McArthur River Mine
Overburden Management Project
AD
Appendix AD
NOEF Surface Water Management
Sediment Dams and Stilling Basins
Draft Environmental Impact Statement
NOEF Surface Water
Management
Sediment Dams and
Stilling Basins
30 November 2016
NOEF Surface Water Management
Sediment Dams and Stilling Basins
750-41-01
November 2016
Prepared for:
Glencore - McArthur River Mining Pty Ltd
34A Bishop Street
WINNELLIE NT 0820
Prepared by:
O'Kane Consultants Pty Ltd
193D Given Terrace
Paddington QLD 4064
Australia
Telephone: (07) 3367 8063
Facsimile: (07) 3367 8052
Web: www.okc-sk.com
Rev. #
Rev. Date
Author
Reviewer
PM Sign-off
A
1 November 2016
IT
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D
22 November 2016
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0
30 November 2016
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DISCLAIMER
This document has been provided by O'Kane Consultants Pty Ltd (OKC) subject to the following
limitations:
1. This document has been prepared for the client and for the particular purpose outlined in the
OKC proposal and no responsibility is accepted for the use of this document, in whole or in
part, in any other contexts or for any other purposes.
2. The scope and the period of operation of the OKC services are described in the OKC
proposal and are subject to certain restrictions and limitations set out in the OKC proposal.
3. OKC did not perform a complete assessment of all possible conditions or circumstances that
may exist at the site referred to in the OKC proposal. If a service is not expressly indicated,
the client should not assume it has been provided. If a matter is not addressed, the client
should not assume that any determination has been made by OKC in regards to that matter.
4. Variations in conditions may occur between investigatory locations, and there may be special
conditions pertaining to the site which have not been revealed by the investigation, or
information provided by the client or a third party and which have not therefore been taken
into account in this document..
5. The passage of time will affect the information and assessment provided in this document.
The opinions expressed in this document are based on information that existed at the time of
the production of this document.
6. The investigations undertaken and services provided by OKC allowed OKC to form no more
than an opinion of the actual conditions of the site at the time the site referred to in the OKC
proposal was visited and the proposal developed and those investigations and services
cannot be used to assess the effect of any subsequent changes in the conditions at the site,
or its surroundings, or any subsequent changes in the relevant laws or regulations.
7. The assessments made in this document are based on the conditions indicated from
published sources and the investigation and information provided. No warranty is included,
either express or implied that the actual conditions will conform exactly to the assessments
contained in this document.
8. Where data supplied by the client or third parties, including previous site investigation data,
has been used, it has been assumed that the information is correct. No responsibility is
accepted by OKC for the completeness or accuracy of the data supplied by the client or third
parties.
9. This document is provided solely for use by the client and must be considered to be
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this document or the information or assessments contained in this document. Any use which
a third party makes of this document or the information or assessments contained therein, or
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11. No section or element of this document may be removed from this document, extracted,
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permission of OKC.
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NOEF Surface Water Management, Sediment Dams and Stilling Basins
TABLE OF CONTENTS
1
INTRODUCTION.................................................................................................... 1
1.1
1.2
1.3
1.4
1.5
2
Report Objectives .................................................................................................... 1
Contaminated Water Management .......................................................................... 1
Scope of Assessment .............................................................................................. 2
Report Organisation ................................................................................................. 3
Drawings .................................................................................................................. 3
STILLING BASINS DESIGN .................................................................................. 5
2.1
2.2
2.2.1
2.3
2.3.1
2.3.2
2.3.3
overflow
2.3.4
2.3.5
2.3.6
2.4
2.4.1
2.4.2
2.4.3
2.4.4
3
Background .............................................................................................................. 5
Approach and Basis of Design ................................................................................ 5
Summary of 100 Year Ramp Channel Design Flow Inputs ..................................... 7
Design of Stilling Basin 1 - Storage and Culvert ...................................................... 7
Objectives ................................................................................................................ 7
Model Results and Findings .................................................................................... 8
Assessment of culvert size to convey 1 in 100 year ARI storm event without
10
Assessment of Culverts from MIA area ................................................................. 11
Proposed Design Features .................................................................................... 12
Discussion and clarifications .................................................................................. 13
Design of Stilling Basin 3 – Flow-through Configuration ....................................... 13
Objectives .............................................................................................................. 13
DRAINS Assessment ............................................................................................. 13
HEC RAS Assessment .......................................................................................... 15
Proposed Design Features .................................................................................... 16
SEDIMENT DAMS ............................................................................................... 18
3.1
3.2
3.3
Concept Design ..................................................................................................... 18
Design Features..................................................................................................... 19
Flood Level Considerations ................................................................................... 20
4
SCHEDULE OF QUANTITIES ............................................................................. 21
5
REFERENCES..................................................................................................... 23
Appendix A
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LIST OF TABLES
Table 1.1: Drawing List ..................................................................................................................... 4
Table 2.1: Summary of DRAINS flows (August, 2016) ..................................................................... 6
Table 2.2: Parameters used in DRAINS model of stilling basin 1 .................................................... 9
Table 2.3: Froude numbers for selected storms ............................................................................. 14
Table 3.1: Catchments and volumes of the sediment dams .......................................................... 19
Table 3.2: Applicable flood levels (m AHD) for sediment dam siting ............................................. 20
Table 4.1: Schedule of quantities ................................................................................................... 21
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LIST OF FIGURES
Figure 1.1
General NOEF surface water management infrastructure layout ................................ 2
Figure 2.1
NOEF catchment and embankment ramp layout ......................................................... 7
Figure 2.2
Stilling Basin Stage Elevation Curve ............................................................................ 8
Figure 2.3
DRAINS output for stilling basin 1 culvert. ................................................................. 10
Figure 2.4
Stilling Basin 1 – Triple 1.5m culverts - Inflow outflow hydrographs – 1 in 100 year
ARI ............................................................................................................................. 11
Figure 2.5
MIA Basin – Single 1.5m box culvert - Inflow outflow hydrographs – 1 in 50 year ARI
................................................................................................................................... 11
Figure 2.6
MIA Area – Dual 1.5m box Culverts ........................................................................... 12
Figure 2.7
Embankment drain 3 and stilling basin 3 HEC-RAS results (100 year ARI peak flow)
................................................................................................................................... 15
Figure 2.8
Embankment drain 3 and stilling basin 3 HEC-RAS results (100 year ARI peak flow)
................................................................................................................................... 15
Figure 2.9
Overflow at Chainage 1220-1360m during 1 in 100 year peak flows ........................ 16
Figure 2.10 Example of overflow at ramp 3 switchback (Chainage 240) ...................................... 16
Figure 3.1
Conceptual sediment dam layout ............................................................................... 18
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1
INTRODUCTION
This Northern Overburden Emplacement Facility (NOEF) surface water management sediment
dams and stilling basins design report has been prepared in support of the Environmental Impact
Statement (EIS) currently being prepared by McArthur River Mine (MRM).
This assessment
provides supplementary detail to infrastructure proposed for site water management, particularly
the surface runoff generated from the NOEF. This document supports a preliminary level of
engineering design, issued for MRM review and for further design refinement. This document
should be read in conjunction with the adopted design drawings, provided as Appendix A.
1.1
Report Objectives
The objectives of this document are to:

