1

Guidelines for Public Awareness Campaign

Guideline No. : NWSDB / RWS / GUI / 15

NATIONAL WATER SUPPLY AND DRAINAGE BOARD

Prepared by Third ADB Assisted Water Supply Sanitation Sector Project

December 2008

2

Table of Contents

1 Background 7

1.1 Sustainability in the Project Context 7

2 Construction Phase and Quality Control 9

2.1 Work Contracts and Responsibilities 9

2.2 Organisational Aspects and Observations 10

2.3 Quality Control and Responsibility of Staff 11

3 Quality Control 12

3.1 Purpose of Quality Control and Supervision 12

4 Drawings 14

4.1 As-built Drawings 14

5 Quality Control - Construction Materials 14

5.1 Cement 15

5.2 Sand 15

5.3 Reinforcement bars 16

5.4 Bricks 16

5.5 Granite 16

5.6 Water 17

6 Quality Control - Concrete Works 17

6.1 Properties and Testing of Concrete 18

6.2 Mixing of concrete 19

6.3 Testing of concrete 19

6.4 Concreting under water 22

6.5 Curing of concrete 22

6.6 Removal of formwork 23

6.7 Disinfection of Concrete Structures 24

3

7 Quality Control - Ferrocement Works 25

7.1 Background 25

7.2 Checks - Materials for Ferrocement 25

8 Quality Control - Pipe Works 27

8.1 Transportation and Storage of Pipes 27

8.2 Laying of Pipes 28

8.3 Pressure Testing 28

8.4 Pipeline Disinfection 31

Table of Appendices

Appendix 1 - Checklist for As-Built Drawings

Appendix 2 - Visual Check List: Cement, Sand & Bricks

Appendix 3 - Visual Checklist: Granite and Water

Appendix 4 - Checklist: Pipe transportation and storage; Pipe laying

Appendix 5 - Checklist: Construction Materials for Ferro-cement structures

Appendix 6 - Certificate of Pressure Testing

Appendix 7 - Table of Permissible Water Losses

Appendix 8 - Checklist of Switchboards in Pump Houses etc.

4

List of Abbreviations and Units Technical dia. diameter ext. external int. internal ND Nominal Diameter ID Internal Diameter OD Outside Diameter fl. Flanged BS British Standard SLS Sri Lanka Standards ISO International Standard Organisation DI Ductile Iron CI Cast Iron GI Galvanised Iron Al Aluminium Upvc Unplasticized PolyVinyl Chloride PN10 Nominal pressure (bars) AV Air Valve WO Wash Out CV Control Valve GV Gate Valve VC Valve Chamber ISO International Standards Organisation Min. Minimum Max. Maximum GL Ground Level WL Water Level TWL Top Water Level IL Invert Level Drg. Drawing RC Reinforced Concrete PCC PreCast Concrete ST Storage Tank No. Number M metre mm millimetre

5

km kilometre m² square metre

m3

cubic metre in. inch ft. foot kg. kilogram lb pound gall imperial gallon l litre m-H

2O meters of water column

s, sec second min. minute

h, hr. hour

d day

l/c/d litre per capita per day

rpm revolutions per minute

kW kilo watt

Rs Sri Lanka Rupee

USD US Dollar

Units: The following metric/SI-units should be used, intermediate units such as cm should not be used: Length km, m or mm

Area km2, m² or mm²

Volume m3

or litres

Flow l/sec. m3/sec

Demand l/s, l/day or m3/day

Pressure Bars Head m-H

2O

Hydraulic gradient m per km Diameter mm NB - ND for plastic pipes is always ext. dia. For all other pipes it is int. dia.

6

Conversion Units A few of the more common factors are given below for easy reference.

To convert To Multiply by To convert

To Multiply by

inches mm 25.4 ft3/s l/s 28.3

feet m 0.3048 ft3/s m

3/d

ay

2447

yards m 0.9144 l/s m3/d

ay

86.4

miles km 1.609 m.g.d. l/s 52.6 sq. miles km

2 2.589 million gallons per day

sq. inch mm2 645 p.s.i m-

H2O

0.7032

cu. ft. litres 28.3 pounds per sq. inch gallons litres 4.546 Atmospher

e m-H

2O

10.332

acre-feet m 1234 Bar m-H

2O

10.197

Hp kW 0.746 MPa

(106N/m²)

m-H

2O

101.97

lb kg 0.4536 kg/cm2 m-

H2O

10.0

The above gallon refers to imperial gallon. American literature use US gallon. One imperial gallon = 1.201 US gallon

7

1 Background 1.1 Sustainability in the Project Context During the first two years of the ADB assisted Third Water Supply & Sanitation (Sector) Project considerable focus and efforts was given by the entire project organisation to ensure future sustainability of village as well as small towns' schemes. The project policies and strategies were all designed to ensure maximum involvement of the potential beneficiaries so that ownership feelings were established, and so that the commitment towards future sustainable management of the schemes could reach a level where the completed schemes could be handed over to motivated, trained and competent CBOs. The phases the rural water supply sub-projects are all going through are: Public awareness

Social mobilisation & hygiene education

Participatory planning and design

Construction and

Consolidation

Each of the carefully designed phases of the project, right from public aware-ness campaigns to the construction and consolidation phases are equally important for future sustainability of the schemes. Basically, full sustainability comprises three major elements: Financial sustainability

Institutional sustainability

Technical sustainability

8

Figure 1: Concept of total scheme sustainability If one element of sustainability fails, it may be assumed that the total prospects for future sustainability may be seriously jeopardised and that the scheme may not survive as intended and planned for during the project preparation period. Institutional sustainability is achieved only if the managing organisation is able and willing to take up the challenge to manage the scheme in a safe and responsible manner that also provides the consumers with an adequate and agreeable service level. The financial sustainability is achieved if the scheme generates sufficient in-come to cover expenditure for management, operation and maintenance and replacement. Therefore, the tariff setting is critical for financial sustainability. Also, on the expenditure side, expenses for operational staff and chemicals, power charges etc. should be monitored carefully and budgets prepared to en-sure that at the very least the above aspects are covered.

