Biện pháp thi công mở rộng tuyến cống hạ tầng đô thị song ngữ bản English

SITE ORGANIZATION AND CONSTRUCTION
METHODS
Name and form of Bidding: Extension of sewer systems
Bid package:
The Employer:
PART 1 – GENERAL INTRODUCTION
I. INTRODUCTION TO THE BID PACKAGE
1. Introduction to the Bid package
Structures (Manhole, CSO, discharge outlet):
A flow separation outfit (CSO) for basin D shall be constructed as referred in
Drawing LT2-MS_OutD-…
In addition, 100 special and typical manholes shall be constructed as referred
in Drawings LT1-3-MS-MH-T-… and LT2-MS-MH-S-… .
Route of works:
In Bid package 2, the following major sewers (grade 1 and grade 2) shall be
constructed as referred in Drawing LT2-MS-PP-…
Code

Basin

Point US

Point
DS

Length

Name of roads

[-]

[-]

[-]

[-]

[m]

[-]

C

C

C01b

C05

170

CC

C

CC1c

CC1d

17

D

D

D00

D08

487

DA

D

DA00

DA03

158

DA

D

DA03c

D05

5

DA-1

D

DA01-1

DA01

22

DB

D

DB01

D06

383

DBA

D

DBA1

DB05

151

DBB

D

DBB1

DB06

98

DC

D

DC01

D04

270

1|Page


Code

Basin

Point US

Point

DS

Length

Name of roads

[-]

[-]

[-]

[-]

[m]

[-]

F

F

F01

F05

146

FA

F

FA02

F05

28

GB

G

GB01

G08

404

GBA

G

GBA1

GB06

154

GBB

G

GBB1

GB08

158

JCA

JN

JCA1

JCA5

147

JCB

JN

JCB1

JCB2

94

Total:

2,892

Grade 3 sewers in alleys:
In Bid package 2, the total length of conduits is approximately 1800 m,
which shall be constructed in a total of ~ 15 alleys according to Drawing LT2TN-A- .... Of which 1,800 m, approximately 620 m including DN300 to DN500
is placed in the middle of the alleys and around 1,400 m is conduits DN200 for
the connection of some household connection boxes to conduits DN300 to
DN500.
Grade 3 sewers in roads:
In Bid Package 2, the total length is about 6,350 m for conduits DN200 to
DN300, they shall be constructed on pavements along the road routes. In the
case of pavement obstructions that prevent the construction on such pavements,
conduits shall be placed close to the road surface. Main areas for construction of
the grade 3 route along the roads are basins D, G, F and JN as referred in the
Drawing LT2-TN-S...;
2. Completion duration: 18 months

2|Page


PART 2 CONSTRUCTION ORGANIZATION
I. Organizational structures of the Site:
PROJECT MANAGER

GIá M Đ ốC Dự á N

SUPERINTENDENT
c hỉ
h uy t r ở ng

MANAGE

MENT OF
quản
EQUIPMEN
lý
T,

ON-SITE
ENGINEERI
bộ
NG
phận
DEPARTME
kNT
ỹ

tMATERIAL
h iết
S,
bị
t hu ật
STOREKEE
vPER
ật
h iện
t ,
t r ờ ng
THủ
KHO

SURVEY
Tổ
k s,
TEAM
t r ắc
địa

CONCRE
Tổ
TE TEAM

BÊ
TÔNG

QUALITY
MANAGEM
bộ
ENT
phận
DEPARTME
quản
NT

lý
c hất
l ợ ng

REINFOR
Tổ

CED
Cố T
CONCRETE
TEAM
THé
P

ADMINIS
TRATIVE
bộ
DEPARTME
phận
NT

hành
c hính

SCAFFOL
Tổ
DING TEAM

Cố P
PHA

SAFETY
SECURITY
bộ
DEPARTME
phận
NT

đảm
bảo
an
t o àn

CONSTR
Tổ
UCTION
THI
TEAM 1

cSUPERVISOR
á n bộ giá m
sá t

LABORATOR
Y DEPARTMENT
bộ

phận
t hí
n gh iệm

ENVIRON
bộ
MENTAL
MANAGEME
phận
NT

quản
DEPARTME
NT
lý

môi
t r ờ ng

CONSTR
Tổ
UCTION
t hi
TEAM 2

CONSTR
Tổ
UCTION
t hi
TEAM 3

CÔNG

c ô ng

c ô ng

Số 1

số 2

số 3

II. Description of organizational structures of the Site:
* Project Manager:
The Project Manager is the highest decision-making person and directly to
units in the Site for effective performance of provisions under economic
contracts. The Manager shall have the right to coordinate the progress schedules,
general construction quality at the site for arrangement and adjustment of tasks
among units, coordinating works, mobilizing equipment and materials in the site
in accordance with capacities of the units as well as ensuring the progress.
* Superintendent:
Be fully responsible for implementation and assurance of the quality and
efficiency. Directly providing orders to construction units as well as ensuring the
relationships with supervisors of the Employer and design agency.
* On-site Technical Department:
Under the management of the Superintendent in terms of construction
performance and construction management, including: method planning and
implementation of construction measures.
* Quality Management Department:
Quality Management Department shall manage all issues within the scope
3|Page


of contracts relating to the quality, such as:
- Organizing the quality management system for the site.
- Preparing project quality assurance plans and implementation monitor.
- Coordinating with the Employer, partners to supervise the quality
management of works, ensuring the quality of the package.
* Administrative Department:
Administrative Department shall be under the direct management of the

