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Page 3 C. Upstream channel Flow does currently exist through the rock undrain of the embankment fill at an estimated rate of 50 to 100 g.p.m. The flow meanders through a small sediment delta at the bottom of the impoundment into the rock underdrain. Debris lines along the North slope of the upstream channel indicate vary- ing stages of impoundment immediately after a storm. The impounded water level was well below the steel stake set to indicate the 10-year, 24- hour storage level. The highest 24-hour precipi- tation for 1985 was 1.77 inches on April 18, 1985. This is higher than the 10-year, 24-hour event of 1.6 inches. Several reasons may explain why the 10-year, 24-hour storage elevation did not appear to be exceeded: 1. The original storage estimate was based on worst case with no seepage through the rock underdrain; whereas, the rock underdrain still appears to allow seepage from the im- pounding area. 2. The original 10-year, 24-hour storage esti- mate may have been based on the use of con- servative methods and/or data; thus, predict- ing higher runoff. 3. The rainfall may not have been directly centered over the immediate watershed. A copy of the annual precipitation data covering 1985 is attached. D. ~wnstream embankment slope Vegetation appears somewhat thicker on this slope than on the upstream slope. Erosion does not appear to be a problem due to the relatively short slope and limited area exposed to runoff. The only significant runoff from the haul road ditches occurs in a controlled downdrain on the North abutment of the embankment to the "Tie Access Road" culvert. No cracking, bulging, or other signs of stress were noted. III. Results There appears to have been no noticeable change in the embankment structure since the last annual inspection of August 1, 1985. Vegetation is growing on the side slopes.