400 RIVERSIDE RD SEPA 016 - 039 - RIVERSIDE BUSINESS PARK Geotech Report 2025-04-14

' December 8,2016 Project No. T-7388-1 5.2 Site Preparation and Grading ' As noted, the site has been subject to previous grading to establish current fill pad elevations. Prior to placing new fill or constructing footings, all exposed bearing surfaces should be observed by a representative of Terra Associates, Inc. to verify that soil conditions are as expected and suitable for support of new fill or building elements. Our representative may request proofrolling the exposed subgrade for pavement and floor slab support ' with a loaded 10 yard dump truck. If unstable soils are observed and cannot be stabilized in place by compaction, the affected soils should be excavated and removed to firm bearing and grade restored with new structural fill. ' All building footings should obtain support on a minimum of two feet of granular structural fill. The fill should extend laterally from the edge of footing a minimum distance of one-foot. As noted earlier, the results of our field exploration indicates that most of the existing fill at the site appeared suitable for support of building ' footings. However, areas of loose fills were also found that will require improvement by compaction. Also deeper footings such as for shear walls and adjacent to the loading dock could extend below the medium dense fills and may require some overexcavation and grade restoration with structural fill. This should be confirmed by ' observation at the time of footing excavation and construction. We recommend that existing fill subgrade exposed below footings be re-compacted to meet structural fill requirements outlined below. ' Our study indicates that the native and existing fill soils contain a sufficient percentage of fines(silt and clay size particles) that will make them difficult to compact as structural fill if they are too wet or too dry. Accordingly, ' the ability to use these native and existing fill soils from site excavations as structural fill will depend on their moisture content and the prevailing weather conditions when site grading activities take place. Native and existing fill soils that are too wet to properly compact could be dried by aeration during dry weather conditions or ' mixed with an additive such as cement or lime to stabilize the soil and facilitate compaction. If an additive is used, additional Best Management Practices (BMPs) for its use will need to be incorporated into the Temporary Erosion and Sedimentation Control plan (TESC) for the project. If grading activities are planned during the wet winter months, or if they are initiated during the summer and ' extend into fall and winter, the contractor should be prepared to import wet weather structural fill. For this purpose,we recommend importing a granular soil that meets the following grading requirements: U.S. Sieve Size Percent Passing ' 6 inches 100 No. 4 75 maximum No. 200 5 maximum* *Based on the 3/4-inch fraction. Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural ' fill. ' Page No. 5