2414 BAKER AVE 2017-01-13 - Laserfiche WebLink

Tom Eiden JN 10114 June 21, 2010 Page 7 We recommend that the contractor, the project materials engineer, and the owner discuss these issues and review recent ACI literature and ASTM E-1643 for installation guidelines and guidance on the use of the protection/blotter material. Our opinion is that with impervious surfaces that all means should be undertaken to reduce water vapor transmission. EXCAVATIONS AND SLOPES Excavation slopes should not exceed the limits specified in local, state, and national government safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be made near property boundaries, or existing utilities and structures. Based upon Washington Administrative Code (WAC) 296, Part N, the soil at the subject site would generally be classified as Type B. Therefore, temporary cut slopes greater than 4 feet in height should not be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. The above-recommended temporary slope inclinations are based on the conditions exposed in our explorations, and on what has been successful at other sites with similar soil conditions. It is possible that variations in soil and groundwater conditions will require modifications to the inclination at which temporary slopes can stand. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the construction of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with ptastic sheeting during wet weather. It is also important that surface water be directed away from temporary slope cuts. The cut slopes should also be backfilled or retained as soon as possible to reduce the potential for instability. Please note that loose soil can cave suddenly and without warning. Excavation, foundation, and utility contractors should be made especially aware of this potential danger. These recommendations may need to be modified if the area near the potential cuts has been disturbed in the past by utility installation, or if settlement-sensitive utilities are located nearby. All permanent cuts into native soil should be inciined no steeper than 2:1 (H:V). Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. All permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the surficiai layer o� soil. TEMPORARY SHORIN� A variety of shoring systems are feasible for use at this site. The following sections present design considerations for cantilevered soldier-pile walis, and Ultra block walls. The use of Ultra biock walls will require a temporary excavation easement from the northern neighbor to allow for the risk of minor sloughing over the property line during block installation and to prevent any vehicie loading to the wall until the permanent basement wall is constructed. Similariy, if slope cuts can be extended into the alley and all traffic can be kept at least 10 feet from the back of the block wall until the basement walls are installed, Ultra blocks could be used along the western side of the excavation as well. Since the most suitable shoring choice is primarily dependent on a number of factors under the contractor's control, we suggest that the contractor work closety with the structural engineer during the shoring design. As discussed above, the sensitivity of adjacent pavements and utilities must be considered in the design to reduce the risk of causing settlement of these adjacent elements. Regardless of the system used, all shoring systems will deflect in toward the excavation. Therefore, there is always a GEOTECH CONSULTANTS. INC.