Conservation of shipping space and tonnage, as well as of on-site labor, was accomplished by providing manhole shells of prefabricated corrugated galvanized iron as a substitution for brick manholes constructed in place, Manhole shells varied in diameters and heights sufficiently to permit nesting of several shells for shipping and handling as one package. The factors contributing to the selection of the method of disposal of sanitary sewage and to the design of subaqueous out-fall lines were outli ned in the Reconnaissance Report, and are partially reproduced in this section because of appropriateness: "OceanCurrents. From available information and from observations made on the site, it has been determined that, in general, the ocean currents in the vicinity of the atoll are predominately from east to west, and tend to sweep across the atoll in this direction. These currents are of lesser magnitude in areas wherein the coral reef is unbroken. Between the islands of Japtan and Parry is a section of broken reef which is known as the Deep Passage, the water having sufficient depth to safely accommodate the largest of ships. Across the lagoon almost direetly west of the deep pass~ age is a shallow opening through the reef, and which is designated the Southwest Passage, while between these two gaps on the south end of the atoll is a third opening called the Wide Passage. The Wide Passage has considerable depth and provides a convenient outlet for flows entering the lagoon through the Deep Passage. The direction of this flow is advantageous for the disposal of sewage into the lagoon, especially as applied to the Islands of Parry amd Eniwetok, the points of greatest concentration. Otherwise the currents tend to sweep the atoll circumferentially in a westerly di- rection, Sewage fram shot island installations will consist of slight volumes, and the general remoteness of these islands from other islands of habitation eliminates much of the hazard of disposing of sewage into the lagoon. SubaqueousOutfal)]Sewers. It is contemplated that each island installation will require one or more subaqueous outfall lines to extend the point of discharge of sewage a sufficient distance from shore to preclude any possibility of the periphery of the sleek field from reaching the shore and consequently subjecting the beaches to bacterial contamination, Competent authorities on sew- age treatment and disposal have determined that the area of a sleek field is related to the contributing population. From the accepted formula, the area of the field for a population of 600 is approximately seven acres. Assuming the shape of the sleek field to be circular and discounting any distortion of shape due to in- fluence of ocean currents, the radius of this sleek field would be 310 feet. The length of outfall should then exceed 310 feet as measured lagoonward from the water's edge at periods of low tide. The ocean or tidal currents, unquestionably will tend to move the entire field off-shore, but nevertheless, it is considered advis- able to allow a factor of safety of 50% of the radius of the field 5-198