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<br />CHAPTER 5: INFILTRATION TRENCHES <br /> <br />Infiltration trenches are an adaptable 8MP that effectively remove both <br />soluble and particulate pollutan"t.s. As with other infiltration systems) <br />trenches are not intended to trap c.oarse sediments. Grass buffers (for <br />surface trenches) or special inlets (for underground trenches) must be <br />installed to capture sediment before it enters the trench. Depending on the <br />degree of storage./exfiltration achieved, trenches can provide groundwater <br />recharge, low flow augmentation and localized streambank erosion control. <br />Individual trenches are primarily an on-site control, and are seldom <br />practica.l or economical on sites larger than 5 or 10 acres. Trenches are <br />only feasible when s.oils are permeable and the water table and bedrock are <br />situated well below the bottom of the trench. Aside from regular inspections <br />and more rigorous sediment and erosion control, trenches have limited routine <br />maintenance requirements. However, trenches. will prematurely clog if <br />sediment is not kept out before, during and after construction of a site.' If <br />a trench does become severely clogged, partial or complete replacement of the <br />structure may be required. ' <br /> <br />Figure 5.1: Schematic of an Infiltration Trench <br /> <br />Wellcap <br />...... <br /> <br />Observation Well <br /> <br /> <br />Sand Filler (6.12 Feet Deep) <br />or Fabric equivalent <br /> <br />'" <br />Runod E:dutrate:s <br />, Through Undisturbed Subsoils <br />with II Minimum fe 01 0.5 Inches/Hour <br /> <br />I <br /> <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />II <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br /> <br />I <br />