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In the matter of the Resource Management Act 1991 And In the matter of an application for Resource Consents by Oceania Dairy Limited

to construct and operate a pipeline to discharge treated wastewater into the ocean.

Duncan Cotterill Solicitor acting: Ewan Chapman PO Box 5, Christchurch Phone +64 3 379 2430 Fax +64 3 379 7097 ewan.chapman@duncancotterill.com

STATEMENT OF EVIDENCE OF SUMAN KHAREEDI FOR OCEANIA DAIRY LIMITED

28/05/ 2020

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INTRODUCTION

1 My full name is Suman Kumar Sachidananda Murthy Khareedi.

2 I hold a Master in Business Administration from the University of Auckland, and a

Bachelor in Engineering (Civil) from Bangalore University, India. I am a member of the

following professional bodies or industry groups:

Engineers Australia (MIEAust)/Professional Engineer registered as a Chartered

Professional Engineer (CPEng) in the National Engineering Register of

Australia;

A Chartered Member of Engineering New Zealand (CMEngNZ) as a Chartered

Professional Engineer (CPEng);

I am also registered as an International Professional Engineer (NZ)/APEC

Engineers Register

3 I, as the Infrastructure Business Manager, lead the Infrastructure Engineering team at

Babbage Consultants Limited (Babbage) since July 2018.

4 I have 28 years of experience in a variety of major projects in the waters sector,

roading, land development, industrial and other civil engineering projects in New

Zealand, Australia, and India. My professional experience includes the design of

large pipelines, the design of water and wastewater treatment, and stormwater

management systems.

CODE OF CONDUCT

5 While this is a Council Hearing, I acknowledge that I have read and am familiar with

the Code of Conduct for Expert Witnesses contained in the Environment Court

Practice Note 2014, and agree to comply with it. I confirm that this evidence is within

my area of expertise, except where I state that this evidence is given in reliance on

another person’s evidence. I have considered all material facts that are known to me

that might alter or detract from the opinions I express in this evidence.

Scope of evidence

6 I have been asked by Oceania Dairy Limited (ODL) to prepare evidence which covers

the following matters:

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I. A detailed description of the proposed wastewater pipeline and outfall

including its size, alignment, and components;

II. An outline of the detailed design to be completed;

III. A conservative outline of the methodology for the construction of the onshore,

coastal and offshore sections (in the CMA);

IV. Its effects, description of alternatives considered, and route options explored;

V. Dewatering groundwater for placement of the pipe and its potential effects;

VI. Operation and management of the outfall, including monitoring and in-built

redundancies and safety measures; and

VII. Maintenance of the outfall infrastructure in the marine environment.

7 ODL has applied for resource consents to install a wastewater pipeline and ocean

outfall from the ODL processing plant at the corner of Cooneys Road and State

Highway 1. The pipeline will extend from the factory to the ocean approximately 500m

offshore from the current coastline (the proposal).

EXECUTIVE SUMMARY

8 My key observations and conclusions are:

ODL intends to procure the construction of the proposal through a ‘Design and

Build’ contract. Our specimen design will be used to draft the procurement

documents outlining the confines within which the detailed design and

construction of the pipeline will need to be completed. The company offering

the design and build services will develop the specimen design discussed in my

evidence to detailed design before construction. My evidence covers a

conservative outline (i.e. a “worst case scenario”) of the pipeline design and

construction based on our specimen design.

I have discussed this pipeline and its construction in three sections:

I. the onshore section;

II. the coastal section; and

III. the offshore section.

The onshore section is 7km long, the coastal section is approximately 270m

long and the offshore section is 500m long with three 50-150m diffusers

extending out at the end of a 350m long outfall pipe. This is shown in figures 1

and 2 below:

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Figure 1: Proposed alignment of the pipeline

Figure 2: Coastal and off-shore sections of the pipeline with diffuser arms

I anticipate that most of the onshore section will be constructed using the

conventional trenching method. Microtunnelling will be used to cross the

irrigation channels, Morven Glenavy Road and the South Island Main Trunk

Railway. Microtunnelling could be used for the entire length of the onshore

section, and I have included that possibility in this evidence. This will be a

decision for the company undertaking the works to determine.

