1528 GRAND AVE Geotech Report 2022-10-25

GeoTest Services, Inc. Report Date 7/17/2019 Anderson Residence- Everett, Washington GTS Project No.19-0384 " ;."'?° Wet Weather Earthwork Fine grained native soils are particularly susceptible to degradation during wet weather. As a result, it may be difficult to control the moisture content of site soils during the wet season. If construction takes place during wet weather, GTS recommends that structural fill consist of imported, clean, well-graded sand or sand and gravel as described above. If fill is to be placed or earthwork is to be performed in wet conditions, the contractor may reduce soil disturbance by: • Limiting the size of areas that are stripped of topsoil and left exposed • Accomplishing earthwork in small sections • Limiting construction traffic over unprotected soil • Sloping excavated surfaces to promote runoff • Limiting the size and type of construction equipment used • Providing gravel 'working mats' over areas of prepared subgrade • Removing wet surficial soil prior to commencing fill placement each day • Sealing the exposed ground surface by rolling with a smooth drum compactor or rubber-tired roller at the end of each working day • Providing up-gradient perimeter ditches or low earthen berms and using temporary sumps to collect runoff and prevent water from ponding and damaging exposed subgrades Foundation Support Based on limited sawcuts performed by others through the existing basement floor, we understand that the existing residence was originally constructed on shallow conventional footings. Any time new construction abuts existing construction, there is a risk of differential settlement between the two phases of construction that must be considered. GTS generally recommends that the foundations for new construction be extended below existing foundations so that the existing foundations are not surcharged. If new foundations are not able to be extended below existing foundations, GTS recommends that the structural loads immediately adjacent to the existing foundations be kept relatively low to mitigate the risk of differential settlement. Based on the subsurface conditions encountered in our explorations, shallow conventional foundations constructed upon firm and unyielding native soils or properly compacted structural fill overlying firm and unyielding soils are suitable for the proposed construction. The presence of loose, previously placed fill soils and generally loose Recessional Outwash suggests that foundation subgrades should be remedially compacted to a firm and unyielding condition prior to the 9