Manual - Home | K4Health · Web viewUse it as a reference. (Turn on the document map in Word: View -> Document Map; in Adobe turn on your bookmarks.) First things first Who’s who

Notes on Manual Well Drilling in the Altiplano

A Compilation of Experiences from B-39 BS Volunteers

July 2007

Introduction..........................................................................................................................1

First things first....................................................................................................................2

Who’s who.......................................................................................................................2

UNASBVI (Unidad de Agua, Saneamiento Básico y Vivienda)................................2

JICA (Japanese International Cooperation Agency)...................................................2

Sumaj Huasi (SH)........................................................................................................3

The Baptists.................................................................................................................3

Carlos...........................................................................................................................3

Hector Lobo.................................................................................................................3

An introduction to your rigs and pumps..........................................................................4

The Rigs.......................................................................................................................4

The Pumps...................................................................................................................5

Seasonal calendar and how it affects you........................................................................7

Planting........................................................................................................................7

Harvesting....................................................................................................................8

Rainy season................................................................................................................8

Dry season...................................................................................................................8

Get to know the terrain....................................................................................................8

Budgeting.............................................................................................................................9

Considerations for 2007...................................................................................................9

Considerations for 2008...................................................................................................9

Estimated Costs...............................................................................................................9

Procuring Materials...........................................................................................................12

Working with the Prefectura..........................................................................................12

Working with the municipal government......................................................................12

Where to buy..................................................................................................................12

Some notes on specific materials...................................................................................13

Organizing.........................................................................................................................15

Deciding where to drill..................................................................................................15

Pre-drilling preparations................................................................................................15

How to get people to show up.......................................................................................16

Driling................................................................................................................................18


Transportation................................................................................................................18

Locating the well...........................................................................................................18

Starting your borehole plumb........................................................................................19

Drilling mud...................................................................................................................19

Circulation pits...............................................................................................................20

Caving............................................................................................................................21

How to know when you’ve hit water.............................................................................21

Fishing...........................................................................................................................21

Some notes on Baptist drilling.......................................................................................22

PVC versus galvanized drill stem..............................................................................22

Galvanized header pipe..............................................................................................23

Tying off your drill stem............................................................................................24

Widening your borehole............................................................................................24

Some notes on ASVI-JICA drilling...............................................................................24

Difficult terrain..............................................................................................................25

Rocky layers..............................................................................................................25

Loose gravel formations............................................................................................26

Pressurized sand aquifers...........................................................................................26

Well Installation and Development...................................................................................27

Screen preparation.........................................................................................................27

Screen length.............................................................................................................27

Screen design and placement.....................................................................................28

Filter...........................................................................................................................28

Screen and Casing Installation.......................................................................................28

Cleaning.........................................................................................................................29

Sand or gravel fill..........................................................................................................29

Well Development.........................................................................................................31

Overpumping.............................................................................................................31

Surging.......................................................................................................................32

Restorative development...........................................................................................33

Sanitary Seal..................................................................................................................33

Pumps and Wellheads........................................................................................................34


Pumps............................................................................................................................34

Baptist Pump Installation...........................................................................................34

AYNI Pump Installation............................................................................................35

Modification for Sand Pumpers.................................................................................37

Wellheads......................................................................................................................37

Capacitación......................................................................................................................39

Beneficiarios..................................................................................................................39

Técnicos.........................................................................................................................39

A Plea for Documentation.................................................................................................41

References and Resources.................................................................................................42

Appendix A: More on sand or gravel fill...........................................................................43

Gravel pack installation.............................................................................................43

Gravel pack particle size............................................................................................44

Appendix B: Case study from Pampa Aullagus................................................................46

Appendix C: Making cups leathers....................................................................................47

Appendix D: Working with Concrete................................................................................48

Appendix E: Driller’s Vocabulary.....................................................................................49

Geology and soils......................................................................................................49

Tools and materials....................................................................................................49

Drilling and installation.............................................................................................50

Introduction

After initial success with Baptist drilling in Santa Cruz, Tim McFarren decided that it was time to make inroads in the altiplano; in 2005 five B-39 BS volunteers were sent to Oruro. One began working with the nascent Baptist-drilling program in Pampa Aullagus. The other four were charged with beginning Baptist-drilling programs from scratch in their municipalities. We have learned a lot, but didn’t accomplish as much as we hoped. We leave behind this document in the hope that B-45 drillers can build off of what was learned…and accomplish a lot.

If you are just beginning to drill, read through Terry Waller’s “Baptist Well Drilling in Bolivia,” available on the Yahoo!Groups basicsan2 site. Regardless of whether you are using the Baptist rig or a rotary rig, Terry has a wonderful perspective on empowering rural families to address their water scarcity problems:

We want knowledge of well drilling in our area to become common as mud. The ideal is for each rural family to have a shovel, machete, hoe, and well drilling rig in the back shed. When he wants a well he simply calls his neighbors and they go drill one. (Baptist Well Drilling in Bolivia, 3)

We are still very far away from this as we take our first baby steps in the altiplano. We seem to be very far away from it indeed as we foster a dependency on the departmental government and play into the handout economy that is so common in the altiplano. As you drill, keep Terry’s philosophy in mind; only when local people see the value of this technology and take it up for themselves will water scarcity be truly eradicated.

Paraphrasing another driller in Santa Cruz, manual well drilling best resembles “a drunken dance”. You will figure it out as you go along, based on your failures and successes, so we haven’t even tried to explain how to do it in this document. Instead we have focused on logistics and contacts and have tried to reiterate some of the important technical points that may have been glossed over in training. There are also some unresolved issues about how to drill and install wells in the altiplano; this document will tell you where we left off in addressing them.

This is definitely more information than you will need to get started with well drilling. Use it as a reference. (Turn on the document map in Word: View -> Document Map; in Adobe turn on your bookmarks.)

Introduction

1


First things first

Who’s whoUNASBVI (Unidad de Agua, Saneamiento Básico y Vivienda)

This is the basic sanitation branch of the prefectura. Their office is on Pagador near Aldana (Caddy-corner to the restaurant Nayjama). The técnico’s office is on the first floor. Peace Corps volunteers typically meet with UNASBVI employees the first Friday of every month. Primary points of contact for the well drilling project are:

Ing. Ariel Tapia Velasco, Coordinator of the project ASVI-JICA II: Ariel is a good place to start if you need tools or materials.

Ing. Juan Carlos Illanes: Engineer in charge of having our second tripod-based drilling rigs made. This rig was originally envisioned as a combination of the Baptist system and Hector Lobo’s system (see below), but now it has become unclear what will be delivered.

Ing. Jose Ayala Miranda, Jefe de UNASBVI: Occasionally meets with volunteers at the monthly meetings.

UNASBVI’s técnicos are not experts on well drilling. Their primary function is to provide the materials necessary for drilling and to teach people how to use the drilling rigs (which usually consists of a single taller in the community). With respect to our project, UNASBVI has earned itself a reputation for preposterously long turn-around times for the provision of promised materials.

An ongoing project at UNASBVI is ASVI (Agua es Salud y Vida); its current manifestation is ASVI-JICA II in collaboration with JICA. Under the 2006 (effective in 2007) convenio between ASVI-JICA II and the municipalities the prefectura is donating 40 complete pumps (any combination of AYNI and YAKU pumps). Verbally they have agreed to give AYNI pumps for any wells drilled above and beyond the 40.

In June 2007 UNASBVI was finalizing their design for letrinas ecologicas. They will be implementing this project preferentially in municipalities with Peace Corps volunteers.

JICA (Japanese International Cooperation Agency)

This agency works closely with the prefectura. It has provided large mechanical rigs that are used to drill 6-inch diameter community wells through the project DASAR-JICA, but it is also coordinating with UNASBVI on the manual rigs. DASAR-JICA’s office is located across the hall from the UNASBVI técnicos. They have a water quality lab that they have agreed to use to test samples from volunteers’ wells when needed. The engineers may also be able to provide support on technical issues.

UNASBVI typically stores materials at JICA’s garage. It is located at Calle Tacna y Campo Jordán. Heading down from the bus terminal on Villarroel, turn left on Tacna, continue past the gas station. Garaje JICA, a blue garage door with JICA’s logo, is on the right.

First Things First

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Sumaj Huasi (SH)

This organization spearheaded a well drilling program in the altiplano in the past working with OPS (Organización Panamericana de la Salud). You will probably run across some of their wells in the field. Their philosophy on sustainability was to train well drillers and have them start drilling micro enterprises but apparently they didn’t put much emphasis on this aspect of the program and it met with little success in the altiplano. However, they did have success with drilling, even in rocky terrain, which shows us that it is possible. SH claims to have drilled 5000 wells in Bolivia with manual rigs; their deepest in the altiplano is 72 meters deep. The rotary drilling rigs that you will find in your sites are knock-offs of the SH rigs and the AYNI pump is an outdated version of the pump that SH installs.

If you have questions about drilling or the AYNI pumps Alfredo Terrazas ([email protected]), SH’s well drilling coordinator, is very willing to help. SH’s office is located in La Paz, Landaeta 533, near the corner of Abdón Saavedra. It is a few blocks up from the Plaza del Estudiante. Tim knows SH’s director Oscar Suntura ([email protected]) well and can help you get in touch. Contact numbers for the office: tel (2) 2493947, fax (2) 2116098. At present SH is not drilling in the altiplano but it may be worthwhile to get in contact with them and find out if they will be so that you can round out your training by drilling some wells with them. Tim has also talked with Oscar about the possibility of setting up a drilling taller with SH and Peace Corps’ drillers.

The Baptists

Terry Waller is a Baptist missionary that has lived for several years in San Julian in Santa Cruz. The Baptist drilling system is Terry’s brainchild and with it thousands of wells have been drilled in Santa Cruz. They have now taken the methodology to Nicaragua and several countries in Africa. Terry’s website is http://www.geocities.com/h2oclubs/. Contact numbers for the folks in Santa Cruz are available in Mike Riley’s and Gerid Buckshire’s activity packet on the Yahoo!groups site. Teo Belmontes is usually the point man for well questions. Terry is now more involved with other projects. Ben Ranz, the PC volunteer in Hardeman is in contact with the Baptist drillers and would be a good way to get in touch.

Carlos

Ken Karthner (callsign Carlos) was a B-30 basic sanitation volunteer. He is an engineer with 6 years of well drilling experience in the States. He is a great reference to us because he knows a lot about how wells are drilled and installed in the States but also understands the realities of working in the Bolivian campo. He can be reached at [email protected].

First Things First

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http://www.geocities.com/h2oclubs/

https://www.fastmail.fm/mail/?MLS=MR-**4*;SMB-FT-TP=0;SMB-MF-SF=Date_1;SMR-MI=4;SMR-PT=;Ust=f0f71b22!812241a6;SMR-FM=1;SMB-CF=7919221;SMB-MF-DR=10;UDm=49;MSignal=MC-FromName*U-1*[email protected]

mailto:[email protected]


Hector Lobo

Hector is a well driller based out of Challapata. He uses a rotatory-percussive drilling method that is similar to SH’s method, but he uses a set of innovative brocas that have an open-topped cylinder at the base. Hector claims that larger rocks that can’t be lifted out of the well with the drilling mud fall into the cylinder, thus allowing him to pass otherwise impenetrable formations.

Hector has also implemented several other innovations on his rig, including a means of reinforcing galvanized pipe joints for the drilling stem. In 2006 UNASBVI was exploring possibilities of working with Hector in the design of new drilling rigs for volunteers, but apparently nothing came to fruition.

