2002 W Alton Ave - Soils Report - Laserfiche WebLink

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Project No. D-3885-06 Christ Our Savior Catholic Parish The basin floor is of very low relief and represents a very large alluvial outwash plain. The Santa Ana River lies 2400-feet to the southeast of the site and drains a very extensive watershed region reaching all the way to the San Bemardino Mountains. This generally intennittently flowing river has been responsible for transporting and depositing the widely distributed alluvium in the Orange County portion of the Coastal Plain. Dams have been constructed across the river up gradient for flood control purposes and the river channel has been improved opposite the site. The site area, regardless of the improvements, still lies within a 100-year flood zone and is capable of inundation depending on storm run-olf and storage capacity. The coast lies about 7.8-miles to the southwest of the site and the nearest uplands slopes (El Modeno Hills) are located 6 to 7 miles to the northeast. Site Geologic Conditions The site area is nearly flat and has not undergone any extensive previous grading. Drainage in the site area is controlled by paved surfaces and storm drains. The gradient across the site region is down-to-the-southwest at about l5-feet per mile. No active faults have been mapped near the site, although two deeply buried inferred faults have been mapped about 2000 feet to the southwest. These are considered confined to older alluvium and or Pliocene age bedrock deposits. They are not active, not having ruptured in Holocene time. Surface Water and Site Surface Drainage Surface water on this site is the likely result of precipitation or surface run-off from surrounding sites. Overall site drainage is in a south and southwestem direction. Provisions for surface drainage will need to be accounted for by the project civil engineer. 4 I I I n I I I I I t I I n I n r I I I