3800 RIVERFRONT BLVD Geotech Report 2023-05-04

1 March 26, 2019 HWA Project No. 2015-061-21 Task 600-7 Common Borrow Fill soils The near surface fill soils consist of predominantly glacial till derived fill that was compacted to 90 percent of modified proctor or better at the time of placement. Given the high fines content of this material, it is considered highly moistures sensitive and will degrade under construction equipment during periods of wet weather. It is our understanding that construction of the roadway utilities is expected to start in spring of 2019. As wet weather conditions are expected in the spring months, the near surface fill soils are expected to degrade under construction traffic associated with the utility installation. If not mitigated, this degradation will likely impede construction progress and reduce the integrity of the road subbase. To mitigate this potential, we recommend that the contractor be prepared to place a crushed rock working surface along the proposed utility alignments. This thickness of this working crushed rock surface should be determined in the field based on needs at the time of utility installation. We expect that this crushed rock working surface will be lost into the subgrade soils during utility installation and not reusable for road base. We expect that standard trench boxes will be a sufficient means of temporary shoring for the utility installations. Cement Treated Soil An 18-inch thick layer of cement treated soils is expected within the near surface soils along , portions of the roadway. The cement treated soil was constructed with relatively low cement content to allow for future excavations through the layer. However, the contractor should expect increased difficulty excavating through the cement treated layer. We expect that the cement treated layer can be excavated with standard excavation equipment. However, if excavation through the cement treated layer results in removal of large intact slabs of the treated soils that disturb the trench sidewalls, the subject layer should be broken up prior to removal. Refuse Where refuse is encountered within utility excavations handling, stockpiling and disposal of the refuse shall be completed per the requirements of the Consent Decree and the approved Health and Safety Plan. 4.4.6 Utility Foundation Recommendations Proposed utilities may be founded within the near surface fill soils or within the underlain refuse where the refuse is close to the ground surface. Specific foundation recommendations are ' provided below for both conditions. Utilities Founded in Fill The near surface fill soils will provide suitable support for the new utilities and associated manholes, if they are properly excavated and prepared. Geotechnical Report Revision 3 26 2019.doc 16 HWA GEOSCIENCES INC.