Superintendent and implement the following tasks:
- Performing administrative works of the Site such as document
management;
- Organizing and proposing the purchase of all materials for the project
and material management.
- Carrying out external relations with government agencies and other
relevant agencies and organizations..
* Safety Security Department:
In charge of guiding, supervising and making the first-aid in case of
accidents at the site through the first-aid stations. Ensuring the labor safety
activities as required in the contract and this requirement.
- Preparing detailed construction safety plans during the construction to
submit to the Employer for approval and implemented during the construction
period of the bid package.
* Laboratory:
The Laboratory shall be responsible for testing and inspecting the quality,
this Department is equipped with a full range of test equipment, measuring
devices relating to the objects to be tested.
Material Testing Department and Quality Inspection Department have
proper work-related equipment to control the quality of inputs from other
suppliers.
* Environmental Management Department:
Environmental Management Department is responsible for guiding and
supervising construction activities that affect the environment according to
requirements of the Project.
- Environmental Management Department shall, on behalf of the
Superintendent, disseminate all directives and instructions related to the
environmental impacts according to requirements of the Project.
* Department of materials, equipment and storekeeper
4|Page

Department of materials, equipment and storekeeper is responsible for
supplying materials and equipment to ensure that the construction items are in
accordance with the design, procedures, current regulations as well as meet the
highest requirements of the construction progress and quality of the works.
III. Layout of construction site:
The Contractor shall undertake the study of approved documents and
receive the landmarks, elevation piles. Based on actual conditions, the
Contractor shall compare with the design documents, in case of defects, the
Contractor shall submit to the Employer and Engineers for review and repair
according to actual conditions at the Site.
Each specific duty shall be prepared in advance as planned to avoid
overlapping works and ensure the construction progress as required.
The Contractor plans to arrange 01 Site Management Board, site-huts in
convenient areas for the purposes of construction.
Auxiliary works include: Headquarters of the Project Management Board
of the Bid Package, houses for staff, workers, information and living facilities,
sports and entertainment facilities, material storehouses and gathering yards of
materials, construction equipment etc.
Based on the actual terrain conditions, the Contractor plans to execute the
works in a sequential way according to the progress assurance procedures and
the quality of the works.
The work items of the Project Management Unit are constructed
alternatively. Include the following construction teams:
+ Survey team.
+ Reinforced concrete team
+ Scaffolding team
+ Concrete construction team.
+ Construction team of conduits including: construction team No. 1, 2,

3….
IV. Arrangement of signs and barriers
To ensure environmental sanitation
To ensure labor safety for people, construction equipment and works
To place signs, traffic signs, mobile barriers at the site to prevent people,
means and animals from accessing to the item.
V. Supply water and power for construction
5|Page


* Power sources
Power sources are connected from the local power grid. Electric wires are
rubber cables. Main circuit breakers and meters are installed at the power
sources. Power transmission lines are connected along to the fences. The
Contractor uses two 50KVA back-up generators to supply the power.
* Water
Water for construction and firefighting is taken from wells to prevent
long-term water loss.
VI. Material sources:
All materials used at the site must meet Vietnamese standards with quality
registration of the manufacturer.
The Contractor undertakes that all types of materials used for the works
shall be submitted to the Engineers regarding to the sources of supply and
must be thoroughly tested in accordance with the requirements as stated in the
Bidding Documents and approved by the Employer.
(Sources of materials are based on legal documents)
List of materials used for the construction
No.

Content

1

Cement PC30

2

Ballast

3

Yellow sand

4

Round bars

5

Types of uPVC conduits and
reinforced concrete culverts

Standard
TCVN 6016-1995; TCVN
6017-1995; TCVN 4030–
85; TCVN 141 : 1998
TCVN 7572 - 2 - 12 :
2006; TCVN 7570 - 06.
TCVN 7572 -1- 8: 06;
TCVN 7570 - 06

TCVN 1651 - 2008
Current
standards

Vietnamese

Note:
- All above mentioned materials must have certificates of the
Manufacturer.
- The Contractor shall check specifications of materials before putting
into use.
6|Page


