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PROJECT

EMERGENCY ACTION PLAN TOP SHED DAM - CUBBIE STATION

DIRRANBANDI, QUEENSLAND

PREPARED FOR CS AGRICULTURAL PTY LTD

DATE SEPTEMBER 2014

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DOCUMENT CONTROL DOCUMENT 11273 EAP ROD2F.docx TITLE Emergency Action Plan, Top Shed Dam – Cubbie Station, Dirranbandi, Queensland PROJECT MANAGER AUTHOR(S) CLIENT CS Agricultural Pty Ltd CLIENT CONTACT CLIENT REFERENCE

SYNOPSIS This report describes the Emergency Action Plan for the Cubbie Station Top Shed Dam.

REVISION HISTORY

REVISION(#( DATE( ( EDITION(BY( ( APPROVED(BY(

1 9/13

2 9/14

DISTRIBUTION

Copy No COPY HOLDER

1 CS Agriculture Pty Ltd

2 Dam safety, DEWS

3 G&S

11273 EAP ROD2F.DOCX / CS AGRICULTURAL PTY LTD – EMERGENCY ACTION PLAN, TOP DAM CUBBIE STATION 3

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CONTENTS

1! Introduction ...................................................................... 4!1.1! Site layout & Dam Details .................................................. 4!

2! Roles & responsibilities .................................................... 5!2.1! Notification listing .............................................................. 5!

3! Emergency conditions ...................................................... 7!4! Emergency events and action list .................................... 9!5! Dam failure hazard inundation information .................... 12!6! Emergency event reporting ............................................ 13!7! References ..................................................................... 14!8! Appendix A - Drawings ................................................... 15!

4( AGRICULTURE WATER ENVIRONMENT

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1 Introduction

This document provides details of an Emergency Action Plan (EAP) for the Cubbie Station Top Shed Dam, developed in accordance with DEWS (2013). This EAP defines responsibilities and provides response procedures designed to:

• Identify emergency conditions that could endanger the integrity of the dam and that would require immediate action;

• Prescribe procedures that should be followed by the dam owner and operating personnel in the event of an emergency; and

• Provide timely warning to appropriate emergency personnel for implementation of community protection measures, if deemed necessary.

1.1 Site layout & Dam Details Drawing no. 1 (Appendix A) shows the layout of the Top Shed Dam and identifies the immediate area of potential inundation.

Table 1 (below) provides details of the Cubbie Top Shed Dam, including referable dam status details as determined by Best (2007).

Table 1: Dam details Location

Official dam name: Top Shed Dam

Location relative to nearest town: 18km south west of Dirranbandi QLD

Location coordinates: 20o40’47”S, 148o03’08”E

Property description: Lots 3 & 4, Plan BEL5370

Local authority: Balonne Shire Council

Dam owner & operator: CS Agricultural Pty Ltd

Details

Purpose: Water supply - Irrigation

Construction type: Compacted earth fill

Maximum height: 9m

Dam crest length: 4,200m

Dam crest width: 5m

Embankment batter slopes: External: Internal:

3(H) : 1(V) 5(H) : 1(V)

Total storage capacity: 7,002ML

Freeboard above Full Supply Level (FSL): 1.5m

Referable dam status Assessed population at risk: 8 Failure impact rating: 1 ANCOLD Hazard classification: Significant

11273 EAP ROD2F.DOCX / CS AGRICULTURAL PTY LTD – EMERGENCY ACTION PLAN, TOP DAM CUBBIE STATION( 5

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2 Roles & responsibilities

CS Agricultural Pty Ltd is responsible for the surveillance, maintenance and operation of the Top Shed Dam. The persons responsible for implementing operational and emergency procedures are:

(1) Operations manager

or nominated delegate. Responsible for:

• Monitoring the dam during normal operations, major climatic events or other emergency situations;

• Implementing the Emergency Notification Procedure (see Figure 1 below);

• Initiating and terminating emergencies (see Section 4)

• Preparation and submission of Emergency Event Reporting (EER) (see Section 6)

(2) Workshop Manager


• Communication with PAR (see Figure 1);

• Evacuation procedures;

• Post-event communication of evacuation outcomes and headcount;

(3) Chief executive officer.


