RES 99074 - Laserfiche WebLink

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 earth resource impacts to a less-than-significant level: Mitigation Measure 4.2-3: Unstable Deep Fills. All grading plans, cut and fill slopes, compaction procedures, and retaining structures shall be designed by a licensed geotechnical or civil engineer. All grading and slope preparation activities shall be conducted under the supervision of a licensed geotechnical engineer or certified engineering geologist. To the extent possible, grading plans shall minimize earthmoving and site grading. Development design shall avoid placing structures and utilities on or near the tops of slopes or in the shallow subsurface of slopes. In graded construction areas, replacement vegetation shall be planted as quickly as possible. Graded areas that remain inactive for 10 days or more during the rainy season (October 1 to April 1 ) without permanent replanting should be hydroseeded or stabilized to inhibit dust generation. The final geotechnical report for the grading plan for proposed projects shall be prepared by a professional engineer and approved by the City Engineer. The report shall address the potential for delayed (differential settlement) consolidation within deep fills and associated land surface subsidence. The report shall provide specific recommendations for: Fill compaction specifications that consider the likelihood of eventual saturation and wetting and drying cycles for the fill materials; · Removal of colluvial material or weathered rock that may be subject to consolidation under the load of proposed fills; · Design that minimizes the variability of fill thickness within fills that underlie structures or other improvements at the project site; and · Design and operation of adequate subsurface drainage systems for fills (particularly beneath heavily irrigated areas or other water sources such as swimming pools or detention basins). Drainage systems for the fills shall be designed to minimize maintenance and ensure long-term performance. Flow from the drainage system shall be controlled so as not to cause or contribute to erosion of existing drainage channels. SIGNIFICANT EFFECT Impact 4.2-4: ~. The potential for expansive soils on the site to shnnk and swell dependent upon weather conditions could cause damage to structures. The soils throughout the project site exhibit the adverse condition of a moderate to high shrink-swell potential. This condition can cause deformation and damage to structures built on these soils. This impact would be considered potentially significant. Vineyard Avenue Corridor Specific Plan Draft EIR -10- Findings