Under Water Screen

1. Client, Contract No.: EPC Contract Name: Fuluasou
Date and time: 29/08/2018|2.00pm – 4.00pm Purpose of visit: General site visit
Inspection by: Alfred Matatia Accompanied
by:
Weather at time of visit: Fine
Plant on site:
Powerhouse:
• No Plant
Penstock:
• 1 x EX250
• 1 x EX140
• 1 x EX100
• 1 x EX70
• 1 x 10ton Tipper Truck
Health and Safety:
Powerhouse
• No Health and Safety Issues
Penstock
• Excavation of the penstock has reached CH2461. The depth of excavation at this location is in excess
of 5m. There has been no effort by the contractor to bench back the trench or employ methods of
protecting labourers going into the trench to install the pipe. There have been numerous attempts in
the past for the contractor to comply with the safety standards required of the project. Their approach
to health and safety has been very casual especially with the standards required in working in confine
spaces and trenches. The consequence of the trench failing will be catastrophic and the contractor
MUST employ the necessary safety measures to ensure the protection of all labourers.
Work in progress during visit:
Powerhouse
• Commissioning of the LV system and the Main Distribution Board
• Earth testing at the Powerhouse to determine the impedance levelwith the completed earthgrid
Penstock
• Dam Site
• Preparatory works for the concreting of the thrust-blocks at CH126, CH140, and CH166
• Screening of the backfill material
• Craig’s Compound
• Excavation of the penstock route through the Craig’s compound was ongoing during the site
visit. The works have reached CH1595
• Powerhouse Site
• Excavation at the powerhouse site remains at CH2461
Any problems or delays apparent:
Powerhouse:
• The transformer governing the operation of the chain-block on the crane has been damaged due to
moisture seeping into it as a result of exposure to the elements prior mounting of the crane. Works are
now underway to source a new transformer.
• Issues remaining from the Progress Report on the 21/08/2018
• The contractor is still yet to furnish an electro-mechanical works program. The secondary
concrete is still yet to be poured, with the electro-mechanical contractor to furnish all the
embedment plates and hold-down bolts..
• Issues remaining from the Progress Report on the 09/07/2018
• The shutter door is to be mounted on the side (the side inside the powerhouse) of the lintel
beam at the main entrance. The lintel beam is 200mm wider (towards the inside of the
Powerhouse) than the masonry units which form the side frames of the shutter door.
Consequently, this would leave a gap between the door and the side frames and there won’t
be a support for the door guides. There is a need for the contractor to address this and

2. provide an amended design with designer approval.
• Issues remaining from Progress Report 23/02/2018
• EPC issued a stop notice on the planned pour (90m3
) for the walls and thrust block on 14th
February until a full review of calculation and proposed remedial works were carried out. A
release notice was later issued on the 15th
February for the pour to be carried out. However,
the contractor did not advise the time of the rescheduled pour (happened on Monday 19th
February). Issues which remained from the visit on the 15th
of February 2018 were:
• Trimmer bars have not been placed around the pipe at entry and exits points of the
reducer
• Concrete at the base of the PH Thrust Block forming the Construction Joint has not
been scabbled to maximise contact area for bonding
An assessment on whether PEP had addressed these issues prior to the pour could not be
carried out. Further to this, there were additional U-Bar reinforcements indicated by the
contractor that would be placed around the reducer spanning its full length. Details of which
are still yet to be provided, and confirmation of whether or not this was carried out could also
not be carried out.
Penstock:
• The screens for the intake are still to arrive on site. Discussions with the contractor revealed that the
screen will be manufactured from Galvanised Steel. However, it is a requirement under the contract
that all screens shall be manufacturers from 316 stainless steel material as per the figure below. A
request was put through to the contractor to confirm the material of the screen.
• Issues remaining from the Site Report 21/08/2018
• Heavy downpour over the weekend has resulted in the inundation of the thrust block
formwork with debris and sludge. The contractor is to remove all the debris and sludge
from the base of the Thrust Block prior to the concrete pour.
