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330 Land Company, LLC Arroyo Lago <br />9785.004.001 Design-Level Geotechnical Report <br /> <br /> <br /> Page | 12 April 16, 2024 <br />Latest Revision October 31, 2025 <br />The former fill stockpile as described in Section 2.1 resided for approximately 10 years or more <br />and appeared to range from 5 to 15 feet in height according to historical topography. The former <br />fill stockpile acted as a surcharge according to our analysis, resulting in the following settlements <br />if civil fill were to be placed in those areas: <br /> <br />TABLE 3.4-2: Total Estimated Settlement in Areas outside of Busch Pit – <br />Former Fill Stockpile Area <br />ADDITIONAL CIVIL FILL (feet) ESTIMATED SETTLEMENT (inches) <br />0 ½ <br />1 ½ <br />2 ½ <br />3 1 <br />4 1 <br />5 1 <br />6 1 <br />7 1 <br />8 1 <br /> <br />Much of the settlement from Tables 3.4-1 and 3.4-2 will likely occur in the first 5 years after <br />placement, but may continue for up to 50 years or more. The total amount of settlement across <br />the site is expected to vary based on the heterogeneous conditions of the subsurface soil and <br />expected proposed grades. <br /> <br />To mitigate long-term total and differential settlement from compressible soil, “pre-compression” <br />of the compressible layers prior to site development can be used to reduce the future long -term <br />settlement. In general, pre-compression of compressible soil can be achieved through a <br />surcharge loading program, as described in Section 4.1. <br /> <br />3.5 DIFFERENTIAL FILL <br /> <br />In addition to settlement due to compressible soil, differential building movements may result from <br />conditions where building pads have significant differentials in underlying engineered fill <br />thickness. We provide discussion for lots potentially affected by differential fill thickness in the <br />following sections. <br /> <br />3.5.1 Busch Pit <br /> <br />According to SMP-31 and historical topography, the northern pit typically comprised side slopes <br />of approximately ¾:1 to 1:1 (horizontal:vertical) and Busch Pit comprised side slopes of <br />approximately 1.1:1 to 2:1. Both the northern pit and Busch Pit were supposedly backfilled to <br />present day conditions without keying into native material, creating a potential differential fill slope <br />condition that may induce differential settlement under new loading scenarios. <br /> <br />Residential lots that span the former side slopes of the northern pit and Busch Pit can potentially <br />settle differentially when a new loading scenario is introduced. We estimate the following <br />differential settlement may occur if the differential fill condition is left unmitigated. The differential <br />settlement for the lots in the northern pit should be added to the estimated settlement for <br />compressible soil presented in Section 3.4. We present lots potentially affected by differential fill <br />conditions in Figure 2C.