Support preliminary engineering design drawings;

Determine the required size and general configuration of certain key infrastructure,
including two stilling basins and two sediment dams;

Outline the assessment methodology and conceptual designs, so that the preliminary
designs may be used as a proxy for additional design and refinement of similar structures
that may be utilised for NOEF water management.
1.2
Contaminated Water Management
The NOEF landform is to be constructed in stages, with completion scheduled for 2032. During
construction, exposed areas of reactive waste rock will generate contaminated surface runoff,
which is to be directed to existing water management dams, referred to as PRODs.
1
Following construction of the final NOEF enhanced store-and-release cover system , runoff will be
isolated from reactive waste, though is anticipated to contain elevated suspended sediments for
some time following placement of the cover system. Surface water generated at this time is to be
directed to sediment dams to remove sediments by gravity separation.
To achieve this, a network of in-line ‘stilling basins’ and ‘sediment dams’ are proposed to manage
surface runoff generated from the NOEF. The proposed stilling basins will be utilised to dissipate
energy from potentially high velocity flows generated as NOEF surface runoff is directed down
relatively steep embankment ramps. The stilling basins act to dissipate kinetic energy, reduce
flow velocities, produce laminar flow to minimise scour risks, control flows and enhance
suspended solids removal in sediment dams.
Stilling basins will be utilised both during
construction of the NOEF and following placement of the enhanced-store-and-release cover
system, at which stage surface runoff is to be directed from stilling basins to sediment dams.
1
OKC 2016. McArthur River Mine – NOEF Cover System and Landform Design in Support of the EIS
Submission. Prepared by O’Kane Consultants Pty Ltd., October 2016.
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1.3
Scope of Assessment
Two stilling basins are assessed as part of this scope, one at the base of embankment channel 1
(Figure 1.1), and also at the base of embankment channel 3. These are referred to as stilling
basin 1 and stilling basin 3, respectively. Similarly, two sediment dams are considered. The
sizing and general arrangement of these have been provided by WRM, and OKC has integrated
the design concepts with the existing landform and existing terrain models. Note that additional
stilling basins and sedimentation dams will be required around the perimeter of the NOEF, and
while no specific designs have been developed for these, it is expected that a similar design
philosophy will be utilised for these other facilities.
Figure 1.1
General NOEF surface water management infrastructure layout
2
Surface water modelling was conducted for all NOEF open channel drains as part of the EIS , and
the assessment herein draws on peak flow and velocity estimations from that investigation. The
surface water modelling was conducted using the DRAINS model and the 100 year peak flow
rates determined from that assessment.
2
OKC 2016. McArthur River Mine – NOEF Cover System and Landform Design in Support of the EIS
Submission. Prepared by O’Kane Consultants Pty Ltd., October 2016.
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The DRAINS model set up for the NOEF drainage assessment was consequently expanded to
include additional system components, specifically drainage to and from the stilling basins (at the
landform toe), and a detention storage component for stilling basin 1.
DRAINS utilises site
specific hydrology, which has been obtained from the Australian Bureau of Meteorology, and the
model utilises established methods for event based runoff prediction. Importantly, the DRAINS
model reflects the final materials properties expected to be placed on surface to reflect
permeability characteristics of the NOEF cover system and catchment routing, and lag times
associated with the plateau and embankment catchments.
The assessment utilises the 1 in 100 year event based critical design event, as per embankment
drainage designs conducted for the EIS. Note that flow rates expected during construction of the
NOEF are lower than after the construction of the cover, because permeability (and therefore
infiltration) of the exposed cover is higher than for the established cover system.
As a
consequence, expected flow rates during cover construction have not been assessed. The higher
(final) flow rates are used for stilling basin and sediment dam design - this provides conservatism
in the assessment for construction periods. This conservatism, coupled with the high magnitude
(low probability) recurrence interval design storm provides a robust, high capacity surface water
management system.
In addition to DRAINS modelling, the hydraulic model HEC-RAS has been utilised to determine
flow profiles and hydraulic grade lines based on recently updated and more detailed NOEF
landform geometry, provided to OKC in October 2016. The modelling uses 3D NOEF landform
models to generate the exact geometry of the drainage network.
1.4
Report Organisation
This report has been subdivided into the following sections:
1.5