- Materials must be tested before being put into use and approved by the
Engineer;
VII. Transportation
The Project is located close to the traffic roads, equipment and materials
shall be transported by roadways.
VIII. Procedures, norms and specifications used for the construction and
acceptance:
- TCVN 9398:2012 : Surveying in construction - General requirements.
-TCVN 4447-2012: Earth works - Construction, check and acceptance;
-TCVN 9394:2012: Pile driving and static jacking works – Construction, check
and acceptance;
-TCVN 8859 -2011 : Graded aggregate bases and subbases pavement
specifcations for construction and acceptance;
-TCVN 8859-2011: Specification for Construction of Hot Mix Asphalt Concrete
Pavement and Acceptance;
-22TCN 247-98: Construction standards and acceptance of prestressed concrete

bridge beams;
-TCVN 5308 -1991: Technical regulations on Safety in Construction.
-TCVN 5674:1992 Finised works in construction – execution, check and
acceptance;
-TCVN 1771 – 1986 : Gravel, crushed gravel used in construction - Technical
requirements;
-TCVN 4314 -1992: Mortar for masonry – Specifications;
-TCVN 4452:1987: Kết cấu bê tông và bê tông cốt thép lắp ghép – Thi công và
nghiệm thu;
-TCVN 4453 -1995 : Prefabricated concrete and reinforced concrete - Codes for
construction, check and acceptance;
-TCVN 9202:2012: Masonry cement;
-TCVN 4085 – 1985: Brick, stone structural - Codes for construction, check and
acceptance;
-TCVN 5640 -1991: Hand over of building works - Basic principles;
-TCVN 4252 – 1988: Procedures for formulation of the building organization
design and the building works design. Construction regulations and acceptance;
-TCVN 2287 -1987: Labour safety standards system - Basic rules;
-TCVN 4086 -1985: Electrical safety in construction – General requirements;
-TCVN 3255-1986: Explosion safety- General requirements;
-TCVN4244 – 1986: Safety regulations of heavy equipment;
7|Page


-TCVN3254-1989: Fire safety- General requirements;
-TCVN 3508 – 1991: Technical regulations on safety in construction;
- And other current standards and regualtions;

8|Page

PART 3 – GENERAL CONSTRUCTION METHODS
A/ PREPARATION:
1. Taking over the site and inspection
The Contractor shall take over the site after the Employer decided to hand
over the site. The process of taking-over and handover of the site shall be
attended by all stakeholders including Employer, Design Consultants, Engineer,
Constructor and cadastral management units.
After handing over the site, the Contractor shall receive the landmarks,
including the boundary landmarks of the bidding package, landmarks of land
clearance, landmarks of construction corridor, design landmarks, landmarks of
design elevation and piles, if any), (central piles, curve piles, edge piles of talus
etc.);
After taking over the site and landmarks, the Contractor shall check
current status. In case of any difference between the current status and the
design, the Contractor shall submit to the Employer and Engineer for review and
repair in accordance with current status.
Constructing barriers, signs at the Site for each location.
Determining the elevation and driving piles for each work item.
2. Construction of site-huts, gathering yards of materials and equipment
Based on the current site, natural conditions, climatic conditions,
surrounding infrastructures and construction volume of the Bid package, the
Contractor shall make specific calculations to arrange and construct site-huts,
gathering yards etc. in the most reasonable manner.
Construction works include the Headquarters of the Project Management
Board of the Bid Package, houses for staff, workers, information and living
facilities, material warehouses, gathering yards of materials, construction
equipment etc. The Contractor shall level these auxiliary works and backfilled
by ballast with the thickness of 15cm and covered with mortar M75 with the
thickness of 3mm.

For the access roads, the Contractor shall execute ballast with thickness of
15cm for the construction works.
Power sources for production and daily life are connected from current
sources used for the construction site. To prevent any interruption, the
Contractor shall reserve 02 generators.
The water sources used for production and daily life are from the current
water sources. The Contractor shall use tankers to transport water to locations
9|Page


where water is not available.
3. Management, relocation and positioning of piles at the Site:

For piles, stakes, important details within the construction site, the
Contractor shall apply measures to move to other locations and prepare
positioning plans without changing during the construction process.
After completing the management plan for reallocation of piles, the
Contractor shall hand over a set of documents to technicians and Engineers for
supervision during the construction process.
4. Preparation and gathering of materials
Based on construction volume, requirements of works and construction
progress of the Bid package, the Contractor shall prepare and gather material
according to types, quantity and time of use.
The Contractor shall mobilize materials and supplies based on the
material mobilization schedule for the bid package.
The Contractor shall use high-quality materials and supplies in
accordance with requirements of the Bid package and current regulations and
standards of the State.
The Contractor shall only use materials and supplies for the Bid package
in case of the quality certificate. Before use, materials and supplies must be

tested and approved by the Employer and Engineer.
The Contractor shall prepare sufficient quantity of materials to ensure
fully and timely supply.
5. Preparation of construction equipment
Based on construction volume, requirements of the works and
construction progress, the Contractor shall prepare and gather construction
equipment according to correct types, quantity and time of use.
The Contractor shall use modern machinery, equipment with high
capacity to meet requirements of the works. Prior to use, machinery and
equipment must be approved by the Employer and Engineer.
To meet the continuity of the works, guarantee the quality and
construction progress, the Contractor shall reserve equipment and machinery. In
case of failure, machinery and equipment must be stopped and replaced by
others.
6. Preparation of construction procedures
* The Contractor shall submit to the Employer the following procedures:
10 | P a g e


