9 water transmissionreservoir

Buildings Practice For ProfessionalsConstruction Method Statements

Chapter 9 Water Transmission Scheme Water ReservoirSafety General

1 Refer to Chapter 3, MS 12 & 13, Chapter 4, MS1, Chapter 6 Page1 for general provisions on safety discipline in addition to those included with various method statements on this Chapter

2 Relevant point should be extracted from description in line to requirements on relevant activities

3 It is to be noted that safety standards vary from organization to organization, company to company & client to client

4 Just consideration of economy on project cannot exclusively, be a criterion to avoid or reduce safety measures

5 A minimum level of safety measures installations should be made a ‘must’ for a site supervise to ensure that workforce ‘must’ work safely

6 It is preferable to work with acceptable level of safety rather than loosening lives of workers

Water Transmission SchemeWater Reservoir

Scope/Purpose1 Purpose of this document is to define construction procedures to be adopted for

prosecution of typical reservoirs. 2 Four number reservoirs are to be built at one location. 3 This statement is meant only for general description of procedures for various operations

involved. 4 Other detailed typical statements shall be produced during real execution of works for

each activity, as standard procedures applicable to project. Project duration is 20 months. 5 Sketch referred to is only for indicative purpose without any authenticity. 6 Quantities mentioned are also, just to explain method.7 Period for tanks construction considered 14 months (60 weeks). 8 Two tanks to be constructed simultaneously. 9 Safety & quality procedures to be defined separately on individual basis

Reference Documents 1 Drawings 2 Reference Attached from Vendor’s Formwork (to be included with actual statement)3 G A Walls & Columns Top 50 systems 4 Formwork D 2 Tables5 Specification For Concrete-Reference to be indicated6 Specification For Concrete Reservoirs-Reference to be indicated7 Attachment drawing is just for indicative information. It should be a part of contract

drawings

Design1 Prior to construction of reservoir, all proposed forms shall be designed to meet final

requirement & calculations with drawings submitted for approval.

of 12 2012 Int. P Eng (India) Suraj Singh


Chapter 9 Water Transmission Scheme Water Reservoir2 Construction execution of reservoir RCC structures shall be carried out based on AFC

drawings.

Existing services1 Records shall be checked for possibilities of certain running service. 2 Existing services so located shall be informed to relevant authorities as well as, company

for necessary actions. 3 Trial pits shall also, be excavated to scan whether or not, certain service exists.

Supervision & Control1 Construction manager, Site engineer, construction foreman & charge hands shall control

all activities on site according to relevant job descriptions included on project plan.

Survey Controls1 According to AFC drawings, surveying team shall locate setting out lines, coordinates as

well as, surrounding circulation area for construction purpose. 2 Since, dimension of built up main reservoir are given around 130 M x 100 M, proper

arrangement shall be made to carry out mass excavation works.3 Topographical levels shall be recorded. 4 Site shall be graded to required ground level. All survey documents shall be prepared for

purpose of verification. 5 Around area, guide barricades shall be erected for purpose of locating grids & reference

site levels. 6 Benchmarks shall be established on all corners for purpose of flying and reestablishing

all working locations. 7 Establishment of base corners points as well as, base level benchmark shall be conducted

by licensed land surveyor, whose documents submitted to engineer for approvals & records references.

Safety1 All safety measures shall be taken according to excavation requirement. 2 Warning tapes/ Safety cones shall be provided around defined working area. 3 All safety signboards meant for excavation safety shall be provided. 4 Warning night lights reflectors shall be provided around. 5 Ladders shall be provided for access into working area located not more than 8 m

spacing.6 Pouring platform for people/personnel to work safely shall be constructed. 7 For convenient access of heavy equipment into formation area, ramps shall be provided

from existing or graded level from 2 opposite ends. 8 If so required, dewatering arrangements shall be carried out continuously, until

foundation slab is constructed. 9 Toolbox talks shall be imparted daily for all important operations involved. 10 A safety officer shall inspect works everyday during all concreting activities, form

erection activities etc.



