(4) Physical Environment (Fig. 56). 



(a) Protected Bay Environment. Location off Gulf of Alaska places site in area 

 of some of the most severe weather and sea conditions in the world. These conditions have a 

 strong influence at the site, which are also affected by the surrounding steep mountain 

 terrain (Petroleum Engineer, 1971). 



(b) Wave Conditions. 28-foot waves. 



(c) Currents. Tidal currents up to ±8 knots at entrance to Upper Met, parallel 

 to shoreUne. 



(d) Winds. In early summer, fresh northwesterly; in summer, easterly; in late 

 summer, southwesterly; mean speed 6 knots (U.S. Coast and Geodetic Survey, 1964), 

 maximum speed up to 66 knots (Petroleum Engineer, 1968). 



(e) Storm Surge and Tides. Tide range, 25 to 30 feet. 



(f ) Littoral Transport. Alternating tidal action carrying glacial silt, sometimes so 

 thick as to appear as Uquefied mud. 



(g) Water Depth at Structure. 62 feet at mean low tide (Cloyd, 1968). 



(h) Foundation Conditions. Flat stiff clay bottom, strewn with boulders up to 

 30 feet in diameter (Visser, 1969; U.S. Coast and Geodetic Survey, 1964); subject to 

 earthquakes. 



(i) Ice Conditions. Average freezeup, 10 December; average breakup, 2 April; 

 maximum thickness, 6 feet (approximate). 



(j) Temperature. Water, 29° to 55°F (Blumberg and Strader, 1969); air, -40°F. 

 (k) Earthquake. Maximum recorded, 8.7 on Richter Scale in 1964. 



(5) Basic Structural Features (Figs. 57 and 58). 



(a) Dimensions of Basic Structure (Cloyd, 1968). 



1 Platform. Two working decks, 110 by 110 feet; upper platform 19 feet 

 above lower. 



2 Support Column. 28.5-foot diameter by 125 feet high with 1-inch plate 

 end sections, and 2-inch plate in middle section. 



3 Pontoon Base. Two parallel pontoons, 20- to 24-foot diameter by 174 

 feet long, spaced at 120 feet, each secured to bottom by 8- to 36-inch diameter by 100-foot 

 piles at each end. 



4 Weight. 2,800 tons (ready to launch); 5,000 tons (approximate total). 



(b) Unusual Structural Features. Design and construction using high strength 

 steel to meet requirements of extreme site conditions of low temperatures, strong tidal 

 currents, and pack ice. Steels used were Armco Lo Temp (A537 Grade A) and Super Lo 

 Temp (A537 Grade B). Designed buoyant, so that the structure could be towed to Cook 

 Inlet, and the base flooded for sinking. After anchoring by piles, the pontoons serve as oil 

 storage tanks. After positioning, jackets having provided buoyancy are filled with concrete 

 to a point above highest anticipated ice-level for protection. 



101 



