permaculture

[Jack Rowe <jackrowe@compuserve.com>]

In Texas, we purchased materials for two 6,000+ gallon ferro-cement cistern
for under $700 per tank (labor was provided with workshop participants).
The walls were about 2-1/2 inches thick, and both Mollison and Alan Savory
assured me they were being built thinner in Australia and South Africa. 

The cisterns were 7-1/2 feet tall and 10 or 12 feet in diameter. Floors
were two layers of light-guage remesh, edges marked with a string compass
and the ends turned up about 6 inches to accept the walls. Walls were 2
layers of light-guage remesh, 1-1/2 widths tall (each roll is 5 feet wide,
great for tomato cages at about $2 per 2-1/2 foot diameter cage). Full
width alternated top and bottom in the two layers for overlap. #3 rebar
(3/8 inch dia) around the top edge. Then we used stucco mesh to hold the
cement. Roofs are needed to keep animals from drowning in tanks during dry
spells. 

Larger, 20,000 gallon cisterns (about 20 feet dia) are being built
commercially around Austin, TX and total costs for these thicker tanks
(around 4 - 5 inches) complete with pumps, pressure tank, UV systems,
filtration, etc are comparable to or below well costs. And, as Bobbi
mentions, water tables are in fact dropping and wells having to be
re-drilled frequently in the Austin area (big surprise!). 

Jack Rowe