4812 HARBOR LN 2018-01-02 MF Import

December 3,199E Project No. T4199 We did not observe groundwater in the borings drilled on -site. The sandy silt found near the surface in Test Boring B-2 was soft and wet immediately below the topsoil, indicating some surface water infiltration despite the sloping terrain. The upper loose silty sand observed in Test Boring B-1 is more permeable than the sandy silt, which allows for continued vertical migration of infiltrated surface runoff. This vortical flow would not be impeded witil encountering the less pervious, very dense silty sand observed at a depth of about five fat. At this depth, flow will likely turn laterally along the loose/dense soil contact. Although we did not observe this condition at the time of our study, we expect it would develop in the late winter months. 4.0 DISCUSSION AND RECOMMENDATIONS Based on our study, in our opinion, there are no geotechnical conditions that would preclude construction of the proposed residence. It will be necessary to extend foundation footings below the upper loose native soils to obtain support on the dense, more competent soil. This will require extending footings to a depth of about five fat in the vicinity of Test Boring B-1 and throe fat at 'test Boring B-2. It should be anticipated that some foundation excavations may encounter loose or disturbed soils below these depths. If encountered, these excavations should also be extended to firm native soils. Fill soils should not be placed on the steep slope located on the west side of the proposed construction. Any structural fill soil placed on the site for building or driveway construction should be supported by engineered retaining walls. Most of the native soils encountered at the site contain a significant amount of frees and will be difficult to compact as structural fill when too wet. For this reason and for stability and erosion considerations, we recommend grading and excavation ')e completed during the dry summer season (June -September). If grading activities must take place during the winter season, the owner should be prepared to import free -draining granular material for use as structural fill rnd backfill. The following recommendations should be incorporated into the project design drawings and construction specifications. These recommendations are preliminary and may be altered or augment-d upon review of the final plans. 4.2 Geologic Hazards Slope Stability Our site reconnaissance did not reveal any recent or older slides in this area. In our opinion, provided the recommendations contained in this report are followed, development of the site would not increase the potential for slope instability on the site or on adjacent properties. However, with steep -sloping sites, there is always a possibility of a slope failure and the owner must be willing to accept this risk, even if it is minimal. Page No. 3