Attachment 5: Construction Methodology Report€¦ · salty lagoon rehabilitation plan:...

Attachment 5: Construction Methodology Report

Richmond Valley Council

Salty Lagoon Rehabilitation Program

Preliminary Construction Concept for the Closure ofthe Artificial Channel

09-018

September 2010

Suite 6, 26-54 River StreetPO Box 7059BALLINA NSW 2478

Telephone: 02 6686 0006Facsimile: 02 6686 0078

© Copyright 2010 Hydrosphere Consulting

SALTY LAGOON REHABILITATION PLAN: CONSTRUCTION CONCEPT

PROJECT 09-018–SALTY LAGOON REHABILITATIONS PLAN: CHANNEL CLOSURE CONCEPT

REV DESCRIPTION AUTHOR REVIEW APPROVAL DATE

A Draft for RVC review R. Campbell, K. Pratt,M. Howland,

M. Howland M. Howland 1 /9/10

0 Draft Final for contractorcomment

R. Campbell M. Howland M. Howland 15/9/10

1 Final R. Campbell M. Howland M. Howland 27/9/10

Channel Closure Construction Concept Rev 1.docx

Disclaimer

This report has been prepared on behalf of and for the exclusive use of Richmond Valley Council,

and is subject to and issued in accordance with the agreement between Richmond Valley Council

and Hydrosphere Consulting. Hydrosphere Consulting accepts no liability or responsibility

whatsoever for it in respect of any use of or reliance upon this report by any third party.

Copying this report without the permission of Richmond Valley Council or Hydrosphere Consulting

is not permitted.


Channel Closure Construction Concept Rev 1.docx Page 1

TABLE OF CONTENTS

Table of Contents.................................................................................................................................... 1

1. Introduction...................................................................................................................................... 3

1.1 Background and Aims .............................................................................................................. 3

1.2 Scope of this Report ................................................................................................................ 3

2. Project Characteristics and Constraints ............................................................................................ 4

2.1 Environmental.......................................................................................................................... 4

2.2 Cultural Heritage...................................................................................................................... 5

2.3 Public Access .......................................................................................................................... 5

3. Design Principles ............................................................................................................................. 7

3.1 Reversibility ............................................................................................................................. 7

3.2 Flexible Management of Connectivity....................................................................................... 7

3.3 Structural Integrity.................................................................................................................... 7

3.4 Public Amenity and Safety ....................................................................................................... 8

3.5 Resistance to Vandalism.......................................................................................................... 8

3.6 Low Construction and Maintenance Impact .............................................................................. 8

3.7 Environmental Sensitivity ......................................................................................................... 9

3.8 Cultural Sensitivity ................................................................................................................... 9

3.9 Cost Effectiveness................................................................................................................... 9

4. Closure Options ............................................................................................................................. 10

4.1 Longevity............................................................................................................................... 11

4.2 Proportion of Artificial Channel Filled...................................................................................... 11

4.3 Hydrological Cut-Off and Structural Barriers........................................................................... 12

4.4 Fill Material............................................................................................................................ 13

4.5 Site Access............................................................................................................................ 16

4.6 Materials Transfer.................................................................................................................. 17

4.7 Water Exchange .................................................................................................................... 17

5. Preferred Artificial Channel Closure Concept .................................................................................. 19

5.1 Preferred Concept ................................................................................................................. 19

5.2 Site Configuration During Construction .................................................................................. 22



5.3 Fill Materials and Source........................................................................................................ 24

5.4 Equipment and Materials Requirements................................................................................. 24

5.5 Infrastructure Siting and Construction Timing ......................................................................... 24

5.6 Work Sequence and Duration ................................................................................................ 25

5.7 Vegetation Clearing and Site Disturbance .............................................................................. 25

5.8 Site Rehabilitation.................................................................................................................. 26

5.9 Finished Site.......................................................................................................................... 26

5.10 Reversibility ........................................................................................................................... 27

5.11 Environmental Management .................................................................................................. 28

6. Next Steps ..................................................................................................................................... 30

7. References .................................................................................................................................... 31

FIGURES

Figure 1: Site Area and Constraints......................................................................................................... 6

Figure 2: Project Timeline...................................................................................................................... 11

Figure 3: Proportion of Artificial Channel Filled – Plan View................................................................... 12

Figure 4: Hydrological/Structural Barrier – Longitudinal Elevation .......................................................... 13

Figure 5: Potential Sand Extraction Sites............................................................................................... 14

Figure 6: Plan View............................................................................................................................... 21

Figure 7: Cross-Section A-A showing hydrological/structural barrier and vegetation............................... 21

Figure 8: Cross-Section B-B showing filled Artificial Channel initial profile and settled final profile. ......... 22

Figure 9: Site Configuration................................................................................................................... 23

Figure 10: Artist’s Impression ................................................................................................................ 26

Figure 11: Anticipated surface water drainage pathways of closed Artificial Channel ............................. 27

TABLES

Table 1: Comparison of Potential Fill Extraction Sites ............................................................................ 15

Table 2: Fill quantity required ................................................................................................................ 24

Table 3: Equipment Requirements ........................................................................................................ 24

Table 4: Indicative Construction Program .............................................................................................. 25

Table 5: Environmental Management .................................................................................................... 28



1. INTRODUCTION

1.1 Background and Aims

Hydrosphere Consulting has been engaged by Richmond Valley Council (RVC) to develop the

Implementation Strategy for the Rehabilitation of Salty Lagoon. A key component of the strategy is to

close the Artificial Channel connecting Salty Lagoon and Salty Creek on a trial basis to increase the

ability of the Salty Lagoon ecosystem to effectively process on-going discharge from the Evans Head

STP and to improve ecosystem health, remove the trigger for large scale draining events and reduce the

potential for fish kills. The Department of Environment, Climate Change and Water (DECCW) and NSW

Industry and Investment (I&I) have provided in principle support for the Rehabilitation Strategy.

The Implementation Strategy will document:

The approvals process;

The environmental monitoring and adaptive management protocols;

The post-implementation environment; and

A risk assessment and public use strategy for the closure of the Artificial Channel between Salty

Lagoon and Salty Creek.

As part of this work, Hydrosphere Consulting is also required to provide a preliminary construction

methodology, describe access arrangements and document the main features of the proposed closure

structure. It is intended that this will provide sufficient project definition to enable regulatory agencies to

advise the scope of the approval requirements and to highlight construction and timing constraints that

may influence the implementation of the project.

1.2 Scope of this Report

This report will identify a credible concept for closure that will document the broad design principles,

address the known environmental constraints and identify the key issues.

This report provides a discussion of the key design and construction considerations, namely:

Design principles;

Preliminary concept design and consideration of alternatives ;

Construction materials; and

Site constraints, construction requirements and site access arrangements .

