Manual for Water Facilities

GOK /UNICEF PROGRAMME OF COOPERATION 2008 - 2013KENYA WASH PROGRAMME

MANUAL FOR WATER FACILITIES

The United Nations Childrens Fund Kenya Country Office, Water and Environmental Sanitation P. O. Box 44145, 00100, Nairobi, Kenya. Tel: 254 207622192, Fax: 254 20622764 Email: [email protected]

August 2008

GoK/UNICEF Programme of Cooperation 2008 2013 Programme

GoK UNICEF Kenya WASH

TABLE OF CONTENTSABBREVIATIONS.......................................................................................5 1.0 INTRODUCTION...................................................................................6

Deliverables......................................................................................................................................62.0 GENERAL DESCPRIPTION APPLICABLE TO ALL STANDARD PROCEDURES. 6

2.1 Procurement of Contractors .......................................................................................................62.1.1 General Terms........................................................................................................................................6 2.1.2 Preamble to Bills of Quantities .............................................................................................................6 2.1.3 Contents of the Bills of Quantities ........................................................................................................7 2.14 Drawings ................................................................................................................................................7 DESCRIPTION OF WATER FACILITIES .........................................................7

Water Facilities.................................................................................................................................73.1.1 Borehole.................................................................................................................................................7 3.1.2 Shallow Well..........................................................................................................................................7 3.1.3 Sub-surface/Sand Storage Dam..............................................................................................................7 3.1.4 Water Pans.............................................................................................................................................8 3.1.5 Roof Catchment ....................................................................................................................................8 3.1.7 Rock Catchment ....................................................................................................................................8 3.1.8 Summary of Water Facilities .................................................................................................................8 4.0 STANDARD PROCEDURES FOR WATER FACILITIES.................................9

4.1 Technical Procedures for Boreholes ..........................................................................................94.1.1 Drilling Technique.................................................................................................................................9 4.1.2 Well Design...........................................................................................................................................9 4.1.3 Casing and Screens................................................................................................................................9 4.1.4 Gravel Pack............................................................................................................................................9 4.1.5 Well Construction..................................................................................................................................9 4.1.6 Well Development ................................................................................................................................9 4.1.7 Well Testing...........................................................................................................................................9

4.2 Bills of Quantities for Boreholes................................................................................................94.2.1 Boreholes with Electric Pump and Various Depths................................................................................9 5.0 TECHNICAL PROCEDURE FOR SHALLOW WELLS...................................10

Drawings for Boreholes .................................................................................................................10 5.1 Description of Shallow Wells...................................................................................................105.1.1 Dug Wells ...........................................................................................................................................10 5.1.2 Hand-Drilled Wells .............................................................................................................................10 5.1.3 Mechanical Well Drilling ...................................................................................................................10

5.2 Dimensions of Shallow wells...................................................................................................10 5.3 Various Procedures for Hand Dug Wells.................................................................................10 5.2 Bills of Quantities for Shallow wells .....................................................................................11 5.3 Drawings for Shallow Wells ...................................................................................................116.0 TECHNICAL PROCEDURE FOR SUB-SURFACE/SAND STORAGE DAM........12

7.0 TECHNICAL PROCEDURES FOR WATER PANS.......................................21

6.1 Bills of Quantities for Sub surface/sand Dams........................................................................12 6.2 Rubble Masonry Sand Dam with Tap/Gate Valve ..................................................................13 15 6.3 Rubble Masonry Sand Dam with Storage tank .......................................................................16 6.4 Gabion Sand Dam with Storage tank .....................................................................................19 6.5 Drawings for Subsurface/Sand Dams.......................................................................................20 21 7.1 Bills of Quantities for Water Pans............................................................................................21 7.2 Drawings for Water Pans.........................................................................................................21 8.1 Parameters................................................................................................................................228.1.1 Runoff Coefficients..............................................................................................................................22Technical Manual for Water Facilities 3



8.1.2 Roof Catchments..................................................................................................................................22 8.1.4 Selection of Tank Size ........................................................................................................................22

9.0 ROCK CATCHMENT ............................................................................26

8.2. Rainwater Harvesting..............................................................................................................22 8.3 Tank Design ............................................................................................................................22 8.4 Bills of Quantities for Storage Tanks ......................................................................................23 8.5 Drawings for Roof Catchments................................................................................................25 9.1 Bills of Quantities for Rock Catchment...................................................................................26 9.2 Drawings for Rock Catchment.................................................................................................27SPRING PROTECTION.......................................................................27

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10.1 Methods of Spring Protection.................................................................................................27 10.2 Typical Spring Flow Rates.....................................................................................................27 10.3 Stages in Spring Protection ...................................................................................................27 10.4 Spring Protection Drawings...................................................................................................27 11.1 Introduction............................................................................................................................28 11.2 Sources...................................................................................................................................28 11.3 Main pipeline..........................................................................................................................28 11.4 Storage and Break-Pressure Tanks.........................................................................................28 11.5 Distribution Pipelines and Tap Stands...................................................................................28 12.1 Hand Pumps...........................................................................................................................2912.1.1 Main Principle of Hand Pumps..........................................................................................................29 12.1.2 Range of lift.......................................................................................................................................29 12.1.3 Choice of Pumps................................................................................................................................29 12.1.4 Performances of Hand Pumps............................................................................................................29 12.1.5 Hand Pumps Installation Details.......................................................................................................30 12.1.6 Siting of the Well...............................................................................................................................30 12.1.7 Fencing of Water Source....................................................................................................................30

12.3 Solar Pumps............................................................................................................................3112.3.1 Comparison of Solar Pumps with Generator Pumps..........................................................................31

12.4 Pumps for Boreholes with Electricity................................................................................3112.4.1 Example of Submersible Pumps for Boreholes with Electricity.........................................................31

12.5 Play Pumps.............................................................................................................................3212.5.1 Operation of the Play Pump...............................................................................................................32 12.5.2 Availability of Play Pumps................................................................................................................32

12.6 Wind Pumps...........................................................................................................................3212.6.1 Technical Information........................................................................................................................32 12.6.2 Factors Affection Sustainability of Wind pump Technology:............................................................32

REFERENCES..........................................................................................36 ............................................37Technical Manual for Water Facilities 4

WATER FILTRATION ................................................................................................................33 Introduction ...................................................................................................................................33 Sand Filters.....................................................................................................................................33 Boiling of Drinking Water ...........................................................................................................33 Activated Carbon (AC) Water Filters...........................................................................................33 Ultraviolet (UV) Light ...................................................................................................................34 Water Distillation (Water Distillers)..............................................................................................34 How Distillers Works.....................................................................................................................34 Disadvantages of distillers..............................................................................................................35 Reverse Osmosis...........................................................................................................................35 How Reverse Osmosis Works .......................................................................................................35 Advantages of reverse osmosis method ........................................................................................35 What does an RO System cost?......................................................................................................36 Summary........................................................................................................................................36



ABBREVIATIONS The following abbreviations and acronyms have been used in this report:UNICEF TOR GOK MWI BoQ United Nations Children Fund Terms of Reference Government of Kenya Ministry of Water and Irrigation Bill of Quantities

Technical Manual for Water Facilities

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1.0 INTRODUCTION This manual is prepared for the purposes of complementing the already existing guidelines/ know- how and gives detailed information and technical procedures of implementation of the water projects for GoK/UNICEF programme of cooperation. Subject to the GoK/UNICEF procurement procedures the content will form an integral part of documents for inviting bids for construction of the facilities. It is important to note these are standard details that are formulated following international codes of design together with some innovations to attempt to suit specific cases. The standards can be localised depending on the location of the water project, geological conditions, terrain, human population, livestock population, level of development of the area, capital etc. At the point of implementation, there would be need for professional guidance especially to modify the where necessary and to supervise works during construction. The standard documents contained in this report are for; boreholes, shallows wells, water pans, sub surface dams, sand storage dams, roof and rock catchments. The details for each of the options are presented in the following sequence; Standard technical description: Bills of Quantities: Drawings: Deliverables The report is presented in two bound hard copies of, a soft copy and a power point presentation of the outputs that will be made to Ministry of Water and Irrigation, Ministry of Health, Ministry of Education, UNICEF, other stakeholders and Government of Netherlands representatives at the end of assignment. The outputs are specified in the ToR and are expected to be submitted within the time frames proposed. There will be need however for the client to comment on the draft before the final report is submitted. 2.0 GENERAL DESCPRIPTION APPLICABLE TO ALL STANDARD PROCEDURES 2.1 2.1.1 Procurement of Contractors Technical information that may be useful for decision making during implementation. To guide pricing while bidding Presentation of technical details for various water facilities.