An introduction to your rigs and pumpsIf you are placed in one of the B-39 well drilling sites you will probably have two well drilling rigs waiting for you, the Baptist rig and the ASVI-JICA (or rotary-percussive) rig. Your municipality will also be part of a convenio under which the prefectura will provide the municipality with AYNI and YAKU pumps.

The Rigs

Baptist rigA modification of the Baptist system used in Santa Cruz, this rig uses the tripod system, PVC drill stem and reverse circulation (mud poured down the hole and spit out of the stem) with a tongue and dart drill bit.

First Things First

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Figure 1: Don Hector's brocas


ASVI-JICA rigThis is based on the SH rig and uses a bipod, galvanized drill stem and standard circulation (mud pumped down to the base of the well, exiting from the bit).

Figure 4: ASVI-JICA bipod Figure 5: ASVI-JICA broca

The Pumps

Baptist pumpsIn 2006 we were working exclusively with Baptist pumps (and rigs). You may still have some materials left over available for use. Baptist pumps could conceivable be phased out if the prefectura keeps donating AYNI pumps, but Baptist pumps have some advantages that should be kept in mind:

1) They are made entirely of cheap and simple materials, available at any hardware store, making it easy for the users to understand and repair them.

2) Because there are set up with a lever system they could be better for deeper wells, where the weight of the water column makes bicycle pump style hard to lift.

First Things First

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Figure 2 (above): Baptist broca

Figure 3: Erecting Baptist tripod


3) The AYNI pumps use check valves at the base of the piston. If you have trouble with fine sand infiltrating into your well there could be a high failure rate for this component, which will be more expensive to replace than the components of the Baptist pumps

AYNI pumpsThis is prefectura’s alternative for drilled wells. Most of the components are comparable to the Baptist pumps, except they use a check valve at the base of the small politubo, which sends water up the small tube (instead of the annulus between the small and large politubo as in the Baptist pump). They also use the bicycle pump style handle. Some of the advantages of the AYNI pumps:

1) These come with a metal wellhead so you don’t need to worry about protecting the PVC from the sun

2) They provide a good flow rate

3) They are free (at least for now)

YAKU pumpsThis is the prefectura’s pump for hand dug well (i.e., norias, wells dug with shovels, typically with a diameter of approximately 1 meter). The pumps are made entirely of specially fabricated components, but there is a taller in Oruro where users may be able to buy replacement parts (Winger S.A., Dirección: Kennedy 7782 y Pasaje 2, Tel: 528-7123, 704-28943, Contact: Zenon Soria Galvarro, Note: The last time I talked with Don Zenon he claimed that the only part on the YAKU pumps that wears out is the thin rubber flap at the top of the piston. He says that this can be replaced with goma cut from a tire inner tube.). Some advantages of norias and YAKU pumps:

1) If for some reason you can’t drill well, these shallow wells serve as an alternative. Many people already have norias that can be modified/deepened for the installation of a YAKU pump.

First Things First

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Figure 6 (left): Finishing a Baptist pump

Figure 7: Baptist piston


2) The pumps provide a good flow.

The primary disadvantage of norias is the need to line the wells:

All wells, except those drilled thorough rock, can be expected to cave in with time unless a lining is installed to support the wall. (Wells Construction, 27)

Traditionally bucket-served norias have been left unlined and could be dug back out if they caved in. However, once a concrete slab and pump have been installed, a caved well is more likely to be abandoned than rehabilitated. Unfortunately, installing well linings is a project that many municipalities aren’t prepared to do because municipalities tend toward short sightedness (at least based on my experience in Corque) and because linings can greatly increase construction cost and time.

If you will be working with the installation of YAKU pumps, try to make well linings an integral part of the project. Some things to consider:

Meter-for-meter lined norias are more expensive than drilled wells.

Linings can be concrete rings, stone, or brick.

Using concrete rings can help you dig further into the water table. Because norias are shallower they can be more susceptible to seasonal fluctuations in the water table, so deeper is better.

Norias typically only tap into the unconfined aquifer and should be avoided in regions where this aquifer may be subject to contamination (typically not a problem in the altiplano).

This manual does not address hand-dug wells. The best reference to help you get a handle on the particulars is Wells Construction: Hand Dug and Hand Drilled, available in the Cochabamba library.

Seasonal calendar and how it affects youBasic sanitation volunteers get to site the beginning of August, which is during prime drill season. It may be possible to hit the ground running if the previous volunteer has already done some of the coordination. As the year progresses be aware of the weather and how it affects people’s workloads. Ignorance of the seasonal calendar can cause much undue frustration. On the other hand, don’t automatically discount any season – an excited populace will make time.

There is a strong possibility that there will be months of the year during which you will be unable to drill. Plan secondary projects to fill these gaps.

Planting

(End of September to December): If people really want wells they should be able to organize drilling around the planting. In Corque people originally told that no one would be able to work after September 21st because they would be busy working in the fields, but motivated groups kept working until December. Also keep in mind that though they may have already planted, after the crops sprout community members may be busier than usual watching their livestock so it doesn’t eat the crop.

First Things First

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Harvesting

(March through June): The most intense workload is during this period. Coupled with the low population common in rural communities, this can potentially mean no well drilling.

Rainy season

(December/January through February/March): Drilling will depend on the quality of roads, whether you have to cross riverbeds to get to the drill site, how close to town it is, among other factors.

Dry season

(April through November): Prime drilling season, especially after the harvest is complete in June. In Corque everyone starts coming out of the woodwork at the end of April.

Get to know the terrainAs you start planning to drill ask the local population about the terrain. People generally have an idea of what to expect because they have dug norias in the area. One rule of thumb as you get started: drill the easy boreholes first (especially as you are getting acquainted with your rigs). Trying to drill in hard terrain or deep wells is valiant but you will garner more support for the project by actually getting wells in the ground.

You can also get a good idea about terrain and the depth to the water table by looking into existing norias. Bear in mind that this doesn’t tell you how deep you need to drill because although the water table could be at 3 meters this could be followed by meters of pure clay. Other drilled wells in the region are a much better indicator of anticipated depth.

JICA may be able to provide geologic data if you want to drill in the same region as one of their wells. This consists of a geologic profile (columna litologica), an electric log (registro electrico), water quality and pump test data for the well. Ing. Mario Ramírez, coordinator of the DASAR-JICA project, has provided this data in the past. His office is located on the second floor of the UNASBVI building.

If there are no existing wells or norias in the region try to look at the lay of the land. Generally speaking, the pampa in the altiplano has a very shallow water table. In hilly regions the water table will typically be shallower in the valleys. Areas near bofedales (wetlands) or riverbeds should also have easily accessible water tables. Vegetation can also be an indicator of groundwater.

First Things First

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Budgeting

In 2006 the setup was simple: UNASBVI provided all the drilling equipment and the municipal government provided all of the material for the wells and Baptists pumps. Volunteers had to fight the convoluted battle to be included in the POA. The convenio with the prefectura has simplified the matter considerably for 2007.

Considerations for 2007The 2007 convenio between ASVI-JICA II and the municipalities stipulates that the municipalities include funding for the well project in their POA. Therefore you should have money or materials waiting for you when you get to site. The convenio states that UNASBVI will donate 40 complete pumps (any combination of AYNI and YAKU pumps); verbally they have agreed to give additional AYNI pumps for any additional wells drilled. Therefore, POA funds are available for transport, purchase of any materials that weren’t donated (such as bentonite), and linings and tops for hand-dug wells.

Bear in mind that if there are unused funds in the municipality’s POA at the end of the year they can be used to buy materials during the first month of the following year.

Considerations for 2008Toward the end of 2007 the POA for the following year will be written and you want well drilling to be in it. The amount required will be dependent on what the prefectura will be providing in 2008. If the municipality signs a convenio with UNASBVI that is similar to the 2007 convenio, funding for wells may be automatically included. If not, the municipality may want you to write a project or at the very least a budget in order to be included in the POA. Often what needs to be done after that isn’t entirely clear. Your best bet is to integrate with the técnicos in the alcaldía, provide them with the data that they need and have them take care of the rest.

Estimated CostsTable 1 includes a sample budget for a 20 well project with Baptist pumps, assuming a well depth of 24 meters. Prices are based on 2006 purchases.

Budgeting

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Table 1: Estimated costs, 20 Baptist wells with pumps

Quantity Item Unit Cost (Bs.) Total Cost (Bs.)

5 Politubo 1 1/2" (Rollo 100mt) 1595.00 7975.00

5 Politubo 1/2" (Rollo 100mt) 500.00 2500.00

80 Tuberia 2" Clase 9 x 6mt 89.00 7120.00

1 Litro Pegamento Plasmar 53.00 53.00

20 Chupador 1" 32.00 640.00

20 Niple 1" PVC Rosca 2.00 40.00

20 Copla 1" PCV Rosca 3.20 64.00

20 Tee 1 1/2" 31.00 620.00

20 Barilla con "U" 34.00 680.00

20 Perno 3/8" x 6" 1.38 27.60

40 Perno 3/8" x 4" 1.20 48.00

100 Volanda 3/8" 0.15 15.00

40 Tuerca 3/8" 0.20 8.00

20 Tuerca de Seguridad 1.50 30.00

15 Cinta Aislante 10.00 150.00

20 Niple 3/4" PVC Rosca 1.20 24.00

20 Copla 3/4" PCV Rosca 2.10 42.00

30 Yute 4.50 135.00

8 Litro Clefa 32.00 256.00

40 Empaquetadura de goma 2.00 80.00

20 Tapa de goma 1.00 20.00

40 Abrazadera 4.00 160.00

10 Bentonita 80.50 805.00

1 Bolsa clavos 10.00 10.00

20 Poste y palanca 20.00 400.00

15 Cemento 43.00 645.00

Total Cost: 22547.60

Budgeting

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The cost per Baptist well (with assumed depth of 24 m) is approximately $140 with a cost per meter of approximately $6. You may note that this is considerably higher than Terry Waller’s 2003 estimate of $2/meter. Apart from inflation this difference may be because Santa Cruz wells are typically deeper, or due to the quality of the tubing purchased.

In 2006 altiplano drillers bought all Plasmar pipe, which is the highest quality available, but as a result tubing accounts for more than three quarters of the total cost. There are several grades of politubo available and a wide range of costs. Because the large diameter politubo isn’t exposed to the sun (with the exception of the spout and riser pipe for the Baptist pump) or repeated stress it may be feasible to use a lower grade. However, cheaper politubo can be much more difficult to work with. It tends to crack instead of stretch when heated and is more difficult to thread. Imperfections in the large diameter politubo can also make it difficult to install your piston. Unfortunately, the politubo donated by the prefectura in 2007 is of a lower grade so you will have to work with it this year. If volunteers are persistent they may be able to convince the prefectura to buy Plasmar pipe in the future.

With respect to the PVC casing, Clase 9 is the lowest grade we are comfortable using. A previous volunteer experimented with desagüe pipe, but some of some of those well casings collapsed over time.

Estimated costs for the pumps donated by the prefectura are included in the following table, as per the UNASBVI técnicos.

Table 2: UNASBVI Pump Costs

Item Total Cost (US$)

Bomba AYNI 160.00

Bomba YAKU 180.00

We can’t directly compare the price of the AYNI pump to the Baptist pump because the técnicos don’t seem to know the assumed depth per well. It is slightly disconcerting that the AYNI price is so high despite the purchase of low-grade politubo. This could be due to the welded metal components, the use of check valves, or the length of tube per well.

Budgeting

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Procuring Materials

Working with the PrefecturaIn 2007 the prefectura is theoretically responsible for providing all necessary materials for the drilling rigs and pumps. If you need something that they haven’t provided, you can write a solicitude requesting it. If you need something urgently you may want to try working through the municipal government because the prefectura can be very slow on purchases. Constant nagging and baking the prefectura técnicos cake are the only strategies that I have developed to speed up the process. If you need a small item they may have money available in their “caja chica”.