A full analysis of construction feasibility or project risk is not intended but will be discussed where they are

apparent. It is also recognised that changes in construction concepts or methodologies may be proposed

by the eventual construction contractor, however, the key aim of this engagement is to provide a concept

that describes the key aspects of the proposal and will allow progression of the approvals phase of this

project. Further design and logistics assessment may be required at later stages of the project before the

scope of works for construction can be fully finalised.



2. PROJECT CHARACTERISTICS AND CONSTRAINTS

The Salty Lagoon, Salty Creek and the Artificial Channel are located within the Broadwater National Park

which provides a range of habitats and species of conservation significance. Salty Creek is an ICOLL that

periodically opens to the ocean at Airforce Beach and is characterised by a highly variable water level

and salinity regime. Salty Lagoon was naturally separated from Salty Creek by a low-lying land bridge

approximately 120m wide and hence was a predominantly freshwater and relatively stable ecosystem.

The Artificial Channel was excavated in the early 1970’s and provides a continuous connection between

the two water bodies at all water levels, thereby having a profound effect on the ecology of Salty Lagoon.

2.1 Environmental

The environmental characteristics of the site have been assessed and documented in a series of

ecosystem monitoring reports (e.g. Hydrosphere Consulting 2009 and 201 0) including water quality and

hydrology, diatoms, macroinvertebrates, fish, frogs, waterbirds, flora and weeds.

Salty Lagoon provides habitat for a wide range of flora and fauna species protected under a number of

legislative provisions. Environmental constraints that are particularly relevant to the construction of the

Artificial Channel closure are:

The entrance to Salty Creek is a known nesting site for listed migratory birds as well as providing

habitat for several species throughout the year. Nesting season occurs between August and

January;

Salty Lagoon water levels appear to be closely coupled to groundwater levels, indicating

groundwater as the primary catchment input pathway . Inputs are greatest when the wet season

has primed groundwater levels across the catchment. Water level can fluctuate significantly in

response to catchment inflows and Salty Creek entrance opening events;

The substrate in the vicinity of the Artificial Channel and downstream of Salty Creek to the

entrance is predominantly fine sand overlain by a thin layer of organic matter and, interspersed

with outcrops of indurated sands (coffee rock). Poor water quality episodes in Salty Lagoon and

to a lesser extent in Salty Creek associated with nutrient enrichment, rapid draining of the system

and seawater intrusion, has been extensively documented. Disturbance of the poorly oxygenated

sediments which are known to contain high levels of nutrients should be minimised during

construction to prevent poor water quality episodes (e.g. algal blooms, low dissolved oxygen);

The Salty Lagoon and Salty Creek area are part of the Broadwater National Park and contain

significant vegetation communities including salt marsh (dominated by Sporobolus virginicus).

Due to the extent of vegetation cover and presence of significant vegetation, vehicular access to

the Artificial Channel site is not recommended and therefore access via Salty Creek (from

Airforce Beach) is preferred. Access by helicopter is not favoured due to the potential disturbance

of fauna, particularly birds, in the area;

Large seas and high tides occur on Airforce Beach, creating a potential impediment to semi -

permanent construction sites and fencing. Equipment types and work scheduling will need to

consider the impact of tides and waves on safety and protection of construction equipment;



Invasion by non-native plant species has been identified by stakeholders as a significant threat to

the ecological values of Salty Lagoon and Broadwater National Pa rk. There is a need to ensure

that that the proposed activities do not increase the risk of weed infestation; and

Fish passage between Salty Lagoon and Salty Creek is currently facilitated by the Artificial

Channel, allowing estuarine species to enter into the lagoon. Trapping of estuarine fish in Salty

Lagoon at the time of closure is to be prevented as much as possible.

Figure 1 shows Salty Lagoon, Salty Creek and Airforce Beach and the key project constraints.

2.2 Cultural Heri tage

Salty Lagoon has a rich cultural history. Aboriginal people occupied the area for thousands of years prior

to European settlement, and the park was hunted and fished widely. A search of the DECCW AHIMS

database revealed evidence of Aboriginal occupation with three Aboriginal objects or places recorded in

or near Salty Lagoon. The area is part of the Bundjalung Nation and is subject to a registered Native Title

Claim. Previous consultation with Aboriginal representatives has established that the site is a particularly

important women’s site. This may have specific implications for management of the system and the

construction of the Artificial Channel closure but any constraints in this regard have not been identified to

date. Continued consultation with the Aboriginal community, particularly the Native Title claimant utilising

the services of the NTS Corp will need to be undertaken to ensure the proposed activities remain

compatible with the wishes of the Aboriginal people.

2.3 Public Access

Salty Lagoon is public land, accessible by the general public. Recreational activities (fishing, canoeing,

bushwalking etc.) are popular in the National Park and beach areas.

The Broadwater National Park Draft Plan of Management (DPOM) (NPWS, 2010) outlines a number of

management principles including to ‘provide for sustainable visitor use and enjoyment that is compatible

with conservation of natural and cultural values’. The walking track access from Broadwater Road was

closed by NPWS in 2005, although the system remains accessible via Airforce Beach, which has a high

level of beach traffic (pedestrian and four wheel drive). Public access along Airforce Beach should be

maintained.

It is likely that there are a moderate number of visitors to Salty Creek and Salty Lagoon, especially in the

area of Salty Creek entrance and the Artificial Channel itself, which is within a short-walking distance of

the beach (approximately 500m) along Salty Creek. Construction activity may arouse curiosity and

restriction of access to work areas is expected to be required to minimise public safety hazards and to

prevent issues such as vandalism.



Figure 1: Site Area and Constraints



3. DESIGN PRINCIPLES

The closure of the Artificial Channel needs to be designed and undertaken in such a way as to achieve

the following design principles.

3.1 Reversibility

The risks associated with the proposed Rehabilitation Strategy are:

The predicted environmental benefits of Artificial Channel closure do not eventuate;

The environmental impacts of the closure are more pronounced than anticipated; or

There is continued degradation in environmental condition with no expectation of reversal in the

future.

Under these scenarios, the Artificial Channel closure would be deemed unsuccessful and an alternative

rehabilitation strategy would be pursued. If required, removal of the Artificial Channel closure should be

achievable in an environmentally sound and cost-effective manner. This may involve the modification or

removal of the Artificial Channel closure.

In principle support for the project (from DECCW) is conditional on the closure having the scope for

practical modification or removal if required. The closure of the Artificial Channel will be undertaken

initially on a trial basis to enable monitoring to confirm the ability of the closure to achieve the project

objectives.

