Method Statements For Excavation And Backfilling Works

Method Statements for Test Pile of Access Trestle andCoal Unloading Jetty_The purpose of this Method Statement is to describe the methodology for structural work of Method Statements For Excavation And Backfilling Works and to details out the steps to be taken in meeting the technical requirements of Van Phong 1 thermal power plant project

A 19-Dec-2019 For Approval JH Choi KS Kim ET Kim

OWNER

VAN PHONG POWER COMPANY LIMITED

PROJECT

Van Phong 1 BOT Thermal Power Plant Project

OWNER’S ENGINEER

Pöyry Switzerland Ltd

Status

□Approved

□Approved with Comment

□Not Approved

□Reviewed EPC CONTRACTORS

IHI–TESSC–CTCI–DHI CONSORTIUM

PROJECT DOCUMENT No

VP1-0-L4-C-GEN-10008

REV

A

DOCUMENT TITLE

METHOD STATEMENT FOR EXCAVATION AND BACKFILLING WORKS EPC

Doosan Heavy Industries and Construction

EPC DOCUMENT No

VP1-0-L4-C-GEN-10008

REV

A

For Approval

General comments:

(1) Project specifications and code/

standard applied for earth works indicated

to be listed Noted that code/standard for

underground works, filled & bedding

materials and so on

(2) Over-excavation for rock or soil ground

to be more specific requirement and

acceptance

(3) For deep hole, pit, foundation, please

consider the access to go up and down for

safety issue

(4) Protection slope during construction to

be considered particularly in rain season

Approved

Contractor to revise the correction and resubmit

Revise the correction and resubmit before proceeding

Information acknowledged with no comment

Information acknowledged with comments Note: Approval or comment does not relieve the Contractor of

Discipline:

all obligations covered under contract

Date:

Civil and Structural

08 Jan 2020

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

CONTENTS

1 PREFACE 2

2 MACHINERY & EQUIPMENT 2

3 RESPONSIBILITIES 3

4 PROCEDURE AND SEQUENCE 3

5 QUALITY CONTROL 9

6 ENVIRONMENT, HEALTH AND SAFETY (EHS) 9

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

1.0 PREFACE

The purpose of this Method Statement is to describe the methodology involved in general excavation and backfilling works and to details out the steps to be taken in meeting the technical standards and EHS requirements

• Plant Project: VP1 BOT Thermal Power Plant

• Company/Owner: Van Phong Power company limited(VPCL)

• Contractor: DHI

2.0 MACHINERY & EQUIPMENT

7 Automatic Level with Tripod and Staff Rod

3.0 RESPONSIBILITIES

• It is overall responsibility of Project Manager to organize resources prior to perform construction activities as per project specification in compliance with the quality, schedule & safety requirements

• EHS Manager will ensure in coordination with Site Engineer that all measure/construction taken shall be

maintained till completion of job

• It is the responsibility of Construction Manager/Site Engineer that construction activities are executed according

to the relevant project specification in compliance with the quality, schedule & safety requirements

• DMPP will ensure that all works are performed safely according to the attachment

• The relevant DMPP Supervisor will ensure that the work is carried out in accordance with this method statement and project specification

• The QC Inspector will ensure that the work is executed according to the requirements of quality dossier are

fulfilled

- Definite what the 'General excavation and backfilling' is

- Applicable case of this MS (For example: onshore open excavation and max 3 meter depth or ect.)

- Format in one font

Who is DMPP and what attachment?

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

4.0 PROCEDURE AND SEQUENCE

4.1 Site Clearance

• It has been done before the commencement of any excavation or placing of fill material

4.2 Mobilization

• Prior to entering the working area, all equipment and machinery will be inspected by safety personnel Safety

personnel shall be responsible for preparing and providing relevant documents

• All machineries, equipment and material shall be entering using the designated entrance gate

4.3 Equipment Setting-up

• All material, machineries and equipment shall be located at designated area

• Setting-up of equipment will be done by Supervisor by adhering to all safety measurement and requirement

outline

• Upon completion of set-up, joint inspection will be carried out to satisfy all parties and ensure all relevant

equipment/machineries shall be complied with safety rules and regulation

4.4 Survey

• Prior to the work commencement, construction drawing will be reviewed to check of its latest issuance for

construction and all essential details are given It will be checked that the intermediate dimension agreed with the overall dimension

