SCG 31131(L3).pdf

Item 4: Retaining Wall Encroachment
From the submitted plans it is unclear whether the proposed retaining walls (including footings and back
drainage) encroach into neighbouring properties.

       Response
       We have provided the section views through the boundary (retaining) walls on the attached revised
       drawings. These were not included on the previously submitted plans in error. The details show the walls
       are wholly contained within the subject site.

Item 5: Signage Information
The submitted plans do not include signage information, namely with regards to directing visitors to
the visitor carpark.

       Response
       We included the requirement for a sign at the front of the site indicating parking at the rear of the site. This
       is shown on the revised plans attached.

Item 6: Erosion and Sediment Control
The higher-order conditions of approval require submission of an erosion and sediment control plan
(ESCP) which achieves best practice and demonstrates how the downstream residential properties
will be protected from increases in peak flows and contaminated (with sediment) site runoff through
all stages of construction.
Given the topography of the site and location of downstream residences, this site is considered high-
risk of impacting off-site properties and particular focus needs to be placed on fully complying with
this condition.

       Response
       The existing site drains towards the rear boundary where an existing inter-allotment drainage pit remains.
       Along the common rear boundary with properties in Admiral Place, bunding and table drains were already
       in existence along the fence line. Regardless these facilities have been improved to strengthen the
       diversion of stormwater surface flows towards the existing stormwater pit. We have shown these facilities
       and included additional information for the various construction stages on our revised Silt and Sediment
       Control Plan. An additional sheet 31131-OW2.2 is also now included and contains the control measure
       details.

       The completed silt basin will have approximately 200m3 of storage during the bulk earthworks stage. The
       expected outflow capacity of the basin will be in the order of 55Lt/s (225 connector pipe capacity). The
       stormwater management plan/report calculated an existing Q100 flow rate for the site in the order of 280Lt/s.
       When considering a 5-10 minute storm and the outflow capacity, approximately 60-130 m3 of storage could
       be required. This would be met with the proposed basin sizing.

       We have included a Construction Phase Management Schedule/Table on the revised plans. This provides
       guidance on silt/sediment runoff management through the various construction phases.

       Construction of the silt basin will proceed prior to the bulk earthworks commencing where greater silt runoff
       loads would be expected. We don’t believe storage volumes will be required during the basin wall
       construction and that silt fencing and turfed buffer areas will be adequate protection measures during these
       works.

       We have included further specification on the proposed geofabric (Bidim) to be used in the silt basin and
       have provided expected inflow capacity calculations of the basin.

Item 7-9: Stormwater Drainage
There are a number of conditions of the higher-order approval which have not been addressed.

       Response
       A CCTV has been programmed to be undertaken but recent rain events have delayed this from occurring.
       As part of our analysis of the existing network at MCU stage we obtained a survey of the existing pipes and
       pits draining the site. This included Council Infrastructure within Headland Drive. The information was
       shown on our previously issued drawing No. 31131-SW1.3.



SCG Consulting Engineers                              Page 2 of 3                                    SCG Ref: 31131(L3)


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Item 4: Retaining Wall Encroachment
From the submitted plans it is unclear whether the proposed retaining walls (including footings and back

drainage) encroach into neighbouring properties.

Response

We have provided the section views through the boundary (retaining) walls on the attached revised
drawings. These were not included on the previously submitted plans in error. The details show the walls
are wholly contained within the subject site.

Item 5: Signage Information
The submitted plans do not include signage information, namely with regards to directing visitors to

the visitor carpark.

Response
We included the requirement for a sign at the front of the site indicating parking at the rear of the site. This

is shown on the revised plans attached.

Item 6: Erosion and Sediment Control

The higher-order conditions of approval require submission of an erosion and sediment control plan
(ESCP) which achieves best practice and demonstrates how the downstream residential properties
will be protected from increases in peak flows and contaminated (with sediment) site runoff through
all stages of construction.

Given the topography of the site and location of downstream residences, this site is considered high-
risk of impacting off-site properties and particular focus needs to be placed on fully complying with
this condition.

 

Response
The existing site drains towards the rear boundary where an existing inter-allotment drainage pit remains.

Along the common rear boundary with properties in Admiral Place, bunding and table drains were already
in existence along the fence line. Regardless these facilities have been improved to strengthen the
diversion of stormwater surface flows towards the existing stormwater pit. We have shown these facilities
and included additional information for the various construction stages on our revised Silt and Sediment
Control Plan. An additional sheet 31131-OW2.2 is also now included and contains the control measure
details.

The completed silt basin will have approximately 200m° of storage during the bulk earthworks stage. The
expected outflow capacity of the basin will be in the order of 55Lt/s (225@ connector pipe capacity). The
stormwater management plan/report calculated an existing Qioo flow rate for the site in the order of 280Lt/s.
When considering a 5-10 minute storm and the outflow capacity, approximately 60-130 m° of storage could
be required. This would be met with the proposed basin sizing.

We have included a Construction Phase Management Schedule/Table on the revised plans. This provides
guidance on silt/sediment runoff management through the various construction phases.

Construction of the silt basin will proceed prior to the bulk earthworks commencing where greater silt runoff
loads would be expected. We don’t believe storage volumes will be required during the basin wall
construction and that silt fencing and turfed buffer areas will be adequate protection measures during these
works.

We have included further specification on the proposed geofabric (Bidim) to be used in the silt basin and
have provided expected inflow capacity calculations of the basin.

Item 7-9: Stormwater Drainage
There are a number of conditions of the higher-order approval which have not been addressed.

Response
A CCTV has been programmed to be undertaken but recent rain events have delayed this from occurring.

As part of our analysis of the existing network at MCU stage we obtained a survey of the existing pipes and
pits draining the site. This included Council Infrastructure within Headland Drive. The information was
shown on our previously issued drawing No. 31131-SW1.3.

SCG Consulting Engineers Page 2 of 3 SCG Ref: 31131(L3)