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objectionable materials will be removed to avoid interference. Sediments accumulated against <br />berms will be periodically cleaned. Maintenance activities will ensure drat breaching hazards • <br />are wrrected immediately. <br />Flow structures may be unlined or lined for erosion protection. When lining materials are <br />specified they may be vegetative, reinforced substrate matrix materials with vegetation, <br />netting, various erosion control fabrics, riptap or some combination of these materials. <br />Reconstructed channels may use biotechaical stabilization measures for stabilization. Normally <br />these structures will be constructed from materials readily available on site. If local materials <br />are inadequate, special construction materials will be imported from outside the ama for specific <br />applications. Adequate compaction is cridcal to structure function and appropriate linings are <br />requued to protect the structures from erosion. Particular attention will be paid to allowable <br />velocities for specific lining materials. <br />In recLrimed areas, reconstructed drainage channels will be placed as necessary to route runoff <br />through disturbed and restored areas and into undisturbed channels. ;stabilization measures <br />will be judiciously employed to ensure long-teen stability of reconstructed channels and <br />transition canes to undisturbed features. To the extent practicable, smooth channel transitions <br />will be made between reconstructed and undisturbed areas. <br />Adequate constnrction procedures and mateaial quality control are critical to concentrated flow <br />structure performance. Construction inspections will be performed to ensure integrity of flow <br />structures. Materials used on the project will mew or exceed structrrre specifications. A <br />qualified engineer will develop site-specific designs for structures where typical designs are <br />inadequate. <br />Unlined channels will be used as temporary structures. Permanent channels will have at a <br />minimum a vegetation lining. Concentrated flow structures will be mair;tained as necessary to , <br />ensure function. Permissible velocity will be used to establish channel lining requirements. <br />Channel erosion control linings or gradient control structures will be used where necessary to <br />ensure stability and to protect against excessive erosion of wncentrate~ flow structures. Where <br />such gradiems are exceeded, appropriate lining materials will be used. <br />Vegetation linings provide the next level of stability over unlined chorine:ls. Vegetation linings <br />are relatively inexpensive to establish providing site moisture conditions allow adequate <br />growth. Vegetation species selection is very important in the establishment of an adequate <br />vegetation lining. Specres used may include grasses, sedges, rushes, bullrushes, cattails or <br />other hydrophyllic, mat forming plant species. Higher velocity flows :may use mat or matrix <br />reinforced vegetation linings to improve root anchoring. Such subsurface reinforcing materials <br />will be applied per manufacturers' specifications. Erosion control blankets may be used to <br />improve surface stability of a concentrated flow structure during the establishment of vegetation <br />linmgs. Various erosron control blankets are manufactured for different types and lengths of <br />application. When erosion control blankets are required to establish vegetation in flow <br />structures, the type used will be selected for the site according to anticipaaed plant establishmem <br />periods and assceiated erosion protection needs. <br />Rip-rap may be used to line concentrated flow structures where steeper channel gradients are <br />necessary. Rip-rap sizing is critical to the success of this lining method. Materials used for <br />rip-rap luungs will meet or exceed the specifications for rock sizing. Riprap sizing will be <br />determined using standardly accepted hydrologic engineering methods. S-zrng requrrements <br />for riprap will be specified in purchase orders and materiaLt supplied subject to sizing <br />verification. Angular rock will be preferred over smoother materials. Geotextile fabric and <br /> <br />B-2 <br />