1 inch at any level of the water surface, a cover plate should be provided. The gangway may 

 be of any design that meets the structural requirements. Manufactured gangways that meet 

 most design criteria are available in sizes for most marina requirements (Fig. 97). Before 

 gangways are designed for an installation, cost data should be obtained from a 

 manufacturer; they can usually be purchased at less cost than would be required to 

 custom-build a gangway. 



Where the bottom end of the gangway rests on a floating deck that is restrained in 

 horizontal movement by guide piles or cables, it must either sHde or roll with changes in 

 water level. Because of the tendency of this rolling or sliding end to creep sideways and 

 severely stress the hinges at the upper end, guides are usually provided to prevent any lateral 

 movement (Fig. 98). SHding ends are used for gangways weighing less than about 500 

 pounds. Heavier gangways should always be provided with rollers and aprons. The apron 

 plates should be long enough to clear the ends of the roller guides at low water level and 

 attached to the bottom end of the gangway with a pipe-and-rod hinge (Fig. 99). 

 5. Design Criteria for Support Facilities. 



a. Utilities, Locker Boxes, and Fire Equipment. Freshwater from a municipal water 

 system or a local water supply development is normally piped out along the main walks of a 

 marina, mainly for use by boaters to wash craft and the adjacent dock area, but can be used 

 for fire protection. Where no fire hydrants are provided, a 0.75-inch line will serve about 

 20 berths and a 1-inch line about 40 berths. Where provided, fire hydrants are spaced at 

 about 100-foot intervals and serve standard 75-foot, 1.5-inch-diameter canvas hose racks in a 

 red colored firehose cabinet (Fig. 100). Local regulations will usually establish the size of 

 the supply Une, normally not less than 2 inches. In a saltwater environment, the Unes should 

 be either plastic or copper. In freshwater harbors, galvanized iron pipe may be used if 

 permitted by local regulations, and the owner is willing to accept the probable shorter 

 trouble-free lifespan of the material. Bronze hose bibbs, usually 0.75-inch diameter, are 

 provided for every one or two boats on each side of but not on the main walk. Some 

 backflow-prevention system acceptable to local authorities should also be provided. 

 Unprotected risers should not extend higher than 1 foot above the deck, and preferably 

 attached to a supporting pile, a locker box, or other dock fixture. Because the valves may 

 eventually break or wear, they should be attached to the piping by a threaded adapter at or 

 near the point of support; replacement can then be made without disturbing a soldered or a 

 plastic joint. AH risers should be brass or copper pipe rather than plastic. Hose racks will 

 help to achieve an orderly appearance of the docking area (Fig. 101). A shutoff valve should 

 be provided to each pier served. 



The landside water main serving a berthing system should be protected with a backflow 

 preventer. A positive neat appearing junction of buried and exposed lines should be 



156 