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Microtunnelling will also be used to construct the coastal section. In sections

where microtunnelling is used, the wastewater pipeline will be housed in either

a 600mm or 1,000mm casing pipe.

The offshore section will most likely be constructed using the dredging method

to excavate a trench in the seabed. The ends will be sealed without filling the

pipe with water, floated out to the sea with the help of tugboats, and sunk to the

seabed. Once the offshore section is placed in the excavated trench, it will be

backfilled using a backhoe dredger or similar. While there are other possible

methods (microtunnelling or self-sinking pipeline), the dredging method is likely

to be used. The dredging method also generates more effects than the other

two, and so my assessment of the dredging method is a “worst case”.

Construction of the coastal and offshore sections will require enabling works by

way of a construction access track. This includes temporary access from the

end of Archibald Road to the beach that will be formed by clearing vegetation

along an existing track and filling its eroded section in the lower reaches of the

gully.

We have estimated the overall duration of construction to be in the order of 8 to

10 months. This is assuming that the onshore, coastal, and offshore sections

will be constructed in sequential order, and trenching/dredging is the

predominant method of construction. This comprises of:

Up to 5 months to complete the onshore section.

Up to 3 months to complete the coastal section, and

Up to 2 months to complete the offshore section

In addition to the above construction durations, the establishment on-site and

the enabling works required are expected to take approximately 4 months.

Therefore, I estimate the total duration of construction to be 14 months.

The construction of the proposed pipeline will have some temporary impact on

the environment because of the land disturbance activities and marine work.

Such an impact can be mitigated satisfactorily through standard construction

management. Conditions requiring a construction management plan are

included with the proposed consent conditions.

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The duckbill valves installed at the end of diffuser arms prevent the backflow of

seawater into the pipeline can get damaged due to the dynamic environment at

the bottom of the sea. Breaking of these valves will not affect the dispersion of

wastewater as the modelling undertaken by my colleague Mr. Lobo Coutinho is

based on having no duckbill valves. Therefore, the inspection of these valves

does not need to be frequent. The onshore and coastal sections will require

standard inspection and maintenance that is typical to most wastewater

pipeline. No specialist maintenance work is required.

EVIDENCE

Description of the proposed wastewater pipeline and outfall

9 The proposed wastewater pipeline and ocean outfall extends from the ODL factory to

the ocean approximately 500m offshore from the current coastline. My team and I

have completed the specimen design to allow an assessment of the effects

constructing this pipeline has on the environment. ODL intends to procure the

construction of this pipeline through a ‘Design and Build’ contract. The nominated

contractor will complete the final design of the pipeline and choose a suitable

construction methodology. My evidence covers a range of possible options for

pipeline design and construction. I have taken a conservative approach, by detailing

the options with higher potential impacts in more detail, so that the Commissioners

can make a decision on the “worst case scenario”.

10 The alignment of the pipeline generally traverses Cooneys Road and Archibald Road.

As it traverses along Archibald Road, it crosses two irrigation channels, the South

Island Main Trunk railway line, and Morven Glenavy Road. The proposed location for

the outfall is at the end of Archibald Road. The wastewater pipeline and outfall will

include a pump station near the existing wastewater treatment plant. The pipeline will

also have scour and air valves along its alignment to allow for effective operation and

maintenance. These valves are typically housed inside valve chambers similar to

manholes.

11 Consents from Waimate District Council and Kiwirail will be required to construct the

pipeline in the chosen alignment. My colleague Ms. Sukhi Singh has obtained an

approval in principle from the Waimate District Council in October 2019. I have

appended a copy of that letter from to my evidence as Appendix A. Likewise, my

colleague Ms. Sukhi Singh and I have had preliminary discussion with Kiwirail about

crossing the South Island Main Trunk railway line to inform them of our proposal.

Constructed of the proposed wastewater pipeline will need formal approval/consents,

when the detailed design is available, from both Waimate District Council bay way of

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a Corridor Access Request (CAR) from Kiwirail by way of and a Deed of Grant and a

Permission to Dig.

