RES 16819 - Laserfiche WebLink

Significant Impact Impact 4.4-5: Compressible soils and non-engineered fills are present within project boundaries and construction on these soils could cause foundation and other structural failures. Finding Changes or alterations have been required in, or incorporated into, the project which mitigate or avoid the significant effects on the environment. Facts in Support of Finding The City of Pleasanton has adopted the following measures which will reduce potential impacts related to compressible soils and non-engineered fill to a less-than-significant level: Mitigation Measure 4.4-5: All existing non-engineered fill, vegetation, and soft or compressible soils and colluvium in existing canyons, creeks, stock ponds, drainages, and other areas to be graded shall be removed as necessary for project requirements. The depth of removal shall be determined by the geotechnical engineer in the field at the time of grading. Evaluation of unsuitable deposits shall be performed during grading by sampling and laboratory analysis. Significant Impact Impact 4.4-6: Fill placed during construction could settle following construction and cause structural damage. Finding Changes or alterations have been required in, or incorporated into, the project which mitigate or avoid the significant effects on the environment. Facts in Support of Finding The City of Pleasanton has adopted the following measures which will reduce potential impacts related to fill settlement to a less-than-significant level: Mitigation Measure 4.4-6a: The differential fill thickness across a lot should be less than 15 feet. Lots requiring local subexcavation of soil and replacement with engineered fill to achieve this limit should be identified on the final corrective action grading plan. Mitigation Measure 4.4-6b: Following clearing and stripping, all areas to receive fill, slabs-on- grade, or pavement should be scarified to a depth of at least 12 inches, moisture conditioned, and compacted to the requirements for engineered fill. Mitigation Measure 4.4-6c: Site soils and bedrock used for engineered fill shall have organic content of less than 3 percent. Rocks greater than 6-inches in size shall not be placed at depths greater than 10 feet from finished grade. Rocks greater than 18 inches in size should be broken down such that their maximum dimension is less than 12 to 18-inches, or placed in non- structural fills below slopes or under one of the proposed detention basins. Alternatively, these rocks could be used in landscaping and/or creek restoration projects. Mitigation Measure 4.4-6d: Engineered fills shall be compacted to the specifications stated in the geotechnical framework. Over compaction of expansive materials (with a plasticity index of greater than 12) should be avoided within the upper five feet of building areas. All fills shall be LUND RANCH II (PUD-25)RESIDENTIAL PROJECT 14 FINDINGS