Kansas Levee Certifications Assessments, Findings and Challenges. APWA Congress Denver, Co - Sept 18, 2011

Transcription

1 Kansas Levee Certifications Assessments, Findings and Challenges APWA Congress Denver, Co - Sept 18, 2011

2 Introductions Presenters Doug Danaher, PE, CFM Wilson and Company Joe File, PE, CFM AMEC Brian Clennan, PE City of Hutchinson Kansas Municipal Levee Owners Consortium Augusta, Dodge City, El Dorado, Florence, Gypsum, Hutchinson, Manhattan, Marion, Osawatomie, Ottawa, Salina, Topeka, Wichita

3 Presentation Outline Background & Importance of Certification Assessment Process Findings Challenges of Certification (Time and Funding)

4 Background History NFIP Program CFR Map Modernization 2003 Provisionally Accredited Levee Agreements 2007 Risk Map 2010

5 Background If the levee is certified by a professional engineer as meeting the criteria in 44 CFR 65.10: The levee is accredited and mapped. Area behind the levee is mapped as moderate risk (zone X). If the levee does not meet criteria: Levee shown on effective maps is de-accredited. Area behind the levee is mapped as high risk (zone AE or A). Flood Insurance policies will be required for properties with federally backed or insured mortgages. 5

6 Background Certification Impacts

7 Background FEMA Levee Certification Program Consultant Certifies FEMA Accredits Process is for Flood Insurance Purposes COE Programs (Other Purposes)

8 Background Those Impacted by Certification: Mayor Jones Mr. Jones Councilman s Brother Senators Mom Floodplain Manager FEMA Employee Retired General Your Son s Kindergarten Teacher Public Works Director Your Wife s Best Friend Your Mother-in-Law

9 Assessment Process Freeboard Closures Seepage and Stability Settlement Embankment Protection Interior Drainage Analysis Operation & Maintenance Manual As Built As Is

10 Assessment Process Phase I Discovery Phase Phase II Analysis Phase Phase III Construction & Certification

11 Assessment Process Freeboard Requires 3 throughout; 3.5 at upstream end; 4 at constrictions (bridges) Updated river hydrology; river hydraulic model / water surface profiles Survey current top of levee profiles Compare profiles & identify deficiencies

12 Assessment Process Closures Requires closures for all openings that are structural parts of the system, designed according to sound engineering practices. Road / rail closures (sandbag, stop log, gates, etc.) Conduits (gated and un-gated) Considers river timing

13 Assessment Process Seepage, Stability and Settlement Requires Engineering analysis to evaluate seepage during loading conditions and demonstrate that seepage into or through the foundation and embankment will not jeopardize stability. Engineering analysis to assess future settlement and demonstrate freeboard will be maintained. Geotechnical science evolved in 1970 s Borings to characterize soils Analyze for seepage, stability and settlement Validate with historical performance and top of levee profile Considers river timing

14 Assessment Process Embankment Protection Requires Engineering analysis that demonstrates no appreciable erosion can be expected, and that expected erosion will not result in failure of levee. Considers flow depths and velocities from updated river modeling Validated with historical performance (review historical photos)

15 Assessment Process Interior Drainage Analysis Requires analysis to identify flooding sources and the extent of the area flooded and if the avg depth > 1, determine water surface elevations. Based on joint probability and capacity of interior drainage facilities. Updated hydrology Utilize USACE coincidental peak analysis method Utilize updated ground surface elevation data (2-ft contours) Complete reservoir routing to minimize ponding surface areas Likely to be Zone A on updated FEMA maps

16 Assessment Process Operation & Maintenance Manual Requires Operation & maintenance per current manual, under jurisdiction of federal, state or community in NFIP. Requires flood warning system; plan of operation; periodic operation of closures; backup provisions. Update USACE O & M manual; develop detailed operation plan

17 Assessment Process As-Built (As-Is) Drawings Requires certified as-built plans of the levee system. Update As-Builts to Reflect Current Conditions Can Use Current Ground Surface, Aerials, Profiles, BFE s, Soil Borings, GIS Data, Utilities, etc.

18 Findings Systems Generally Well Maintained Review Original Agreement & O & M Manual Reporting Requirements, Access Control, Modifications (USACE Approval and update documents), Detailed Operation Plan, Practice Operation, Video Inspection of Conduits

19 Findings Wichita Valley Center Flood Control System Constructed from 1950 through miles earthen levee embankment 4 diversion structure 14 floodwalls 6 pump stations 120 interior drainage structures 96 ponding areas 11 miles training levees

20 Findings Developed Phased Assessment Approach Phase 1 LiDar Historical Documentation Visual Assessment Phase 2 - Certification Analysis (COE completed part of hydrology) Phase 3 Design and Construction

21 Findings Worst First Approach Four Projects Identified Plans & Specs parallel to analysis Additional Construction Projects

22 Findings City of Manhattan Levee Project Five Mile Levee System Two Closures Two Pump Stations 19 Drainage Structures

23 Findings Required Levee Modifications Additional freeboard for one mile of levee (BFE s went up) Decommission two interior drainage structures

24 Shaded Relief Map Hutchinson S. Hutchinson

25 Hutchinson 1929 Flood

26 Hutchinson Levees Levee F: Protects Willowbrook Levees A, D, E Protect Hutch Levee C: Protects Reno Co. Levee B: Protects S. Hutch

27 Hutchinson: 2011 vs 2007

28 Hutchinson: 2011 vs 2007

29 Hutchinson: 2011 vs 2007

30 Floodplain w/o Levees Hutchinson S. Hutch

31 Floodplain w/ Levees Hutchinson S. Hutch

32 Findings Hutchinson Levee System Lacks freeboard in a few areas Additional underseepage control needed Update operation & maintenance manual; develop detailed operation plan

33 Findings Hutchinson Levee System, Cont. Corroded conduits Additional embankment protection needed Large interior drainage areas, potential pump station

34 Findings Dodge City Levee System Insufficient freeboard due to sedimentation in river channel Operation challenges for sandbag closures 8 closures require 135 people (8 hrs), 22k bags, 200 cu yd sand, 8 trucks Embankment protection improvement & alternative analysis Update operation & maintenance manual; develop detailed operation plan

35 Certification Challenges Each System Differs Hydrology Hydraulics Geography Geology Definition of System Lack of Time Lack of Funding

36 Certification Challenges Kansas Municipal Levee Owners Consortium Augusta, Dodge City, El Dorado, Florence, Gypsum, Hutchinson, Manhattan, Marion, Osawatomie, Ottawa, Salina, Topeka, Wichita 13 Municipalities Throughout Kansas Populations range from 400 to 400,000 Primary Functions Include: Unified Voice to Rule Makers (Federal and State) Share Lessons Learned