Agenda - Public Works Committee - 04/16/2024

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or "N" value. The results of the standard penetration tests are indicated on the boring logs. The samples were sealed in containers and provided to HGTS for testing and soil classification. A field log for each boring was prepared by the HGTS drill crew. The logs contained visual classifications of the soil materials encountered during drilling, as well as the driller's interpretation of the subsurface conditions between samples and water observation notes. The final boring logs included with this report represent an interpretation of the field logs and include modifications based on visual/manual method observation of the samples. The soil boring logs, general terminology for soil description and identification, and classification of soils for engineering purposes are also included in the appendix. The soil boring logs identify and describe the materials encountered, the relative density or consistency based on the Standard Penetration resistance (N-value, "blows per foot") and groundwater observations. The strata changes were inferred from the changes in the samples and auger cuttings. The depths shown as changes between strata are only approximate. The changes are likely transitions, variations can occur beyond the location of the borings. The bituminous cores were obtained in conjunction with the soil borings with a 4-inch diameter diamond studded core barrel using wet coring techniques. 3.0 RESULTS 3.1 Pavement and Soil Conditions The subsurface soils encountered at this site generally consist of three main stratigraphic units: 1) pavements, 2) Fill, 3) Buried Topsoil/Swamp Deposits 4) native alluvial deposits. A brief description of each stratum is presented in the following paragraphs. Pavements The pavement sections consisted of varying thicknesses of bituminous and aggregate base. Bituminous thicknesses ranged from about 13/4 to 4 inches but mostly ranged from about 2 to 21/2 inches. Aggregate base thicknesses ranged from about 3 to 13 inches but was mostly about 3 to 4 inches thick. We could not recover intact pavement cores at borings SB-3, SB-5, SB-6, SB-9, SB-15 and SB-22. The pavements at these borings basically disintegrated while coring. Where possible we attempted to reassemble the cores and measure them to obtain a pavement section thickness. At some locations the pavement cores were to badly damage and we relied on field measurements of the pavement thickness. Therefore, the bituminous thicknesses at these borings are identified as "estimated" or "assumed". The aggregate base thicknesses were likewise not always easy to distinguish. The aggregate base did not appear to contain significant amounts of gravel that are typically associated with Class 5 aggregate base. The lack of gravel was most apparent at soil boring SB-20 completed along 1801h Avenue NW. The observed pavement section thicknesses are summarized in Table 1. The subgrade soil type is also summarized in the table. 3