Saturday, September 20th, Buzz Durham, Herve Delisma, Lucien Joseph and I headed down the highway from Papaye, through Port au Prince, to Léogâne, to lead a workshop there on in-ground cisterns, a technique for capturing rainwater (micro-catchments) that I had learned from members of COSECHA, a non-profit rural development organization located in southern Honduras. COSECHA does not appear to have a web-site, but here are a couple of links to articles about their work:
COSECHA-what we have learned in five years
COSECHA-What we have learned in five years
The workshop was hosted by the Organization for Development in Léogâne (ODEPOL for its name in Haitian Creole), one of our partners in the FONDAMA Yard Garden Program since April 2012.
Here are pictures and a rough idea of the process:
Sunday afternoon, as we were frantically getting the first hole ready, we got help from neighbors, both tools and labor.
You can see that we have cut out all around on top and laid some gravel down. You cut out the extra soil on top to lay a border and you do it carefully so that you do not disturb the 3/8" re-bar on top. The gravel was because we had it as what was left after sieving the sand.
The ideal is to use river sand, well washed, without sediment. What we were able to get by Tuesday AM was white sand, from a nearby quarry. I have been led to understand that the white sand corrodes the metal embedded in the mortar more quickly and reduces the life of the structure.
In any case, my original instructors came from the countryside where river sand was very accessible.
The depth came to just over half a meter (0.6 m) in part because we lost some depth from the top, but also because we poured a good thick base--at least 5 cm (2 inches) thick of cement, sand and gravel. After pouring this, we capped the base off with the same rich cement mix we used to finish the sides. This mix seals the cement so that water is not lost through the base or the walls.
The reality is that I have never been part of building one of these cisterns where we had an easy time of it. There is always something off with the sand or the hole, or something else.
The actual costs for the materials for the first cistern. We ended up using 2 pieces of 20' lengths of 3/8" re-bar; 5 pieces of 20' lengths of 1/4" re-bar; about 14 pounds of binding wire (fil aligati) #18; half a sheet of "siloteks", a pretty cheap material usually used for paneling ceilings (to mix up the mortar in the hole, to keep dirt out); 6 wheelbarrows of sand; and 4 sacks of cement. Total cost HTG 3,625--around $US 80.
The actual capacity of the cistern, when we did the final measurements, was 1.9 m3 or 1,900 liters (about 500 gallons).
We compared the cost to buying plastic barrels, which hold 60 gallons. Our cistern holds the equivalent of around 8 plastic barrels, each of which sells for HTG 1,500 in Port au Prince. Eight barrels would cost HTG 12,000. So our cistern is considerably cheaper than buying the equivalent in plastic barrels.
If we were to pay for a skilled mason to build the same cistern, and pay for the hole to be dug, we would probably lose most, if not all of the difference. The serious advantage of this type of water catchment system is the fact that pretty much anyone can learn to do it, and then pass it on.
That said, with Buzz's experience in pretty much everything, we were able to offer quite a few points on how to improve the success of this type of cistern. One simple but tedious point we discovered from Buzz is that to acquire maximum strength, the cement should be maintained humid for at least a week, preferably two. That means splashing water on the sides four or five times a day or more.
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