ARCHIVED REPORTS 2011 YEAR 5 PHYTOREMEDIATION TREE MONITORING REPORT

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1 ' SECTION 5 Year 5 Success Criterion Evaluation and Recommendations This section provides a summary of the results of the Year 5 tree and irrigation system monitoring and the Year 5 success criterion evaluation. ' 5.1 Attainment of 5-Year Success Criterion As described in the Phytoremediation Cleanup Plan (CH2M HILL, 2004) and summarized in ' Section 3, the 5-year success criterion for the tree phytoremediation system is an average tree survivorship rate of 80 percent or greater(average for all six planting sub areas). Once the 5-year success criterion was to have been attained, site monitoring and annual reporting of the plant system would cease. The average tree survivorship success criterion of 80 percent(average for all six sub areas) was exceeded in all monitoring years. In Year 5 (2011),the overall survivorship rate was 91 percent. In Year 4 (2010),the average survivorship rate was 93 percent (Table 4-1 and Appendix A). The average Year 3 survivorship rate was 91 percent. The average Year 2 ' (2008) survivorship rate was 89.6 percent(rounded in Table 4-1 to 90 percent).This was essentially the same survivorship rate as observed in Year 1 (2007),which was 89.5 percent. 5.2 Recommendations Because the 5-year 80 percent survivorship success criterion has been attained, the annual tree survivorship monitoring and annual reporting component of this project will cease. The trees in Areas A, Addition to A,Area AA, and Area B are well-established and no longer need supplemental irrigation. Irrigation was last applied to these trees in 2009. As ' shown in the photographs in Appendix B,the trees in these planting sub areas continue to grow vigorously and have a dense canopy that provides substantial wildlife habitat benefits. However, the trees in Areas C and D have probably not become naturally established (with roots that reach the groundwater) and will need supplemental irrigation to maintain their continued growth and survival. Therefore,limited irrigation will be applied to the trees in Areas C and D in 2012. Weeds throughout the site, including the areas adjacent to Whiskey Slough Road,will be controlled by the native restoration contractor concurrent with the ' irrigation site visits. Phytoremediation system checks will be performed in 2012 to document the survivorship in Areas C and D and site irrigation and maintenance actions will be performed. A memorandum will be prepared that summarizes these activities and it ' will be submitted to the RWQCB by December 31,2012. ' SAC14203071113570001(YEAR5-2011 HOLTTREE_MONITORING REPORT-FINAL.DOCX) 5-1