Chapter 9 Water Transmission Scheme Water Reservoir

MaterialsConcrete source

1 Ready mix concrete from an approved supplier shall be used.Rebar fabrication

1 Reinforcing bars shall be fabricated on steel yard located elsewhere on site.2 All fabricated bars shall be tagged according to BBS (Bar Bending Schedule) references

Form fabrication1 Fabrication of plywood forms shall be carried out on site based on specialist formwork

vendor details. 2 Supporting system shall be provided by form vendor based on detailed design approved

by engineer. 3 On site, form works shall be erected according to complying with vendor drawings.4 Scope of vendor formwork system shall be confined to retaining walls, baffle walls,

columns, flat slab.

Procedures/Method for one reservoir construction (sketch # 29/30 indicatively)Summary of activities

1 General activities prior to structural construction2 300 mm compacted granular sub base laying on all areas3 75 mm concrete blinding laying on required area4 layers bituminous membrane application for concrete protection below ground5 50 mm screed to be laid for protecting protection membrane

Structural construction activities1 RCC Elements involved-2 Periphery retaining walls, Base slab, baffle walls, columns with heads, suspended slab,

all components pertinent to inlet & outlet chambers, components of overflow chambers Intermediate suspended slabs & walls, sump elements.

3 Box outs, construction joints, expansion joints, stair structure, Roof up stands

General activities post structural construction1 Filling PVC pipes inserts within walls with approved propriety material.2 Fixing of Manholes covers & frames on roof.3 Roofing & waterproofing standard approved system4 Roof handrails5 External Walls pattern formation.6 1200 mm wide interlocking paving around reservoir construction.

Detailed activities prior to structural constructionExcavation & Sub Grade

1 After clearance from engineer, excavation shall be started using heavy equipments removing excavated material from location, loading excavated material directly into truck & transporting to tip off stock piles or in case material not to be used for filling back purpose, to a designated dumping area.

2 During excavation, dust control measures shall be carried out by conventional means.



Chapter 9 Water Transmission Scheme Water Reservoir3 Excavation shall be carried out approximately, to formation sub grade level only, all

according complying with profile shown on approved drawings. 4 Land Surveyor shall control levels to avoid over excavation. 5 Excavated formation shall be dressed manually as well as, using light rollers & after

formation profile is established, heavy rolling shall be carried out over entire are to reach field compaction to 95 % of dry density.

6 Field compaction test shall be conducted complying to standards & specification requirements. Quality Engineer shall inspect profile for clearance & approval

300 mm thick compacted granular sub base1 1st layer of sub base shall be laid in 200mm thickness to achieve 150 mm compacted, so

that after rolling, compacted thickness in both courses is 300 both courses.2 Thereafter, 2nd course construction shall be carried out. 3 Top profile of sub base shall be given according to details, which indicates a fall 1 in 500. 4 Site samples testing shall be conducted from both layers in conformance to specification

requirement for granular sub base, spread over entire area in 2 layers.

75 mm concrete blinding & mass concrete to requirement1 Blinding shall be done in stages parallel to width of reservoir. 2 Whole blinding shall be divided into 6 to 8 bays each 20/25m wide & 100 m long. 3 One stage quantifies to about 200 cum, which is feasible for a convenient casting. 4 If so required, further formation of baying compartments could be established within

each bay for alternative laying. 5 Low profile strip formwork for controlling sides shall be prepared & fixed. 6 A concrete laying team shall be grouped for purpose, such that concrete received from

transit mixer is immediately, pumped into location & spread using teeth shovel/garden racks, to strip profile level.

7 Proper leveling shall be carried out using wooden float edge by masons. 8 Whole area shall be laid, profiled to true levels & given wooden float after concrete is

ready to receive float. 9 Polythene sheet shall be spread over entire area. 10 Curing shall be carried out for 3 days only. 11 Before laying new concrete at set edge of previous blinding at edge, cement slurry shall

be applied to edge, so that new & old concrete is properly bonded. 12 Mass concrete shall be carried out as shown on approved contract drawings

2 layers bituminous membrane1 At end of curing, surface shall be cleaned of all dust particles, debris, water etc &

inspected. 2 All cracks appearing or certain damaged portion located shall be repaired. 3 According to manufacturer’s instruction, bituminous membrane shall be applied over

blinded surface.

50 mm screed



Chapter 9 Water Transmission Scheme Water Reservoir1 Membrane shall be protected by an application of 50 mm screed layer as soon as,

possible & cured accordingly by repetition of foregoing activities in sequence, but in alternate bays.