2.1.2

Preamble to Bills of Quantities 1. 2. The Bill of Quantities shall be read in conjunction with the Instructions to Bidders, General and Special Conditions of Contract, Technical Specifications, and Drawings. The quantities given in the Bill of Quantities are estimated and provisional, and are given to provide a common basis for bidding. The basis of payment will be the actual quantities of work ordered and carried out, as measured by the Contractor and verified by the Engineer and valued at the rates and prices bid in the priced Bill of Quantities, where applicable, and otherwise at such rates and prices as the Engineer may fix within the terms of the Contract. The rates and prices bid in the priced Bill of Quantities shall, except insofar as it is otherwise provided under the Contract, include all Constructional Plant, labour, supervision, materials, erection, maintenance, insurance, profit, taxes, and duties, together with all general risks, liabilities, and obligations set out or implied in the Contract. A rate or price shall be entered against each item in the priced Bill of Quantities, whether quantities are stated or not. The cost of Items against which the Contractor has failed to enter a rate or price shall be deemed to be covered by other rates and prices entered in the Bill of Quantities. The whole cost of complying with the provisions of the Contract shall be included in the Items provided in the priced Bill of Quantities, and where no Items are provided, the cost shall be deemed to be distributed among the rates and prices entered for the related Items of Work. General directions and descriptions of work and materials are not necessarily repeated nor summarized in the Bill of Quantities. References to the relevant sections of the contract documentation shall be made before entering prices against each item in the priced Bill of Quantities. Provisional Sums included and so designated in the Bill of Quantities shall be expended in whole or in part at the direction and discretion of the Engineer in accordance with Sub-Clause 52.4 and Clause 58 of Part I of the Conditions of Contract. The method of measurement of completed work for payment shall be in accordance with [insert the name of a standard reference guide, or full details of the methods to be used]. Errors will be corrected by the Employer for any arithmetic errors in computation or summation as follows: (a) (b) where there is a discrepancy between amounts in figures and in words, the amount in words will govern; and where there is a discrepancy between the unit rate and the total amount derived from the multiplication of the unit price and the quantity, the unit rate as quoted will govern, unless in the opinion of the Employer, there is an obviously gross misplacement of the decimal point in the unit price, in which event the total amount as quoted will govern and the unit rate will be corrected.

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8. 9.

General Terms

Selection of contractors shall be made in accordance with the Kenya Public Procurement and Disposal Act 2005 or as will be outlined in the Programme documents for the GoK/UNICEF Programme of cooperation. Contractors will be evaluated on the basis of their bid prices and their technical capacity. They should be invited for the tender opening and be informed on the outcome of the tenders by writing. Conditions of contract shall be based on provisions of the contract signed by both contractor and the or as per other procedures as it may advised at the time of execution of these works. Where applicable the implementation may be by the Community Based Organisation through the facilitation of the programmes technical staff. Measurement of all works executed by contractors will comply with the Civil Engineering Standard Methods of Measurements and the Bills of Quantities and will always be verified by the responsible engineer on site

10.

Rock is defined as all materials which, in the opinion of the Engineer, require blasting, or the use of metal wedges and sledgehammers, or the use of compressed air drilling for their removal, and which cannot be extracted by ripping with a tractor of at least 150 brake hp with a single, rear-mounted, heavyduty ripper.


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2.1.3

Contents of the Bills of Quantities

DESCRIPTION OF WATER FACILITIES Water Facilities The technological options for development of the water points for rural communities and livestock consumption includes of; boreholes, shallow wells, water pans, sub surface dams, sand storage dams, roof and rock catchments. The choice of technological options depends on various factors as follows;

The Bills of Quantities will consist of the following;

General Proposed works Provisional sums Contingencies Taxes Total Cost Drawings

2.14

2.14.1 Scale The scales used are provided below and they conform to ISO 5455 1979 (E). 1: 2 1: 20 1: 200 1: 5 1: 50 1: 500 1: 10 1: 100 1: 1000

Suitability of site: - The suitability of site depends on space occupied by the development, ease of development, ability to abstract water and water quality. Reliability of option: - Permanence of water supply and potential of the source of water to meet demand across the year. Quality of water: - The cleanliness, salinity levels, against the uses for the water need to be checked. Quality of yield:-The ability of water source to yield comparatively more water needs to be considered. Cost of development: - The cost of construction of water facilities also determines the type of technological options used. For example, a borehole will be developed where the beneficial community will be able to cater for cost of operation and maintenance.

A detailed unit cost model for various technological options has been developed by the Ministry of Water and Irrigation and is available for use at the planning, and monitoring and evaluation stages of implementation cycle to determine the investment and operational costs for different water supply technologies. 3.1.1 Borehole Table 3.1 Borehole Yield Class Yield Class 1 2 3 4 5 6 7 Yield (m3/hr) 0 2.5 2.5 3.5 3.5 4.5 4.5 5.5 5.5 6.5 6.5 7.5 7.5

2.1.4.2 Standard and Type of Drawings The drawings will be presented in A3 (450 x 297mm). However, if a drawing is being used during construction it should be printed in paper size A1 (840 x 594mm). The title block used is attached in the appendix 3. The following conditions must be fulfilled for a drawing to be classified as standard. These includes:a) b) c) d) Design shall be possible to use for several different projects. Design shall be of high professional standard Design shall comply with recommendations of Kenya Bureau of Standards or with the standards used by the Ministry. SI units shall be used exclusively. The description of SI system is given below:Design shall be sufficiently detailed to allow construction work to be carried out without additional design work.

The groundwater is exploited by use of borehole and its suitability is determined by the groundwater in the underlying rocks. This defines the existence of shallow, medium or deep groundwater in the sub-surface. According to water act, it is a requirement that a borehole is drilled not less than 0.8 km radius from an existing one. The borehole yield varies from 0.641 - 26.776 m3/hr. Depending on the yield of the borehole, they are classified as shown in the table 3.1 below:3.1.2 Shallow Well

In area where shallow aquifers are encountered at depths less than 30 metres, shallow wells are recommended. In areas where there are shallow riverbeds saturated with sands, especially where there is a perennial sub-surface flow, shallow wells are the best technological options. 3.1.3 Sub-surface/Sand Storage Dam

The sub-surface/Sand Storage Dams are constructed in the arid and semi-arid areas. The suitable areas are dry river-bed, seasonal stream or lagga, which receives some flow during the rainy season. The sand retains the water for relatively long periods after the surface flow in the river has ceased. The volume of water stored varies depending on the grading of the sand and gravel. In most cases, the available water is about 20% to 30 % of the total volume of sand. The water is retained behind the dam structure. The dam structure is built on an impermeable layer of rock or clay. Pumping wells or any other suitable outlet structure is located upstream for drawing water and delivering it to the community to avoid damage caused by direct access to the dam. The water quality in sub-surface dams is usually much better than water from open surface reservoirs, since it is protected from direct contact with animals and humans.


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Water Source 3.1.4 Water Pans Spring Protection Water pans are shallow natural or man-made depressions on the ground surface, where water can be collected from surface flow or direct from a nearby seasonal stream (lagga). Water pans are constructed in the arid and semi-arid areas for livestock watering. Springs and surface flow are the source of water to water pans. Water is stored in the form of a pond with an open water surface. This results to evaporation losses. The capacity of water pans ranges from few hundred cubic metres for natural depressions and small man-made pans, to 20,000 m3 for the Ministry of Water and Irrigation Standard large capacity design. There are two types of water pans/earth dam construction. These are simple excavation pit in flat areas or in existing depressions and embankment ponds where water is retained within an earth embankment comprising impervious soils. For domestic use, a hand-dug well positioned adjacent to the pan will provide better quality water, particularly if a graded sand and gravel filters links the well to the pan or earth dam. 3.1.5 Roof Catchment

Capital Cost

Running Cost

Recommended Comments/Requirements Regions Nation wide provided there exists reliable spring eye

Low; Medium if piped to Low community

Gravity Supply

Hand Dug Wells

Roof catchment is the most common type of rainwater catchment system, and offers the greatest potential for development in the future. It provides the cleanest and most convenient of all rainwater supplies. However, it is highly dependent on the amount of rainfall. Proper design and construction of the system is a prerequisite to the efficient functioning of the system. To prevent water contamination, care should be take in selecting the roof catchments e.g. avoid roofs near rubbish disposal area, industrial emissions and hospital rubbish pit/incinerators. 3.1.6 Surface Runoff

Sand Dam/Subsurface dams Water Pans

Surface runoff occurs when the rate of rainfall on a surface exceeds the rate at which water can infiltrate the ground. The excess water flows on the ground surface and can be collected for domestic, livestock or irrigation use. Underground tanks and reservoirs (surface dams, water pans, earth dams etc.) are conveniently used to collect and store surface run off water. This technology is highly depends on high amount of rainfall and rain water can easily be contaminated especially where communities dispose human excreta in the cathcment area. 3.1.7 Rock Catchment

River/Lake Abstraction

Rock catchment is a catchment area formed by a bare rock surface and a pond normally formed by a concrete weir. The catchment area may be extended using cement guttering. The rock catchment depends on geology. The rock catchment depends on availability of existing quality rock surfaces, and density of rock outcrops in an area. The storage capacity of rock catchment varies from 20 m 3 to 10,000 m3 depending on the size of the rock outcrop, and its area extent, elevation and gradient. 3.1.8 Summary of Water Facilities Capital Cost Medium, storage tanks needed Running Cost Low Recommended Comments/Requirements Regions North eastern, Eastern, Central, Rift Valley, Western, Nyanza provinces North eastern, Eastern, Rift Valley, Needs two wet seasons a year, preferably. Water quality is good for roof catchment and poor for surface run off. Suits deep underground aquifer. Needs maintenance of mechanical pumps. Requires acquisition of license from NEMA and Authorization permit from WRMA.8

Needs a reliable spring flow throughout the year. Requires acquisition of license from NEMA and Authorization permit from WRMA. High pipeline and local Low Nation wide Needs a stream or spring source at a storage provided there higher elevation. Major advantage is exists reliable that the taps stands can be near water source fromhouses. Requires acquisition of lake, river, license from NEMA and borehole, spring Authorization permit from WRMA. etc Low (local labour) Hand Low North eastern, Abstraction can be by hand pumps. Pump Needed Eastern provinces Buckets do contaminate drinking water, thus not preferred. Requires acquisition of license from NEMA and Authorization permit from WRMA. Low; Medium if building Low North eastern, Required high accumulation of sand stones are not readily Eastern provinces soil. Can be used to recharge shallow available. wells and springs. Needs acquisition of license from NEMA and Authorization permit from WRMA. Low Low North eastern, Suitable for areas clay soils else Eastern provinces polythene or concrete lining would be needed to prevent water losses through seepage. High High Nyanza, Western, Last resort. Filtration essential. Design and construction Treatment and Central and Rift Maintenance required for filtration of intake pumping usually valley provinces and dosing plant. Requires acquisition needed of license from NEMA and Authorization permit from WRMA.

