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The Riverfront Development site includes more than 20 individual wetlands, which range from small
<br /> isolated depressions formed on fill soils to larger riparian wetlands that predate site development. The
<br /> wetlands are grouped into five associations or complexes:
<br /> • the North Wetland Complex includes wetlands east of the vacated railroad corridor and
<br /> north of the proposed residential Simpson Pad development;
<br /> • the West Wetland Complex includes wetlands east of the vacated railroad corridor and
<br /> active rail mainline, abutting the Simpson Pad;
<br /> • the South Wetland Complex includes wetlands south of the Simpson Pad, between the
<br /> railroad main line and the river;
<br /> • the East Wetland Complex includes wetlands east of the Simpson Pad between the
<br /> Simpson Pad and the river; and
<br /> • the railroad corridor wetlands, which include the highly-modified and channelized
<br /> wetlands between the active mainline and the northern extent of the Eclipse Mill site.
<br /> Many of the wetlands within the railroad corridor complex are associated with the current
<br /> Bigelow Creek or West Ditch Creek drainages.
<br /> Bigelow geek Drainage/South Wetland Complex
<br /> The master plan proposes returning Bigelow Creek to an alignment consistent with pre-development
<br /> drainage patterns. Baseflow and stormflows in the stream will be diverted from the existing system of
<br /> ditches abutting the BNSF mainline and will discharge to a newly-constructed channel that will bisect
<br /> the South Wetland Complex. The alignment of the new channel will approximate the alignment of an
<br /> existing gravel access road that connects the Simpson Pad to the BNSF right-of-way. Near the rival'the
<br /> new channel will join two small existing drainages that convey flows to the river from portions of the
<br /> South Wetland Complex. The existing drainages will be enhanced, and two existing culverts, one under
<br /> the gravel access road and the other under the Riverfront Trail, will be removed. The new Bigelow
<br /> Creek alignment will be a constructed as a low-gradient tidal channel due to the elevation at its
<br /> culverted discharge underneath the BNSF mainline. Most of the length of the newly-constructed stream
<br /> will be tidally influenced, and will provide the opportunity to restore tidal influence to the South Wetland
<br /> Complex. Restoration of Bigelow Creek will require excavation within and adjacent to wetlands in the
<br /> South Wetland Complex. Limited fill of adjacent wetlands will be required to hydrologically isolate the
<br /> restored wetlands from the existing non-tidal wetlands in the WSDOT parcel to the south, and from
<br /> Wetland D, which is largely overlaid by the Restrictive Covenant, located to the northwest. Wetland fill
<br /> will be offset by wetland and stream creation within the restored and enhanced South Wetland
<br /> Complex.
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<br /> Riverfroni Development Public Amenities Maser Plan 17
<br /> 54
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