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7 <br /> • � � � .�� � C?/�G�-r�1�) �. <br /> � - <br /> 5-2.2 Roof Runoff Infiltration System Sizing <br /> rench Dimensions Required Length of Trench per 100 square feet of Roof Surface** <br /> width depth* coarse sand sand loamy sand sandy loam loam <br /> 1 S ft. 1.0 ft. 0.72 1.44 3.38 5.48 7.88 <br /> 1.5 ft. 0.56 1.10 2.54 4.08 5.80 <br /> 2.0 ft. 0.45 0.89 2.06 3.30 4.60 <br /> 2.5 ft. 0.38 0.75 1.72 2.76 3.84 <br /> 3.0 ft. 0.32 0.65 1.49 2.38 3.28 <br /> 2.0 ft. 1.0 ft. 0.60 1.19 2.68 4.34 6.22 <br /> 1.5 ft. 0.47 0.92 2.04 3.28 4.62 <br /> 2.0 ft. 0.39 0.76 1.66 2.66 3.70 <br /> 2.5 ft. 0.33 0.65 1.41 2.26 3.10 <br /> 3.0 ft. 0.28 0.56 1.23 1.94 2.68 <br /> 2.5 ft. 1.0 ft. 0.51 1.01 2.24 3.64 5.14 <br /> 1.5 ft. 0.41 0.79 1.71 2.76 3.88 <br /> 2.0 ft. 0.34 0.66 1.40 2.26 3.14 <br /> 2.5 ft. 0.29 0.56 1.20 1.90 2.66 <br /> 3.0 ft. 0.25 0.49 1.05 1.65 2.30 <br /> 3.0 ft. l.0 ft. 0.44 0.88 192 3.10 4.40 <br /> 1.5 ft 036 0.69 1.47 2.38 3.36 <br /> 2.0 ft. 0.30 0.58 1.21 1.94 2.74 <br /> 2.5 ft. 0.25 0.50 1.04 1.65 2.32 <br /> 3.0 ft. 0.22 0.44 0.9] 1.43 2.00 <br /> 3.5 ft. 1.0 ft. 0.39 0.78 1.68 2.72 3.88 <br /> 1.5 ft. 0.32 0.62 1.29 2.08 2.96 <br /> 2.0 ft. 0.26 0.51 1.07 1.70 2.42 <br /> 2.5 ft. 0.23 0.44 092 1.45 2.06 <br /> 3.0 t 0.20 0.39 0.81 .27 1.79 <br /> 4.0 ft ].0 ft. 035 0.70 1.49 2.42 3.46 <br /> 1.5 ft. 0.28 0.55 1.15 1.85 2.66 <br /> 2.0 ft. 0.24 0.46 0.95 1.52 2.18 <br /> 25 ft. 0.20 0.40 0.82 130 1.86 <br /> 3.0 ft. 0.18 0.35 0.73 1.13 1.62 <br /> *Depth refers to the depth of washed rock, not depth from surface <br /> **Soil textures to be determined using the results of soil gradation tests and the USDA Textural Triangle. <br /> Example: An infiltration trench 3.5 feet wide and 2 feet deep, dug in sandy loam soils, for runoff from <br /> a 1500 square foot roof, would be 25.5 feet long (chart value of 1.70 multiplied by 15). <br /> 'Y <br /> �J�� •��� r L�� <br /> � D <br /> � <br /> �� � � 5 � <br /> 3-2-10 � �� <br /> � Z � <br /> , <br />