A. Introduction

A geotechnical report is intended to define the subsurface conditions, and provide geotechnical conclusions and recommendations for design and construction of the project. A geotechnical report requires the stamps from both a Certified Engineering Geologist and Geotechnical Engineer as specified in Subsection I. The Certified Engineering Geologist shall investigate and respond to the applicable criteria listed below. Findings shall be cited in the geotechnical report as an appendix. The purpose for the appendix is to provide geological information for a Geotechnical Engineer, explaining the implications of the subsurface conditions for appropriate project design and construction. The Geotechnical Engineer shall be required to complete the remaining geotechnical report criteria.

Investigation should include the following:

B. General

1. Name, Address, and Phone Number.

2. Client for whom the report was prepared.

3. A description of the proposed project and its location.

4. A site map of the area at a scale of 1:400 or larger. Geologic conditions, topography, and location of proposed structures are to be shown. A copy of published geologic maps shall be also be provided.

5. A review of the geologic history and history of prior excavation and fills.

6. A field reconnaissance of the site and the vicinity.

7. Discussion of geologic hazards.

8. A discussion of the engineering aspects of the site and proposed project. The discussion should address foundation types for proposed structures, retaining systems, grading considerations, stability of cut-slopes and constructed embankments, settlement of the site and adjacent sites due to existing conditions, proposed construction ,and proposed surface and subsurface drainage facilities.

9. A bibliography of all references used.

C. Field Investigations

1. Planned construction (type of structure and use, type of construction and foundation/floor system, number of stories, estimated structural loads.)

2. Scope (date work done, investigative methods, sampling methods, logs of borings/test pits, elevations of borings/test pits for reference of materials and samples to finished grade or footing elevations, identify real or assume elevations.

3. Location of all samples taken, surface and subsurface.

4. Groundwater conditions and potential (future natural and artificial seepage effects).

5. Structural cross-sections (one or more appropriately positioned and referenced on map; especially through critical areas, slopes and slides) of suitable size and engineering scale; with labeled units, features and structures; and a legend. These sections should correlate with surface and subsurface data showing representative dip components, projections and stratigraphic/structural relationships.

D. Engineering/Material Characteristics and Testing

1. Test methods used, type or condition of samples, applicable engineering graphics and calculations, results of all tests, and sample locations of all test samples.

2. Unified Soil Classification of materials.

3. Material competency and strength of existing soils/profile.

a. Pertinent engineering geologic attributes (clayey, weak, loose; alignments, fissility, planar boundaries; pervious or water-bearing parts; susceptibility to mass wasting, erosion, piping, or compressibility).

b. Effects and extent of weathering (existing and relationship to project design and future site stability, material strength.

c. Field densities of unconsolidated field areas and moisture content.

d. Bearing capacity and/or shear strength of areas affected by future foundation placement (drained or undrained conditions, effective stress or total stress analysis, in-situ or remolded samples must be identified).

e. Consolidation or settlement potential.

f. Expansion potential.

4. Maximum density-optimum moisture parameters of proposed fill material.

E. Stability Features and Conditions

1. Adequate mapping, sections and description dimensions and type of existing downslope movement soil/rock creep, flows, falls, slumps, slides, if any.

2. Activity, cause or contributing factors of downslope movement features.

3. Recent erosion, deposition, or flooding, features.

4. Subsidence/settlement, piping, solution or other void features or conditions.

5. Groundwater and surface drainage characteristics or features.

a. Surface expression (past and present); permeability/porosity of near surface materials.

b. Actual or potential aquifers or conduits, perching situations, barriers or other controls to percolation and groundwater movement and fluctuation of groundwater levels at the site.

F. Foundation Design Criteria

1. Footing depth and width.

2. Criteria for foundation material preparation.

3. Allowable bearing values based on testing.

4. Lateral pressures (active, passive, or at rest conditions) and coefficient of friction.

5. Settlement - total, differential, and rate of settlement.

G. Reference

1. In supplemental or grading plan review reports referencing earlier reports, supply copies of those reference reports or applicable portions as required by the Administrator.

H. Conclusions and Recommendations

1. Ground preparation (clearing, unsuitable material removal, scarification and moisturization).

2. Fill support:

a. Suitability and precompaction of in-situ materials (describe test results and other pertinent data to be used to determine suitability).

b. Densification and moisturization or dewatering measures (equipment, surcharge, settlement monitoring, if applicable).

3. Placement of fill:

a. Material approval (on site, imported).

b. Methods and standards (ASTM standards or approved equivalent).

c. Testing (ASTM standards (D1556, D1557, D2167, D2922, D2937, D3017) or equivalent) and frequency of field density testing by vertical intervals and/or volume of fill.

4. Elimination of cut/fill or other differential transitions beneath improvements.

5. Opinion as to adequacy of site for the proposed development (This opinion should also be summarized in the first part of the report.)

6. Other pertinent geotechnical information for the safe development of the site.

I. Certification

1. A signature, certification number, and stamp of a Registered Geologist who is certified in the speciality of Engineering Geology under the provisions of ORS 672.505 to 672.705.

2. A signature, certification number, and stamp of a Professional Engineer, registered in the State of Oregon as provided by ORS 672.002 to 672.325, who by training, education and experience is qualified in the practice of geotechnical or soils engineering practices.