The Project.
Amongst the historic structures, restaurants, and shopping of Old Town is the Mormon Battalion Visitor Center. Activated in 1846, the battalion is the only religiously based unit in United States military history. The recent remodel of the visitors center required extensive geologic study due to its location within the active Rose Canyon fault.
Client:
The Church of Jesus Christ of Latter-Day Saints
Location:
San Diego, CA
Services:
- Geotechnical
- Geotechnical Testing
- Special Inspection
- Materials Testing
Project Fact:
Old Town San Diego State Historic Park includes original adobe buildings dating back to the early 1800s.
The Leighton Solution.
Leighton was chosen for the project because of our experience in the completion of fault hazard evaluations within urban locations, our efficient schedule, and competitive cost. Also of significance was our previous experience and understanding of the review process within the Land Development Review Section of the City of San Diego Development Services Department.
The active Rose Canyon Fault Zone prompted the necessity of a fault hazard evaluation. In addition, Leighton provided a design level geotechnical investigation and continued with the project through review services. Given Leighton’s outstanding service record on the project we continued to the conclusion of the project which included materials testing and inspection services.
We originally proposed to excavate two trenches across the eastern portions of the property boundary. However, following the observation of several faults, we performed an additional three trenches for a total of five exploration trenches across the site totaling approximately 265 lineal feet.
In particular, one exploration trench reached a maximum depth of 22 feet utilizing vertical speed shoring. The presence of existing sewer and storm drain utilities bisecting the subject site from east to west complicated the fault trenching. Our analysis of the trenching data using a combination of soils morphology and radiometric Carbon 14 dates indicated that the site was transected by several active faults.
As a result of our findings, we provided setback recommendations for the proposed project. Following several meetings with City of San Diego geology personnel and the client, the project was redesigned as a remodel to the existing structure with small building additions of less than 500 square feet founded on strengthened mat slabs to resist potential ground movement associated with seismic shaking.
