Chapter A - Introduction - City of Pickering

Comments in white are satisfied.
Comments in orange background are not satisfied or are new comments.
Comments in blue background can be addressed at the NFSSR stage.
Comments in yellow are deferred due to need for hydrology model.
APPENDIX A. TRCA COMMENTS ON SEATON MESPA DECEMBER 2011; MESPA TEAM RESPONSE FEBRUARY 2013
# Section #
Page # in
PDF TRCA Comment Action Required
sand extends to about 3 m below grade, is wet to
saturated at 1.5 to 3 m, and wet silt below that.
Consulting Team’s Response
April 27, 2011
Action Taken
MESPA December 2011
TRCA Comment on MESPA
Team Response
February 2013
Conceptual alignment (Regional and Local
sanitary lines) will cross Ganatsekiagon Creek.
Depending upon the sewer depth, there is a
concern about construction and long term impacts
on groundwater contribution to the watercourse.
There are similar concerns relative to the second
sanitary sewer alignment further to the west that
skirts the Lake Iroquois shoreline deposits and
crosses the Ganatsekiagon Creek. There may be
construction and long term impacts to
watercourse baseflow.
12. 1.0 70 There is no discussion of woodland and
watercourse water balance, This is required in the
Terms of Reference and is a major gap.
13. 1.0 70 The second bullet speaks to wetland water
balance. The wetland water balance only refers
to water volumes and does not include frequency,
timing and duration.
14. 4.1 96 It appears that the water balance assessment was
considered on watershed scale. Please note that
the assessment is somewhat misleading by
showing a much lower impact on infiltration and
runoff due to the relationship between the size of
the watershed catchment and the development
parcel within that catchment. The water balance
As discussed at the meetings, please set up the
framework for woodlands and watercourses similar
to what was done for wetlands.
Please confirm that frequency, timing and duration
for all water balances have been considered.
These considerations will be important for
watercourses and woodlands as well.
Please update the water balance assessment by
further breaking down the catchments based on the
development limits. Please determine the water
balance criteria for each neighborhood. A detailed
mitigation strategy to satisfy the criteria can be
developed at the NFSSR stage.
Acknowledged.
Under review.
The groundwater balance assessment is for the
entire area as agreed to by the TRCA to provide
a comprehensive analysis of the Seaton area.
The feature based water balance assessments
are site-specific.
Woodland and headwater drainage features now
are referenced in the bullet in Section B1.0. The
approach to screening and assessment was
discussed at technical meetings. Woodland and
headwater drainage feature screening and water
balance assessments were undertaken and are
reported in new sections of the MESPA (Sections
B9 and B10).
The bullet in Section B1.0 remains the same;
however further discussion is provided in the
MESPA in Section B7.4).
An updated water balance is provided in Section
B4.5. The update includes the use of recent
changes in the PRMS model that enables a more
comprehensive evaluation of the cumulative effects
of development within the whole of the Seaton area
on local groundwater resources.
These assessments have now been provided.
See detailed comments below.
No discussion provided for consideration of
frequency, timing and duration. Please revise or
provide a rationale for the omission.
Noted.
The water balance modelling was
completed utilizing a continuous simulation
model. The model established runoff
volumes pre and post-development based
on 6 years of continuous rainfall data. The
data included representative wet, dry and
average years. The proposed amount of
water augmentation to these features is
based on trying to maintain the predevelopment
average monthly volume to
the feature. As the model utilizes actual
rainfall data, the water balance is in
essence taking the existing frequency,
timing and duration of runoff to the features
into consideration. The ultimate engineered
solution, which in most cases will involve a
third pipe conveying clean roof water
discharging to the feature, will not replicate
existing conditions with respect to timing
and duration, although will for volume.
However, the design of the conveyance
system and recommended outfall LID
measures which will be designed to retain
5mm (such as a wetland flow spreader or
bioswale) will ultimately take into
consideration flow velocities and will be
designed to dissipate flows with the
intention of trying to more closely replicate
existing timing and duration of flows.
PAGE 3 February 2013