NB: Detailed site investigations should be carried out at each particular site to determine the suitability of each technological option prior to project implementation. 3.1.9 Monitoring of Water Facilities

Water Source Rainwater harvesting (Roof catchment and surface run off) Boreholes

Once a water facility has been commissioned, a routine monitoring and evaluation programme should be established so that its performance can be verified and the actual output of the facility established. The exercise can be conducted on monthly, quarterly, semi-annual or annual basis depending on the nature and size of the project. More sensitive technologies require frequent monitoring e.g. borehole while simple technologies like water pan would adequately be monitored before and after a rainy season. Routine monitoring of the functionality of facility permits a regular assessment to be made of whether it is serving the intended purpose and that the water quality complies with the water standards. In addition, timely project monitoring and evaluation enables the required repair actions to be taken on time. Monitoring of selected performance parameters should provide sufficient information to measure performance in meeting project objectives. If monitoring results indicate that the system is not working according to the objectives, corrective measures must be applied. Improvement of water quality and quantity may be assessed by conducting laboratory tests and analysing the changes in service levels.

Medium ,Well drilling equipment needed

Medium, Mechanical Pumping




4.0 STANDARD PROCEDURES FOR WATER FACILITIES 4.1 Technical Procedures for Boreholes

Once screen, pack, seals and backfill have been installed, the well should be developed. Development aims at repairing the damage done to the aquifer during the course of drilling by removing clays and other additives from the borehole walls. Secondly, it alters the physical characteristics of the aquifer around the screen and removes fine particles. We do not advocate the use of over pumping as a means of development since it only increases permeability in zones, which are already permeable. Instead, we would recommend the use of air or water jetting, or the use of the mechanical plunger, which physically agitates the gravel pack and adjacent aquifer material. This is an extremely efficient method of developing and cleaning wells. Well development is an expensive element in the completion of a well, but is usually justified in longer well-life, greater efficiencies, lower operational and maintenance costs and a more constant yield. Within this frame, the pump should be installed at least 2m above the screen, certainly not at the same depth as the screen. 4.1.7 Well Testing

The borehole is supposed to be drilled not less than 0.8 km radius from an existing one as a water act requirement. To determine suitable spacing for economical and sustainable borehole system, test pumping, modelling and property boundaries are used. The criterion for successful rate of borehole is borehole yield: 330 l/hr or more and water quality. 4.1.1 Drilling Technique

Drilling should be carried out with an appropriate tool either percussion, piling or rotary piling machines will be suitable, though the latter are considerably faster. Geological rock samples should be collected at 2-metre intervals. Struck and rest water levels and if possible, estimates of the yield of individual aquifers encountered should also be noted. Monitoring of the electrical conductivity of each aquifer encountered should be done. 4.1.2 Well Design

The design of the well should ensure that screens are placed against the optimum aquifer zones. The final design should be made by an experienced driller or hydro geologist. The well head should be water tight, lockable by threading and constructed from material that is not easily corroded. The electrical cables for the power supply should be buried below ground level. 4.1.3 Casing and Screens

After development and preliminary test, a long-duration well test should be carried out. Well tests have to be carried out on all newly-completed wells, because aside from giving an indication of the quality of drilling, design and development, it also yields information on aquifer parameters which are vital to the hydro geologist. A well test consists of pumping a well from a measured start level (Water Rest Level (WRL) at a known or measured yield, and simultaneously recording the discharge rate and the resulting draw downs as a function of time. Once a dynamic water level (DWL) is reached, the rate of inflow to the well equals the rate of pumping. Usually the rate of pumping is increased step wise during the test each time equilibrium has been reached (Step Draw-Down Test). Towards the end of the test, a water sample of 2 litres should be collected for chemical analysis. The duration of the test should be 24 hours, followed by a recovery test for a further 24 hours, or alternatively until the initial WRL has been reached (during which the rate of recovery to WRL is recorded). The results of the test will enable a hydro geologist to calculate the optimum pumping rate, the installation depth, and the draw down for a given discharge rate. 4.2 4.2.1 Bills of Quantities for Boreholes Boreholes with Electric Pump and Various Depths

The well should be cased and screened with good quality material. Owing to the depth of the borehole, the high salinity coupled with incidence of corrosion in the area, it is recommended to use high quality uPVC casing and screens with high effective open surface area. Alternatively galvanized steel casings and Johnsons screens of high open surface area may be used. We strongly advise against the use of torch-cut steel well-casing as screen. In general, its use will reduce well efficiency (which leads to lower yields), increase pumping costs through greater draw down, increase maintenance costs, and eventually reduction of the potential effective life of the well. In addition, the slot size of these screens is too large and will enhance siltation of the wells due to presence of silts in the formation. 4.1.4 Gravel Pack

4.2.1.1 BILL OF QUANTITIES FOR BOREHOLE 80 250 m DEPTH ITEM 1 2 3 4 5 6 7 8 9 10 11 12 139

The use of a gravel pack is recommended within the aquifer zone, because the aquifer could contain sands or silts which are finer than the screen slot size. A 1 meter diameter borehole screened at 40cm will leave an annular space of approximately 30cm, which should be sufficient. Should the slot size chosen be too large, the well will pump sand, thus damaging the pumping plant, and leading to gradual siltation of the well. The slot size should be in the order of 0.5 1mm. The grain size of the gravel pack should be an average 1 2 mm, although this should be determined after drilling and execution of on-site sieve analysis of the samples. 4.1.5 Well Construction

Once the design has been agreed, construction can proceed. In installing screen and casing, centralizers at 6 metre intervals should be used to ensure centrality within the borehole. This is particularly important so as to insert the artificial gravel pack all around the screen. If installed, gravel packed sections should be sealed off top and bottom with clay (2m). The remaining annular space should be backfilled with an inert material, and the top three metres grouted with cement to ensure that no surface water at the wellhead can enter the well bore and thus prevent contamination. 4.1.6 Well Development

DESCRIPTION A. Boring Boring B. Pump Station E. Pump Concrete (1:2:4) Reinforcement Gravel bedding Formworks C. Drain Concrete (1:2:4) Reinforcement Gravel bedding Formworks D. Livestock Trough Concrete (1:2:4) Reinforcement Gravel bedding

UNIT QUANTITY m Unit m3 kg m3 m2 m3 kg m3 m2 m3 kg m3 Various (80 -250) 1 1.21 10 0.7 4.59 1.8 0.02 0.8 18 0.71 10 2.16

RATE

AMOUNT(Kshs)




4.2.1.1 BILL OF QUANTITIES FOR BOREHOLE 80 250 m DEPTH 5.1.1 ITEM DESCRIPTION 14 Formworks Total 4.2.1.2 ITEM UNIT QUANTITY m2 4.8 RATE AMOUNT(Kshs) Dug Wells These have depths less than 30 metres. The diameter should be at least 1.2 m to allow two men to work together during the digging. The well should be dug at least 3m below the expected lowest water level. The well need to be lined with materials such as bricks, stone masonry, concrete rings cast insitu or precise concrete rings. The shallow well is excavated from inside but in loose soil hand-drilling should be used. If the area is rock, the well may stand unlined but the upper part should always have a lining. The section of the well penetrating the aquifer requires a lining with openings or perforations to allow the groundwater to enter. Any backfill at the same level as the aquifer should be made with gravel. The fine sand aquifers have lining without perforations and the groundwater should enter only through the bottom of the well. The bottom should be covered with graded gravel e.g. three layers each 150 mm thick with grain sizes 102 mm for the deepest layer, then 4 8 mm and 20 30 mm effective size at the top. As protection measure, the wall lining should be extended 0.5 m above the ground to form a wall round the well. In addition, the well top should be sealed with a watertight slab. In areas where there are shallow riverbeds saturated with sands, especially where there is a perennial sub-surface flow, shallow wells are the best technological options. 5.1.2 Hand-Drilled Wells

BOQ for Wind Pump in 80m BH 3.7 m Diameter Rotor, 10 m Head and 80 m Borehole DESCRIPTION A. Wind pump Machine including Standard Tower 10 ft. Tower extension Shallow well crossbeam Pump rods Stifling box Transport (100 km) 2" Pipe fittings, air bottle and shroud 2 2/4 Deep well pump cylinder 3 3/4 Deep well pump cylinder Installation B. Borehole C. Storage tank (Capacity:28 m3) Concrete (1:2:4) Reinforcement Excavation, common Backfilling Formworks C. Tap Station Concrete Reinforcement Excavation, common Backfilling Sub-Total UNIT QUANTITY RATE AMOUNT(Kshs) each each each each each each each each each day m m3 kg m3 m3 m2 1 1 1 1 1 1 1 1 1 5 80 13.98 0.7 86.64 54.9 72.16

Hand drilling of 150 300 mm diameter wells down to a depth of 15 20 m is particularly feasible in clay and sand soils. A filter pipe of 6m length and 100 150 m diameter and a sand filter should be put in the well. 5.1.3 Mechanical Well Drilling

