EC 9.6710 Geological and Geotechnical Analysis. <br />(1) Purpose of Geological and Geotechnical Analyses: <br /> is to ensure that public and private <br />facilities in developments in areas of known or potential unstable soil conditions are located, <br />designed, and constructed in a manner that provides for public health, safety, and welfare. <br />and <br />EC 9.8320 (6) Tentative Planned Unit Development Approval Criteria - General <br />(6) The PUD will not be a significant risk to public health and safety, including but <br />not limited to soil erosion, slope failure, stormwater or flood hazard, or an <br />impediment to emergency response. <br />SLOPE MOVEMENT FEATURES MAPPED BY DOGAMI IN VICINITY OF PUD <br />DOGAMI (Department of Geology and Mineral Industries) has mapped numerous apparent landslide <br />features in the vicinity of the proposed Capital Hill PUD. This mapping is based partlyon <br />geomorphic expression of slope movements in the area and partlyon field-verified reports of <br />landslides which have occurred during the presence of white people in the area. The SLIDO <br />(Statewide Landslide Inventoryand Database for Oregon) map can be accessed online at <br />www.oregongeology.org/sub/slido/index.htm. DOGAMIis in the process of updating this mapping <br />using newlyavailable LiDAR technology, which provides significantly better topographic <br />information than was available with conventional topographic maps, however this update process <br />has not yet been completed. <br />The figure on the following page shows the larger vicinityof the Capital Hill PUD, from the area <br />th <br />of 30 Avenue in the south to nearly the bridge of I-5 over the Willamette River in the north. The <br />base map was generated by GeoScience from a LiDAR DEM (Digital elevation Model) available <br />from DOGAMI. The “hillshade map” was created through QGIS, a GIS program. The calculation <br />of the shaded relief map was performed with the “virtual sun” located at an azimuth of 190 degrees <br />(SSW) and 30 degrees up from horizontal. These angles were chosen to enhance geomorphic <br />features on the steep east-facingslope of the ridge, which are in dark shadows if the conventional <br />virtual illumination from the NW is utilized. The PUD is shown in dark pink. The following page <br />includes the outlines of landslides mapped by DOGAMI. <br />Whereas it is correct that the SLIDO map does not include landslides within the PUD itself, it does <br />include two larger slope movements below the southeast portion and northeast corner of the <br />proposed PUD, which are located less than 100' and 200' from the boundary of the PUD, <br />respectively. Two smaller slides are indicated on SLIDO to be less than 150' from the PUD. <br />It is interesting to note that the overwhelming number of landslides mapped in this area on SLIDO <br />are located on east-facing slopes. The explanation for this phenomenon is provided in the section <br />on “Dip-Slope Failure” below. <br />2 <br />Capital Hill PUD Geotechnical Review, GeoScience, Inc. 3/7/18 <br /> <br />