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3.0 Trench Installation Sizing and Guidelines <br /> Trench Example: <br /> House size: 3 Bedrooms <br /> Design Flow: 450 gpd <br /> Soil Description: Sandy Loam, Blocky, Moderate Structure <br /> Absorption Field Type: Trench <br /> Distribution Type: Gravity or better <br /> Unit Used: A42 <br /> Calculate Minimum Absorption Area <br /> Lookup loading rate from Table 3 and determine the loading rate: <br /> Soil Texture Maimum Soil <br /> (per the USDA soil classification Soil Structure Shape Grade Application Rate <br /> system) (gpd/ft2) <br /> Massive Structureless 0.2 <br /> Platy Weak 0.2 <br /> Coarse Sandy Loam,Sandy Loam Moderate, Strong Prohibited <br /> Prismatic, Blocky, 0.4 <br /> Granula Moderate, Strong 0.6 <br /> Absorption Area: Design Flow = Loading Rate <br /> 450 gpd = 0.6 gpd/ft2 = 750 ft2 <br /> Calculate Number of Modules Required <br /> Number of units required =Absorption Area = Square Foot per Module <br /> A42 Units required (17 ft2 per module) <br /> 750 ft2= 17 ft2/ module = 44.1 Modules <br /> Round to: 45 Modules <br /> Calculate Minimum Trench Length <br /> 45 Units x 4 ft/unit= 180 linear ft <br /> Trench Width <br /> 3 ft <br /> Final Dimension Layout <br /> (Note: System layout and number of rows will vary based on site constraints) <br /> A42 <br /> Min. Product Length* 180 ft <br /> Trench Width 3 ft <br /> Minimum Number of Units 45 Modules <br /> Min. System Area 543 ft2 <br /> *(note: 6 inches of sand required at each end of trench) <br /> 2022 California Design&Installation Manual Page 12 www.eljen.com <br />