Chapter A - Introduction - City of Pickering

COMMENT MESPA RESPONSE (December 2011) CITY RESPONSE (October 2012) RESPONSE
SWMF #33 has been eliminated. SWMF #38 is shown
located between the 100 year flood line and the
Regional floodline. It should be noted that land for
SWMF #38 is owned by Infrastructure Ontario.
REPORT CHAPTER
AND SECTION
Geotechnical Assessment Required
Similarly to the floodplain assessment, ponds should be located on lands
which will be stable in the long-term. As such, the ponds should be
located outside the line delineated for the stable top of slope plus an
appropriate buffer. Based upon the current submission, 32 of the 69
proposed pond locations will require this assessment.
Furthermore, consideration of the loading that a full pond will place upon
the slope must be considered in this assessment. This assessment will
need to be completed prior to finalizing the pond locations.
SWMF locations were established based on the Erosion
Hazard Limit which is the greater of the Stable Top of
Slope (including toe erosion allowance where
applicable) plus an Erosion Access Allowance of 6m as
recommended by the MNR (2001) guidelines, or Top-of-
Bank plus a 10m setback as recommended by TRCA. If
the channel is unconfined this is not applicable. The
MESPA, Section B6.4, notes that additional analyses
are required at the NFSSR stage to finalize all pond
locations. This includes geotechnical assessments,
stable slope analyses, staking of top of bank, etc.
Noted, however where the pond matrices
(Appendix B6 B within the MESPA) notes a
geotechnical investigation is required at the
draft plan stage, an alternative pond location
should be considered at the MESPA stage.
The intent of the recommendation for a
geotechnical investigation was to further
refine the stable top of slope when
confirming pond locations at the NFSSR
stage. It is not expected that detailed stable
slope analyses will totally negate pond
locations identified at the MESPA stage.
Rather, they may refine the pond limits
within or adjacent to the NHS. For this
reason, alternative locations for ponds have
not been considered as part of the MESPA.
Chapter B6.4
It is also noted that should a pond relocation
be necessary, locations to be considered
need not necessarily be limited to those
considered in the MESPA; however, the
guidance in the MESPA provides the criteria
for locating and designing the SWMF
ponds.
Special Considerations for the Outlet
The City requires that the design and configuration of the outfall channels
are such that long-term operations and maintenance requirements are
minimized. This is particularly important given that the majority of the
ponds are located within the NHS and that disturbance of the NHS for
maintenance operations should be minimized to the greatest degree
possible.
Given that, when selecting the location of the pond block the proponent
should consider the requirements for safely conveying drainage from the
pond to the receiving stream in such a manner that the outfall channel will
be stable in the long-term with minimal maintenance requirements. Given
that, very steep outfall channels and emergency spillways may not be
practical in the long term and drop structures may need to be provided to
safely convey stormwater from the pond to the receiving stream.
Acknowledged. General outfall locations have been
provided. The exact outfall location and design will be
determined through the NFSSRs and detailed design.
This requirement is noted in Section B6.4 and in the
Table of Contents for the NFSSRs (Appendix J2).
Operations and maintenance access will be
required for all SWM facility features (headwalls,
plunge pools, polishing units, etc.), and shall be
designed with regards to the requirements
outlined in the City’s SWM design guidelines.
It is the City’s expectation that the NFSSR’s will
provide some insight, and detail as to the
location and design of operations and
maintenance access.
This requirement has been added to the
Annotated Table of Contents for the
NFSSRs presented in Appendix J2.
Chapter B6.4
Appendix J2
Furthermore, additional consideration will need to be given to ponds
which outlet to receiving systems which will be particularly sensitive to the
changes caused by urbanization. Additionally, where the outlet is to
infrastructure owned by others, such as the Region of Durham or
MTO/407, the proponent should have a suitable alternative outlet as a
contingency measure. These considerations should be accounted for in
the stormwater cost analysis. Lastly, ponds which outlet directly to
marshes and wetlands will need specially designed outlets to ensure
flows are disturbed appropriately. With this in mind, 59 of the 69 ponds
will require some special considerations for their outlet.
The Annotated Table of Contents prepared for the
NFSSRs and presented in Chapter J, Appendix J2 of
the MESPA outlines the requirements for a stormwater
cost analysis. No further specific costing information is
presented in the MESPA.
The Sernas Group Inc., Stonybrook Consulting Inc. December 2011, Revised February 2013 Master Environmental Servicing Plan - Amendment
SPL Beatty, Bird and Hale Limited, Earthfx Inc. 07161 Seaton Community, City of Pickering
AMEC Earth & Environmental, R.J. Burnside Appendix A7 – Page 12
Amos Environment + Planning