Construction of peripheral retaining walls- major elements1 Preparatory works for one corner L shape – 1 set, 4 stages in repetition

(Ref to attached drawing GA walls from vendor)2 Preparatory works for straight walls – 1 set 35 m long, 1 set 30 m long 3 repetitions each

(Ref to attached drawing GA walls from vendor)3 These elements comprise of base slab, shear key & upright RCC structures shear keys not

indicated on sketch but, may be required

Preparatory works for base slab- non propriety formwork1 26 x 20=520 repetitions of each bay2 Each bay comprises of 4 sides as indicated on typical square on sketch3 Site fabricated forms to be used. 4 Bar sides to be prepared for construction joints in horizontal position.5 Fabrication of construction joint water bars to be fabricated.6 Arrangements of reinforcing bars to be made to pass through vertical forms correctly

Preparatory works for columns- propriety formwork1 25x19=475 columns 85 sets, 5/6 repetitions each2 Each column comprises of 4 sides3 Site fabricated forms shall be used to standard designs/or in compliance to vendor’s

designs as suitable(Ref to attached drawing Column top 50 from vendor)

Preparatory works for baffle walls- propriety formwork1 sets, 4 repetitions

Refer to attached sketch & other contract drawings2 Both sides of each wall shall be prepared for forms either from vendor or by site

fabrication

Preparatory works for inlet / outlet chamber as well as, overflow1 1 set, 2 repetitions2 These comprise of excavation, soil improvement, blinding, concrete protection

membrane, screed cover, foundation beams, stubs columns, walls, grade slab, sump walls, base slab, walls, columns, cantilever slabs, suspended slabs including external suspended slabs for connection, stairs, railing, roofing, concrete protection above ground, backfill, external paving etc. all.

Preparatory works for suspended slab - propriety formwork1 1 set, 2 repetitions Flat slab construction

(Ref to attached drawing …. Tables from vendor)



Chapter 9 Water Transmission Scheme Water Reservoir

L shape walls @ corners of reservoir1 Setting out for each L shape wall at corner shall be carried out on screed for base slab

(Toe + Heel) portion. 2 Reinforcing bars shall be placed according to details provided with supported on due

spacers. 3 Chairs shall be provided between top & bottom rebar layers. 4 At end of everyday work, polythene membrane shall be spread over, placed & fixed on

reinforcing bars for protection from humidity. 5 Vertical forms shall be prepared at site using plywood & wooden battens, all in line

approved methods. 6 Arrangement for construction joint shall be made for insertion of approved water bar, so

that lower half of bar is inserted in retaining wall base slab concrete. 7 Retaining wall base slab shall be continuous without any joint. 8 It shall be ensured that set lines of forms are in true alignment & plumb. 9 All vertical sides shall be well supported, so that 1 m high concrete pressure is sustained

by supporting system adequately, without concrete bulging.

After clearance by site engineer, QC inspection shall be conducted & engineer’s approval obtained for pouring concrete.

1 About 600 cum of pour in this programme that may take about 16 hours. 2 Pouring shall be done in 3 layers, so that cold joint is avoided. 3 Two pumps shall be used for this pour. Concrete delivery shall be continuous. 4 Portion of green concrete at wall junction shall be roughened, before concrete is

hardened. 5 Exposed portion of concrete shall be properly finished to defined levels & immediate /

instant as well as, specified duration curing be continuously carried out. 6 Following preparatory works for upper wall portion shall be continued.

Upright wall1 Scaffolding shall be erected on both sides for accessing workers to fix reinforcing bars &

erect formworks for upright wall. 2 Reinforcing bars shall be placed properly in compliance with design details & engineers

approval obtained prior to closure of forms. 3 At end of everyday work, polythene membrane shall be spread over placed & fixed

reinforcing bars for protection from humidity. 4 According to formwork vendor’s design, sides of forms shall be erected & fixed.5 It shall be ensured that erected forms are in true alignment & plumb as well as, outer wall

forms complied truly to designed profile. 6 Anchoring arrangements sleeved in, for tie bolts shall be fastened properly. 7 All supports as shown on details shall be provided. 8 A platform shall be built on top for workers safe access & safe working. 9 Water bar shall be inserted in all vertical positions duly welded, using cross as well as,

Tees wherever, required. 10 Permanent bars shall also, be inserted as shown on vendor’s design.



