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Eugene Planning Commission May 2, 2018 Page 9 The last recommendation, regarding fill- and cut-slopes, is most problematic. - Rather than decrease the risk of slope failure; the recommendation for installing fill slopes at angles up to 1.5H : 1V is likely to increase the risk of slope failure. In general, installing fill slopes at angles steeper than 2H : IV is reserved for fills constructed of material with high angle of internal friction such as rock. In this case, it is being made for fills constructed of "compacted earth". Moreover, the fill slope typical drawing contains provisions for a sub-drain only on the lowermost key-way. On this slope, underlain in part by rock, this may allow buildup of excess pore pressure higher in the fill section, resulting in reduced effective stress at the base of the fill and an increased potential for failure of the embankment. As a result, the applicant's report does not contain "numerous specific recommendations to mize the potential for slope failure" and one of their recommendations appears to actually increase the potential by allowing overly steep fill slopes with inadequate drainage. It is difficult to determine where the HO received the impression that the issue was addressed in the application materials. 2.c. "Soil Creep" Branch Engineering ascribes the tree deformation noted on the steep eastern slopes of the site entirely to "soil creep"." 6 The HO twice seizes upon this statement in her findings. However, whereas "soil creep" is clearly occurring on the steeper slopes of the PUD property (as acknowledged by GeoScience in our March 7, 2018 report), the tree deformation found in several portions of the site is not consistent with having been caused by soil creep alone. As discussed by GeoScience", deformation by soil creep always tilts the base of the trunk in a downslope direction, due to the direction and mechanics of the soil movement. However, on this site, and especially in the areas where there are geomorphic indications of sliding failure, the deformation of the tree trunks is haphazard, with many tree trunk bent in different directions at different levels, in some cases in an upslope direction (see also GeoScience site photos"). This is consistent with back-rotation of the tree during rotational sliding movement and cannot have been caused by soil creep. The HO erred in accepting Branch Engineering's explanation of the tree deformation on the site. 16 Branch Engineering Rebuttal, 3/20/18 p.2, last paragraph. 17GeoScience Technical Review, Geotechnical/Geologic Assessment and Addendum Capital Hill PUD, March 7, p 4, 2' paragraph and following. 18GeoScience Technical Review, Geotechnical/Geologic Assessment and Addendum Capital Hill PUD, March 7, attached site photos and GeoScience PowerPoint presentation.