TITLE
Recommendation to receive and file the report, “Elevation Changes in the City of Long Beach, November 2012 through April 2013.” (Citywide)
DISCUSSION
The City of Long Beach, through the Long Beach Gas and Oil Department (LBGO), supervises oil production and subsidence control operations in the Wilmington Oil Field. LBGO conducts elevation surveys every six months to monitor elevation changes in the oil fields and adjacent city areas. This report focuses on elevation changes that have occurred from November 2012 through April 2013. The LBGO survey includes the following areas: Civic Center, Central City, Alamitos Bay, Naples, Harbor District, and an offshore area encompassing the four oil islands.
The results of the six-month survey show that elevations were stable in the Civic Center, Central City, Alamitos Bay, Naples, and the offshore drilling islands. In the Harbor District, Pier A declined up to 0.08 foot (1.0 inch). A mitigation plan, based on adjustments of oil field operations, has been implemented and the areas will be closely monitored for further action. Piers C, E and H were stable during the past six months, while elevations on Piers D and T rose up to 0.06 foot (0.7 inches). The elevation change is within normal limits and not expected to continue.
The LBGO survey uses a series of benchmarks to determine elevation changes. Studies by the Department's engineers and geologists show that the benchmarks may rise and fall in such a manner as to make a survey either optimistic (slightly up in elevation) or pessimistic (slightly down in elevation). These changes in elevations may be associated with tidal cycles, temperature changes, and/or deep earth tectonic changes or re-pressuring operations. Surface elevations in a rebounded area can be expected to fluctuate under changing water flood conditions.
This matter was reviewed by Deputy City Attorney Richard Anthony and by Budget Management Officer Victoria Bell on August 1, 2013.
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