Section 1
Introduction

Section 2
Stilling basin design

Section 3
Sediment dam design

Section 4
References

Appendix A
Design Drawings
Drawings
Preliminary engineering design drawings are provided as Appendix A.
Surfaces have been
designed in 3D terrain model using Autodesk Civil 3D to ensure that existing and design surfaces
are integrated. Drawings provided are listed in Table 1.1
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Table 1.1: Drawing List
Drawing Number
Drawing Description
750-41-001
Sediment Dam 1 and Stilling Basin Layout Plan
750-41-002
Sediment Dam 3 Layout Plan Contaminated Water Management Stage
750-41-003
Sediment Dam 3 Layout Plan Clean Water Management Stage
750-41-004
Details
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2
2.1
STILLING BASINS DESIGN
Background
‘Stilling basins’ are used to dissipate energy from energised, surface water runoff to generate less
turbulent / erosive conditions at the outlet of the stilling basin. They are typically flow through
systems aimed at dissipating energy, rather than impoundments that store water (as proposed
herein for stilling basin 1). Stilling basins are generally constructed where surface water flows
transition from a ‘supercritical’ state to a ‘subcritical state’, and often used to intentionally generate
a ‘hydraulic jump’ to further dissipate energy.
Supercritical flows are associated with relatively high velocities and energy, with potentially very
high erosive potential as they are fast flowing and dominated by inertial forces (Vennard et al,
1996). Conversely, subcritical flows are dominated by gravitational forces, and are slower moving
due to shallower bed gradients, tail water flow control, and generally exhibit laminar flow
conditions.
Stilling basins come in a variety of types and are often used for dam spillways, and may be
constructed (for example) as inclined or stepped concrete structures at the inlet end, a basin area
and an outlet, or combination of outlets.
In open channels for mine sites, heavy rip-rap is
generally the most cost effective and practical solution to energy dissipation given the access to
large volumes of rock and availability of earthmoving equipment.
2.2
Approach and Basis of Design
Stilling basin areas have been conceptually designed based on:
1) NOEF layouts provided by MRM, the stilling basins have been sited at the base of the
channels where the longitudinal gradient transition to a shallower gradient. The changing
gradient gives rise to varied flow conditions characterised by changing flow depths and
velocities. At stilling basin 1, a storage has been proposed to retain and control surface water
inflows.
A storage is proposed to arrest flows so that they may be initially directed into
SPROD and because the adjacent haul road presents a physical barrier to the flow, culverts
are instead proposed to transmit water under the road. At stilling basin 2, a traditional flow
through system is proposed, without a defined storage, or culverts.
2) Previous DRAINS modelling conducted in August 2016 assessed catchment runoff rates in
1 in 100 year flow events, and the modelling was used to determine the size the NOEF
embankment channels. The 1 in 100 year critical duration peak flows were assessed and
those flows are utilised herein. The 100 year flows have therefore been used for design of
the stilling basins, however this should be reviewed by MRM as once surface water is
conveyed away from the NOEF, a contamination risk is reduced i.e. the risk profile has
changed.
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3) Plateau and embankment runoff drainage was designed for the NOEF ramps as part of the
EIS assessments (OKC, 2016). A summary of the relevant DRAINS modelling results for the
northern and southern stilling basins is provided in Table 2.1.
Table 2.1: Summary of DRAINS flows (August, 2016)
3
Location
Peak Flow Rate (m /s)
Peak Velocity (m/s)
Max Flow Depth (m)
Embankment Drain 1
25
4.7
0.51
Embankment Drain 3
30
5.2
0.55
EIS: Appendix H NOEF Conceptual Design for Surface Water Management
4) The Froude number has been calculated based on previous DRAINS modelling. The Froude
number provides insight to the flow profile (i.e. supercritical or subcritical), and hence the risk
of erosive conditions – such as the presence/scale of hydraulic jumps. This is applicable for
stilling basin 2 only as hydraulic grade lines in stilling basin 1 are derived from the volume of
water stored in the stilling basin behind the haul road, i.e. is not a flow through system with
downstream subcritical flow conditions.
5) The DRAINS model constructed in August 2016 for the EIS was ‘expanded’ to assess
detention storage at stilling basin 1 and determine approximate culvert requirements (to pass
under the haul road to SPROD) from stilling basin 1. The objectives being to 1) generate an
efficient use of the available storage, 2) limit culvert sizes as far as practicable and 3) convey
‘lower’ magnitude storms through the culvert.
This arrangement negates the need to
construct an open channel through the haul road.
Overflows beyond the capacity of the
system may be directed to the haul roads and/or MIA area.
6) HEC-RAS modelling under ‘steady state’ flow conditions were conducted for stilling basin 2,
using a traditional flow-through system. HEC-RAS is a leading hydraulic model developed by
the Hydrologic Engineering Centre for the U.S. Army Corps of Engineers, and enables
detailed assessment of flow conditions in open channel networks. The term ‘steady-state’
signifies that the variables (velocity, acceleration and pressure) are constant for each
individual point in the channel during the analysis. These conditions were modelled using the
sustained 100 year peak flow rates output from DRAINS (i.e. the hydrological component of
the August 2016 modelling) and was conducted in this manner to simplify the assessment,
determine the practicality of the general arrangement and estimate water levels / hydraulic
grade lines.
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2.2.1
Summary of 100 Year Ramp Channel Design Flow Inputs
Figure 2.1
NOEF catchment and embankment ramp layout
The scope of this assessment relates to two proposed spilling basins and two sediment dams as
shown in Figure 1.1 and Figure 2.1. These were selected by MRM as they were considered to be
among the more complex geometries to achieve the required functionality.
2.3
Design of Stilling Basin 1 - Storage and Culvert
DRAINS modelling was conducted to include drainage paths extending from the base of ramp 1
embankment drain, to stilling basin 1. A detention storage / culvert configuration was adopted for
stilling basin 1 because a flow through configuration would require flow to be discharged across
the surface of the haul road or into the MIA area, which is not a viable alternative. As flow is
throttled by the culvert, water levels increase and subside in the storage depending on the
magnitude of the storm, its temporal pattern, and amount of runoff generated.
2.3.1
Objectives
The objectives of the modelling were specifically to:
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1) Validate whether the general arrangement of Stilling Basin 1, comprising a detention storage
area and culvert under the haul road to SPROD, is a feasible solution. The size of the culvert
and the volume of storage required in the stilling basin are intrinsically linked as larger
culverts have increased flow capacity, and therefore the required storage volume is reduced.
The assessment aims to recommend an appropriate culvert size based on the storage
volume available.
2) To determine the approximate size of the culverts required from the MIA area into Sediment
Basin 1 following decommissioning of culverts to SPROD from the stilling basin. This is
3
based on an approximate detention storage capacity of 9000 m in the MIA area.
3) Determine the capacity of the system in terms of event-based rainfall ARI’s in order to
determine under what storm event the system will overflow.
4) Determine the size of the culvert that would be required to convey the 1 in 100 year ARI event
without overflow.
2.3.2
Model Results and Findings
The DRAINS modelling indicates that a combined stilling / detention basin is generally feasible,
given the spatial constraints. This system modelled was a quasi ‘high early discharge’ system
where the culvert inlet is sited in a sump at the base of the stilling basin, and acts to increase
outflow through the culvert early in the storm. The culvert modelled, is a 1.5m x 1.5m pre-cast
3
concrete box culvert system and 3,500m of storage (Figure 2.2).
Figure 2.2
Stilling Basin Stage Elevation Curve
The system provides capacity to accommodate up to approximately the 1 in 10 year ARI critical
3
storm event, with appreciable (~2.2m /s) overflows in the 1-in-20 year ARI critical duration event.
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Overflows may be directed towards either the MIA drain or spill to the haul road depending on
MRM’s preferred management. Both options enable overflow to be contained within the
contaminated water management system.
The storage inflow-outflow curves for the 1-in-10 year critical duration event are provided below the area indicated between the inflow and outflow curves indicates the volume of water stored
behind the culvert in the analysis. The outflow hydrograph indicates that the storage/culvert
3
combination has a capacity of approximately 7 m /s.
Key inputs/outputs of this model, are listed in Table 2.2.
Table 2.2: Parameters used in DRAINS model of stilling basin 1
Parameter
Value
Peak inflow
13 m /s
Peak outflow
7 m /s
Outflow Type
1.5m x 1.5m box culvert
RL basin floor
45m RL
Culvert invert level (IL)
44m RL
Culvert downstream IL (at SPROD)
43.5m RL
Weir overflow level
46.5m RL
3
3
DRAINS output levels / hydraulic grade lines are indicated in Figure 2.3.
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Figure 2.3
DRAINS output for stilling basin 1 culvert.
Other culvert configurations may be preferred (such as the use of concrete pipes or polyethylene
pipes), though these generally offer lower flow capacity and therefore may only accommodate
lower magnitude events. Combinations of pipes may also be used to increase outflow capacity,
for example dual 1200mm diameter pipes offer a similar flow area and potentially similar
performance to a singular box culvert alignment. Larger box culverts would offer increased flow
capacity and thereby offer increased capacity / immunity from larger events.
2.3.3
Assessment of culvert size to convey 1 in 100 year ARI storm event without overflow
DRAINS modelling indicates that a system comprising three 1.5m box culverts in parallel would
be required to convey the 1 in 100 year ARI critical duration storm flows to the SPROD without
overflow. Refer to Figure 2.4 inflow and outflow hydrographs. These indicate that the detention
storage has very little influence reducing peak outflows.
3
This is based on approximately 4,860m storage calculated for the stilling basin, and general
arrangement provided in D 750-41-001. Given the large quantity of culverts required to span the
road, and high dilutions of surface runoff in large magnitude storms, this is considered an
impractical alternative.
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Figure 2.4
2.3.4
Stilling Basin 1 – Triple 1.5m culverts - Inflow outflow hydrographs – 1 in 100 year
ARI
Assessment of Culverts from MIA area
Culverts from the MIA area were initially modelled as a singular 1.5m box culvert, with 9000m
3
storage capacity and 4m max basin depth (from the invert of the sump to the overflow weir). The
active storage depth (not including sump) was 3m.
In this scenario storage capacity was
3
exceeded with a peak overflow of approximately 0.3m /s. The single culvert system did not
overflow in the 1 in 50 year ARI critical duration storm. Inflow and outflow hydrographs for this
model are provided for the 1 in 50 year ARI critical duration event in Figure 2.5 below.
Figure 2.5
MIA Basin – Single 1.5m box culvert - Inflow outflow hydrographs – 1 in 50 year ARI
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Dual 1.5m culverts were also modelled from the MIA area, indicating no overflow in the 1 in 100
year ARI critical duration event.
Inflow and outflow hydrographs are shown in Figure 2.6.
Presumably a larger sized, single box culvert may be appropriate to convey the 1 in 100 year ARI
critical event surface runoff if this is required.
Figure 2.6
2.3.5
MIA Area – Dual 1.5m box Culverts
Proposed Design Features
Based on the above approach and assessment of stilling basin 1, various features are required
for the design, a summary of which is provided below:

