Pinnacle Hills

 

The Pinnacle Hills residential subdivision is located at the base of the San Gabriel Mountains in the northern part of Fontana, California. The proposed development will consist of 122 single-family residential lots and related infrastructure to be constructed on 35 acres of land. The northern part of the property is located within a State of California Alquist-Priolo Earthquake Fault Zone for fault rupture hazards. To aid in initial planning of the development, RMA Group performed a geologic fault investigation, a preliminary geotechnical investigation, and soil infiltration testing for percolation of storm water runoff.

The geologic fault investigation included review of prior fault investigations and regional references, geologic mapping, review and interpretation of aerial photographs, excavation and logging of four fault trenches, and preparation of a written report. Cal/OSHA, Underground Service Alert, and the San Bernardino County Geologist were notified prior to our excavation of trenches. Each of these trenches was 12 to 20 feet deep, totaling 770 feet of excavation. The subsurface investigation spanned the entire Alquist-Priolo Zone within the proposed development area. The trenches were logged, digitally photographed, surveyed, and examined by the County Geologist. A fault setback zone was recommended through a portion of the property to mitigate potential surface fault rupture hazards.

The geotechnical investigation included excavation, logging, and sampling of 10 exploratory trenches, laboratory testing of soil samples, and preparation of a written report presenting grading, foundation, and other engineering recommendations for site design. The soil infiltration testing was performed using a Double-Ring Infiltrometer in accordance with ASTM Test Method D3385.