Building a large wall next to large trees without damaging the trees
Project: wall construction
Location: St. Augustine, Florida on Old Quarry Road
When: Summer, 2007
Trees: 5 live oaks (Quercus virginiana) ranging from 24 to 36 inches DBH
The roots are located where they will cross the wall footing
The initial wall foundation trench is opened within the dripline with the Air Spade air excavation tool. A small backhoe with an operator who understands the importance of roots works on areas of the trench outside the dripline. Note the irregular location of roots even close to the base of the tree. You never know where the roots are unless you look. Once roots are located, the widening can be done by hand and with the help of a carefully operated small back hoe.
The trench is widened and the footing is poured along except where the larger lateral roots are located.
The trench is widened and the concrete foundation is poured where no large lateral roots are found. These lateral roots will be saved and a lintel (bridge) will be installed over the roots.
The wall construction is nearly complete. The lintel was precast concrete in this case. The lintel could also constructed of steel.
The wall is nearly complete with the lintel bridging the lateral roots close to the tree trunk.
The wall is finished. The height of the gap between the soil and lintel could have been shorter, in my opinion. Most of the other lintels were at ground level. The area of the opening will be filled in with mulch.
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The finished wall.
The usually sandy soil in this part of Florida was covered by a 24-inch thick layer of shells which turned out to be a 1000-year-old Indian shell midden. It made excavation difficult. Because of the number of historic sites in the City of St. Augustine, an archeological protection ordinance requires an archeological team be present during the excavation on construction sites.
