Method Statement for Construction of cast-in-situ chambers (Wash out, air release, gate valve chamber, hydrant & water meter chamber)

CONTENTS

1. Scope of Work

• Definitions

• References

• Subcontractors

• Materials

• Plant  & Equipment

• Safety

• Prior Activities

• Procedure

1. Responsibilities

1. Attachments

1. Scope:

1.1	This Method Statement covers the construction of cast-in-situ chambers of the fire and water supply network intended for the wash out, air release valve, gate valve and hydrant elements.

2. Definitions:

2.1	MS: STM Method Statement : Cast-in-situ chambers for fire and water supply networks.
2.2	ITP  Inspection and Testing Plan
2.3	PS-GCMI  Project Specifications-General, Civil and Mechanical Infrastructure
2.5	UG   Underground

 3. References:

3.1	PS-GCMI : Section 401: Concrete (in general)
3.2	PS-GCMI : Clause 401.3 & 401.14 :Steel reinforcement
	Clause 401.7 & 401.12: Concrete Grade & Placing
	Clause 401.9 : Quality control
	Clause 401.13: Formwork
	Clause 401.16: Protection and curing
	Clause 401.20.2: Application of protective coatings
3.3	PS-GCMI : Section 901: Pipework (in general)
3.4	PS-GCMI : Section 901: Clause 901.4: Construction of Pipework and manholes
	Clause 901.4.7: Constructing manholes and chambers
	Clause 901.4.8: External protection of manholes & chambers
	Clause 901.4.9: Internal protection of manholes & chambers
	Clause 901.3.9: Standards of compaction
3.5	Inspection Testing plan 1008-OAJ-ITP-1021 to be submitted for approval
3.6	MS-1004 Dewatering
3.7	MS-1005 Surveying
3.7	MS-1008 Earthwork

4. Subcontractors:

4.1

None.

5.  Products:   

5.1	Concrete class 30/20/S for blinding
5.1	Concrete class 40/20/S for benching and mass concrete.
5.2	Concrete class 50/20/R for structural reinforced concrete
5.3	Steel Reinforcement as per approved bar bending schedule to be submitted
5.4	External Brush-applied tanking membrane and Protection Board: Bitutex FBR and Bituboard Refer to Material submittal 1008-OAJ-FM-MSF-RO / STR 002 or similar approved.
5.5	Approved Epoxy resin coating for concrete internal protection
5.6	Approved Cover & Frame
5.7	Approved GRP ladder
5.8	uPVC pipe dia 50 as drain pipe sleeve
5.9	Geotextile fabric: Type Polyfelt (Refer to material submittal 1008-OAJ-FM-MSF-RO/OTH 001-R0) approved as noted
5.9	Puddle/anchor flanges
5.10	T12 dowel bars 400mm long
5.11	Epoxy resin for fixing dowels

6. Plant & Equipment:

6.1	Dewatering Equipment (If required)
6.2	Excavators, JCB
6.5	Crane (if required).
6.7	Concrete Mix Trucks
6.8	Light Vehicles
6.9	Concrete vibrators
6.10	Surveying Instruments
6.12	Ladders
6.13	Concrete Barricades
6.15	Flagging Tape/Warning Tape
6.16	Concrete Formwork
6.17	Concrete Temp. Gauge
6.18	Slump cone, cube moulds
6.19	Compactor (Plate or Roller)
6.20	Drilling machine

7. Safety

7.1	PS-GCMI Section 102: Clause 102.11, 102.12 and 102.14 General and Preliminary
7.2	PS-GCMI Section 901 Clause 901.3: Trench Excavation and Backfill.
7.3	PS-GCMI Section 100: Clause 100.2 Airport Emergency And Safety
7.4	OAJ JV Safety Manual
7.5	Activity Hazard Analysis to be submitted for approval
7.6	Safety Hazards and Precautions
	a)- Strike UG Services:   Use Locator and/or hand excavation (trial holes)
	b)-Excavation Collapse:   Batter sides to safe slope or provide shoring (as directed by Geotechnical Consultant) and subject to the Engineer’s approval.   Keep vehicles/equipment safely away from excavation edge   Keep spoil at least 2.0 meter away from edge   c)- Fall into excavation:   Provide fencing, guardrails or flagging tape around edges and night lights.   Provide banks man when operating equipment near excavation.   d)-Crane Accidents:   All cranes checked and certified   Operators professional and well experienced   Check load indicator, slings and wire ropes daily   e)- Falling Objects:   Stand clear during lifting operations   Wear hard hats   f)- Equipment & Vehicles:   Use Safety belts   Slow down and obey speed limits   Provide “back-ups” alarms   Provide banks man when operating equipment near excavation.   g)- Confined Space:           Check excavations for snakes and scorpions before entering trenches.   Take precautions against flooding   Develop rescue procedures

8. Prior Activities:

8.1	Calibrate Surveying Instruments.
8.2	Check for Existing Utilities before excavation (Trial Holes).
8.3	Prepare and get approval of Shop Drawings.

8.6	In case of dewatering, proper water discharge away from work area will be provided. Permits will be obtained where needed.

. 9. Procedure:

All activities carried out will comply with the OAJ-JV Inspection Test Plan (1008-OAJ-ITP-1021) which reflects the testing requirements of the Contract and which will be submitted for approval.           