• Communication with wider (i.e. non-PAR) personnel and relevant parties (see Figure 1);

• Review/sign-off of EER;

• Communication with CS Agriculture Board.

2.1 Notification listing Figure 1 provides an Emergency Notification Procedure in the event that dam failure is imminent or in progress, with evacuation of the workshop and surrounding areas located downstream from the dam to be initiated.

For an emergency condition under an EAP, relevant entities who need to be notified are as follows (in order of priority):

(1) Workshop personnel (i.e. the persons whose safety or property may be threatened by the emergency condition);

(2) CS Agriculture CEO

(3) Non-PAR on-site personnel and visitors, dam design engineer

(4) Queensland Police Service (Emergency situations only)

(5) Balonne Local Disaster Management Group;

(6) the chief executive of DEWS

(7) CS Agriculture Board

Figure 1 below provides a notification flow chart with contact details (including alternative mode of contact) under activation of the EAP.


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Figure 1: Notification flow chart (EAP activation)

PRIORITY 3

PRIORITY 6

PRIORITY 5

PRIORITY 1

PRIORITY 4

PRIORITY 2

PRIORITY 1 WORKSHOP MANAGER

UHF Channel 13

OPERATIONS MANAGER UHF Channel 13

CEO UHF Channel 13

Dam design engineer

QUEENSLAND POLICE SERVICE

Dirranbandi 07 4625 8200 (alternative - Personel visit)

WORKSHOP PERSONNEL

Word-of-mouth / Personal Visit (Alternative - UHF channel 13)

Non-PAR on-site personnel UHF Channel 13

(Alternative - word-of-mouth/personal visit)

Balonne Local Disaster Management Group

PRIORITY 2

The chief executive of DEWS

1300 596 709 (emergency events)

Mailing address (EER))


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3 Emergency conditions

The updated Queensland dam safety legislation defines three types of emergency conditions comprising:

• A dam failure hazard • A downstream release hazard (including

spillway overflow, outlet releases, etc.) • An abnormal circumstance that potentially

indicates an increase in the likelihood of a dam failure hazard or downstream release hazard (e.g. an unusual amount of seepage from the dam).

Cubbie Top Shed Dam is a compacted earth fill “Turkey’s Nest” dam, with no purpose constructed spillway and standard operational approach based on maintenance of an FSL providing 1.5m freeboard (greater than the estimated Probable Maximum Precipitation (PMP) of 1,450 mm). This means that controlled reduction of storage levels will be undertaken as a standard response under any conditions in which the water level in the dam is above the FSL.

Maximum rates of pumped inflow are 350 ML/d at low storage levels (dam < 50% full) decreasing with increasing dam water levels to 100 ML/d at FSL. Under this maximum inflow rate, filling of the dam to embankment crest level from FSL would take approximately two weeks. Failure due to overtopping of the embankment crest level therefore does not represent a realistic dam failure hazard for Cubbie Top Shed Dam.

Outlet works are located on the northern wall of the dam with gravity-release via pipe at a maximum rate of 250 ML/d into a purpose-constructed supply channel system. The location of the outlet works and low rate of maximum release do not represent a downstream release hazard.

The emergency conditions relevant to Cubbie Top Shed Dam relate therefore only to those dam failure hazards caused by such events as piping failure, earthquake, explosion or other structural damage to the dam embankment (described further in Section 6.0). The development of the EAP has been based on a worst case condition of dam failure of the embankment most proximal to the workshop (and PAR).

Table 2 below has been adapted from the Emergency Action Planning for Referable Dams, Provisional Guideline (DEWS, 2013) and details of emergency conditions that are considered most likely to initiate a failure of Top Shed Dam. These conditions are also based on a comprehensive inspection of the dam undertaken by Allan Watson Associates (2011).

