LARGE DIAMETER POLYETHYLENE SUBMARINE OUTFALLS

L.A. Jackson

Abstract


This paper presents the state of the art that has now evolved in Australia and shows the trend towards using high density polyethylene pipes for submarine conditions and the varying techniques and materials utilised. Prior to 1981 High Density Polyethylene (H.D.P.E.) was not produced in Australia in diameters larger than 630mm and even in the available sizes submarine outfalls were in the main constructed of mild steel or concrete pipes. In 1980 the Gold Coast City Council called tenders for the supply and installation of a 1500 metre, 1 metre diameter, outfall across the Southport Broadwater which is an active tidal estuary area. The proposed route crossed a main navigation channel and required trenching up to 8 metres into sand and sandstone. After consideration of the special requirements and high tender prices for conventional materials, Council constructed a temporary 400mm diameter H.D.P.E. outfall while the design of the permanent outfall was re-evaluated. The outfall was eventually constructed by day labour utilising a 1 metre diameter H.D.P.E. at a cost saving of approximately $1.5 million over the lowest tender price utilising steel pipes. Manufacturing facilities were imported into Australia for this job and now other large diameter submarine H.D.P.E. outfalls have been constructed in Australia and this material is now gaining acceptance.

Keywords


outfall; submarine outfall; large diameter outfall

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