Working with the municipal governmentIf your counterpart agency is the alcaldía, try to make them completely responsible for purchasing materials. First off, they will get better prices than you, and secondly, they have the means to transport it. Your responsibility is to “solicitar” the items and justify why they are necessary and possibly to obtain quotes. If you attempt to purchase items on your own things can get complicated, whether you have the alcaldía cut you a check prior to the purchase or you ask for reimbursement.

In Corque the alcaldía needs three quotations for each item to be purchased. The tricky part is that all the same items need to be quoted in the same order for three stores. That would work if we were going to building-supply stores in the States, but in Oruro most stores carry a few specific things; one store may have 5 items from your materials list but another may have only 4. Somehow this doesn’t jive with the alcaldía’s bookkeeping. As a go-around they fabricate quotations that match up with the quote sheet of the store they will buy from using blank forms that they have induced someone to stamp and sign (but not before giving me a hard time about not getting quotes correctly). My recommendation would be to do the quotes with an alcaldía staff member if at all possible.

Transport can be problematic, especially if buying large quantities of tubing. Your best bet is to make this the alcaldía’s responsibility. If you are working with a different counterpart agency here are some other possibilities:

Ask at the mayor’s office if you can piggyback your materials into a truck that is bringing materials for another project to town.

UNASBVI may be able to help if they are planning a visit to your site.

If you have enough money budgeted, rent a truck.

Where to buyThe following lists the stores we frequent:

Augster (Adolfo Mier, half a block up from the main plaza): This is the factory outlet for Plasmar products including PVC Clase 9, politubo, PVC accessories including nipples and couplings, and pegamento de PVC. They also carry chupadores.

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Colmena (527-7354, Caro esq. Brasil): They carry a very good selection of high quality tools. If you can’t find something anywhere else try Colmena, but be prepared to pay a mint.

Comercial Gaviota (527-3272, Av. Ejercito esq. Brasil): They sell PVC Clase 9, politubo, accessories for PVC, electrical tape, foot valves and some tools.

Ferbo (Murgia y Velasco Galvarro, by the train station): They have excellent tool prices, especially on the Mexican brand Truper. They also have electrical tape and galvanized pipe and fittings. B-39ers recommend them for good customer service.

San Augustín (Ayacucho No. 244, near Pagador): Metal pipe fittings.

Some notes on specific materialsBentonite: The owner of Electromar (esq. Cochabamba y Pagador) had some bentonite to sell at a premium (120 Bs. per bag). Unfortunately, I bought some very poor quality mud from him. He had bentonite for drilling and for setting posts but they were in identical bags, and I believe he mixed them up. A much better option, especially if you are buying in quantity, is to buy from the factory Materiales Industriales (527-8019, open Monday through Friday, to the right immediately after the cuartel on Carretera Vinto, blue(?) sign). Tell them it is for well drilling. I bought very high quality mud for $10 a bag.

Brocas: The prefectura provides brocas, but if you want a special broca made you can visit the taller de soldadura of Simón Gómez Fuentes, at Backovic No. 1855, between Murguía and Aldana, tel: 527-5425. Don Simón does quality work and has been making brocas for volunteers since B-33.

Clefa: It can be found in Barrio Chino, but if you need a receipt you can buy it at some of the paint stores on Pagador between Junin and Ayacucho.

Cup Leathers: You can buy cup leathers for air pumps at the carts near the intersection of 6 de Agosto y Bolivar. These aren’t soaked in paraffin as is usually recommended for water pumps, but Jacob installed some in Huari and they seem to be working; sustainability not yet determined.

Empaquetaduras de goma: Several gomerías are located on Tacna between Caro and Montesinos. I typically go to Pedro Alvarez’ taller at Tacna No. 7007. You may want to shop around for someone that does better quality work and is better at meeting deadlines.

Goma para amarrar: Sold at Tarapaca y Bolívar, below Mercado Bolívar.

Gravilla: If you want to but gravilla for a filter pack you can try Constructora Arteago at the Circunvalación, about a block from esquina Ejercito. They sell a fine gravilla (which they call “clip”) by the cubic meter.

Leather: “Cuerina” is the type that seemed to work best for making your own cup leathers. It can be hard to find in Oruro. Try the leather and fabric shop near Fermin Lopez. Alternately, thicker leather can be bought at shoe repair stands or at some leather shops. Thicker leather can easily be cut/filed into ring gaskets.

Procuring Materials

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Llave estilson: Buy Truper brand llaves. Do not buy aluminum llaves because they break.

Metal scrap etc.: Mercado Antacatu (Iquique entre Sucre y Bolívar) has scrap metal, used pipes, turriles, miner’s barretas if you are making your own brocas, and other various items. Bargain hard.

Motobombas: I was told that Cbba pumps were cheaper. In Cbba the store recommended to me wass Agencias Generales S.A. (425-1062, Bolivar E-520). Within a few blocks there are several other stores. In Oruro Colmena had the best price (Honda 2” 5hp, Korean manufacture, 1 yr guarantee for $316). [Brief aside: The prefectura claims that they have budgeted in 2 motobombas for the well drilling project in 2007. I have no idea how they would be shared between the volunteers and have even started to doubt the usefulness of a gas pump at the drill site. First off we usually only have a few turrils to pump in because we are hauling water from far away. Secondly, when it breaks down who will fix it? Tim had some comments if you do purchase a pump: Five hp recommended. The most important parts are the oil seals on the pistons. See if a repair kit is sold for the pistons. Also make sure that replacement parts are available for the motor.]

Pegamento de PVC: You can buy Plasmar brand pegamento by the liter from Augster. Also recommended is the Brazilian pegamento; it has been purchased at Gaviota in the past but at last report they weren’t willing to sell it to us if we didn’t have a permit. If you buy by the liter consider also purchasing a small can that you can refill. The cans have an applicator brush inside the lid. Additionally, if you are constantly opening a liter bottle the pegamento may dry out.

Politubo: Use Plasmar when possible. Available for purchase at Augster and Gaviota.

Postes y Palancas: Bolillas are bought at Puente Tajarete. If you have the budget consider having your postes and palancas made of a harder wood at a barraca (they can notch and bore the pieces which will save considerable time during pump installation). Ask at the mayor’s office if they have a barraca that they typically do business with.

PVC Clase 9, 6m: Prices at Augster and Gaviota have fluctuated over the last two years. Get quotes at both stores to determine which is cheaper at the time of purchase.

Varillas: Don Simon (see above, under brocas) has always made our varillas for the Baptist pumps.

Yute: You can buy the bags anywhere, but yute by the roll is much easier to work with. It can be bought inside Mecado Bolivar in several lovely colors (ask for where tumbado is sold). It is sold without a receipt but they may be able to provide you with a recibo if you ask in advance.

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Organizing

Our original thought on coming to the altiplano was that aynis, the traditional Aymaran communal work groups, would work as an equivalent to the H2O clubs in Santa Cruz. Some of us had success with this, and others less so. The other major difference in the altiplano is that we typically collaborate with the municipal government.

Deciding where to drillCommunities interested in wells typically have to present a solicitude to the municipal government. The municipal governments aren’t always fair when distributing projects, so try your best to keep the selection process fair and transparent. In Corque, the number of wells requested currently exceeds the number we can do during the drilling season. We will be considering the following factors for selecting beneficiary communities:

The date the solicitude was presented: Note that requiring official solicitudes also ensures that the beneficiaries are vetted by the communities’ autoridades (the ones wearing the ponchos, such as the hilacata, the agente, etc). There is often infighting within altiplano communities; if the volunteer works through the autoridades he should be able to avoid conflicts over who gets a well within a given community.

The availability of private vehicles: Transportation was a huge problem in 2006 so we are encouraging communities to find private vehicles that we can use. However, several of the more impoverished communities don’t have vehicles so we are also pushing the alcaldía to make a vehicle available.

Voluntad: Some community autoridades solicit a project and then seem to forget about it. Others are constantly asking at the alcaldía when we will be able to start drilling. In part this is dependant on the personal initiative of the autoridad, but it is also a good indicator of whether community members will actually show up to work. Communities that demonstrate voluntad will be given priority.

Also, try to confirm that beneficiarios are permanent residents. In 2006 Corque’s mayor accepted a private solicitude; I found out after arriving at the drill site that the beneficiary lived in Cochabamba! Permanent residents should be given priority because they have a greater need, but also because they will be more motivated to work. The same beneficiario went back to Coch before we even installed his pump.

Pre-drilling preparationsOnce you have selected the community where you will be working, tell the community members or the autoridades what they need to have ready before you get to the drilling site:

People: A group of eight to ten men will be needed to drill the well. In Corque we ask that interested parties form groups of 8-10 families. One person from each family will be responsible for working on each of the wells.

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Water: At the very least they should identify the nearest water source. If possible, drop off the turril(es) in advance so they can fill them up beforehand. Bear in mind that if the water source is far away from the drilling site you may need to ask for more workers. People going to fetch water can be a serious drain on the work force.

Clay: Clay appropriate for mixing drilling mud should be stockpiled at the drilling site before getting started. The amount you need will be dependent on the anticipated depth of the well and the type of terrain you expect to encounter.

Gravilla: If you are filter packing the well the coarse sand or gravilla should also be stockpiled before starting.

Contraparte: You may decide to ask for a monetary contribution (i.e., contraparte) from the beneficiaries. This is sometimes a requirement when NGOs fund projects and is also encouraged by alcaldías to show that the beneficiary is invested in the project. This money has to be funneled back into the project. Some examples from 2006: a) In Huari, Jacob planned a 17 well project. The contraparte from the first 13 wells was used to buy materials for the final 4 wells. b) In Pampa Aullagus, Travis’ project with Water For People required a monetary contribution. This money was used to pay the técnicos that ran the drilling rigs. c) In Corque I collected 90 Bs. for each well. I used this as a petty cash fund to buy materials that I couldn’t buy with a receipt such as yute and gomas, to buy additional tools that we hadn’t included in the original budget and to fix things when they broke. If you are collecting a contraparte, do it in advance. It is very hard to collect after the pumps have been installed. The prefectura has asked that we don’t collect a contraparte for the AYNI wells that we install.

How to get people to show upWe all struggled with this issue at some point during our service. Migration has been a huge drain on the altiplano and it sometimes seems impossible to assemble a work crew of 8 able bodied persons. Some suggestions:

In some communities the autoridades such as the hilacata wield a lot of power. In Huari and Pampa Aullagus the volunteers had success when they let the hilacatas organize everything. Along the same lines, Ing. Alfredo from Sumaj Huasi recommended that we work with community autoridades to set up fines or another form of punishment for people that don’t comply with their work requirement.

Consider incentives. Water, amazingly enough, doesn’t always seem to be a strong enough incentive. In Corque people have been highly motivated to do projects with DRIPAD (a food for work program, being discontinued in 2008). PCI has also expressed interest in providing alimentos through the project Mis Llamas if people drill wells and install bebederos (drinking troughs). In Huari, Jacob didn’t install any pumps until all of the wells for the group had been drilled.

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Decide where you will draw the line: Draw it early and very plainly. If they don’t pull together the minimum number of workers, leave. We recommend a minimum of 10 workers for the rotary drilling system and 6 for the Baptist.

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Driling

You should already have a general feel for drilling if you participated during Tech Week and read through Terry’s manual and Buck and Mike’s activity packet from the Yahoo!groups site. The following discusses some issues that sometimes get glossed over.

