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<br />e <br /> <br />e <br /> <br />e <br /> <br />DRAINAGE CRITERIA MANUAL (V. 2) <br /> <br />HYDRAULIC STRUCTURES <br /> <br /> <br />Photograph HS-6 <br /> <br />Detail of the grouted sloping boulder drop with a trickle channel section creating the sight <br />and sound of cascading water. <br /> <br />Grouted boulder drops should be constructed of uniform-size boulders having a minimum dimension as <br />specified in Table HS-4. All boulders are grouted in place to 50% of their height through the approach, <br />sloping face, and basin areas of the drop. Figure HS-7 illustrates the general configuration of the GSB <br />drop. It is important that the grout depth extends from the subgrade up to one-half of the nominal rock <br />size, but under no circumstances higher than two-thirds of the minimum rock dimension. Requirements <br />for the grout are given in the MAJOR DRAINAGE chapter of this Manual. Adequate seepage provisions <br />are critical to the design success whenever drop height exceeds 5 feet. The following outlines the <br />fundamental oesign steps with some additional guidelines. <br /> <br />1. Hydraulics should be completed as described in Section 2.3 whenever the drop height exceeds 5 <br />feet. Otherwise, use critical depth to size the boulders, using the boulder sizing procedure <br />described below. <br /> <br />06/2001 <br />Urban Drainage & Flood Control District <br /> <br />HS-21 <br />