Innovative Water Scheme for Remote Nepalese Community: Raipali village clean water high lift...

7/29/2019 Innovative Water Scheme for Remote Nepalese Community: Raipali village clean water high lift hand-pump install

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EWB-UK Research Conference 2009

Hosted by The Royal Academy of Engineering

February 20

Community of Practice: Water and Sanitation

Author: Aidan Marchand

Institution: N/APreviously published: N/A

INNOVATIVE WATER SCHEME FOR REMOTE

NEPALESE COMMUNITY

RAIPALI VILLAGE

CLEAN WATER HIGH LIFT HAND-PUMP INSTALLATION

TECHNICAL REPORT

EXPEDITIONS

2007 200826TH OCTOBER29TH NOVEMBER 11TH NOVEMBER -2ND DECEMBER

COMPILED BY AIDAN MARCHAND


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CONTENTS

Introduction ...................................................................................................................................... 3

The Challenge .................................................................................................................................... 3

Research and Design ......................................................................................................................... 4

Power Supplies .............................................................................................................................. 5

Preliminary Design Considerations ................................................................................................. 5

Pump Selection .............................................................................................................................. 6

Detailed System Design .................................................................................................................. 9

System Construction........................................................................................................................ 12

Lessons Learned .............................................................................................................................. 14

Conclusions ..................................................................................................................................... 15


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INTRODUCTION

Development work in this area of Nepal was initiated by Richard Backwell in 2003 when trek guide

Bimal Gurung took Richard back to his home village of Okhle after a trekking expedition. Richard

saw the potentially life changing projects that the local villagers were keen to implement withminimal external funding and assistance and he set about raising funds in his home town of

Weymouth. Others have been keen to get involved and since 2003 Richard has been organising and

running expeditions to Nepal involving trekking and an experience of Okhle Village, where group

members contribute to the projects underway. Through the phenomenal effort and achievement of

Richards untiring efforts in Nepal he was awarded an MBE for his work in 2008.

The scope and number of projects has grown since 2003 as more villages have seen what can be

achieved. The expeditions are now run under the banner of Okhle Village Trust and work is

underway in 5 villages, namely Okhle, Raipali, Rbaje, Kot Guan and Ghale. This cluster of villages lie

in the Mahabarat Hills of Northern Nepal at an altitude of approximately 1250m North from Dumreon the Kathmandu to Pokhara road to the north west of Kathmandu. The work underway falls

broadly into three categories of social, infrastructure and education projects which support the self-

development of these communities.

This report covers the technical detail of Raipali Water Project from initiation through design and

implementation to the present time and is intended to provide sufficient information for others to

implement projects utilising similar technology and principles in Nepal or elsewhere.

THE CHALLENGE

The village of Raipali lies on the opposite side of a spur from the spring where the villagers draw

water. Many of the villagers face a steep climb of up to 95 vertical metres up rough steps to fetch

their water. This equates to up to an hour per round trip, to collect approximately 20 litres of water.

The slope on which the steps are poised is so precipitous it is also prone to landslides, one of which

occurred in 2008 during the monsoon and washed a section of path away. Rapaili village is also very

spread out with houses located on the owners farmland which means any water distribution system

will be extensive.

The task of collecting water is not only time-consuming and physically exhausting, it also limits the

time and effort that can be committed to other activities in the village. Raipali is a community of

subsistence farmers and as such is heavily reliant on good harvests and consistency of the monsoon

rains. Having time to develop other skills with the potential to earn money will help the community

develop and be better equipped to survive changes in weather patterns brought by climate change.

In addition, easier access to water would allow the villagers to grow vegetables, as has been seen in

other local villages where water supplies have been developed. These vegetables typically include

spinach, garlic and onions in addition to their staples: rice, corn and millet, to supplement a diet

which largely consists of dhal bhaat (rice, lentils and curried vegetables).

The culture of rural Nepal has a substantial divide between the work of the sexes and the collection

of water is typically done by the women and children, although in Raipali this work is so arduous


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that the men often take water back home after finishing their days work. Water collection is

typically done in the early morning and evening when the air is cooler. Due to the dispersed nature

of the village it is common to see representatives from several neighboring households sociably

coming to collect water together, but rare to see a large proportion of the village by the spring at

the same time. Indeed by virtue of there being only one tap by the spring, it would becounterproductive for too many people to arrive together as this would only further extend the

round trip of collecting water. The social hub of the village is the community centre which is located

centrally and houses most community events such as mothers and fathers committee meetings.

