Chapter 12.12 — SOILS AND ENGINEERING GEOLOGY REPORT

The soils and engineering geology report shall be prepared by a professional soil investigation firm under the direction of a soils engineer and an engineering geologist and shall include the following:

• A. An adequate description of the geology of the site;

• B. Conclusions and recommendations regarding the effect of geologic conditions on the proposed development;

• C. Opinions and recommendations covering the adequacy of sites to be developed by the proposed grading;

• D. Data regarding the nature, distribution, strength, and in place relative compaction of existing soils;

• E. Conclusions and recommendations for grading procedures and design criteria for corrective measures when necessary;

• F. Ground water conditions;

• G. Data on erodibility of the soil;

• H. Draft specifications for erosion control measures. For purposes of such draft specifications, reference is made to Association of Bay Area Governments Manual for Surface Runoff Control Measures, pages 1-45, through 1-151, inclusive.

• (Prior code § 9-1.7(a); Ord. 1369 § 1, 1981)

Recommendations included in the report and approved by the city engineer shall be incorporated in the grading plans and/or specifications. (Prior code § 9-1.7(b); Ord. 1369 § 1, 1981)

Sufficient soils samples to represent a true cross-section of the cut and fill areas and of the material to be used as fill shall be taken and tested under the supervision of the soils engineer. All soils shall be classified in accordance with the unified soil classification system. Reports, including all test reports by the soils engineer, shall be submitted covering the following:

• A. Field and laboratory tests of the land to be covered with fill to determine the characteristics of the soil, including its expansive qualities; the bearing value of the land; consolidation potential; data on erodibility of the soil; and a statement as to whether the land can support the proposed fill and structures. In those areas where saline or alkaline soils or other problem condition may be encountered, sufficient information to define the problem and evaluate its solution shall be submitted to the city engineer.

• B. Field and laboratory soil analysis of the material proposed for the fill, including its source and expansive quality, and a statement as to its suitability. The analysis shall also specify the optimum moisture content at which each type of proposed fill material compacts to one hundred percent dry density in accordance with State Department of Transportation Impact Method (Test No. 216F) or an equivalent approved by the city engineer. The city engineer may defer this requirement until some grading has been done in order to obtain good representative samples.

• C. Field and laboratory soil analysis of existing soil conditions in proposed cut locations, including expansive qualities and bearing values. If steep slopes are proposed, sufficient data concerning slope stability analysis shall be submitted.

• D. Any potential ground water condition which may affect soil strength, consolidation, or slope stability shall be defined and evaluated. This is of particular significance in areas subject to vibratory or shock loadings.

• E. Proposals to replace, rework or blend, or to stabilize or modify with additives either natural site soils or the proposed fill materials shall be supported by appropriate laboratory analysis and other such data as may be necessary for evaluation of the proposal.

• F. The location of and effects of active faults which may affect the proposed development. The results of seismic activity on the soils as the site is proposed to be graded and on the proposed buildings and structures shall be evaluated. Recommendations shall be made relating to building distances from nearby active faults and foundation design due to seismic activity.

• (Prior code § 9-1.7(c); Ord. 1369 § 1, 1981)

• A. The soils engineer shall prepare a complete and detailed specification for clearing, grubbing, and all aspects of grading, including utility trench backfill, with special emphasis on the depth of fill layers, compaction methods, moisture content, frequency of field density tests, and minimum density to be obtained in the field as related to laboratory density tests.

• B. The soils engineer shall prepare a statement regarding specified grading and slopes, giving a professional opinion regarding the following:

  1. Shrinkage or settlement of a fill constructed in compliance with the proposed specification for controlled earthwork;

  2. The safe load-bearing capacity for such controlled site;

  3. The maximum slope ratios necessary for slope stability for proposed cut and fill slopes, with the assumption of proper planting on the slope to assure freedom from erosion; and

  4. The remaining movement anticipated in cut areas. Any forecast of appreciable settlement shall be supported by appropriate site and soils data.

(Prior code § 9-1.7(d, e); Ord. 1369 § 1, 1981)

A complete and detailed plan for erosion control shall be prepared and included within the grading plan. If planting is proposed, the specification shall be prepared by a registered landscape architect or landscape contractor and shall indicate the material and methods for slope control planting and planting to return the slope to its native appearance, including ground covers, trees and shrubs, and with special emphasis on the following:

• A. Soil preparation, fertilization, plant material, and methods of planting; and

• B. Initial maintenance of the plant material and slopes until a specified percentage of plant coverage is established uniformly on the cut and fill slopes.

The erosion control plan shall contain calculations showing estimated surface water runoff on the site and maintenance of non-vegetative erosion control measures. Vegetative control measures shall be in accordance with Association of Bay Area Governments Manual for Surface Runoff Control Measures, pages 1-50 through 1-57, inclusive.

(Prior code § 9-1.7(f); Ord. 1369 § 1, 1981)

The city engineer may require additional soils or geological investigations to be made in order to further the safety and maintainability of the site. (Prior code § 9-1.7(g); Ord. 1369 § 1, 1981)