9.1	Prepare the Shop Drawings and submit to the Engineer for approval prior to starting any excavation works. Any obstruction encountered on Site will be reported to the Engineer and will be indicated in a revised shop drawing. A shop drawing will be issued for each type of chamber and will be subject to the Engineer’s approval.
Note:	Only the drawings marked as approved “Issued for Construction” are allowed to be used by the Site Staff.
9.2	Survey will be conducted according to MS-1005
9.3	Dewatering (If required) will be conducted according to MS-1004.
9.4	Excavation will be conducted to the proper formation level according to MS-1008.
Note:	The Engineer’s Inspector will be notified if any areas are over excavated or unsuitable materials are encountered, in which case replacement material will be used.
9.5	The trench formation shall be compacted to 98% MDD.
9.6	The formation level will be to the required lines and grades as detailed in the approved Shop Drawings.
Note:	Formation compaction is a Hold Point and will be confirmed by the Engineer’s Inspector before proceeding with blinding concrete.
	The chamber construction will start after completing the related section of pipeline including the short pieces that would be cast along with the chamber walls as detailed on shop drawings.
9.7	Exact location of the chamber will be determined by the surveyor according to the approved shop drawings.
9.8	Blinding concrete class 30/20/S as shown on drawings related will be undertaken after compaction, construction of any subgrade drainage and the Engineer’s approval is given.
Note:	The blinding concrete is a hold point and levels must be checked and approved by the Engineer’s Inspector before other work proceeds.
9.9	The formwork for the bottom slab will be erected and braced as per clause 401.13 of the specs. Recess for joint sealant application will be allowed through the top of kicker and around the pipe. The kicker height will be 10cm.
9.10	The reinforcement steel already cut and bent according to approved bar bending schedule will be fixed over 60mm approved concrete spacers as per clause 401.14.2 and 401.14.6.
9.11	Levels will be checked to confirm accuracy as per approved shop drawings
Note:	The steel reinforcement is a hold point and must be checked and approved by the Engineer’s Inspector before other work proceeds.
9.12	Once all pre-pour aspects are checked and found acceptable by the Engineer’s Inspectors, concrete grade 50/20/R e will be poured according to clause 401.12 “Placing of concrete” to the levels shown on the shop drawings.
9.13	As soon as is practicable, all concrete shall be cured by the application of approved concrete curing membrane or materials as per clause 401.16.
9.14	Striking of bottom slab sides formwork will occur 12 hours after pouring as per clause 401.13.5 unless otherwise directed by the Engineer.
9.15	Fixing of reinforcement and formwork of the walls will follow the same sequence starting activity 9.9 through 9.11. Where pipes are built through concrete walls puddle/anchor flanges will be provided as per approved shop drawing and securely fixed in a way not to suffer disturbance or movement during the concrete pouring. Level and position will be checked after fixing. Concrete pouring will take place after inspection and approval by the Engineer’s Inspector. Formwork striking will occur 36 hours after concreting if wall height exceeds 1.2meters. Curing will be as detailed in 9.13
Note:	The formwork fixing  is a hold point and must be checked and approved by the Engineer’s Inspector before other work proceeds.
Note:	The wall will be poured in one stage. Pouring heights exceeding 2.5 m will be subject to the Engineer’s approval. Extension will be fitted to the concrete pump hose to reduce the height of pouring and avoid segregation and honeycombing. Utmost care will be taken for well compacting the concrete below the pipe and at acute angles.
9.16	All foreign materials shall be thoroughly cleaned after striking the formwork (Clause 401.13.5). Approved sealant will be applied along the pipe perimeter. Brush-applied tanking membrane will be applied to the walls according to specifications and protection board installed as per clause 401.20 and as per manufacturer’s recommendations.

Backfilling:

9.17	Backfilling will proceed in layers in accordance with MS-1008 and clause 201.3.3 Backfilling to structures will start only after striking the formwork, applying the waterproofing system and after the concrete has gained enough strength to sustain the filling material load and compaction.

9.18	Top slab (Cast-in-situ or pre-cast) will be carried out according to shop drawings to be submitted for approval.
9.19	GRP ladders will be installed after dismantling the shutter for cast-in-situ top slab.
9.20	The chamber will be thoroughly cleaned.
9.21	As per clause 901.4.9 all internal concrete faces will be treated and coated with approved Epoxy coating system of which method statement will be forwarded along with the material submittal.
9.22	Concrete support block will be poured using concrete Grade 40/20/S and as shown on the approved shop drawings. Bottom slab will be drilled and T12 diffused dowel bars 400mm long will be fixed 200mm inside the slab by means of approved epoxy resin material.
9.23	Where benching is required, bottom slabs shall be bush hammered then thoroughly cleaned. Concrete Grade 40/20/S will be applied to the slopes and levels shown on approved shop drawings.

10. Responsibilities:

10.1	The CM will coordinate with SE and ensure that the necessary resources to implement the approved method statement and ITP have been allocated to the task.
10.2	It is the Site Supervisor’s duty to organize the work in a safe manner to ensure that safety and protective equipment are being properly utilized.  He must also assure the method statement procedure is followed and must observe the Hold-points and notify the Engineer for inspection.
10.3	It is the worker’s duty to properly wear the protective equipment provided and obey all safety rules.  They must also perform the work as described in the method statement procedure.
10.4	The SE will ensure that the site preparation activities are conducted according to the approved method statement and all in-situ tests according to the ITP are implemented.
10.5	The ME will ensure that the materials being used are in accordance to the project specifications, the approved method statement and the ITP.