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June 13, 2023 HWA Project No. 2022-188-21 from 5.75 to 17.25 feet. This soil consists of alluvium deposited in the past by laterally migrating channels of the Yakima River. These soils exhibit moderate to high strength and low compressibility. Except at the locations of BH-4 and BH-5, the water table was encountered in this unit at depths of 7.5 to 11.5 feet below the existing ground surface during our explorations. 3.4 GROUND WATER During our subsurface exploration, conducted on February 28, 2023, during the winter season, the ground water table was encountered at depths ranging from 7.5 to 11.5 feet below the ground surface in our explorations. Ground water surface data collected at the site over an 8-month period (April to November, 2020a) by Jacobs indicates seasonal variation ranging from 5 to 8 feet depending upon the time of year, with groundwater deepest in early spring and late fall, and highest during the summer months. Depending upon location, groundwater should be expected to be within 2 feet of the surface during the summer irrigation season. In view of our findings and available information, we expect that ground water will be encountered in the sub - excavation for the scale facility, transfer station, and potentially the MRW and administration building foundations. Interpreted groundwater sections developed by Jacobs (2020a) indicate that groundwater surface elevations are sloped down towards the south following the surface topography. 3.5 SOILS According to the Soils Survey of Kittitas County (available from Natural Resources Conservation Service (MRCS) — Web Soil Survey online), the project site is predominately underlain by Cleman very fine sandy loam, 0 to 2 percent slopes, Nanum ashy loam, 0 to 2 percent slopes, Zillah silt loam, 0 to 2 percent slopes, and Nack-Opinish complex, 0 to 2 percent slopes. These soils form on flood plain and alluvial fans and are derived from alluvial material with an influence of volcanic ash in the surface. These soils, except for the Cleman series (Map symbol 424) are considered to be poorly drained and exhibit a shallow groundwater table, usually with the upper 0.5 to 3 feet below the existing ground surface. The Soils Map for the site is shown on Figure 4. 4.0 CONCLUSIONS AND RECOMMENDATIONS 4.1 GENERAL In general, the site is underlain by a veneer of topsoil developed over fine-grained and coarse - grained alluvial soils. The fine-grained alluvium exhibits low strength and moderate to high compressibility due to its moisture content, consistency, and plasticity characteristics. The underlying coarse -grain deposits consisting of sand and gravel generally have high shear strength 2022-188-21 KCTS — Final Geotechnical Report 7 HWA GEOSCIENCES INC.