For the purposes of section 99 above the discounted aggregate deficit on a public sewer is the amount equal to the sum of the estimated relevant deficits for each of the twelve years following the provision of the sewer, in each case discounted in accordance with subsection (6) below.
The estimated relevant deficit for any year is the amount (if any) by which the estimated drainage charges payable for the use during that year of that sewer would be exceeded by the annual borrowing costs of a loan of the amount required for the provision of that sewer.
Subsections (2) to (6), (8) and (9) of section 100 above (which relate to the annual borrowing costs of a loan of the amount required for the provision of a public sewer) shall apply for the purposes of this section as they apply for the purposes of that section.
Any reference in this section to the estimated drainage charges payable for the use during any year of any sewer is a reference to so much of the aggregate of any charges expected to be payable to the sewerage undertaker for the provision of services in the course of that year as would represent charges—
For the purposes of subsection (4) above, a thing is expected to be the case if, at the time the relevant calculation is made, it is reasonably likely to occur.
The estimated relevant deficit for a year mentioned in subsection (1) above shall be discounted in order to determine its net present value by applying such factor, and in accordance with such other provision, as may be determined by the Authority.
A determination made by the Authority for the purposes of subsection (6) above—