7505 SEAWAY BLVD Geotech Report 2022-10-25

November 11, 2016 HWA Project No. 2014-117-21 method ASTM D1557 (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 and/or improper moisture content. Soils with high fines contents are particularly susceptible to becoming too wet, and coarse-grained materials easily become too dry, for proper compaction. 4.8.6 Wet Weather Earthwork If earthwork is to be performed or fill is to be placed in wet weather or under wet conditions when soil moisture content is difficult to control, the following recommendations should be incorporated into the contract specifications. • Earthwork should be accomplished in small sections to minimize exposure to wet weather. Excavation or the removal of unsuitable soil should be followed promptly by the placement and compaction of a suitable thickness of clean structural fill. The size and type of construction equipment used may have to be limited to prevent soil disturbance. • Material used as structural fill should consist of clean, granular soil, containing less than 5 percent by dry weight passing the U.S. Standard No. 200 sieve, based on wet sieving the fraction passing the 3/4-inch sieve. The fines should be non-plastic. • The ground surface within the construction area should be graded to promote rapid runoff of precipitation, and to prevent surface water from ponding. • No soil should be left uncompacted so it can absorb water. The ground surface within the construction area should be sealed by a smooth drum vibratory roller. Soils which become too wet for compaction should be removed and replaced with clean granular materials. • Excavation and placement of fill should be observed by the geotechnical consultant to verify that all unsuitable materials are removed and suitable compaction and site drainage is achieved. • Bales of straw and/or geotextile silt fences should be strategically located to control erosion. 2014-117 Final Geotechnical Report 15 HWA GEOSCIENCES INC.