3
A storage area of approximately 3250 m , or more where possible. The storage should be
low permeability to retain water and lined with rip-rap scour protection placed on walls. Large
energy dissipation structures (boulders) should be placed proud of the stilling basin floor
across the direction of flow.

A single 1.5m box culvert to convey up to the 5 year ARI flows from the north side of the haul
road to the SPROD, to convey higher flows either increased storage or increased culvert
sizes are required (or both). The culvert may be sited in a sump to provide quasi high early
discharge and include concrete wing walls for improved hydraulics. Culverts will require good
foundation construction to limit differential settlement over time and bedding appropriate for
the selected culvert type/material.

A high level spillway from the spilling basin to convey higher flow rates to either the haul road,
or other desired relief point.

Outlet scour protection will be required at SPROD.
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2.3.6

Discussion and clarifications
3
The storage / culvert design is based on the use of 3250m storage, however this may
potentially be increased by expanding the storage zone to the south east, along the alignment
of the proposed stilling basin.
An increased storage volume would allow for either 1)
increased capacity of the overall system (to accommodate for example 1 in 20 year event via
the culvert) or 2) allow for a smaller culvert, with the same currently modelled capacity (i.e. 5
to 10 year storm event).

Often culverts can block over time where sediment builds up over time during low flows.
However, this is more common in flatter areas where the culvert does not have a freely
discharging outlet and is affected by tailwater conditions. The culvert to SPROD will have a
freely discharging outlet (i.e. the downstream invert is above SPROD top water level) and
therefore blockage by long term build of sediment is unlikely.

Further work to optimise the conceptual storage and culvert configuration is recommended to
provide optimal flow and cost given adopted performance requirements of the culvert.

Upon decommissioning the culvert from the stilling basin, i.e. once the NOEF cover is
constructed, it would be effective to utilise stilling basin 1 as an initial sediment dam.
Therefore the settling basin volume may reduce the volumetric requirements of sediment
dam.
At this stage, the two systems are considered independently, i.e. the volume of
sediment dam 1 is as provided by WRM.
Design of Stilling Basin 3 – Flow-through Configuration
2.4
HEC-RAS modelling was conducted to assess ramp drainage and the proposed stilling basin that
extends from the toe base of ramp 3 embankment drain to stilling basin 3.
A flow through
configuration is adopted for stilling basin 3 given the unobstructed access to WPROD, however it
is understood that local infilling of the existing terrain is required to provide adequate and
consistent gradient for gravity drainage to WPROD.
2.4.1
Objectives
The objectives of the modelling were specifically to:
1. Determine water levels at the stilling basin and address the risk of a potential hydraulic
jump causing scouring of the NOEF toe.
2. Determine the general layout of the spilling basin and specific design features.
2.4.2
DRAINS Assessment
DRAINS modelling conducted in August 2016 allows the calculation of the Froude number. The
Froude number is a dimensionless parameter, and describes the ratio of velocity to flow depth
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(and acceleration due to gravity). Flow velocities and depths from a range of storm magnitudes
were used to calculate the Froude number.
If the Froude number (F) is > 1, the flow is supercritical and if F < 1, the flow is subcritical. Where
F = 1, there is a transition and a hydraulic jump may occur, the turbulence of the jump dissipates
energy. The relationship is described by the equation below, where F is the Froude number, V is
-2
velocity (m/s), and D is depth of flow (m) and g acceleration due to gravity (9.8 ms ).
Note that the equation shows that the velocity of flow has a greater influence on the Froude
number than does the depth of flow. The velocities used in the DRAINS assessment are the peak
velocities for the storm and therefore provide some conservatism in the estimate of the Froude
number.
𝐹=
𝑉
√𝑔 × 𝐷
Table 2.3: Froude numbers for selected storms
Storm
ARI
Flow
Rate
3
(m /s)
Max Velocity (m/s)
Flow Depth (m)
Froude Number
Embankment
Toe
Embankment
Toe
Embankment
Toe
5
14
4.1
2.2
0.36
0.65
2.21
0.87
20
21
4.6
2.4
0.45
0.83
2.2
0.84
100
30
5.2
2.7
0.55
1.0
2.2
0.86
Results indicate that for all storm scenarios there is a transition between supercritical
(embankment drain) flows and subcritical flows (in the toe areas). This infers that weak jumps
may occur in these locations. The upstream Froude numbers are relatively low (~2.2), according
to Chow (1959), this represents only a weak jump, which occurs in the range 1.7 <F< 2.5. In this
range, the water surface only shows slight undulations. These surface ‘riffles’ result low energy
dissipation and in general, the downstream water surface remains relatively smooth. HEC-RAS
results indicate similar velocities and Froude numbers, and a change in flow depth of
approximately 0.6m.
The length of a hydraulic jump can be estimated to predict its location and bolster scour protection
along the length of the jump, given by the equation:
𝐿 = 220 × 𝑦1 ∗ tanh(𝐹𝑟1 − 1 )/22
Where y1 and F1 are upstream (from the jump) flow depth and Froude numbers respectively.
This is based on the 100 year values in Table 2.3 above, the overall length of the jump is short, at
approximately 7m. Given the above, the presence of turbulent hydraulic jumps are likely to be
minor and temporary, and won’t require any significant change to the channel geometry design or
construction of heavy surface structures for scour protection.
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2.4.3
HEC RAS Assessment
HEC-RAS modelling was conducted from the crest of the proposed NOEF landform through to the
stilling basin, using a 100 year peak, steady flow analysis. Perspective and longitudinal results
are illustrated in Figure 2.7 and Figure 2.8 respectively, noting that:

The blue area indicates the flow area.

Horizontal black lines indicate the stations with representative cross section.