Cubbie Top Shed Dam is located entirely within the privately-owned Cubbie Station and there is no potential for closure of, or damage to, any public roads, railways or other infrastructure associated with any emergency condition that has the possibility of occurrence associated with the Top Shed Dam. The potential hazards associated with Top Shed Dam are limited entirely on on-farm infrastructure and personnel. All possible effects would be contained entirely on site, cause inundation of adjacent fields that would dissipate within a matter of hours.


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Table 2: Emergency conditions Emergency Condition General characteristic Monitoring/Action

Abnormal circumstance that

potentially indicates an

increase in the likelihood of a dam

failure hazard or downstream

release hazard (Seepage related

issues during elevated storage

level)

New or increased seepage areas identified in dam embankment: • Evidence of concentrated

discharge of seepage from any embankment surface with or without the presence of colour or loss of clarity due to suspended soil particles

• Water surface disturbances such as whirlpools (vortices) in reservoir (probably associated with significant downstream leakage, soft spots or boggy areas)

Monitoring: During routine inspection, elevated water level or after unaccountable increases in seepage flows, look for an emission point

Action (if emergency condition present):

Activate EAP (Table 2)

Dam failure hazard (Embankment

stability issues)

Defect observed in embankments, such as cracking, slumping or faults in

the transfer system; Earthquake, or other cause of potential structural damage to embankment(s)

Monitoring: During routine inspections or immediately after earthquakes - Inspect for evidence of

foundation movement or displacement adjacent to the dam

Action (if emergency condition present):

Activate EAP (Table 3)


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4 Emergency events and action list

Timely implementation of the EAP is crucial in order to ensure that the effectiveness of the plan, with appropriate warning systems imperative to reduce the risk of loss of life and property damage downstream from the dam. The emergency response procedures presented below provide the steps to identify and manage emergency conditions events that can lead to failure of the dam. The response procedures have been developed consistent with the staged response approach of:

• Alert • Lean forward • Stand up • Stand down

Actions associated with emergency conditions relevant to Top Shed Dam are provided in:

• Table 2 - Seepage related issues (leading to piping failure)

• Table 3 - Embankment stability issues (leading to dam failure)


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Table 2: Actions and notifications during emergency conditions (Seepage related issues) Emergency condition LEVEL

Observations Notifications (see Figure 1) ACTIONS

ALERT New or increased seepage areas identified in dam embankment

Priority 1 and 2 entities

Look for source of seepage record all relevant observations and measurements

LEAN FORWARD

Detection of signs of cloudy water in seepage - look for the source of cloudy water

Priority 1 – 3 entities Timed updates:

• beginning and end of work-shifts

• prior to personnel coming to or leaving from Cubbie Station

Immediately commence drawdown of dam water level through transfer system Evacuation of all PAR from potential area of inundation Continue monitoring and record all relevant observations and measurements If it can be done safely, undertake remedial works as per advise from Dam Design Engineer

STAND-UP

Seepage developing further. Discharge is clouding and increasing (piping failure has started) Progressive internal erosion of the embankment or foundation to form an open conduit or pipe

Notifications to Priority 1-6 entities. Timed updates:



Continue drawdown of dam water level Continue monitoring and record all relevant observations and measurements If it can be done safely, undertake remedial works as per advise from Dam Design Engineer

STAND-DOWN

Failure occurs and the reservoir drains or it is determined seepage is manageable and is not going to develop into a failure condition.

