Installing the Barrel
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mixing the concrete |
Once the hole has been prepared, mix 100 lbs of quick-set concrete with water, stirring constantly. We mixed concrete in a rectangular flat-bottomed mixing tray, using a garden hoe. The concrete should be mixed to a smooth, even consistency, approximately that of oatmeal. Pour the concrete into the hole, level slightly with the hoe, and then set the barrel into the concrete. Press down and rotate the barrel to ensure that it seats well into the wet concrete. Put the lid on the barrel, place a bubble level on the lid, and move and reseat the barrel until it is level.
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leveling the barrel |
In cool, wet conditions it may be necessary to wait until the concrete begins to set; in warm, dry conditions it should begin to set almost immediately. Mix a further 50 lbs of quick-set concrete to the same consistency as above, and pour into the barrel. Using a small concrete finishing trowel, level and smooth the surface of the concrete. A smooth, level surface is important here, as this concrete will be the surface on which the seismometer will rest.
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pouring concrete into the barrel |
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smoothing the concrete |
Once the concrete has adequately set, you can begin backfilling the hole. First put the lid on the barrel, to keep dirt out and help prevent the barrel from deforming during backfilling. Then, selecting dirt with no large rocks from your pile, fill in around the barrel. Pause at intervals and tamp down the dirt with the flat end of the rock bar or a shovel handle. Fill to ground level, so that the top of the barrel is slightly above the level of fill dirt.
Now it is time to Fence the Site...