Abstract: Tee root zone mix installation involves careful planning and execution to limit subsurface drainage impacts while insuring even compaction.
I’ve seen a few contractors ruin subsurface grading and drainage piping by jamming tee rootzone mix without any concern for tee subgrades and piping. They try to increase production by doing the following:
- Driving a truck or trailer over the tee subgrade (the surface under the tee mix). Good construction methods incorporate the tee surface slope into the subgrade because this allows a true mirror image of the tee top slope while insuring positive subsurface water flow. A tire track or two will disrupt this sheet flow and crunch the drainage pipes. Note: we always install subsurface pipes under tee mix.
- Plowing out the tee mix with a bulldozer without any compaction technique.
We use these methods to install mix:
- Establish subgrade and finish grade stakes on the four tee corners (assuming you want a square tee). Calculate the amount of tee mix needed and transport this volume to the edge of the new tee. Stack the mix in a big pile on the edge of the tee. Don’t drive a truck or trailer over the tee edge. When the pile is complete, plow out a few inch lift of tee mix over the subgrade floor.
- Plow out another lift ( a lift is an even spread of soil i.e. a six inch lift) or two to establish design depth. This process creates even compaction-the dozer or excavator tracks do a nice job with this.
- Run a few strings connecting the four corners, and add or subtract mix as needed.
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