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***Tuesday, November 8, 2011***
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Topic: "Subsurface Characterization at LADWP Headworks Reservoir Site, City of Los Angeles"

Speaker: David L. Perry,
Amec Engineering Consulting

Location: Cisco's Restaurant
925 South Westlake Boulevard
Westlake Village, CA

Date/Time: Tuesday, November 8, 2011
6:00 p.m.-Social Hour; 7:00 p.m.-Dinner; 7:45 p.m.-Presentation

Reservations: Please e-mail Dave Perry at
or call (323) 889-5326

The proposed Headworks Reservoir is part of the Silver Lake Reservoir Complex Replacement Project, which will be constructed on approximately 12 acres within the Headworks Spreading Grounds, located in the southeastern San Fernando Valley area of Los Angeles, California. The Headworks Reservoir will consist of two structurally-separate reinforced concrete water storage structures surrounded by earthen embankments, with combined capacity of about 110 million gallons. The geologic units underlying the project site consists of artificial fill, recent to Holocene age alluvial deposits, and variably weathered quartz diorite / granodiorite that is cut by intrusive mafic dikes. This presentation provides a description of geotechnical exploration and testing methods for site characterization. Subsurface exploration consisted of rotary wash and continuous dry-core borings, Becker Penetration Test (BPT) soundings, sonic core borings, ground-water monitoring wells, close-range terrestrial photogrammetry and logging of deep test trenches, large-diameter ring density tests, suspension P-S wave velocity testing, and spectral analysis of surface waves (SASW).

The advantages of supplementing rotary-wash borings with samples collected at 3- foot depth intervals with continuous dry core and sonic core borings will be presented. Due to the presence of thick sandy gravel lenses in the alluvial deposits beneath the site, BPT soundings in addition to conventional SPT testing was performed for liquefaction evaluation. In-situ density testing was conducted at 3-foot depth intervals in a 20-foot deep test trench using large (3- and 6-foot) diameter rings where gravel and cobbles were encountered. SASW and suspension logging was performed to characterize the shear wave velocity of the alluvial deposits and bedrock. An excellent correlation in shear wave velocity profiles was observed between several of the SASW surveys and suspension logging. Laboratory testing consisted of two and three-point direct shear tests, consolidation tests, triaxial unconsolidated-undrained tests, Atterberg limits tests, and over 80 grain size analyses. The laboratory test program was needed to characterize the alluvial deposits for liquefaction evaluation and soil-structure interaction analyses.
Speaker Biography:
Mr. Perry is a Senior Engineering Geologist at AMEC Environment and Infrastructure in Los Angeles. He has 26 years of experience on geologic investigations for design and construction monitoring of infrastructure projects throughout California. A majority of these projects have been engineering geology studies for dams, tunnels, water storage reservoirs, water and sewer pipelines, highway and subway-rail structures, educational institutions, commercial facilities, sanitary landfills, and land development. He has performed numerous fault-rupture-hazard studies in southern California and Washington. Major infrastructure projects include the light rail/subway tunnels for the Los Angeles Metropolitan Transit Authority and the Emergency Water Storage Reservoir Project) for the San Diego County Water Authority.

Mr. Perry is the current treasurer of the AEG Southern California section. He received his Bachelors degree in Geological Sciences from the University of California at Santa Barbara and completed graduate studies in geology at Cal State Los Angeles.