RESEARCH AND DESIGN

In 2006 a project was initiated by the villagers in Raipali to construct a storage tank for water by the

spring to maintain a ready supply throughout the year and provide a buffer for the end of the dry

season when the output from the spring is lower. In this instance Okhle Village Trust provided only

funding and the design and construction was overseen by a local tank engineer. Part of the scope of

this was to construct a tapstand just below the tank, and fed from the tank, to be used for water

collection (Figure 1). The slope of the bank by the spring necessitated three stone gabions to

support the tank and the remaining bank is held back by stepped dry stone walls which the

Nepalese use extensively for stabilising rice terraces.

FIGURE 1: RAIPALI TANK AND TAP AS SEEN IN NOVEMBER 2007


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The problem remained as to how to pump the water into the village and prior to the expedition in

2007 an optioneering study was undertaken to evaluate the possibilities. The following

considerations were particularly pertinent:

Available power supply Daily quantity of water required Height for water to be pumped Cultural fit Time and effort involved in pumping Geographical location of pump and equipment suppliers Spares requirements Appropriateness for village level operation and maintenance (VLOM) System complexity and requirement for specialist assistance Project cost including components, transit, fees, specialist assistance and labour Any necessary bespoke modifications to standard components Practicality of site assembly Delivery timescales

POWER SUPPLIES

It was quickly ascertained that there was no availability of an electrical grid connection, so the

power supply options were limited to local generation by fossil fuels or renewables. Using a local

tractor, small fossil fuelled generators and solar power to drive a pump, were all considered. It was

not deemed appropriate to promote a dependence on fossil fuels where none presently exists and

the village does not have a consistent income to pay for fuel, being primarily a subsistence farming

community. The size and cost of solar panels required to pump water to heights of up to 95 metres

quickly made this option impractical, added to the impossibility of any repair or maintenance and

the perceptions of wealth this would create causing social tensions or vandalism. Hence it quickly

became apparent that it was not presently sensible for any pumping device to be powered but the

option of converting the system to a powered alternative should not be ruled out in the future.

PRELIMINARY DESIGN CONSIDERATIONS

From a technical perspective the key design considerations for the system were the daily

requirement of water, the height for the water to be pumped and the acceptable time and effort

spent pumping to achieve this. As Raipali village is spread down the hillside the villagers must

descend different heights and distances to collect their water, the lowest being almost at the height

of the spring but several hundred metres around the spur. Therefore the effort involved in pumpingmust not be so great that it is still easier for the lower houses to collect their water by hand or the

scheme would be flawed.

Construction facilities at the site by the spring were severely limited with no power tools, limited

hand tools and a steep slope but possible vehicle access. The site for the proposed top tank was flat,

being on a rice terrace, but with poor access along footpaths through fields. In lieu of the limited

site facilities the pumping solution would have to be preassembled or easily assembled on site. A

standard, off the shelf pump was desirable due to proven reliability, low maintenance, availability of

spare parts, easy site assembly and known performance characteristics which all helped mitigate

the project risk.


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PUMP SELECTION

Having ruled out a powered pump, options of either a self powered pump, such as a hydroram

pump, or a handpump were then considered. The hydroram pump uses the kinetic energy of

running water in a supply pipe to induce water hammer, the energy from which is then used to

pump a proportion of the water from the supply pipe up a rising main. The proportion of water thatcan be pumped depends largely on the ratio of the supply pipe static head to the rising main static

head. Simple calculations for a static head ratio of 5 with a typical 50% efficiency of energy transfer

showed that only about 10% of the water at Raipali spring could be pumped up the rising main with

this solution.

There was a possibility that a proportion of the water could be pumped using a hydroram pump butthis would supply no-where-near the water requirements of the village and the remainder would

have to be collected by hand from even lower than before. It was decided that any solution had to

serve the whole community so use of a hydroram pump was ruled out. The most appropriate option

for the present was deemed to be a hand-pump as the villagers currently collect their water by handand the installation of a pump would substantially reduce the labour involved without causing

unnecessary dependence on external factors.

A number of standard deep well handpumps were considered that could pump against static heads

of 50-100m but there were principally three different types:

Reciprocating piston pumps (Afridev (Figure 2), India MkI, MkII)o Reciprocating piston pumps are by far the most common and typically use a

reciprocating handle to move a piston in the pump element to draw water through a

one way valve on the expansion stroke and eject it up the rising main on the

compression stroke.

Hydrostatic pumps (Vernot)o Hydrostatic pumps use the same principle as a reciprocating pump but use a column

of water to transmit the force from the handle to the pump element rather than a

series of rods. The advantage of this is that the pump housing need not be directly

above the pump element.