9

Technical sustainability depends on among others: Quality of construction works carried out

Quality of operation and maintenance,

2 Construction Phase and Quality Control As the first phases (mobilisation and design) of the sub-project cycle for batch 1 of sub-projects are now over the project’s attention has logically shifted to-wards the construction phase. The importance of quality control in the context of sustainability has been outlined above. Quality control is here defined as the control and compliance of quality of executed works with the specifications as given in the relevant tender documents. Quality control is most commonly carried out through introduction of a number of measures that intend to check various elements of preparations for construction as well as measures that are aimed at check of materials and quality of workmanship during the construction. An important part of the quality control is carried out through on-site supervision. 2.1 Work Contracts and Responsibilities This document applies to quality control and supervision of works under two types of contracts as follows: 1 Contracts signed with the CBOs for the construction of non-complex components of village

water supply schemes, such as ferro-cement structures, pipe laying, culvert crossings etc. These contracts are awarded at the district level by signing a simple agreement and the contractor (CBO) should carry out construction according to ICTAD1 conditions/specifications of contract. The CBOs will be trained by the Project and assisted by the POs to handle such construction works to achieve accepted quality.

2 Contracts signed with registered contractors at district level / NWS&DB Head office for the

construction of major / complex components of water supply schemes, such as water towers, R/F structures and supply and installation of pumps etc. These contracts are to be implemented according to the conditions / specifications given in the signed contract documents.

1 ICTAD (Institute for Construction Training and Development, Sri Lanka)

2 Field visit by Team Leader of COWI in February 2002

10

2.2 Organisational Aspects and Observations The structure of the project’s organisation allows for wide delegation of responsibility for supervision through the involvement of Partner Organisations (POs). The quality control measures are implemented at various levels in the organisation: Quality Control by Technical Officers of the POs

Quality Control by the Engineering Assistants of the DIUs

Quality Control by the Engineers (Consolidation) of PIUs

Quality Control by the Senior Engineers of PIUs

Based on field interviews2 the main organisational limitations for adequate supervision of works appear to be logistical limitations in relation to the geo-graphical area to be covered, combined with the time to be assigned for other works, often administrative duties. In December 2000 a draft report titled ‘Procedures and Guidelines for Supervision of Construction Contracts, Rural Water Supply Schemes’ was issued by PMU. Interviews with staff in February 2002 revealed that only few staff had read the report/guidelines. Consequently, the checklists included as annexes to the draft guidelines were only used to a limited extent in the project organisa-tion. This document contains a number of checklists that can be used by the project staff for the purpose of streamlining the documentation of quality control per-formed at site. But it must be stressed that all supervision and quality control performed in connection with the construction works must be documented.

11

2.3 Quality Control and Responsibility of Staff While the various types of construction works require quality control to ensure a reasonable standard of work it is also important that the various levels of the project organisation are aware of their roles and responsibilities during the construction phase. Only when responsibility is clear can the methods for the various ways and means of quality control be established. In the project organisation, the various levels and officers all have their role to play, as described in the various project guidelines. While the guidelines may provide significant detail during the project preparation and design stages, the guidelines issued so far do not, to sufficient detail, provide enough practical advise on how to carry our the actual quality control. Therefore, the staff functions in relation to the different stages of construction works, is presented be-low. Based on that delegation of responsibility a more practical guide to quality control will be presented. Table 2.1: Responsibilities of staff - CBO Contracts

Staff Preparation for construction work

Supervision of construction work

Testing of materials and work

TO of PO X X X EA, DIU X X Eng. (Con.), PIU (X) X Sen. Eng., PIU (X) District Manager, PIU (X)

Table 2.2: Responsibilities of staff - Contracts with Registered Contractors

Staff Preparation for construction work

Supervision of construction work

Testing of mate-rials and work

TO of PO X X EA, DIU X X X Eng. (Con.), PIU (X) Sen. Eng., PIU X X (X) District Manager, PIU X (X)