+ Project performance method.
+ Quality management plan.
+ Use plans of materials and supplies.
+ Origin of materials.
+ Mobilization and use plans of construction equipment and machinery.
+ Features and capacity of equipment used for the bid package.
+ Use plans of material mines (if any).
*The Contractor shall notify the Employer’s preparation of procedures as
follows:
+ Construction permits.
+ Notice to power and telecommunications companies to identify the

location of cables in the construction area.
+ Construction site map and traffic flow solution.
+ Location map of temporary storages.
+ ESHS method (as stated in the Bids).
+ Other required materials relating to the additional construction works (if
any);
* The Contractor shall apply for water and power supply, installation at the
Site.
* The Contractor shall contact to local authorities to apply for the temporary
residence of all personnel involved in the Project.
* The Contractor shall carry out procedures to transport materials and
equipment to the Site.
7. Construction and installation of formworks
The Contractor shall use steel, word formworks or Fuvi plastic formworks
during the processing process of formworks. Faces of formworks are guaranteed
to be flat and smooth as required.
Formworks shall have the same thickness. In case of using laminated
wood, the thickness shall not less than 12mm and waterproof sealant shall be
used in the fabrication.
Formworks shall have correct structures corresponding to the shape of
concrete blocks as detailed in the drawings. Formworks are designed properly
with strong structures and be approved by the Employer. In the design and
construction of formworks, the Contractor shall consider the shrinkage,
deformation or deflection during the construction process to adjust in order to
11 | P a g e


ensure that the dimension of concrete blocks is consistent with the straightness,
elevation and curvature.
Do not concrete without prior approval of concrete-related works such as

the installation of reinforcing steels, steel anchors or pre-stressed steels as well
as other written documents relating to the formworks of the Employer.
The formwork removal is performed when the concrete strength reaches
at least 75% as for wall formworks and 100% as for bottom formworks.
8. Construction methods of reinforcing steel:
* Processing of reinforcing steels
The reinforcing steels are cut and bent to the forms as shown in the
schedules. Tolerances shall be consistent with the standards. All steel bars shall
be cold bending, unless otherwise provided. Steel bars buried in concrete blocks
shall not be bent, unless otherwise provided in schedules or approved.
Sizes of anchor hooks and bending diameters measured inside of the steel
bars shall be determined according to parameters shown in the plan. If the size
of anchors or bending diameter is not shown in the drawings, provisions of Part
I, Article 8.23 “Construction code - Requirements for reinforced concrete” shall
be applied.
Each reinforcing steel shall be cut and bent to the size as specified in the
Drawings. For some structure, the number and length of steel bars may need to
be measured at the site to be consistent with the size of the structure.
As for the bending of reinforcing steels, recommendations of the
manufacturer shall be complied with in each case. All steel bars shall be cold
bending. All reinforcing steels shall be bent according to procedures of the
American Concrete Institute, unless otherwise specified. Steel bars inside
concrete blocks shall not be bent, unless otherwise specified on the Drawings or
allowed.
Authorized person shall cut and bend steel bars and use proper equipment
to do so.
* Installation of reinforcing steels
Reinforcing steels are assembled according to shapes and sizes as shown
in the Drawings. Bars are tied together firmly at intersections to form a solid
frame and fixed during the concreting process. Steel wires are not allowed to be

loosen in the surface of concrete.
12 | P a g e


Concrete blocks and fillers must ensure the strength to avoid the breaking
or cracking during the concreting. They are fabricated as small as possible and
kept in fixed places by wires. These blocks are soaked into the water just before
concreting.
The temporary support bars for reinforcing steels shall not be put into
concrete blocks without permission of the Employer.
When concreting, all reinforcing steels must be cleaned and removed
thoroughly all liquid detergent, scale, mud, oil or any other coatings that may
destroy or reduce the binding; these steel structures must be cleaned the whole
or any part for a specific equipment as stated in the notice of concrete.
The minimum distance of parallel steel bars is 2.5 times higher the
diameter of the steel bars; if the distance is not specified clearly, the distance
between bars shall not less than 1.5 times the maximum dimension of materials
used for concreting.
All reinforcing steels must have a protective layer as shown in the
Drawings. Steel bars shall be placed on concrete fillers (prefabricated) with the
same Mac with the concrete used for the structures; the thickness of these fillers
is as same as the thickness of the protective layer.
Protective layers, general limits on reinforcing steels and distance
between them shall be complied with regulations as stated in the Drawings.
9. Concreting:
* Concrete aggregate:
After receiving a written approval for materials, the Contractor shall
submit the Employer a written design of concrete aggregate.
The Contractor shall strictly comply with minimum compressive strength
of testing blocks after 3 and 7 days. After obtaining testing results, the

Contractor shall submit a written request to require the Employer to approve the
design of concrete aggregate. The concrete is only carried out when the
Employer approves the design.
* Concrete testing
- Testing of concrete strength.
Before concreting, the Contractor shall submit to the Employer with a
Concrete sampling plan.
The concrete testing shall be carried out by an independent laboratory as
appointed or approved by the Employer with consultancy of the Contractor.
13 | P a g e


