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3.0 Trench Installation Sizing and Guidelines <br /> 1. Ensure all components leading to the GSF system are installed properly. Septic tank effluent filters are <br /> required with the GSF system. <br /> 2. Determine the number of GSF Modules required using the trench sizing example. <br /> 3. Prepare the site. Do not install a system on saturated ground or wet soils that are smeared during <br /> excavation. Keep machinery off infiltrative areas. <br /> 4. Plan all drainage requirements above (up-slope) of the system. Set soil grades to ensure that storm <br /> water drainage and ground water is diverted away from the absorption area once the system is <br /> complete. <br /> 5. Excavate the trench; prepare the receiving layer to maximize the interface between the native soil and <br /> specified sand. <br /> 6. Minimize walking in the trench prior to placement of the specified sand to avoid soil compaction. <br /> 7. Place specified sand in a 6" lift and stabilize by foot, a hand held tamping tool or a portable vibrating <br /> compactor. The minimum stabilized height below the GSF module must be level at 6". <br /> 8. Place GSF modules with PAINTED STRIPE FACING UP, end to end on top of the specified sand along <br /> their 4-foot length. <br /> 9. A standard 4-inch perforated pipe, SDR 35 or equivalent, is centered along the modules 4-foot length. <br /> Orifices are set at the 4 &8 o'clock position. <br /> 10. All 4-inch pipes are secured with manufacturers supplied wire clamps, one per module. <br /> 11. (Pressure Distribution Systems) Insert a pressure pipe (size per design and code) into the standard 4- <br /> inch perforated pipe. The pressure pipe orifices are set at the 12 o'clock position as shown in Figure <br /> 13. Each pressure lateral will have a drain hole at the 6 o'clock position. Each pressure lateral shall <br /> include sweeping cleanouts at the terminal ends and be accessible from grade. <br /> 12. Cover fabric substitution is not allowed. The installer should lay the Eljen provided geotextile cover <br /> fabric lengthwise down the trench, with the fabric fitted to the perforated pipe on top of the GSF <br /> modules. Fabric should be neither too loose, nor too tight. The correct tension of the cover fabric is <br /> set by: <br /> a. Spreading the cover fabric over the top of the module and down both sides of the module <br /> with the cover fabric tented over the top of the perforated distribution pipe. <br /> b. Place shovelfuls of Specified Sand directly over the pipe area allowing the cover fabric to <br /> form a mostly vertical orientation along the sides of the pipe. Repeat this step moving down <br /> the pipe. <br /> 13. Place the sand extensions along both sides of the modules edge. A minimum of 6 inches of Specified <br /> Sand is placed at the beginning and end of each trench. <br /> 14. Complete backfill with a minimum of 6 inches of clean porous fill measured from the top of the <br /> distribution pipe. Backfill exceeding 18 inches requires venting at the far end of the system. Use well <br /> graded native soil fill that is clean, porous and devoid of large rocks. Do not use wheeled equipment <br /> over the system. A light track machine may be used with caution, avoiding crushing or shifting of pipe <br /> assembly. <br /> 15. Divert surface runoff from the system. Finish grade to prevent surface ponding. Topsoil and seed <br /> system area to protect from erosion. <br /> 2022 California Design&Installation Manual Page 14 www.eljen.com <br />