2009/10/21 Council Agenda Packet

2 Attachment 1 City of Everett Public Works Department Smith Island/Union Slough Restoration Project Alternatives Analysis for Adaptive Management of Site Hydraulics and Public Access Scope of Work The City of Everett Public Works Department(EPWD)has requested ICF Jones&Stokes to conduct an alternatives analysis,including costs,for assessing a long-term fix to the hydraulic and structural issues at the bridges and Union Slough dike compared to trail rerouting/abandonment of the Union Slough dike and associated trail and bridges at the EPWD mitigation site.The EPWD mitigation site is located east of the EPWD water pollution control facility(WPCF)on Smith Island. This scope of work identifies the tasks to be completed as part of the analysis. This scope assumes two options for addressing the drainage and scour problems at the Smith Island mitigation site: • Long-term repair of existing trail and bridges: includes the repair of the splitting that has been observed at the north end of the Union Slough dike by filling the backside of the dike within the mitigation area; paving the multi-purpose trail along the top of the dike from 4th Street to the north cross over dike,including long-term maintenance of the paved trail;creating an appropriate sill elevation at the three dike breaches to drain the mitigation site and restore a tidal regime that mirrors Union Slough,as described in the 2002 mitigation plan;fixing or replacing the three bridges in such a manneras to restore a tidal regime in the site that mirrors that of Union Slough(i.e.enables the mitigation site to drain at low tide)and resolve current scour problems;associated environmental permitting; and mitigation planning costs and implications for mitigation site credits associated with these actions. • Trail rerouting and abandonment of existing trail and bridges: includes abandoning the existing multipurpose trail on the Union Slough dike and rerouting a paved trail along the newly constructed western setback levee,including long-term maintenance of the trail;installing a fence along the rerouted trail to isolate trail use from the WPCF; removing and salvaging or demolishing the three bridges at the three Union Slough dike breaches(whichever seems most feasible);creating an appropriate sill elevation at the three dike breaches to drain the mitigation site and restore a tidal regime that mirrors Union Slough,as described in the 2002 mitigation plan;associated environmental permitting;and mitigation planning costs and implications for mitigation site credits associated with these actions. Alternatives Analysis Scope, October 6,2009 6 Page 1