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objectionable materials will be removed to avoid interference. Sediments accumulated against berms will be periodically cleaned. Maintenance activities will ensure that breaching hazards are corrected immediately. Flow structures may be unlined or lined for erosion protection. When lining materials are specified they may be vegetative, reinforced substrate matrix materials with vegetation, netting, various erosion control fabrics, riptap or some combination of these materials. Rewnstrtrcted channels may use biotechnical stabilization measures for stabilization. Normally these structures will be constructed from materials readily available on site. If local materials are inadequate, special construction materials will be imported from outside the area for specific applications. Adequate compaction is critical to structure function and appropriate linings are requitd to protect the structures from erosion. Particular attention will be paid to albwable velocities for specific lining materials. In reclaimed azeas, reconstructed drainage channels will be placed as necessary to route runoff through disturbed and restored areas and into undisturbed channels. Stabilisation measures will be judiciously employed to ensure long-term stability of reconstructed channels and transition zones to undisturbed features. To the extent practrcable, smooth channel transitions will be made between reconstructed and undisturbed azeas. ' Adequate construction procedures and material quality control are critical to concentrated flow structure performance. Construction inspections will be performed to ensure integrity of flow structures. Materials used on the project will meet or exceed structure specificatrons. A ' qualified engineer will develop site-specific designs for structures where typical designs are madequate. ' Unlined channels will be used as temporary structures. Permanent channels will have at a minimum a vegetation lining. Concentrated flow structures will be maintained as necessary to ensure function. Permissible velocity will be used to establish channel lining requirements. Channel erosion control linings or gradient control structures will be used where necessary to ' ensure stability and to protect against excessive erosion of concentrated flow structures. Where such gradients are exceeded, appropriate lining materials will be used. ' Vegetation linings provide the nett level of stability over unlined channels. Vegetation linings are relatively inexpensive to establish providing site moisture conditions allow adequate growth. Vegetation species selection is very important in the establishment of an adequate vegetation lining. Species used may include grasses, sedges, rushes, bullmshes, cattails or other hydrophyllic, mat forming plant species. Higher velocity flows may use mat or matrix reinforczd vegetation linings to improve root anchonng. Such subsurface reinforcing materials will be applied per manufacturers' specifications. Erosion control blankets may be used to ' improve surface stability of a concentrated flow structure during the establishment of vegetation linings. Various erosion control blankets are manufactured for different types and lengths of application. When erosion control blankets are required to establish vegetation in flow ' structures, the type used will be selected for the site according to anticipated plant establishment periods and associated erosion protection needs. ' Rip-rap may be used to line concentrated flow structures where steeper channel gradients are necessary. Rip-rap sizing is critical to the success of this lining method. Materials used for rip-rap linings will meet or exceed the specifications for rock sizing. Riprap sizing will be determined usmg standardly accepted hydrologic engineering methods. Srzing euquirements ' for riprap will be specified rn purchase orders and matenals supplied subject to sizing verification. Angulaz rock will be preferred over smoother materials. Geotextile fabric and B-2 1