X = responsible (X) = As required/Occasional

12

3 Quality Control 3.1 Purpose of Quality Control and Supervision The purpose of quality control is to ensure that construction works conform to the specifications. The specifications often refer to BS (British Standards), SLS (Sri Lanka Standards), ISO or similar standards. It may not be expected that e.g. CBOs as contractors would know these standards. But the supervisors/facilitators of the project, including the Pradeshiya Sabah Technical Officer and the PO assigned to help the CBOs should know the most important standards. This document is based on a number of standards, both BS, SLS and ISO, whereas the details of how to carry out various aspects of water supply supervision and quality control to some extent are based on ICTAD specifications for Water Supply, Sewerage and Storm Water Drainage Works. There may be deviations described where such deviation have been deemed necessary to reflect developments in materials and technologies since the issue of the ICTAD document. However, with the substantial problems related to the practical supervision it may be feared that only a fraction of the standards are actually known and that many construction works may never be checked or tested properly. This makes it impossible for the project to certify that the works are constructed in accor-dance with specifications and the project, at all levels, remains open for criticism in the event of immediate or later operational problems. Such problems are often difficult and expensive to rectify and the easy solution for the CBOs may be to accept poor performance/leakage etc. Such compromises will in the longer term most likely affect sustainability. Realizing the impracticalities involved with 100 % control and supervision of works it is never-the-less of significant importance that a minimum number of checks and tests that conform to certain standards are actually carried out in the field. In this section the quality control aspects for materials, concrete, pipes etc. are presented in brief and the quality control is suggested to cover these aspects a minimum. A number of checks and tests have been recommended and these form the basis of the quality control formats presented in the Appendices. The related standards have often not been included as the guideline is thought to be as practical as possible. The following framework for quality control of construction works in rural water supply facilities may apply:

13

Table 3.1: Framework for Testing (Quality Control) Tests areas Village water supply Small towns water

supply Materials, Visual checks Yes Yes Pre-concrete casting checks Yes (RC structures and

ferrocement) Yes (RC structures and ferrocement)

Slump test Elevated structures & water retaining structures

All concrete works

Test cubes No Yes Curing and formwork re-moval checks Yes Yes

Waterproofing All water retaining structures

All water retaining structures

Pipe trenches, depth and width Yes Yes

Pipe storage Yes Yes Simple Pressure testing – transmission mains Yes No

Standardised Pressure Test-ing - TMs No Yes

Simple Pressure testing – distribution system All gravity schemes < 100 connections

No

Standardised Pressure test-ing – distribution system

All pumping schemes and gravity schemes with > 100 connections

Yes

Pumps & switchboards Supplier to test on site Supplier to test on site

14

4 Drawings 4.1 As-built Drawings The basis for the quality control performed in the course of the construction phase is the design drawings prepared during the design phase. The drawings are also called as-built drawings because they reflect how the concerned structure or component of a scheme was constructed/built. The as-built drawings shall be drawn with due consideration to the applicable standards for such drawings and be issued in A-formats, i.e. A-0, A-1, A-2, A-3 or A-4. Other formats are not allowed. While the design drawings to the greatest extent shall be followed during construction, circumstances may require minor changes to or deviations from the drawings. Such circumstances are mainly of practical character and must re-main minor. Changes to reinforcement of concrete structures, overall measurements such as thickness of slabs etc are not permitted for any reason without a total revision of the structural aspects of the design. When a construction has been completed and changes or adjustments from the original design drawings have been made, however minor, these must be re-corded and included in a revision of the design drawings to fully reflect all aspects of the construction. This also applies to intakes, pipe networks, water mains, pump houses, electrical & mechanical installations, ferrocement structures etc. Checklist for as-built drawings is provided in Appendix 1.

3 'Rapid' types of cement achieve design strength in 7 days

5 Quality Control - Construction Materials The materials commonly used in construction of structures under the rural component of the project are as follows: Cement

Sand

Tor-steel/Mild steel

Granite

Bricks

15

Water The quality requirements for each of the given materials are provided below. Checklists for visual checks of selected materials are provided in Appendix 2 and 3. 5.1 Cement ‘Portland’ cement, named so because of its resemblance when hardened to ‘Portland Stone’ found near Dorset in England, mixes easily with water to form a hardened mass. Concrete made with Portland cement takes 28 days to achieve its design strength3. ‘Portland’ cement must be manufactured according to BS 12 and this should be indicated on the cement bag – visual check. In addition all cement used shall be low alkali cement, containing less than 0.6% alkali (expressed as Na20 + 0.658 k20). Cement shall be delivered in sealed manufacturer’s branded bags or barrels, each consignment accompanied by the manufacturer’s test certificate. Damaged bags or barrels and any cement the Engineer considers unsatisfactory shall be rejected. All rejected cement bags including those which have become affected by damp conditions is to be removed from site within 48 hours - visual check. If there are hardened cement pieces, the bag should be rejected and carried away from site. Use of other types of cement is only permitted if given in the specifications – visual check of name. The cement bags should be properly stored, also at site. The bags should preferably be kept in a shed or in-doors until the time of use and as a minimum covered effectively with plastic to prevent exposure to humidity - visual check. Cement stored on site shall be protected from the weather and raised from the ground. Cement shall be used in the order in which it is delivered.

Cement temperature shall not exceed 60o C when used.

5.2 Sand Sand used for construction (concrete works, plastering or brick-laying) should be free from foreign matters and when unloading sand at site care should be taken to place sand on a plastic sheet or tarpaulin to prevent mixing with organic substances. Sand for concrete shall not contain more than 5% voided shells (as determined by direct visual separation), river sand should be used. If the supervisor suspects that beach sand is used such observation should be informed to relevant superior officer.