12 The size of the proposed wastewater outfall pipeline will be any size between 300mm

and 450mm in diameter. Our specimen design comprises of a 400 mm diameter pipe

that discharges the design flow of 10,000m3/d (116 l/sec) at a flow velocity of 1.4m/s.

We have estimated the pressure drop over this length to be in the order of 4.8m for

the above parameters. If an alternative pipe diameter is chosen, the flow velocity and

the pressure drop over the length of the pipeline will correspondingly vary.

13 To disperse the wastewater flows effectively in the ocean, the diffuser arms at the end

of the pipeline (submarine section) will need be 200 to 250 mm in diameter. The

current flow rate of 1,740m3/day is less than the maximum flow rate of 10,000m3 the

diffusers are designed for. This provides ODL the flexibility of discharging wastewater

for a shorter period in the day.

14 Our specimen design has a constant gradient (positive or negative) of 1 in 250 or

0.4%. This allows the pipeline to be constructed predominantly at depths (Depth to

Invert or DTI) of 1.0 m to 3.0 m with these gradients. This results in a very flat “W”

shape along the length of the pipeline, which can be seen in figure 3 below. This is

typical for pipelines of this nature.

Figure 3: Vertical profile of the pipeline in the shape of a 'W'

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Status of the design

15 To prepare for this application and hearing, a specimen design of the pipeline has

been completed. The work needed to create the specimen design included the

following:

I. Field investigations to allow the selection of a suitable pipeline alignment, and to

identify practicable construction methodologies;

II. Topographical survey of the selected alignment to finalise the vertical alignment of

the pipeline and identify construction challenges;

III. Hydraulic design of the pipeline to determine the necessary size of the pipeline;

IV. The horizontal and vertical alignments of the pipeline, with some flexibility for

refinement by the nominated Contractor based on the chosen construction method;

V. Identification of other components required for efficient operation and maintenance

during the pipeline’s whole of life cycle; and

VI. Shortlisting of the practicable construction methods to allow an assessment of the

potential impact construction activities may have on the environment.

16 The specimen design will assist ODL in procuring the design and build services by

providing a baseline design. In other words, it will be used to draft the procurement

documents outlining the confines within which the detailed design and construction of

the pipeline will need to be completed. The company offering the design and build

services will develop the specimen design discussed in my evidence to detailed

design before construction. The detailed design will include the following:

I. Selection of a suitable construction method that suits the plant and machinery, and

the technical skills available within the company undertaking the construction;

II. Refinement of the horizontal and vertical alignment of the pipeline to suit the

chosen method of construction;

III. Detailed site investigations to inform the design of temporary structures and

supports;

IV. Rationalisation of the pipeline components to suit the chosen alignment and

construction method;

V. Structural design of temporary and permanent works. This includes the design of

the trench shoring, tunnel boring machine launch and receiving pits, valve

chambers, surge tank, diffuser heads, anchors for the offshore section of the

pipeline, and the access to the beach for construction; and

VI. Selection of brands and suppliers for various fittings and materials to construct the

pipeline. This includes the brand of the pumps, the pipe, valves, and the diffuser

heads.

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Construction methodology

17 An alignment along existing road corridors and the paper road was chosen for the

proposed alignment for the following reasons:

I. To mitigate the impact of constructing this pipeline on the environment by using an

alignment that has already been modified in the past for other utilities

II. To allow easy access to the pipeline for operation and maintenance even when the

fields are irrigated and without the need for permanent access tracks

III. To have ground conditions that are conducive for the construction of the pipeline

18 The outfall pipe is designed to be a pressure pipeline through which the wastewater is

pumped to the ocean for the following reasons:

a) The ground profile along the majority of the alignment is typically flat to gently

undulating with slopes varying from 0.38% to 0.14%. This makes it impracticable to

have a constantly falling or constantly rising pipeline from the wastewater treatment

plant into the ocean without having deep sections.

b) Large boulder clusters are expected at depths of more than 4 metres. It is extremely

challenging to construct the pipeline through boulder clusters. Therefore, the pipeline

will need to be constructed predominantly at depths (Depth to Invert or DTI) of 1.0 m

to 3.0 m.