TransportationTransport can be a huge problem when going to the drill site and moving between drilling sites. Tim believes burros are a feasible option (see figure 8 from Baptist well drillers in Ethiopia), but we have relied primarily on trucks, tractors, and occasionally bicycles or our backs when drill sites were only separated by a few kilometers. Your transport will probably be provided by the beneficiarios or counterpart agency. The prefectura may be able to help out on occasion.

Figure 8: Low tech option Figure 9: Loading up in Corque

Some advice:

Try to drill wells in clusters to reduce transportation headaches.

Make drilling contingent on transport. Tell either the alcaldía or the beneficiarios that you will drill the well if they get the rig to and from the site.

Whether soliciting outside funding (e.g. local and/or foreign NGOs), or working with the alcaldía make sure to include a portion for transportation in the budget. Bear in mind that it can be difficult to obtain numbers for mileage to the drill site.

Another option is to contract a truck. You may be able to get a flat rate to and from the site including gasoline and not have to worry about mileages.

Don’t skimp on planning. Transportation in the altiplano usually doesn’t “just work itself out.”

Locating the wellBefore drilling ask about the existence of possible contamination sources. These could include latrines, animal corrals, huge manure piles, etc. Wells should be at least 30 meters away from these sources of direct contamination. Try to locate the well as close

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to the house as possible if you are drilling for a family, or ensure that it is located fairly (and that all interested parties have been consulted) when drilling for a group of families.

Many residents of the altiplano are interested wells so that they can provide water to their livestock in the dry season and may want wells in isolated locations, far from their homes. This seems to go against our intent to provide water for sanitation, but in the long run could be best for the project. One of the most important guarantees for sustainability of a water program in a developing country is that the beneficiary is the primary decision maker. If we let the beneficiary drill where he needs water for productive gain he will be more likely to understand and maintain his pump. If he has success with his first pump he may very well want another.

Starting your borehole plumbYou want to start your borehole as plumb as possible to ensure that the drilling stem stays plumb as it advances. First identify the point directly beneath the pulley where the drilling stem will naturally fall. The easiest way to do this is hook a pipe wrench or the first segment of your drilling stem to the rope and lift it slightly above the ground. Once it is steady let it drop, marking the point.

When using the orange pulley donated with the ASVI-JICA rig have people pulling on the rope (in the direction that they will be pulling while drilling) when you locate your point.

After locating your point dig a pilot hole half a meter to a meter deep. A posthole digger is a nice tool to have for this. For the Baptist system the pilot hole needs to be deep enough to have the broca submerged. A shallower hole works fine for the ASVI-JICA rig.

As drill your first few meters have people watching the tube from the front and the side to ensure that it is going in plumb.

Drilling mudYou will be keeping the borehole full at all times with drilling fluid, also called drilling mud. This mud is formed when water poured or pumped down the borehole mixes with clay that you have drilled though, or it is mixed manually topside, either with natural clays dug up from the area or bentonite, and then poured or pumped into the borehole. This mud has the following purposes:

1) Keeps your cuttings in suspension long enough to get them out of the borehole (but lets them drop out in the settling pit).

2) Provides pressure inside the borehole to keep it from collapsing.

3) Keeps water from being lost to permeable formations that you are drilling through. (Campesinos sometimes understand points 2 and 3 by saying that it works like revoque on the well’s walls.)

The thickness of your drilling mud is key. If you make it too thick you could clog your Baptist broca or the mud pump for the ASVI-JICA rig. Also, too thick of a mud won’t allow the cuttings to drop out in the settling pit before the mud circulates back into the

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borehole. If the mud is too thin it won’t accomplish the purposes listed above. One of the most common reasons for not advancing (i.e., not being able to dig deeper) is not having a mud that is thick enough to carry the cuttings up from the base of your borehole.

Bentonite is the clay most often used by professional well drillers. It “can swell up to approximately ten times its original volume when exposed to water” (Driscoll 351) and is more effective for drilling than other clays. It only hydrates in fresh water. The Baptists use bentonite for their wells in Santa Cruz and we have used it in Corque, Huari and El Choro. In Corque we averaged about half of a bag of bentonite for a well in normal terrain. We often tried to stretch it by mixing it with natural clays, because bentonite is expensive at approximately $10/bag.

The term greda isn’t always specific enough when asking beneficiarios to collect natural clays for drilling. A lot of natural clays have a high rock, sand or silt content which makes them difficult to work with because you will need to mix it well with water and let the non-clay particles settle out in order to avoid pouring them into your well. Explain that you need clay without sand or rocks. Also, when mixed with water it shouldn’t settle out quickly (que no se siente rápido cuando está mezclado con aqua). If people bring you a high quality clay consider visiting the source and stockpiling clay for other wells. In Pampa Aullagus they have managed to find a good source and now they never buy bentonite.

Alfredo from Sumaj Huasi claims bentonite shouldn’t be used for manual drilling because it is too expensive and too difficult to clean out of the borehole using manual hand pumps. He recommends that the beneficiarios collect 12 wheelbarrows of natural clay prior to drilling. (More could be needed but this amount is usually sufficient.) This quantity implies that their drilling mud must be much thicker than what is typically used for the Baptist system; this may be the secret to passing some of the difficult geologic formations that we have encountered.

Circulation pitsYou can drill using the Baptist methodology using a single sedimentation pit, but we have found that two pits work better if you are drilling through very fine sand because it has more time to settle out. Using two pits will also allow you to alternate between the Baptist and ASVI-JICA systems. One suggested configuration for your circulation pits is shown in figure 10.

Figure 10: Suggested circulation pit configuration

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CavingBe constantly alert for signs of caving. If you feel the walls caving, thicken up your mud mix. If it is severe, shorten your drilling stem, thicken the mud and then try to enter the caving formation again.

Always haul up the drill stem to the top of the tower and tie it in place if you are going to stop drilling for a period of time. If you leave your stem sitting at the bottom of the borehole and stop for lunch, for example, you may come back to find that sedimentation or caved in walls have locked the stem in place. The ASVI-JICA rigs came with block and tackle, but thankfully we have never had to use them.

At the end of the day always remove your entire drill stem from the borehole.

How to know when you’ve hit waterYou will know that you are in a water-bearing layer when you find a sand or gravel layer below the unconfined water table depth (identified by asking about hand dug wells in the area). Preferably it will also be below a confining layer of clay. Sumaj Huasi recommends that filters are installed in medium to coarse sand in the altiplano (in contrast to Santa Cruz, where they have found that fine sand aquifers yield more water).

For the Baptist method you should always be aware of what is coming out of the pico. You can stick your hand in front of it, take bucket samples, or look for a change of mud color. I prefer bucket samples at 1 m intervals. Collect half a bucket of pico spit and then top it off with clean water and swirl it around. (I’ve found that if I don’t dilute the mud the silt won’t settle which can lead you to believe that you aren’t bringing anything up). Let this sit for a few minutes and then pour off the top. For the ASVI-JICA rig samples are taken by inspecting what settles out in your pit.

Keep a log of your samples. This will help you know where to cut the filter. The log should also be written up and stored in the mayor’s office as a guide to future drillers in the area.

After reaching the water bearing formation where you plan to install your screen you should continue drilling until you are deep enough to install the desired screen length and a sump of 50 cm (which will allow for some sand infiltration into your well without decreasing your effective screen length).

FishingIf a tool falls into your borehole or if part of your drilling stem breaks off you will need to try to fish it out. Some of our experiences:

A broken pipe stem has been fished out but forcing a stick with a wedge at the base into the pipe. Once, a pipe that broke off at only 2.5 m was fished out by a campesino who just inserted a long stick into the pipe. When he lifted the stick up at a slight angle he was able to pull the pipe out of the hole.

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Fishing a pipe wrench out of the hole is almost impossible. It was done once with a wire hook but several wells have been abandoned because fishing failed. Always tie your pipe wrenches to your tower to avoid this problem.

Sometimes, if a tool can’t be fished out, you can drill past it.

Don’t expect to come back the next morning to fish something out. The sediments in the drilling mud will settle over night and it will be near impossible to suck anything out of the muck that you find at the base of the hole the next morning.

Ask parents to help keep children away from the borehole. Children like to watch things drop into holes.

The ASVI-JICA rig came with a couple of fishing tools that we haven’t tried out yet but look promising. Unfortunately the pipe hook will probably be too wide to fish out drilling stem if you are using the Baptist broca. It may be worthwhile to design something narrower to deal with this scenario.

Some notes on Baptist drillingPVC versus galvanized drill stem

Santa Cruz drillers swear by PVC drilling stem for the Baptist method. The theory is that the flexibility of PVC will allow the energy of the impact to dissipate. The rigidity of steel on the other hand will theoretically lead to more breakage, always at the threads where the pipe is weaker. Additionally, the break can happen at the threads of any of the tubes, leading to the possibility of losing part of your drill stem and your broca several meters down.

That being said, drillers in Pampa, Huari and El Choro have all been using 1.5 m galvanized tubes without experiencing breakage. In Corque we experienced breakage in 2006 so I switched to PVC. (After pounding on a rock for six hours the bottom pipe of the drill stem broke at the roscas; I was unable to retrieve the stem and my only broca). When using PVC we typically use 1.5 m galvanized tubes for the first 4.5 meters. At 6 meters we put in a galvanized header pipe (see below) and always use PVC above that. In 2007 we began to use pure galvanized in soft terrain and haven’t yet experienced breakage.

Your two main considerations when deciding which type of pipe to use will be weight and terrain. The weight of a galvanized stem can help you advance faster, but can also wear out your pullers if you are drilling deep or short on workers. If you are going to be pounding against something hard use PVC or tie off your galvanized stem (see below). If it is soft terrain galvanized should be fine.

If you want to use galvanized for the weight advantage but will be encountering hard terrain consider reinforcing your unions as Hector Lobo has done, as shown in the following figures.

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Figure 11: Male reinforced pipe Figure 12: Female reinforced pipe

If you decide to use PVC drill stem be aware that it will probably break while drilling, especially if drilling through hard terrain or if the perforista is slamming the drill stem into the ground with a lot of force. If the perforista applies equal force on both sides of the pico handle it will reduce (but probably not eliminate) breakage. The break will almost always be just below the pico, and can be repaired without removing the drill stem from the borehole. A pair of vice-grips helps to hold the pipe while threading.

To not waste time fixing the breaks I connect the pico to a 1” niple to a 1” copla which is connected to the drill stem. When the stem breaks we just need to unthread the pico and niple from the copla and put a new copla on the retreaded pipe. That way we aren’t melting or cutting the broken stem from inside the pico, which needs to be done if the pico is connected directly to the drill stem. (The broken stem can be roughly cut from the 1” couplings, which can then be used for connecting the foot valve to the 1.5 in politubo because only one set of threads is used. Or you can cut it out carefully and use the copla again for drilling.) Santa Cruz drillers claim this configuration leads to more breakage, but I’m not convinced.

Galvanized header pipe

For deeper wells or harder terrain a 6 meter galvanized header pipe is often used to add weight at the base of the PVC drill stem. In Santa Cruz they were using a 6m 1 ¼” pipe with an additional 3m of 1 ¼” pipe sliced up the side, wrapped around the base of the 6m pipe and welded in place. In Oruro some drillers were using a 6m 1 ¼” pipe. In sites where hard terrain is presenting a problem it may be worthwhile to weld on the additional 3-meter sleeve.

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Figure 13: Galvanized header pipe


Tying off your drill stem

Tying off your drill stem, or specifically the 6 m galvanized header piece can be frustrating but rewarding. I like having it tied off so we can add tubes with just two sets of hands at the borehole, while the pullers rest. If the pipe slips from the wrench, it can be retrieved with the rope. It also allows for retrieval if the drilling stem breaks.

