volume 1 - Halifax Regional Municipality

Halifax Water Integrated Resource Plan
Appendices
Figure 2.1
Capital Cost of Enhanced Overflow Control
The figure shows a “knee” or inflection point where the marginal costs of further
reductions in overflow frequency start showing diminishing return. The “knee” in this
case occurs at about 10 overflow events per average year, which would typically
correspond to between 1-2 events per month depending on the rainfall distribution. The
additional capital cost (above the RWWFP) of the storage-pumping-treatment facilities
would be $929 million if all outfalls were included. A second step of the analysis
examined the sensitivity of the results to the level of receiving water risk. Figure 2.2
presents the cumulative capital cost to achieve 10 overflows per average year for the
outfalls discharging to each receiving water risk level. The A level has not been included
since no overflows discharge to A level receiving waters.
The figure shows that a 10 overflow per average year control level would require a
capital cost of about $173 million to control the B and C risk level outfalls. A relatively
small increase would be required to add the D level outfalls but a quadrupling of costs is
required to address all the outfalls (i.e. A to E level).
Revision: 2012-10-29 Integrated Resource Plan –Appendices F-25
October 31 2012 Page 204 of 272