19 The three discrete sections – Onshore, Coastal, and Offshore require three distinct

construction methodologies which I have discussed below:

Onshore Section

20 The pipeline from the factory boundary to the end of Archibald Road (the boundary of

the CMA) constitutes the onshore section. This section can be constructed using

either the conventional trenching or trenchless methods as the pipeline will be at

depths between 1.0m and 3.0m. Trenchless methods will be required to cross the

irrigation channels, the South Island Main Trunk railway line, and Morven Glenavy

Road.

Conventional trenching

21 Conventional trenching will be the most likely method adopted for the majority of the

onshore section. Trenches for pipe laying will be constructed using a 20-tonne

excavator or similar. It is anticipated that approximately 20m of trenching can be

achieved each day. The major limitation on length is the amount of time it takes to

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clear the excavated material. Therefore, a longer length of the trench could be

excavated in a day if a suitable site for disposing of excess cut material is available

close to the pipeline alignment. In either case, trenches will be progressively

excavated and backfilled in lengths less than 50m. Plastic pipes are generally in

lengths of 12 to 18 metres. Therefore, a 20m length of the trench is expected to be

open for pipelaying and backfilling at any time of a working day.

22 Trenches that are 1.0m to 3.0m deep are typically 1.5m wide. Therefore, a 10m wide

corridor will be fenced off as a construction area. This construction area will move

progressively with trenching. Polyethylene pipes will be welded progressively to

install in the excavated trenches. Pipes will be welded next to the trenches within the

fenced area.

Figure 4: Trenching for pipelaying (picture source: 95revive.com)

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Excavated material that is not required for backfilling will be carted away for disposal

regularly. It is estimated that a total volume of 30,000m3 of excavated material will be

disposed of during the construction of the pipeline.

23 The pipes will need to be bedded in engineered backfill (select aggregate). This will

need to be imported to the site from a suitable quarry. An estimated 1.0m3 of

compacted engineered backfill will be required per metre of pipe laid (20m3 per day

or 3 truckloads). This equates to an estimated 15 truck movements per day (return

trips) to and from the construction site to cart away excavated material and to bring in

engineered fill.

24 The vertical alignment of the pipeline is in a “‘W’ fold format (as explained above in

paragraph 13 and shown in Figure 3) as it is not practicable to construct it with a

constant gradient from the factory to the ocean. Scour and air valves will need to be

constructed at every sag and crest. These valves will be housed in valve chambers

that are similar to manholes. These valve chambers will be constructed progressively

with the trench. Finishing of these chambers from inside will be completed after the

valves are installed.

25 Any groundwater and/or rainwater contained in trenches and pits will be dewatered

using wellpointing or open sump pumping as in figures 6 and 7. The wellpointing

method of dewatering consists of a series of small-diameter wells (wellpoints)

connected by a header pipe that is connected to a pump. The pump draws out water

from the wellpoints via the header pipe. For pipeline trenches, wellpoints are typically

installed in lines on either side of the trench. The pump will be operated using a diesel

generator. The sump pumping method of dewatering comprises excavating a small

sump at the downstream of the trench excavated to lay the pipe. Groundwater that

drains to this sump is pumped out using a pump. In both instances any sediment-

laden water will be discharged to a settling tank for primary treatment (settlement)

before being discharged. The discharge will be undertaken well clear of any irrigation

lines or other surface water bodies and will be controlled or dispersed to avoid any

scour. The sediments deposited at the bottom of the settling tank will be disposed off

site with surplus excavated material.

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Figure 5: Wellpointing method of dewatering

Figure 6: Sump Pumping method of dewatering (picture source: Tang Y., Zhou J., Yang P., Yan J., Zhou N. (2017) Construction Drainage. In Groundwater Engineering. Springer Natural Hazards. Springer, Singapore)

26 Trenches will be temporarily reinstated immediately after backfilling. This is typically

done in sealed roads using cold mix bitumen. The permanent reinstatement of the

road will likely be done progressively in 200m to 500m sections.

27 The section of the pipeline from the factory site in Cooneys Road to Morven Glenavy

Road will be constructed with suitable traffic management. A lane closure will likely

be required to construct the pipeline.