The main problem with tie-off is wear and tear on the rope. I’ve heard of failed attempts to retrieve a broken stem because the rope was so worn down that it snapped when they tried to use it. If you are going to tie off you need to keep the rope from rubbing on the borehole sides. I use two methods: 1) Instead of having a bulky knot at the tie-off point I have the rope looped through metal rings welded onto the header pipe. The rope is held in place with hose clamps (see figure 13). The downside of this is wear on the clamps which don’t last very long. 2) We always keep the top end of the rope wrapped around the pico handle when drilling, preferably in a figure-8, and keep the rope taut. In 2007 we were experimenting with cable held in place with U-bolts and were experiencing much less wear.

As an alternative to tying off the stem you may want to design a fishing tool to retrieve broken pipe when using the Baptist method, as mentioned above.

Widening your borehole

In the Baptist methodology a pilot hole is initially drilled with a 1.5” diameter broca. You are then required to widen the hole using a larger broca (typically 2.5” in diameter) in order to install the casing. The widening process can usually be completed in a couple of hours (depending on the depth of the well and the terrain).

If you believe that you will need to install a gravel pack you may want to build yourself a wider Baptist broca or use the ASVI-JICA broca to widen the hole because the annular space in a 2.5” diameter borehole will not be large enough to permit the gravel to reach the screen.

Some notes on ASVI-JICA drillingKeep the following in mind when you are using the ASVI-JICA rig:

Always rotate the drilling stem clockwise at the bottom of the down stroke so that you are tightening the threads.

You must use metal pipe. PVC pipe will snap when subjected to that degree of torque.

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Figure 14: Baptist widening broca


The broca with the spiraled rebar tends to advance more rapidly but is more prone to clogging. Cutting off and rewelding the rebar at the tip in a more open configuration should correct the clogging problem.

Try using the double-tined broca if you are having clogging issues. The tines are supposedly hardened steel so it can also be used to try to penetrate rock. When using this broca alternately stand behind and to the side of the borehole as you drill to cut out a complete cylinder.

It is harder to know precisely what type of soil is at a given depth for this system because cuttings will be lifted out of the borehole at varying rates and settle out into your pit at varying rates. This could make it difficult to construct an accurate geologic log needed to install your screen in thin alternating clay/sand layers.

The brocas are wider than the Baptist brocas, and create the wider hole needed for gravel pack installation.

This system seems to require more people than the Baptist system. We recommend a minimum of ten workers.

The mud pumps have been breaking when left in freezing weather. This may be remedied by replacing the 1” nipple connecting the two reductions on the piston. It seems that very thin-walled pipe was used for this component. Or just bring the pump inside for the night.

Difficult terrainIn 2006 we encountered terrains that we could not drill through using the Baptist rig. I unfortunately haven’t logged enough wells to know how to solve the problems that we encountered, but anecdotal evidence says that they all have solutions.

Part of the solution may lie in using the right rig. The Baptist rig was designed for clay and sand deposits, but Terry says that they have been able to drill through rock (with a heavy dose of patience). The ASVI-JICA rig comes with a hardened-steel tipped broca specifically for pushing through rock, but we believe that it may be less effective in sand. One of the strengths of the project at present is that we have both rigs and can experiment as to which gives the best results for certain soil types.

Rocky layers

Regardless of which method you are drilling with, patience will be your greatest asset when trying to drill through rock. By simply chipping away at them you can pass thin solid rock layers. Large stones can sometimes be passed if you force them to one side of the borehole. (Hopefully they will stay there and not drop down into the borehole.)

For the Baptist method, Terry recommends sludging (sometimes called jetting) if the rocks that you are trying to pass are larger than the orifice inside the broca valve. To sludge use a length of pipe without a broca attached at the base (you may want to put on a copla to protect the pipe threads) and cover the top of the pipe (or the pico) with your hand. On the down stroke lift your hand up so to that mud and cuttings can enter the pipe at the base. On the up stroke cover the top of the pipe completely so that suction keeps

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the mud and cuttings in the pipe. Repeating this process will fill the pipe and mud and cuttings will start to shoot out of the top of the pipe on the down stroke.

Note that shallow rock layers can be very difficult to drill through because the drill stem is still very light. If you hit a shallow rocky layer we recommend not trying to dig through it with shovels. We have tried this using the Baptist system without success. A gaping hole leads to stem breakage if you are using PVC, not to mention countless headaches when trying to circulate your drilling mud. It would not be possible to use the ASVI-JICA system because you wouldn’t be able to circulate the drilling mud. Digging out the layer and then filling in the hole with material without rocks did not work because we couldn’t compact the fill enough to prevent it from constantly caving into the borehole.

Loose gravel formations

SH claims that their rig can push through loose gravel formations. They pull out the drill stem, mix up a very thick mud and then pour that into the borehole. They then continue drilling as usual. They claim that the thick mud helps hold the formation together so that they can pass through it. The same may work with the Baptist system, but a very thick mud may clog the broca valve.

If the ASVI-JICA rig doesn’t work for pushing through gravel Wells Construction mentions bailers as an option:

A bailer is the most commonly used tool in loose soils. It is a long cylindrical tube with a valve at the bottom end which permits material to be forced up into the tube but will not permit it to fall back out. Bailers used with hand equipment are most often equipped with flab valves. The bailer is lowered to the bottom of the hole. Lift it 1 to 2 meters and drop it. The impact of the bailer on the bottom of the hole will force some of the loose soil up into the hollow core. Continue lifting and dropping until the bailer is full or until it has picked up as much of the loose material as it can. Experience will show how long to continue lifting and dropping the bailer to get the maximum usage. When the bailer is full, pull it up to the surface and empty it away from the well.

A bailer has several uses in different situations. It removes rock pieces loosened by a rock bit; it removes sand in caving formations from inside the casing; it functions to remove loose material that cannot be packed or retain its shape.” (ICE 159)

Pressurized sand aquifers

If you hit a pressurized sand aquifer and the drilling mud isn’t providing enough pressure to hold it in place the sand can flow into the borehole, preventing advance, or in extreme cases grabbing hold of the drilling stem. The only way I have heard of to deal with this is by using a very thick drilling mud (and probably the ASVI-JICA rig because the Baptist broca may clog with thick mud). This happened once in Corque. We used up all of the clay that we had at the drill site including a full bag of bentonite, but didn’t advance at all. The well was abandoned. This possibility is a compelling reason to have 12 wheelbarrows of clay ready before drilling, as recommended by SH.

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Well Installation and Development

Screen preparationImmediately after widening the borehole the casing should be installed to prevent the possibility of the well caving in. The screen is cut directly into the casing. With some practice (and a sharp hacksaw blade) one person should be able to prepare a 4-meter filter in 3 hours (including yute). It can be prepared while widening the borehole if you are using the Baptist system.

Screen length

Unlike hand-dug wells, which can work with less than a meter of water, small-diameter borehole wells need a longer filter length. The length would depend on the characteristics of the aquifer, but since that can’t be known precisely without doing an analysis, we use a rule of thumb of approximately four to five meters. Tim once advised to use 2-3 meters, preferably capped on both sides with clay (i.e., confined aquifer). Sumaj Huasi, on the other hand, has set 5 meters as their minimum. More is better, but because we are just installing small hand pumps, less is probably okay too. If cuttings show the aquifer to be course sand or gravel the filter length could be reduced on the assumption that the aquifer would provide more water.

[Aside: The above paragraph is based on conventional wisdom in Bolivia. I asked Carlos about screen length and he said the following:

In the real world, the length of screen is determined by starting with the flow you are going to pump out of the well and then looking at a table that the screen mfg. has prepared that gives the velocity through the screen and you choose the length that keeps that velocity below a figure I can’t remember. Since all the wells you are doing are fitted with those little hand pumps, my sense is that 1 meter would be enough and 2 meters would be more than safe. But remember, I don’t know anything about the aquifers you are in. If you don’t see any reason not to, I would try approaching the 2 meter length, one meter at a time, on new wells and stop before 2 meters if I am completely wrong

This leads me to believe that longer screen lengths are recommended here because we aren’t correctly developing the aquifer so that water can flow unimpeded into the screen (5 m of trickle equals 1 m of what a developed aquifer would provide). This is another compelling reason to investigate surging for development.]

B-36 volunteers in Santa Cruz sometimes used 3” or 4” pipe for their screens when their aquifers had a limited height. However, doubling the screen diameter only increases the yield by approximately 10%, so if at all possible try to drill deeper instead of boring out the hole for a large screen. [An aside on larger casing: Several people in altiplano have begun to ask about using these wells for riego. If a beneficiario plans to install a submersible pump for irrigation at a later date you should use 3” or 4” casing. Two-inch submersible pumps may exist in Bolivia, but larger sizes are much more common. UNASBVI has worked with 4” diameter wells for irrigation and may be able to provide some guidance.]


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Screen design and placement

The screen is cut to allow water to flow in but it also needs to be able to resist the stresses on the pipe caused by the soil that will surround the casing. Terry recommends making cuts one finger width apart on both sides of the 2” pipe. Cuts should be the depth of the saw blade. You can cut on three sides of 3” pipe and 4 sides of 4” pipe.

You won’t know with exactitude where changes occur between different soil strata but take into account a margin of error and try to keep the screen completely within the aquifer. If you are have a fine sand layer overlying a coarse sand, the screen should start 60 centimeters below the fine sand layer because otherwise fine sand could start to enter into the upper part of the screen after development. After fine sand starts infiltrating into the well the problem could be perpetual.

If you don’t find one continuous aquifer, the filter can be installed in several separate layers. If you have kept a good geologic log you can cut the filter where it will be in sand/gravel and leave it uncut where it will be in clay. Not only will this save you time cutting, but it is also possible that if the screen slots front a clay layer this clay will cause turbidity in the water.

Filter

The Baptist methodology recommends that a woven plastic sugar sack (yute) be wrapped around the screen as a filter. This is typically wrapped once or twice around the screen and glued in place with clefa along the uncut segments of the pipe. Electrical tape is then wrapped around the filter at 20 to 30 cm intervals. See below for more discussion of filters.

Screen and Casing InstallationIn boreholes with a tendency towards caving, the drilling stem should be removed and the screen and casing installed as fast as possible. After drilling the workers are usually pretty handy with the pipe wrenches so pulling out the drilling stem proceeds quickly. To speed up the process of casing installation we often assign people to the following jobs:

1) One or two people hold the casing as it is lowered into the hole. Two may be needed if you are using gasketed pipe because you often need to shove a little harder to get it in.

2) One person has a full bucket of water ready to fill each pipe segment after it is lowered into the hole. This counteracts the buoyancy of the empty pipe, making it easier to push the casing down into the borehole.

3) One person has a clean dry cloth that is used to clean and dry the joints that will be glued. Have them clean all of the joints before you begin the installation process. After pouring in the water he will just need to wipe them dry.

4) One person applies the pegamento de PVC. This is applied liberally to the inside of the bell and the outside of the entering pipe. (Note: the bell always faces up.) After applying the pegamento the pipe is pushed into the bell while rotating it a half a turn to make sure that the pegamento completely and evenly lines the surfaces being joined. The tubes should slide together with only slight pressure.


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If a couple of people pushing down can’t get it in immediately, they probably aren’t inserting it straight (this often happens with gasketed pipe). Count to ten before pushing the casing into the borehole. Fill with water and repeat the process.

If you are working with 6-meter lengths of casing you will also want someone waiting at the top of your tripod/bipod to help hold the tubes. After you install the casing, tie it to something heavy such as one of your big galvanized pipes or a pipe weighted down with something. Otherwise it may pop out of the hole (and you may not be able to shove it back in).

