(1)
When a site proposed for development or alteration is located or may be located within a geologically hazardous area or its buffer, or will negatively impact a geologically hazardous area, the administrator shall have the authority to require the submittal of a geotechnical report.
(2)
A geotechnical report is an evaluation of the geologic characteristics of the subject property and adjacent areas. A geotechnical report shall include a field investigation and may include an analysis of historical aerial photographs, review of public records and documentation, and interviews with adjacent property owners.
(3)
Submittal requirements will vary depending on the type of project and the type of hazard mitigations that are proposed. The administrator may waive parts of the submittal requirements if he/she determines that they are not applicable to the proposed activity.
(4)
Submittal Requirements. The following submittals may be required for a geotechnical report:
(a)
A site plan that shows:
(i)
The site boundary lines.
(ii)
Existing physical features of the site including buildings, fences, and other structures, roads, parking lots, utilities, water bodies, etc.
(iii)
A detailed depiction of the proposed development including features such as lot location (for land divisions); utility location (well, septic, drainfield, etc.); parking and access location; the location of any proposed building(s); and the limits of grading and vegetation removal.
(iv)
An identification of critical areas and buffers within 300 feet of the site and an estimate of the existing acreage for each. The assessment of off-site critical areas shall be based on available information and shall not require access to off-site properties.
(b)
Site Geology Information.
(i)
Topographic contours at two-foot intervals or as specified by the responsible official.
(ii)
Subsurface data including the exploration method, location of soil borings, borings, logs, soil and rock stratigraphy, and ground water levels including seasonal changes.
(iii)
The location of landslides, or down-slope soil movement, faults, and geologic contacts on the subject property and adjacent properties.
(iv)
A site history that describes any prior grading, soil instability and/or slope failure.
(v)
A description of the site vulnerability to seismic events.
(c)
Geotechnical Information and Plan Requirements.
(i)
A slope stability study and opinion of slope stability on the subject property and adjacent properties.
(ii)
A grading plan, including road profiles.
(iii)
Structural foundation requirements and estimated foundation settlements.
(iv)
Soil compaction criteria.
(v)
Allowable soil-bearing pressure for foundations, minimum footing widths, piling recommendations for foundations, and design pressure for retaining walls.
(vi)
Laboratory data and soil index properties for soil samples.
(vii)
Suitability for fill.
(viii)
Lateral earth pressures.
(ix)
A description of erosion vulnerability and an erosion control plan, including measures to reduce the impacts of erosion on neighboring critical areas.
(x)
An evaluation of proposed surface and subsurface drainage, and a drainage control plan.
(xi)
Building limitations.
(xii)
A vegetation management and restoration plan or other means to maintain long-term stability of the hazardous areas and their buffers.
(d)
A site evaluation that describes the suitability of the site to accommodate the proposed activity.
(e)
Such additional information describing existing physical features of the site and the surrounding area as required by the responsible official to complete a review of the project.
(Ord. 1284 § 4, 2018; Ord. 1370 (Exh. B), 2025)