Geotechnical Soil Infiltration Investigation <br />2610 Cal Young Road, Eugene, Oregon <br /> <br />3 | P a g e CORE GeoEngineering, Inc. Project No. 25-1127 <br /> Version 1.0, January 23, 2026 <br /> <br />Geologic mapping1 indicates that the site is directly underlain by Pleistocene-aged (approximately 2.6 <br />million to 11,000 years ago) silt, sand, and gravel (Qs). The Quaternary deposits typically consist of <br />Holocene-aged alluvium and Pleistocene-aged floodplain deposits. These sediments, deposited by the <br />Willamette and McKenzie Rivers, include unconsolidated sand, silt, clay, and gravel, forming the modern <br />floodplain and low terraces. The extent and thickness of the Qs deposits vary across the Eugene area, <br />primarily influenced by historic river migration. <br /> <br />A review of water well reports filed with the Oregon Water Resources Department (OWRD) identified two <br />water supply wells located in the vicinity of the subject property. Well LANE 57683 was constructed in <br />1999 to a total depth of 60 feet below ground surface (bgs). The well log indicates soil from 0 to 2 feet <br />bgs, clay from 2 to 16 feet bgs, and gravel and sand from 16 to 60 feet bgs. The static water level was <br />reported at 23 feet bgs on November 11, 1999. Well LANE 69794 was constructed in 2009 to a total depth <br />of 120 feet bgs. The well log indicates topsoil from 0 to 2 feet bgs, loam from 2 to 10 feet bgs, gravel with <br />clay from 10 to 80 feet bgs, and gravel with clay from 80 to 120 feet bgs. The static water level was <br />reported at 40 feet bgs on August 7, 2009. <br /> <br />The Web Soil Survey (United States Department of Agriculture, Natural Resources Conservation Service <br />[USDA NRCS, 2025 Website]) indicates that near-surface soils at the site consist primarily of the Salem- <br />Urban Land Complex (map unit 119), with the Courtney gravelly silty clay loam, 0 to 3 percent slopes (map <br />unit 2224A) extending across the northern portion of the property. Salem soils are very deep, moderately <br />well drained soils that formed in silty glaciolacustrine deposits on terraces within the Willame tte Valley. <br />The surface horizons typically consist of dark grayish brown silt loam underlain by silty clay loam to silty <br />clay with slow permeability. The Courtney series consists of very deep, poorly drained soils formed in <br />mixed alluvium on low stream terraces and floodplains, characterized by gravelly silty clay loam surface <br />horizons and very slow permeability. Areas mapped as Urban Land represent portions of the landscape <br />where native soils have been modified or covered by impervious surfaces such as roads, driveways, or <br />building pads, resulting in variable soil conditions. The mapped soil units at this site are classified as <br />Hydrologic Soil Groups B (Salem) and D (Courtney), indicating moderate infiltration rates for the Salem <br />series and very slow infiltration rates (high runoff potential) for the Courtney series. <br /> <br />According to EugMaps (City of Eugene, Oregon, 2025), the soils at the site are classified as <br />Hydrologic/Permeability Soil Group B across the majority of the property, with a zone of Soil Group D <br />extending across the northern portion. Soils in Group B typically exhibit moderate infiltration rates when <br />thoroughly wet and consist of moderately well drained to well drained materials with moderately fine to <br />moderately coarse texture. Soils in Group D typically exhibit very slow infiltration rates (high runoff <br />potential) when thoroughly wet and typically consist of clays with high shrink-swell potential, soils with a <br />high water table, soils with a claypan or clay layer at or near the surface, or soils that are shallow over <br />nearly impervious material. <br /> <br /> <br /> <br />1 Generalized Geologic Map of the Willamette Lowland, US Department of the Interior, US Geological Survey, Professional <br />Paper 1424-A, Gannett and Caldwell, 1998.