• The setting-out will be made at the beginning stage of the work by referring to the construction drawing and all

reference points will be made necessary for the entire work This will be acquired and develop method of

checking and cross-checking on all setting-out operations When principal lines and levels haste be set-out, it

would be advised to be the relevant persons

4.5 Layout and Marking

• Layout and marking will be marked using surveying equipment having a valid calibration certificate and will be

verified by QC

4.6 Excavation

4.6.1 Excavation by Mechanical Means

• If required trial holes will be dug with hand tools to confirm the locations of existing services before

carrying out excavation using the excavators to widths, lengths and depths as given in the

specification/drawings

• For foundation excavation, leave the bottom layer of minimum 50mm undisturbed while mechanical

excavation and subsequently remove this layer manually when the blinding concrete is about to be placed

This prevents softening or deterioration of the excavated surface If hard strata appear then jack hammer and breaker can be used

4.6.3 Excavation Concrete foundations, Manholes and Miscellaneous Structures

• Excavation for concrete foundation, concrete valve boxes, manholes and appurtenant structures shall include the work of removing all earth, sand, gravel, quicksand, stone, loose rock, solid rock, clay, shale, cement,

Describe clearly basic requirement of site clearance before each excavation, backfilling

Excavation should be divided by depth so that in each case, can design:

1 Necessary space for manpower working or not

2 Kind of slope and slope protection or shoring system

3 Kind of barricade, distance to edge line

4 Loading distance to edge line

5 Type of excavation equipment

6 De-watering system ect

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

hardpan, boulders and all other materials necessary to be moved in excavating the trench for the pipe and other structures; maintaining the excavation by shoring, bracing and sheeting or well pointing to prevent the sides of the trench from caving in whilst in progress and removing sheeting from the trench after pipe has been laid

• Trench support system shall be suitable for the soil structure, depth of cut, water content of soil, weather conditions, superimposed loads, vibration The method shall be ensuring safety of workers on the trench

• Sloping sides of trench to the angle of repose at which the soil will remain safely at rest

• Shoring trench sides by placing sheeting, timber shores, trench jacks, bracing, piles, or other materials to resist pressures surrounding the excavation

• Trenches shall be of the necessary width for proper laying of pipe Care shall be taken not to over-excavate The bottom of the trenches shall be accurately graded to provide uniform bearing and support for each section of the pipe along the entire length of the barrel of the pipe

• Grading of trenches shall be performed to avoid interference of water and sewer lines with other

underground utilities and structures

• Excavation for manholes, concrete foundations, and similar structures shall be sufficient to leave at least 400mm in the clear between the outer surfaces and the embankment or timber that may be used to hold and protect the banks

• Excess materials shall be hauled away from the construction site or otherwise disposed of on designated disposal area

• TYPICAL FOUNDATION

EXCAVATION PLAN

SECTION A-A

DUMP TRUCK EXCAVATOR

- showing barricades

- drainage trench if any

Rock excavation shall

be included in this

MS or separated sub-mission of MS for rock excavation.

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

4.6.4 Excavation on Underground Service Pipeline

• If required trial holes will be dug with hand tools to confirm the locations of existing services before carrying out excavation using the excavators to widths, lengths and depths as given in the

specification/drawings

• Pipe trenches shall not be opened too far in advance of pipe laying

• Width of the trench shall be minimum of 1M (excavator bucket width) but in any case shall not be less than the outer diameter of the pipe plus 300 mm on either side to allow proper compaction of the side fill material

• Bottom of the trench shall be trimmed to form the pipe bed as per the pipe gradient Where solid rock is encountered at invert level, it shall be removed by breaking with jack hammer

4.6.5 Maintenance of Excavated Area

• Continuously monitor the dimension/level of excavation to avoid over cutting If any accidental over cutting takes place, fill and compact with suitable material to the desired level

• Remove any undesirable material (vegetation, organic soils, etc.) encountered during the excavation Take necessary measures to keep the excavation free from water by dewatering wherever required

• Arrange shoring so that it does not interfere with the progress of work As work proceeds, remove the shoring carefully without causing any damage to the excavation

• If any accidental slips or settlement occurs in the excavated area, properly filled by selected materials

4.6.6 Cutting and Sloping the Sides of Excavation

• Whenever there are chances of sliding, properly slope side of excavation Trim the slopes by hand or be mechanical means to uniform batters Trim any rock or boulders appearing in the face of the slope and remove it altogether if it seems unstable

• If any rock is removed, fill the resulting void with compacted material

• Any overhanging, loosed or unstable material shall be removed

• In cutting where the strata consist of earth overlaying rock which is required to be cut to a slope of 1:2, the face of the rock shall be given its appropriate slope up to the junction of the rock and earth and the latter shall be stripped to form a bench and sloped to the gradient as specified

Min 1,000

1 : n

Pipe

Please input slope protection ratio & angle?

Is there enough for people walking & working space?

