Wednesday, January 28, 2009

About Hand-Dug Wells

There are three types of water solutions that charity: water typically implements in Ethiopia – hand dug wells, shallow boreholes and spring protections. Our partners who build water solutions will always determine the best solution based on the specific situation. Most of the solutions in Ethiopia are hand dug wells that can go as deep as about 25-30 meters (about 100 feet). They are generally the most inexpensive solution so whenever there is sufficient water near the surface a hand dug well is the best solution. This will describe how our partner in northern Ethiopia – REST – builds hand dug wells.
A REST hydrologist will identify the site for the well and the local community will start digging the hole for the well. They will dig down to about three meters depth on their own. At that point local workers will be trained and managed by a REST technician. A tripod is placed over the hole that is used to raise and lower equipment into the well. In general, one laborer will be in the hole breaking up the dirt and rock; another will load the dirt and rock into a bucket; the third laborer will raise the bucket, dump the contents and send it back down. When they reach rock that can’t be broken with a pickaxe the REST technician will use dynamite to loosen the rock.
Frequently, the hole will have layers of soil and rock that helps to keep the walls of the hole stable and prevent any collapse. In this case the laborers may build the interior wall of the well out of stone as they dig. This means that they are building the wall from the top down. If the hole is mostly unstable soil, then a stronger wall is needed. REST will bring forms to the site to make concrete cylinders. They will then use cement that they have brought to the site combined with local gravel to make the cylinders. The cylinders are then stacked in the hole to make the wall. As the hole is dug the cylinders will descend and new cylinders are stacked on top. Each cylinder takes two weeks to harden after it is made and there are generally two molds on site so the site is limited to about six feet of progress every two weeks. The concrete cylinders or the stone wall will continue until the hole reaches solid rock at which point the diameter of the hole will narrow and digging will continue. There will be gaps in the wall to allow water into the well.
At some point water will start to seep into the hole. The point of the well is to get water and the deeper the hole is the more reliable the water supply will be. However, during construction the water creates a problem so a pump connected to a generator is used to pump the water out of the hole during construction. By this point it’s pretty messy work in the hole with water sloshing around mixing with soil and bits of rock to make a chunky mud. When the hole reaches it’s final depth, gravel is placed between the walls of the well and walls of the hole to filter soil out of the water seeping into the well. Gravel is also put at the bottom of the well for the same reason.
When the hole is completed a slab of reinforced concrete is placed over the top. The concrete holds the pump and seals the well from contaminants. A pipe is run from the pump down to near the bottom of the well. A drain is built into the concrete slab to take away overflow water. Finally a barrier – usually a stone wall – is built around the well to keep out animals. At this point the well is ready for use.
On our first day we saw a well that had just been completed. The water did not look completely clean. As the well gets used all of that soil will eventually get flushed out and the water will look and be safe. No filtration system is necessary because the soil effectively filters out contaminants as the water seeps down.
In general, REST will provide the technology necessary to site and build the well. That includes the generator and pump, the cement, the hand pump and the technicians. They will also pay local laborers about 15-20 Birr (about $2.00) per day to do the laborer. They may also pay a local mason up to 30 Birr ($3.00) per day to carve the stones necessary for walls. The local community will provide the labor to start the digging, they will often have to carry supplies in form the nearest road – often a considerable distance – or they will build a road so that trucks can get in. The local community will also provide all of the stones necessary for walls and the gravel for making concrete.
After the well is built REST will provide training for well maintenance and ensure that there is a well committee to manage a monitor the well. Most communities will pay a well manager to manage the well including locking it when it is not in use. A carefully maintained well will last for a long time - charity: water estimates twenty years, but it can be much longer. In Ethiopia the typical cost of a hand dug well is about $3,000 - $4,000 dollars and is intended to serve about 400 people – a cost of about $10 per person.

No comments:

Post a Comment