volume 1 - Halifax Regional Municipality

Halifax Water Integrated Resource Plan
Appendices
The results presented in Table 2.10 show that under current (baseline) conditions
approximately 7.8 million m 3 /yr is discharged through the 28 outfalls addressed in the
RWWFP with an additional 1.6 million m 3 /yr. discharged through the remaining 31
active overflows. It is noteworthy that 49% of the non-growth baseline volume is
discharged to B or C risk level receiving waters while about 12% of the growth impacted
volume is discharged to B and C risk level receiving waters. The impact of growth with
no additional controls is evident with an over 100% increase in overflow volumes
between the baseline and growth with no controls cases. The preferred RWWFP
strategy however reduces the average annual overflow volume for the 28 outfalls by
16% for the total systems outfalls, thus already achieving a substantial improvement.
It is for these reasons that an Enhanced Overflow Control Program was developed and is
proposed for implementation through the IRP. A high level analysis of the Enhanced
Overflow Control Program was carried out using the following assumptions:
• Additional overflow control used a technology based on storage coupled to pumping
and secondary treatment for purposes of estimating capital costs.
• Storage was sized to capture all but 25, 15 and 5 overflow events per average year
• Pumping and secondary treatment requirements were sized to empty full storage in
48 hours
• Costs were estimated using the same procedures as throughout the IRP
(documented in Volume 3 - Appendix C).
The additional (beyond the RWWFP) capital costs to achieve a uniform level of 5, 15 and
25 overflow events for all risk levels of receiving water are presented in Figure 2.1.
Revision: 2012-10-29 Integrated Resource Plan –Appendices F-24
October 31 2012 Page 203 of 272