3.2 Flexible Management of Connectiv ity

DECCW’s in principle support for the project is conditional on the ability to enable flexible management of

connectivity between Salty Lagoon and Salty Creek as required. Active management of Salty Lagoon is

required to allow manipulation of water levels and water exchange with Salty Creek if considered

necessary.

An adaptive management protocol is being developed as part of the post -closure monitoring program

which will set out monitoring requirements, triggers and management responses and responsibilitie s,

should action be required. The process for manipulating water levels or providing water exchange will be

detailed in the plan.

3.3 Structural Integrity

The Artificial Channel closure should be constructed in such a way to maintain its structural integrity in the

long-term (or the design life of the structure – see section 4.1). The risks to structural integrity are

dependent on the closure method, however the following are considered the key factors:

Seepage erosion of any embankments caused by high groundwater gradients between Salty

Lagoon and Salty Creek. Seepage could lead to piping erosion of the embankment leading to

failure of the structure;

Scour of embankments and fill material through overtopping flows;



Corrosion or rotting of structural elements;

Sinking/settlement of elements;

Erosion of unconsolidated sediments due to wind or rain; and

Public access to banks and track formation which may compromise the protective vegetative

cover and lead to preferential drainage pathways.

3.4 Public Ameni ty and Safety

The closure construction should be designed and undertaken in a way that is consistent with the

principles of the National Park and gives due consideration to amenity and public safety (refer Section

2.3). The Artificial Channel closure itself should be inherently safe and should not rely on long-term

restriction of access or signage to increase public safety.

Support for the proposal from DECCW is conditional on further discussion on the implications of th e

rehabilitation work on recreational use of Salty Lagoon and development of a communications strategy

regarding any human health implications (due to water quality), monitoring of public health and

development of triggers.

3.5 Resistance to Vandalism

The closure should be designed and constructed in such a way to minimise the attractiveness and

opportunities for vandalism. Vandalism is a concern as damage to the structure and associated

equipment may affect proper function of the closure and may result in risk to public safety as well as

environmental issues. If monitoring equipment is installed in the vicinity of the structure, damage to

equipment or theft is an additional risk. To minimise the risk of vandalism the closure structure should:

Be as natural looking as possible to blend into the existing environment, avoiding large artificial

structures that attract attention. This is not only a requirement of keeping within the objectives of

the Broadwater National Park, but will also minimise the attractivenes s for vandalism;

Minimise the number of vulnerable or removable parts;

Utilise fencing and signage to restrict access during construction as necessary; and

Have security measures installed where necessary such as cages or boxes to protect equipment.

3.6 Low Construction and Maintenance Impact

Construction should be carried out in a way that minimises impacts to fauna and flora, cultural and

ecological values of the site and public amenity. Appropriate planning and establishment of access

routes, and considerations for waste management, noise, vibration, water quality and hydrological issues

need to be included in the design.

Ongoing operation and maintenance requirements should also have minimal impacts and be as simple

and cost effective as possible.



3.7 Environmental Sensitiv ity

The Artificial Channel closure design and operation is required to consider the sensitivity of the

environment (refer Section 2.1). In principle support for the project from DECCW and I&I NSW is

conditional on key points relating to environmental aspects as follows:

Construction impact should be minimised;

Development of an adequate environmental post-closure monitoring program is required

including triggers and adaptive management responses should adverse ecological conditions be

detected as a result of the works;

A suitable weed control program (at the works site) is required;

An Environmental Management Plan should be developed for the construction phase to

minimise environmental harm (e.g. spills, vegetation disturbance, sediment disturbance, turbidity

control); and

Approvals or concurrence required under the Fisheries Management Act 1994 for any works

that constitute “dredging or reclamation’ and/or “harm” marine vegetation.

3.8 Cultural Sensi tiv ity

The Artificial Channel closure design and construction phase should be sensitive to cultural values of the

site (refer Section 2.2). DECCW’s in-principle support for the project is conditional on:

Ongoing and active consultation with stakeholders including Native Title Claimants; and

Discussion of future recreational implications and development of a recreation use strategy.

Ongoing consultation with stakeholders and particularly Aboriginal representatives will be a key

requirement throughout the design and implementation of the closure to ensure compatibility with these

values. A recreational use strategy is being developed as part of the Implementation Plan for the

Rehabilitation Strategy.

3.9 Cost Effectiveness

The closure method and construction works should achieve all the above design principles while

maintaining a priority on achieving cost effective solutions for RVC. This incorporates design and

feasibility studies, construction and monitoring and maintenance phases of the work.



4. CLOSURE OPTIONS

A range of closure options have been considered with respect to :

Longevity:

o temporary, or

o permanent (but removable);

Proportion of Artificial Channel filled:

o all, or

o partial;

Hydrological barrier material:

o concrete,

o sheet pile,

o plastic sheeting,

o clay/bentonite,

o organic (e.g. leaves, straw), or

o geofabric (biodegradable or permanent);

Fill material:

o none (e.g. sheet piles only),

o beach sand,

o Salty Lagoon or Salty creek sand, or

o imported material (sand, clay, etc.);

Site access route for machinery and materials import:

o ground access along the shallow margins of Salty Creek,

o ground access over the dunes,

o water access via Salty Creek,

o air access via helicopter.

Materials transfer methods:

o dredge/slurry pump,

o truck,

o barge via Salty Creek, or

o helicopter; and

Water exchange:

o permanent pipes and valving,

o spillways,

o sluices or gates,

o temporary siphons, or

o permanent siphons.

The potential range of options is discussed in the following sections.



4.1 Longevity

Closure of the Artificial Channel can be undertaken in one of two ways:

A staged closure such that a temporary closure is put in place for the duration of the trial period

(nominally 5 years), with a view to replacing or augmenting this closure to its permanent

configuration after this trial period. Assuming the trial is successful, this stra tegy would require

that additional works are undertaken at the end of the trial period to construct the permanent

closure; or

Artificial Channel closure in a permanent configuration that does not require ancillary works in

order to make the closure permanent, but is able to be reversed.

The staged closure of the Artificial Channel has some advantages in that the design can be optimised for

easy removal and that the volume of fill material and structures can be reduced to account for the

reduced longevity requirements. This may dictate that an easily removable structure (e.g. sheet piling as

discussed in Section 4.3) is utilised initially, with a different technique for the final closure (e.g. sand fill).

Staging of construction in this way may be initially cheaper (with fewer materials) but more expensive

over the full life of the project should permanent closure be the desired outcome. The key disadvantage

with this approach is that on-ground disturbance will be duplicated if permanent closure is eventually

agreed upon.

Closure of the Artificial Channel in a permanent configuration avoids the need to undertake follow-up

works at the end of the trial period, but, depending on the method, may result in a structure that is not

optimised for removal, and hence reversal of the closure, if required, is likely to be more expensive. A

permanent configuration allows habitat restoration works to be undertaken immediately and provides

advantages in terms of protection of environmental and cultural sensitivity due to reduced ground

disturbance.