The sampling is implemented at the Site with presentation of the
Employer’s representative.
Numbers of concrete strength samples are determined as follows: A
concrete sample is taken for every 50m3. Samples are marked with serial
numbers and time, work items and any other information as required. Then
samples are sent to the certified laboratory.
If 7-day testing results fail to meet requirements, the Contractor shall,
under the Employer’s guidance, carry out testing and inspection for suspected
structures. If the testing results prove that concrete blocks don’t meet
requirements, the Contractor shall demolish damaged concrete and reconstruct
such structures.
The testing results shall conform to current standards.
d- Testing of slump
Slump testing methods shall be in accordance with current standards.
According to requirements of the Employer, one or more slump test shall
be carried out. The slump test is implemented under the witnesses of the
Employer’s representative. Concrete structures are the main load-bearing
structures of the Works, so it is necessary to ensure the concrete quality

according to the design documents, procedures and norms of the State, namely:
- Technical workers shall have skill grade 3 or higher.
- Workers in charge of transporting materials for concreting shall be skill
grade 3.
- The construction process is implemented comprehensively and properly.
Materials are prepared properly with good construction equipment. The
construction process shall be executed continuously until all technical
specifications are met.
In case of rain, nylon films are used to cover the entire concreting areas.
In hot weather conditions >300C, canvas are used to cover to avoid direct
sunlight after concreting.
Concrete slump test (flexibility): Using Abrams equipment to measure the
slump.
After concreting, concrete blocks shall be covered and maintained
according to current construction regulations.
*Mixing concrete by concrete mixers:

14 | P a g e


The mixing and transport of concrete is carried out in accordance with the
requirements of applicable standards. The mixing and transport of concrete shall
be regulated to ensure that the concreting process is implemented in a
continuous status. The time of each concreting shall not be too long to void
partly solidification, that period shall not exceed 45 minutes.
The addition of water or additives shall not be carried out without prior
consent of the Employer; however, the ratio of water-cement should not exceed
the regulations.
Concrete mixers shall be operated at the speed as indicated on the
manufacturer’s nameplate. Any concrete batch that the mixing time is shorter

than the specified time shall be disposed or removed by the Contractor.
Water shall be added to the drum before cement and aggregates are added.
Water is added regularly and all water volume must be added to the drum until
the end of the first 15 seconds of mixing. Approximately 10% of the water
volume required for the mixing batch is put into the drum before cement and
aggregate are added, while the remaining water volume is gradually added to the
drum so that all water volume is added within the first 1/4 period of time of the
mixing. The mixing time shall not less than 60 seconds for the mixer with
capacity of 1.5 m3 or less. For mixers which have a capacity higher than 1.5m3,
the mixing time shall not less than 90 seconds. If the start time to set up the
mixer to the maximum capacity, further 4 seconds are calculated to the mixing
time. The mixing time is completed with the feeder is opened. The concrete is
mixed until the mixture has a homogeneous color and the consistency is
attained.
The amount of concrete in a batch shall not exceed the rated power of the
mixer. All concrete of a mixing batch shall be taken away before materials are
added for a new mixing batch. After completion or there is any interruption for
more than 20 minutes, the mixer and other equipment must be cleaned with
water. If concrete is still remained in the mixer, it must be cleaned by rotating
the aggregate and water in the drum before mixing the fresh concrete.
The mixed concrete as stated above shall not be changed by adding water
or any other ingredients.
Concrete added into the drum within one hour or stated to be solidified
shall not be used.
The slump of concrete will be measured according to current standards.
15 | P a g e


*Transport of concrete.
Transport of concrete is carried out by manual methods.

*Works of concreting.
Before concreting, formworks must be thoroughly cleaned and removed
all dirt, sawdust, chips and other debris. The outer surface of concrete shall be
thoroughly cleaned during the concreting process by using approved tools and
equipment. This work includes the removal of large-size aggregates out of the
surface, separating the mortar in the formworks to form a flat surface without
water, air bubbles or honeycombs.
Formwork shall be treated with anti-corrosion materials or saturated water
before concreting. Open formwork surfaces shall be treated with an anticorrosion agent to prevent the adherence of the concrete and must be approved
by the Employer.
The concreting work shall be carried out carefully with the height of less
than 1 meter. The outer surface shall be thoroughly cleaned during the
concreting process by using approved tools and equipment. This work includes
the removal of large-size aggregates out of the surface, separating the mortar in
the formworks to form a flat surface without water, air bubbles or honeycombs.
The Contractor shall concrete by mixers.
The concreting work shall be implemented so the water is not
concentrated to a corner or formwork surface; it is not allowed to add a large
volume of water in a specific period of time and remaining water must run along
the formworks.
All concrete should be poured and compacted in layers and bonded with
previous concrete layers. The thickness of concrete is varied from 15 to 30 cm as
for reinforced concrete and up to 45 cm for non-reinforced concrete.
* Compaction of concrete
Concrete shall be compacted continuously and carefully; especially
around the reinforcement parts and at corners of formworks so that the concrete
is tightly bonded and contains no honeycomb.
Concrete is compacted by plate vibrators or spud vibrators according to
requirements of the Employer. Do not use vibrators to compact concrete with
too high vibration.