28 If microtunnelling is used for construction, the wastewater pipeline will be encased in

a larger (600mm or 1000mm diameter) pipe.

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Trenchless Construction

29 The onshore section of the proposed wastewater pipeline could also be constructed

using microtunnelling. This would be a decision for the company undertaking the

works, as it is significantly more expensive. As outlined above, microtunnelling will be

required in parts of the onshore pipeline (under irrigation channels, and

roads/railroads). The prevailing geology of the site makes other methods such as

Horizontal Directional Drilling impracticable. Visible disturbance from microtunnelling

within the onshore section would generally be limited to occasional pits for the

following:

1. Drive/launching shaft to launch the micro-tunnel boring machine (MTBM)

and/or to jack the pipes behind the MTBM at the start of the pipeline which

is expected to be in Archibald Road outside the plant,

2. Receiving/recovery pit to recover the MTBM at approximately 7,000m

chainage,

3. Launching shafts at acute bends in the pipe alignment (at the intersection

of Cooneys Road and Archibald Road, and the bend in Archibald Road),

4. Valve chambers to install air release and scour valves along the length of

the pipeline, and

5. Rescue pits to recover the MTBM if an obstruction is encountered.

30 Trenchless methods will require that the pipe be deeper underground, to mitigate the

risk of hydraulic fractures (frac-outs) or ground heaving, which causes visible issues

to the ground surface in addition to posing health and safety risks. If the nominated

contractor uses trenchless methods, I envisage the pipe will be constructed at depths

between 1.5 m and 3.0 m.

31 The construction area for trenchless construction will comprise land for the topside

facilities including a control unit, lubrication unit, muck handling, cleaning storage and

disposal, pipe storing and handing area, and a power supply unit. Generally, this

takes up an area of around 15m wide x 30m long. If the MTBM is a slurry system, the

topside facility will include a slurry separation plant instead of the muck handling area.

The slurry plant allows cleaning of cuttings from slurry for reuse in the tunnel via a

slurry injection equipment (pumps). The topside facility will be located next to the

jacking pit. Depending on the type of equipment used by the nominated contractor,

establishing a topside facility may require the full closure of a section of Cooneys

Road requiring suitable traffic management to divert traffic via other roads for the

duration of construction.

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Figure 7: Typical set up for microtunnelling (picture source: ScienceDirect.com)

32 If microtunnelling is used, the wastewater pipeline will need to be installed in a casing

pipe that is 600mm to 1000mm in diameter. This will result in 0.8m3 of cuttings per

metre tunnelled that need to be disposed of. Ten to twelve truck movements per day

will be required to cart away cuttings/excavated material. This will be in addition to

the traffic volumes required to transport other construction materials viz., pipes, slurry,

hardware, and personnel.

33 Once the pipeline is laid the pits will be finished from inside to form valve chambers or

access manholes. The surface will be reinstated to its pre-construction condition,

which will include asphalting or bitumen sealing in sealed roads.

34 Notwithstanding the method used to construct the remainder of the onshore section,

microtunnelling will be used to cross the irrigation canals, the Morven Glenavy Road,

and the railway line. If microtunnelling is used only for the above crossings, each of

these crossings will need to be tunnelled separately with a drive shaft and a receiving

shaft on either side of the crossings. The topside facilities will move from one

crossing to the other as the work progresses along the alignment.

Coastal Section

35 The coastal section of the site comprises a large gully that extends approximately

90m east to the gravel beach. Cliffs of approximately 10m high are present either side

of the mouth of the gully where it meets the 30m wide gravel beach. All work within

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the coastal section will be undertaken via microtunnelling. Conventional trenching is

not practicable in this section because the vertical profile of the pipeline will need to

be below the seabed level in this section.

Figure 8: Cross-section of the coastal section

36 A drive/launch pit will be required for the MTBM at the top of the gully. The topside

facilities for the microtunnelling activity will be established next to this shaft. The

description of microtunnelling activity in the coastal section is the same as the

description given earlier for the onshore section. The welding of the pipeline will take

place in the paper road section of Archibald Road.

