2320 CALIFORNIA ST Geotech Report 2025-07-25

I 1 Pavement Recommendations ' Subgrade Preparation We recommend the subgrade soils in new pavement areas be prepared and evaluated as described in the "Earthwork"section of this report. If the subgrade soils are excessively loose or soft, it may be necessary to excavate localized areas and replace them with structural fill or gravel base material. Pavement subgrade conditions should be observed during construction and prior to placing the subbase materials in order to evaluate the presence of unsuitable subgrade soils and the need for over-excavation. ' New Hot Mix Asphalt(HMA)Pavement In light-duty pavement areas(e.g., automobile parking), we recommend a pavement section consisting of at least a 2-inch thickness of 1/2-inch HMA (PG 58-22) per WSDOT Sections 5-04 and 9-03, over a 4-inch thickness of densely compacted crushed rock base course per WSDOT Section 9-03.9(3). In heavy-duty pavement areas(e.g.,truck traffic areas,materials delivery),we recommend a pavement section consisting of at least a 3-inch thickness of 1/2-inch HMA(PG 58-22) over a 6-inch thickness of densely compacted crushed rock base course. The base course should be compacted to at least 95 percent of the maximum dry density (MDD) per ASTM D 1557. We recommend that a proof-roll of the subgrade and compacted base course be observed by a representative from our firm prior to paving. Soft or yielding areas observed during proof-rolling may require over-excavation and replacement with compacted structural fill. The pavement sections recommended above are based on our experience. Thicker asphalt sections may be needed based on the actual traffic data, truck loads, and intended use. All paved and landscaped areas should be graded so surface drainage is directed to appropriate catch basins. Portland Cement Concrete Pavement Portland cement concrete (PCC) sections should be considered for loading dock aprons, trash dumpster areas and where other concentrated heavy loads may occur. We recommend that these pavements consist of at least 6 inches of PCC over 6 inches of crushed surfacing base course. A thicker concrete section may be ' needed based on the actual traffic data. If the concrete pavement will have doweled joints, we recommend that the concrete thickness be increased by an amount equal to the diameter of the dowels. The base course should be compacted to at least 95 percent MDD. We recommend PCC pavements incorporate construction joints and/or crack control joints spaced at maximum distances of 12 feet apart, center-to-center, in both the longitudinal and transverse directions. ' Crack control joints may be created by placing an insert or groove into the fresh concrete surface during finishing, or by sawcutting the concrete after it has initially set-up. We recommend the depth of the crack ' control joints be approximately 1/4 the thickness of the concrete; or about 11/2 inches deep for the recommended concrete thickness of 6 inches. We also recommend the crack control joints be sealed with an appropriate sealant to help restrict water infiltration into the joints. Asphalt-Treated Base If pavements are constructed during the wet seasons,consideration may be given to covering the areas to be paved with asphalt-treated base (ATB) for protection. Light-duty pavement areas should be surfaced with 3 inches of ATB,and heavy-duty pavement areas should be surfaced with 6 inches of ATB. Prior to placement of the final pavement sections,we recommend that the ATB surface be evaluated and areas of ATB pavement 1 Page 6