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Pday 5, 2008 <br /> Mr. Ron Riach/JRR L'nginccring, lnc. <br /> L&A Job No. 8A043 <br /> Page 5 <br /> Sitc Preparation and Gencral Grading <br /> Vegetation within wnstruction limits of the block wall should be cleared and roots thoroughly <br /> grubbed. Topsoil and loose weathered sandy soils within the block wall footprint should be <br /> stripped down to firtn, nativc, dense sand soils. The base blocks of the wall should be founded <br /> on a minimum 6-inch layer of compacted 7/8-inch crushed rock base, placed over very-dense <br /> frcsh till soils. A silt fence should be erected along the downhill side of the construction area of <br /> the wall to keep sediment from being washed down ro adjacent properties. The bottom of the <br /> fihcr fabric should be anchored in a trcnch fillcd with gra�cl. <br /> Kcyway Trench <br /> Thc keyway trench for the block wall should be cut into native, undisturbed, very-dense, fresh till <br /> soils, capable of rendcring an allowable bcaring pressure of at least 3,000 psf. The soils exposed <br /> at bottom of the kcyway trcnch should be compacted to a non-yielding state witn a vibratory <br /> compactor. Over-excavation of unsuitable soils should be backf Iled with structural fill. A <br /> minimum G-inch laycr of 7/8-inch-minus crushed rock leveling base, compacted to a non- <br /> yiclding state, should be placed over bottom of the keyway trcnch. Thc base-course blocks are to <br /> be placed on this crushed rock base with an embedment at least 12 inches below the finish grade <br /> in front of the block wall. The precast wncrete blocks should be stacked tightly against each one <br /> anothcr. <br /> Urainagc Cunirul <br /> A minimum 6-inch perforatcd, rigid, PVC omin linc fitted in a nan-woven filter fabric sock <br /> should bc laid in the kcyway trcnch behind the baso-course blocks. Thc bottom of keyway trench <br /> ' and the drain line should have sufficicnt slopc (0.5 percent minimum) to gcnerate flow by <br /> graviry. The drain pipe should bc tighUincd to drain into a storm sewer or a suit�.ble stormwater <br /> disposal facility. A minimum 12-inch-thick (horizontally) veriical drainage blanket constructed <br /> LIU & ASSOCIA'i'ES, IN�C. <br /> 5�,� <br />