Red lines indicate the top of embankment line
Stilling B asin 3 - IT edits
Plan: Current model
31/10/2016
265
263
261
259
257
255
Legend
WS 100 Year
Ground
Bank Sta
252
250
248
246
243
241
239
237
235
233
228
224
221
217
214
210
207
203
200
197
193
190
187
184
181
178
175
173
171
169
166
164
162
160
158
156
154
152
150
148
146
144
142
140
138
136
134
132
130
128
126
124
122
120
118
116
114
112
110
108
106
104
Figure 2.7
Embankment drain 3 and stilling basin 3 HEC-RAS results (100 year ARI peak flow)
Stilling Basin 3 - IT edits
Plan: Current model
31/10/2016
Stilling Basin 2 Stilling Basin 2
180
Legend
EG 100 Year
WS 100 Year
Crit 100 Year
Ground
160
140
Elevation (m)
120
100
80
60
40
20
0
200
400
600
800
1000
1200
1400
1600
1800
Main Channel Distance (m)
Figure 2.8
Embankment drain 3 and stilling basin 3 HEC-RAS results (100 year ARI peak flow)
Two distinct increases in water level are evident, one at approximately chainage ~1220-1360m
(measured from the end of the drain), which corresponds with the ramp 3 switchback, and the
other at the landform toe.
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Initial HEC-RAS hydraulic modelling indicates that embankments will need to be raised nominally
at the ramp 3 switchback, as indicated by Figure 2.9 and Figure 2.10. This is not considered a
significant change, and has not been re-designed at this stage. Flow continuity calculations are
valid, as the affected cross sections at this location are conceptually bounded on the right hand
side (in Figure 2.10) by a vertical wall at Station 50m.
Stilling B asin 3 - IT edits
Plan: Current model
31/10/2016
Legend
249
WS 100 Year
248
Ground
247
Bank Sta
246
245
243
242
241
240
239
238
237
236
235
234
233
232
228
227
224
223
222
221
219
Figure 2.9
Overflow at Chainage 1220-1360m during 1 in 100 year peak flows
Figure 2.10
2.4.4

Example of overflow at ramp 3 switchback (Chainage 240)
Proposed Design Features
A continuation of the embankment ramp drain 3 to WPROD is sufficient to manage the minor
increase in surface water flows and weak hydraulic jump anticipated in this area.
substantial increase in cross sectional (flow) area is required;
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
Infill is required to extend out from the northeast of the NOEF to provide the relief for the toe
drain to continue to drain by gravity to WPROD (refer to DRG 750-41-002).

Rip rap armouring of the drain is required and should be constructed in an interlocking matrix
to provide good scour protection. Rip rap boulders, placed in and proud of the surface in the
direction of flow should be constructed in rows and offset from one another dissipate energy
at the base of the embankment drain. Three rows are sufficient, and over a distance of no
less than 10m as indicated in (refer to DRG 750-41-004).

The channel under the rip rap should be underlain with a synthetic geomembrane to provide a
low permeability layer and prevent entrainment of finer material underneath the riprap from
local eddies from turbulent flows.
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3
SEDIMENT DAMS
Sediment dams are storages used to capture fine grained material from surface water. A number
of sediment dams are proposed for NOEF surface water management, with two sediment dams
(sediment dams 1 and 3) discussed herein. Stilling basins 1 and 3 are located downstream of
stilling basins 1 and 3 respectively, as shown in Figure 1.1, and are included to receive potentially
sediment-impacted water from the final cover system.
3.1
Concept Design
WRM have provided OKC conceptual sediment ponds configurations to support site surface water
management design. The proposed ‘Type F’ (IECA, 2008) sediment ponds have two zones: a
settling zone to treat the sediment laden water; and a sediment storage zone for the collection of
sediment that drops out of the water. The sediment ponds are sized based on a 5-day cycle
whereby the influent water fills the sediment pond, is treated and then discharged to the receiving
environment within a maximum of five days. As required, the water is to be ‘pumped down’ to the
sediment storage zone in preparation for the next runoff event. De-silting of the sediment pond
should be undertaken as required when the sediment storage zone is close to full.
A conceptual ‘Type F’ sediment dam layout is provided as Figure 3.1 and has been provided to
OKC by WRM from ‘the Best Practice Erosion and Sediment Control’ (IECA, 2008) guidelines.
This conceptual layout has been adopted to support the siting and geometric design of the
sediment dams.
Figure 3.1
Conceptual sediment dam layout
Sediment dam locations and general volumes have been calculated based on contributing
catchment areas, and provided by WRM, as listed in Table 3.1. Sediment dams/traps were sized
by WRM based on a ‘Type F’ sediment dams to capture the 1 year ARI 5 day rainfall event.
WRM note that the size of this type of dam is related to catchment area and the equation for
estimating the size of the settling zone of the sediment dam/trap is given by:
𝑉𝑠 = 10 × 𝑅 × 𝐶𝑣 × 𝐴
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Where vs = volume (m ), R is 85% of the 5 day rainfall depth (36mm), Cv is the volumetric runoff
coefficient and A is the catchment area (ha). WRM note that the settling volume required for each
sediment dam/trap is therefore given by:
𝑉𝑠 = 216 × 𝐴
Table 3.1: Catchments and volumes of the sediment dams
Location
Catchment Area (ha)
Settling Zone Volume
(ML)
Storage Zone Volume
(ML)
Sediment dam 1
82.1
17.7
8.9
Sediment dam 3
108.4
23.4
11.7
Source: email to OKC from WRM 17 October 2016
3.2
Design Features
Further to the above volumetric configurations, further design principles and recommendations
were provided by WRM, including:

The recommended minimum length (L) to width (W) ratio of the sediment dam is 3:1. The
length to width ratio is important because the longer flow path improves settlement efficiency.

The recommended volume of the sediment storage zone for a ‘Type F’ sediment dam/trap is
50% of the settling volume. Deposition of sediment in the basin will vary over time, it is
anticipated that the sediment storage zone will be filled in approximately 5 years, though
general maintenance may be carried out at a reasonable subset of that.

The settling zone of the sediment ponds have been sized to capture the required 63% AEP (1
year ARI) 5-day rainfall event from the contributing catchment area.

Internal baffles can be constructed where the space constraints limit the sediment dam
footprint to less than the desired ratio. Where utilised, internal baffles should be placed so
that flow velocities within the sediment dam/trap do not exceed the scour velocity for the
design storm.

The crest level of internal baffles should be at or just below the crest of the spillway.

Spillways are to be designed to convey the 1% AEP (100 year ARI) discharge plus a 300 mm
freeboard to the crest of the dam wall. This is based on sediment dams being used for more
than two consecutive wet seasons.