Chapter 9 Water Transmission Scheme Water Reservoir11 Outer forms shall be checked for correctness of its compliance with design profile, while

vertical forms for verticality as we as, alignment. 12 QC inspection shall be conducted & engineer’s approval obtained.13 Programme shall be charted out for pouring about 250 cum in one go. 14 Concrete pouring chute pipe shall be inserted vertically into prepared works, so that net

drop of concrete is not more than 2 m. 15 Pour shall be carried out in layers not exceeding 450 mm, so that vibrator nozzle

penetrates internally. 16 This pour shall consume about 10 hours. 17 At end of pour, top surface shall be properly floated & either curing compound instantly

sprayed or poured covered with polythene sheet. 18 Side supports shall be struck only after 48 hours.

Base Slab bay / Floor slabs1 Size of bay is 5 m x 5 m, 500 mm thick i.e. 12.5 cum, means total number 26x20=520 bays.2 Preparation for 50 bays shall be done in one go i.e. 600 CUM pour. 3 Construction joints to be prepared around to detail requirement. 4 Preparation of forms to be carried out around in general, keeping in view that it allows

for continuation of reinforcing bars and also, insertion of water bar. 5 At end of everyday work, polythene membrane shall be spread over placed & fixed

reinforcing bars for protection from humidity. 6 Rebar placement to be done continuously to details.7 Reinforcing bars for starter bars shall be placed for baffle walls in correct positions,

wherever defined8 Reinforcing bars for starter bars shall be placed for columns in correct positions,

wherever defined9 Provision of surface water strip shall be made according to details. 10 Provision of rebar chairs for top & bottom reinforcing bars supports shall be made. 11 Proper placement of concrete spacers shall be made. 12 All bars shall be properly bound to avoid some kind of slip or dislocation, even though,

steel fixers shall be available to attend pour to control intact bars positions. 13 Formwork carpenters shall also, be available to control alignment & levels. 14 Two concrete pouring pumps shall be used for pour for 18/20 hours programme.15 Immediately, after finishing of top surface to defined profile, instant curing shall be

carried out. 16 After concrete is set, curing shall be carried out as approved. 17 Repetition of bays shall be done accordingly, to complete all 520 bays. Side supports

shall be struck only after 24 hours.

Straight walls 1 Base Slab preparatory works shall be carried out similarly, as indicated in foregoing L

shape pattern excepting that forms are straight.2 Upright wall3 Each pour is about 120 cum, in which case also, scaffolding shall be erected for accessing

workers to fix reinforcing bars & erect formworks for upright wall.



Chapter 9 Water Transmission Scheme Water Reservoir4 Reinforcing bars shall be placed properly in compliance with design details & engineers


reinforcing bars for protection from humidity. 6 According to formwork vendor’s design, sides of forms shall be fixed. It shall be ensured

that erected forms are in true alignment, profile & plumb. 7 Tie rods sleeved in shall be fastened properly. 8 All supports as shown on details shall be provided. 9 A platform shall be built on top for workers safe access & safe working. 10 Water bar shall be inserted in all vertical positions duly welded, using cross as well as,

Tees wherever required. 11 Permanent bars shall also, be inserted as shown on vendor’s design. QC inspection shall

be conducted & engineer’s approval obtained. 12 Programme shall be charted out for pouring this quantity in one go. 13 Concrete pouring chute pipe shall be inserted into form, so that net drop of concrete is not

more than 2 m. 14 Pour shall be carried out in layers not exceeding 450 mm, so that vibrator nozzles

penetrate internally. 15 This pour shall consume about 5/6 hours. 16 At end of pour, top surface shall be properly wooden floated followed by, either curing

compound instantly sprayed or covered with polythene sheet. 17 Side supports shall be struck only after 48 hours.