All compactors shall have a proper diameter according to the distance of
reinforcing steels with sufficient frequency and carried out by experienced
16 | P a g e


personnel. Concrete shall be compacted at regular distance which is
approximately 10 times higher than the diameter of the vibrators and same depth
in the concrete. The vibration works shall be implemented carefully to avoid any
movement of reinforcing steels or effects on the solidified concrete. The
equipment shall not be attached to the reinforcing steels in any case. Each
compaction time shall be carried out continuously until there is no air bubble on
the concrete surface, but shall not exceed 30 seconds. The vibrators shall be
removed slowly and in the vertical direction to ensure that no air bubble is
generated.
The concrete shall be compacted by vibrators as approved by the
Employer. Whenever necessary, vibration works shall be supplemented by
shovels or suitable tools to ensure proper compaction.
The Contractor shall prepare the back-up equipment during the
concreting.
All works of compaction and completion shall be completed right after
concreting.
Workers are not allowed to walk on the surface of new concreting layers
until they are solidified to bear the weight without distortion.
It must pay attention to avoid any exposal of reinforcing steels out of the
concrete surface. The original structures of concrete exposed to reinforcing
steels shall not be demolished or damaged by the vibration.
The concreting in any structure or part shall be carried out continuously
without interruption. In case that beams and plates are an integral part of
structures, they shall be concreted in the same phase.
*Concrete maintenance.

The Contractor shall take precautions to ensure that the temperature of
concrete structures is less than 20°C during the concreting and maintenance.
In hot weather, measures shall be applied to reduce the concrete
temperature and dehydration rate by appropriate maintenance methods; paying
attention to the cooling of mixing water before use, production and treatment
methods.
All newly-placed concrete shall be maintained, and this maintenance shall
be commenced immediately after finishing the concreting and maintaining for at
least 7 days. The purpose of maintenance is to ensure the moisture of concrete.
17 | P a g e


The Contractor's maintenance methods shall be approved by the
Employer. The Contractor shall apply the following maintenance methods.
10. Construction and erection of main sewers
- Determining the central lines of sewers, locations of manholes
- Installing temporary fences, safety equipment
- Locating the excavation works
- Executing the road works
- Removing the surface layers of roads
- Executing the reinforcement
- Excavating
- Repairing manholes by manual
- Driving cajuput piles
- Executing sand layers
- Executing culverts and joints
- Filling sand and compacting
- Completing and handing over the site, acceptance;
In each construction phase, the site organization and equipment for the
construction shall be arranged according to main equipment and the

mobilization of human resources for that phase.
11. Construction and erection of uPCV conduits
- Executing road bases
- Executing ditch canals for placing culverts
- Laying sand of conduits and installing uPVC conduits;
- Implementing the connection and welding of conduits.
- Testing pressures, excavation and filing sand;
- Constructing and returning the site and acceptance;
12. Construction of manholes
- Determining the central lines of manholes
- Erecting temporary fences, safety equipment
- Locating the excavation works
- Executing the road works
- Removing the surface layers of roads
- Executing the reinforcement
- Excavating
- Repairing manholes by manual
- Driving cajuput piles
- Executing sand layers
- Executing the bottom concrete plates
- Executing bottom concrete, wall concrete and concrete covers
- Completing and handing over the site, acceptance;
18 | P a g e


13. Progress guarantee
The construction progress guarantee is a very important work. Prior to
the construction, the Contractor shall contact with the local power and water
suppliers to provide water and power for the construction of works.
The construction equipment is arranged fully and in accordance with

construction methods. The construction site is close to other sites of the
Company, so that in case of failure of any equipment, the Contractor shall use
other equipment to guarantee the construction progress. In addition, the
Contractor shall also provide some additional equipment.
The Contractor shall arrange qualified and experienced human resources
in accordance with the arrangement.
The construction equipment is repaired and maintained regularly to avoid
any damage during the construction process.
However, the most important thing is to ensure the orders, combination
and proper succession between the construction progress and work items. The
Contractor shall cooperate with Employer, Engineers and other construction
units to ensure the most effective construction. Technical requirements and
general construction progress are guaranteed. The construction in specific orders
is the most reasonable solution.
Based on the volume and requirements of the progress, all forces
including machinery, equipment and personnel at the site shall be arranged
properly to perform the bid package in the most effective ways.
Based on the current status of the construction area.
Based on the weather and climate conditions at the construction site.
Based on construction capacity and experience, the Contractor shall
prepare construction schedules for the Bid package with the total construction
time from the commencement date to the date of delivery is 18 months.

