TITLE
Recommendation to receive and file the report, “Elevation Changes in the City of Long Beach, November 2006 through April 2007.” (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 November 2006 through April 2007. 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 Central City, Alamitos Bay, Naples, Harbor District areas including the Pier A West steamflood area and northern edge of Pier S adjacent to the Cerritos Channel, and majority of the offshore oil island areas. The Civic Center and the western portion of the offshore island area showed a 0.05 foot (0.6 inches) elevation loss for the period. There is no immediate reason for concern as this area had minor elevation changes due to ongoing waterflood adjustments corresponding to oil field development programs. LBGO is mitigating the loss in the area by increasing and realigning water injection as a temporary drilling program on Island Grissom came to an end.
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 rebound...
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