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City of Arden Hills <br />Project B2204011 <br />June 23, 2022 <br />Page 13 <br /> <br /> <br />D.2.b. Geologic Origins <br />We assigned geologic origins to the materials shown on the logs and referenced within this report, based <br />on: (1) a review of the background information and reference documents cited above, (2) visual <br />classification of the various geologic material samples retrieved during the course of our subsurface <br />exploration, (3) penetration resistance testing performed for the project, and (4) available common <br />knowledge of the geologic processes and environments that have impacted the site and surrounding <br />area in the past. <br /> <br />D.3. Material Classification and Testing <br /> <br />D.3.a. Visual and Manual Classification <br />We visually and manually classified the geologic materials encountered based on ASTM D2488. The <br />Appendix includes a chart explaining the classification system we used. <br /> <br />D.4. Groundwater Measurements <br /> <br />The drillers checked for groundwater while advancing the penetration test borings, and again after auger <br />withdrawal. We then filled the boreholes or allowed them to remain open for an extended period of <br />observation, as noted on the boring logs. <br /> <br /> <br />E. Qualifications <br /> <br />E.1. Variations in Subsurface Conditions <br /> <br />E.1.a. Material Strata <br />We developed our evaluation, analyses and recommendations from a limited amount of site and <br />subsurface information. It is not standard engineering practice to retrieve material samples from <br />exploration locations continuously with depth. Therefore, we must infer strata boundaries and <br />thicknesses to some extent. Strata boundaries may also be gradual transitions, and project planning <br />should expect the strata to vary in depth, elevation and thickness, away from the exploration locations. <br /> <br />