 2.5 metre diameter concrete pipelines (one intake and one outlet) extending some 550 and 850 metre respectively into the ocean off the Northland coastline. The majority of the pipes were made in 10 metre lengths by epoxy/dowel splicing, two vertically cast, 5 metre long concrete sections. Joints between pipes were spigot and socket with a rubber “O” ring and the pipes were layed using a purpose built underwater pipelayer. Both pipelines were buried throughout their length and terminal structures were designed to be wholly constructed on land before towing to the site for installation. All joints, pipe bearings and laying procedures were inspected underwater by R W Morris and Associates Consulting Engineers Limited own engineer/divers. Similarly, since completion the interiors of both pipelines have been regularly inspected for signs of pipe movement, and/or joint leaking by R W Morris and Associates Consulting Engineers Limited engineers.
R W Morris and Associates Consulting Engineers Limited expertise in design and supervision was highlighted by winning the Association of Consulting Engineers of New Zealand 1981 “Award of Merit” for this project.
- Moa Point Wastewater Outfall
R W Morris and Associates Consulting Engineers Limited were engaged in 1977 by the Wellington City Corporation to carry out a feasibility study on the construction of a sewage outfall pipeline from the Moa Point area. The project involved subconsultants reports on wave conditions and sea bed structure, and sea bed diving surveys by R W Morris and Associates Consulting Engineers Limited engineers. Location, length, diameter, materials and construction methods were all evaluated and some preliminary design work undertaken. Cost estimates were prepared for four outfall configurations and recommendations made for further studies. Results from the study were presented in a comprehensive report.
- Gisborne Refrigeration Company Limited Wastewater Outfall
R W Morris and Associates Consulting Engineers Limited was engaged as subconsultants to Murray-North Partners Limited to investigate, design, and manage the construction of a new 1500 metre long submarine outfall to discharge pretreated wastes from the Gisborne Refrigerating Company Limited’s meatworks.
Following investigations, including hydrographic surveying, a site was selected for the outfall. At this site there was insufficient back room space available to joint and launch the outfall in one length or even as a number of moderately long lengths. Each of the 700 mm diameter concrete coated steel pipes was therefore flanged and the outfall was launched with bolted connections using the bottom pull negative
buoyancy method. Difficult weather conditions caused some problems during the launching operation but these problems were resolved and the outfall was secured. The outfall was commissioned in February 1978 and has been operating successfully since that time.
- Taharoa Submarine Slurry Loading Pipelines
New Zealand Steel Mining Limited required a loading system for large ore carriers at the Taharoa ironsands site on the west coast of the North Island. The company’s existing slurry loading buoy, 1800 metres offshore, had been installed in 1972 and the new buoy had to be located 3000 metres offshore to give adequate seaway for larger carriers. The planned loading rate was double the existing system of 2500 tph through two pipelines of 14 inch OD. In addition a 150 mm gland water line was specified. R W Morris and Associates Consulting Engineers Limited was appointed as consultants in 1976 by New Zealand Steel Mining to design and supervise construction of the offshore project. The successful tenderers were Brian Perry Limited, of New Zealand, and Comex Far East Limited, of Singapore jointly.
A location was selected following a study of wind and wave data recorded during four years of operations. On the selected alignment the landward projection of the offshore pipeline passed through the mining dredge pond, so that 3000 metre of pipeline had to be constructed in four separate strings. The client required the pipe to be asphalt-wrapped and further protected by an impressed current system. Various methods of protecting this wrap during installation were considered. On the basis of installed cost, concrete coating was rejected in favour of a timber skid beneath each pipe.
The existing system had been piled and frequently monitored by the client. Piling was again selected for securing the pipelines. The pipelines were clamped together by untreated bolted clamps which housed the piles and all steelwork was protected against corrosion by zinc anodes.
The pipelines, with an all up air weight of 1200 tonnes, were successfully pulled into position.The contract also included the laying of the SMB anchors and chains – 102 mm oil rig quality chain and 9 tonne Bruce anchors.
- Gisborne City Wastewater Outfall
The Gisborne City Council required a submarine ocean sewage outfall to be installed at Waikanae Beach and the contractor, Canterbury Pipelines Limited, engaged R W Morris and Associates Consulting Engineers Limited to undertake construction planning and to control installation. The Gisborne City Engineer, Mr Harold Williams, originated and designed the concept and was Engineer to the Contract.
The pipeline consisted of 2.4 metre long plain end ducted spun reinforced concrete pipes of 750 mm inside diameter and 116 mm wall, stressed together to form 450 metre lengths. The complete launching operation and the design and development of launching techniques and procedures was carried out by R W Morris and Associates Consulting Engineers Limited.
The first length was launched into the sea by the bottom pull negative buoyancy method, with the second being mechanically spliced to the landward end of the first length. This was done successively with each length until the total 1800 metres of pipeline was successfully pulled into position along the seabed, with the diffuser section resting 15 metres below mean sea level. This was the first longitudinally prestressed concrete submarine pipeline in the world.
Other outfall projects with which OCEL personnel have been associated, include:
A. Design and Construction Supervision
1. Canterbury Frozen Meat Wastewater Outfall, Pareora.
2. Rarotonga Sewerage Scheme Phase 1 Marine Outfall.
3. Whirinaki Effluent Outfall, completed 1972.
4. First Taharoa Submarine Slurry Loading Pipelines, completed 1972.
B. Preliminary Investigations/Conceptual Designs/Feasibility Studies
1. Pulp mill outfall concept studies Burnie, Tasmania.
2. Wellington City Council, Investigation of Outfall and Harbour Crossing 1987/88.
3. North Taranaki Regional Wastewater Outfall, 1983.
4. Geelong Wastewater Outfall, Victoria, 1983.
5. Kiwi Co-operative Dairies Company Limited Wastewater Outfall, Taranaki, 1982.
6. Egmont Co-operative Dairies Company Limited Wastewater Outfall, Taranaki, 1982.
7. Port Vila Petroleum Off Loading Pipeline, Vanuatu, 1981.
8. Stony Point Condensate Loading Pipeline, South Australia, 1981.
9. Aluminium Smelter Cooling Water System, Dunedin, 1981.
10. Porirua Wastewater Outfall, 1981.
11. Sydney Wastewater Outfall, New South Wales, 1980.
12. Timaru Wastewater Outfall, 1980.
13. Spencer Park Wastewater Outfall, Christchurch, 1977.
14. New Plymouth Wastewater Outfall, 1974.
15. Kwinana Offshore Cooling Water System, Western Australia, 1967.
16. Napier Wastewater Outfall, 1967.
C. Specialist Advice
1. Kawana Caloundra Outfall Mooloolaba, 1987.
2. Timaru Wastewater Outfall, 1979.
3. Nelson City Wastewater Outfall, 1970.