1215 W MUKILTEO BLVD 2017-07-28 - Laserfiche WebLink

April 29,2015 HWA Project No. 2014-162-21 that no open spaces or voids larger than 6 inches exist. Rocks should be placed so that there is bearing between flat rock faces, rather than on points. Voids greater than 4 inches should be visibly examined and checked to determine if contact between rock courses exist. If there is no contact, then some resetting of the rock is required. Where voids greater than 6 inches in size are visible along the inside face of the rock facing, quarry spalls can be used to block the open spaces and, where necessary,to wedge between rocks and to lock them together. This should also serve to prevent washing of backfill material through the rockery. No rock less than 12 inches in least dimension shall be used to fully support a larger rock. Upon completion, there should be no loose rocks that could be dislodged by climbing or walking on the top of the rock facing. Construction Inspection We recommend an HWA geotechnical engineer, or their representative, be present during construction to verify that the rockeries are constructed per the recommendations presented in this report and outlined in the ARC guidelines. The depth and extent of foundation excavation will be directed by the geotechnical engineer on site. Construction Considerations Replacement of the existing rockeries will require the contractor to expose the native soils behind the existing wall. We expect this soil to consist of stiff to very stiff, Whidbey Formation soils with a thin layer of fill soils near the top of the wall. The stiffness nature of the Whidbey Formation soils is such that we do not expect significant caving during construction. However, there is potential that the near surface fill soils could ravel slightly when exposed. Long Term Inspection and Maintenance Rock facing is a protective system built from natural materials by builders with varying levels of experience and is not intended to act like a reinforced concrete wall or engineered retaining wall. We recommend that provision be made to conduct periodic inspection of the rock facing during its service life. Wet Weather Earthwork Existing site soils are moisture sensitive and will be to be difficult to handle or traverse with construction equipment during periods of wet weather. General recommendations relative to earthwork performed in wet weather or in wet conditions are presented below. These recommendations should be required when earthwork is performed in wet conditions: 2014-162 Letter Report 8 HWA GEOSCIENCES INC.