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
note that LID does not necessary just imply
infiltration practices, measures dealing with
evapotranspiration, rainwater reuse and filtration
should also be considered and are an important
component of a sustainability strategy for the site.
21. 4.7.4 123 The Full Build-out with LID measures used a
selection of varying percentage of roof coverage
and percentage of each roof discharge to pervious
lawn areas for five land use categories. A
rationale that describes how these percentages
were derived was not provided.
22. 4.7.5 124 In Table B4.10, the comparisons are postdevelopment
without mitigation to postdevelopment
with mitigation instead of pre- to post
development.
23. 5.2.3 128 As outlined in the approved Terms of Reference,
and reiterated in Section 5.2 of the MESP, a
watershed hydrology update was required as part
of the MESP to re-assess existing conditions
using updated information, and future conditions
based on revised Official Plans, the Seaton
Neighborhood Plans, and the proposed airport.
This requirement has not been completed. The
intent of the watershed update was to build upon
an extensive amount of information provided in
the 2002 Duffins Creek Hydrology update. The
current hydrology assessment provided in the
MESP constitutes an entirely new model,
developed for the development area only, and
does not account for amendments to municipal
and regional Official Plans or the airport lands.
Provide the appropriate rationale for how the
percentage values were derived.
Consulting Team’s Response
April 27, 2011
Acknowledged. The topic was discussed at a
technical meeting.
Action Taken
MESPA December 2011
Section B4.7.4 provides updated assumptions for
the LID analyses. As noted in Section B4.7.4,
these were developed by the MESPA Team based
on experience in Duffin Heights.
Provide a pre to post-development comparison. Acknowledged. Numerous tables in Section B4.7 in the MESPA
were revised to provide the comparison of postdevelopment
model results to existing conditions
model results.
Complete a watershed hydrology update as per the
Terms of Reference, followed by a reassessment of
the quantity, erosion, and Regional control
requirements. See Appendix B, Peer Review
Comments related to the surface hydrologic
analysis, specifically comments 2 and 7-12, for
further detailed comments.
Hydrology update is being undertaken as per
discussions at technical meetings with TRCA
and the City.
As discussed in Section B5.2, numerous meetings
have been held with agencies and based on these
discussions, revisions have been made to both the
existing and future conditions models. At the time of
submission of this MESPA, Regional Storm
modelling discussions are ongoing and are
expected to extend into early 2012 as further
dialogue on modelling approaches and results is
warranted.
TRCA Comment on MESPA
increased topsoil as an LID.
Our research has shown that construction
activities also cause significant compaction
which limits the ability of the topsoil to hold water
from the first day of operation. There should be
some consideration for this in the modelling.
Until more details are provided, it is not known if
all of the ponds can remain unlined, especially
given the high groundwater table that exists
throughout the area.
The solutions for the water balance mitigation
portion of the project should be clearly defined
for each Neighbourhood Plan as part of the
MESPA. If, at the NFSSR stage, more
information is provided that will result in
deviation from the original plan, then TRCA
expects that the model will be re-run to assess
how any proposed changes will be reflected in
the overall model. To clarify, we would like to
know what other LID measures can be provided
at the NFSSR stage in case the topsoil and
unlined ponds cannot be implemented.
Comment addressed.
Comment addressed.
The hydrology study; a major component of the
MESPA, is currently being undertaken by the
City of Pickering and TRCA. There are several
components of the MESPA that rely on the
results of the hydrology study (most of which are
related to the water resources engineering
component of the project). As such, all
comments provided are based on the parts of
the submission that are not impacted by the
results of the hydrology model. A full set of
comments will follow once the revised hydrologic
analysis is incorporated into the MESPA.
Team Response
February 2013
the roof was draining to the rear yard. If
necessary, the same function of
discharging roof leaders to grade can be
achieved by connecting the roof leaders to
a third pipe system and conveying them to
infiltration facilities.
Based on the preliminary geotechnical and
hydrogeological work completed as part of
the NFSSRs, it is estimated that
approximately 80% of the ponds will not
require a liner. Also, for the remaining
locations, there are engineering solutions
that may be considered to eliminate the
need for a liner. For example, if a liner is
required because the soils are permeable
and will not allow for maintenance of a
permanent pool, there is the opportunity to
design the facility as an “infiltration SWMF”.
There are also engineering solutions for
SWMFs that are being constructed in areas
of high water table elevations such as
perimeter drains.
The LID measures modelled have been
outlined in Section B2.3 and shown on
Figure B2.1. It is also outlined in Section
B2.3.3 that implementation of the modelled
LIDs is recommended where possible;
however, other equivalent LID techniques
can also be implemented.
No response required – 2012 Duffins
Creek Hydrology Update supersedes 2011
MESPA.
PAGE 5 February 2013