What is meaning of properly slope, please describe ratio & angle of slope

Excavation should be divided by depth so that in each case, can design:

1 Necessary space for manpower working or not

2 Kind of slope and slope protection or shoring system

3 Kind of barricade, distance to edge line

4 Loading distance to edge line

5 Type of excavation equipment

6 De-watering system ect

It is a very common

description, do not know what

deep what slope, space for

working, drainage

- showing barricades

- drainage trench if any

- if deep foundation, access path for inspector

is required

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

• In all cuttings, whether in earth or rock, undulations in the general plane of the slope will not be permitted

• The excavation shall be so arranged that the working areas are adequately drained throughout the period of construction

4.6.7 Removal of Rocks

• Should rock be met in the course of excavation, it shall be removed by approved means

• The written consent of the OWNER shall be obtained on occasion DHI wishes to use a method

• The OWNER shall be fully informed by DHI as to the steps and precautionary measures taken to safeguard the surroundings It shall be determined the danger zone likely to be created and ensure that no damage is caused to persons or property on site

4.7 Backfilling 4.7.1 Placing of Fill Material

• Where the concrete protective coating is applicable the area shall be cleaned thoroughly and protective coating shall be applied in accordance with the approved coating specification before backfilling work

• Approved suitable excavated material from the site can be used for backfilling/general filling If the excavated material is of a poor quality, obtain fill material from approved borrow pits or any other source able to provide material as per specifications

• Filling area surface shall be kept free from water, such as materials and debris

• Fill materials shall be placed and spread in uniform horizontal layers across the full area of the foundation without segregation The thickness of each layer after compaction shall not exceed 300 mm from third layer, first and second layer shall not exceed 500mm

• Fill in areas not intended to receive concrete foundations shall be placed and spread in uniform layers not exceeding 300 mm after compaction from third layer, first and second layer shall not exceed 500mm

• Filling operations shall be programmed so as to ensure that the specified compaction is attained throughout

• Fill materials shall be laid, spread and leveled using manpower and compacted by using roller compactor to the required levels

• No person shall be permitted to position or operate machinery in a manner likely to endanger that person or others in vicinity of the excavation area

• Field density test (FDT) shall be carried out randomly on agreed area before proceed to the next excavation site or layer

• Setting out the level again for rechecking the excavation level as stated in the drawings

• Each lift shall be evenly spread and moistened or dried by other means so that the required density will be produced

• Backfilling adjacent to structures shall be placed and compacted uniformly in such manner as to prevent eccentric loading upon or adjacent to the structures Slopes bounding or within areas to be backfilled shall

be stepped or serrated to prevent sliding of the fill

4.8 Compaction and Leveling the Fill

• During compaction, maintain the moisture content of fill material usually +/- percent of overall moisture

This is backfill work after completion

of permanence structure, 500mm layer thickness is not accepted

Filling?

Supplement compaction

requirement on the

surface of excavation pit

Filling material shall comply with Code/ Standard Please make it clear

Rocks or stones larger than 100 mm, shall not be used for fill Place compacted fill in successive horizontal layers of loose material not more than 300 mm thick when compaction is made by rollers or vibrators, and 150 mm when mechanical tamping is required

Field density test shall be carried out once for each layer of compaction area or once for each layer of 400 sq.m.

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

content If required, add clean water to the fill material in order to maintain the necessary moisture content

• Around new (or existing remaining) concrete foundations or other sub structures, do not compact by rolling instead, use mechanical rammers or plate compactors to compact the space in vicinity of concrete structure

• After compaction, level the surface free from undulations using suitable equipment

• Mechanical compaction shall be accomplished by the use of foot rollers, pneumatic tire rollers, vibrating rollers or other mechanical tampers of a size and type necessary to achieve the required degree of

compaction

• The type, size and efficiency of compaction equipment shall be subject to the OWNER approval and shall

be capable of achieving the specified degree of compaction Minimum fill compaction will be as follows:

• The mechanical rammers or plate compactors shall be used to compact the confined space in vicinity of

concrete structure instead of rollers

• After compaction, the surface shall be leveled using suitable equipment

• By using adequate capacity of vibrio-max roller about 6 to 8 passes are ensured to achieve minimum

required compaction on 300mm thick layer from third layer, first and second layer shall not exceed 500mm 4.9 Dewatering

• The DHI shall do all pumping, shall build all drains and do all the work necessary to keep the trench and pipes free from water during the progress of the work

Not accepted

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

• It shall be on proper steps to ensure that all water disposal is done in line with good engineering practices and is compliance with national & local laws, rules and codes

• DP will take the proper steps to ensure that the backfilling works are kept free from water until completion

of works This can be achieved by continually dewatering water from the area to the designated drainage system

• Excavation and removal of the mud will be done by backhoe and dump trucked working simultaneously

• The submerged pumps will be arranged sufficiently so that the excavation and removal of the mud can be preceded with no obstruction

