Jetting - EMAS method
EMAS well drilling is a method for drilling small-diamter tube wells by hand, up to 100 m deep. The drilling method is a hybrid between washboring, percussion and rotary drilling. It permits to drill through all kinds of loose soils, as well as consolidated materials and light rock. It will not, however, penetrate hard original rock or boulders (e.g. ancient river beds underground). The usual diameter of the tube well is 37 mm.
History and social context
The EMAS drilling method was developed by the Escuela Móvil de Agua y Saneamiento (Mobile School for Water and Sanitation, EMAS) in Bolivia. Project leader of EMAS in Bolivia is Wolfgang Eligius Buchner, born 1957 in Holzkirchen bei München.
EMAS was established in 1993, and has provided training for about 130 independent well builders in its branches in San Julian (1994) and in Puerto Pérez (1997). 20 students have been able to graduate from the licensed craftsman course. The well builders in Bolivia have founded a well builder organization.
During a three-month education, agricultural workers are trained to independently drill wells, build sanitary installations and market their skills in their local area depending on demand.
The need for large financial investments for well drilling and the building of line systems has traditionally prohibited the construction of large scale potable water systems in rural areas. Wolfgang Buchner adapted already accepted suction - and rinsing drilling methods to local conditions.
Suitable conditions
Advantages | Disadvantages/limitations |
---|---|
- Very simple and cheap equipment. - No need for machines. |
- Does not penetrate rock - slower than motorized drilling |
Wells as deep as 90 meters (approx.270 feet) can be drilled within 3-4 days without any machine employment and exclusively through the use of manual labor. Depths up to 100 m have been reached with the EMAS method. Most regions of South America (loam and sandy soils) are geologically suitable for this drilling method (predominantly rinsing or suction drilling).
This technique adapts best to loamy soils, consolidated materials and light rock. In sticky clays, the mud injection orifices in the bit can get blocked. In pure coarse sands, progress may be slow: the space between the drill stem and the well walls is relatively large, in relation to the slender drill stem, which makes for a slow upward flow. Sand may sink faster than it can be lifted out with the drilling fluid. In such conditions, it may be beneficial to (temporarily) switch to a sludging technique.
Technical specification
Operation
Drilling is continuous: the drill bit is normally not removed from the borehole until it is finished or work is interrupted. As a portion of the drill stem is entered, another length of ¾” (19 mm) metal pipe with reinforced threads is screwed on. Drilling fluid (mud, a suspension of ordinary clay or bentonite with an adequate density) is pumped down through the drill stem using a hand-operated mud pump. The drilling fluid comes back up around the drill stem, carrying broken-up material. Sand and small stones settle in a settling area dug in the ground, and the mud is recycled through the pump.
Percussion action is performed by lifting the drill with a lever, mounted on the drilling tower, and letting it fall down. Moreover, the drill is rotated half-turns in both directions, enhancing the grinding action of the bit.
The resulting hole diameter is about two inches, and wells are cased with cheap 1 1/2” (39 mm) PVC pipe. This can accommodate a 1 1/4” PVC piston pump, but if required, the upper portion of the well (down to about 1 m below the lowest expected water table) can be reamed to accommodate larger diameter pumps.
As the entire drill stem is metallic, the weight of the drill increases linearly with depth, so the deeper the well, the heavier the stroke, but stroke length is limited to about 30 cm by the lever.
No temporary casing is used. Upon reaching the desired depth, drilling fluid is removed from the hole by injecting progressively lower density mud. If unstable layers are present, however, this diluting can make the well collapse before it can be cased. In such cases it may be better to case the well with mud in it and evacuate the mud afterwards by pouring or injecting water into the casing (backwashing).
Maintenance
Manufacturing
The complete rig can be built locally in about any arc-welding workshop, using only materials found in ordinary hardware stores.
Cost
An EMAS drilling rig, fit to drill holes up to 30 m deep, can be built in Bolivia for about US$ 600 - 800. This includes the tower, mud pump and all essential non-common tools to operate and maintain it.
In most cases, the tube well is combined with an EMAS hand pump. In that case, the total cost per meter, including labor, materials, hand pump and 1 year warranty, in Bolivia amounts to about US$ 6. This is approx. 10 times more economical than the least expensive existing method.
An average well with a depth of 30 m costs approx. US$ 180 including an EMAS hand pump. This makes a surface covering supply of drinking water possible for municipalities and families in rural areas.
Country experiences
Manuals
Movies
External links
- www.emas-international.de
- www.practicafoundation.nl
- General info on well drilling www.rwsn.org
- nl.youtube.com/watch?v=MvebFHCjCvk
- Organisation http://www.waterforallinternational www.waterforallinternational ]
References
- This article is based on an article by Paul Cloesen, and on material from www.emas-international.de