37 Once the pipeline is in place, an inspection chamber will be built at the site of the

drive/launch shaft. Other operational components of the pipeline such as an isolation

valve, sampling port will also be constructed here in conjunction with the inspection

chamber. This structure will be similar to a manhole (substantially smaller than the

drive/launch shaft). The remainder of the drive/launch shaft will be backfilled and

reinstated to its pre-construction condition.

38 Traffic management around the shaft site will not be necessary as traffic access along

Archibald Road does not currently extend up to it.

Constructing a temporary access track

39 A temporary access track from the end of the Archibald Road to the beach will be

required to construct the remainder of the offshore section. This is to allow the

transport of the pipeline to the beach and to monitor the installation of the pipeline

under the sea bed. This access track will be constructed down the existing gully at

the end of Archibald Road.

40 The existing gully is not recorded as a natural feature (in local or regional maps and

plans) and seems to have been caused (or at least exacerbated) by the discharge

from an irrigation exhaust channel. It is also likely that the gully was used to access

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the beach from the paddocks above the cliff, as it seems to have a man-made, now

overgrown, wide path on the southern side connecting the top of the cliff to the beach

with a width and slope appropriate for a vehicle. Therefore, creating an access path

will comprise of clearing vegetation and placing fill to reform the eroded section in the

lower reaches of the gully.

41 Reforming of the track as above it will not increase the risk of erosion or aggravate

ongoing erosion. The existing gully is substantially wider than the irrigation channel

discharging it. Only a small section of the gully will be adequate to convey the

expected flows. Notwithstanding that, the section of the gully conveying water can be

lining with Reno Matters or similar armour to mitigate the risk of erosion. Other

options possible include constructing a ‘culvert’ with drainage arches, pipes, or

drainage cells or to line the edge of the track with gabion baskets. Even though the

appointed contractor will make the final choice of the methodology, I consider that the

risk of gully erosion is low and any such risk can be effectively mitigated using one of

the numbers of options outlined above.

Offshore Section

42 The offshore section of the pipeline comprises a straight section of up to 350m and

three diffusers placed 50m apart and extending a further 50m-150m. The

construction of the offshore section will comprise of the extraction of the MTBM, and

then laying the pipeline either by dredging the seabed or by using self-sinking

anchors. The extent of dredging required will be determined by the length of the

microtunnelling completed.

Extraction of the microtunnel bore machine

43 The microtunnelling operation should terminate 100m offshore within an approximate

sea depth of 8m and up to 1.5m below the seabed level. The entire extent of the

300m ‘straight’ section of pipe may be completed via microtunnel, however, this is not

preferred, due to the difficulty of recovering the MTBM machinery.

44 The MTBM will be extracted using a ‘wet recovery’ technique. Wet recovery is

completed entirely from offshore via a barge-mounted dredger. The MTBM will be

exposed via dredging an area of no more than 30m2. The excavation would create a

temporary sediment plume but given the coarse material that will be present it is

anticipated that the material will settle relatively quickly. Once the MTBM is exposed it

will be recovered using divers and barge-mounted crane. If the MTBM is extracted

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further out, the conditions become progressively more difficult for divers to attach the

cables.

Figure 9: Wet recovery of the MTBM (source of image: The Microtunnelling and Pipe Jacking Compendium by J Thomson, Dr. M Herrenknecht and W Suhm)

Pipeline welding

45 The construction of the straight section will entail welding together individual

polyethylene pipe lengths of 12-18 m into a long string of pipes. The welding of the

pipeline will take place in the paper road section of Archibald Road. The anchor

blocks that secure these pipes to the seabed will be fitted at regular intervals as per

the design. Once the entire 300m of the pipeline is ready, the ends will be sealed

without filling the pipe with water, and floated out to the sea with the help of tugboats.

Cranes will be used to pull the welded section of the pipeline from the top of the cliff

to the bottom.

46 A section of approximately 70m to 100m of the beach will be occupied to pull the pipe

string into position and float it out to the sea. This will require a crane and a few small

plants and machinery as shown in Figure 11 where a substantially larger pipe is being

floated out to the sea. No permanent structures will be required for this operation.

The disturbance of the beach will be minimal and temporary. It will not require any

reinstatement works apart from the cleaning of the beach to remove any construction

material.

