large dromadary bags would be good for packing the water in. peeps use them for camping for showers and such. They will fit in a back pack and wont leak. you can get them from campmor. I would just use water crystals which slowly give off water. 1 lb of Water-Keep crystals can absorb 47 gallons of rain water and 30 gallons of tap water. Instead of packing in heavy soil I would concentrate my efforts on tilling the soil thats there and packing in mulch, water crystals, extended release ferts, some vermiculite. This would keep the soil better than just putting in potting soil.

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It has to be time to get active. We are facing a new Vietnam after all.