2039 N Victoria Drive #2 - Plan - Laserfiche WebLink

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24-8009 Page 5 GEOTECHNICAL FINDINGS Regional Geologic Setting The subject site is located within the south-western corner of the Orange 7.5-Minute Quadrangle, Orange County, California. According to the Geologic Map of Orange County, California (Morton and Miller, 1981), the subject site is underlain by alluvium. Figure 2 presents the Regional Geologic Map. Groundwater Subsurface water was not encountered in our borings to the explored depth of 15.5 feet. Based on our review of available historical groundwater information (CDMG, 1997) regional groundwater is mapped at greater than 40 feet beneath the subject site. Static groundwater is not anticipated to impact the proposed improvement. Figure 3 presents the Historic High Groundwater Map. Earth Units Based on our subsurface investigation, the location of the proposed ADU (B-1 and B-2) is underlain by fill generally consisting of greyish brown silty sand with clay to a depth of approximately 2 to more than 7 feet, below which lies native alluvium consisting of sandy silt to silty sand to a depth of 15.5 feet, the maximum depth explored. In the area of the proposed spa (B-3), the native alluvium consisting of sandy silt to silty sand was observed at the surface and continued to a depth of approximately 10.5 feet. Detailed descriptions of the earth units encountered in our borings are presented in the log of borings. Faulting and Seismicity The subject site, like the rest of Southern California, is located within a seismically active region as a result of being located near the active margin between the North American and Pacific tectonic plates. The principal source of seismic activity is movement along the northwest- trending regional faults such as the San Andreas, San Jacinto and Elsinore fault zones. These fault systems produce approximately 5 to 35 millimeters per year of slip between the plates. We consider the most significant geologic hazard to be the potential for moderate to strong seismic shaking that is likely to occur at the subject site. The subject site is located in the highly seismic Southern California region within the influence of several faults that are considered to be Holocene-active or pre-Holocene faults. A Holocene-active fault is defined by the State of California as a fault that has exhibited surface displacement within the Holocene time (about the last 11,700 years). A pre-Holocene fault is defined by the State as a fault whose history of past movement is older than 11,700 years ago and does not meet the criteria for a Holocene-active fault. These Holocene-active and pre-Holocene faults are capable of producing potentially damaging seismic shaking at the site. It is anticipated that the subject site will periodically experience ground acceleration as the result of small to moderate magnitude earthquakes. Other active faults without surface expression (blind faults) or other potentially active seismic sources that are not currently zoned and may be capable of generating an earthquake are known to be present under in the region. 2039 N Victoria Drive #24/28/2025