used as finger-end guide pUes. The eaves of the roof must be high enough to clear the 

 superstructures and masts of all the berthed craft at the highest water level. 



At some sites, the water may be too deep or the water level may fluctuate with too great 

 an amphtude to permit guide-pile anchorage. A cable and bottom anchor to moor the 

 floating system is then necessary. Such a system is usually more costly than a guide pile or 

 dolphin system. To maintain proper distance from the shore, horizontal displacements of 

 the entire installation will occur as the water level changes. Chaney (1961) contains a 

 description of one such system. Another scheme that may be used where the bottom is 

 more rugged, as in mountain reservoirs, is shown in Figure 91. Where this anchorage system 

 can be installed in the dry before the reservoir is flooded, the work wiU be greatly 

 simpUfied. Anchors that can be installed in deep water include massive concrete weights, 

 large boulders with driUed-and-grouted eyebolts, pulled-in ship anchors, and shot -in anchors. 



Where the surface level fluctuation amphtude is small, a system of long lateral lines with 

 sinkers or counterweights may provide for automatic adjustment to meet the specific 

 requirements of lateral positioning at different levels. In cases where adjustment is done by 

 winches, it is important to devise a system that is simple to operate and more foolproof. 

 Systems that require several adjustments to be made concurrenfly should be avoided. To 

 devise a system that requires only one winch is usually impossible, but with ingenuity a 

 two-winch system can usually be designed for all the necessary adjustments. The two-winch 

 system should be planned by a rigging expert. Steel cable manufacturers often have such 

 personnel or can recommend a qualified rigger. 



A floating dock system is common along the bank of a river or canal where a 

 unidirectional current prevails all or most of the time. Several river anchorages are possible, 

 but aU are based on the trailing sUp principle shown in Figure 7. The differences are usually 

 based on the varying methods for anchoring the system against the pull of the current. The 

 American Society of Civil Engineers (1969) shows a river anchorage system in which a 

 dolphin is used for one of the anchors. Each boat is moved into a berth against the current 

 from a downstream access. When leaving, the mooring lines are unfastened and the boat is 

 guided carefully by hand to clear all moored boats and other obstructions until it drifts out 

 of the berthing area. 



In locations where the bottom drops steeply from the bank, or where the bottom should 

 remain free of piles, anchors, and cables, a floating system may be held away from the bank 

 by double-hinged struts. Struts are generally used only for small docks and sUps because of 

 the large stresses that can be transferred to the struts and shore anchorages by small lateral 

 loads on the floating system. If the gangway can be attached to the bank at the same level as 

 that of the strut system, it may substitute for one of the struts. The hinges must be larger 

 than the ordinary gangway hinge to resist the higher tensile and compressive stresses to 

 which the struts are subjected. Because of the limited use of these systems they are not 

 discussed in detail, but included as a possible solution to a specific problem. 



146 