16

Clay, silt and dust shall not exceed 3% by weight. An analysis must be made if the supervisor is in doubt. The maximum permitted concentration of chlorides and sulphates expressed as percentage by weight of dry sand are 0.10% (as acid soluble Cl- ) and 0.4% (as acid soluble SO2) respectively. The sand should be covered until use to ensure uniform water content – visual check. The grain size should be between 2mm – 5mm. A visual check could be made to ascertain this. The sand should be stored in a clean place – visual check Should be free from any chemicals – visual check 5.3 Reinforcement bars Reinforced steel used for construction should conform to following standards Mild steel - SLS 26 (1968) Tor-steel - BS 4449 (1978) It is the obligation of the contractor to produce necessary certificates from the manufacturer, if asked by the supervisor. If the supervisor is in doubt of the quality of the steel, such a certificate should be asked for. Bending reinforcement should be done according to the design drawings. Storage should be done in a proper way to avoid corrosion, although this may often be difficult. 5.4 Bricks Bricks used for construction should follow below guidelines: be of a proper shape without twisting or cracks – visual check

random drop-test from 4 feet

standard size of 225mm(L) x 112mm(B) x 75mm(H) should be maintained – visual check

all faces should be rectangular and of rough surface – visual check

uniformly burnt colour –visual check

free of any foreign matter – visual check

17

absorption of water after immersing in water for 24 hours should not exceed 12% - 18% of its weight – random test

weight of a brick should be between 2 – 2.7 kg – random test

The bricks should be submerged in water for a period of not less than 30 minutes immediately prior to the bricks being used. 5.5 Granite Granite used in concrete works should be free of dirt and mud – visual check Size of stones given in the design should be used (e.g.: 12mm, 20mm, 25mm) – visual check Should be of sharp edged (not rounded) and contain less than 10 % weathered rock – visual check 5.6 Water Water must be free of oil, dirt, mud or chemicals. Only clean water should be used in the construction Sea water must not be used at any time. Any suspicion or confirmation of sea water being used for construction works requires immediate instructions from the supervision to stop work. 6 Quality Control - Concrete Works Plain concrete is made by mixing cement, fine aggregate, coarse aggregate, water and sometimes admixtures. When reinforcing steel in placed in the forms and wet concrete mix is placed around it, the final solidified mass becomes reinforced concrete. The strength of concrete depends on many factors: notably the proportion of the ingredients and the conditions of temperature and moisture under which it is placed and cured. Different types of concrete mixes are normally used in Sri Lanka and their uses are given below: Table 6.1: Concrete mixes and use

Mix Use 1:2:4 (20) Slabs, beams, columns etc. 1:3:6 (20) Screed concrete 1:1.5:3 (20) Water retaining structures

18

6.1 Properties and Testing of Concrete There are different grades of concrete, such as Grade 20, Grade 25 etc. These grades indicate the

specified compressive strength achieved by concrete after 28 days in N/mm2.

It should be noted that concrete made with Portland cement requires, under normal circumstances, 14 days to obtain adequate strength so that the forms can be removed. The supervisor must emphasis this point to the contractor. Concrete is a material whose strength and other properties are not precisely predictable and test cubes from a mix could easily provide significant variations. Therefore, mixes should in principle be designed to achieve an average compressive strength greater than the specified value. However, in practical terms it would probably be impossible to talk about such detailed mix design for rural concrete construction works. It is, never-the-less, of significant importance to determine whether the concrete achieves the specified compressive strength because the design of the relevant structure depends on this. A small safety factor of e.g. 0.2 may be eliminated by a mix of less compressive strength than the specified value. Appropriate testing of concrete mix would entail a more comprehensive testing programme to determine the average compressive strength, a programme that would be impossible to implement. However, a number of basic precautions and tests can provide a reasonable basis for determination of the quality of the concrete as well as determination of the achieved compressive concrete strength (seen as a random sample, which in itself offers limited guarantee and carries no statistical value). In order to achieve the specified strength of the concrete, following precautions should be observed Materials used should be of proper standards – see materials section.

Mix should contain correct quantities specified in the design. This point is of extreme

importance to achieve the minimum required strength of the concrete. It is absolutely vital that the mix design is followed (cement, sand, stones). If the specifications indicate a 1:2:4 mix such mix must be followed. The mix ratio in terms of volume may be used. Care should be taken to ascertain that all containers are filled equally during mixing - visual check

The water-cement ratio (w/c) is the primary and critical factor for the concrete to achieve the

required strength and it also determines the workability of the concrete. The water-cement ratio is always given in weight. A given mix with w/c ratio of 0.45 may produce a concrete with a

compressive strength of 35 N/mm2, while a w/c of 0.6 produces a compressive strength of less

than 24 N/mm2. If a specific w/c ration is given in the specifications this ratio must be

followed. More details are provided in section 6.3

19

The workability of concrete is measured by a ‘slump test’. More details are given in section 6.3

Mixing and placing concrete as specified (including vibration) – visual check

Curing of concrete – please refer section 6.5

Removal of shuttering and props only after recommended period – random check – please refer

to section 6.6 Checklists to be used in connection with the preparation and execution of larger concrete

works are provided in Appendix 13 to the main document. 6.2 Mixing of concrete There are two ways of mixing concrete in a work site, namely (a) hand mixing (b) machine mixing. In order to reach the expected quality of concrete, it is always recommended to use machine mixing of concrete. Hand mixing should be allowed only for screed concrete or for small reinforced concrete parts of a construction pro-vided there are facilities for proper compaction/vibration of concrete. 6.3 Testing of concrete When substantial quantities of concrete are involved in the construction of structures (concrete storage tanks, water towers etc.), it is necessary to carry out tests to control the quality of concrete. Some of the commonly used concrete tests are mentioned below. Concrete cube test The characteristic compressive strength of concrete on which the structural de-sign is based is that 28-day cube strength below which not more than 5% of the test results may be expected to fall. Compliance with the specified characteristic strength should generally be judged by tests made on cubes at an age of 28 days. In order to get an idea of the quality of the concrete sooner, compressive strength test at 7 days may be used to test compliance with the specified characteristic strength. For this purpose the 7 days strength may be taken to be 2/3 of the 28 day cube strength. The rate of sampling shall generally be as given below unless other-wise decided by the officer in-charge.

