The Confined Disposal Facility (CDF) is located within the northeast portion of Naval Air Station (NAS) North Island. The CDF received approximately 78,000 cubic yards of dredged sediments that were hydraulically placed behind the rock dike and densified in-place by deep dynamic compaction and vibro-replacement techniques. The CDF was created to dispose of and isolate environmentally impacted dredge fill that could not be disposed with the rest of the material dredged to create the aircraft carrier docking area. The CDF features a clean sand cap, approximately 10 feet thick, a 50-foot clean-sand buffer zone between the designated waste and the interior dike face, and a 25- to 50-foot rock dike that abuts San Diego Bay. The sand cap was surfaced with asphalt and concrete to control infiltration and was subsequently developed with roads and temporary and permanent structures. The area was developed contemporaneously with the adjacent aircraft carrier wharf. The reinforced concrete wharf is supported on numerous rows of pre-stressed concrete piles bearing in the Bay Point Formation. Five inclinometers were as part of the wharf construction to monitor potential displacement of the pile structure.
Geosyntec's Scope of Services
Geosyntec was contracted to perform a visual site survey and examine data from inclinometer monitoring at the site. The purpose of the visual site survey was to document surface features within and along the perimeter of the CDF that might indicate settlement or movement, which could be indicators of movement within the CDF. The purpose of the inclinometer monitoring was to estimate the cumulative lateral displacement of the concrete pile structure supporting the CDF. During the course of our surveys, we identified new areas indicating possible movement and performed monitoring of five existing inclinometers within the pile foundations. Once we had completed the field portion of our efforts, we reduced the field data, conducted engineering analyses of the results, and prepared a report. Previous monitoring efforts by others produced data not suitable for analyses. Geosyntec has performed several years of annual monitoring at this site and has developed a clearer understanding of the site conditions compared to previous settlement or movement assessments.
Geosyntec establish a new datum at the site for future monitoring activities after evaluating the quality of data collected by others. Geosyntec was able to plan and execute the field investigations on an active carrier wharf while the carrier was in dock.