volume 1 - Halifax Regional Municipality

Halifax Water Integrated Resource Plan
Recommended IRP and Analysis
• Demand reduction for the existing and future sanitary flows occurs through the ongoing
decline in water use whereby both residential and employment water
demand and hence wastewater generation are reduced.
• I/I reduction pertains only to existing I/I flows. Future I/I flows are determined from
design allowances that provide part of the margin of safety in wastewater systems
design. This is particularly true of long-lived assets such as pipes with a 100-year
longevity.
• For the purpose of the demand reduction assessment the following assumptions
have been made:
- Existing sanitary – 10% reduction in existing sanitary flows through water
demand reduction. This is a conservative reduction based on retrofit of existing
homes and purchase of new water efficient appliances.
- Future sanitary – 30% reduction in sanitary flows through future water demand
reduction.
- Existing I/I – 30% I/I reduction in existing I/I flows. This is consistent with the
targets set for King County Washington. 31
- Future I/I – Current design allowance.
Figure 6.5 shows the results of a capacity-demand analysis resulting in a somewhat
longer timing (2033 versus 2026) for required expansion of the Dartmouth WWTF than
currently being considered in the RWWFP. It nonetheless serves to illustrate the case
study and the nature of offsetting capital costs.
The figure shows that the total projected flow at Dartmouth with the -future flow
projected by the RWWFP would require a treatment capacity in excess of 99,860 m 3 /d
or when compared to the current capacity of 83,800 m 3 /d an expansion of 16,060 m 3 /d.
With the demand reduction strategy applied, flows are reduced by about 16% to slightly
below current rated capacity at 2046. This has the effect of deferring the expansion
requirement to beyond the planning period of this IRP.
31 Initial Infiltration Inflow Reduction Project Alternatives Analysis Report, King County
Washington, April 2009
Revision: 2012-10-29 Integrated Resource Plan 82
October 31 2012 Page 115 of 272