1318 37TH ST Geotech Report 2018-01-02 MF Import

. James Pirie • t JN 97072 • March 15, 1997 Page 3 Groundwater Neither c,roundwater seeFage nor � et s�ils were observed in our explorations. Sinc2 the test pits were cnnductad follcwing a wet wir�te�, :his indicates that substantial groundwater seepaya would likely not be encountered on most portions of the site during excavation. It should be noted that groundwater levels vary seasonally with rainfall and other factors. We an;icipate that groundwater cou�d be found between tiie near-surface, weathered soil 2nd the underlying dense sand�, and in more permeable soil layers withir, the dense sands. This is most likely to occur in low arezs of the property. COtdCLUSIONS AND RECOMMENDATIONS General 6ased on our observatior�s and the results of our explorations, the pmposed site development appears feasible from a geotechnical engine�ring standpoint. The presence of silty, moisture- sensitive soils and the extensive grading that is planned appear to be the most si�nificant geotechnical concerns. . Conventional foundations can be used to supoort the buildings and retaining walis. Cut portions of the buildings should bear on medium-dense to dense, native :,oils. No more than 5 feet of structural fill placed above the mediiam-dense to dense, native soils should underlie footings. This ' reduces tt:� potential f�r excessive differentiai settlement throughout the buildings. It wili also likely be necessary to extend columns and foundation walls beneath portions of the building to limit �fifferential settlement. Floors and garage slabs c:�� be supported on native soils or structural fill. All topsoil and existing `II should be removed from slab or pavement areas before placing structurel fill. Slabs over deep fills should be reinforce�� with steel bars. This wili limit, but not prevent, differential slab settlement • aiid cracking. Flexible fill walis, such as geogrid-reinforced rockeries or modular block walls, should be considered for parkiny areas where new deep fills will be placed. These walls can tolerate more seltlement than conventional concrete walls without structural damage. The on-site soiis are silty and fine-grained, making them moisture-sensitive. Reuse of the native silty sands as structural fill will only be possible during dry weather and if the excavated soils are prevented from becoming wet prior to placement and compaction. No wet soils were observed in our explorations. If very moist to wet soils are encountered during earthwork, they v✓ill need to be dried prior to compaction. lhis is generally only possible during hot, dry weather. A�equate compaction of all fill, in�luding utility backfill, for structural areas must be completed in accordance with our recommendations to limif the potential for settlement. Erosion cont�ol measures will be necessary at this site during wet weather. As a minimum, rock construction =ntrances should be provided and silt fences should be installed along the downslope sides of the property. Subgrades for footings and slabs should be protected with a 2- to 4-inch layer of gravel. This reduces subgrade disturbance due to foot traffic. Additional erosion and subgrade protection measures may be necessary, depending an the conditions ercountered during , construction. —� � GEOTECH CONSULTANTS,INC. ul