Figure 2: Project Timeline

4.2 Proportion of Ar tificial Channel Filled

The degree to which the Artificial Channel is filled is largely dependent on the fill material (Section 4.4),

the hydrological cut-off strategy (Section 4.3) and the longevity of the structure (Section 4.1).

2010 2012 20172014

Temporary

Permanent



A partially filled Artificial Channel would require a hydrological/structural barrier at the Salty Lagoon end of

the channel (refer Section 4.3) and would negate the need to import large amounts of fill.

A completely filled Artificial Channel is also likely to require a hydrological/structural barrier at the creek

end of the channel (to contain any fill material). A completely filled Artificial Channel would mimic the

natural conditions prior to the dredging of the Artificial Channel. Channel filling may also be utilised to

enhance public safety, increase aesthetic values and provide opportunities for habitat restoration and

revegetation.

Figure 3: Proportion of Artificial Channel Filled – Plan View

4.3 Hydrological Cut-Off and Structural Barriers

A hydrological cut-off may be required to prevent seepage erosion and piping through the sediment due

to the groundwater gradient between the Salty Lagoon and Salty Creek. Potential artificial barriers include

sheet piling, concrete barriers and impermeable (or semi-permeable) sheeting. The use of sheet piling or

concrete barriers would negate any structural need for fill material but would create a visually intrusive

structure that is out of character with the rest of the area, unless additional fill and vegetative cover was

able to be established. Exposed sheet piling by itself would achieve the structural and short-term

hydrological aims, but may present an unacceptable public safety risk.

A semi-permeable barrier would facilitate natural clogging of the sand to provide long term erosion

protection whilst allowing a natural rate of groundwater exchange across the barrier. Geofabric or natural

materials (such as hessian sand bags) and natural barriers (such as organic matter) would be more

consistent with the character of the area and would support revegetation and habitat restoration.

Biodegradable materials could be used to provide the barrier until the natural processes are established.

A structural barrier may also be required during placement of any fill to contain material at the fill site and

prevent erosion however it is likely that natural stability of the fill material will be sufficient during

placement of the fill (once the natural angle of repose is formed). Options similar to the hydrological cut-



off could be provided. Ideally, this barrier would be buried by the fill and would be made of natural or

biodegradable fibres. In this case, the barrier may remain in place after filling as long as the character of

the area was maintained. A natural material such as biodegradable sand bags would achieve both the

structural barrier and hydrological cut-off. Sand bags would need to be either filled and brought to site or

filled at the site (e.g. with beach sand, refer Section 4.4).

The need for hydrological or structural barriers would be determined during the final design stage (refer

Section 6).

Figure 4: Hydrological/Structural Barrier – Longitudinal Elevation

4.4 Fill Material

The Artificial Channel volume to be filled is estimated at 2900 m3 with the approximately trapezoidal

channel averaging 110m long, 15m wide and 2m deep. Initial fill will be required to fill sandbags, if used,

prior to the bulk transfer of fill.

The use of sand sourced locally from either Airforce Beach, the Lagoon or Creek would be cost-effective

compared to importation of fill. Airforce Beach provides a source of suitable clean fill although sand

particles are likely to be coarser and have less organic content than the natural sediments in the vicinity

of the Artificial Channel. Sediments sourced from within Salty Lagoon or Salty Creek are more likely to

match the native sediments but it is considered that disturbance is undesirable (turbidit y plumes, nutrient

Bed of Artificial Channel

SaltyLagoon

Hydrological barrier

Salty Lagoon water level

Partial Closure

Salty Creek water level

Natural Surface

Bed of ArtificialChannel

SaltyCreek

SaltyLagoon

Hydrological barrier

Salty Lagoon water level

Salty Creek water level

Structural barrierNatural Surface

Bed of Artificial Channel

Full Closure

SaltyCreek

Fill

Artificial Channel

Artificial Channel

S N



release, deoxygenation of the water column), deepening of Salty Lagoon is to avoided (shallow areas are

more likely to have increased benthic micro algal rather than water column algal growth) and deepening

of Salty Creek may exacerbate bank erosion.

Extraction from the beach/Salty Creek entrance is more desirable as the area is geomorphologically

active and natural sand accretion processes are likely to replace the sand removed within a

comparatively short timeframe. Nesting and roosting habits of migratory birds would need to be

considered in the timing and location of sand extraction from this area (refer Section 2.1).

Importation of fill provides opportunities to source any required grade or type of material but this is

expected to be more expensive and require large numbers of truck movements along Airforce Beach than

local extraction of fill. The trucking of fill along Airforce Beach would be regarded as a risk to public safety

and beach significantly reduce public amenity.

Potential local sand extraction sites are shown in Figure 5. Key considerations are available area,

proximity to water supply (for slurry pumping, refer Section 4.6), impact on migratory birds and public

safety.

Figure 5: Potential Sand Extraction Sites

A comparison of the sites (and importation of fill) is given in Table 1.



Table 1: Comparison of Potential Fill Extraction Sites

Consideration A – Lagoon B – Creek C – Entrance D - Beach Imported Fill

Site availability Suitable. Land

ownership issues

to be confirmed.

Suitable. Land

ownership issues

to be confirmed.

May be subject

to waves and

tides. Potentially

limited to low

tides only. Land

ownership issues

to be confirmed.

May be subject

to waves and

tides. Potentially

limited to low tide

time only. Land

ownership issues

to be confirmed.

To be sourced.

Proximity to

Artificial

Channel

<50m <50m 500m 600m – 1km Requires over

300 truck loads

to transport

required quantity

Quality of fill Lagoon

sediments similar

to Artificial

Channel

Creek sediments

similar to

Artificial Channel

Fine beach

sands

Fine beach

sands

Any quality

available

Site

disturbance

Excavation of

lagoon

sediments,

potential release

of nutrients and

deoxygenation.

Excavation of

creek sediments,

potential release

of nutrients and

deoxygenation.

Minimal long

term impacts as

entrance is

subject to high

levels of natural

sand movement.

Minimal long

term impacts as

beach areas are

subject to natural

sand movement.

Extensive truck

movement but

minimal long

term impacts as

beach areas are

subject to natural

sand movement.

Longer term

impact on

water quality

in Lagoon/

Creek

Dredged area

would create

deeper water

and poorer light

penetration

resulting in

potential

localised

degradation.

Dredged area

would create

deeper water

and poorer light

penetration

resulting in

potential

localised

degradation.

Potential for

increased bank

erosion

Nil Nil Nil, providing fill

was of suitable

quality

Proximity to

water supply

Available from

Creek.

