001-40 WC 139 NOV-DEC24 PAPERTURN - Flipbook - Page 34
Location of Watershed with Regional Trunks and WWTP
The key objectives of this study include the following:
Unlock capacity for growth
Improve climate resilience
Adapt to sea-level rise
Reduce CSO in both short- and long-term
Improve discharge water quality
To achieve these objectives, a comprehensive and data-driven
planning approach was used. GHD Limited worked with the
City to develop a scope of work and methodology that includes
multidisciplinary studies, complex hydraulic modelling using
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WATER C AN ADA • NOV EMBER/ DECEMBER 2024
InfoWorks ICM, and geospatial multi-criteria analysis (MCA)
using GHD’s InDeGo model. The supporting studies include
a desktop geotechnical study of the entire sewershed to inform
risk and opportunities for sewer trunk design and blue-green
system implementation. In addition, a shoreline environmental assessment and Archaeological Overview Assessment (AOA)
have also been completed to provide guidance on the design
and potential ecological restoration for the outfall areas and
identify key locations that may have significant archaeological
values. All together, these allow the City to integrate and select
the appropriate stormwater management options and trunk
alignments that consider other partners and important inputs
outside of the hydraulic performance of the system.
The InfoWorks ICM model development for this study
requires complex geospatial data analysis in GIS and transformation of the City’s legacy PCSWMM model. The model
includes a total sewershed area of over 985 ha and 213 km
of sewer pipes. The existing sewer system is highly complex,
which includes three types of sewers and service connections,
namely combined, storm, and sanitary sewers. The accurate
representation of the connection types and hydraulics greatly
impact the accuracy of the model. Based on that, each parcel
is modelled as two subcatchments, namely storm and sanitary
subcatchments. Each parcel subcatchment is assigned with
population and runoff properties extracted from available data
such as census data and imperviousness per cent based on analysis on orthophoto and LiDAR data. The model was calibrated
WAT E R C A N A D A . N E T
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The impending growth coupled with legacy issues of combined sewers and impending climate change effects have created
significant challenges for the City in terms of providing adequate
service levels, while achieving other goals such as combined sewage
overflow (CSO) elimination. The annual rainfall for the watershed
is expected to increase 12 per cent and the number of extreme
rainfall events is projected to increase by 20 per cent. The estimated sea-level rise is around 0.5 m by 2050, and 1.0 m by 2100.
These complex and multi-faceted challenges require solutions that
provide more resilience and adaptability, which are the impetuses
of this planning study. The location of the sewershed is presented
along with Metro Vancouver’s trunk sewers and Iona Wastewater
Treatment Plant (WWTP).
