2010/03/31 Council Agenda Packet

rl excavation, and avoids excavation entirely within the Restrictive Covenant area. Enhancements will include the creation of wetland hummocks and upland islands , :° y 4 G t 1using imported topsoil and/or organic soil amendments, Q5"`_,:. .---1 . -,�.t '~- areas which will be planted with scrub-shrub or forested f.. ' e wetland vegetation to increase complexity and habitat ,� ,,'` ', i'4 r diversity within emergent wetland areas. These new West - ,,itVA i,I l ,a ' - Wetland Complex hummocks will be augmented with E, _ ..L ' surface-installed large woody debris and brush piles to _2 ,_ . " -. 3 provide added habitat value. Railroad conidor wetlands. Railroad Corridor Wetlands The restoration of the Bigelow Creek and Walton Creek drainages will divert much of the surface water inflow in the railroad corridor north of the Snohomish County Public Utility District transmission line crossing. Because these channelized wetlands have elevations lower than the high tide of the Snohomish River, the wetlands are anticipated to retain sufficient hydrology. Most of the existing ditched wetlands are proposed for filling to construct trails, access roads, and other amenities within the railroad corridor. The functions of the impacted wetlands will be replaced through the creation of new wetlands and the enhancement of remaining wetlands within the corridor. This area of the Riverfront Development site will also provide mitigation sites for impacts to other railroad corridor wetlands affected by other (both city and private developer) projects, including impacts to a small wetland area on the 3-Acre Park site and filling of the ditched wetlands along the proposed Eclipse Mill Road corridor. The majority of wetland creation and enhancement will occur north of the PUD transmission line crossing, east of the proposed multi-use Railroad Corridor Trail, and west of the developer's Wetland C buffer enhancement and off-channel habitat pond. The private developer's buffer and wetland/habitat mitigation areas are planned as mitigation for its development-related impacts, and are not part of this Public Amenities Master Plan. This work will, however, be coordinated with the master plan efforts to maximize the restoration and enhancement opportunities within the corridor. PROPOSED CONDITION ?WETLAND C I 60' �/ 50' p 35' 20_ 30' LANDFILL J Q�t FER • WETLAND O.M.BUFFER 1TRAIL&-f O.M.BUFFER • �., SHOULDER r I r �1 WETLAND C DOUBLE WETLAND V SINGLE WETLAND W GRAVEL LANDFILL RR TRACK RR TRACK SURFACE ROAD EXISTING CONDITION Cross-section through railroad corridor: Riverfront Development Public Amenities Master Plan 21 58