20

One sample shall be taken from any one batch selected randomly to represent an average volume

of not more than 20 m3, 20 batches or ¼ of the total quantity of concrete under consideration for

testing whichever is the lesser volume, but not at a rate less than 1 sample per day per Grade. Each cube shall be made from a single sample taken from a randomly selected batch of concrete. The samples shall be taken at the point of discharge from the mixer or in the case of ready mixed concrete, at a point of discharge from the delivery vehicle. Specified characteristic strength for concrete cubes of different Grades are given below. Table 6.2: Concrete Mix and charateristics

Specified mix Grade

designation

Specified characteristic

strength

N/mm2

28 days compressive strength

(N/mm2)

Average of any group of 4 consecutive test cubes shall be

greater than AND

Individual test result

greater than

1:3:6 10 10 13 8.5 1:2:4 20 20 27 17 1:1.5:3 25 25 33 21 1:1:2 30 30 40 26

Slump test for concrete The concrete shall be of such consistency as will suit the method of placement and compaction. The quantity of water shall be regulated by carrying out regular slump tests for each mix using one bag of 50-kg cement. The mould shall consist of a metal frustum of cone having the following internal dimensions: Bottom diameter 20 cm

Top diameter 10 cm

Height 30 cm

The mould shall be of a metal other than Brass and Aluminium of at least 1.6 mm thickness. The top and bottom shall be open and at right angles to the axis of the cone. The mould shall have a smooth internal surface.

21

It shall be provided with suitable foot pieces and handles to facilitate lifting it from the moulded concrete test specimen in a vertical direction as required by the test. A mould provided with a suitable guide attachment may be used. The tamping rod shall be of steel or other suitable material, 16mm in diameter, 600mm long and rounded at one end. Procedure : The internal surface of the mould shall be thoroughly cleaned and free from superfluous moisture and any set concrete before commencing the test. The mould shall be placed on a smooth, horizontal rigid and non absorbent surface, such as a levelled metal plate. The operator shall hold the mould firmly in place while it is being filled with the test specimen of concrete. The mould shall be filled in four layers, each approximately one quarter of the height of the mould. Each layer shall be tamped with twenty five strokes of the rounded end of the tamping rod. The strokes shall be distributed in a uniform manner over the cross section of the mould and for the second and subsequent layers shall penetrate into the under lying layer. The bottom layer shall be tamped through out its depth. After the top layer has been rodded the concrete shall be struck off level with trowel or the tamping rod , so that the mould is exactly filled. Any mortar that may leak out between the mould and the base plate shall be cleaned away. The mould shall be removed from the concrete immediately after filling or raising it slowly and carefully in a vertical direction. The moulded concrete shall then be allowed to subside and the slump shall be measured immediately by determining the difference between the height of the mould and that of the highest point of specimen. The above operation shall be carried out at a place free from vibration or shock, and within a period of two minutes after sampling. The slump shall be recorded in terms of mm of subsidence of the specimen during the test. Any slump specimen which collapses or shears off laterally, gives incorrect result. If this occurs, the test shall be repeated with another sample. The slump test shall not be used for very dry mixes as the results obtained are not accurate. Table 6.3: Slump Values for Concrete

Work Slump (in mm) Vibrator used Vibrator not used

Mass concrete in R.C.C foundations and retain-ing walls

10 – 25 80

Beams, slabs and columns 25 – 40 50 – 100 Thin R.C.C. sections or sections with congested steel

40 – 50 125 - 150

22

6.4 Concreting under water General precautions In general placement of concrete under water should be avoided whenever possible because of the practical difficulties involved. Special care should always be taken to avoid that the concrete is affected by water turbulence. Concreting in running water should not be made under any circumstances as most of the concrete is likely to be washed away. In order to keep the place of concreting free of water the flowing or stagnant water present in the surrounding environment must be diverted by placing a plastic film over the surface of the working place or by lowering the water table. If there is only shallow water over a solid base the placing of concrete shall start from the dry areas and move in the direction of the water which will gradually be displaced with only limited intermixing. Concreting in deep water Concreting in deep water requires special attention to skills and quality of execution of the concreting. Special measures should be taken to prevent intermixing of concrete and water at the contact surfaces. This can be done by using a richer mix or by increasing the design thickness of slab by 50 mm. A vertical chute/tremie may be used to place concrete at the bottom. The chute should not be taken out of the water until the concreting is completely over. The purpose is to avoid letting water into the concrete. Therefore the chute should be a large diameter pipe etc. through which water cannot enter the concrete stream. The chute must have a funnel shape at the top end and a removable plug at the bottom end ('go-devil'). In this type of concreting works concreting operations must not be suspended or interrupted until the pouring of concrete is fully over and the chute shall al-ways be kept full with concrete and the flow rate shall be determined by the static head of the concrete. No attempt to vibrate or puddle concrete under wa-ter should be made. The less the concrete under water is disturbed the better. Special attention should be made towards segregation of concrete during the transport of concrete through the vertical chute. 6.5 Curing of concrete After the placed concrete has begun to harden – i.e. about 24 hours after its laying, the curing shall be done by keeping the concrete damp with moist gunny bags, wet straw, sand or any method except water under pressure. Curing shall be done for a minimum of 7 days. Curing of slabs may be effectively carried out by covering the slab with water up to 2-4 cm for a period of 7 days.

