Water Harvesting

LWH currently builds a tank design with ferrocement. A 2" - 3" thick base of concrete is laid with four pieces of rebar woven together with tie wire and two pvc outlets, one for cleaning and one for consumption. 1 tie wire pig tail extends off each tip of rebar. A grain sack form, filled with corn husks, sawdust, pine needles, straw, etc.. is laid on top of the concrete base and a 1/2 - 3/4" thick layer of mortar (3:2 sifted river sand to cement) is troweled up the surface of the form to a lid. Three, braided tie wire rings are laid around the lid, each progressively getting bigger, and the tie wire pig tails are continued to the smallest ring. Tie wire is wrapped around the tank with a two finger (approx 1 1/2" - 2") distance between each pass from the base to the top of the vertical wall. A second layer of 3:1 mortar is laid on top of the first layer, sandwiching the tie wire inside. Plastic sheeting or wet cloth should cover the fresh ferrocement and keep it moist for a week or so. After a week or so, the grain sack form is emptied and pulled out of the tank. Neat cement, or other appropriate sealant is then painted on the inside of the tank. The tank should be filled the following day and be kept full for 3 more weeks. Water may leak out while the cement is curing. These ferrocement water tanks store around 780 gallons for a cost of Q350 ($44). During the rainy season (May-Oct.), gutters with a first flush system (which keeps debris from entering the storage tanks) are added to collect clean water to keep the cisterns full by simply harvesting rainwater.

We also work with different EWB chapters in Comalapa's villages. We are currently realizing a rainwater harvesting system in Simajuleu, Comalapa's largest village, at their school that will store enough water to keep the students and teachers with enough water throughout the dry season (Nov-April) with EWB Minnesota. By taking advantage of the roof area on the school buildings, enough rainwater can be stored in the 34,400 gallon concrete cistern (to be finished the 2nd week of September 2009), for 6 months. Plans are afoot to continue the project with an improved distribution line running throughout the village that should provide each house with enough water for daily consumption.