Available from

Creek.

Available from

Creek entrance.

Available from

Creek entrance.

Fill to be

transported to

creek entrance

for watering.



Consideration A – Lagoon B – Creek C – Entrance D - Beach Imported Fill

Impact on

migratory

birds

Nil Nil Must be timed to

avoid nesting

season. Area to

be rehabilitated

(e.g. levelled to

ensure no

ponding of

nesting site)

Minimal, if

nesting area is

avoided.

Must be timed to

avoid nesting

season.

Public

safety/amenity

Minimal public

access.

Minimal public

access.

May be visible to

public using

beach.

Visible to public

using beach.

Visible to public

using beach.

Increased risk to

public safety.

4.5 Site Access

Ground access to the entrance to Salty Creek would be via the 4WD access ramp to Airforce Beach

(approximately 2.8km along the beach) to the entrance of Salty Creek. Public safety will need to be

considered for all vehicular movements. Depending on tide heights, access may be restricted to low tide

times to ensure appropriate clearance from other beach users.

The Artificial Channel site is located approximately 500m inland from Airforce Beach along Salty Creek. A

walking track is available in the dune areas although some sections are steep and contain dense

vegetation which would need to be trimmed to allow safe walking access to the site. Construction

personnel can access the Artificial Channel site via the walking track or by small boat along the creek.

Vehicular access via this route would entail removal of the bollards at the eastern end of the track and

establishment of a cleared track over the last part of the dune and through vegetation immediately to the

east of the Artificial Channel. In this case, cut and fill of the western edge of the dune face would be

required to achieve appropriate grades for vehicle access and would result in a large dis turbance

footprint. Restoration of the pre-construction landform and vegetative cover would be a large overhead for

the project and therefore this mode of access is not favoured.

The banks of Salty Creek are heavily vegetated with some areas of high/steep dune. The Creek margins

are shallow but narrow. Flow in Salty Creek is influenced by tides and entrance breakout events. Large

machinery (e.g. 20 tonne excavator) is likely to be able to traverse a shallow route along the banks/bed of

Salty Creek to reach the Artificial Channel site, however water depths are likely to restrict unassisted

access for smaller machinery (e.g. bobcat).

Water access via Salty Creek is the preferred method to convey equipment to the Artificial Channel.

Although it is likely that large earth moving equipment could reach the site unassisted, the scale of the

project is not likely to require this size of machine. It is considered that a bobcat could be transported to

site with the aid of a shallow draft barge floated along Salty Creek and would result in minimal impact.

Similarly, any other equipment (e.g. slurry pumping pipelines) could be transported and deployed directly

from a mobile shallow draft barge.



Air access via helicopter is expected to be more expensive and would require a suitable dry, level landing

area, away from trees flying debris and other obstructions. A suitable landing area may be available

within the Lagoon (once drained) at the entrance to the Artificial Channel. Aircraft create the potential for

noise impact on fauna in the area and increases the risk of issues such as bird strikes.

4.6 Materials Transfer

Construction materials may include hydrological/structural barrier materials, erosion/sedimentation

controls and fill material. Apart from fill material, it is considered that transfer by shallow draft barge or

boat along Salty Creek is the most appropriate method. If a barge is utilised for site access, this could

also be used for materials transfer with imported fill material transferred in skips, or similar, on top of the

barge. A method of transfer from the barge to the fill site, such as slurry pump or bobcat, would still be

required and the volume of sediment transferred in this way would be restricted by the laden draft of the

barge along shallow sections of Salty Creek.

The use of trucks or helicopters to transport materials to the Artificial Channel would require similar

considerations as site access (refer Section 4.5). Given the volume of fill required to completely fill the

Artificial Channel ground (i.e. truck) transfer of fill to the site would lead to a high level of disturbance that

would be disproportionate to the scale of the work to be completed.

Sand transfer is likely to be most efficient utilising a slurry pump and temporary pipeline system to

transfer fill from the source area to the Artificial Channel site. This method will avoid heavy equipment

movements with the Salty Creek and will minimise the need for site rehabilitation due to access. Pumping

of slurry will require fluidisation of fill material prior to pumping and will require a ready source of water as

well as power. This could also be achieved through wet dredging of sand and pumping to the Artificial

Channel site. Salty Creek is the closest source of water and is preferred as the salinity levels at the mouth

of the Creek would be best matched to the receiving area for drainage of the transferred sand. In general

it would be preferable to utilise fresh water for slurry pumping which is most likely to be available at times

of outgoing tide or following entrance breakout. The slurry pump would require a portable power system

at the extraction location.

4.7 Water Exchange

Manipulation of water levels and water exchange between Salty Lagoon and Salty Creek may be required

in times of poor lagoon water quality where monitoring of the system and the associated adaptive

management protocol indicates that water exchange would be beneficial.

Options with fixed mechanical components (e.g. a permanent valving and pipes) are likely to require

ongoing maintenance and would be subject to corrosion, fouling and blockage. Permanent structures may

also be vulnerable to vandalism and would therefore also require protective measures. Permanently

installed options are likely to be more expensive than temporary/ mobile equipment due to these design

and maintenance requirements.

Permanently installed facilities to allow water transfer would consist either of slot arrangement (with stop

boards) or a valve and pipe system and would need to be designed to cater for the full range of lagoon

water level. Both these approaches would need to be fully integrated with the hydrological cut off barrier

to ensure that bypassing of the slot or valve did not occur.



A stop board slot would most likely consist of a concrete lined channel aligned longitudinally within the

Artificial Channel closure and therefore would be most cost effec tive if only part of the Artificial Channel

was filled. The slot itself would be up to 2m deep and at least 0.6m in width (to allow maintenance access

and reduce the risk of the slot as a wildlife trap). The length of the slot would be dictated by the prop ortion

of the Artificial Channel to be filled. Apart from a potential hazard to wildlife, this channel would also pose

a safety hazard to people and would therefore need to be covered (e.g. walkway grid -mesh) or access to

the site prevented. Management of the stop boards, particularly if sub-surface water extraction was

required, or if variable rates of discharge were to be achieved, would require a system to interchange

various configurations of boards at different levels without compromising personnel safety. The stop

boards at different levels would need to be able to be raised and replaced without entirely draining Salty

Lagoon and therefore would probably require mechanical assistance to overcome water pressure. A

system such as this would be vulnerable to vandalism and would need to be appropriately protected.

A valve and pipe arrangement would need to consist of a variable depth intake (or multiple valves). This

system would be most appropriate for concrete or sheet pile closure where the valves could be mounted

on the structure. The pipes would discharge to an area either immediately downstream of the closure or

some distance downstream. The discharge location would need to be protected from erosion due to water

velocities exiting the pipe(s). Valve maintenance against corrosion and clearance of blockages would

need to be regularly undertaken to ensure the valve(s) remained operationa l. Once again, vandalism

would be a concern and appropriate measures would need to be taken.