Mechanical well drilling has to be used in layers with big stones and boulders and in heavily cemented soils. The protection is as that of dug wells. 5.2 Dimensions of Shallow wells

m3 kg m3 m3

0.86 0.9 15.2 11.1

Depths of hand-dug wells range from shallow wells, about 5 metres deep, to deep wells over 0 metres deep. Wells with depths of over 30 metres are sometimes constructed to exploit a known aquifer. It is impractical to excavate a well which is less than a metre in diameter; an excavation of about 1.5 metres in diameter provides adequate working space for the diggers and will allow a fnal internal diameter of about 1. metres after the well has been lined. 5.3 (a) Various Procedures for Hand Dug Wells Digging with the sides of the excavation supported

Drawings for Boreholes i. Water Facilities Drawings\Boreholes\Bore hole and Wind Pump.pdf

There are several methods of supporting the sides of the excavation while digging proceeds: 1 The safest method is to excavate within pre-cast concrete rings which later become the permanent lining to the sides of the well. The frst ring has a cutting edge, and additional rings are placed on it as excavation proceeds. As material is excavated within the ring, it sinks progressively under its own weight and that of the rings on top of it. This method should always be used in unstable ground. When construction has fnished, the joints between the rings which are above the water table should be sealed with cement mortar. 2 In suitable ground, excavation may proceed for a short distance without support to the sides; these are then supported by means of concrete poured in situ from the top, between the sides of the excavation and temporary formwork, which becomes the permanent lining to the well. This process is repeated until the water table is reached. In suitably stable ground, excavation may proceed within the protection of vertical close-ftting timber boards, supported by horizontal steel rings. The timbers are hammered down as excavation proceeds and additional timbers are added progressively at ground level. The steel rings must be hinged, or in two parts bolted together,

5.0 TECHNICAL PROCEDURE FOR SHALLOW WELLS 5.1 Description of Shallow Wells

Shallow wells are classified according to the manner of construction as; dug wells, hand drilled and mechanical drilled wellsTechnical Manual for Water Facilities 10

3



so that lower ones can be added as the excavation progresses. The vertical spacing between the rings will depend on the instability of the ground. The well is lined with bricks, or concrete blocks, from the water table upwards, within the timbers as they are withdrawn. (b) Digging with the sides of the excavation unsupported

In stable ground, wells are often excavated down to water level without a lining, and are lined with in situ concrete, or with pre-cast concrete rings, from this level upwards. Wells safely dug during the dry season may become unstable when the water level rises in the wet season and therefore must be lined before this occurs to prevent a collapse. Although in firm stable ground unlined wells may be safely excavated and may give long service in operation, it is prudent, and in most cases essential, to provide a permanent supporting lining which will support the sides of the excavation and prevent them from collapsing; suitable lining materials are concrete, reinforced concrete, ferrocement, masonry, brickwork, etc. (c) Excavation below the water level

5..2.1 BOQ for Shallow well and hand pump 10 m depth ITEM DESCRIPTION C. Drain 7 Concrete (1:2:4) 8 Reinforcement 9 Gravel bedding 10 Formworks D. Livestock Trough 11 Concrete (1:2:4) 12 Reinforcement 13 Gravel bedding 14 Formworks Total

UNIT m3 kg m3 m2 m3 kg m3 m2

QUANTITY 1.8 0.02 0.8 18 0.71 10 2.16 4.8

RATE

AMOUNT(Kshs)

Regardless of which method has been used to excavate the well to the water table, excavation below this level should never be attempted until the sides of the excavation have received the support of their permanent lining, from water table to ground level. Excavation below the water table should be carried out within pre-cast concrete caisson rings of a smaller diameter than the rest of the well. The initial caisson ring is provided with a cutting edge and additional rings are placed on top of it; as the material within is excavated, the rings sink progressively under their own weight. To facilitate the ingress of water, these lower rings are often constructed with porous, or no-fines, concrete and their joints are left unpointed (d) Completion

5..2.2 BOQ for Shallow well and hand pump 20 m depth ITEM DESCRIPTION A. Boring 1 Boring 2 3 4 5 6 7 8 9 10 11 12 13 14 B. Hand pump Station Hand pump Concrete (1:2:4) Reinforcement Gravel bedding Formworks C. Drain Concrete (1:2:4) Reinforcement Gravel bedding Formworks D. Livestock Trough Concrete (1:2:4) Reinforcement Gravel bedding Formworks Total

UNIT m Unit m3 kg m3 m2 m3 kg m3 m2 m3 kg m3 m2

QUANTITY 20 1 1.21 10 0.7 4.59 1.8 0.02 0.8 18 0.71 10 2.16 4.8

RATE

AMOUNT(Kshs)

After construction of the well shaft has been completed, the bottom is plugged with gravel. This helps to prevent silty material from clay soils, or fines from sandy materials, being drawn into the well. Any annular space between the precast caisson well rings and the side of the excavation should also be filed with gravel; such filling behind the rings which are below the water helps to increase water storage and to prevent the passage of fine silts and sands into the well. The space behind the top three metres, or so, of the well rings should be backfilled to ground level with puddled clay, or concrete, and the well rings should project about one metre above a concrete apron. This apron provides a sanitary seal to prevent polluted surface water seeping into the well and should slope away from it and drains into a channel which discharges into a soak away. (e) Abstraction

It is desirable for the well to have a concrete cover slab to reduce the possibility of contamination. Water is safely abstracted by means of a rope and washer pump above an access hole, or a hand pump, depending upon the yield of water available and the ability of the benefiting community to pay for ongoing maintenance for the hand pump, spare parts, etc. A hand-dug well fitted with a hand pump can serve the needs of about 300 people. 5.2 Bills of Quantities for Shallow wells 5.3 UNIT m Unit m3 kg m3 m2 QUANTITY 10 1 1.21 10 0.7 4.5911 14

5..2.1 BOQ for Shallow well and hand pump 10 m depth ITEM DESCRIPTION A. Boring 1 Boring B. Hand pump Station 2 Hand pump 3 Concrete (1:2:4) 4 Reinforcement 5 Gravel bedding 6 FormworksTechnical Manual for Water Facilities

Drawings for Shallow Wells Water Facilities Drawings\Shallow Wells\Shallow Well with Hand Pump.pdf

RATE

AMOUNT(Kshs)



6.0 TECHNICAL PROCEDURE FOR SUB-SURFACE/SAND STORAGE DAM The sub-surface/Sand Storage Dams are built in the riverbeds and have dam walls built of soil that stretch across the riverbed in seasonal water courses with sand, also called sand rivers, dry riverbeds, laggas, wadis etc. The sub-surface dams blocks floodwater that has infiltrated into the voids between the sand particles. They store up to 35% water in the voids in course sand. Weirs, built of stone masonry or concrete function as subsurface dams, but can store more water because they can be built to 50 cm above the surface of the surrounding sand. Sand dams are structures larger than weirs, which can be raised to several metres above the sand surface of seasonal water courses and gullies. The dam across the river should done in stages to ensure that mainly sand and gravel are deposited. The first stage is 2 m high. Later the wall should be raised as the sand and gravel builds up until the full height, often 6 12 m is reached. Pumping wells or any other suitable outlet structure is located upstream for drawing water and delivering it to the community to avoid damage caused by direct access to the dam. 6.1 6.1.1 Bills of Quantities for Sub surface/sand Dams

6.1.2

Bill of Quantities for Rubble Masonry Sub-surface Dam with well 2 m high and 25 meter long B. Water Abstraction Stone/Gravel filter Unit 5.94 3 Concrete Pipe (1.0 m diameter) m 4 Common excavation kg 28.57 Backfill m3 17.81 Total

6.1.3

Bill of Quantities for Rubble Masonry Sub-surface Dam with well 2 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY A. Sand Dam Site Clearing m2 400 3 Excavation, common m 625 3 Excavation, rock m 102.88 3 Backfilling m 548.5 3 Rubble masonry m 175 B. Water Abstraction Stone/Gravel filter Concrete Pipe (1.0 m diameter) Common excavation Backfill Total 6.1.4 Bill of Quantities for Rubble Masonry Sub-surface Dam with well 3 m high and 10 meter long ITEM DESCRIPTION UNIT QUANTITY A. Sand Dam Site Clearing m2 110 3 Excavation, common m 245 3 Excavation, rock m 59.63 3 Backfilling m 231 3 Rubble masonry m 67.5 B. Water Abstraction Stone/Gravel filter Concrete Pipe (1.0 m diameter) Common excavation Backfill Total

RATE

AMOUNT(Kshs)

Bill of Quantities for Rubble Masonry Sub-surface Dam with well 2 m high and 10 meter long ITEM DESCRIPTION UNIT QUANTITY A. Sand Dam Site Clearing m2 80 3 Excavation, common m 125 3 Excavation, rock m 42.88 3 Backfilling m 128.5 3 Rubble masonry m 35 B. Water Abstraction Stone/Gravel filter Concrete Pipe (1.0 m diameter) Common excavation Backfill Total

RATE

AMOUNT(Kshs)

Unit m3 kg m3

5.94 4 28.57 17.81

RATE

AMOUNT(Kshs)

Unit m3 kg m3

5.94 4 28.57 17.81

6.1.2

Bill of Quantities for Rubble Masonry Sub-surface Dam with well 2 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY A. Sand Dam Site Clearing m2 200 3 Excavation, common m 312.5 Excavation, rock m3 65.38 3 Backfilling m 286 3 Rubble masonry m 87.5

RATE

AMOUNT(Kshs)

