reference plane elevation usually mean low water and take the necessary soundings in order to establish a profile of the water bed in the area of operation an exavation will then be made from a predetermined point established by the physical dimensions of the undertaking and extending to point 12 located above the level of the high water mark the second step will be tunnel under the water as indicated the extent of this operation being determined by the profile of the sea bed as previously established all work will be in conformance with approved engineering practise and observance of existing safety regulations in this operation the design depth of the channel will be exceeded by a sufficient amount to accomodate the material 13 which will be displaced by the blasting or other approved method this being part of the third step the third step contemplates the placing of explosive charges 14 as indicated which upon being detonated will cause the collapse of the material 13 which will be deposited in the space 15 provided by the additional exacavation beyond the designed channel depth the channel will now extend from the innermost point of exavation to a point offshore where the designed depth and natural depth coincide while in some case it may be practical to detonate all charges simultaneously individual studies will be made of each project in order to establish a pattern and sequence which will promote the success of the.