11731 AIRPORT RD Geotech Report 2018-01-02 MF Import

08/18/2885 15:27 4257478561 GEOTECH PAGE 09 Lucia Dsirobpment, L1.0 JN 05233 August 18, 2005 Page 8 as detertnined by ASTM E 96. It is possible that eonerete admixtures may meet thfs spedficaUon, aRhough the manufacturers oi the admixtures ahould lx ConsuRed. Where plastie sheeting is used under slabs, jaiMs should oveAap by at least 6 inehes and be sealed with adhesive tape. The sheeting should extend to ihe foundation waAs for maximum vapor protection. If no potential for vapor passage through the slab is desired, a vapor barrier should be used. A vapor barrier, as defined by ACI, is a product with a water transmission rete of 0.00 pertns per square foot per houf when tested in accordance with ASTM E 96. Reintorced membrenes having sealed overiaps Can meet this requirement. In the recent past, ACI (Sectio� 4.1.5) recommended that a minimum of 4 inches of well-greded eompactable granular material, such as a 5/8 ineh minus crushed rock pavement base, should be placetl over the vapor retarder or barrier for protection of the retarder or barrier and as a "blofleP to aid in the curing of the concrete slab. Sand was not recommanded by ACI far this purpose. However, the use of material over the vapor retardar is eontroversial as noted in currerrt ACI literature because af the potential that the protection/blotter material qn become wet betwee� the time of�ts placement and the installation of the siab. If the mata�ial is wet prio�to slab placement, which is aNvays p�sible in the Puget Sound area, it could cause vapor transmission to occur up through the slab in the tuture, essentially destroying the purpose of the vapw bartieNretarder. ThereTore, if there is a poterrtial that the protectioNblotter material wili become wet before the slab is instailed, ACI now recommends that rro protection/blottar material be used. However, ACI then recommends that, because there is a potential for slab cure due to the loss of ttte blotter material, jant apacing in the siab 6e redueed, a low shrinkage concrete mi�Rure be used, and "other measures"(steei reirtforcing, etc.) be used. AS7M E-1643-98"Stantlard Practice for Installatiort of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs" generalty agrees with the reeent ACI literature. We recommend that 1he eorrtractor, the projact 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 oi the protectionlblotter material. Our opinbn is that with impervious surtaces that all means should be undertaken to reduce water vapor transmissian. IXCAVA710NS AND StOPES No excavated Slopes are anticipated other than for uhlity trenChes. Excavation s!opes ahould not exceed the limits spec�ed in local, state, and national govemment safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, if there are no indieations of slope instability. However, vertical cuts should not be made near property boundaries, or e�sting utilities and structures. Based upon Wasttington Administretive Code (WAC) 296, Part N, the sai at the subjed site would generaily be classified as Type C. Therefore, temporary cut slopes greater than 4 feat in height should not be exCavated at an inelination steeper than 1.5:1 (Horizorrtal:Vertical), eutending continuously between the top and the lwttom of a Cut. The above-recommended temporary slope inclination is based on the cond'ttions exposed in our � explorations, and on what has been suecesstul at other sites with similar soil condkions. It is possible that variations in soil and groundwater conditions will require moditications to the inelination at which temporary slopes can stand. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the constnietion of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wat weather. It is also impoAant that surface water be directed away from temporary sbpe cuts. The cut slopes should also be backfilled ar retained as soon as possible to reduce the potential tor GEOTECH CONSULTANTS,MC.