Temporary measures to achieve water exchange are considered less problematic as it is anticipated that

the need for water exchange will be short-term and sporadic. This would take the form of either

temporarily deployed pumps or siphons transported to site by small boat and set up a s the circumstance

dictated. A temporary siphon arrangement has the advantage of not requiring continuous fuel or power

(aside from initial pump priming of the siphon) and is easily scalable (i.e. multiple siphons) to achieve

increased discharge rates if required. Once the appropriate level of water exchange had been achieved,

all equipment would be taken off site, refurbished and stored for further use.

A temporary set up has several distinct advantages, including:

Less installed infrastructure, less corrosion and field maintenance costs

Higher degree of reliability

Less aesthetic impact

Less exposure to vandalism and inadvertent draining

Less public safety risk

For this reasons a portable, temporarily deployable system that would allow water exchange when

required is favoured as described in the following section.



5. PREFERRED ARTIFICIAL CHANNEL CLOSURE CONCEPT

Based on the discussion in Section 4 a preferred concept has been developed for consultation with

DECCW (PWS & EPA) and I&I NSW. It is acknowledged that further design is required to confirm key

aspects such as structural stability and that other options not presented here may also be viable and

should be considered as appropriate.

Although an exhaustive analysis of Artificial Channel closure options was not undertaken it is considered

that the concepts discussed in this report provide a sufficient evaluation of the potential techniques,

construction requirements and hence scope of environmental risk associated with each of the options.

5.1 Preferred Concept

The preferred option is to fill the entire length of the Artificial Channel with sand derived from Airforce

Beach at the entrance to Salty Creek (Site C in Figure 5) and pumped as a slurry to the fill location.

Prior to construction of the channel closure, the water level in the lagoon must be low to ensure that salt

water fish species are not trapped in the closed lagoon. In addition, low water levels allow more efficient

erosion controls. If the lagoon is not already drained, it may be necessary to artificially open Salty Creek

to the ocean to allow draining to coincide with planned construction times. This may be achieved by

digging a small channel between Salty Creek and the ocean. This is considered a low environmental risk

operation as long as water quality conditions within Salty Lagoon are favourable at the time. A site

assessment would need to be undertaken at the time to evaluate any environmental risk at the

commencement of works.

Transport of the sand would be achieved using a shallow water dredge at the mouth of Salty Creek. An

example dredge is shown in Appendix 1. The dredge would be operated within a defined excavation area

at the mouth of Salty Creek until the required amount of fill has been transferred to the Artificial Channel

site. The dredge can be temporarily relocated further up Salty Creek if required to reduce risks associated

with high seas.

The sand slurry will be pumped via temporary pipe laid along the bed of Salty Creek. Pipe segments

would be laid by hand with the aid of a floating shallow draft barge or boat and would remain in place for

the duration of the pumping phase of the project. The diameter of this pipeline would need to be selected

such that the clogging and pump head loss was not prohibitive, but that pipe segments were deployable

without heavy machinery.

The fill material would be transferred as pumped slurry directly to the Artificial Channel area. At the

Artificial Channel, biodegradable sand bags (if required) would be filled with the slurry and placed towards

each end of the closure to create a central bunded area within the channel. The slurry would be pumped

into the area between the bund walls and allowed to settle. The water from the slurry would drain towards

Salty Creek and could be prevented from draining to Salty Lagoon by a layer of impe rmeable (but

biodegradable) geotextile that would be installed in association with the southern wall of sand bags. This

impermeable layer will remain buried within the channel fill and will gradually break down and be replaced

by natural clogging of the sediments. This will allow natural groundwater exchange through this section of

the land bridge to be re-established over time. Placed fill material will naturally settle as the Artificial

Channel is filled and water drains from the slurry. A double set of temporary geotextile silt curtains will be



installed outside of the bunded area to ensure that any turbidity plume is contained within the immediate

work area.

Drained sand within the bunds will be landscaped to fit the natural contours of the site allowing for further

settlement. Sand would be pushed outside of the bunded area to form the ‘beaches’ at either end of the

Artificial Channel closure. Sufficient fill will be transferred to these areas to account for natural erosion

and redistribution of sediment at these locations. The sand bag bunds (if used) will be set back far

enough within the length of the Artificial Channel such that there is no risk of these being uncovered with

any such erosion. The final fill elevation at the southern end of the closure (i.e. cross-section A in Figure

6) is to exceed 2.1m AHD thereby ensuring that any overflow from Salty Lagoon to Salty Creek is via the

natural overflow to the west and not over the new fill area where erosion issues could result.

It is envisaged that one person will be required to ensure correct placement of the fill at the Artificial

Channel site and will be in contact with the dredge operator via two-way radio.

Once site works are complete, the entire Artificial Channel closure site would be revegetated with low -

lying vegetation (easy to remove if the channel closure is to be reversed) to suit the surrounding area.

Long-term establishment of Melaleucas and other larger species is likely to occur naturally or could be

planted as desired. The rehabilitated site will be entirely natural in appearance and all buried construction

materials (e.g. sand bags and impermeable barrier) will be biodegradable.

Operational water exchange between Salty Lagoon and Salty Creek would be achieved through the

temporary deployment of a mobile siphon arrangement when/if needed. The sizing and number of siphon

units is yet to be determined however the strategy is readily scalable. The siphon intake would consist of

a small floating platform that is temporarily anchored in place at the head of the filled Artificial Channel.

The design of the siphon intake would be such that the depth in the water column from which water is

drawn can be varied and the maximum depth of Lagoon drawdown pre-determined. Temporary pipe(s)

would connect the intake to a priming valve and then overland to and exit point in Salty Creek. The siphon

would consist of backflow prevention valves and would be primed using a small portable water pump. It is

envisaged that a siphon kit could be transported to site and deployed rapidly (within a day) using a small

boat accessing the site via Salty Creek. All equipment would be removed at the end of a transfer

operation, and housed at Council facilities in Evans Head thereby ensuring equipment remains free from

corrosion, clogging and vandalism.

Drawings showing the closure concept in plan view and cross -sections are shown in Figure 6 and Figure

7and Figure 8. Further details on the preferred concept are provided in the following sections. The need

for structural and hydrological barriers will be determined during the final design stage (refer Section 6).



Figure 6: Plan View

Figure 7: Cross-Section A-A showing hydrological/structural barrier and vegetation

A A

Biodegradablesand bag barrier

Sand fill

Revegetate to matchsurrounding native vegetation

Existing tree to be retained

WE

Existing bed profile



Figure 8: Cross-Section B-B showing filled Artificial Channel initial profile and settled final profile.