CleaningAfter tying off your casing you can begin to pump water into the pipe. This helps to clean out the mud that you used while drilling. This is especially important if you used bentonite. If you don’t flush out the bentonite it will remain in the aquifer and plug up the pores between the grains of sand in your aquifer, reducting the amount of water that will flow into your screen.

To pump into the well feed your small diameter politubo into the well and connect the end that is topside to your manual pump. Seal up the top of the casing where the politubo is entering with goma numático so that all of the pumped water is flowing into the base of the well. We typically cut the length of small diameter politubo that we will be using to install the hand pump and use that for this step.

Your goal is to pump water in until the water flowing out around the casing is flowing clear. Depending on how far away your water source is and how many workers you have this may not be possible. Try to pump in as much as possible, but shoot for two barrels of water as a minimum. You can return to this step and pump more in later if it wasn’t enough (i.e., if you well dries up when you try to pump out).

If you have wrapped your screen with yute as a filter this step is also important to “saturate” the yute, or blow open the holes from the inside. If you don’t saturate the yute you may find that there is very little or no water in your well when you try to pump out.

Sand or gravel fillAfter pumping clean water into the casing sand or gravel is poured into the annular space between the casing and the borehole walls. This is your gravel pack or stabilizing fill, depending on the situation. This is a departure from the Baptist methodology used in Santa Cruz. Terry insists that porous fill isn’t required with the Baptist drilling method because the borehole diameter is so small. He says that the sand from the aquifer will fill in around the casing and claims that sand poured around the casing won’t even reach the filter. When a well is developed without a using a porous fill in the annular space it is called natural development:

In natural development, a highly permeable zone is created around the screen from materials existing in the formation. Creation of this zone is best understood by visualizing what happens throughout a series of concentric cylindrical zones in a sand aquifer surrounding the screen. In the zone just outside the well screen,


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development removes most particles smaller than the screen openings, leaving only the coarser material in place. A little farther out, some medium-sized grains remain mixed with the coarse sediment. Beyond that zone, the material gradually grades back to the original character of the water-bearing formation…. By creating this succession of graded zones around the screen, development stabilizes the formation and prevents further movement of sediment.” (Driscoll, 500)

A naturally developed well would ideally look like figure 15.

Figure 15: Developed aquifer (source: www.geology.sdsu.edu/.../well1development.htm

Terry’s methodology is appropriate in the altiplano when you are drilling with the Baptist brocas and are screening an aquifer that has a gradation of particle sizes, including particles larger than the screen slot size. Unfortunately we believe that we may need to modify the methodology in most cases for the following reasons:

1) Many of the aquifers that we are screening in are uniformly sized, with particles smaller than the screen slot size.

2) The use of the yute filter would effectively reduce the screen slot size allowing us to install in aquifers with smaller particle size, but there have been many reports of yutes that have clogged up. The most extreme case is Quillacas, where filters have reportedly clogged after only two years.

3) The use of the ASVI-JICA rigs results in a much larger borehole size and we can no longer assume that fill material will not reach the screen.

4) We have seen infiltration of fines in wells installed with and without yutes (much more severe for the latter).

The ideal solution would be to determine what fill material and development process we should be using to 1) eliminate the need for the yute filter, and 2) arrange and stabilize the soil particles around the screen so that water can pass through but sand cannot (as


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shown in figure 17). This may not be possible with the equipment available to us but it is worth investigating, especially as we plan to ramp up drilling in the altiplano.

Until we determine how to do this (or if it is possible) I recommend continuing to use the yutes (except perhaps in Quillacas where we should be experimenting with fill materials) because they provide the cleanest water to the beneficiary. The annular space should be filled with coarse sand or small gravilla. The unfortunate thing is that we can’t know what the useful life of these wells will be. To my knowledge, no data has been collected on well life in the altiplano and well logs aren’t available for most of the existing wells that have been installed with filters.

Our best guess at a best practice at present is the following:

a) Install in aquifers where the majority of the particles have a diameter larger than 0.35 mm (the smallest size that won’t infiltrate into a screen slot size of 1.25 mm, the slot size cut by a hacksaw). This could easily be controlled by carrying a sample of 0.35 mm sand with us and drilling until we reach an adequate aquifer.

b) Widen the borehole to 4” for all wells (excluding those wells that can be naturally developed due to the gradation of particle sizes).

c) Pour in (very slowly one handful at a time, while pumping water into the casing to prevent bridging) a gravilla mix that is retained on malla milimetrica but passes a bidon with 2mm holes punched in it (or the air filter from a camion).

We will be trying out this methodology during the 2007 drilling season to see if it is feasible.

Well DevelopmentThe other side of this issue is how to correctly develop your well so that the formation around the screen is stabilized in a way that won’t let sand reach the screen. Well development has the following purposes:

1) Removal of fines (sand and silt),

2) Correction of clogging or compaction caused by drilling, and

3) Grading of the aquifer material around the screen.

Overpumping

Based on the Baptist methodology we are currently pumping a few barrels of water out of the well using a pump made from a foot valve connected to the base of the small diameter politubo. This is based on the development method called overpumping. Overpumping consists of pumping at a faster rate and for a longer period of time than what will be normal for the well.

Overpumping is undoubtedly the simplest development method. Also, “if a well will support overpumping, it should certainly operate at a capacity less than that with no problem” (ICE 203). Unfortunately, although the well may be yielding enough water, it may not be providing clean water if the third goal of development, grading of the aquifer particles, is not being achieved. Also, Carlos claims that for overpumping to be effective


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we need to pump at a rate 3-4 times the normal rate, which we aren’t currently achieving using our politubo hand pumps.

Surging

Carlos recommends that we investigate the possibility of surging to develop our wells. Surging is the process of forcing water in and out of the slots in the well screen. (limpieza por oleaje). It is done using a surge block, a tool that can easily be constructed from local materials (see figure 16). It is “a flat seal that closely fits the casing interior and is operated like a plunger beneath the water level” (ICE 205).

The following steps are recommended for a surge block’s use:

1) First make sure that you can pump water out of the well.

2) Lower the surge block to 3 to 4.5 m below the static water level but above the screen.

3) Lift the surge block up and let it drop, with a stroke of a meter or less. You can have the block hooked up to your galvanized header pipe so that it falls rapidly. Begin slowly. Surging too rapidly at first could damage the screen.

4) “As water begins to move easily both into and out of the screen, the surging tool is usually lowered in steps to just above the screen. As the block is lowered, the force of the surging movement is increased. In a well equipped with a long screen, it may prove more effective to operate the surge block in the screen to concentrate its action at various levels.” (Driscoll 505)

5) After each surging session the well should be pumped or bailed until the fines are reduced.

I can imagine working with the surge block the same way we work the drilling stem. It could be connected to the pico and rope and operated by one person at the borehole and a team pulling rope. The unresolved issue is how labor intensive surging will be. We will also be experimenting with this methodology during the 2007 drilling season.

Some cautions regarding the use of surge blocks:

“Although some drillers depend on surge blocks for developing screened wells, other feel that this device is not effective and that it may, in some cases, even be detrimental because it forces fine material back into the formation before the fines can be removed from the well. To minimize this problem, fine material should be removed from the borehole as often as possible.” (Driscoll 504)


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Figure 16: Surge block (www.geology.sdsu.edu/.../wellldevelopment.htm

)

http://www.geology.sdsu.edu/classes/geol552/wellldevelopment.htm

http://www.geology.sdsu.edu/classes/geol552/wellldevelopment.htm


“Surge blocks sometimes produce unsatisfactory results…especially when the aquifer contains many clay streaks, because the action of the block may cause clay to plug the formation.” (Driscoll 506)

Restorative development

As we begin to collect data about wells clogging or drying up we should consider the possibility of redeveloping them to put them back in service:

“…older wells often require periodic redevelopment to maintain or even improve the original yield and drawdown conditions.” (Driscoll 497)

This would be something to think about if you have wells that are reportedly clogged in your province. During months when you are not drilling you could try to track down the non-functioning wells and disassemble the pump to ensure that it is not the cause of the problem. If it appears that the filter is clogged you could attempt to backwash and redevelop the well to see if it can be brought back into operation.

Sanitary SealTerry has made the very valid point that pouring a concrete slab at the wellhead does not qualify as a sanitary seal because over time water can seep under the slab. His recommendation is that bentonite be mixed with sand and used to fill in an area dug out around the well. No volunteers are doing this, due to the high cost of bentonite. For wells in the States the annulus between the well casing and the soil is filled with mortar. Carlos recommends filling to a depth of one meter. Unfortunately the borehole at the surface is sometimes very large and it could get expensive to fill it. The most inexpensive (but least effective) sanitary seal would consist of mixing natural clays, such as those used for the drilling mud, with the water to create a thick slurry in the annulus between the casing and the borehole. You should then wait to pour the slab until the soil around the casing has settled and solidified.


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Figure 17: If a sanitary seal was not installed for this well, the erosion under the slab now provides a direct contamination route for the aquifer.


Pumps and Wellheads

PumpsThe following is step by step instructions for the installation of Baptist and AYNI pumps.

Baptist Pump Installation

Filter1) With a hack saw, cut slots approx. 1 cm apart on opposite sides of 2” PVC pipe,

being careful not to cut more than one third through the diameter of the pipe. Depending on the depth of aquifer, ideally there should be five meters of pipe prepared with slots to maximize the recharge rate.

2) To close the pipe at the bottom, cut out two or three triangle-shaped sections from the pipe, removed at equal intervals along the circumference, then heat evenly with fire until easily pliable and bend the sections together, closing the pipe. Pour cold water over the heated area to stiffen the plastic.

3) Wrap the entire length of filter one to two times (depending on the composition of the aquifer) in woven polyethylene sacks (yutji), gluing in place with clefa. Then wrap with electrical tape at intervals.

Installation of 1½” Polytubing1) Cut 1½” tube to desired length (depends on the depth of well and quantity of

water), adding an extra length at top to take into account the pipe protruding above ground. Lengths range from 40 to 80 cm.

2) File any ridges off the 1” coupling until surface is smooth.

3) Assemble 1” coupling with 1” nipple and 1” foot valve.

4) Evenly heat end of 1½” polytube until 1” coupling will fit inside, taking care not to burn the plastic. Then by wrapping with pneumatic rubber, clamp still-pliable tubing firmly over coupling to create a tight seal. Cool with water.

Piston1) Cut a ½” coupling in two pieces, dividing 1/3 and 2/3.

2) On one side of the 2/3 piece, file or cut 3 or 4 notches approx. 6-8 mm deep and v-shaped, distributed evenly around the circumference.

3) Assemble two rubber or leather donut-shaped pieces on to each end of a ½” nipple. Screw the coupling pieces on the nipple, making sure the cut notches of the 2/3 piece face outward.

4) On a 6” x 3/8” bolt, use a hack saw to cut two notches on opposite sides near the bolt head, separated by a distance of approx. 1 cm. A small nail must be able to slide tightly in the notch but not move horizontally.

5) Wrap each notch with electrical tape to increase the diameter until it fits tightly in ½” polytubing.

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6) Place bolt head inside ½” polytubing, inserting until both wrapped notches are inside and there is still sufficient space for movement of piston (approx 3 cm vertical space). Note the location and direction of each notch.

7) Drive nails through the tubing and notches, but not through the opposite side of tubing. After confirming that nails are properly placed, drive nails completely through until nail head is flush against the outside of the tube.

8) Cut excess nail, file down any sharp edges and wrap with electrical tape.

9) Place washer on the bolt, then piston (notches towards the tube), then rubber piece (goma de garrafa or a piece of sandal sole), then two nuts tightened against each other to ensure the assembly will not fall off after extensive movement.