• Issues remaining from the Site Report 16/08/2018
• There is a need for the contractor to compact the subgrade for the Thrust-blocks at CH126,
140, and 166. The vicinity of the thrust blocks to the river makes it prone to frequent
changes in water table. This will inevitably result in the consolidation of the concrete
masses and the potential failure at these locations.
• At CH140, no trimmer bars were placed on the thrust blocks. The concerns were raised
with the contractor.
• Issues remaining from the Site Report 07/08/2018
• There is an urgent need for scour protection to be employed from CH153 to CH91 to
protect the pipe. Works in widening the river channel at these locations is also necessary to
lower flood elevation to mitigate scouring.
• There is a need for the contractor to lower the lifts employed at haunching the backfill at
the pipe sides to ensure the required SPD for the backfill is achieved.
• Issues remaining from the Site Report 25/07/2018

3. • There are concerns with the current alignment of the penstock at the dam site particularly
from CH153 to CH91. As shown in the attached photos, the alignment of the old penstock
(which is now what the contractor has adopted) is located directed at the top of the river
embankment. The concrete saddles which carried the old penstock for this section have
now been removed. The saddles provided a passive form of scour protection for this
particular section. The main concernnow lies with the risk of the penstock failing at this
section as a result of backfill scour from flood flows given its high level of exposure and
lack of scour protection. Therefore, it is prudent the contractor immediately construct scour
protection measures at this section after the penstock has been laid.
• At the location of SWA scour line (Approx. CH230) there is a 90° cross-over with the
penstock. The minimum allowable cover from the crown of the SWA scour line to the invert
of the penstock is 175mm. This has not been achieved. The contractor is to remove the
pipe section traversing the SWA scour line, have SWA install their scour line 1st
, then
compact 175mm from the crown up of the SWA scour line. This shall form the bedding for
the pipe section removed. These concerns were made known to the contractor on site with
the need to compact the SC2 material around both pipes to 90% of its SPD
• For the golf course; the issue still remains with the current width of the trench not allowing
for compaction of the backfill material at the side of the pipe. This concern has been raised
with the contractor; and also raised in the past 2 site reports.
• Issues remaining from the Site Report 19/07/2018
• The minimum allowable trench width for a 1.1m DIA pipe is 1.980m. The measured width
at CH2369 is 1.450m - approximately 175mm from each side of the pipe to the trench wall
measured at the springline. The main concern lies with the side of the pipes not been
properly compacted given that the width of the plate compactor is larger than the allowed
width at the pipe sides. The structural support for the pipe is by and large provided by the
compacted fill surrounding the pipe, hence the importance of having the fill at the pipe zone
compacted cannot be understated.
• Rev 6.0 of the pipe laying manifest shows a pipe cover of 0.95m at CH2369. The existing
cover however is approximately 2.4m; a difference of 1.45m.There is a need for the
contractor to re-confirm all levels to ensure there are no localised low points along the
pipeline that may introduce negative pressures.
• The bedding at CH1429 was found to be 75mm thick. The minimum bedding requirement
is 100mm. This concern was made known to the contractor on site.
• Issues remaining from Site Report 27/06/2018
• For the excavation and pipe works between CH383 and CH271; there were a number of
concerns noted on the installation procedure and also the quality control on the installation
itself.
• The minimum width of the trench should be 1.62m for this particular section (900mm
DIA). However, at some locations along this section the width measured from the
trench wall to the spring line of the pipe isn’t sufficient to fit a plate compactor to
compact the backfill. The compaction of the backfill is vital in achieving the design
bearing support for the pipe, yet it is apparent that no compaction is taking place at
areas where they cannot accommodate the plate compactors. These concerns were
made known to the site supervisors
• The compacted bedding at the location of the pipe collar should be marked out prior
to pipe placement and a 25mm deep pocket should be excavated to ensure that the
pipe does not site on its collars spanning its length and the pipe is continuously
supported along its length. However, this was not observed on site. The pipe at
CH303 was supported at its collars; the risk remains that the overburden will induce
stresses along the pipe invert thus compromising the structural integrity of the pipe.
This was made known to the site supervisor.