5.2 Site Configuration During Construction

The access route and work areas are shown in Figure 9.

B B

WE

Existing bed profile

Sand fill

Initial fill profile

Final fill profile



Figure 9: Site Configuration



5.3 Fill Materials and Source

The quantity of beach sand required is shown in Table 2.

Table 2: Fill quantity required

Purpose Quantity Comments

Fill 2,900 m3 The Artificial Channel is approximately trapezoidal in shape

averaging 110m long, 15m wide and 2m deep

Excavation depth 0.5 m Assumed average

Excavation area 5,800 m2 e.g. 100m x 58 m (approximate only)

5.4 Equipment and Materials Requirements

The major equipment and material requirements are listed in Table 3.

Table 3: Equipment Requirements

Purpose Equipment/Materials

Site establishment Fencing, signage, erosion/sedimentation protection

Hydrological/structural barrier If required, filled natural fabric biodegradable sand bags (refer Table 2)

Excavation of beach sand Refer Table 2. Shallow water dredge.

Transfer of sand to Artificial Channel

site

Slurry pump and hose (at least 600m).

Stabilisation/ revegetation of Artificial

Channel surface

Digging equipment, erosion control matting, plant stock

Water transfer infrastructure Concrete and reinforcing for sump construction for placement of siphon

5.5 Infrastructure Siting and Construction Timing

The main considerations for timing of the works and siting of infrastructure are:

Lagoon water level – for safety and practicality reasons, the construction work must be

undertaken at low lagoon water level and be completed prior to refilling of the lagoon (which will

occur with prolonged heavy rainfall). If the lagoon is not already drained, it may be necessary to

artificially open the creek to the ocean to allow draining to coincide with planned construction

times. This may be achieved by digging a small channel between Salty Creek and the ocean. The

time taken to drain the lagoon will depend on lagoon water level (and hence hydraulic gradient to

the beach) and tides at the time but is likely to be approximately 1 - 7 days;

Tides – access to the work sites along the beach can only be undertaken at lower tides. Similarly,

infrastructure must be located above the maximum high tide (indicated on Figure 6) with



allowance for storms. Timing of the work and siting of infrastructure must be flexible enough to

deal with high sea levels;

Nesting season for migratory birds (generally August to January each year) – Construction

activities must be undertaken outside of the nesting season. Any site disturbance (such as work

compounds or excavation areas) must also be rehabilitated prior to the commencement of the

nesting season;

High rainfall events generally occur in the summer months, particularly January and February but

can also occur at other times of the year. Average rainfall is generally highest between February

and June, with March generally experiencing the highest rainfall; and

Public amenity and safety – the beach and creek entrance are frequently used by the public for

recreational activities at all times of the year but more frequently in summer holidays (December

to January). All work areas must be fenced with appropriate signage to exclude public access.

Public vehicular access along the beach, past the creek entrance must be maintained at all times.

5.6 Work Sequence and Duration

Based on the above, the construction works can be undertaken between April and July (inclusive). The

months of May and June are expected to experience the lowest average rainfall and a lower probability of

high rainfall events. An indicative work program is given in Table 4. Tides must be considered in all

activities.

Table 4: Indicative Construction Program

Activity Approximate

Duration

Timing Month

Lagoon draining (if required) 1-2 days Week 1 May

Site establishment, fencing, sediment/silt controls at beach and

Artificial Channel sites (refer Figure 6), establish/repair walking track

through dune

3 days Week 1 May

Establish dredge equipment at creek entrance 1 day Week 2 May

Establish hydrological/structural barriers (if required) 3 days Week 2 May

Dredge sand and pump to Artificial Channel site 2 weeks Week 3-4 May/June

Decommission dredge and transport off-site 1 day Week 5 June

Construct water transfer infrastructure 1 day Week 5 June

Create finished ground level, remove weeds, apply erosion controls

and rehabilitate Artificial Channel and beach sites.

2 days Week 5 June

5.7 Vegetation Clearing and Site Disturbance

It is envisaged that some areas of salt marsh at the Artificial Channel will be disturbed during the

construction work. These areas are indicated on Figure 6 (approximately 250 m2). The proposed site for

sand extraction is clear of vegetation due to wind, tide and wave impacts. Dune areas surrounding the



work sites will be fenced as no go zones. Workers are expected to access the Artificial Channel site by

boat or by walking along the existing walking track which may require minor removal of tree branches to

improve access.

Some areas of Salty Creek may experience minor bed disturbance as a result of transport of equipment

and materials to the Artificial Channel site (e.g. by boat, barge or placement of the slurry pumping hose).

5.8 Site Rehabili tation

Rehabilitation activities will consist of:

Removal of all equipment, waste and work compounds. Sediment controls may be required to

remain in place until vegetation is established;

Establishment of vegetation on filled Artificial Channel surface and revegetation of disturbed

areas; and

Recontouring of beach areas disturbed through work compounds or excavation.

5.9 Finished Site

It is expected that the rehabilitated Artificial Channel would mimic the surrounding area between the

Lagoon and Creek. The finished surface of the Artificial Channel infill would be equal to or marginally

above the surrounding land elevation, such that high water overflow from the Lagoon would occur via the

natural connection between salty Lagoon and Salty Creek. In this way, overtopping of the Artificial

Channel would be avoided. An artist’s impression of the closed Artificial Channel is shown in Figure 10.

Figure 10: Artist’s Impression



The profile of the banks of the Lagoon and Creek would mimic the existing banks and form a natural

extension of the lagoon/creek bed. The anticipated surface water drainage pathways are shown in Figure

11 including the natural overflow pathway between Salty Lagoon and Salty Creek.

Figure 11: Anticipated surface water drainage pathways of closed Artificial Channel

5.10 Reversibility

If required, reversal of the Artificial Channel closure would be achieved by excavation of some or all the

sand. Construction activities would be similar to those for the Artificial Channel closure and would consist

of:

Slow dewatering of lagoon (e.g. using siphon equipment);

Establishment of work compounds and exclusion fencing;

Barge to transport digging equipment to the Artificial Channel;

Excavation of sand from the Artificial Channel and placement of sand at low points in the lagoon

and creek or pumping of sand slurry back to the beach; and

Rehabilitation of the work sites and disturbed areas.



5.11 Environmental Management

An environmental management plan would be prepared for the construction of the Artificial Channel

closure. The adaptive management protocol to be prepared for the trial phase of the Artificial Channel

closure would include all environmental operational requirements. The key environmental management

requirements for the design and construction of the Artificial Channel closure are listed in Table 5.