Adequate erosion protection will be required at and downstream of the spillway of the
sediment pond.
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3.3
Flood Level Considerations
Estimated flood levels from the McArthur River and a smaller (unnamed) local creek were
provided by WRM to support the selected location of sediment dams, i.e. to ensure sediment
dams are isolated from floodwaters to prevent back-flooding of the sediment dams.
Flood
magnitudes were provided for 1% annual exceedance probability (AEP), equivalent to
approximately the 1 in 100 year ARI flood event, and the 5% AEP, (~20 year ARI event). Note
that OKC has not reviewed or conducted any flood assessment to confirm appropriateness of
adopting these levels. The levels are listed in Table 3.2 below.
Table 3.2: Applicable flood levels (m AHD) for sediment dam siting
Local Creek
McArthur River
5% AEP
1% AEP
5% AEP
1% AEP
Sediment dam 1
34.24
35.62
35.90
39.80
Sediment dam 3
37.10
37.69
37.10
39.12
Source: provided to OKC by WRM, email 14 October 2016
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4
SCHEDULE OF QUANTITIES
A preliminary schedule quantities is listed below in Table 4.1.
Table 4.1: Schedule of quantities
Facility
Stilling Basin 1
Description
Quantity
Unit
Shape stilling basin floor and embankments
7,333
m
2
Construct 0.15m gravel bedding layer (base of BIDIM geofabric)
1,100
m
3
Place protective BIDIM (or similar) base geofabric
7,333
m
2
Construct HDPE low permeability liner
7,333
m
2
Construct upper BIDIM protective geofabric
7,333
m
2
Construct 0.15m gravel bedding layer above geofabric
1,100
m
3
Construct 0.5m interlocking rip rap surface with proud boulders for
energy dissipation.
3,667
m
3
Shape and compact overflow spillway area
200
m
2
Excavate culvert trench through haul road
2,850
m
3
Construct culvert floor / bedding
(0.5m depth assumed)
63
m
3
Construct culvert to SPROD
(1.5m wide x 3m long box culvert assumed)
20
No.
Construct inlet and outlet headwalls
2
No.
Construct riprap apron at outlet headwalls
70
m
3
Excavate Basin (including allowance for base and riprap
construction)
9,944
m
3
Shape culvert basin floor and embankments
2,246
m
2
337
m
3
2,246
m
2
337
m
3
1,123
m
3
Shape and compact overflow spillway area
90
m
2
Excavate culvert trench through haul road
9,000
m
3
Construct culvert floor / bedding
(0.5m depth assumed)
84
m
3
Construct culvert to Sediment Basin 1
(1.5m wide x 3m long box culvert assumed)
27
No.
Construct inlet and outlet headwalls
2
No.
Construct riprap apron at outlet headwalls
70*
m
Construct perimeter diversion bund and drain
135
m
Shape channel drainage from culvert outlet to Sediment Dam 1
730
m
2
Excavate (cut) sediment dam to required levels
49,379
m
3
Construct (fill) sediment dam to required levels
2,617
m
3
Grade and compact final surfaces
14,500
m
2
431
m
Construct 0.15m gravel bedding layer (base of BIDIM geofabric)
Place BIDIM (or similar) geofabric filter
Construct 0.15m gravel bedding layer above geofabric
Construct 0.5m interlocking rip rap surface with proud boulders
embedded in surface for energy dissipation.
Culvert Basin 1
Sediment Dam 1
Construct perimeter bund
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Facility
Description
Quantity
Unit
44*
m
3
Bulk fill of drainage berm
177,619
m
3
Shape final berm surface
6,886
m
2
Construct 0.15m gravel bedding layer (base of BIDIM geofabric)
1,033
m
3
Place BIDIM (or similar) protective base layer
6,886
m
2
Construct HDPE low permeability liner
6,886
m
2
Construct upper BIDIM protective geofabric
6,886
m
2
Construct 0.15m gravel bedding layer above geofabric
1,033
m
3
Construct 0.5m interlocking rip rap surface with proud surface
boulders for energy dissipation.
566
m
3
Construct rip rap outlet to WPROD
224
m
3
Reshape (cut) berm
18,640
m
3
Grade/shape surface
5,808
m
2
265
m
Bulk exaction of Sediment Dam 3
41,953
m
3
Grade and compact surfaces
15,100
m
2
Bulk fill of Sediment Dam 3 (bunds etc.)
2,945
m
3
Bulk fill of existing flowpaths
14,360
m
3
Construct/place spillway rip rap
62
m
3
Construct/place rip rap at eastern inlet
78
m
3
Construct/place rip rap at western inlet
61
m
3
1,555
m
3
Construct perimeter bund
280
m
Construct continuous precast concrete T-wall flow baffle
80
m
Construct / place 0.5m rip rap at spillway
Stilling Basin 3
(flow to WPROD)
Stilling Basin 3
(flow to Sediment
Dam 3)
Construct drain to Sediment Dam 3
Sediment Dam 3
Construct diversion bund along WC1 drain
Note: All volumes quoted refer to in situ volumes, quoted fill volumes are post compaction.
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5
REFERENCES
Chow, V. T. 1959. Open-channel hydraulics. McGraw-Hill, New York.
DRAINS User Manual. http://www.watercom.com.au/
HEC-RAS user manual
OKC, 2016 ‘Appendix H NOEF Conceptual Design for Surface Water Management’
Vennard, J.K and Street, R.L., Elementary Fluid Mechanics, Seventh Edition, Wiley New York