Top1) Cut ½” tube to desired length

2) Assemble varilla to other end of ½” polytube using same technique as piston—notches wrapped in tape, nails driven through.

3) Cut two pieces of 1½” polytubing (approx. 10-15 cm each) and thread one end of each piece. Assemble with 1½” T, perpendicular to each other (makes an “L”)

4) Thread end of long 1½” tube (the tube that is inserted into the well)

Assembly (Assembly can take place “in situ” or on the ground)

1) Push piston through assembled “T,” then down into 1½” polytubing.

2) Screw assembled “T” onto 1½”.

3) If not already inserted into the well, place whole assembly into the casing.

AYNI Pump Installation

After your well is drilled and it is properly cased and developed, you are now ready to build the base and install the pump. The installation of the pump is quite easy and can be done in 1 hour or so.

1) The first step is to secure the galvanized tube to the top of your well casing. The galvanized tube should have dimensions of 0.6m by 2” diameter. If you are working in Oruro, these tubes should be given to you by JICA. This tube could be bigger if your casing is bigger. It should just be the same diameter as your casing. To prepare to install the tube, you should cut your PVC casing at 15 cm above the ground. Then you should make a campana de fuego with the PVC tube so that the metal tube can fit inside the PVC. If you have galvanized tubes that have a copla on the end and are threaded, you will have to use a two inch tarraja to thread the PVC.

2) You are now ready to build the concrete box around the casing and galvanized pipe. You should need about a half bag of cement. The dimensions and shape of the box can be left up to the owner of the well. The only requirement is that the rebar pieces welded on the galvanized tube are buried in the cement so that they

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cannot come out. When the box is finished, it should be left to dry overnight. The cement mix should be 1 cement: 2 sand: 3 rocks.

3) Now you are ready to install the pump. The first thing you should do is cut your 1 ¼” politubo so that it reaches the top of the galvanized tube and leaves at least 50 centimeters of room between the bottom of the politubo and the bottom of your casing. This space allows dirt that might enter the filter to settle out before reaching the check valve.

4) Now that you have your politubo measured and cut, you should put threads on one end so that it can screw into the reduction on the top of the galvanized tube. On the other end you will be placing the check valve. The check valve should measure ¾”. A ¾” niple and copla should be screwed onto the side of the valve. You can tell the upper side of the valve by blowing into it. If air passes through the valve when you blow on it, then that is the bottom. This niple and copla allows for easy replacement of the check valve if it should break.

5) When you have the valve ready, you should heat up the end of the politubo and place the valve, niple, and copla piece into the politubo until it almost reaches the valve itself. The copla and niple should pretty much be completely buried in the politubo. If you do not have ¾” niples and coplas, you can bury the valve itself in the heated politubo. This method is not as secure and does not allow the valve to be changed with much ease.

6) You can now put the politubo in the casing. Just be careful that you have hold of the politubo because it can fall in the well and then you might not be able to get it out. You should tie it off with some goma to secure it.

7) The next step is preparing the ¾” politubo. This politubo should be cut so that it is at least 30 cm and at most 5 meters above the foot valve already in the well. You should remember to take into account that the handle will have a length of about 65 cm.

8) Now you can assemble the piston. The parts of the piston should consist of a ½” check valve, ¾” to ½” reduction, a ½” niple, and an empaquetadura of goma. The goma should be shaved, sanded, or cut so that it enters the 1 ¼” politubo without too much resistance. To assemble the piston, you should screw the reduction onto the ½” niple as tight as you can. The goma should be placed on the other side of the niple. Then the ½” valve should be screwed onto the side with the goma. It should be screwed on until it is tight, but not so tight that it is causing the goma to become misshapen.

9) Now one end of the ¾” politubo should be threaded so that the reduction can be screwed onto it. After it is threaded, you should apply pvc glue to the reduction and the politubo, and then screw the reduction onto the politubo. You can now place the ¾” politubo into the 1 ¼” politubo. You need to be careful here that it does not because the 1 ¼” politubo to further enter the casing and that you do not lose your ¾” politubo inside the 1 ¼” politubo.

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10) At this point you will want to slide the galvanized reduction over the ¾” politubo and screw it onto the 1 ¼” politubo. This can also be skipped and the galvanized reduction can be slid up the metal handle and screwed onto the 1 ¼” politubo after the next step.

11) The next step is to screw the politubo onto the metal handle. You can thread the handle using a metal tarraja. Then the politubo should be heated just a little so that it goes onto the metal handle easily. The handle will actually be screwed into the politubo as it will be the thing that is being turned. After it is screwed on, it should be wrapped in goma so that it dries firm and well attached.

12) Now just push in the handle and start pumping.

If you have the make the metal parts of the well, ask an Oruro volunteer for the specifications. They should have a manual with the dimensions. You can also contact JICA directly.

Modification for Sand Pumpers

As discussed in the filter and screen sections, some wells become sand pumpers. You cannot put in a new gravel pack, and there is no way to redo the filter once the casing has been installed and gravel poured down the sides. So what can be done?

Although we have not found a solution to this problem, one possible solution that is being thrown around is that we attach a PVC pipe to the bottom of the foot valve. The diameter and length of the pipe would depend on how much room you had below the foot valve and the size of your foot valve. The PVC pipe would have cuts much like the outside casing itself. The bottom would also be sealed off so that material could not enter through the bottom of the pipe. Also this PVC would be wrapped in another filter. One cheap idea would be to use panty hose. Other materials could be used. This idea has not been tested and needs to be tested before the ideal materials are found out.

WellheadsRegardless of which type of pump you install you should construct a slab at the wellhead. If you are using the Baptist pump you also need to think of a way to protect the exposed PVC casing. This can be done by encasing it with concrete, replacing it with metal pipe, or any other creative solution you come up with. Figure 18 shows the typical (but not terribly elegant) wellhead design used in Corque in 2006. In Pampa Aullagus the exposed casing is simply wrapped in goma or a blanket (which doubles as an insulator).

There are some outrageously sized concrete slabs surrounding (often defunct) pumps in the altiplano, but slabs don’t need to be large or expensive to be effective. Carlos recommends 1 meter square (so it is large enough to put containers on)

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Figure 18: Baptist wellhead design, Corque


with a thickness of 3”. Rebar is not needed if you put a layer of gravel (1/2” to 3/4”) under the slab. From Carlos:

This gravel keeps the freeze/thaw cycle from damaging the slab and the slab remains in compression so the rebar does nothing. But if you pour on clay or there is some reason there are going to be voids under the slab, without rebar it cracks and heaves. No. 3 at 20 cm both ways is typical for the slab.

When designing your wellhead consider the possibility of installing a bebedero (drinking trough) for livestock, either as part of the project or in the future.

After pouring your slab make sure that the surrounding earth is sloping away from the well and install a greywater system (this can be as simple as a hand dug canal).

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Capacitación

BeneficiariosYou will likely be spending several days with the beneficiarios while drilling their well. Instead of holding a formal educational workshop many important issues can be addressed informally during this time. In addition to the all-important issue of how to build and maintain the hand pump, consider addressing the following issues:

Basic sanitation

Hand washing

Boiling water or SODIS

Protection of the aquifer

All future latrines or animal corrals should be located at a minimum 30 meters from the well

Trash and especially batteries should be kept away from the well site. The heavy metals that leach out of decomposing batteries can accumulate in aquifers making them unsafe for future generations. Consider collecting batteries at the well sites as the basis for a side project. [Aside: if protecting their aquifer isn’t incentive enough mention that you can’t become a certified organic quinoa grower if you have batteries improperly disposed of on your land.]

If the well is abandoned it should be filled with clay or capped with cement because an open well is a direct route for contamination of the aquifer.

If a certified técnico is drilling many wells within a community, consider holding a taller for all of the beneficiarios after their wells have been drilled. You could make pump installation contingent on attendance at the workshop. If you do hold an organized workshop, don’t skimp on dinámicos to keep the attendees motivated and active.

Another possible follow-up activity is an inauguration of the wells. This is a great opportunity to explain to the beneficiaries how all of the funds for the project, including NGO contributions, alcaldía funds and contrapartes, were used. Not only is this a chance to promote transparency in Bolivia, it also show that nothing ended up in the volunteer’s pocket.

TécnicosTraining members of the local population to drill wells is one of our primary goals as Peace Corps volunteers. These técnicos will ensure the sustainability of the project. Several communities also have more than one drilling rig so técnicos will make it possible to have all drilling rigs working during the drill season.

Gerid Buckshire wrote up a checklist for training técnicos. This checklist and a Spanish translation are available on the Yahoo!groups website. After the técnico is trained, Peace

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Corps will provide him or her with a certificate. Certified técnicos may be able to work contractually with municipalities. Time-based contracts have been abused in the past, so consider per-well or per-meter-drilled compensation. The contract should also consider who is responsible if parts of the rig are lost due to well collapse or negligence.

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A Plea for Documentation

This isn’t a very sexy topic, but I believe it to be an important one. Volunteers should document their wells for the following reasons:

It is professional. Well drillers the world over maintain a record of each well that they drill. This record typically lists the soil types encountered while drilling and how the well and pump were installed. Documenting your wells will not only set a good example for municipal employees but will also provide them with the necessary information when they begin to catalog or map their infrastructure installations.

Peace Corps volunteers only serve two years. In order for your replacement volunteer to find the wells you drilled, much less troubleshoot problems with their operation they will need access to your data. Also, if future volunteers return to areas where you have drilled, access to your geologic logs will help them anticipate what type of terrain they will encounter.

Data will be necessary to improve our methodology. Towards the end of my service I have started to hear rumors about dry wells. More than one person has told me that they think manually drilled wells are “medio-deshechable.” But without data it is very hard to address these concerns.

Consider keeping two copies, one in the alcaldía and one to be passed on to the next well driller (in my experience government agencies in Bolivia are notorious for losing things). Well documentation worksheets are included on the Yahoo!groups website. This files includes a worksheet for norias, one for drilled wells and a maintenance/visit log. The maintenance log can be photocopied onto the back of the noria and well worksheets.

A Plea for Documentation

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References and Resources

Available in the Cochabamba library:

Wells Construction: Hand Dug and Hand Drilled, Peace Corps Information Collection & Exchange Manual M0009

Written for development workers. This manual contains an extensive discussion of hand-dug wells that is required reading before beginning a project lining norias. It also contains general information on drilled wells; It’s a good reference if you are looking for fresh ideas or ways to modify the methodology we are currently using.

Groundwater and Wells, Second Edition, Fletcher G.Driscoll, Ph.D.

More than you will ever need to know about drilled wells. This is a good resource for specific technical questions.

Borrowed from Ben Ranz:

Manual de Los Pozos Pequeños: Localización, disenno, construcción, uso y conservación, Gibson, Ulric P.; Singer, Rexford D.; published by Centro Regional de Ayuda Tecnica and AID, January 1969

We are currently trying to get an English copy of this concise reference for the Cochabamba library.

Websites:

Carlos recommended this site for well development and completion information:

http://pasture.ecn.purdue.edu/~epados/farmstead/private/src/complete.htm

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http://pasture.ecn.purdue.edu/~epados/farmstead/private/src/complete.htm


Appendix A: More on sand or gravel fill

Sand or gravel poured into the annular space between the casing and the borehole walls serves as either a gravel pack or stabilizing fill, depending on the situation.