23

6.6 Removal of formwork The formwork shall be so removed as not to cause any damage to concrete due to shock or vibration. If formwork has not been properly oiled/greased before placement of the concrete removal of formwork may cause damage to the surface of the concrete. Formwork shall normally be stripped in the following order: Shutters to vertical faces e.g. side of columns, beams and walls

Shutters forming underside (soffits) to roof and floor slabs

Shutters forming underside (soffits) of beams and girders

The removal of the formwork for larger structures shall be planned and a definite scheme of operation worked out to the satisfaction of the officer in-charge. Time of removal of formwork In no circumstances shall forms be struck until the concrete reaches a strength of at least twice the stress to which the concrete may be subjected at the time of strike. Where possible the formwork shall be left for as long as possible as it would assist curing. Forms shall be eased out carefully in order to prevent the load being transferred suddenly to the partly hardened concrete. The period that shall elapse after the concrete has been poured, before easing and removal of formwork are given in the table below. Table 6.4.: Minimum Period for Removing Formwork

Part of structure Period for ordinary Portland cement with-out admixtures

Sides of foundations, columns, beams and walls 24 hours

Undersides of slabs of up to 4.5 m span 7 days Undersides of slabs of above 4.5 m span and undersides of beams and arches up to 6 m span

14 days

Undersides of beams and arches over 6 m span and up to 9 m span

21 days

24

6.7 Disinfection of Concrete Structures The disinfection of tanks and water retaining structures should be carried out in the following sequence:

1. All debris inside the tank should be removed and the floor should be swept twice to remove all loose dirt on the floor, walls roof etc.

2. All inside surfaces should be flushed with clean water to wash away dirt and dust 3. The cleaning should be followed by spraying of chlorine on all surfaces, including roof,

starting with the roof, then walls and finally the floor. The chlorine solution should contain 200 mg/l Chlorine, which equals approximately 1.6 kg bleaching powder dissolved in 1000 litres of water. The spray solution should be in contact for min. 30 minutes.

4. The structure should be filled with water and the Chlorine contents should be adjusted to 10

mg/l and the tanks should remain filled for 24 hours 5. After 24 hours the Chlorine contents of the water must be determined and the following

action taken:

If the chlorine content is < 5 mg/l more chlorine should be added up to 10 mg/l and leave for 24 hours, then test again. Follow this procedure until the Chlorine content of the water is > 5 mg/l.

If the chlorine content is > 5 mg/l the water should be kept in the tank for

another 3 days to dissolve alkalinity of the concrete structure

6. At the end of the procedure water should be drained out in such a manner that the drainage does not harm the environment or creates erosion of any kind.

7. The tank is then again filled with water containing 2 mg/l Chlorine and should be kept full

for 24 hours. If the water is free from smells after 24 hours the tank is ready for use. If the water gives of smell follow the procedure from step no. 5

25

7 Quality Control - Ferrocement Works 7.1 Background The use of ferrocement is recommended mainly in thin elements, sandwich type elements and similar constructions. Ferrocement can be utilised in combination with conventional reinforced concrete as well as pre-stressed concrete. If used in combination with these other types of concrete particular attention shall be given to the design of the connection between the different materials. In the event that ferrocement is designed and used pre-stressed similar to pre-stressed concrete it should be noted that ferrocement is unable to take more than low to moderate pre-stresses. In general reference is made to Ferrocement Model Code (IFS 10-01) of IFS Committee no. 10, International Ferrocement Society, Asian Institute of Technology. The use of ferrocement in rural water supply schemes is mainly relevant for ground level tanks, elevated tanks or treatment plant components with very limited water turbulence at any given point. It should be stressed that only standardized designs must be used for ferrocement. NWSDB has developed sev-eral very creative and useful designs that are available on request. Although it is realised that quality control in rural water supply schemes may sometime be problematic due to low resources it should be noted that strict quality control is necessary for structural ferrocement elements. There are a number of basic requirements to the use of ferrocement that will be listed here. They are all equally important and should receive due attention during construction. 7.2 Checks - Materials for Ferrocement In the following section the various materials used for ferrocement have been mentioned along with the checks to be applied. Wire Mesh Normally, the same type of wire mesh is used in ferrocement constructions but different types are allowed provided they are all either galvanized or non-galvanized. This should be checked before application of mortar. Steel bars, wires and strands used as skeletal reinforcement should comply with standards (SLS; BS; ISO etc). Cement Standard Portland, Rapid Cement or Super Rapid Cement can be used for ferrocement structures. The quality aspects for cement used for normal structures apply, ref. section 5.1 Sand