1995.
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Appendix A
Design Drawings
NO
EF
NOEF EMBANKMENT DRAIN
EM
BAN
70
EN
KM
65
TR
AM
TIN
G
P
EX
IS
HA
UL
NOEF EMBANKMENT
44.8m
60
RO
AD
STILLING BASIN BLOCKED PRIOR TO
COVER SYSTEM PLACEMENT TO DIRECT
CONTAMINATED WATER INTO SPROD
44.5m
1
STILLING BASIN / CHANNEL
ROCK BAFFLES TO BE PLACED AT BOTTOM OF
EMBANKMENT DRAIN TO PROVIDE SCOUR PROTECTION
REFER TYPICAL BAFFLE DETAIL.
55
ALTERNATIVE BUND LOCATION FOR
INCREASED STORAGE CAPACITY
004
44.3m
MINE-AFFECTED RUNOFF OVERFLOW FOR
WATER TO SPILL ACROSS EXISTING HAUL
ROAD INTO SPROD FOR HIGH FLOW EVENTS
50
47.7m
~60m CULVERT WITH INLET HEADWALL. SIZE TO BE
CONFIRMED ON MRM REQUIREMENTS. CULVERT TO
BE UPGRADE TO CATER FOR ADDITIONAL FLOWS.
EXISTING MINE-AFFECTED WATER TO BE
RE-ROUTED TO EXISTING MIA SUMP
44.3m
40.9m
E
OUTLET SCOUR PROTECTION
E
E
E
E
E
E
43.8m
E
E
CONSTRUCT NEW TABLE DRAIN EXISTING MIA SUMP
E
SPROD
EXISTING MIA AREA
39.4m
E
BASIN PERIMETER BUND CONSTRUCTED BETWEEN
MINE-AFFECTED AND CLEAN CATCHMENTS
42.5m
E
~ 80m CULVERT WITH HEADWALL
SIZE TO BE CONFIRMED ON MRM REQUIREMENTS
46.6m
EXISTING MIA DRAIN FILLED NORTH OF PROTECTION
BUND AND RE-SHAPED TO FORM PART OF CLEAN
WATER CULVERT BASIN
40
LEGEND
38.6m
EX
I
ST
IN
E
E
40
E
E
EX
E
ACCESS RAMP
EXISTING CONTOUR
G
MI
A
AI
IS
N
TIN
G
E
E
E
PROPOSED CONTOUR
HA
UL
50
PROPOSED CLEAN WATER DRAIN
RO
PROPOSED CONTAMINATED
WATER DRAIN
E
SEDIMENT BASIN 1
E
PROPOSED CLEAN WATER CULVERT
TOPSOIL STOCKPILE
TO BE EXCAVATED
PROPOSED CONTAMINATED WATER
CULVERT
E
40
40
40
SPILLWAY
50
EXISTING CONTAMINATED
WATER DRAIN
DR
AD
35
E
35
CULVERT BASIN (30m x 20m)
E
40
E
PROPOSED BUND
1% AEP FLOOD ELEVATION (RL35.62)
EXISTING OVERHEAD ELECTRICITY
E
EXISTING TOPSOIL
STOCKPILE
E
EXISTING UNDERGROUND
ELECTRICITY
E
33.0m
E
E
CLIENT/PROJECT:
EXISTING POWER SUPPLY
TO BE RELOCATED
E
MCARTHUR RIVER MINE
SEDIMENT DAM & STILLING BASIN DESIGN
PRODUCED BY:
SEDIMENT DAM 1 AND STILLING BASIN LAYOUT PLAN
O'Kane
Consultants Pty Ltd.
1:2000
20
10
0
20
40
60
80
Integrated Mine Waste Management and Closure Services
Specialists in Geochemistry and Unsaturated Zone Hydrology
100m
OKC PROJECT NO.: 750/41
THIS DRAWING IS TO BE READ IN CONJUNCTION WITH OKC REPORT
DESCRIPTION
750/41
REVISIONS
REFERENCE
SCALE 1:2000
DWG. NO.
NO.
A
DESCRIPTION
PRELIMINARY ENGINEERING DESIGN ISSUE FOR CLIENT REVIEW
DRN. BY:
APPD. BY:
DATE
SMW
PG
01.11.16
B
ENGINEERING DESIGN ISSUE
SMW
PG
21.11.16
0
FINAL ENGINEERING DESIGN ISSUE
SMW
PG
30.11.16
DRN. BY:
APPD. BY:
SCALE:
DATE:
S. WALKER
DATE:
P. GARNEAU
AS SHOWN
PAGE SIZE:
A3
SEDIMENT DAM 1 AND STILLING BASIN
LAYOUT PLAN
30.11.16
30.11.16
OKC RPT. NO.:
750/41
DWG. NO.:
750-41-001
REV.:
0
A
ARE
RES
TRI
CTE
D
REFER TO DRG
750-41-003
EXISTING OVERLAND FLOWPATH
AIN
WC1 DR
FUTURE CLEAN WATER DRAIN
1:3 EMBANKMENT TO BE CONFIRMED
ALTERNATE EMBANKMENT
RAMP HAULROAD ALIGNMENT
TO BE CONFIRMED
SEDIMENT BASIN 3
REFER DRG750-41-004FOR DETAILS
2%
2%
1%
45
2%
50
CONSTRUCT NOEF BERM WITH COMPACTED
MATERIAL TO ACCOMMODATE DRAINAGE ABOVE
NO
EF
MINE-AFFECTED WATER TO DISCHARGE INTO
SPROD PRIOR TO COVER SYSTEM PLACEMENT
WPROD
BA
NK
EM
BA
NK
ME
NT
R
AM
ME
N
2
INLET TO WPROD AND SCOUR PROTECTION
55
EM
TD
004
60
P
RA
IN
STILLING BASIN / CHANNEL.
ROCK BAFFLES TO BE EMBEDDED IN CHANNEL AND
OFFSET TO CREATE SNAKING DRAINAGE PATH.
REFER TYPICAL BAFFLE DETAIL.
65
LEGEND
EXISTING CONTOUR
50
PROPOSED CONTOUR
50
PROPOSED CONTAMINATED
WATER DRAIN
1% AEP FLOOD ELEVATION (RL37.69)
35
NOEF EMBANKMENT
55
50
45
40
70
65
60
75
70
CLIENT/PROJECT:
80
75
80
85
MCARTHUR RIVER MINE
SEDIMENT DAM & STILLING BASIN DESIGN
PRODUCED BY:
STILLING BASIN 3 LAYOUT PLAN
MINE-AFFECTED WATER MANAGEMENT STAGE
O'Kane
Consultants Pty Ltd.
Integrated Mine Waste Management and Closure Services
Specialists in Geochemistry and Unsaturated Zone Hydrology
1:2000
20
10
0
20
40
60
80
100m
OKC PROJECT NO.: 750/41
THIS DRAWING IS TO BE READ IN CONJUNCTION WITH OKC REPORT
DESCRIPTION
750/41
REVISIONS
REFERENCE
SCALE 1:2000
DWG. NO.
NO.
A
DESCRIPTION
PRELIMINARY ENGINEERING DESIGN ISSUE FOR CLIENT REVIEW
DRN. BY:
APPD. BY:
DATE
SMW
PG
01.11.16
B
ENGINEERING DESIGN ISSUE
SMW
PG
21.11.16
0
FINAL ENGINEERING DESIGN ISSUE
SMW
PG
30.11.16
DRN. BY:
APPD. BY:
SCALE:
DATE:
S. WALKER
DATE:
P. GARNEAU
AS SHOWN
PAGE SIZE:
A3
STILLING BASIN 3 LAYOUT PLAN
MINE-AFFECTED WATER
MANAGEMENT STAGE
30.11.16
30.11.16
OKC RPT. NO.:
750/41
DWG. NO.:
750-41-002
REV.:
0
REA
DA
RES
TRI
CTE
SMALL DITCH CUT INTO NATURAL
GROUND TO DIVERT NORTHERN
CATCHMENT WATER INTO WC1 DRAIN
SAFTY BUND TO BE CONSTRUCTED ON
NORTHERN SIDE OF SEDIMENT DAM
SED-LADEN RUNOFF DIRECTED
TO SEDIMENT DAM 3
SEDIMENT DAM ACCESS RAMP
DIVERSION BUND.
ACCESS OVER BUND
TO BE CONFIRMED.
1%
WC1 DRAIN DIVERSION BUND
ALTERNATE EMBANKMENT
RAMP HAULROAD ALIGNMENT
TO BE CONFIRMED
SPILLWAY
AIN
WC1 DR
1%
EXISTING OVERLAND FLOWPATH
1%
1%
1%
SEDIMENT BASIN 3
1%
40
1%
3.4m HIGH PRECAST CONCRETE T-WALL (OR SIMILAR)
