SPECIFICATIONS FOR GREEN RETAINING WALL / SLOPE SYSTEM ( GWASA 2006 )
GREEN WALL SYSTEM MATERIALS
Facing elements shall be ( Product brand ) as manufactured by, or under license from, ( company ). The units shall be (___product type ___). The elements shall be designed to interlock when installed according to the specifications so as to form a flexible, stable and plantable structure. The setback shall be ( _____ degrees ) from horizontal as allowed within the context of each style and shown on the construction drawings and system specifications. The color, if any, shall be chosen by the owner and all plant material shall be specified by a certified landscape architect.
The needs of the site and the goals of the “ mature” green wall/slope system should be completely assessed for geographic region, micro-climates within the system, media depth and composition, drainage, functional design intent, light conditions, aesthetics , relevant history of species use in similar applications, maintenance constraints and accessibility to the wall/slope face. Wall/slope plant location schematic per project stationing should be shown on the landscape plan.
The approved plant pallet shall consist of the following species @ specified percentages (_____approved plant list and growers_____)
The wall/slope system planting and initial maintenance and feeding program shall be performed by (__wall builder, landscape contractor, other__) in the following timeframe (_season and/or dates__) and maintenance shall begin (__timeframe and frequency_) .
The Facing Elements shall be (_____brand, style and size_____)
The Plantable facing element infill shall be (______topsoil, site soil or blended media @ __% organic material___)
The reinforced backfill material shall be compacted (rock or soil) in accordance with these requirements (__ properties__)
The structural reinforcement shall be (_product code_) geogrid or woven geosynthetic as indicated on the plans.
The geotextile filter fabric shall be Mirafi 140N or Amoco 4547.
The drainage composite shall be (_____brand or style___ ) as shown on the construction drawings
The leveling pad shall be constructed of compacted crushed rock similar to 1” minus, unless otherwise specified on the plans.
FOUNDATION
Foundation soil shall be excavated as required for the leveling pad and the reinforced fill zone to the depths and locations shown on the plan sheet or as directed by the site engineer. The exposed foundation soil shall be observed by the on-site soils engineer prior to construction to verify that the exposed material is suitable for a net design bearing pressure of (_per design__) psf and that the base of the excavation is free of loose soil, uncompacted fill, water, or frozen material. Undercut any unsuitable soil. Undercut areas shall be filled with crushed limestone and compacted to at least 95% of the material’s standard Proctor maximum dry density. Construct the crushed rock leveling pad to the lines and grades shown on the plans.
CONSTRUCTION
Install the first course of facing elements on the leveling pad. Install the next course per the published manufacturers’ recommendations. Pull elements forward to establish a ( angle required ) degree wall batter. Completely fill facing elements and any spaces between elements with ( ___soil or blended media __). Backfill behind the facing elements to the ends of the geogrids, and continue construction. Each lift must be stacked and completely backfilled before the next course is placed. No double stacking shall be allowed if it prevents proper soil placement at the facing.
( Refer to published ”Installation Guidelines” booklet for additional information )
REINFORCEMENT
The reinforcement shall be cut to design lengths and placed between the blocks at the elevations shown on the plans. The reinforcements primary strength direction will be directed perpendicular to the wall face (into the fill.) Reinforcement placed outside a plus or minus 4” zone of the placement design elevation will not be accepted. The geogrid shall be placed horizontally and lay flat on the reinforced fill area. Reinforcement shall be connected to the facing elements per manufacturers’ recommendations. Slack in the reinforcement shall be removed prior to placing additional backfill. Construction equipment shall not be operated directly on the reinforcement material.
BACKFILL
Wall backfill material shall be placed in maximum 8” loose lifts and compacted to at least 95% of the material’s maximum dry density as determined by the standard Proctor method. Backfill shall be placed, spread and compacted in such a manner that minimizes wrinkles and movement of the reinforcement. Field density testing shall be conducted by a qualified soils technician to verify that at least the minimum degree of compaction is being obtained.
The finished grade above the structure should include a drain swale and must be sloped in such a manner to drain all water away from the wall.
A document under review from the Green Wall and Slope Association