Blackburn Wastewater Treatment Plant Upgrade Study

Section 1.0 -Project Background and Objectives
Physical characteristics of the underground piping (old/new/materials).
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Connection policies (roof drain connections, etc.).
Review of wet weather flow mitigation policies and plans is essential. Should a
reduction program prove practicable and cost effective, lower peak flows would occur
after changes are implemented and thereby defer expanding plant infrastructure.
1.7.6 Wet Weather Flows
As detailed in the Stantec Consulting Ltd. report completed June, 1999, VI is a serious
problem in the Blackburn sewage collection area and corrective action is required.
The original 1976 design information for the Blackbum treatment facility lists the
following criteria:
rn Contributing population 2,500
ADWF, m3/d 945
In the future, as development exceeds 2,500 population, the facility would be doubled
in capacity to accommodate a population of 5,000 with ADWF doubling, but PWWF
remaining constant.
Based on these design parameters, the lagoon facility would provide an eMuent
quality of BOD6 20 mg/L and TSS< 20 mfl. Monitoring data from the City
indicates that the facility up to now has reliably achieved these two targets and is in
compliance with pennit requirements.
It is important to note that the original design appears to have taken into consideration
not only winter operating conditions, but also identified flow variations due to winter
thaw conditions and spring raidthaw conditions. In the first stage of development,
during wintedspring thaw conditions, because of the layout and locations of manholes
and the coliection pipework, PWWF would be high, amounting to nearly 4.5 times
ADWF, primarily because of inflow due to flooding around manholes adjacent to
natural drainage streams. A second component would be due to infiltration due to wet
ground andtor high groundwater conditions in Iow lying areas. In the second stage of
development, UI would be reduced so that PWWF would remain at 4,350 m3/d and the
PWWFlADWF ratio reduced to approximately 2.5.
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