26

Sand for ferrocement structures should be clean, inert, free of organic matter and other deleterious substances and contain a minimum proportion of silt and clay. Maximum grain size is 2 mm, preferably 1 mm, to easier obtain a workable high-density mortar. Aggregates reacting with the alkalis in cement should be avoided. If there are reactive aggregates tests in accordance with ASTM C 227-81 should be carried out. Water The mixing water should be fresh, clean and potable. The water should be relatively free from organic matters such as silt and clay, oil, sugar, chloride and acidic material. The pH-value of water should be between 7 and 8 to minimise the reduction in the pH of the mortar slurry. Salt water must not be used under any circumstances. Chlorinated water can be used. Admixtures In order to reduce water content, increase strength and increase water tightness high-range water reducing admixtures (super plasticizers) can be used. For water retaining structures the admixture will make it easier to keep the water-cement ratio below 0.4. However, it may be possible to achieve this without admixtures also. Any cracks must be kept as narrow and fine as possible. Waterproofing coating may also be applied. Retarders may be used in large ferrocement plastering works in hot climates. Mix proportioning The mix ranges recommended for ferrocement are: Sand-cement ratio by weight: 1.5 - 2.5

Water - cement ratio (w/c) by weight: 0.35 - 0.5; for water retaining structures w/c < 0.4

Slump value of mix < 50 mm

The higher the sand content, the higher the required water content to maintain the same workability. Shrinkage is generally not a problem because of the high proportion of reinforcement and low w/c ratio. Mix quantities should always be given by weight in the recipe and care should be taken to ensure proper weighing when mixing. The mix must attain 25 MPa (28 days) for test cylinders of 75 x 150 mm. If test cubes are used the strength should not be less than 30 MPa. In case of water retaining structures increased strength up to 70 MPa is desirable. A basic checklist is provided in Appendix 5.

27

8 Quality Control - Pipe Works The pipes of any water supply scheme need to be laid with sufficient care and attention to details to minimise leaks and pipe bursts once the system becomes pressurized. Constant loss of water will affect the financial viability of especially pumping schemes and at the same time affect the service level offered to the consumers. A number of precautions can be taken to increase the quality of pipe works: 8.1 Transportation and Storage of Pipes The following precautions should be taken when transporting and storing uPVC pipes as well as other pipe materials such as GI and DI pipes: Pipes should not be allowed to hang outside the vehicle while transporting – visual check

Unloading of pipes from the vehicle should be done by two people holding from two ends of

each pipe – visual check Under no circumstances the pipes should be dropped from vehicle for unloading purposes –

visual check Storage of pipes should be done in such a way that no direct sun light falls on pipes (storage

area has to be covered) – visual check Stacking of number of layers of pipes should be in accordance with the manufacturer’s

recommendations Pipes should always be placed on supports/rafters- visual check

When it comes to GI pipes the following additional points should be observed: The threaded ends of G.I pipes should be protected from corrosion and damage by applying a

coat of grease and fixing an end cap of plastic or other suitable material – visual check Should be stored on supports – visual check

28

Basic checklists are provided in Appendix 4. 8.2 Laying of Pipes When pipes are being laid the supervisor should be observe the following points: Depth and the width of pipe trenches as per drawings – measure depth

Back filling materials as per specifications – visual check

Road reinstatement to the standards of the relevant authority - check

Pipes and fittings to be of required standards – check with specifications and design drawings

Preparation of as built drawings to give location of pipe lines

Backfilling should not take place until pressure testing has been done, although there is a tradition to cover the pipes to a moderate degree, to keep them in place during pressure testing, and leave the joints and saddle connections open for observation for leaks. Also the end-points should be left open for installation of pressure testing equipment and end-valve. Checklists are provided in Appendix 4. 8.3 Pressure Testing 8.3.1 Preparations for pressure testing In general, pressure testing will appear to be a considerable and time consuming exercise. However, with a bit of planning and organisation the pressure testing can be carried out with minimum of resources. Normally, the pressure testing remains the responsibility of the contractor and the work involved should have been included in the price for laying pipes. The main problem normally encountered when pressure testing of rural schems takes place is that there is no water for pressure testing or that filling the lines require extraordinary efforts. This happens mainly because the implementation of the piped village schemes takes place on ad-hoc basis, i.e. the pipe laying normally takes place as and when the pipes are on site and when the trenches have been dug. There is often little logical work planning that ensures gradual completion of the scheme from one end to the other.

29

As far as possible the work plan should try to take into account the completion of scheme components in the order given: Intake - pump house - transmission main(s) - tower(s) - distribution mains - distribution network with connections 4 The ICTAD formula for permissible water losses has been found impractical.

If the completion of components follows this simple order there will always be water available for pressure testing, especially if the schemes are fed by gravity. In case of pumping schemes factors such as availability of pumps and electricity connection may delay the operational ability of the scheme. The alternative to this is to carry water by bowser to the section to be tested. The preparations also involve the availability of a pressure testing machine. The machine can be either manually operated or electrically operated. If the pressure testing is to be carried out in a smooth and rational manner it is equally important that a trained crew to operate the machine is available. The crew should also know how to cap the pipes to take the heavy load of the pressure inside the pipes. Generally, the quality of the executed pipe works must be documented through pressure tests according to BS standards4. The maximum length of test sections should be limited to 500 m for distribution mains and 1,000 m for transmission mains. The line shall be prepared for testing by closing valves when available, or by placing temporary bulkheads in the pipe and filling the line slowly with water. The pressure testing shall take place at 1.5 x the design working pressure in the specific section of the line, i.e. NOT the max working pressure e.g. PN 16. 8.3.2 Simple Pressure Testing This procedure is not in accordance with recognised standards and should only be used when the correct testing procedure is very difficult or impossible to carry out. The procedure only applies to village water supply schemes. The line is filled gradually with water from another line or from a bowser/tanker. Make sure no air pockets are present inside the line. Flush thoroughly to eliminate air pockets. Air valves installed at the line ends should be kept open while filling water. The line is sealed and kept filled with water for 24 hours. Towards the end of the 24 hour period, all exposed joints, fittings, valves, hydrants and couplings shall be examined for leaks. If leaks are found they shall be repaired at the con-tractor's own expense. If pipes are cracked a new pipe section shall be inserted. The line shall then be refilled and all bulkheads, joints and connections (if

