13 - Laserfiche WebLink

BACKGROUND Included in the City's Capital Improvement Program are four projects related to improving the Bernal Avenue and Vineyard Avenue traffic movements. The four projects have been combined into one project as a way of improving project and construction efficiencies. One of these four projects is the construction of a second bridge on Bernal Avenue over the Arroyo del Valle adjacent to the existing bridge. Project completion was originally anticipated to occur in 2003, but final design and construction was postponed in order to identify suitable wetland and riparian mitigation areas, as required by the Army Corps of Engineers, Department of Fish and Game, and the Regional Water Quality Control Board. All necessary regulatory agency permits have now been obtained and on-site and off-site mitigation areas identified. DISCUSSION Off-site Mitigation Area The proposed off-site mitigation area on the Bernal Property would meet the Bernal Avenue Bridge project requirements for riparian habitat as well as wetland habitat. Staff believes the use of the Bernal Property for wetland and riparian mitigation is compatible with the Bernal Property Specific Plan, which designates this area as agricultural. Per the Specific Plan, agricultural uses were anticipated to provide "hands-on" lessons in the natural sciences and ecology and to provide for a living classroom experience (see Attachment 2, pages 1-6 and Attachment 4). The created wetland and riparian habitat will foster these learning activities as stated in the Specific Plan. Access to the site for a more intensive use is problematic. The site is bordered by the Valley Avenue underpass, the Union Pacific Railroad, and the Bernal Creek. The use of this site for a wetland fits in well with this site's access constraints. The proposed mitigation site at the Bernal Property (Attachment 3) will create approximately 1.08 acres of wetland and 1.60 acres of riparian habitat, and will create an excess of .85 acres of wetland and .60 acres of riparian habitat over what was required by the environmental permitting agencies that can be used for future City project requiring similar mitigation measures or sold to other agencies as mitigation credits. In general, these mitigation areas will be constructed with a range of features including the planting of native trees and shrubs, wetland areas, and ponds. Trees to be planted include Coast Live Oak, Western Sycamore, Fremont Cottonwood, Valley Oak, Sandbar Willow, Yellow Willow and Red Willow. Shrubs and vines include Coyote Brush, Mulefat, Toyon, California Rose, and California Blackberry. Reseeding of any disturbed areas with native seed mixes will occur to facilitate growth of a native herbaceous under story. The mitigation area at the Bernal Property will primarily be fed by natural flows from Mission Creek and augmented with storm flows from the Valley Avenue Pump Station. In order to direct flows from Mission Creek into the created wetlands, modifications to the existing concrete outlet structure will be required. A temporary irrigation system will also be installed and be used to ensure healthy plant and tree growth during the plant establishment period (5 years). Page 2 of 3