Unit m3 kg m3

7.42 5 35.34 22.27


12



6.1.5

Bill of Quantities for Rubble Masonry Sub-surface Dam with well 3 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY A. Sand Dam Site Clearing m2 275 3 Excavation, common m 612.5 3 Excavation, rock m 89.63 3 Backfilling m 527.25 Rubble masonry m3 168.75 B. Water Abstraction Stone/Gravel filter Concrete Pipe (1.0 m diameter) Common excavation Backfill Total 6.1.6

Common excavation Backfill Total RATE AMOUNT(Kshs)

kg m3

42.41 26.72

6.1.8 Bill of Quantities for Rubble Masonry Sub-surface Dam with well 4 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY A. Sand Dam Site Clearing m2 350 3 Excavation, common m 1012.5 3 Excavation, rock m 115.88 3 Backfilling m 845.5 3 Rubble masonry m 275 B. Water Abstraction Stone/Gravel filter Concrete Pipe (1.0 m diameter) Common excavation Backfill Total

RATE

AMOUNT(Kshs)

Unit m3 kg m3

7.42 5 35.34 22.27

Unit m3 kg m3

8.91 6 42.41 26.72

Bill of Quantities for Rubble Masonry Sub-surface Dam with well 3 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY RATE A. Sand Dam Site Clearing m2 550 Excavation, common m3 1225 Excavation, rock m3 139.63 3 Backfilling m 1021 3 Rubble masonry m 337.5 B. Water Avstraction Stone/Gravel filter Unit 7.42 Concrete Pipe (1.0 m diameter) m3 5 Common excavation kg 35.34 Backfill m3 22.27 Total 6.1.7 Bill of Quantities for Rubble Masonry Sub-surface Dam with well 4 m high and 10 meter long ITEM DESCRIPTION UNIT QUANTITY A. Sand Dam Site Clearing m2 140 3 Excavation, common m 405 3 Excavation, rock m 78.38 3 Backfilling m 365.5 3 Rubble masonry m 110 B. Water Abstraction Stone/Gravel filter Unit 8.91 Concrete Pipe (1.0 m diameter) m3 6Technical Manual for Water Facilities

AMOUNT(Kshs)

6.1.9 Bill of Quantities for Rubble Masonry Sub-surface Dam with well 4 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY RATE A. Sand Dam Site Clearing m2 700 3 Excavation, common m 2025 3 Excavation, rock m 178.38 3 Backfilling m 1645.5 3 Rubble masonry m 550 B. Water Abstraction Stone/Gravel filter Concrete Pipe (1.0 m diameter) Common excavation Backfill Total

AMOUNT(Kshs)

Unit m3 kg m3

8.91 6 42.41 26.72

RATE

AMOUNT(Kshs)

6.2 Rubble Masonry Sand Dam with Tap/Gate Valve 6.2.1 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 3 m high and 10 meter long ITEM DESCRIPTION UNIT QUANTITY RATE 1 Sand Dam (Capacity 2,180 m3) Site Clearing m2 90 3 Excavation, common m 90 3 Excavation, rock m 73.5 3 Backfilling m 13513

AMOUNT(Kshs)



6.2.1 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 3 m high and 10 meter long Rubble masonry m3 132.5 3 Concrete m 8.75 Reinforcing Bars kg 40 Formworks m2 30 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Total 6.2.2 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 3 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY 1 Sand Dam (Capacity 5,450 m3) Site Clearing m2 225 3 Excavation, common m 225 3 Excavation, rock m 148.5 3 Backfilling m 337.5 3 Rubble masonry m 293.75 3 Concrete m 8.75 Reinforcing Bars kg 80 Formworks m2 75 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter m 25 PVC pipe 50 mm Diameter m 12 Gate Valve/Tap each 2 Stone/Gravel filter m3 75 Total 6.2.3 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 3 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY 1 Sand Dam (Capacity 10,901 m3) Site Clearing m2 450 3 Excavation, common m 450 3 Excavation, rock m 273.5 3 Backfilling m 675 3 Rubble masonry m 562.5 3 Concrete m 8.75 Reinforcing Bars kg 40 2 Formworks m 150 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter m 70 PVC pipe 50 mm Diameter m 15Technical Manual for Water Facilities

m m each m3

10 10 2 30

Gate Valve/Tap each 2 Stone/Gravel filter m3 75 Total 6.2.4 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 4 m high and 10 meter long ITEM DESCRIPTION UNIT QUANTITY 1 Sand Dam (Capacity 3,876 m3) Site Clearing m2 100 3 Excavation, common m 150 3 Excavation, rock m 83.5 3 Backfilling m 240 3 Rubble masonry m 197.5 3 Concrete m 9.95 Reinforcing Bars kg 90 Formworks m2 40 RATE AMOUNT(Kshs) 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Total

RATE

AMOUNT(Kshs)

m m each m3

10 10 2 30

RATE

AMOUNT(Kshs)

6.2.5 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 4 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY RATE Sand Dam (Capacity 9,690 m3) Site Clearing m2 250 3 Excavation, common m 375 3 Excavation, rock m 158.5 3 Backfilling m 600 3 Rubble masonry m 433.75 3 Concrete m 9.95 Reinforcing Bars kg 90 2 Formworks m 100 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Total

AMOUNT(Kshs)

m m each m3

25 12 2 75

14



6.2.6 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 4 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY 1 Sand Dam (Capacity 19,380 m3) Site Clearing m2 500 3 Excavation, common m 750 3 Excavation, rock m 283.5 3 Backfilling m 1200 3 Rubble masonry m 827.5 3 Concrete m 9.95 Reinforcing Bars kg 100 Formworks m2 200 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Total

RATE

AMOUNT(Kshs)

6.2.8 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 5 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY RATE 3 1 Sand Dam (Capacity 15,140 m ) Site Clearing m2 275 3 Excavation, common m 550 3 Excavation, rock m 170.5 3 Backfilling m 937.5 3 Rubble masonry m 618.75 3 Concrete m 11.15 Reinforcing Bars kg 100 2 Formworks m 125 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Total

AMOUNT(Kshs)

m m each m3

70 15 2 75

m m each m3

25 12 2 75

6.2.7 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 5 m high and 10 meter long ITEM DESCRIPTION UNIT QUANTITY 1 Sand Dam (Capacity 6,056 m3) Site Clearing m2 110 3 Excavation, common m 220 3 Excavation, rock m 95.5 3 Backfilling m 375 3 Rubble masonry m 292.5 3 Concrete m 11.15 Reinforcing Bars kg 10 Formworks m2 50 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Total

RATE

AMOUNT(Kshs)

6.2.9 Bill of Quantities for Rubble Masonry Sand Dam with Tap/Gate Valve 5 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY RATE 1 Sand Dam (Capacity 30,281 m3) Site Clearing m2 550 3 Excavation, common m 1100 3 Excavation, rock m 295.5 3 Backfilling m 1875 3 Rubble masonry m 1162.5 3 Concrete m 11.15 Reinforcing Bars kg 110 Formworks m2 250 2 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Total

AMOUNT(Kshs)

m m each m3

10 10 2 30

m m each m3

70 15 2 75


15



6.3 Rubble Masonry Sand Dam with Storage tank 6.3.1 BOQ for Rubble Masonry Sand Dam with storage tank 3 m high and 10 meter long ITEM DESCRIPTION UNIT 1 Sand Dam (Capacity 2,180 m3) Site Clearing m2 Excavation, common m3 Excavation, rock m3 Backfilling m3 Stone masonry m3 Concrete m3 Reinforcing Bars kg Formworks m2 2 Storage (Capacity:1000 m ) Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks Total3

QUANTITY 90 90 73.5 135 132.5 8.75 40 30

RATE

AMOUNT(Kshs)

6.3.2 BOQ for Rubble Masonry Sand Dam with storage tank 3 m high and 25 meter long ITEM DESCRIPTION UNIT 1 Sand Dam (Capacity 5,450 m3) Site Clearing m2 Excavation, common m3 Excavation, rock m3 Backfilling m3 Stone masonry m3 Concrete m3 Reinforcing Bars kg Formworks m2 2 Storage (Capacity:2500 m3) Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks Total

QUANTITY 225 225 148.5 337.5 293.75 8.75 80 75

RATE

AMOUNT(Kshs)

m2 m3 m3 m3 kg m2

400 1682 76.8 179.2 7170 590.4

m2 m3 m2 m3 kg m2

841 1682 151.88 437.5 17500 1126.4

m m each m3 m3 kg m2

20 15 3 30 0.86 40 9.36


40 15 3 75 0.86 86 9.36


16



6.3.3 BOQ for Rubble Masonry Sand Dam with storage tank 3 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY RATE AMOUNT(Kshs) 1 Sand Dam (Capacity 10,901 m3) Site Clearing m2 450 3 Excavation, common m 450 3 Excavation, rock m 273.5 3 Backfilling m 675 3 Stone masonry m 562.5 3 Concrete m 8.75 Reinforcing Bars kg 40 Formworks m2 150 2 Storage (Capacity:5000 m3) Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks Total

6.3.4 BOQ for Rubble Masonry Sand Dam with storage tank 4 m high and 10 meter long ITEM DESCRIPTION UNIT 1 Sand Dam (Capacity 3,876 m3) Site Clearing m2 Excavation, common m3 Excavation, rock m3 Backfilling m3 Stone masonry m3 Concrete m3 Reinforcing Bars kg Formworks m2 2 Storage (Capacity:2000 m3) Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks Total