Stabilizing fill is used when the aquifer conforms to the conditions necessary for natural development but the borehole diameter is too wide to ensure that the aquifer material will naturally fill in around the screen without sediment from inadequate strata falling into the annular space. [Aside: We have no idea if 4” with a 2” casing would qualify as too wide.] The fill should be poured in to a good bit above the screen (Gibson recommends 10 meters above the screen, but that is deeper than some of our wells.) You want to extend beyond the top of the screen to account for settlement and because the fines in this material will be lost (pumped out) during the development process. Gibson recommends the coarse sand used for mixing concrete, but this would be smaller than our screen slot size so shoot for 1.5mm diameter.

“Well development tries to remove the fine materials surrounding the screen, leaving only the coarser material. This can’t be accomplished if the aquifer consists of a fine uniform sand. The point of packing the well with gravel is to artificially provide the gravel or coarse sand that is missing from the natural formation. A well treated this way is called artificially gravel packed, which is in contrast to naturally developed wells.” (Gibson 60, rough translation)

For our purposes there are two important issues to consider when installing a gravel pack:

1) How can we make sure that the filter pack reaches the screen?

2) What porous material should we use?

Gravel pack installation

Terry’s right in that sand poured into a typical Baptist well probably won’t even reach the screen. Even if we increase the borehole diameter any granular material poured into a small space is likely to bridge, leaving gaps between the particles, especially if it is poured in quickly.

"When gravel is simply dumped into the space around the casing at the ground surface, size separation of fine and coarse particles occurs as the materials settle through the water or mud fluid. Any slight obstruction at some depth may cause the material to bridge in the hole, leaving a void below that point." (Driscoll ?, From Carlos)

In the States gravel packs are typically installed via a tremie pipe – a pipe that extends to the base of the borehole and is retracted as the annulus is filled. Carlos has recommended trying this out:

The only way you can be sure the gravel pack gets around the screen is with a tremie pipe….A tremie pipe smaller than 2 inches would probably plug and that would … require a 6” [borehole diameter] which isn’t going to happen….Would it be worth your time to see if a 1” tremie pipe works? It seems to me it would plug, but if you could get a constant stream of water and pour in the gravel pack slowly, it might work. Given the realities of the work here, if the 1” tremie isn’t feasible, I

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think you just have to live with pouring it down the sides, always as slowly as you can stand and with as much water as you have, and hope it gets to the bottom of the hole.

Alfredo says that SH uses the latter method. They very slowly put the gravilla in – one handful at a time. I like to put the material in while pumping into the casing (directly after cleaning out the borehole, before disassembling) because the flow of water may help break up some of the bridges that form. Carlos sent the following idea (“this isn't a recommendation, it's just an idea I read”) but it may require a motobomba and a fair amount of water.

"These difficulties can be overcome by reverse circulation of the fluid in the well as the gravel is fed into the annular space. To apply this procedure, water must be added to keep the borehole full as fluid is pumped out from the inside the casing. The gravel is carried to bottom by the water as it flows downward outside the casing. As the gravel fills the space around the well screen, the water passes through the screen openings and flows upward to the pump near the top of the well." (Driscoll ?, From Carlos)

Gravel pack particle size

In professionally dug wells the gravel pack particle size is selected based on the particle sizes in your aquifer. The screen slot size is then picked based on gravel pack particle size. “A filter pack is chosen to retain most of the formation material; a well screen opening is then selected to retain about 90 percent of the filter pack after development.” (Driscoll, 439) For our wells we have to work backwards because we can’t vary the screen slot size (it is the smallest cut you can make with a sierra mecánica). I asked Carlos if we can work backwards from the slot size and he sent me the following:

Remember that the gravel pack is not uniform; you need a gradation of size, but not a wide spread - that is, a low uniformity coefficient. Here is what I calculated for the ideal gravel pack for the 1.25 mm hacksaw-cut screen openings:

Sieve opening, mm % retained

2.00 0-8

1.50 32-48

1.30 44-60

1.10 82-98

0.90 92-100

70% of the acquifer should be retained on a 0.35 mm sieve. Or, put another way, if more than 30% of the acquifer is smaller than 0.35 mm, it will be a sand pumper with the hacksaw-cut slots.

The following concisely explains the calculation for determining filter pack particle size:

The material used for the gravel pack should conform to the following: 1) its 70% size should be 4 to 6 times the size of 70% of the material in the finest layer of the aquifer [this ensures that the gravel pack isn’t restricting flow through the aquifer]

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and 2) its coefficient of uniformity should be less than 2.5, but smaller would be better [this ensures that loss of material during development is minimized]. The coefficient of uniformity is the number that expresses the ratio between the 40% and 90% material size. Note that sizes refer to the percentage retained on the sieve. Screen slot size is then selected to retain 90% of the gravel pack (Gibson 61, very rough translation).

Note that gravel pack material will preferably consist of quartz or other silica based materials so that it doesn’t deteriorate over time. Particle grains will preferably be rounded.

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Appendix B: Case study from Pampa Aullagus

A well was installed 5-6 years ago in Travis’ patio. It was cased with 4-inch desagüe pipe. It had a continual problem with sand infiltration. Over time, as this sand was pumped out of the well, a cavern formed around the screen. The cavern eventually became unstable and the soil collapsed in on the screen, flattening it.

A rocky layer had been dug out with shovels when the original well was drilled and an auger drill had been used to reach the final depth. It was decided to drill a new well alongside the old well using the Baptist method. The new borehole was positioned less than a meter away, because the rocky layer had also been removed at this location. When the drillers reached 10 meters depth, the depth of the cavern, all of the drilling mud disappeared from the borehole into the cavern. Sand was then dumped into the hole in an attempt to fill the cavern. When the borehole was refilled with water and drilling recommenced all of the water disappeared again. The drillers then slowly added water mixed with 8-10 bags of sand to the borehole. They managed to fill the cavern and start drilling, but the sand was so unstable that they could not advance without the borehole collapsing. The borehole was abandoned.

Lessons learned:

1) Don’t use desagüe for casing.

2) Even mild sand infiltration can have a severe effect over time.

3) Sand infiltration doesn’t always clear itself up.

4) You can’t drill through material that you just filled in (as relates to digging past a rock layer, filling in the hole and then trying to drill past the fill material).

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Appendix C: Making cups leathers

The following instructions were provided to me via Tim from Marcelo Ramos Illanes. [My comments in brackets]

1) Soak the leather in water approximately 1-2 hours. [I soak mine longer. Then, to mold the leather, place the smooth side down on top of the large hollow cylinder and the small solid cylinder on top (on the rough side of the leather – the final cup leather should have the smooth side to the outside). Place this assembly in a vice and push the leather as far into the large cylinder as it will go. I then trim the remaining leather off, using the large cylinder as a guide. I use vice grips and the vice to remove the small cylinder.]

2) Once molded, let the cup dry completely.

3) Heat the paraffin to almost boiling. Place the cup in the paraffin for approximately 2-3 minutes. [Paraffin can be bought in the form of candles, but can also be bought by the kilo and you won’t have to fish the wicks out (available from the candle vendor at the corner of Bolivar and 6 de Agosto). Use a double boiler because paraffin is flammable.]

4) Once bathed in paraffin, the leather should be placed in the mold again so that it doesn’t deform.

5) Suggestion: buy a hole punch (sacabocado) according to the diameter of the pump stem. [Sacabocados can be bought from Barrio Chino, but the largest size I can find is for ½” nipples.]

Teo from San Julian told me that they use cera de oveja to treat their leathers. I never figured out what that is.

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Appendix D: Working with Concrete

Most concrete work for this project can be done by the beneficiarios. Some advice:

DO NOT use salty water for mixing concrete

Make sure your sand is clean or wash it prior to mixing

A 1:2:3 mix is usually fine (1 part cement, 2 parts sand, 3 parts gravel)

SIKA 3 may be an option if you want to pour during freezing weather as it purports to prevent freeze damage. We are unsure whether it would reduce the concrete’s strength.

If you need to calculate quantities for concrete work Wells Construction offers the following simple methodology:

1) Calculate the volume (V) of the item you wish to pour

2) Multiply the volume by 3/2 to determine the volume of dry materials (3/2 * V = Vdry)

3) Multiply the volume of dry materials by 1.1 to account for losses (1.1 * Vdry = Vtotal)

4) Add the components of your mix ratio (C:S:G). For example, for a 1:2:3 mix: 1+2+3=6

5) Calculate the volumes of cement, sand and gravel by multiplying the total volume (Vtotal) by its respective part of the mix, divided by the result of step 4. For example, for a 1:2:3 mix:

Vcement = Vtotal * 1/6

Vsand = Vtotal * 2/6

Vgravel = Vtotal * 3/6

6) The volume of cement (in cubic meters) can be multiplied by 30.12 to determine the number of bags of cement needed. Or the calculation can be done as follows:

# Bags of cement = Vcement (in m3) * (1000 L/m3) * (1 bag/33.2 L)

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Appendix E: Driller’s Vocabulary

Geology and soils

Acuífero or capa acuífera: aquifer

Arcilla: clay

Arena: sand

Barro: mud or clay

Capa: layer or strata of soil

Fino: fine

Grava: gravel

Gravilla: smaller gravel, such as pea gravel

Greda: clay

Grueso: coarse

Limo: silt (term is not commonly know in the campo)

Lodo: mud, or sometimes silt

Mediano: medium

Piedra: rock or stone

Roca: rock

Tools and materials

Achicador or cubeta sacalodos: bailer, or can be used for a sludging pipe

Alicate de presión: vice grips

Bentonita: bentonite, the highest quality clay that you can use for drilling

Broca: drill bir

Cernidor: sieve

Chupador or válvula de pie: foot valve

Cinta Aislante: electrical tape

Clefa: glue

Colador: screen, as in the well screen

Copla (sometimes cupla): coupling

Cuero: leather

Dado: die, such as those used to cut threads in metal pipe, or sockets for a socket wrench

Émbolo or pistón: piston

Émbolo de limpieza or bloque de limpieza: surge block

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Encamisado: casing

Empaquetadura: gasket

Entubado: casing

Esmerril: grinder, can be used to shave down goma gaskets

Fierro Galvanizado (F°G°): galvanized steel

Filtro: filter, such as the yute wrapped around the screen

Goma numático: the thin goma usually cut from a tire inner tube

Hojas: blades for hacksaw

Inyector de lodos: mud pump

Lima: file

Llave estilson: pipe wrench

Niple: nipple

Pico: the “beak” of the drilling stem; where the drilling mud and cuttings are spit out of for the Baptist drilling method

Pita: Rope

Prensa: vice

Rejilla: screen, as in the well screen

Roscas: pipe threads

Sierra mecánica: hacksaw

Soga: rope

Tallo de perforación: drilling stem

Tamices: sieves

Tarraja: pipe threader

Torre: tower, can refer to your tripod or bipod

Trapo: cloth or rag

Tubería, tubo: tube, pipe

Turril: barrel

Varilla: rod, as in the steel rod used to connect the lever arm to the ½” politubo for the Baptist pump

Drilling and installation

Achicar: to bail

Agua lodosa: muddy water

Agujero: borehole

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Bombear: to pump

Caudal: flow rate

Cernir: to sieve, to sort granular material using screens

Cortes: cuttings, the soil that you are cutting out of the borehole

Derrumbar(se): to collapse

Derrumbe: a collapse, as in a pipe or a borehole collapse

Desarrollo: development

Diámetro: diameter

Empaque con grava: gravel pack or filter pack

Entubar: to case the well

Flujo: flow

Fosa de asentamiento: sedimentation pit

Limpieza por oleaje: surging

Lodo de perforación: drilling mud

Noria: hand-dug well, typically with diameters of up to a meter

Pozo: well, borehole lined with casing

Ranura: slot, as in the slots cut into the casing to make the screen; also cortes

Túrbia: turbid

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