30

any) shall be examined for leaks. This procedure continues until all leaks have been identified and repaired. 8.3.3 Standardised Pressure Testing The line is filled gradually with water from another line or from a bowser/tanker. Make sure no air pockets are present inside the line. Flush thoroughly to eliminate air pockets. Air valves installed at the line ends should be kept open while filling water. The line is sealed and kept filled with water for 24 hours. Towards the end of the 24 hour period, all exposed joints, fittings, valves, hydrants and couplings shall be examined for leaks. If leaks are found they shall be repaired at the con-tractor's own expense. After 24 hours the pressure is increased to the test pressure, additional water may need to be pumped into the line. After the test pressure (1.5 x design working pressure) has been achieved no further pumping is allowed. After 4 hours the pressure is recorded and the required quantity of water to pump into the line to achieve the test pressure is recorded. The permissible water losses can be calculated based on the following formula: Q = 0.0375 x (( D1 x L1)/1000)+((D2 x L2)/1000) etc x H/24 x (P x 1.5) Where D1 is the internal diameter of the first pipe segment, L1 is the length of the first pipe segment, H is the testing time in hours and P is the testing pres-sure in Bar. As a guideline, a pressure drop > 2 % of initial pressure indicates leakage that needs to be attended to. Also, the quantity of water to add to maintain the test pressure after the 2 hours shall be recorded. The tables provided in Appendix 7 indicate permissible water losses for uPVC pipes for both type 600 and type 1000 for 4 hours of testing. Special attention and caution should be given to the fitting of end caps of the tested line. In connection with the testing a very significant pressure is applied to the end caps. The following table indicate the range of force on the end caps: Table 8.1: Load at end cap during pressure testing

Pipe dia. 75 mm 90 mm 110 mm 160 mm 200 mm Load at 13.5 bar 596 kg 860 kg 1282 kg 2714 kg 4241 kg

Load at 9 bar 398 kg 573 kg 833 kg 1810 kg 2827 kg

A checklist for pressure testing, that can also be used as certificate of testing is provided in Appendix 6.

31

8.4 Pipeline Disinfection The internal surfaces of all pipelines and pipe work including all equipment incorporated in a pipeline or pipe work through which water will pass shall be disinfected after they have been cleansed to the satisfaction of the Supervisor. 8.4.1 Disinfection Process Disinfection shall be effected by filling the pipeline with water heavily dosed with chlorine, and shall be carried out when filling the pipeline with water for carrying out the hydraulic test on completion. Alternative methods may be adopted with the approval of the PS. The level of chlorine dosing shall be such as to make available 50 mg/l of free chlorine throughout the pipeline. The water, heavily dosed with chlorine, shall stand in the pipeline for a period of 24 hours or for such longer period as the Engineer shall require and all valves in the system shall be operated at least once during this period. At the termination of the required period, chlorine residual tests shall be taken at the end of the pipeline farthest from the point of injection and the test shall be repeated if necessary until the residual is not less than 10 mg/l. The contractor shall obtain the PS's approval to the method to be adopted for disposing of the chlorinated water and the time when such disposal shall take place on completion of disinfection.

32

Appendix 1 - Checklist for As-Built Drawings Checklist for As-Built Drawings PS NAME: _____________________________ GND NAME: ___________________________ MIS CODE NO.: ________________________ CONTRACT NO.: _______________________ One form per Scheme Yes No

1. All concrete works completed

2. All levels on drawings checked and registered after completion

3. Location of all civil works marked after completion

4. Foundations for mech. equipment checked and OK

5. Levels and location of all pipe works recorded after completion

6. Valve chambers and manholes recorded after completion

7. Office, storage and control structures marked after completion

8. External works checked and marked after completion

9. Drawing of all the above enclosed (compulsary) Responsible authority: ___________________________ ______________________________ _________ Supervisor (TO of PO) CBO Representative Date Certified by: __________________________ ____________________ NWSDB Representative Date

33

Appendix 2 - Visual Check List: Cement, Sand & Bricks

34

Appendix 3 - Visual Checklist: Granite and Water

35

Appendix 4 - Checklist: Pipe transportation and storage; Pipe laying

36

Appendix 5 - Checklist: Construction Materials for Ferro-cement structures

Construction of Ferrocement Structures Checklist for Cement Motar Mixing

OK

Not OK

1 Check cement is OK 2 Check water is OK 3 Mix recipe by weight 4 Water – Cement ratio 0.35 - 0.5 5 Slump max 50 mm 6 Sand – cement ratio by weight 1.5 – 2.5

37

Appendix 6 - Certificate of Pressure Testing

38

Appendix 7 - Table of Permissible Water Losses

39

Appendix 8 - Checklist of Switchboards in Pump Houses etc.

40