QUANTITY 100 150 83.5 240 197.5 9.945 0.1 40

RATE

AMOUNT(Kshs)

m2 m3 m2 m3 kg m2

1849 3698 252.3 629.3 25170 2059.2

m2 m3 m2 m3 kg m2

702.25 1404.5 1404.5 343.13 13.73 831.6


70 15 3 75 0.86 86 9.36


20 15 3 30 0.86 40 9.36


17



6.3.5 BOQ for Rubble Masonry Sand Dam with storage tank 4 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY RATE 1 Sand Dam (Capacity 9,690 m3) Site Clearing m2 250 3 Excavation, common m 375 3 Excavation, rock m 158.5 3 Backfilling m 600 3 Stone masonry m 433.75 3 Concrete m 9.95 Reinforcing Bars kg 100 Formworks m2 100 3 2 Storage (Capacity:5000 m ) Site Clearing m2 1296 3 Excavation, common m 2592 2 Excavation rock m 307.2 3 Concrete, structure m 704 Reinforcing Bars kg 28.16 Formworks m2 1434.4 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks Total

AMOUNT(Kshs)


40 15 3 75 0.86 86 9.36

6.3.6 BOQ for Rubble Masonry Sand Dam with storage tank 4 m high and 50 meter long ITEM DESCRIPTION UNIT 1 Sand Dam (Capacity 19,380 m3) Site Clearing m2 Excavation, common m3 Excavation, rock m3 Backfilling m3 Stone masonry m3 Concrete m3 Reinforcing Bars kg Formworks m2 2 Storage (Capacity:10000 m3) Site Clearing m2 Excavation, common m3 Excavation rock m2 Concrete, structure m3 Reinforcing Bars kg Formworks m2 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter m PVC pipe 50 mm Diameter m Gate Valve/Tap each Stone/Gravel filter m3 Concrete m3 Reinforcing Bars kg Formworks m2 Total 6.3.7 BOQ for Rubble Masonry Sand Dam with storage tank 5 m high and 10 meter long ITEM DESCRIPTION UNIT 1 Sand Dam (Capacity 6,056 m3) Site Clearing m2 Excavation, common m3 Excavation, rock m3 Backfilling m3 Stone masonry m3 Concrete m3 Reinforcing Bars kg Formworks m2 2 Storage (Capacity: 3000 m3) Site Clearing Excavation, common Excavation rock

QUANTITY 500 750 283.5 1200 827.5 9.95 100 200 2025 4050 504 1135.7 45430 2163.2 70 15 3 75 0.86 86 9.36

RATE

AMOUNT(Kshs)

QUANTITY 110 220 95.5 375 292.5 11.15 0.11 50

RATE

AMOUNT(Kshs)

m2 m3 m2

992.25 1984.5 226.88


18



6.3.7 BOQ for Rubble Masonry Sand Dam with storage tank 5 m high and 10 meter long ITEM DESCRIPTION UNIT Concrete, structure m3 Reinforcing Bars kg Formworks m2 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks

QUANTITY 510.13 20410 1011.6

RATE

AMOUNT(Kshs)


20 15 3 30 0.86 40 9.36

6.3.9 BOQ for Rubble Masonry Sand Dam with storage tank 5 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY RATE 1 Sand Dam (Capacity 30,281 m3) Site Clearing m2 550 3 Excavation, common m 1100 3 Excavation, rock m 295.5 3 Backfilling m 1875 3 Stone masonry m 1162.5 3 Concrete m 11.15 Reinforcing Bars kg 110 Formworks m2 250 2 Storage (Capacity: 15000 m3) Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks Total 6.4 Gabion Sand Dam with Storage tank

AMOUNT(Kshs)

Total 6.3.8 BOQ for Rubble Masonry Sand Dam with storage tank 5 m high and 25 meter long ITEM DESCRIPTION UNIT 1 Sand Dam (Capacity 15,140 m3) Site Clearing m2 Excavation, common m3 Excavation, rock m3 Backfilling m3 Stone masonry m3 Concrete m3 Reinforcing Bars kg Formworks m2 2 Storage (Capacity: 7500 m3) Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks 3 Water Abstraction (Tap Station) PVC pipe 280 mm Diameter PVC pipe 50 mm Diameter Gate Valve/Tap Stone/Gravel filter Concrete Reinforcing Bars Formworks TotalTechnical Manual for Water Facilities

QUANTITY 275 550 170.5 937.5 618.75 11.15 110 250

RATE

AMOUNT(Kshs)

m2 m3 m2 m3 kg m2

2916 5832 750 1610 64.4 2631.2


70 15 3 75 0.86 86 9.36

m2 m3 m2 m3 kg m2

1849 3698 456.3 994.5 39.78 1742.4


40 15 3 75 0.86 86 9.36

6.4.1 Bill of Quantities for Gabion Sand Dam with Storage Tank 3 m high and 10 meter long ITEM DESCRIPTION UNIT QUANTITY RATE 1 Sand Dam Site Clearing m2 120 3 Excavation, common m 120 3 Excavation, rock m 140 3 Fill and Backfilling m 210 3 Gabion m 700 Concrete (1:2:4) m3 18.3 2 Storage Tank Site Clearing Excavation, common Excavation rock19

AMOUNT(Kshs)

m2 m3 m2

289 578 76.8



6.4.1 Bill of Quantities for Gabion Sand Dam with Storage Tank 3 m high and 10 meter long Concrete, structure m3 Reinforcing Bars kg Formworks, structure m2 3 Water Abstraction PVC pipe GI pipe Gate valve/Tap Stone/Gravel filter Concrete Pipe (tap station) Reinforcement Formwork, structure Total

38.4 3.46 989.28


20 15 3 30 0.86 8.6 9.36

6.4.3 Bill of Quantities for Gabion Sand Dam with Storage Tank 3 m high and 50 meter long ITEM DESCRIPTION UNIT QUANTITY RATE AMOUNT(Kshs) 1 Sand Dam Site Clearing m2 600 3 Excavation, common m 600 3 Excavation, rock m 700 3 Fill and Backfilling m 1050 3 Gabion m 1700 3 Concrete (1:2:4) m 42.3 2 Storage Tank Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks, structure 3 Water Abstraction PVC pipe GI pipe Gate valve/Tap Stone/Gravel filter Concrete Pipe (tap station) Reinforcement Formwork, structure Total

6.4.2 Bill of Quantities for Gabion Sand Dam with Storage Tank 3 m high and 25 meter long ITEM DESCRIPTION UNIT QUANTITY RATE 1 Sand Dam Site Clearing m2 300 3 Excavation, common m 300 3 Excavation, rock m 350 3 Fill and Backfilling m 525 3 Gabion m 625 3 Concrete (1:2:4) m 27.3 2 Storage Tank Site Clearing Excavation, common Excavation rock Concrete, structure Reinforcing Bars Formworks, structure

AMOUNT(Kshs)

m2 m3 m2 m3 kg m2

961 1922 252.3 356.7 17.84 1505.28


80 15 3 150 0.86 8.6 9.36

m2 m3 m2 m3 kg m2

300 1200.5 151.88 219.38 8.78 989.28

6.5 i. ii.

Drawings for Subsurface/Sand Dams Water Facilities Drawings\Sand-Sub surface Dams\Gabion Sand Dam with RC Tank.pdf Water Facilities Drawings\Sand-Sub surface Dams\Rubble masonry Sand Dam.pdf iii. Water Facilities Drawings\Sand-Sub surface Dams\Rubble Masonry Sand dam with RC Tank.pdf iv. Water Facilities Drawings\Sand-Sub surface Dams\Rubble Masonry Sand Dam with Well.pdf

3 Water Abstraction PVC pipe GI pipe Gate valve/Tap Stone/Gravel filter Concrete Pipe (tap station) Reinforcement Formwork, structure Total


45 15 3 75 0.86 8.6 9.36


20



7.0 TECHNICAL PROCEDURES FOR WATER PANS Water pans are shallow natural or man-made depressions on the ground surface, where water can be collected from surface flow or direct from a nearby seasonal stream (lagga). The capacity of water pans ranges from few hundred cubic metres for natural depressions and small man-made pans, to 20,000 m3 for the Ministry of Water and Irrigation Standard large capacity design. The design of water pan consists of a semi-circular dam wall shaped like a new moon. The wall is made of compacted earth and each end, which is strengthened with rocks, is designed to act as a spillway. To improve on the quality of water for domestic use, hand pumps, sand filters and cattle troughs should be incorporated into the system. Details on hand pumps and sand filters are shown in Section 12 and 13.2 respectively. Cattle troughs are meant to prevent contamination of water by livestock drinking water directly from the water pan. Good practice is to provide a sufficient watering area for young and mature livestock separately for ease of use and this should be located about 100m downstream of the pan. 7.1 Bills of Quantities for Water Pans 7.1.3 Bill of Quantities for Water pan 20,000 m3 Location: Ground is level to the base of the pan ITEM DESCRIPTION Water pan Site Clearing Excavation, common Embankment Clay blanket Sandy Clay Riprap Concrete pipe 0.6 m Diam Concrete pipe 1.0 m Diam Concrete Reinforcing Bars Formworks Total 7.1.4 Bill of Quantities for Water pan 20,000 m3 Location: Along the waterway (One side is open) ITEM DESCRIPTION Water pan Site Clearing Excavation, common Backfilling Clay blanket Sandy Clay Riprap Concrete pipe 0.6 m Diam Concrete pipe 1.0 m Diam Concrete (1:2:4) Reinforcing Bars Formworks Total Drawings for Water Pans Water Facilities Drawings\Water Pans\Water Pan Capacity 10,000 cu.pdf Water Facilities Drawings\Water Pans\Water Pan in Natural Water.pdf UNIT m2 m3 m3 m3 m m m3 m3 m3 m2 QUANTITY RATE AMOUNT(Kshs) 8,548.82 54.00 27483.92 1417.38 393.3 322.38 21 6 2.43 0.05 8.4 UNIT m2 m3 m3 m3 m3 m m m3 m3 m2 m2 QUANTITY RATE AMOUNT(Kshs) 10,393.71 54.00 35,857.67 1417.38 393.3 394.62 21 6 2.43 0.05 8.4