4.10 Protection

• Provide barricades or warning tape with post and restrict access as appropriate to prevent damage to work in place

• DHI shall be responsible for protection of work in place against displacement, damage, or loss until OWNER’s acceptance Any work and subsequently damaged, lost or displaced shall be repaired and replaced to the OWNER’s satisfaction

4.11 Cleaning

• Thoroughly clean, rake, wash, flush or sweep as required to clean adjacent improvements of materials covered as part of this work to submitting for OWNER’s acceptance

• Contractor shall provide all labor, equipment, materials and other items as required to perform clean up as required by the OWNER

• Finish grading of areas affected by this work shall be required as part of clean up

• The roadway including shoulders, slopes, ditches, and borrow pits shall be smoothly trimmed, and shaped

by machinery or other satisfactory methods to the lines, grades and cross-sections as established and shall be

so maintained until accepted Any surplus material not suitable for spreading along the road to widen the existing shoulder or raise the grade shall be disposed of as specified above

4.12 Testing:

• Tests for un-compacted materials shall be in accordance with ASTM/TCVN or equivalent method and tests for compacted materials shall be in accordance with ASTM D/TCVN or equivalent method Each test shall

be executed every 5,000 m3 according to the instruction of the OWNER

4 QUALITY Control

4.6 The Site Inspection and Test Plan (ITP) for this work summarize various characteristics to be checked The concerned Site Engineer/Foreman will be responsible to ensure stage wise compliance for this operation and the Site QA/QC Engineer/Inspector will carry-out quality control checks and report the inspection results

4.7 Codes and Standards All excavation and fill works shall be in accordance with the Contract Part III-2 Exhibit B1 Tech Spec Section 8 ASTM D1557 and 4254 shall be applied as an applicable code for the density test

Relevant TCVN codes shall be applied for material laboratory tests

ASTM D1194 shall be applied for Plate Load Test

ASTM D6938 shall be applied in case Nuclear Density Gauge is used for site density test

AASHTO T27 Standard shall be applied for sieve analysis of material

What is process of disposal?

Please describe detail how to control water before discharge?

What is meaning

of DP?

Please describe how far

barricade will be installed

from the edge of excavation

- Code and standard should be stated at the beginning of the document

- Frequency of testing should be stated in each structure ITP (5000m3 applied for site leveling only)

- State the requirement of field density of both excavation and backfill

Code and standard should be stated at the beginning of the document

VAN PHONG 1 BOT THERMAL POWER PLANT PROJECT

5 ENVIRONMENT, HEALTH AND SAFETY (EHS)

6.1 Responsibilities

• The Safety Manager is responsible for the overall safety of the construction site His responsibilities include site inductions ensuring work permits are valid, accident reports, number of man-hours worked and ensuring all works are carried out in the safest possible manner consistent with good construction practices In case of imminent danger the site supervisor has to stop the work immediately The Safety officer at site is equally responsible from stopping the work in the above case

6.2 Safety

• Personal Protective Equipment (PPE) will be issued to all workers such as safety shoes, hard hat, working gloves, safety goggles, reflective vest and safety harness for workers who will be assigned in elevated places 1.8m and above

• Wearing of the basic PPE will be enforced fully

• All new recruits will undergo proper orientation and safety induction before they could deploy at site for work

• Place necessary warning signs as required

• Provide flickering lights and reflectors while working in the night time

• Where material must be stacked, make sure that they are staked on a firm and level base and in tidy manner

• No waste, debris, toxic chemical, oil grease and etc from excavation and backfilling activities shall be spilled or burned on/in the ground, or discharge into any watercourse These wastes stored in drums/ containers and taken away and disposed of in the approved manner

• Ensure that proper access is provided before entering excavation area

• Always obey speed limits and traffic signs for ingress and egress from the site

• Barricades/Signs will be provided sufficiently and maintained, as precautionary measures during the entire stage of construction, to protect the work and safety of the workmen

• Prior to using any machines/equipment at site, ensure that they will be inspected and certified by qualified person

• Operators and drivers are to be equipped with valid driver's/operator's license or permit from concerned government agency

• Periodic Preventive Maintenance will be made on all equipment and machines

• Lifting equipment as well as its accessories such as sling wire, nylon sling, shackles, chain blocks crane hook and latch will be inspected prior to using

• Any potentially dusty material being transported from work sites will be securely contained Transporting vehicles, etc., will be monitored to prevent overloading and over-filling

• Weight of dump truck containing the excavated material will not be exceeded the limited weight allowed by the nation, local and traffic law

• Ensure all workers and equipment’s working overtime are properly accounted and obtained permit/ approval from DHI EHS Manager prior to carry-on works