3535 RIVERFRONT BLVD Geotech Report 2023-02-22

September 24, 2018 HWA Project No. 2015-061-21 the over-excavation. Where fine-grained material is encountered, the separator fabric should be used and is not the same as the geogrid recommended in the previous section. 4.8.6 Pavement Drainage It is essential to the satisfactory performance of paved areas that good drainage is provided to prevent water ponding alongside or under the pavement. Water ponding can cause saturation of the pavement and subgrade layers and premature failure. The base layers should be graded to prevent water being trapped within the layer. The surface of the pavement should be sloped to convey water from the pavement to appropriate drainage facilities. Given the expected differential settlements that potentially may occur in various developed areas, water ponding may occur after paving is complete. Again, delaying of paving will decrease the extent and severity of these issues. Some additional maintenance of the drainage along the trail may need to be addressed over the serviceable life of the pavement. 4.9 GENERAL EARTHWORK 4.9.1 Structural Fill Structural fill should consist of clean, free-draining, granular soils free from organic matter or other deleterious materials. Such materials should be less than 4 inches in maximum particle dimension, with less than 7 percent fines (portion passing the U.S. Standard No. 200 sieve), as specified for"Gravel Borrow" in Section 9-03.14(1) of the WSDOT Standard Specifications (WSDOT, 2018). The fine-grained portion of structural fill soils should be non-plastic. Fill material having a fines content greater than 7 percent may be acceptable for structural fill if the earthwork is performed during relatively dry weather and the contractor's methods achieve proper compaction of the soil. Material with a fines content greater than 7 percent should be approved by the project engineer prior to use. 4.9.2 Compaction Structural fill soils should be moisture conditioned and compacted to the requirements specified in Section 2-03.3(14)C, Method C, of the WSDOT Standard Specifications (WSDOT, 2018); except the standard of compaction achieved shall not be less than 95% of the maximum dry density(MDD) determined for the fill material by test method ASTM D 1557 (Modified Proctor). Subgrade compaction in road bed areas should conform to the requirements of Section 2-06.3(1) of the WSDOT Standard Specifications. Achievement of proper density of a compacted fill depends on the size and type of compaction equipment, the number of passes, thickness of the layer being compacted, and soil moisture- density properties. In areas where limited space restricts the use of heavy equipment, smaller equipment can be used, but the soil must be placed in thin enough layers to achieve the required relative compaction. Generally, loosely compacted soils result from poor construction technique Final Geotechnical Report-3-Acre Park.docx 26 HWA GeoSciences Inc.