3214 BROADWAY SEPA 017 - 004 Geotech Report 2025-04-14

American Property Devel,r.nent ES-0599.05 January 16, 2015 Page 13 Updated January 22, 2015 Drainage The presence of excessive groundwater seepage is not expected in the general site and utility excavations. However, zones of perched seepage are possible and may produce moderate flow rates within the site excavations. Temporary measures to control groundwater seepage and surface water runoff during construction would likely involve interceptor trenches and sumps, as necessary. Based on groundwater seepage conditions observed at the test sites, we do not anticipate extensive dewatering of excavations will be necessary. At this time we do not anticipate a permanent sub-slab drainage system will be necessary for this project. However, the location and depth of groundwater seepage and zones of chronic groundwater are difficult to predict. Therefore, if unanticipated groundwater conditions are encountered, the geotechnical engineer should reassess the need for additional drainage below the slab during construction. Utility Trench Backfill In our opinion, the soils observed at the test sites are generally suitable for support of utilities. Excessively loose or unstable soils encountered in the trench excavations should not be used for supporting utilities. In general, the on-site soils observed at the test sites should be suitable for use as structural backfill in the utility trench excavations, provided they are at or near the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable specifications of the city or county jurisdictions, as appropriate. LIMITATIONS The recommendations and conclusions provided in this geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the boring and test pits locations may exist, and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction. Earth Solutions NW, LLC