Progressive cavity rotary pumps (Mono (Figure 3))o Progressive cavity rotary pumps typically use a metal rotor which rotates in a rubber

stator, lubricated by the fluid being pumped, to create a cavity which moves

upwards as the rotor is rotated


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FIGURE 2: AFRIDEV PUMP ASSEMBLY


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It was notable that all standard high lift handpumps were designed as borehole pumps with a pumpelement which is dropped to the base of the borehole and a pump housing and handle which sits at

the top. This configuration was not ideal for pumping from a low tank to a high tank up a rising main

as the main would not be vertical or straight which ruled out the use of most standard

configurations requiring pump rods to connect the pump element with the handle. These pumps

could only be used if the pump housing was capable of being situated at the base of the rising mainand had seals which could withstand the total dynamic head of the system. The system at Raipali

was designed with a pressure rating of 10 bar to allow some flexibility as to the height at which theupper tank was sited allowing for static head and friction losses.

The Afridev and India MkII reciprocating handpumps were considered in some detail but were not

designed for the pressure of a rising main of water to be on the outlet side of the pump and had to

be discounted. This proved to be particularly disappointing as the India MkII is widely used in India

and other neighbouring countries giving excellent local knowledge on the operation and

maintenance of the pump, and also local manufacturers and suppliers for the pump set and spares.

The Vernot pump could be installed in its standard configuration but requires two pressure rated

pipes, one inside the other for the entire length of the rising main. This would prove a costly

solution and one which would be difficult to repair and maintain, hence the Vernot pump was also

discounted.

Following discussions with the manufacturer, it transpired that the Mono design pump housing had

seals that were rated at 10 bar and it could potentially be used with a rising main and pressure head

on the outlet side of the pump. The Mono handpump is now manufactured exclusively under license

by Denorco in South Africa and this raised concerns over local knowledge and spares availability.

However, the track record of Mono handpumps was exemplary with thousands of units sold to the

South African government annually with units operating after 15 years with no maintenance. It wasdecided that the design should progress with the Mono pump; taking the risk of an unprecedented

configuration.

The exact specification of the pump was the best compromise considering the technology available,

the effort involved in pumping and the time needed to pump the water required on a daily basis.

The pump was rated with a maximum dynamic head of 80 metres to give approximately 10 litres

per minute with two people pumping at 1 revolution per second. Although specifying this pump

inevitably meant that those in the top houses still have some 15 vertical metres to descend for their

water, the lower flow rate inherent with a higher head pump to enable gravity feed to this height

made the pumping time prohibitively high.


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FIGURE 3: MONO PUMP ASSEMBLY

DETAILED SYSTEM DESIGN

As a borehole pump, the Mono pump element needed to be submerged and the simplest way to

achieve this was to drop the pump straight through the lid of the cupola topped tank. Unfortunately

this would inhibit access into what is already a confined space and add unforeseen stresses into the

thin walled tank. In order to limit the risk of damage to the existing tank it was decided to fabricate

a standalone pump sleeve, fed from a valved outlet off the tank drain. In this instance the tank drain

had to be used in lieu of another suitably large outlet to maintain water flow to the pump.


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The relative height and orientation of the pump sleeve were also important considerations.

Mounting the pump horizontally eliminated the need for a working slab to be cast on which people

could pump. However, it would also pressurise the interface flanges between the pump and pump

sleeve which were not designed to be pressure sealed. Water pressure on this interface was

eliminated by locating the pump vertically and the interface flange just above the top water level inthe tank.

To keep the pump element completely submerged and be able to drain the tank would require the

top of the pump element to be just below the base of the tank. However, this would require the

pump sleeve to be approximately 3m long which would require a considerably larger excavation and

more substantial retaining walls than was otherwise necessary with the 2m minimim depth from

the interface flange. With a considerable working range and volume in the tank it was decided that

the facility to pump the tank entirely dry was not necessary, and not entirely desirable. Sediment

tended to settle in the base of the tank and was periodically cleaned out. To avoid drawing that

sediment into the pump a raised inlet was installed and the stationary water allowed the sedimentto drop out of suspension before the water entered the pump.

A sightglass was included in the design to ensure there was sufficient water in the pump sleeve to

keep the pump submerged whilst pumping. There was a noticeable drawdown of the water level in

the pump sleeve, even with a 2 feed pipe and 1.7m of head from the tank when full. The sightglass

had to be open to the atmosphere to give a true tank level and capped off to prevent insects and

debris entering.

The valve chamber was designed with a non-return valve in the water meter just after the pump.

