Laserfiche WebLink
330 Land Company, LLC Arroyo Lago <br />9785.004.001 Design-Level Geotechnical Report <br /> <br /> <br /> Page | 13 April 16, 2024 <br />Latest Revision October 31, 2025 <br />TABLE 3.5-1: Total Estimated Differential Settlement in Fill Slope Areas <br />ADDITIONAL CIVIL FILL <br />(feet) <br />ESTIMATED SETTLEMENT (inches) <br />LOWER BOUND UPPER BOUND <br />0 ¾ 1 <br />1 1 1½ <br />2 1½ 1¾ <br />3 1¾ 2¼ <br />4 2 2¾ <br />5 2½ 3 <br />6 2¾ 3½ <br />7 3 4 <br />8 3½ 4½ <br /> <br />Much of this differential settlement will likely occur in the first 5 years after placement, but may <br />continue for up to 50 years or more. The total amount of settlement across the site is expected to <br />vary based on the heterogeneous conditions of the subsurface soil and expected proposed <br />grades. We discuss options to mitigate differential fill in Section 5.3.1. <br /> <br />3.5.2 Emergency Swale <br /> <br />As described in Section 1.2, an emergency drainage swale was constructed for drainage <br />purposes that will be backfilled as a part of grading operations. Up to 7 feet will be placed to fill <br />the emergency drainage swale to pad grade, with fill ranging from 3 to 7 feet across building pads. <br />We discuss options to mitigate differential fill in Section 5.3.2. <br /> <br />3.6 SOIL CORROSION POTENTIAL <br /> <br />As part of this study, we obtained a representative soil sample that we submitted to a qualified <br />analytical lab for determination of pH, resistivity, sulfate, and chloride. The results are <br />summarized in the table below. <br /> <br />TABLE 3.6-1: Corrosivity Test Results <br />SAMPLE <br />LOCATION <br />REDOX <br />(mV) pH RESISTIVITY <br />(OHMS-CM) <br />SULFIDE <br />(MG/KG) <br />CHLORIDE <br />(MG/KG) <br />SULFATE <br />(MG/KG) <br />1-B2 at 3.5 feet 280 7.91 2400 - 40 41 <br /> <br />The 2025 CBC references the 2019 American Concrete Institute Manual, ACI 318-19, <br />Section 19.3.1 for concrete durability requirements. Based on the test results and ACI criteria, the <br />tested soil would classify as ‘Not Applicable – S0’ for sulfate exposure; there is no requirement <br />for cement type or water-cement ratio for this category. It should be noted, however, that the <br />structural engineering design requirements for concrete may result in more stringent concrete <br />specifications. <br /> <br />According to CERCO Analytical, the soil is moderately corrosive to buried metal piping based on <br />the resistivity measurements. The reported values of chloride and pH concentration do not pose <br />a significant impact to metal or concrete. The laboratory test results by CERCO Analytical are <br />included in Appendix C. <br />