§ 24.35.190. Geologic hazards—Additional requirements for geologic assessments in seismic hazard areas.

In addition to the requirements in TCC 24.35.130, the following shall be required for geologic assessments in seismic hazard areas, as specified:

A.

The geological assessment for a seismic hazard area shall be prepared by a team that includes a geotechnical professional who is licensed as an engineering geologist specializing in seismic hazards with a minimum of four years of relevant professional employment, as determined by the director.

B.

The geological assessment shall be submitted in the form of a geotechnical letter when the geotechnical professional finds that no seismic hazard areas exist within the development proposal site. A geotechnical letter shall, at a minimum, include the following:

1.

The letter shall be labeled identifying the submittal as a "seismic hazard geotechnical letter" and shall include all mandatory elements listed in TCC 24.35.130.

2.

The geotechnical letter shall be prepared under the responsible charge of a geotechnical professional(s) and be signed, sealed and dated by the geotechnical professional(s).

C.

The geological assessment shall be submitted in the form of a geotechnical evaluation when the geotechnical professional finds that a seismic hazard area exists but is located outside the proposed project area. A geotechnical evaluation shall, at a minimum, include the following:

1.

The cover letter for the document shall clearly identify the submittal as a "seismic hazard geotechnical evaluation" and shall include all mandatory elements listed in TCC 24.35.130.

2.

A site plan, as defined in TCC 24.35.130(H)(9).

3.

Verification that a seismic hazard exists on the property, but is located outside the proposed project site.

4.

A description of the geology of the site, conclusions and recommendations regarding the effect of geologic conditions on the proposed development, and opinions and recommendations for compensating for the seismic hazards present.

5.

The geotechnical evaluation shall be prepared under the responsible charge of a geotechnical professional(s) and be signed, sealed and dated by the geotechnical professional(s).

D.

The geological assessment shall be submitted in the form of a geotechnical report when the geotechnical professional finds that a seismic hazard area exists within the proposed project area. A geotechnical report shall, at a minimum, include the following:

1.

The cover letter for the document shall clearly identify the submittal as a "seismic hazard geotechnical report" and shall include all mandatory elements listed in TCC 24.35.130.

2.

A site plan, as defined in TCC 24.35.130(H)(9). The site plan shall also include any set-backs from the defined locations of the seismic hazard area, as determined by the geotechnical professional(s), to protect any portion of the proposed development activity from damage caused by liquefaction-induced ground displacement.

3.

Verification that the proposed project site falls within a seismic hazard area.

4.

The field investigation shall include subsurface characterization using conventional geotechnical borings and standard penetration testing (SPT) or using cone penetration testing (CPT).

5.

The geotechnical report shall include a detailed assessment of the liquefaction and/or dynamic settlement hazard based on an analysis of all available SPT or CPT data using state-of-the-practice methodologies, such as provided by Youd and Idriss (1997) or subsequent technical publications. The methodology used in the analysis shall be documented, and all results of intermediate and final calculations and results, including factors of safety, shall be included.

6.

The geotechnical report shall contain an assessment of the potential for large lateral spreads or flow failures, bearing failures, settlement, limited lateral displacement, and floatation of buried facilities. The methodologies used must be, at a minimum, state-of-the-practice, and where applicable, should employ more than one method of analysis. All results of intermediate and final calculations and conclusions regarding the potential and severity of the possible liquefaction and/or dynamic settlement induced failure modes shall be presented.

7.

Alternative mitigation measures including structural and foundation design options and/or soil improvement techniques shall be evaluated and compared for their effectiveness in reaching the level of performance specified in the report. Final designs and specifications and plans for structural and/or foundation design shall be included if applicable. Effectiveness of soil improvement techniques shall be specified in terms of post-treatment densification or strength improvement as measured by appropriate subsurface investigation and testing. The extent of post-treatment verification testing shall be provided on a site map at the same scale as required by the approval authority.

8.

A description of the geology of the site, conclusions and recommendations regarding the effect of geologic conditions on the proposed development, and opinions and recommendations for compensating for the seismic hazards present.

9.

The geotechnical report shall be prepared under the responsible charge of a geotechnical professional(s) and be signed, sealed and dated by the geotechnical professional(s).

(Ord. No. 14773, § 3(Att. B), 7-24-2012)