Laserfiche WebLink
this junction to help transport flow to the yard (sediment ponds) and away from <br /> the pile. See the design drawings for details_ <br /> In addition to the main, central tlrain it is recommended that French drains be <br /> constructed on both sides at '100-foot intervals for the 800 ft of reaches 2 antl 3. <br /> These French tlrains should consist of 4" pertorated pipe centered in a bedding <br /> zone 24" x 24", trenched into the natural surtace. The bedding should be a well <br /> graded gravel with a maximum rock size of/. ". The finger drains should eMend <br /> through the side of the underdrain filter liner and into the drain. Laterally they <br /> should extend across the valley floor to the breaKpoint in the slope with the valley <br /> side walls. <br /> If at anytime during salvaging of topsoil or any other construction activity, a <br /> spring or seep is encountered, an atlditionaf lateral French drain shall be installed <br /> from the seep to the underdrain. It shall be constructed as described above. <br /> Tha underdrain is wrappetl in a porous filter cloth (designed to allow water to <br /> enter but Keep out fine sediment) and filled with rock. No more than 'IO% of the <br /> rock may be less than '12" in size and no single rock may be larger than 25% of <br /> the depth of the drain. Flow from the drain will enter the lower intercept channel <br /> and subsequently be diverted to the pontls for settling. <br /> January 199R <br />