This arrangement allows the head of water in the rising main to sit against the valve rather than the

pump and prevent any backflow through the pump. This allows the pump to be removed without

draining the rising main and was also a mitigation measure for any slow leaking pump seals which

would then only weep whilst pumping rather than constantly. A valved washout was inserted just

after the non-return valve to allow the rising main to be drained for cleaning and maintenance

(Figure 4). The rising main itself was deliberately oversized and designed with a generous pressure

rating to minimise friction losses and allow for much higher flow rates if a powered pump were to be

installed instead of a handpump.

The civil work for the project used local materials and skills extensively: rocks from the hillside,

aggregate from broken rocks, sand from the river and dry stone walls where possible.


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FIGURE 4: VALVE CHAMBER LAYOUT

An allowance was made during planning to have a single pump valved onto two rising mains each to

a separate tank. This would permit one tank to feed the lower part of the community and the other

the upper part so that water to the lower part of the village would not be pumped unnecessarily

high corresponding to wasted effort. This option gave more flexibility about where the tanks could

be sited, and should this option not be exercised, there would be an additional valved outlet for

future expansion of the system. In fact the second rising main was not used due to the layout of the

village which would have resulted in high costs for limited benefit.

The 175 metre length of rising main and 75 metre height difference between the two tanks meantthat it would be difficult to know how much water had been pumped. A small domestic water meter

was installed in the valve chamber so that the volume pumped could be monitored. This would also

allow the villagers to monitor their usage and to determine the amount of water to be pumped on a

regular basis. Individuals could then be allocated a certain proportion of that amount to divide the

labour fairly.

The locally available materials for the construction of the rising main were either galvanised iron

(GI) pipe in 6 metre lengths or High Density Polyethylene (HDPE) pipe in coils of up to 100 metres.

The decision was taken to use HDPE pipe due to the ease of installation, low number of joints (1

HDPE compared to 30 GI!) and increased flexibility. Leaks were of particular concern due to the high

Rising

Main

Meter and

Non-Return

Valve

Wash

Out

Capped

Main for


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pressure of this system (75m head, 7.4 bar). The standard GI threads were seen to be poorly cut and

leaks are very common.

The standard way of joining HDPE pipe locally was to heat up a steel plate in a fire and press the

ends of the pipe against the plate until molten when the plate can be removed and the ends fused

together. This caused concern for use on a pressurised system due to the uncertain quality and

consistency of the joints, potentially with impurities in, and the potential constriction of the pipe

bore as the ends are pressed together, leading to higher friction losses. To mitigate this risk, good

quality compression fittings including valves (Plasson) were sourced and taken from the UK.

SYSTEM CONSTRUCTION

The Raipali water project began in 2006 with the construction of a nominal 20,000 litre tank next to

the spring to contain a buffer of water for later in the dry season. In 2007, two engineers from Okhle

Village Trust worked with the Raipali villagers and carried out the civil groundwork to install a pump

sleeve, fed from the tank, that would house the selected Mono design pump. (Figure 5).

FIGURE 5: COMPLETED CIVIL GROUNDWORKS IN 2007

The excavation for the pump sleeve proceeded with caution due to uncertain soil stability and

consistency behind the existing dry stone walls. This caution was justified as below approximately

400mm depth the ground was weak and unconsolidated with mixed rubble, soil and air spaces. This

ground was evidently the result of untamped backfill behind the dry stone walls at depth, with the


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surface compressed by human passage. In order to construct a secure platform for the pump and

hold back the bank, a stone and mortar wall was constructed and backfilled with concrete.

During construction it was found that the cement was of poor quality and took several days to go

off and a considerably period of time to reach full strength. The standard grade was nominally

52N/mm but was thought to offer lower strength in reality. This impacted on the speed at which

the walls could be built as too much weight above crushed the mortar from between the stones

before it could go off. Such was the concern for the top slab, which would support the people

pumping, that a higher grade of cement was used which was nominally 55N/mm. This approach

caused its own problems as the 55N/mm grade went off extremely fast and caused difficulties

mixing and laying the concrete fast enough.

The pipe to feed the base of the pump sleeve required flexibility in alignment as the orientation of

the tank and pump sleeve outlets were, almost inevitably, not orthogonal. Leaking joints on

galvanised iron pipes were sent away to be welded but returned still leaking due to dirty materials

and poor quality welding.

The scheme design and procurement of key components was undertaken in the UK to mitigate the

risk of being unable to source components of suitable quality and functionality locally, and in a

timely manner. The chosen Mono pump is now manufactured exclusively by Denorco for Orbit

Pumps in South Africa. Mono pumps in the UK has the rights to distribution in Europe. The initial

idea was to procure the pump in the UK from Mono, manufacture the pump sleeve, and test the

functionality of the pump before shipping to Nepal. This approach reduced the project technical risk

but we would be liable to pay UK VAT on the import as Inward Processing Relief (IPR) was not

available for products sold in the UK. The cost of this approach was considered excessive, especially

as an import duty of dubious magnitude was also due in Nepal.

