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<br />Taranto Stanton & Tagge <br />Page 2 <br />July", 1980 <br /> <br />Slopes along the majority of the ditch are steep, estimated 1:1, with <br />some portions probably approaching 1/2:1, Typically at waterline the <br />slopes are near vertical becoming less steep below the waterline, Near <br />vertical slopes exist along portions of the alignment and are typically <br />more pronounced on the outside of horizontal curves in the ditch, The <br />very steep slopes have resulted 'from erosion at the toe and saturation <br />and sloughing of the slopes with time. The most pronounced sloughing of <br />the slopes was observed around the lake in the northwest 1/4 of Section <br />3, Township 3 North, Range 68 West, The depth to the waterline in the <br />ditch in the area of the lake is estimated to be approximately fifteen <br />(15) feet with bedrock observedioutcropping approximately six (6) feet <br />below the surface, It is our opinion that observed banks stability <br />problems have been directly cau$ed by erosion and undermining of the <br />slopes, Erosion of the toe of slopes and bank sloughing will continue <br />if adequate means to retard the erosion are not provided, <br /> <br />Many trees exist along the ditch typically being more pronounced west of <br />County Road 13, Tree roots and,fe1led trees have in part created a <br />nonuniform channel cross-section with erosion much more pronounced in <br />the immediate area of the trees; It is our opinion that all trees on <br />the ditch banks interfering with flow should be removed, <br /> <br />Growth adjacent to ditch sections in fill indicate horizontal seepage <br />does not appear to be severe, Seepage was observed along a small <br />section of the ditch immediately adjacent to the Davis Reservoir, Lush <br />grass growth on the north side of the ditch east of the Great Western <br />Railroad tracks (southeast 1/4 Of Section 30, Township 4 North, Range 67 <br />West) may indicate some seepage: in this area, At this time, we have no <br />indication of vertical seepage from the ditch, Soil Conservation Ser- <br />vice maps indicate permeabi1ity'rates of the majority of the soils along <br />the ditch are moderate to slow., Only the Otero Sandy Lome which occurs <br />along the east end of the alignment has rapid permeability rates, We <br />suggest that additional geotechnical field and laboratory work be <br />performed to evaluate the permeability of soils along the alignment, If <br />permeability tests indicate that seepage losses are high, then con- <br />sideration should be given to cQmpaction of the soils on the bottom and <br />sides of the ditch and/or lining the ditch, <br /> <br />In summary, we would like to make the following observations; <br /> <br />(1) Remedial work is required at all structures to minimize <br />erosion, Hydraulic design of the structures and reshaping and <br />riprapping of the slopes are required, <br /> <br />