19 | P a g e


PART 4- DETAILED CONSTRUCTION METHODS
I. Construction methods of reinforced concrete culverts and uPVC conduits
1. Construction procedures
Prior to the construction, the Contractor shall train all technicians and

construction workers regarding to the construction procedures of conduits in an
order as specified in the diagram. Based on the site conditions according to the
organizational diagrams, the Contractor shall disseminate the specific
construction process to each site.
2. Site preparation
* Site preparation
The Contractor shall agree and hand over the site to units who have
underground works in the construction site of the Bid package, and hand over
the site in writing between the parties under the witness of the PMU.
The Contractor shall prepare detailed construction plans and construction
schedules, so that units who have underground works and surrounding people
will acknowledge and then facilitating the construction of culverts in such areas.
The Contractor shall prepare and gather all necessary elements such as
lights, electric cables, equipment, motorcycles etc. for the construction;
Based on construction capacity in the day, the Contractor shall execute the
conduits to avoid any impacts on the traffic and daily life of people in the area.
The execution of conduits and culverts are only carried out with the
approval of the Employer and full of construction permits.
Auxiliary parts are also lifted by turbo-cranes, arranged in trunks, not
thrown and overlap when transporting to the site.
* Determination of central lines for erection of culverts, conduits and
benchmarks
- Determination of central lines
Based on the position of each pile (as marked on the drawings) and based on
delivery documents of the Employer and Contractor, the Contractor shall drive
wooden piles or iron poles to position all piles along the edges in order to
determine the central lines.
Based on such central lines, the Contractor shall locate the benchmarks from
design piles with the distance of 1 benchmarks for every 30 - 40 piles. The
central lines of benchmarks are transferred from other benchmarks as

determined by the leveling instrument and the Contractor is responsible for
preserving such benchmarks during the construction process and serves the
inspection and testing works.
Use white paints to paint asphalt roads or concrete surfaces.
20 | P a g e


- Determination of elevation of ditch canals, bottoms and culverts
The determination of elevation of conduits is important when placing
culverts and conduits and the hydraulic slope. Through many years of
experience, our Company has applied the methods as follows.
+ From the standard elevation according to the design of the Employer, the
Contractor shall transfer the elevation to construction site, determine the
elevation to the construction area and elevation to power poles or other fixed
positions of the local houses on road sides where conduits are constructed, or
other fixed elevation near to the first pile, along to the ditch canals; in wide
space without fixed items, wooden piles are driven with distance of 4x4x50,
elevation distance is <25m to facilitate the construction process.
+ After that leveling machines are used to determine the elevation of ground
for executing the ditch canals, depth and erection of culverts and conduits.
- Benchmarks for inspection
The construction of conduits and culverts is within an areas as same as other
works, therefore the determination of elevation not only minimizes the revision
but also greatly affects the progress of excavation and construction.
Conduits and culverts are divided into many construction areas and executed
at the same time; therefore, it must have many benchmarks subject to the terrain
conditions, the distance of among benchmarks is 50m and 100m for inspection.
Benchmarks are built by concrete or iron piles or in fixed structures, marked
by paints or by concrete with iron nails.
3. Excavation of ditch canals and treatment techniques

* General methods
Prior to executing ditch canals for placing water sewers, the Contractor shall
arrange signs, barriers, lights at night etc. The ditch canals and sewers are
constructed in successive construction method, executing with the length of L =
50m, then inspecting the ditch canals to meet requirements in the Technical
documents.
Works of execution of ditch canals and culverts shall be executed in the
following steps:
* Step 1: Determination of culverts and sewers
- Determining central lines, conduits and marking by paints or limes or
boundary lines.
- Identifying the elevation of each culvert section by theodolite, Electric
tachometers.
* Step 2: Executing ditch canals
21 | P a g e


- At narrow areas of culverts and conduits, that are difficult to access by
motorcycles, the main construction method is by manual. In convenient areas
close to large roads, suitable for the transport of machinery and equipment, the
Contractor shall use excavators with bucket capacity of 1.2m 2, in combination
with manual repair methods.
- For single or double ditch canals with slopes, the Contractor shall execute
ditch canals according to the design drawings and the Bidding documents as
prescribed.
- Execution of vertical ditch canals: The clearance width of ditch canals with
vertical edges shall not less than or exceed 10% of the width of the clearance.
- During the construction, the Contractor shall pump and discharge water to
specified areas to avoid the flooding and obstruction to the traffic systems or any
impacts on the surrounding environment.

* Step 3: Inspection of ditch excavation
- Before erecting the culverts and conduits, it must inspect the slope,
dimensions by the theodolite, Leveling instrument and other special tools. The
sewer bottom must ensure the flat and dry.
- The depth of ditch canals is consistent with the design, slope of conduits
and not exceed 15% of the slope shown in the drawings. All special cases shall
be consulted and approved by the Engineers.
Some permissible tolerances for executing conduits shall be according to
requirements of the Employer.
* Step 4: Backfilling
- Soil used to fill ditch canals must be neatly arranged and not cause any
danger and obstruction to the traffic as well as daily activities of local people.
Excess soil is transported by trucks and covered by canvas to the landfill at the
request of the Employer and competent authorities.
* Step 5: Sand layers
- Filling sand layers with the thickness of 200mm for culverts and conduits
and then using vibrators to compact to the required compaction.
Note: After executing the ditch canals, the Contractor shall place iron sheets
to cover the foundation pits to ensure the traffic safety.
* Acceptance of the execution
After completion of the excavation, the Contractor shall cooperate with the
Employer and Engineer to accept foundation pits to transfer next works; bases
for acceptance are as follows:
+ Approved drawings of ditch execution.
+ Elevation and size of current pits
22 | P a g e


