SCARPS MAPPED ON PUD BY APPLICANT’S ENGINEERING GEOLOGIST <br />Whereas the Staff report may be correct that no landslides are shown mapped on SLIDO on the <br />proposed PUD itself, the blanket statement that no landslides were mapped there is patently false. <br />The applicant’s own Engineering Geologist mapped two “scarps” within the PUD in what is now <br />Lot 16, with one located in the vicinity of the proposed driveway and one a little farther downslope. <br />“Scarps” are the steep slope segments that form the upper boundary of a moving landslide block as <br />the sliding block drops and slides downslope. The presence of this landslide feature is <br />th <br />acknowledged by the applicant’s own geotechnical consultant in the 5/30/2017 Addendum (p.1, 5 <br />paragraph): <br />“One location in the southeast portion of the site was mapped as the upper section of a <br />landslide area; subsequent site design omitted development in this area”. <br />Whereas GeoScience agrees with the first part of this statement, the second part is incorrect. The <br />current PUD design indicates that grading for the driveway for Lots 16 and 17 will occur directly on <br />top of the upper scarp with the likely building area for Lot 16 located below the driveway. <br />Therefore, the apparent building area for this lot will be located on top of a landslide the presence <br />of which is acknowledged by the applicant’s geotechnical professional. No subsurface exploration <br />was conducted in this area to define the problem (further discussion in “Inadequate and Biased <br />Assessment Area”, below). <br />SLOPE MOVEMENT FEATURES MAPPED BY GEOSCIENCE <br />Given that DOGAMI’s update of the slope movement mapping in the area is not yet complete and, <br />given our familiarity with the immediate area, GeoScience determined that it would be beneficial <br />to conduct our own geomorphic mapping of probable slope movement features in the area. The <br />figures on the following pages illustrate the results. Based on the geomorphology alone, it is quite <br />clear that significant slope movements have occurred on the east-facing slope of the ridge in the <br />recent geologic past. The outlines of these movements are shown in yellow. Scarps delineating the <br />head of slides areshown with short lines attached on the downslope side of the outline of the <br />movement. Areas with arrows indicate movement directions of the resulting landslide deposits. In <br />most cases in the Eugene-Springfield area, slope movements initially consisting of sliding blocks, <br />which tend to disintegrate with movementand turn into “earthflows”. These then form lobate <br />landforms at the base of the slope which move downhill by soil creep and localized much more rapid <br />movements of several feet to tens of feet within days. <br />Such lobate forms are clearly discernible at the base of the steep east-facing slope of the ridge on <br />which the PUD is proposed to be constructed. In the vicinity of Floral Hill Drive, the lobes exhibit <br />uneven “hummocky” topography typical of landslide deposits. Moreover, in areas of the most recent <br />and rapid movement, larger coniferous trees are absent, allowing for significant brush to cover the <br />deposit, which causes minor problems with the LiDAR mapping. These areas are identifiable on the <br />3 <br />Capital Hill PUD Geotechnical Review, GeoScience, Inc. 3/7/18 <br /> <br />