3535 RIVERFRONT BLVD Geotech Report 2023-02-22

September 24, 2018 HWA Project No. 2015-061-21 • HMA should not be placed on any frozen or wet surface. • HMA should not be placed when precipitation is anticipated before the pavement can be compacted, or before any other weather conditions which could prevent proper handling and compacting of HMA. • HMA should not be placed when the average surface temperatures are less than 45°F. • HMA temperature behind the paver should be in excess of 240°F. Compaction should be completed before the mix temperature drops below 180°F. Comprehensive temperature records should be kept during the HMA placement. • For cold joints, tack coat should be applied to the edge to be joined and the paver screed should be set to overlap the first mat by 1 to 2 inches. 4.8.4 Parking Lot Pavement The parking lot will also be lightly loaded, used primarily by passenger vehicles, with some heavy maintenance trucks expected. We anticipate the subgrade will consist of the existing gravel roadway of Eclipse Mill Road, or of imported embankment materials. For these conditions, we recommend the pavement section consist of at least 3 inches of HMA over 7 inches CSTC and CSBC combined. The majority of the parking lot will be constructed on the existing roadway, which is near the proposed final grade for the project. However, at the north end, we understand that embankment fill may need to be placed to raise the ground surface to the proposed grade. This may result in differential settlements, as the new fill settles relative to the existing fill. Such differential settlement will likely cause premature pavement cracking; most notably, along the area of contact between the new fill and older fill. In order to reduce the potential and magnitude of ' cracking, Tensar Biaxial B 1200 or Triaxial T5X geogrid (or equivalent) could be placed in the middle of the CSBC portion of the pavement section. Additionally, this differential settlement may impede surface drainage which should be accounted for in the selection of finished surface grading elevations. 4.8.5 Subgrade Preparation The subgrade exposed b rade should be thoroughly proof-rolled, under the observation of the P g g Y geotechnical engineer, with oheavy-tiredv hi 1e ( g. fully-loadeddump truck, water truck or similar)prior to construction of the new pavement. All loose or soft areas that exhibit excessive yielding should be over-excavated, to a maximum depth of 2 feet below grade, and replaced with 111 CSBC compacted to a dense and unyielding condition in accordance with Section 2-03.3(14)C P Y g (Compacting Earth Embankments) and/or Section 2-06.3(1) (Subgrade for Surfacing) of the WSDOT Standard Specifications (WSDOT, 2018). If fine-grained soils are encountered at the bottom of the over-excavation, a separator fabric, conforming to the WSDOT Standard Specifications Section 9-33.2(1), should be placed over the exposed subgrade prior to backfilling Final Geotechnical Report-3-Acre Park.docx 25 HWA GeoSciences Inc.