Table 5: Environmental Management

Objective Recommendations

Protection of

Vegetation

Fence off sensitive areas and establish no-go zones;

Minimise removal or damage of existing vegetation;

Weed species within construction areas to be identified by suitably qualified botanist and

removed and disposed in licenced landfill;

Establish designated access routes for minimal vegetation disturbance;

All vehicles/plant to be clean and inspected for weeds and seeds before authorised on site;

Any imported fill inspected for weeds and seeds;

Any large vegetation removed should be mulched on site and used in site rehabilitation;

Rehabilitate all disturbed areas and revegetation of construction area with local endemic

species; and

Monitoring of revegetation areas following planting and maintenance where necessary.

Protection of

Wildlife

Conduct fish monitoring prior to works to confirm risk and if required, conduct fish netting in

Salty Lagoon immediately prior to initial closure and transport estuarine species to Salty Creek;

Restrict working hours to day time only;

Timing of construction works to occur outside breeding season (nesting season generally

occurs from August – January);

Timing of construction works outside of fish migration periods (e.g. June/ July) or to coincide

with low water levels and preferably immediately after a draining event;

If entrance opening occurs leading up to construction works (within month of work), close off

Artificial Channel with sand bags to prevent fish passage into lagoon (or consider artificial re-

opening); and

Contact NPWS personnel if sick, injured or orphaned wildlife are found.

Sediment and

Erosion Control

Timing of construction works to coincide with low rainfall periods as much as possible;

Maintain existing vegetative cover to greatest extent possible;

Sediment and erosion controls to be designed and implemented according to appropriate

engineering guidelines (bunding, soil stabilising matting, etc.);

All sediment controls to be inspected regularly and after any high rainfall events ;

Monitor water quality including turbidity; and

Corrective action to be undertaken swiftly if water quality issues detected (e.g. additional

bunding, cease pumping, reconfigure controls, etc.).



Objective Recommendations

Stormwater

Control

Sediment and erosion control as above;

No refuelling to be conducted on site or if unavoidable, refuelling to be conducted within

bunded areas;

Spill kits to be available at all times in case of any spills;

Hazardous materials, fuels or chemicals to be stored in appropriately bunded areas; and

All vehicles/plant to be regularly maintained and inspected for leaks .

Reduction of

Noise and

Vibration

Restrict working hours to day time only and avoid long periods of high noise activity;

Minimise heavy vehicle movements;

Selection of minimal noise/vibration machinery; and

Minimise total work time wherever possible.

Protection of Air

Quality

Limit removal of vegetation and topsoil wherever possible;

Dust producing activities should be avoided or minimised wherever practical; and

Watering of works to be undertaken if required for dust suppression.

Waste

Management

Recycling and reuse to be undertaken where practical;

Provide suitable bins for waste and storage; and

Monitor site and clean up daily as required.

Fire

Management

If smoking is permitted on site, ensure all butts are fully extinguished and disposed of in bins

provided;

All machinery to be maintained and serviced regularly; and

Fire fighting equipment to be available at all times.



6. NEXT STEPS

The following actions are required prior to the closure of the Artificial Channel:

Liaison with regulatory authorities, particularly DECCW (PWS & EPA) and I&I NSW to obtain

approval requirements for the project;

Environmental impact assessment in accordance with the Environmental Planning and

Assessment Act, 1974;

Final design of the closure; and

Selection of a preferred construction contractor.



7. REFERENCES

Hydrosphere Consulting (2009). Salty Lagoon Rehabilitation Plan Part B: Options Assessment. Report

prepared for Richmond Valley Council

Hydrosphere Consulting (2010). Salty Lagoon Ecosystem Recovery Monitoring Program. Final Report

prepared for Richmond Valley Council

DECCW (2010) Broadwater National Park Draft Plan of Management



Appendix 1: Example Dredge (Sykes Pelican Dredge)

Version 1 17th January 2005

Pelican Dredge The innovative, maneuverable and robust Pelican Dredge is designed and manufactured by Sykes Group and is a breakthrough in shallow water dredging. Designed for one-man operation in water less than one metre deep, the Sykes Pelican dredge, in standard trim will excavate material down to a depth of 4.5 metres. If required greater excavation depths can be achieved. The Pelican dredge can be put to work in a variety of applications: • Clearing out settlement and tailings ponds in mine sites • Recovering river sands and gravels • Clearing silt from industrial and municipal waste ponds • Clearing weeds and similar growth from waterways and marinas The dredge is self-contained and self-propelled. Powered by a high torque Cummins diesel engine* the rear-

mounted outboard hydraulic drive complete with a low speed/high thrust propeller ensures optimum maneuverability. The Pelican Dredge is easily transported and can operate in areas inaccessible to conventional suction dredges. The 2.4 metre wide, horizontal-shaft, rotating cutting head is fitted with hardened steel cutting blades and auger fighting which ensures the dredge’s suitability for a range of applications. Depending on the operating environment sand cutting spikes, tiller tines or a pond liner protection cage are available as options.

Cutting depth is controlled by the operator. The hydraulically operated dredge arm includes a 150mm submersible dredge pump capable of handling viscous and particulate slurry transporting up to 60mm solids. Discharge is pumped ashore through a floating pipeline.

Technical Specifications Model Pelican Length (Overall) 7.4M (nominal) Length (Pontoons) 5.5M Width 2.4M Height 2.8M (nominal) Weight 5.5 Tonnes Draft 600mm Fuel Capacity 500L Fuel Consumption 20 litres/hour Power Cummins High-Torque Diesel* Engine Kilowatts 71KW Continuous Propulsion Outboard Hydraulic Drive Steering Cable Controlled Propeller Low Speed/High Thrust Pump 100mm Dredge Type Pump Speed 1000rpm to 1900rpm Impeller Screw Centrifugal Pump Seal Tungsten-Carbide Mechanical Pump Solids 60mm Passing Cutterhead Width 2.4M Cutterhead Torque 565 NM 95000 in/lbs) Cutterhead Rotation Birotational Cutting Teeth Hardened Steel Excavation Depth to 4.5 M Nominal Excavation Width to 2.4 M Excavation Speed to 3 M per minute Discharge Pipe 150m dia floating complete with flexible 2 M joints and bauer couplings Pontoons Foam-filled steel Deck Finish Non-skid surfacing Colour Red-Orange/Grey/White Control Cab Front-mounted, air conditioned Electrical Power 12 V DC Lighting Cab Light (optional), Front Work Lights (optional) Instrumentation Tachometer, Hour Meter, Water Temperature, Oil Pressure, Hydraulic

Pressure, Ammeter, Flow Meter (optional) Controls Steering Wheel, Engine Throttle, Key Start, Depth Control, Pump

Speed Control, Cutterhead Forward/Neutral/Reverse * Optional engines available Specifications subject to change without notice

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