+ Bottom elevation
Compared to regulations on permissible tolerances for acceptance, TCVN 4447-2012 is applied - Earthwork, construction regulations and acceptance and

TCXD-79-1980 - Construction and acceptance of foundation works.
* Treatment of underground works
In areas located underground works as early notified by management
agencies, the Contractor shall survey by manual method to check the elevation
and characteristics of each type of underground works.
After executing areas where underground works are located, the Contractor
shall report specific construction methods and progress to the Employer and
management agencies.
After obtaining approvals of the Employer and management agencies of
underground works, the Contractor shall carry out the construction according to
the methods as approved by the parties.
In locations where cross-section and elevation of underground works cross
over, it is impossible to erect sewers according to the design elevation, the
Contractor shall construct the shoulders subject to the elevation and other
protection standards, these shoulders shall be constructed upward or downward
with joints and supports.
* Treatment of bases and ditch canals for placing culverts and conduits
The construction of culverts and conduits is within production areas of the
local people, so that after completing the construction of culverts and conduits,
the Contractor shall backfill by sand and soil according to design documents and
compacted in each layers in accordance with regulations and procedures.
* The entire excavation pits must be filled and compacted after finishing the
construction to the elevation of the road foundation, excavation soil layers and
handed over to road management unit to ensure the safety for people and traffic
vehicles.
* Lower the water level of ditch canals:
During the process of excavating ditch canals, culverts and conduits, it must
be dry, not flooded or sediment. In routes which have high underground water
level, high water volume, 1 manhole is constructed along to that route every (20
- 30)m. A submersible pump is placed to pump water out of the ditch canals;

hoses of pumps are made from soft grass cloth to facilitate the drainage of ditch
canals and other operations of pumps.
In the case that the underground water level is high with risks of infiltration,
the Contractor shall install permanent pumps for the drainage (installed pipe
side).
23 | P a g e


The pump only stops when the water is discharged completely and the
erection of culverts and conduits is finished.
* Inspection of central lines and elevation of canal bottom
Based on positions of each pole (marked on the drawings) as determined
before the construction;
According to positions marked by white paint in asphalt or concrete areas,
lime is used for rice fields and land edges;
As mentioned above, Leveling instruments are used to determine the
elevation of the ground and canal bottom, compared to the design to ensure the
slope.
The following steps shall be only carried out after the elevation is consistent
with the technical design drawings and approved by the Engineer.
* Equipment used for the ditch execution
- Excavators
- Leveling instrument
- Gravity level
- Water level
- Wooden benchmarks.
- Gasoline-powered rammer.
- Handle vibrator (compacting areas surrounding conduits).
- Concrete cutting machine, concrete drilling machines
- Air compressors, concrete hammers;

4. Installation of pipes and culvert
a. Implementation immediately after installation of pipes and culvert
Theodolite and leveling machine are used to check the pipe reinforcement,
hydraulic slope. Make a Certificate of Final Acceptance with the Employer and
the Engineer before moving to the construction phase.
Clean thoroughly to prevent sediment inside the pipes before installing pipes
and culvert.
After each construction phases of installing pipes and culvert, the ends are
sealed to prevent soil, sand and dirt from entering the pipes and culvert.
b. Equipment for installation
- Theodolite, leveling machine, total station;
- Nivo, excavator, crane machine;
- Tubular;
- Electric welding machine;
- Electric pipe welding machine;
- Pipe end cutting and flattening tool;
24 | P a g e


- Chain hoist from 3,5 to 5 tons;
- Silk cable, Phabo wire;
- Steel hook for pipe;
- Rubber cushion;
- Level;
- Crowbar;
- Wood purlin 12x12 and hoist for alignment;
- Metal cutting and grinding machines;
- Electric winches;
5. Placing pipes and culvert
Pipes and culvert are put into place before connecting pipes;

Pipes and culvert are placed into the ditch by rolling method
Pipes and culverts are slowly lowered into the ditch by means of hoist and
crane machine or excavator.
Prevent any impact which may damage the pipes and culvert.
6. Construction of manholes
* Construction of concrete for manholes
a/ Checking the elevation of lining concrete for foundation, bottom, wall and
manhole cover, checking center of the positioning axis and elevation transmitted
to the lining concrete surface of the manhole.
b/ Checking formwork:
Checking formwork construction method approved.
Location, size, verticality, standing system for stability during construction.
Checking and cleaning formwork and lining concrete.
c/ Concrete
Checking the concrete slump, molding according to regulations.
Check the stop time between spills to ensure the stop time within the
allowed time.
d/ Dismatle and curing of formwork:
- Checking the time of removing formwork in accordance with regulations.
- Checking and supervising concrete curing process after placement.
II. Solutions for dealing with underground works
When receiving the written response of the technical infrastructure
management agency, the contractor will have a demonstration of the location of
the underground works on the construction site drawing. The Contractor will
sign construction supervision contract with the underground works management
unit.
25 | P a g e