Columns 1 About 100 cum in one go for 50 columns. 2 In this case also, Scaffolding shall be erected for accessing preparatory workers to fix

reinforcing bars & erect formworks. 3 Reinforcing bars shall be placed properly in compliance with design details & engineers


reinforcing bars for protection from humidity. 5 According to formwork vendor’s design, sides of forms shall be fixed. 6 It shall be ensured that erected forms are in true alignment & plumb. 7 Fixing arrangements shall be fastened properly. 8 All supports as shown on details shall be provided. 9 A platform shall be built on top for workers safe access & safe working to allow for

comfortable & safe circulatory movement for crew.10 QC inspection shall be conducted & engineer’s approval obtained. 11 Programme shall be charted out for pouring about 100 cum in one go. 12 Concrete pouring chute pipe shall be inserted into form so that net drop of concrete is not

more than 2 m. 13 Pour shall be carried out in layers not exceeding 450 mm, so that vibrator nozzle

penetrates internally. 14 This pour shall consume about 8/10 hours. At end of pour, top surface shall be properly

finished rough, covered with saturated Hessian & polythene sheet. 15 Continuous curing shall be conducted thereafter.



Chapter 9 Water Transmission Scheme Water Reservoir16 Side supports shall be struck only after 48 hours.

Baffle walls 1 Each pour is about 80 cum, in this case also, scaffolding shall be erected for accessing

workers to fix reinforcing bars & erect formworks for upright wall.2 Reinforcing bars shall be placed properly in compliance with design details & engineers


reinforcing bars for protection from humidity. 4 According to formwork vendor’s design, sides of forms shall be fixed. 5 It shall be ensured that erected forms are in true alignment & plumb. 6 Fixing arrangements shall be fastened properly. 7 All supports as shown on details shall be provided. 8 A platform shall be built on top for workers safe access & working to allow for

comfortable & safe circulatory movement for crew. 9 QC inspection shall be conducted & engineer’s approval obtained. 10 Programme shall be charted out for pouring about 80 cum in one go. 11 Concrete pouring chute pipe shall be inserted into form, so that net drop of concrete is not

more than 2 m. 12 Pour shall be carried out in layers not exceeding 450 mm, so that vibrator nozzle

penetrates internally. 13 This pour shall consume about 5 hours. 14 At end of pour, top surface shall be properly wood floated & either curing compound

instantly sprayed or covered with polythene sheet. 15 Side supports shall be struck only after 48 hours.

Inlet chamber1 Base slab of this chamber is at a lower level & 1 m thick. 2 It also, has walls & intermediate cantilever structure to be connected to roof suspended

slab. 3 This shall be separately carried out in two stages.

Outlet chamber1 This has a basement sump in stepped profile. 2 Base slab of this chamber is at a lower level & 1.2 m thick. 3 It also, has grade level suspended slab. 4 This shall be separately carried out in three stages.

Access stairs to roof 2 numbers1 These stair structures are to be constructed on 3 columns on isolated footings.2 Columns have to carry cantilevered steps & one landing3 Stages4 Construction of footings shall be carried out comprehensively according to conventional

trade practices. 5 Construction of columns shall be carried out comprehensively according to conventional

trade practices.



Chapter 9 Water Transmission Scheme Water Reservoir6 Construction of waist slab & steps shall be carried out comprehensively according to

conventional trade practices. 7 Preparatory works shall be similar to as defined in foregoing excavation, blinding,

formwork, steel fixing, pouring etc. 8 All works shall be carried out comprehensively according to conventional trade practices

Suspended Slab 1 Half portion in one go about 1800/2000 cum. 2 This is a flat structure transferring loads on column heads. In one go, half portion of slab

is intended to be poured as shown on drawing. 3 Arrangement of supporting system shall be strictly adhered to vendor’s instructions as

shown on attached vendor’s drawing. 4 Preparation & erection of forms shall be done following all approved details. Rebar

placement shall be done to details & spacers provided accordingly. 5 At end of everyday work, polythene membrane shall be spread over placed & fixed

reinforcing bars for protection from humidity. 6 Location of movement joints shall be prepared, so that 50 mm thick joint filler is fixed in

position correctly as well as, supported to remain so intact during concrete pouring. 7 Forms for up stands shall also, be erected for monolithic pour requirement with slab

concrete, for which fixing arrangements should be made accordingly. 8 All block outs for openings shall be prepared to defined locations & properly anchored to

remain in position.

Following quality checks shall be conducted prior to pouring is commencedSlab alignment

1 Levels2 Profile of column head / drop heads3 Alignment of up stands & verticality4 Re-bars placement as well as, locations & centering5 Proper fixing of concrete spacers6 All inserts or services fixes if so required, shall be placed in & approved.7 It shall be ensured that no rebar is susceptible to any possible displacement any time.8 Certain possibility to correction must exist during pour, in case displacement appears.9 Certification of supporting system by form system vendor engineer10 All access routes shall be properly tagged & certified by safety officer.11 During concrete delivery, slump, temperature, air voids tests etc shall be recorded.