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Figure 10: Typical beach set-up to float the pipe out to the sea (source of photo: triton-marine.com)

Excavation of the seabed

47 The ocean outfall will need to be embedded in the sea bed with approximately 1.0 to

1.5 m of cover to avoid damage by the driftwood rolling along the seabed. The

offshore section of the proposed wastewater outfall can be constructed by either

dredging or using self-sinking anchors. The final selection will depend on the plant

and machinery available to the nominated contractor. I consider that dredging is the

more likely method, however, I have outlined both processes below.

Dredging methodology

48 Dredging may be undertaken using one of many options, including barge-mounted

dredger, backhoe dredger, suction dredgers, water injection dredgers, or jetting. It is

possible to dredge up to 350m of the alignment to form a trench. Dredged material

will be placed adjacent to the underwater trench temporarily until the pipeline is strung

and placed into the trench and backfilled. The total volume of the dredged material

will be up to 1,000m3.

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Figure 11: Image of a backhoe dredger in operation (source of photo: https://www.youtube.com/watch?v=gzKjyNW15lU, Engineering, NZ)

49 Given that the geology will be similar to the geology sampled on the adjacent shore, I

anticipated that turbidity will be limited during excavation as the material will be

generally coarse and will settle quickly.

50 Once the entire 350m of the pipeline is ready, the ends will be sealed without filling

the pipe with water and floated out to the sea with the help of tugboats. Once in the

sea, the pipe will be aligned and held in position with tugboats and slowly filled with

water to sink it into the trench in the seabed. Once the pipeline is in place, the trench

will be backfilled with the adjacent dredged material.

Figure 12: Aerial view outfall pipe being held in position before sinking (source of photo: Delaware Public Media - delawarepublic.org)

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Self-sinking anchor methodology

51 In this method, specially designed anchors will be installed on the pipe at regular

intervals. These anchors facilitate the pipe to bury itself in the seabed over a short

period due to the dynamic environment. The design of the anchor blocks will ensure

that the diffusers stay upright when the pipeline is sunk to the seabed.

52 An issue with self-sinking anchors is there is less control over where the pipeline

‘settles’. Unlike dredging, where the pipeline is laid in place, self-sinking anchors take

time to settle into place and can move. Besides, the high energy of the sea bed in this

location means the likelihood of material hitting the pipeline before it is buried, and

potentially damaging the pipeline or the diffusers, is increased.

Installation of Diffusers

53 The three diffusers will extend up to 1.0m above the seabed level and will comprise

smaller diameter pipelines with risers allowing discharge through duckbill fitted rosette

diffusers.

Duration of Construction:

54 We have estimated the overall duration of construction to be in the order of 8 to 10

months. This is assuming that the onshore, coastal, and offshore sections will be

constructed in sequential order, and trenching is the predominant method of

construction onshore (with microtunnelling where required), microtunnelling in the

coastal section, and dredging in the offshore section. This comprises of,

i. Up to 5 months to complete the onshore section.

ii. Up to 3 months to complete the coastal section, and

iii. Up to 2 months to complete the offshore section

55 In addition to the above construction durations, the establishment on-site and the

enabling works required are expected to take approximately 4 months. Enabling

works include:

i. Locating any other services in the road reserve and plan to avoid conflict;

ii. Clearance of vegetation;

iii. Construction of the temporary access track;

iv. Excavating drive/launch shafts for microtunelling equipment;

v. Design and construction of temporary works, and

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56 Therefore, I estimate the total duration of construction to be 14 months.

57 The construction period will be reduced if the nominated contractor proposed to use

multiple crews progressing the construction of various sections concurrently.

Likewise, if there is inclement weather, the construction period could be

proportionately longer.

Operation and management of the outfall

58 The operation and management of the outfall over the entire lifecycle of the pipeline

will include the following:

Inspection and maintenance of the pump-station

59 Inspection and maintenance of the pump station will include inspection of the pumps,

control valves, and control systems (SCADA/Telemetry) to ensure the pump-station is

pumping wastewater at the design flow rates. It is typical to have redundancy (duty

and standby) in pumping capacity to ensure the wastewater can be pumped at the

design rates despite one or two pumps being under maintenance. It is typical of

pump-station designs to have control valves that allow flows to bypass a pump that is

being taken out for servicing. Pumps typically have a life expectancy of 10-15 years.

