2007/04/18 Council Agenda Packet

1 April 6,2007 Page 3 • Data Gaps list;and • Drainage basin and pattern sketch map with locations for survey identified, if necessary. TASK 3. ANALYSIS Using existing data and observations made during the field reconnaissance,the Adolfson team will: Assess Existing Level of Protection Adolfson will estimate the level of protection provided by the existing levee system to the WPCF and to property within Diking District No.5 using existing LIDAR or other current topography information, and existing FEMA flood elevations. The level of protection study will be based solely on elevations shown in the LIDAR, and any additional survey provided by the City. The level of protection study will assume that the levees are properly constructed and that they provide two feet of freeboard. Assess Levee Stability A qualitative description of the stability and condition of the existing levees will be provided.This will be based on existing boring information,survey information and observations made during our site reconnaissance.No subsurface explorations are proposed as part of this study. Assess and Document Existing Drainage Reconnaissance-level mapping of existing drainage basins and patterns within the levees will be provided. Mapping and initial assessment will be based on existing LIDAR and as-built topography information,and observations made during the field reconnaissance. Spatial locations will be collected using a handheld GPS to be included in the maps generated for the report;these data points will not include elevations. We will also note areas where additional survey would be required to accurately depict drainage patterns(e.g.,culverts or inlet/outlet structures). One result of the documentation will be to identify access routes to the facilities that have the potential to flood during high tide/flow conditions. These areas would be identified for future detailed assessment Future assessment tools would include rainfall/runoff modeling. Develop a Levee System Map GIS generated maps of the diking and drainage system will be provided to the City. These maps will show: • Diking District No. 5 boundaries; • Existing levees; • Existing drainage basins and patterns; • Areas where the levee crest elevation is below the 10-year plus 2 feet elevation; • Areas that may already have 10-year plus 2-feet or better protection; • • Area above the flood elevations predicted by FEMA; • Access routes to the WPCF; • Levee sections qualitatively assessed to be in poor condition; 64 zi