SCG 31131(L3).pdf

Page 2

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)


[OCR of page images]
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)

 

Page 3

       We expect to receive results in the coming week and will forward to Council upon receipt.

       With regards to the 1% AEP drainage considerations for both Eumundi Noosa Road and internal site
       drainage, these were both addressed in our response to Council’s Information Request dated 6/01/2022 in
       our letter 31131(L2) dated 11/02/2022.

Item 10: Stormwater Quality
There are a number of conditions of the higher-order approval which have not been addressed.

       Response
       The access ramp into the bio-retention basin was shown but the ramp marker was omitted in error. This
       has been amended in the attached revised drawings.

       There are 2 stormwater drains into the bio-basin. The driveway drain invert is approximately 300mm above
       the finished detention basin surface which is proposed to be turf (now noted). This difference in level will
       promote flow into the basin and the stone scour protection noted will protect against scour across this area
       and into the bi-retention filter area.

       The second drainage point into the basin is from the rear of the units along the northern boundary. The pit
       levels shown on the submitted OPW plan were incorrect. These have been amended in the attached
       revised drawings with the proposed pipe invert and scour protection to match that of the driveway pipe.

       Subsoil pipe runs within the bio-retention bed have been shown on the revised attached drawings.

       The bio-retention pit details shown on drawing 31131-SW1.2 specifies that only the slotted 100 diameter
       pipes are set in the 150 thick drainage layer, not the 225 diameter pipe.


We trust the above information and the attached revised drawings address Council’s request for information and
look forward to Council’s approval.

Please do not hesitate to contact the undersigned should further information of clarification be required.


Yours faithfully




SEAN RICHARDSON – RPEQ 5835
For and on behalf of
SCG CONSULTING ENGINEERS


Enc    SCG Drawing Nos.: 31131-OPW-2022.05.17 RFI set




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


[OCR of page images]
We expect to receive results in the coming week and will forward to Council upon receipt.

With regards to the 1% AEP drainage considerations for both Eumundi Noosa Road and internal site
drainage, these were both addressed in our response to Council’s Information Request dated 6/01/2022 in
our letter 31131(L2) dated 11/02/2022.

Item 10: Stormwater Quality
There are a number of conditions of the higher-order approval which have not been addressed.

Response
The access ramp into the bio-retention basin was shown but the ramp marker was omitted in error. This

has been amended in the attached revised drawings.
There are 2 stormwater drains into the bio-basin. The driveway drain invert is approximately 300mm above
the finished detention basin surface which is proposed to be turf (now noted). This difference in level will
promote flow into the basin and the stone scour protection noted will protect against scour across this area
and into the bi-retention filter area.
The second drainage point into the basin is from the rear of the units along the northern boundary. The pit
levels shown on the submitted OPW plan were incorrect. These have been amended in the attached
revised drawings with the proposed pipe invert and scour protection to match that of the driveway pipe.
Subsoil pipe runs within the bio-retention bed have been shown on the revised attached drawings.
The bio-retention pit details shown on drawing 31131-SW1.2 specifies that only the slotted 100 diameter
pipes are set in the 150 thick drainage layer, not the 225 diameter pipe.
We trust the above information and the attached revised drawings address Council’s request for information and
look forward to Council's approval.

Please do not hesitate to contact the undersigned should further information of clarification be required.

Yours faithfully

SEAN RICHARDSON - RPEQ 5835
For and on behalf of
SCG CONSULTING ENGINEERS

Enc SCG Drawing Nos.: 31131-OPW-2022.05.17 RFI set

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