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Page 2 of 4 increase in student population due to new home development is normally addressed by the school district. The school district includes City input when evaluating its school boundaries and when developing its school modifications. Similarly, PUSD input is incorporated into the City’s housing element update and other projects that could impact the student population. 3: Has the developer (either independently or through the CEQA process) completed geotechnical work to explore issues related to soils and stability in an area previously used for mining? Yes. Section 3.6 of the Draft Environmental Impact Report (DEIR) as prepared by Alameda County for Arroyo Lago discusses "Geology and Soils". This discussion was based on two reports prepared by ENGEO dated April 16, 2024 (revised June 27, 2024) and May 18, 2023. The ENGEO reports also reference earlier reports by other qualified consultants that date back to 2007. The ENGEO reports specifically evaluated soil conditions within the boundary of Arroyo Lago, but did not evaluate vacant land east of Arroyo Lago where the East Lakes subdivision is proposed. The ENGEO reports describe the prior use of the property as a mining quarry with open pit excavations and dirt access roads. The northern pit extended 160 feet below the ground surface and was later backfilled in 1993. The southern pit extended 50 to 70 feet below the ground surface and was backfilled in 2013. The backfilling was performed according to a Surface Mining Permit Reclamation Plan issued by Alameda County, although the type of soil material used, and the method of placement/compaction, was not well documented. To make the property suitable for residential construction, ENGEO recommends a "surcharge program" be employed to compress the soil in the vicinity of the former pits. The surcharge program relies on additional soil placed on top of building pads to force settlement in advance of home construction. Although the depth of additional soil varies by location, up to 14 feet of soil could be placed atop building pads for a duration of up to a year. The settlement will be monitored by regular surveying until the desired settlement is achieved. This additional soil would then be removed and off-hauled. ENGEO also evaluated other potential issues such as expansive soil, earthquake faulting, and liquefaction. The soil at the property contains expansive clay which is common in Pleasanton. Seasonal fluctuations in moisture content have been addressed with specific recommendations for the home foundations to guard against soil expansion/contraction. Earthquake faults, while prevalent in California, are not specifically relevant at the property given the distance to the nearest known fault; liquefaction, which can cause sudden settlement of the soil during a seismic event, is unlikely to occur given the depth of groundwater and cohesion of the soil. As a result of ENGEO's analysis, the DEIR includes Mitigation Measure MM GEO-1 which requires the developer to prepare an updated design-level geotechnical exploration and assessment. The recommendations from the assessment shall be implemented during construction including grading and excavation. By implementing this mitigation measure, the environmental impact associated with the geology and soils at the property is reduced to less than significant.