TITLE
Recommendation to receive and file the report, “Elevation Changes in the City of Long Beach, May 2006 to November 2006.” (Citywide)
DISCUSSION
The City of Long Beach (City), 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 May 2006 to November 2006. The LBGO survey includes the following areas: Civic Center, Central City, Alamitos Bay, Naples, Harbor District, and an offshore area encompassing the four offshore oil islands.
The results of the six-month survey show that elevations were stable in the Civic Center, Central City, Alamitos Bay, Naples, and offshore areas. Harbor District elevations were stable except in two areas. An elevation gain of up to 0.072 feet (0.86 inches) was observed on Pier D and an elevation loss of up to 0.069 feet (0.83 inches) occurred on the northern edge of Pier S adjacent to the Cerritos Channel. There is no immediate reason for concern as these two areas had minor elevation changes due to ongoing waterflood adjustments corresponding to oil field development programs. Additionally, the area located below Pier A, which had shown persistent elevation losses in the past, has slowed significantly.
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. Repressuring operations will result in the rebound of the affected areas.
Surface elevations in a rebounded area can be expected to fluctua...
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