• 1 x 11.5m, 1 x 22.5° Bend, and 1 x 5.85m Pipe were found to have structural
damages to them. These pipes were removed by the contractor due to alignment
changes prior the site visit. However, these damages were pointed out to the
contractor to ensure that the appropriate repairs are undertaken on the pipe before
any plan to use them again.
• The contractor has adopted a “Type 2” Installation for the penstock works. However,
there is no evidence of compaction of the SC3/SC4 material from the 60% DN zone
to 300mm above the pipe crown.

4. • The pipe laying through the golf course has stopped at CH2335. This was due to damage
sustained by the rock breaker attachment during excavation through this section. Tests for
vertical deflection and pipe deflection were undertaken for pipes at CH2335 and CH2323. The
vertical deflection tests carried out on both pipes (1.69%) were within the deflection limits
(3%) stipulated by the Flowtite manual. The pipe deflection test carried out on the pipe at
CH2335 showed a deflection of 2.5° which is well over the limit of 1° for a 11.5m pipe. There
is an urgent need for the contractor to implement measures to rectify the excessive deflection
on the pipe.However, from observation the first action to be taken by the contractor is to
widen the trench at this location to allow any changes to the alignment. It was also noted that
the current trench width was too narrow to accommodate the haunching and compaction of
backfill material using a plate compactor. The need to compact the backfill cannot be
understated.
• Issues remaining from Site Report on the 01/05/2018
• On the 28th
of April 2018, there was flooding at the Fuluasou River. At CH1365 (next to the
river), the penstock was not capped at the upstream end; consequently flood waters
inundated the pipe and the open trench downstream of CH1411. The trench is now inundated
with silt and organic materials. There is a need for the contractor to remove all the organics
and silt and re-bed, backfill, and compact the approved material.
• Issues remaining from Site Report 24/04/2018
• Issueshighlighted in the Health and Safety Section in the site report on the 21st
of April 2018
still has not been addressed. These concerns were made known to the Country Project
Manager and no works have been done to date to ensure the safety of all labourers working
in the vicinity of the High Voltage cables.
• Contractor to cap off pipe ends at the end of every day to prevent ingress of debris
• Issues remaining from Progress Report 20/04/2018
• Pipe laying operations have now extended to CH1411 from CH1365 on the 11/04/2018. The
material used to bed the pipe is the same material which is currently being tested by LTA as
per resolution reached on the 11th
of April 2018. If the test results from LTA reveal that the
material currently being used falls outside the specification; then all the pipes should be
removed. It remains prudent the contractor source a guaranteed approved material for the
time being to avoid unnecessary works.
• Large rocks from the have fallen into the trench and are wedged against the pipe and trench
wall. There is a need for the contractor to remove all the large rocks that have fallen in as a
result of the heavy downpour.
• Issues remaining from Progress Report 09/04/2018
• Works for backfilling and pipe-laying have stopped at CH1209. The total length of pipe in
which the unapproved backfill material was used is 85m (CH1124 to CH1209). The same
concerns have been raised with the contractor on the 27th
, 28th
of March, the 4th
of April and
now today. The backfill and bedding material being used has not only a high fines (organic)
content but also a high proportion of rocks exceeding 32mm. The risk of underground
pressurised vessels failing as a result of the wrong bedding is well documented and therefore
cannot be understated. Further to this, the design life for all the civil structures allowed for in
the specification is 100 years. The use of wrong bedding material, in effect shortens the
lifespan of the scheme. The actions required for this section are:
• The contractor to supply the correct bedding material
• Pipes from CH1124 to CH1209 need to be removed and re-bedded and backfilled
with the correct material.
• The need for the contractor to address this on-going issue is CRUCIAL.
• Issues remaining from Progress Report 04/04/2018
• Work on laying the penstock and compacting still continues on without the appropriate
backfill material from CH1124 to 1166. The same concerns were raised with the CPM in
the previous visits on the 27th
and 28th
of March. The actions go in contrary with
instructions issued by the Project Manager on the 28th
of March rejecting the materials
currently being used.