TO PROVIDE WATER-TIGHT BARRIER TO FLOW
50
NO
EF
STILLING BASIN / CHANNEL.
ROCK BAFFLES TO BE EMBEDDED IN CHANNEL AND
OFFSET TO CREATE SNAKING DRAINAGE PATH.
REFER TYPICAL BAFFLE DETAIL.
WPROD
EM
BA
N
2
004
WESTERN SEDIMENT DAM INLET
45
EASTERN SEDIMENT DAM INLET
DRAINAGE REROUTED TO
PROPOSED SEDIMENT DAM 3
FOLLOWING COVER CONSTRUCTION
EXISTING FLOWPATH TO BE
INFILLED AND GRADED TOWARDS
PROPOSED SEDIMENT DAM 3
55
EM
BA
KM
EN
T
NK
ME
NT
R
60
AM
DR
P
AIN
35
60
45
40
65
NOEF EMBANKMENT
LEGEND
55
50
70
65
60
75
EXISTING CONTOUR
50
PROPOSED CONTOUR
50
PROPOSED CLEAN WATER DRAIN
70
80
PROPOSED BUND
75
1% AEP FLOOD ELEVATION (RL37.69)
80
85
90
CLIENT/PROJECT:
MCARTHUR RIVER MINE
SEDIMENT DAM & STILLING BASIN DESIGN
PRODUCED BY:
SEDIMENT DAM 3 AND STILLING BASIN LAYOUT PLAN
CLEAN WATER MANAGEMENT STAGE
O'Kane
Consultants Pty Ltd.
Integrated Mine Waste Management and Closure Services
Specialists in Geochemistry and Unsaturated Zone Hydrology
1:2000
20
10
0
20
40
60
80
100m
OKC PROJECT NO.: 750/41
THIS DRAWING IS TO BE READ IN CONJUNCTION WITH OKC REPORT
DESCRIPTION
750/41
REVISIONS
REFERENCE
SCALE 1:2000
DWG. NO.
NO.
A
DESCRIPTION
PRELIMINARY ENGINEERING DESIGN ISSUE FOR CLIENT REVIEW
DRN. BY:
APPD. BY:
DATE
SMW
PG
01.11.16
B
ENGINEERING DESIGN ISSUE
SMW
PG
21.11.16
0
FINAL ENGINEERING DESIGN ISSUE
SMW
PG
30.11.16
DRN. BY:
APPD. BY:
SCALE:
DATE:
S. WALKER
DATE:
P. GARNEAU
AS SHOWN
PAGE SIZE:
A3
SEDIMENT DAM 3 LAYOUT PLAN
CLEAN WATER MANAGEMENT STAGE
30.11.16
30.11.16
OKC RPT. NO.:
750/41
DWG. NO.:
750-41-003
REV.:
0
3.4m HIGH PRECAST CONCRETE T-WALL (OR SIMILAR)
TO PROVIDE WATER-TIGHT BARRIER TO FLOW
DITCH CUT INTO NATURAL GROUND TO DIVERT
NORTHERN CATCHMENT WATER INTO WC1 DRAIN
SPROD
SPILLWAY LOCATION
BUND
ROCK SCOUR
PROTECTION
ACCESS RAMP
49m
ROCK SCOUR
PROTECTION
SEDIMENT DAM 1 VOLUME = ~26,600m³
SEDIMENT DAM 3 VOLUME = ~35,300m³
~ 44m
142 m
~ 177m
32
ROCK SCOUR
PROTECTION
33
34
35
32
36
37
33
SPILLWAY
LOCATION
38
34
35
NOEF EMBANKMENT
1m HIGH SAFETLY BUND BUILT
AROUND SEDIMENT DAM PERIMETER
36
SEDIMENT DAM 3 LAYOUT PLAN
1:1250
10.0m
3
SEDIMENT DAM 1 LAYOUT PLAN
-
1:1250
3m
TO TIE INTO
WC1 DRAIN
3
1 ON
SEDIMENT DAM DEPTHS ('D')
TYPICAL SEDIMENT DAM SECTION
1:250
3.2m
SEDIMENT DAM 3
3.5m
BIDIM A34 GEOFABRIC WITH 0.15m GRAVEL
BEDDING MATERIAL ABOVE AND BELOW AS
PER MANUFACTURERS SPECIFICATIONS
-
1.2m MAX DESIGN FLOW DEPTH
ROCK BAFFLES TO BE EMBEDDED
IN CHANNEL AND OFFSET TO
CREATE SNAKING DRAINAGE PATH
EXISTING
HAUL ROAD
DEPTH VARIES (2m MIN.)
DEPTH REQUIRED BASED ON
STORAGE REQUIREMENTS FOR
CONTAMINATED WATER CULVERT
10.0m
1 ON
SEDIMENT DAM 1
3
STILLING BASIN
SEDIMENT STORAGE ZONE
3m
CHUTE OUTLET SCOUR PROTECTION
TO CONTINUE INTO DAM AS SHOWN
DRAIN
0.5m GRADED RIP RAP SCOUR PROTECTION
~350mm-500mm (NOTHING FINER THAN 100mm)
CONSTRUCTED IN AN INTERLOCKING MATRIX
10m LENGTH OF
ROCK BAFFLE
'D'
SETTLING ZONE
1:250
EMBANKMENT
3
SECTION
BIDIM A34 GEOFABRIC WITH 0.15m GRAVEL
BEDDING MATERIAL ABOVE AND BELOW AS
PER MANUFACTURERS SPECIFICATIONS
EMBANKMENT
DRAIN
1m
3m
0.5%
1 ON
0.5m GRADED RIP RAP SCOUR PROTECTION
~350mm-500mm (NOTHING FINER THAN 100mm)
CONSTRUCTED IN AN INTERLOCKING MATRIX
SEDIMENT DAM SPILLWAY
TOP OF BUND
(BEYOND)
SEDIMENT DAM INLET
1 ON
3
SECTION
1
1:250
001
ROCK BAFFLES TO BE EMBEDDED
IN CHANNEL AND OFFSET TO
CREATE SNAKING DRAINAGE PATH
10.0m
HAUL ROAD
1 ON
3
BAFFLES OFFSET TO CREATE
SNAKING FLOWPATH
1 ON
0.5m GRADED RIP RAP SCOUR PROTECTION
~350mm-500mm (NOTHING FINER THAN 100mm)
CONSTRUCTED IN AN INTERLOCKING MATRIX
HDPE LINER WITH BIDIM A34 GEOFABRIC AND 0.15m
GRAVEL BEDDING MATERIAL ABOVE AND BELOW
AS PER MANUFACTURERS SPECIFICATIONS
TYPICAL ROCK BAFFLE LAYOUT PLAN
1.5m DEEP
STILLING BASIN
3
SECTION
2
1:250
002
10m BASE
1:500
3
CLIENT/PROJECT:
MCARTHUR RIVER MINE
SEDIMENT DAM & STILLING BASIN DESIGN
0.5m GRADED RIP RAP SCOUR PROTECTION
~350mm-500mm (NOTHING FINER THAN 100mm)
CONSTRUCTED IN AN INTERLOCKING MATRIX
PRODUCED BY:
HDPE LINER WITH BIDIM A34 GEOFABRIC AND 0.15m
GRAVEL BEDDING MATERIAL ABOVE AND BELOW AS
PER MANUFACTURERS SPECIFICATIONS
10
5
0
5
10
15
O'Kane
Consultants Pty Ltd.
20
Integrated Mine Waste Management and Closure Services
Specialists in Geochemistry and Unsaturated Zone Hydrology
25mm
OKC PROJECT NO.: 750/41
THIS DRAWING IS TO BE READ IN CONJUNCTION WITH OKC REPORT
DESCRIPTION
750/41
REVISIONS
REFERENCE
SCALE 1:1
DWG. NO.
NO.
A
DESCRIPTION
PRELIMINARY ENGINEERING DESIGN ISSUE FOR CLIENT REVIEW
DRN. BY:
APPD. BY:
DATE
SMW
PG
01.11.16
B
ENGINEERING DESIGN ISSUE
SMW
PG
21.11.16
0
FINAL ENGINEERING DESIGN ISSUE
SMW
PG
30.11.16
DRN. BY:
APPD. BY:
SCALE:
DATE:
S. WALKER
DATE:
P. GARNEAU
AS SHOWN
PAGE SIZE:
A3
30.11.16
TYPICAL SEDIMENT DAM SECTION
30.11.16
OKC RPT. NO.:
750/41
DWG. NO.:
750-41-004
REV.:
0
For further information contact:
O'Kane Consultants Pty Ltd
193D Given Terrace
Paddington QLD 4064
Australia
Telephone: (07) 3367 8063
Facsimile: (07) 3367 8052
Web: www.okc-sk.com