3005 PANAVIEW BLVD 2016-01-01 MF Import

J�io i�� 9��-iit� ^ support the mnstruction of a rock buttress across a gendy sloping bench below ttie steep portion of the failure and rnplacement of the failed material with large diameter quarry � rock Our mnceptual design is shown on the plan and cross section shown on Figures 4 and 5. It includes the mnstruction of a keyway trench on the gendy sloping bench about 50 ��-� feet down the slope from the crest The keyway trench will serve to support the rock buttrese fill and collect surface and groundwater seepage from the alope. The keyway '� trench should be excavated through the landslide debris and mlluvium and into the '� � dense native outwash sand. Once the keyway trench and drainage pipes are mnstructed it will be backfilled with large diameter(6-to 8-inch)angular quarry rocks. r" The remainder of the slope soils lost in the mud/debris flow will be replaced with �� angu]ar quarry rock(3-ta 6-inch diameter)placed an the slope against the keyway � buttrnse. i � � We have provided a detail of the drainage system to be installed in the bottom of the keyway. The drainage pipe shall be bedded on a minimum of six inchea of one-and-a- C", half inch diameter rounded drain rock and mvemd with a minimum of twelve inches of 1'� drain rock The drain rockshall be wrapped with a non-woven geotextile drain fabric with a minimum twelve inch overlap. A cleanout riser pipe shall be provided at the Y`! lceyway trench to allow periodic cleaning of the pipe in the keyway. A semnd cleanout � + shall be located in the two tightline outlet drain pipes that discharge to the creek All cleanout risers are to be provided with a removable cap. r� � e Constrnclion Accese md ObeervaHon � i Implementation of our rncommendations will rnquire accesa to your backyard for construction equipment We undeistand that you may be mordinating work on your ' " slide with your neighbor to the south,Mr.Lund. The obvious access route is from the � �" street and down behveen your two houses. It will require removal of landscaping rockeries and several sheda. These ibems will have to be re-constructed after the slope ' ° work is done. Access down onto the lower portion of the slope to install the keyway ' trench and mnstruct the rock buttress will likely be made by cutting a ramp down from your backyard through the slide acarp. We strongly suggest mntacting several ' ' mntractora to look at the pmject and provide a plan for eite accesa and soil mmoval with � * their construction bids. In addition,work on your neighbora landslide repair will likely rnquire the sa�mnstruction access as your lot. There rnuld be a significant benefit to ' coordinating your work through the same mntractor. , Several aspects of the reatedial rnnstruction will rnquire our participation in the field. ' Specifically the excavation of the keyway trench. We should be on-site to verify the ' adequacy of the depth and length of the trench and observe the installation of the draut gravel and pipe. .., �-. Golder Associafes