During the 2008 expedition the hand pump was installed and tested, the valve chamber and rising

main were completed and a site for the upper tank was excavated ready for construction after the

harvest. The valve chamber was constructed with a thin screed floor drained to a pipe in one cor ner

and dry stone walls to allow water to pass through the chamber rather than apply a hydrostatic

force to the chamber walls. A weak, wet cement mix was poured over the dry stone walls to offer

some bonding and the welded lid frame was set in concrete to give a solid top to the chamber. The

lids themselves were carefully sized to ensure they could be lifted by a single villager and a

reinforcement bar slotted through cast-in hoops to secure the chamber.

The rising main was buried to prevent damage, minimise thermal transients and to prevent direct

sunlight on the black pipe. The lower section of the pipe was rated at 10 bar to resist the high

pressures at depth whilst the upper section at 6 bar to reduce pipe costs by using a thinner walled

pipe where the pressure was lower. Care was taken to avoid kinking the pipe or laying it over sharp

rocks and the terraced landscape through which the pipe ran had to be broken down to give a

smooth incline. This reduced the friction losses, the length of pipe and consequently also the

pumping effort. The buried pipe was covered, using rocks in such a way as to prevent the monsoon

run off following the course of the pipe, causing landslip, and exposing the pipe.


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During installation, test pumping was undertaken to check the pump performance and resistance

with different static heads of water, and to locate the optimum position for the upper tank. This

strategy was deliberate to ensure that the pump and the villagers pumping could comfortably pump

to the required height to reach the tank. By siting the upper tank on the basis of the pump

performance in situ, the risk of constructing a tank in an unachievable or non-optimal location wasmitigated. The top tank was eventually situated 75m above the lower tank on the nose of the spur

at the highest point in the pipe system to prevent air accumulating in local pipe crests.

Water quality testing was also done to ascertain the quality of water at source, after storage and

after being pumped. The quality at source was found to be excellent but storage in ferrocement

tanks had the effect of raising the pH. This was not to an unacceptable level but benefit may be

reaslised in this region in the future by using additives in the tank cement mix to counter the

alkalinity of the cement. However, this phenomenon could also be of mild benefit in areas with

acidic soils.

LESSONS LEARNED

o The duty payable on imported products is not necessarily consistent or easy to quantify inadvance and may represent a substantial proportion of the value of the product.

o The quality and strength of materials is not necessarily that which is quoted and materialsof the desired quality may not be locally available. Steps should be taken to design out the

need for high quality and strength materials or a reliable source must be found.

o The accuracy of machine tools is limited and steps should be taken to design out thenecessity for high accuracy or make alternative arrangements to guarantee the requiredaccuracy.

o Design information provided by local villagers may not be accurate, dimensions arefrequently guessed, units mixed and statistics on usage of water and other commodities

may be tailored to please. Cross checks should be run and if design information is

unavoidably critical it must be verified.

o Stick welding is widely available but other forms of welding are not and the quality of weldsis dubious. Eye protection is rarely adequate.

o More specialised pipe components such as flexible couplings are generally not available andsteps should be taken to design out the necessity for flexibility in angular alignment in

construction or maintenance of pipework. If angular flexibility is required the flexible

couplings may have to be imported.

o The construction site and completed project may be subject to vandalism and theft andshould be designed robustly and with as much fault tolerance as is practicable. Valuable

assets should be able to be locked away.

o Be prepared for weak soil in areas of previously disturbed ground.


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o Procedures to improve quality should be impressed upon the local workers before andduring fabrication operations and constant supervision may be required along with the

provision of measuring equipment.

o Capacity for expansion and modification in the future should be allowed. If possible systemsshould be designed to allow a different source of power to be used with minimal

modification.

o In general the cost of mitigation measures should be in proportion to the significance of theperceived risk. However, if risks are identified that will leave the local community with an

incomplete or non-functional system which they are not capable of completing themselves,

mitigation measures of considerable cost may be appropriate.

o The construction sequence should permit maximum flexibility and allow the areas ofgreatest uncertainty to be addressed early on.

CONCLUSIONS

The installation of this Mono design handpump in Nepal represents the first known installation of

this type of pump in the region and the first successful use of this pump at the base of a rising main

rather than as a borehole pump, thus proving the concept for future use on other water schemes.

The ongoing work includes construction of a government standard design upper tank and

installation of the distribution system to tap-stands, which the local community is fully capable of

completing without external assistance.

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