Notes for requirements1 For pour, minimum 2 pumps shall be required for continuous placement of concrete, with

1 pump to remain standby. 2 Keeping a speed of 10 minutes for each truck, 60 cum each hour, 2 pumps shall pour

prepared portion in 10 hours followed by another overlapping 10 hours required for wooden finishing of unformed surface.

3 Instant curing shall be carried out by spraying curing compound over area to control shrinkage cracks.



Chapter 9 Water Transmission Scheme Water Reservoir4 Later, after final profile & finishing surface, polythene layer shall be spread over

saturated hessian to keep wet for at least 10 days continuously.5 Striking of forms shall be carried out only after 8 days. 6 Whole exercise shall be repeated for second half of slab.

Concrete Pour Location of Equipment1 Since, size of reservoir is considerable making it difficult to pour concrete either at base

slab or at suspended slab conveniently, large boom length concrete pumps shall be utilized.

2 Locations to station pumps shall be decided judiciously onsite. 3 Adequate arrangement shall be made to control pump swings & delivering concrete to

locations on base slab & suspended slab.4 Pumps shall be required to be located on all sides requiring relevant arrangements.5 Tower cranes may preferably, be utilized for easy access to central points on area. 6 Tower cranes stationed on all sides could be utilized to assist smooth & efficient shifting

of preparatory materials to locations.7 Mobile cranes also, could be in second preference, be utilized provided these are

available having required boom length at optimum cost.

Reservoir testing1 Structure when completed, according to BS 8007 provisions, water tightness test shall be

conducted to check any leakage. 2 After closing all openings, water shall be filled gradually to required level. 3 Fall in water level shall be monitored regularly at defined intervals according to code

provisions. 4 Loss of water should be within prescribed limits5 During filling of water, filling depth shall not exceed 1 m in a day. 6 Water shall be left for one week or as indicated by specification for absorption &

autogenous healing/restitution. 7 Water loss monitoring shall start only when tank is full to maximum water level &

restitution period is completed.8 Though not necessary in this case since water is in cover, for comparison of loss by

evaporation, a separate small container shall be kept, which indicate loss in level due to weather & fall of reservoir level corrected accordingly to reach net loss in level.

9 After successful completion of water test, water used for test shall be pumped out to other reservoir for testing in sequence.

10 Whatever leakage or defects observed, shall be charted out with engineer regarding repairs or injections &if so required, retesting could be conducted.

Roofing1 After curing is completed, whole surface shall be scabbled properly to expose aggregate

to meet bonding requirement of foam concreting. 2 Surface shall be prepared & all services plinth required be constructed to details. 3 True profile required for drainage shall be prepared for foam concrete over entire area.4 Foam concrete shall be produced on site & laid by specialist roofing subcontractor.



Chapter 9 Water Transmission Scheme Water Reservoir5 All other roofing operations shall be carried out in line / accordingly to procedures

defined on approved method statement. 6 Roof waterproofing shall be tested by flooding with water for 48 hours. 7 Leak detected shall be made good according to agreed procedures.

Other General activities1 Roof handrails shall be fixed to required locations. 2 Adequate arrangements shall be made to keep internal space of reservoir well ventilated

during performing application of concrete protections. 3 All other activities about concrete protection shall be carried out for above ground

concrete on inner as well as, on external surfaces. 4 All operations of backfilling of walls up to formation levels shall be carried out according

to standard approved methods & field samples tested accordingly. 5 Preparation of walkways around shall be carried out for receiving interlocking blocks. 6 Compaction shall be done for formation of walkway area. 7 Works for kerbstone shall be carried out. 8 Laying interlocking blocks shall be carried out to given profile & levels.

Equipment1 Shovel, Excavator, tipper trucks, Roller, Compactor, Tower crane, Mobile crane,

Concrete pumps, Truck mixers as & whenever required, concrete vibrators, centrifugal pumps to boost out water from reservoir etc

Attachment1 Sketches & formwork drawings (not included herewith)


9 water transmissionreservoir

Engineering