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3.05 BASE COURSE PREPARATION <br />A. Place base materials to the depths and widths shown on the Drawings, upon undisturbed soils, or <br />foundation soils prepared in accordance with Article 3.04. <br />1. Extend the leveling pad laterally at least 6 inches in front and behind the lowermost concrete <br />retaining wall unit. <br />2. Provide aggregate base compacted to 6 inches thick (minimum). <br />3. The Contractor may at their option, provide a concrete leveling pad as specified in Subparagraph <br />2.0l.C.2, in lieu of the aggregate base. <br />4. Where a reinforced footing is required by local code official, place footing below frost depth. <br />B. Compact aggregate base material to provide a level, hard surface on which to place the first course of <br />units. <br />C. Prepare base materials to ensure complete contact with retaining wall units. Gaps are not allowed. <br />3.06 ERECTION <br />A. General: Erect units in accordance with manufacturer's instructions and recommendations, and as <br />specified herein. <br />B. Place first course of concrete wall units on the prepared base material. Check units for level and <br />alignment. Maintain the same elevation at the top of each unit within each section of the base course. <br />C. Ensure that foundation units are in full contact with natural or compacted soil base. <br />D. Place concrete wall units side-by-side for full length of wall alignment. Alignment may be done by using <br />a string line measured from the back of the block. Gaps are not allowed between the foundation concrete <br />wall units. <br />E. Place 12 inches (minimum) of drainage aggregate between, and directly behind the concrete wall units. <br />Fill voids in retaining wall units with drainage aggregate. Provide a drainage zone behind the wall units <br />to within 9 inches of the final grade. Cap the backfill and drainage aggregate zone with 9 inches of <br />impervious material. <br />F. Install drainage pipe at the lowest elevation possible, to maintain gravity flow of water to outside of the <br />reinforced zone. Slope the main collection drainage pipe, located just behind the concrete retaining wall <br />units, 2 percent (minimum) to provide gravity flow to the daylighted areas. Daylight the main collection <br />drainage pipe through the face of the wall, and/or to an appropriate location away from the wall system at <br />each low point or at 50 foot (maximum) intervals along the wall. Alternately, the drainage pipe can be <br />connected to a storm sewer system at 50 foot (maximum) intervals. <br />G. Remove excess fill from top of units and install next course. Ensure drainage aggregate and backfill are <br />compacted before installation of next course. <br />H. Check each course for level and alignment. Adjust units as necessary to maintain level and alignment <br />prior to proceeding with each additional course. <br />I. Install each succeeding course. Backfill as each course is completed. Pull the units forward until the <br />locating surface of the unit contacts the locating surface of the units in the preceding course. Interlock <br />wall segments that meet at corners by overlapping successive courses. Attach concrete retaining wall <br />units at exterior corners with adhesive specified. <br />J. Install geosynthetic reinforcement in accordance with geosynthetic manufacturer's recommendations and <br />the shop drawings. <br />1. Orient geosynthetic reinforcement with the highest strength axis perpendicular to the wall face. <br />2. Prior to geosynthetic reinforcement placement, place the backfill and compact to the elevation of <br />the top of the wall units at the elevation of the geosynthetic reinforcement. <br />3. Place geosynthetic reinforcement at the elevations and to the lengths shown on the Drawings. <br />4. Lay geosynthetic reinforcement horizontally on top of the concrete retaining wall units and the <br />compacted backfill soils. Place the geosynthetic reinforcement within one inch of the face of the <br />concrete retaining wall units. Place the next course of concrete retaining wall units on top of the <br />geosynthetic reinforcement. <br />5. The geosynthetic reinforcement shall be in tension and free from wrinkles prior to placement of the <br />backfill soils. Pull geosynthetic reinforcement hand -taut and secure in place with staples, stakes, <br />or by hand -tensioning until the geosynthetic reinforcement is covered by 6 inches of loose fill. <br />6. The geosynthetic reinforcements shall be continuous throughout their embedment lengths. Splices <br />in the geosynthetic reinforcement strength direction are not allowed. <br />5-02832 <br />