7.1.1 Bill of Quantities for Water pan 20,000 m3 Location: Ground is level to the dike's berm ITEM DESCRIPTION Water pan Site Clearing Excavation, common Clay blanket Sandy Clay Riprap Concrete pipe 0.6 m Diam Concrete pipe 1.0 m Diam Concrete Reinforcing Bars Formworks Total 7.1.2 Bill of Quantities for Water pan 20,000 m3 Location: Depression ITEM DESCRIPTION Water pan Site Clearing Excavation, common Clay blanket Sandy Clay Riprap Concrete pipe 0.6 m Diam Concrete pipe 1.0 m Diam Concrete Reinforcing Bars Formworks TotalTechnical Manual for Water Facilities

UNIT m2 m3 m3 m3 m3 m m m3 m3 m2

QUANTITY RATE 10,393.71 20,615.34 1,417.38 393.3 394.62 21 6 2.43 0.05 8.4

AMOUNT(Kshs)

UNIT m2 m3 m3 m3 m3 m m m3 m3 m2

QUANTITY RATE 10,393.71 31,633.95 1,417.38 393.3 394.62 21 6 2.43 0.05 8.4

AMOUNT(Kshs)

7.2 i. ii.

21



8.0 8.1

TECHNICAL PROCEDURES RAIN WATER HARVESTING Parameters

b) Assess whether the system will cause any problems for people in the area. Are there buildings, roads or pathsalong the runoff flow path that may be affected or cause water pollution? c) Depending on the size of the proposed reservoir or tank, consider the availability of human labour or earth moving machinery for excavation and construction works. Rain may fall on roads, fields, bushes or rock outcrops. If there is any possibility of contamination of the water by human or animal waste, it is vital to treat the water before use if it is used for domestic purposes. Risk of contamination with industrial or agricultural chemicals should be addressed prior to the construction of the system. 8.1.4 Selection of Tank Size

The parameters outlined below are considered in the design of roof catchments and rain water harvesting tanks. 8.1.1 Runoff Coefficients

The following run-off coefficients should be used for calculating the fraction of the rainfall which can be harvested. The 90 % probability annual rainfall should be regarded as the dependable rainfall for the purpose of rainwater harvesting for domestic use. Table 4.1 Run-off Coefficient Surface Type Roof tiles, corrugated sheets, concreted bitumen, plastic sheets Brick pavement Compacted soil Uncovered surface, flat terrain Uncovered surface, slope 0 5 % Uncovered surface, slope 5 10 % Uncovered surface, slope > 10 % Run-off Coefficient 0.8 0.6 0.5 0.3 0.4 0.5 >0.5

The required capacity of the collection tank should be calculated using available meteorological data showing the rainfall pattern of the area. But for rough calculations the tank capacity may be calculated by the formula: C = 0.03 x D x (T 2), Where:C = Tank Capacity in m3 D = Total water demand in litres/day T = Longest dry spell in months, average year. The dry spell is the period when the average monthly rainfall is less than 50 mm. 8.2. Rainwater Harvesting

8.1.2

Roof Catchments

Rainfall records representative of the catchment are essential as the basis for reliable design of such a system. For a catchment of area A m2 receiving rainfall run in a month, the yield Y is calculated as follows:Y = f x A x R m3/month 1000 Where; f = catchment run off coefficient typical values as given in table 4.1. If in an area, P is the population supplied by drinking water entirely from rainwater system, the quantity of water to be supplied per month, Q will be:Q = P x 30 x C m3/month 1000 Where C = daily consumption per person l/p/d.

A rough estimate of the required minimum roof area can be calculated as follows:A = 450 x D R Where; A = Minimum roof area in m2 D = Total water demand in litres/day R = The 90 % probability annual rainfall in mm. 8.1.3 Surface Runoff Catchment

Surface runoff can be generated either by rainfall or by the melting of snow or glaciers. In Kenya, surface run off comes mainly from heavy rainfall. Water from light showers is easily absorbed by soil storage and surface run off occurs only when the rate of rainfall on a surface exceeds the rate at which water can infiltrate the ground, and any depression storage has already been filled. Surface run off can harvested using underground catchments and can be stored in reservoirs such as water pans, and underground tanks depending on water usage, available development funds and existing ground conditions. Surface runoff from a hillside Before building a runoff harvesting system, the following factors need to be considered:a) If the system is to be on communal lands, the community must get together and agree on ownership, operation and maintenance of the systemTechnical Manual for Water Facilities 22

With a large variation in rainfall distribution, the more critical parameter is the minimum storage volume required. Selecting the critical or design draught period, T months, from rainfall records, the minimum storage volume, V mm is given by:Vmin = N x 30 x C x T m3 1000 Hence a family of 6 will require a storage volume of 10.8 m3 to span a four month drought period. 8.3 Tank Design

The standard capacities of the ministry should be used. They are 10, 25, 50, 100, 150, 200, 300, 500, 800 and 1200 m3. Larger tanks may have capacities as required. The tank should:-

a) Be equipped with internal and external ladder or steps.



b) c) d) e) f) g) h) i) j) k)l) 8.4

have a level indicator which can be read from outside have inlet pipe which ends not more than 0.5 m above the floor to prevent air entrainment Have outlet at a level at least 0.2 m above the floor. Have a scour pipe which allows complete emptying. have an overflow placed at least 50 mm above the normal top water level which allows the overflowing water to be seen when in operation. be designed so that the ball valve (if any) is above the highest water level and is easily accessible from the manhole. have ventilation pipes covered with nylon nets. have outside walkway and handrail (only elevated steel tanks) not usually have any portioning not have a ball valve on the inlet pipe when a pumping main feeds it. be covered and have a lockable manhole cover, universal type Bills of Quantities for Storage Tanks Parameters: 1

Total

Technology Specific Variables Area of Roof Catchment Length of gutters Volume of storage tank Average capacity Design 1: Plastic Tanks Volume of Tank Number of Storage tanks Size of Platform = Diameter of Tank + 20% Thickness of platform Bills of Quantities ITEM 1.1 1.6 2.1 2.2 2.5 3.3 3.4 3.5 4.1 4.2 ITEM DECRIPTION Excavate over site to remove topsoil Compacted hardcore bed Provide and place 75mm thick mass concrete blinding class 1:3:6 Provide, place and compact structural concrete C20; 1:2:4 Supply, cut, bend and place high tensile steel bars 225 mm natural stone walling Plastering Cement screed 32 mm thick Plastic Tank 15000Litre Aluzinc Gutters incl fittings & pipes (+50%) Pipe and fittings (20mm bibcock and fittings) Misc. paving, finishing work etc Total

Parameters: 2 100 20 12 0.204 m m3 m3/day

15,000 1 3.10 10% UNIT m2 m3 m3 m3 Kg m2 m3 m2 Item m Item Item

Litre

Roof rainwater harvesting Technology Specific Variables Max size Plastic tank Max size Ferrocement tank Max size Masonry tank Area of Roof Catchment Length of gutters Volume of storage tank Average capacity m m3 m2 m m3 m3/day3

m of platform size QTY 9.6 1.4 0.5 2.5 63 3.8 0.08 10 1 20 1 1 RATE AMOUNT (Ksh)

23 300 15 4 2 0.031

Design 1: Plastic Tanks Volume of Tank Number of Storage tanks Size of Platform = Diameter of Tank + 20% of platform size Bills of Quantities ITEM ITEM DECRIPTION 1.1 Excavate oversite to remove topsoil 1.6 Compacted hardcore bed 2.1 Provide and place 75mm thick mass concrete blinding class 1:3:6 2.2 Provide, place and compact structural concrete C20; 1:2:4 2.5 Supply, cut, bend and place high tensile steel bars 3.3 225 mm natural stone walling 3.4 Plastering 3.5 Cement screeding 32 mm thick 4.1 Plastic Tank 2300Litre 4.2 Aluzinc Gutters incl fittings & pipes (+50%) 4.3 Pipe and fittings (20mm bibcock and fittings) 4.4 Misc. paving, finishing work etcTechnical Manual for Water Facilities

Litre

23,000 1

m

2.04 10%

UNIT m2 m3 m3 m3 Kg m2 m3 m2 Item m Item Item

QTY RATE 4.2 0.6 0.2 0.6 15 1.7 0.03 4 1 4 1 1

AMOUNT (Ksh)

4.3 4.4

23



Technology Specific Variables Area of Roof Catchment Length of gutters Volume of storage tank Average capacity Design 1: Plastic Tanks Volume of Tank Number of Storage tanks Size of Platform = Diameter of Tank + 20% Thickness of platform ITEM ITEM DECRIPTION 1.1 Excavate oversite to remove topsoil 1.6 Compacted hardcore bed 2.1 Provide and place 75mm thick mass concrete blinding class 1:3:6 2.2 Provide, place and compact structural concrete C20; 1:2:4 2.5 Supply, cut, bend and place high tensile steel bars 3.3 225 mm natural stone walling 3.4 Plastering 3.5 Cement screeding 32 mm thick 4.1 Plastic Tank 23000Litre 4.2 Aluzinc Gutters incl fittings & pipes (+50%) 4.3 Pipe and fittings (20mm bibcock and fittings) 4.4 Misc. paving, finishing work etc Total

