CONCLUSIONS AND RECOMMENDATIONS <br />Conclusions <br />The field work conducted for the Geotechnical/Geologic Assessment of the Capital Hill PUD by <br />Branch Engineering does not satisfy the requirements of EC 9.6710 (5)(b) or (4)(c), in that it: <br />1.The subsurface exploration was conducted on 20% or less of the subdivision property. <br />2.The subsurface exploration did not extend into the areas most likely to be subject to slides. <br />3.The field work cannot be shown to have been conducted according to Standard Methods. <br />The report on the assessment and its addendum contain numerous errors, all of which make it appear <br />that the area is safer and more stable than it is in reality. <br />4.The addendum presents that the PUD will be constructed on “stable volcanic rock”, when, in <br />reality, the site is underlain by an east-dipping sedimentary rock assemblage. <br />5.The scale of the “Area Slope Hazard Map” makes nearby DOGAMI-mapped slides appear twice <br />as far from the PUD as they are in reality. <br />6.That same map indicates that lots 18 and 19 are located entirely within the “No Build Area”. <br />The subdivision plans indicate otherwise. <br />7.Independent mapping of the area using state-of-the-art LiDAR hillshade maps and on-site tree <br />evidence indicates that significant portions of the eastern part of the PUD have been and are <br />subject to landslides. <br />The PUD’s design also fails to satisfy the requirements of EC 9.8320 (6): <br />8. The design of the subdivision, with fills in the upper portion of the steep east-facing slope and <br />concentration of storm-water in the pore-pressure sensitive lower portions of the site combine <br />to both increase driving forces for slides at the top of the slope and decrease resisting forces at <br />the bottom. In a system alreadysubject to slope movements this will have a highly destabilizing <br />effect. <br />9. The level spreaders proposed to be employed to discharge the storm-water from the eastern <br />portion of the PUD aredesignedto dump 144 gallons per minute of water on a slope with a <br />gradient of 50%. This is the equivalent of about 29 garden hoses running full bore and will result <br />in mud and water running across the Ribbon Trail. From there, the waterwill run directly into <br />a landslide mapped by DOGAMI and then continue to several residences along Floral Hill Drive. <br />10.The professionals who prepared the Geotechnical/Geologic Assessment appear to either not <br />understand the local geologic system, or not to care, placing the interests of the developer ahead <br />of the people along portions of Floral Hill Drive in the Laurel Hill Valley who will be the <br />recipients of both the storm-water discharge and potentially resulting landslides of various forms. <br />10 <br />Capital Hill PUD Geotechnical Review, GeoScience, Inc. 3/7/18 <br /> <br />