• Issues remaining from Progress Report 28/03/2018
• There are still concerns regarding the material being carted to site as raised in the previous
site report. After raising it for the second time with the PEP Country Project Manager
(CPM); the position he took(contrary to earlier discussions) is that the material carted to

5. site is the same material that was used in the previous lengths of pipe – which was
approved. It was made known to CPM that the material on site does not satisfy the
specification for bedding material to be used on the pipe and that a suitable material needs
to be provided. In moving forward the contractor is now sourcing a suitable material to be
carted to site.
• Issues remaining from Progress Report 27/03/2018
• Major concern lies with the quality of bedding material and backfill currently being used on
site. The material used has very high fines content with a significant proportion of rocks
exceeding 32mm. The grading envelope for the material characterises it as an SC4 type
material. Given that these areas are below the 100 year flood level, this makes the pipe
susceptible to piping failure through the migration of the fines. Furthermore, the presence
of large rocks in the backfill makes the pipe prone to indentation/piercing from rocks
directly on the face of the pipe under traffic loading. Therefore, it should be HIGH priority
for the contractor to remove the pipes affected by the wrong bedding material and supply a
new approved material satisfying the specifications.
• Issues remaining from Progress Report 21/03/2018
• The proposed thrust block for the fabbed elbow at CH861, has already been backfilled with
the intention that it will be re-excavated when construction of the thrust block takes place at
a later date. The problem however, is that PVC pipes for the fiber optic complete with draw
wires have been installed with no slag provision. This will mean that the fiber optic would
have to be cut and spliced to allow for the works to take place. Given that the contractor
has opted for this methodology, it is recommended that provisions should be made at these
locations so to minimise the need to cut and re-splice the FO cable
• Issues remaining from Progress Report 05/02/2018
• CH861 to CH863 is the 1 miter band 0 to 30° elbow which is also the location of the thrust
block. Backfilling has taken place at the elbow to minimise movement while joining the
subsequent downstream pipes. Consequently, this has taken the space allocated for the
steel reinforcement to go in, meaning extra work will be carried out to re-excavated the
sides and below the pipe to allow for the steel work. The delay in construction is due to
PEP not furnishing the final detail designs incorporating all changes indicated by EPC.
General observations on work in progress:
Powerhouse:
• The embedment plates for the turbine and generator are yet to be installed. The secondary concrete
hinges on their setting into place with the hold-down bolts.
• Electro-Mechanical works are still to commence with an indicative programme to be forthcoming from
the contractor the installation of the Main
• The LV Main Distribution Board has been completed and commissioned. The outstanding immediate
works is for the installation of the transformer and the mounting of the switchgears. There hasn’t been
any indication on who will be responsible for the termination works for the switchgears.
Penstock:
• The intake structure (Screens and Gates) has arrived on site. Tentative works program indicated by
the Contractor has a commencement date for early next week with an official program to be submitted.
• There is an urgent need for the contractor to implement scour protection from CH153 to CH91. With
the rainy season approaching; there is no guarantee that the current easement within this section
would withstand high flood flows. Discussions with the country project manager indicated that their
preferred scour protection method would be gabions given the depth of the pipe and the steep slopes.
It was raised with the contractor that the gabion baskets would then have to be coated with ultra-violet
stabilised polyvinylchloride given the level of exposure. It was also indicated that EPC are still yet to
decide on the what is required to be done at this location, it was highlighted to the contractor that it is
their responsibility to assess where scour protection is needed as highlighted in Task 2 of their bid.
Stantec/EPC to note/address (Recommendations):
Powerhouse:
• Contractor to furnish electro-mechanical works program
• Contractor to repair damages to the crane transformer
• Contractor to provide correct rocker pipe length at Powerhouse Thrust block (1.1m to 2.2m)

6. Penstock:
• Contractor to construct scour protection along sections CH153 to CH91 immediately after the
installation of the penstock at this section
• Contractor to provide road crossing methodology
• Contractor to provide new approved bedding material for sections of pipe where the SC3 material was
being used as the bedding material
• Contractor to address the QA Issuesas highlighted in this report
• EPC to have personnel to verify the quantity of rock being broken, excavated, and carted off site at the
golf course site
Further actions required:
NIL
To be actioned by:
NIL