Ordinance 2213-97 - Laserfiche WebLink

4.3 Mitigation Measures 4.3.1 General Mitigation Measures 1. The following Best Management Practices (BMPs) must be followed for all construction work through and immediately adjacent to environmentally sensitive areas and their buffers, unless otherwise required by a permit issued by a federal or state agency. • Work should be done in the dry season whenever possible (June 15 to September 15). • The width of the corridor through the wetland or stream should be minimized. • Construction staging areas must be located outside of environmentally sensitive areas and their buffers, unless determined by the Planning Director to be infeasible. Streams, wetlands, buffers, staging areas and construction limits shall be clearly shown on construction plans. Construction limits shall be clearly marked in the field with orange construction fencing. • Work shall be done so as to minimize turbidity, erosion, and other water quality impacts. • Proper erosion and sediment control measures shall be followed to prevent sediments from entering creeks or wetlands. Erosion control measures shall be approved by the Department of Engineering and Public Services and/or agencies with jurisdiction. Measures may include, but not be limited to, placing plywood across the area where equipment will operate; mulching the wetland areas where equipment will operate; placing wood chips atop a flexible mat to help prevent compaction (the wood chips and mat must be removed following construction); placing silt fences and hay bales between construction areas and all adjacent wetlands and streams; and placing ecology blocks between construction areas and streams or wetlands when a temporary fill is used for roads, etc. • Erosion control measures shall be in place and inspected prior to commencement of work. All erosion control structures shall be inspected regularly to ensure they are maintained in working order. • If the corridor needs to be dewatered to do the work, the water should be pumped to a sedimentation pond where all solids can settle or an area where it can sheet flow before being discharged back to the stream or wetland. Turbidity levels in associated wetlands and streams shall not exceed the standards in WAC 173-201A. • Any excavation materials must be placed in an upland area during construction. Wetland soils must be in separate piles from upland soils. After construction, wetland soils should be returned to the wetland and upland soils placed in upland areas. At a minimum, the top 18 inches of topsoils from wetland areas shall be stored separately from the rest of the soils and replaced as the top layer of fill in the wetlands following construction. Care must be taken not to make "dams" from compacted fill that would alter any subsurface flow. • If a pipe is being trenched through the area, measures shall be taken to prevent the de-watering of the wetland (e.g. cut off collars, etc.). 18