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Ms. Susan Morrison <br />June 2, 1992 <br />Page 5 <br />C. Upstream Channel <br />Flow does currently exist through the <br />rock underdrain of the embankment fill at <br />an estimated rate of 5 to 10 gpm. The <br />flow meanders through a small sediment <br />delta, upstream from the toe of the <br />embankment, into the rock underdrain. <br />The rock underdrain appeared to be <br />functioning properly with no evidence of <br />water backing up in the rocks from the <br />current flow. <br />The highest 24-hour precipitation for the <br />1991 Water Year was 1.12 inches of snow <br />on October 7, 1990. This is lower than <br />the 10-year, 24-hour evert of 1.6 inches. <br />A copy of annual precipitation data <br />covering the 1991 Water Year is attached. <br />D. Downstream Embankment Slope <br />Vegetation is sparse on the side slopes <br />due to the coarse and rocky material <br />present in the fill. Erosion does not <br />appear to be a problem due to the <br />relatively short slope and limited area <br />exposed to runoff. No runoff from the <br />haul road ditches occur down the <br />embankment slope. No cracking, bulging, <br />or other signs of stress were noted. <br />III. Conclusion <br />There appears to have been no noticeable <br />change in the embankment structure since <br />the last annual inspection of May 8, <br />1991. Vegetation is growing on the side <br />slopes. The embankment is stable and the <br />underlying rock fill is functioning as <br />expected. <br />