Parameter: 3 300 40 34 0.613 m2 m m3 m3/day Technology Specific Variables Area of Roof Catchment Length of gutters Volume of storage tank Average capacity 23,000 2 3.60 10% UNIT m2 m3 m3 m3 Kg m2 m3 m2 Item m Item Item m of platform size QTY 25.9 3.9 1.3 8.0 200 10.4 0.21 26 2 40 1 1 RATE AMOUNT (Ksh) Litre Design 1: Plastic Tanks Volume of Tank Number of Storage tanks Size of Platform = Diameter of Tank + 20% Thickness of platform ITEM ITEM DECRIPTION 1.1 Excavate oversite to remove topsoil 1.6 Compacted hardcore bed 2.1 Provide and place 75mm thick mass concrete blinding class 1:3:6 2.2 Provide, place and compact structural concrete C20; 1:2:4 2.5 Supply, cut, bend and place high tensile steel bars 3.3 225 mm natural stone walling 3.4 Plastering 3.5 Cement screeding 32 mm thick 4.1 Plastic Tank 23000Litre 4.2 Aluzinc Gutters incl fittings & pipes (+50%) 4.3 Pipe and fittings (20mm bibcock and fittings) 4.4 Misc. paving, finishing work etc Total 23,000 5 3.60 m RATE AMOUNT (Ksh) Litre Parameter: 4 1,000 100 111 2.045 m2 m m3 m3/day

10% of platform size UNIT QTY m2 64.8 m3 9.7 3 m 3.2 m3 Kg m2 m3 m2 Item m Item Item 20.1 502 25.9 0.52 65 5 100 1 1


24



Bills of Quantities for a 15 m3 brick tank ITEM ITEM DECRIPTION 1 Cement 2 Lime 3 River Sand 4 Crushed stones 5 Hardcore 4x6 6 Blocks/Bricks 7 Water 8 Weld mesh 8x4 No. 8 9 Barbed wire gauge 12.5, 20kg 10 Twisted Bars Y12 11 Binding wire gauge 8 12 uPVC 4 pipe 13 G.I. Pipe 14 G.I. tap, elbow, socket nipple 14 Galvanised coffee mesh 15 Mosquito mesh 16 Timber 6x1 17 Poles 18 Nail 3 Total

UNIT Kg Kg Tonnes Tonnes Tonnes Units Litres Sheets Rolls M Kg m m Units m2 m2 m m Kg

QTY 1250 100 6 4 1 555 1000 10 2 15 1 3 3 1 1 0.5 90 8 4

RATE

AMOUNT (Ksh)

Bills of Quantities of Quantities for a 50m3 Masonry R.C tank ITEM ITEM DECRIPTION UNIT QTY 1 Foundation 1.1 Removal of top soil up to 50 mm depth m2 1.2 Excavation for foundation m3 1.3 Laying of 300mm hardcore for m2 foundation 1.4 50 mm 1.2.4 concrete blinding m2 1.5 Finished floor concrete m3 1.6 Reinforcement for foundation Y 8 bars Kg Y12 2 Walls 2.1 Masonry wall m2 2.2 Y 8 reinforcement rings for the wall in No between courses 4.2 Aluzinc Gutters incl fittings & pipes m (+50%) 4.3 Pipe and fittings (20mm bibcock and Item fittings) 4.4 Misc. paving, finishing work etc Item Total

Bills of Quantities for a 46 m3 ferrocement tank ITEM ITEM DECRIPTION 1 Cement 2 Lime 3 River Sand 4 Crushed stones 5 Hardcore 4x6 6 BRC Mesh No 65 7 Water 8 Chicken mesh 25mm, 0.9m 9 G.I wire, 3mm 10 Twisted Bars Y12 11 Binding wire gauge 8 12 uPVC 4 pipe 13 uPVC 2 pipe 14 G.I. Pipe 15 G.I. tap, elbow, socket nipple 16 Galvanised coffee mesh 17 Mosquito mesh 18 Timber 6x1 19 Timber 2x 3 20 Poles 21 Bolts 6 x 120 mm 22 Plastic bag 23 Sisal twine 24 Nail 3

UNIT Kg Kg Tonnes Tonnes Tonnes m Litres m Kg M Kg m m m Units m2 m2 m m m No No Kg Kg

QTY 2500 50 10 4 1 33 3500 80 25 3 1 3 3 3.4 1 1 0.5 36 46 8 12 50 5 4

RATE

AMOUNT (Ksh)

RATE 1 19.6 11.8 19.6 19.6 11.8 26 250 47.1 28 12 1 1

AMOUNT (Ksh) Total

8.5

Drawings for Roof Catchments

i. ii. iii. iv. v. vi. vii.

Water Facilities Drawings\Roof Catchment\Plastic Tanks.pdf Water Facilities Drawings\Roof Catchment\15cu.m Tank Built of Soil Compressed Bricks.pdf Water Facilities Drawings\Roof Catchment\Bricks Tank.pdf Water Facilities Drawings\Roof Catchment\Ferrocement Tank.pdf Water Facilities Drawings\Roof Catchment\25 and 50 RC Tank Details.pdf Water Facilities Drawings\Roof Catchment\RC Tank.pdf Water Facilities Drawings\Roof Catchment\RC Tank.pdf


25



9.1.2 Bill of Quantities for Rock Catchment 2m High and 15 m Length Dam 9.0 ROCK CATCHMENT Rock catchments system consists of two components, a catchment area formed by a bore rock surface and a pond normally formed by concrete weir. The rock catchment is an extremely low cost method of community water supply, which lends itself well to community participation. The storage capacity of the reservoir may vary from 20 m3 to 10,000 m3 depending on the size of the rock outcrop, and its area extent, elevation and gradient. The storage capacity can be estimated using equation below:S = S (I) + I D Where:S = storage at the end of the month S (I) = the amount stored at the end of previous month I = product of monthly rainfall x rock area x loss factor D = amount of water used by a family in a given period 9.1 Bills of Quantities for Rock Catchment B. Tap Station Concrete Reinforcement bars Gravel bedding Formworks C. Drain Concrete Reinforcing Bars Gravel bedding Formworks D. Livestock Trough Concrete Reinforcing Bars Gravel bedding Formworks Total 9.1.3 Bill of Quantities for Rock Catchment2m High and 20 m Length Dam ITEM DESCRIPTION A. Dam Site Clearance Rock excavation Rubble Masonry GI pipe 110 mm B. Tap Station Concrete Reinforcement bars Gravel bedding Formworks C. Drain Concrete Reinforcing Bars Gravel bedding Formworks26

ITEM

DESCRIPTION A. Dam Site Clearance Rock excavation Rubble Masonry GI pipe 110 mm

UNIT m2 m3 m3 m m3 kg m3 m2

QUANTITY 97.50 97.50 75.00 50 1.21 10 0.7 4.59

RATE

AMOUNT(Kshs)

9.1.1 Bill of Quantities for Rock Catchment 2m High and 10 m Length Dam ITEM DESCRIPTION A. Dam Site Clearance Rock excavation Rubble Masonry GI pipe 110 mm B. Tap Station Concrete Reinforcement bars Gravel bedding Formworks C. Drain Concrete Reinforcing Bars Gravel bedding Formworks D. Livestock Trough Concrete Reinforcing Bars Gravel bedding Formworks UNIT m2 m3 m3 m m3 kg m3 m2 QUANTITY 65.00 65.00 50.00 50 1.21 10 0.7 4.59 RATE AMOUNT(Kshs)

m3 kg m3 m2

1.8 20 0.8 18

m3 kg m3 m2

0.71 10 2.16 4.8

UNIT m2 m3 m3 m m3 kg m3 m2

QUANTITY 130.00 130.00 100.00 50 1.21 10 0.7 4.59

RATE

AMOUNT(Kshs)

m kg m3 m2

3

1.8 20 0.8 18

m kg m3 m2

3

0.71 10 2.16 4.8

Total

m3 kg m3 m2 18

1.8 20 0.8




9.1.3 Bill of Quantities for Rock Catchment2m High and 20 m Length Dam 10. SPRING PROTECTION D. Livestock Trough Concrete Reinforcing Bars Gravel bedding Formworks Total 9.1.4 Bill of Quantities for Rock Catchment 2m High and 30 m Length Dam ITEM DESCRIPTION A. Dam Site Clearance Rock excavation Rubble Masonry GI pipe 110 mm B. Tap Station Concrete Reinforcement bars Gravel bedding Formworks C. Drain Concrete Reinforcing Bars Gravel bedding Formworks D. Livestock Trough Concrete Reinforcing Bars Gravel bedding Formworks Total 9.2 Drawings for Rock Catchment Water Facilities Drawings\Rock Catchment\Rock Catchment.pdf m3 kg m3 m2 0.71 10 2.16 4.8 Surface springs occur where groundwater emerges at the surface because an impervious layer of ground prevents further seepage downwards. The rate of flow of water from the spring will vary with the seasons. It is necessary to measure the springs flow at the end of the dry season to determine its potential reliable yield. An inspection of the ground upstream of the spring is essential to ascertain that there is no danger of pollution or, if there is, that measures can be taken to prevent it. A spring source can be used either to supply a gravity scheme or just to provide a single outlet, running continuously, which is set at a sufficient height to allow a bucket or container to be placed below it. To prevent waste, any flow which is surplus to that required for domestic use can be used to irrigate gardens. RATE AMOUNT(Kshs) If the flow from the spring is not sufficient to meet peak demands during the day, a storage tank can be incorpora

Manual for Water Facilities

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