Hearings Official Decision - Laserfiche WebLink

As noted above, the Response Committee presented its own Geotechnical assessment, which disputes nearly every finding of the applicant's report. As it relates to slope stability, the GeoSciences analysis relies on Dr. Schlieder's interpretation of LIDAR data and extensive discussion to suggest that the subject property may be geologically unstable. Following his initial investigation, Dr. Schlieder provided an addendum to support his interpretation, based on the presence of `lobes' in the pavement of Floral Hill Drive, located "at or near the toe of the east- facing slope below the proposed PUD." (Addendum to Geotechnical Review of Capital Hill PUD, March 21, 2018.) The Response Committee's forester, James Mehrwein, also disagrees with the applicant's analysis regarding the potential for slope failure. He concludes that "there is current evidence in the project area of slope instability. After viewing the site and reviewing published studies regarding tree removal and slope instability, it is my opinion that the proposed plan to harvest the trees designated for removal would increase the likelihood of slope failure in the future." He further explains that type of slope instability he observed would be considered "soil creep." The applicant's geotechnical engineer responded to Mr. Mehrwein's assertion that the property may be subject to soil creep as follows: "Soil creep is the downhill movement of near surface soil (usually the upper 2- to 3-feet) due to gravity, freeze/thaw, and shrink/swell effects. The slow creep may cause a pistol- butting of tree trunks during their early growth phase until substantial root mass and trunk strength is developed. Creep is common on most hillsides and does not indicate gross landslide movement. Creep movement is generally mitigated by modern foundation systems and control of soil moisture and temperature under and around the residence to where the slow movement is unnoticeable over the typical lifespan of a residence." (Branch Engineering Geotechnical/Geological Investigation Rebuttal, March 20, 2018.) The applicant's geotechnical engineer responded to the GeoSciences assessment by reiterating the finding in the applicant's analysis that "[t]here are areas of gross land instability on the east side and those were field mapped to the best of our ability for the planning level report. Mr. Schlieder's interpretation of the LIDAR is simply that, an interpretation with no ground reconnaissance of the site. The supposed landslide features that appear to encroach onto the northeast portion of the site are just as likely to be erosional in nature if they exist at all." To respond to Dr. Schlieder's analysis related to Floral Hill Drive, the applicant's engineer provides a detailed factual analysis to support its conclusion that there is no indication of landslide movement in that area. Neither the GeoSciences assessment nor the forester's assessment consider or respond to the numerous, specific recommendations in the applicant's geotechnical investigation to minimize the potential for slope failure. The standards for Geological and Geotechnical Analysis at EC 9.6710 are discussed in further detail below. However, as those standards relate to the issue of slope stability, Public Works referral comments (page 7-8) agree with the applicant's analysis and conclusions in the report. In Hearings Official Decision (PDT 17-1) 52