34. If in accordance with the provisions of this Schedule—
(a)alternative apparatus of better type, or greater capacity or of greater dimensions is placed in substitution for existing apparatus of worse type, of smaller capacity or of smaller dimensions, except where this has been solely due to using the nearest currently available type; or
(b)apparatus (whether existing apparatus or alternative apparatus) is placed at a depth greater than the depth at which the existing apparatus was situated,
and the placing of apparatus of that type or capacity or of those dimensions, or the placing of apparatus at that depth, as the case may be, is not agreed by the promoter or, in default of agreement, is not determined by arbitration to be necessary having regard, among other things, to the nature of the authorised works, then, if such placing involves cost in the construction of works under paragraphs 9 to 12 exceeding that which would have been involved if the apparatus placed had been of the existing type, capacity or dimensions, or at the existing depth, as the case may be, the amount which apart from this paragraph would be payable to the specified undertaker by virtue of paragraph 32 is to be reduced by the amount of that excess.