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Report in Support of the Recertification of the University of Colorado 's Flood Control Levee Page 15 X. GEOTECHNICAL EVALUATIONS X.1. Stability, Seepage and Settling CTL /Thompson's earlier geotechnical evaluation of the Levee was conducted in 1997. Its analyses and findings are included in the September 28, 1998 report, "Levee at Deepe Farm Pit, Boulder, Colorado" (see Appendix B -9). In the summary, CTL /Thompson concluded: "1. Results of geotechnical investigation indicate the levee meets (satisfies) FEMA criteria for slope stability and piping through or under the levee." "4. ... Given the compactness of the levee and the dense soils there should be no noticable change in freeboard." "5. Inspection of the levee and the results of this study show the levee meets the geotechnically related FEMA criteria." 2 X.2. Removal of Vegetation After the Levee was constructed, trees and other vegetation grew on its outside face. Since FEMA does not allow trees and vegetation on the face of any Levee which is to be recognized, the trees and brush were removed from the upstream reach of Levee during September 1997. CTL /Thompson was present to observe removal of trees and other vegetation from the Levee, including removal of roots and re- compaction of the disturbed area. See Appendix B -9. Since then, the University has been diligent in removing any vegetation that starts to grow on the upstream reach of Levee. X.3. Raising of Embankment CTL /Thompson provided testing and observation during the raising of the Levee in 1997, 1998 (see Appendix B -9) and 2008, and testing for the raising of the Levee in 2009 (see Appendices B -9 and E). X.4. Evaluation of Seeps The area behind (on the land side of) the Levee was once a gravel pit. The Levee was constructed on top of the natural ground at the top of the excavation prior to the excavation of the pit. There are a number of seeps which exist on the face and toe of the slope that forms the sides of the former gravel pit. They are located relative to the Levee in Appendix C of the CTL /Thompson report which is now contained in Appendix B -9. They are also visible on the aerial photographs of the site, Figures 7, 9, & 11. The seeps exist because the gravel -pit excavation intercepted the naturally occurring ground -water table. In addition, some of the seepage is from leakage out of Dry Creek Ditch Number 2, which runs along the creek -side toe of slope of the Levee for approximately 4,100 feet. Seeps have been present on the inside face 2 Ibid, pages 1 and 2 (Appendix B -9). 3 Ibid, Figures C -1 through C -4 of CTL /Thompson's Appendix C (included here as Appendix B -9) © Leonard Rice Engineers, Inc. June 2009 — 207FIP05