All priority entities

Issue a final notification advising the end of the emergency event Prepare and submit EER


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Table 3: Actions and notifications during emergency conditions (Embankment stability issues) Emergency condition LEVEL

Observations Notifications ACTIONS

ALERT

Identification during routine inspection of initial signs of embankment distress such as cracks or scarps near the crest and bulges at the toe

Priority 1 and 2 entities Record all relevant observations and measurements

LEAN FORWARD

Defects visible and intensifying External conditions where safety of dam is potentially impaired (earthquake, etc)

Priority 1 – 3 entities Timed updates:


• prior to personnel coming to, or leaving from Cubbie Station

Immediately commence drawdown of dam water level through transfer system Evacuation of all PAR from potential area of inundation Continue monitoring and record all relevant observations and measurements If it can be done safely, undertake remedial works as per advise from Dam Design Engineer

STAND-UP

Loads on embankment increasing or cracking/ deformation increasing to state where the safety of the dam is significantly impaired

Notifications to Priority 1-6 entities. Timed updates:



Continue drawdown of dam water level Continue monitoring and record all relevant observations and measurements If it can be done safely, undertake remedial works as per advise from Dam Design Engineer

STAND-DOWN

Failure occurs and the reservoir drains or remedial works completed and risk of failure drops significantly

All priority entities

Issue a final notification advising the end of the emergency event Prepare and submit EER


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5 Dam failure hazard inundation information

Dam failure analyses were undertaken to simulate worst-case failure conditions of Cubbie Top Shed Dam, comprising piping failure during a PMP rainfall event. Dam failure inundation maps for the worst-case scenario are provided in Appendix A, comprising:

• Maximum inundation depth and extent map (Drawing no. 2)

• Timing (from initial dam failure) of maximum inundation depth downstream of dam failure map (Drawing no. 3)

• Maximum flood hazard (velocity x depth) map (Drawing no. 4)

The area likely to be affected from dam failure due to the two identified emergency conditions (Seepage and Embankment stability) should be less than the inundation from the dam failure due to PMP rainfall event as shown in drawing 2. However the PAR that will be affected during these emergency conditions will be the personnel present in the workshop during the event. The notification and evacuation to workshop personnel based on priority are included for both the emergency events.


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6 Emergency event reporting

The requirement for the preparation and submission of an emergency event report (EER) is triggered at the ‘stand up’ level. The provisions of the Act require such emergency event reports to:

(a) describe the emergency event to which the report relates; and

(b) describe the implementation of the approved emergency action plan for the dam in relation to the emergency event, including relevant details of—

(i) communications made and actions taken in response to the emergency event; and

(ii) monitoring of the dam and the area affected or potentially affected by the emergency event; and

(c) describe any damage to the dam, including by reference to photographs of the damage; and

(d) state whether and to what extent any damage to the dam has been caused or contributed to by the emergency event; and

(e) include an assessment of whether and to what extent the approved emergency action plan effectively dealt with the emergency event; and

(f) recommend any changes to the approved emergency action plan that would allow the plan to deal with a similar emergency event more effectively; and

(g) include details of any other matter that is relevant to the emergency event or how it was dealt with under the emergency action plan; and

(h) include any other relevant matter prescribed under a regulation.

The Act requires an emergency event report to be prepared by dam owners and submitted to the chief executive within 30 business days after the end of an event. An emergency event ends:

(a) if the event is a dam failure hazard that has happened—when the owner of the dam reasonably considers the hazard no longer poses a risk to the dam and ‘Stand down’ is activated; or

(b) if the event is a downstream release hazard that has happened—when the owner of the dam reasonably considers the hazard no longer poses a risk to the safety of persons or property.

14(( AGRICULTURE WATER ENVIRONMENT

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7 References

Allan Watson Associates (2011), Cubbie Station Top Shed Dam Comprehensive Inspection report and Emergency Action Plan. Cubbie Group Limited, April 2011.

, (2007), Failure Impact Assessment, Cubbie Station Top Shed Dam (1487). Cubbie Group Ltd, Dirranbandi. April 2007

Department of Energy and Water Supply (DEWS) (2013), Emergency Action Planning for Referable Dams. State of Queensland, June 2013, Provisional guidelines.

Department of Natural Resources and Mines (DNRM) (2002), Queensland Dam Safety Management Guidelines. February 2002.

Gilbert & Sutherland Pty Ltd (2013), Acceptable flood capacity (AFC) report – Top Dam, Cubbie Station. Letter report dated 27 September 2013.


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8 Appendix A - Drawings

Workshop

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