7214 LARIMER RD 2016-08-08 - Laserfiche WebLink

GeoTest Services, Inc. October 11,2011 7214 Larimer Road, Everett,WA Job No. 11-0493 Topography at the top of the cut slopes upward to the west at an inclination of between 10 and 20 degrees. The slope is heavily vegetated with brush, groundcover and deciduous trees. No obvious signs of instability, significant soil creep, excessive erosion or other indications of landslide or erosion hazards were observed within the vicinity of the project site at the time of our field investigation CONCLUSIONS AND RECOMMENDATIONS Based upon evaluation of the data collected during this investigation, it is our opinion that the proposed construction is feasible and should not decrease slope stability, increase erosion potential, or increase risk to life or property provided the recommendations contained herein are incorporated into the project. The dense, Advanced Continental Glacial Outwash comprising the slope on the subject property is classified as Type A soils per WAC 296-155-66403 and as such, may be benched to a maximum of 3/4H: 1V. The current plans to bench the hillside to a maximum of 1H: 1V appears appropriate in our opinion, based upon our limited, visual site evaluation. Erosion Control All areas disturbed by construction practices should be vegetated or otherwise protected to limit the potential for erosion as soon as practical during and after construction. Areas requiring immediate protection from the effects of erosion should be covered with either plastic, mulch or erosion control netting/blankets. Areas requiring permanent stabilization should be seeded with an approved grass seed mixture, or hydroseeded with an approved seed-mulch-fertilizer mixture. We recommend that appropriate silt fencing be incorporated into the construction plan for erosion control (if applicable). Proposed Retaining Wall We understand that both modular block and railroad tie landscape retaining walls will be constructed in the vicinity of the new parking area. The walls will be less than 3 feet in height and will be gravity walls that support existing soil. Based upon discussions with the home owner, in our opinion, both walls are appropriate for use at the subject property if standard construction techniques are implemented in their construction. • Drainage is essential for proper performance of a gravity retaining wall. The retaining wall design assumes drained conditions and does not allow for hydrostatic pressure buildup within the gravity retaining wall. • The drainage layer should consist of free draining material with no fines, such as 3/4 inch clear crushed rock. The base of the drainage layer should be at least 12 inches in thickness. A minimum 0.5H:1V slope should be maintained between the drainage layer and any compacted fill. The drainage material should be compacted into place using hand equipment or light compaction equipment. • A non-woven geotextile, such as Mirafi 140N (or approved equivalent), should be used to separate the drainage layer from native soil, topsoil or fill with significant fines (silt or clay) content. Page 2 of 3