As such, the need to replace them arises less frequently.

60 The control valves will be routinely checked to ensure they open and close as

designed. Valves not functioning satisfactorily will be replaced. This may require

pumping to be stopped temporarily. Such shutdowns for replacements will be done

during low production periods, by using redundant storage capacity in the treatment

plant and the pump-station, or during periods when it is appropriate to irrigate

wastewater to land. The frequency of replacing valves is very low as the valves are

designed to last between 35 and 40 years before needing to be replaced.

Inspection and maintenance of air and scour valves

61 This will include routine inspections to ensure the air valves release air entrapped in

the pipeline and let air into the pipeline when the pumping is temporarily stopped for

maintenance. Scour valves are inspected to ensure silt build-up in the pipeline can

be flushed out.

62 Silt built up in the pipeline will need to be flushed out routinely to maintain the

conveyance capacity of the pipeline. This is done by sucking/flushing out a small

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amount of wastewater with silt from the pipeline via the scour valves. When the

suction method is used, the scour valve is connected to a vacuum suction truck that

sucks out silt in the pipeline. When the flushing method is used, the scour valve is

opened to flush out the silt from the pipeline. The silt flushed out will collect in the

valve chamber, which is sucked out using a vacuum suction truck.

Inspection and maintenance of control valves

63 The operation and maintenance of control valves along the alignment of the pipeline

will be similar to that of the valves in the pump-station. Valves along the length of the

pipeline will be housed in valve chambers similar to manholes. A member of the

maintenance team will enter the valve chamber for inspection and maintenance.

Traffic management will be required to undertake inspection and maintenance of

control valves along the length of the pipeline. These inspections could be in the

order of once every 5 years.

Inspection and maintenance of diffusers

64 The duckbill valves at the end of the diffuser arms are prone to damage from the

debris rolling at the bottom of the sea due to the dynamic environment. These valves

will need to be inspected for damage and replace as required. I note that the section

42A report recommends visual inspection of the outfall pipe and outfall diffusers once

a year and after any significant tsunami event. This recommended frequency is

adequate. Breaking of these valves will not affect the dispersion of wastewater as the

modelling undertaken by my colleague Mr. Lobo Coutinho is based on having no

duckbill valves. Therefore, the inspection of these valves does not need to be

frequent. Inspection and replacement of the damaged diffuser heads will be done by

divers during periods when it is appropriate to irrigate wastewater to land.

Assessment of Effects

65 The construction of the proposed pipeline will have some temporary impact on the

environment because of the land disturbance activities and marine work. Such an

impact can be mitigated satisfactorily through standard construction management

conditions, as is proposed in the conditions.

SUMMARY AND CONCLUSION

66 The construction of the proposed wastewater outfall will be constructed in three

distinct parts using three distinct construction techniques. Most of the on-shore

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section will be constructed using the conventional trenching method. Microtunnelling

will be used to cross the irrigation channels, Morven Glenavy Road and the South

Island Main Trunk Railway. Microtunnelling will also be used to construct the coastal

section. In sections where microtunnelling is used, the wastewater pipeline will be

housed in a 600mm to 1,000m casing pipe. Microtunnelling will also be used to

construct the coastal section.

67 The offshore section will be constructed using the dredging method to excavate a

trench in the seabed. The ends will be sealed without filling the pipe with water,

floated out to the sea with the help of tugboats, and sunk to the seabed. Once the

offshore section is the excavated trench, it will be backfilled using a backhoe dredger

or similar. While there are other practicable methods, the above method is the likely

method used to construct the pipeline.

68 The construction of the proposed pipeline will have some temporary impact on the

environment because of the land disturbance activities and marine work. Such an

impact can be mitigated satisfactorily through standard construction management

viz., suitable erosion and sediment control measures, progressive reinstatement of

disturbed areas. Therefore, the proposed construction activities are expected to have

only a temporary and minor impact on the environment.

______________________

Suman Khareedi

28/05/2020

11538204_1 24/24

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