Nat Hazards (2006) 39:343–351 DOI 10.1007/s11069-006-0032-8 ORIGINAL PAPER
Mitigation of seismic and meteorological hazards to marine oil terminals and other pier and wharf structures in California M. L. Eskijian
Received: 26 August 2003 / Accepted: 8 June 2005 Springer Science+Business Media B.V. 2006
Abstract For the past 12 years, the California State Lands Commission has been involved in the operational monitoring, structural inspection and requalification of 45 marine oil terminals along California’s coast, which have an average age of about 50 years and plans to keep these structures in service for another 20–40 years. Having seen the port and harbor damage from the 1995 Kobe and 1999 Izmit earthquakes, the potential for a major disruption in petroleum product production is real. Losing the daily gasoline production for a period of weeks or months as a result of a moderate earthquake or tsunami could significantly affect the economic well being of California and much of the western United States. In addition, a major oil spill resulting from such an event could cause the closure of a major port for days or even weeks. Such a closure would further affect the economy of California and the United States. Most of these facilities were designed to primitive seismic standards and for vessels much smaller than those currently moored. Many of these structures have never had a comprehensive underwater inspection. Wind and current forces on large tank ships can cause mooring lines to break or cause serious structural damage to supporting structures. In California, non-regulatory progress has been made in the following areas: (i) underwater and above water inspections or audits; (ii) mooring analyses and structural/environmental monitoring in high velocity current areas; (iii) seismic analyses and structural rehabilitation with updated seismic hazard data; and (iv) accelerometers on marine structures. In addition, standards have been developed and are proposed to be regulatory by early 2004. The new standards include most of the items listed above, but also extend into many other areas. Along with the proposed regulations come many issues that raise economic and political questions. These issues are not unique to marine oil terminals and are applicable to other pier and wharf structures in harbors. Keywords
Marine structures Æ Seismic requalification Æ Mooring analyses
M. L. Eskijian (&) Marine Facilities Division, California State Lands Commission, 200 Oceangate, Suite 900, Long Beach, CA 90802, USA e-mail:
[email protected]
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Abbreviations ASCE American Society of Civil Engineers CSLC California State Lands Commission CSMIP California Strong Motion Instrumentation Program (California) DWT Deadweight tons FEMA Federal Emergency Management Agency (USA) MFD Marine Facilities Division of the California State Lands Commission MOTEMS Marine Oil Terminal Engineering and Maintenance Standards NFESC Naval Facilities Engineering Service Center (USA) OCIMF Oil Companies International Marine Forum P&ID’S Piping and Instrumentation Diagrams PIANC Permanent International Association of Navigation Congresses PRC Public Resource Code (California) USCG United States Coast Guard
Introduction In order to protect public health, safety and the environment, the California legislature passed the Lempert-Keene-Seastrand Oil Spill Prevention and Response Act of 1990. The Act defines specific tasks for the California State Lands Commission (‘‘the commission’’), in part stating: ‘‘The commission shall adopt rules, regulations, guidelines and commission leasing policies for reviewing the location, type, character, performance standards, size and operation of all existing and proposed marine terminals within the state, whether or not on lands leased from the commission, and all other marine facilities on land under lease from the commission to minimize the possibilities of a discharge of oil ...’’ (California Public Resources Code (PRC) Section 8755 (a)). ‘‘The commission shall periodically review and accordingly modify its rules, regulations, guidelines and commission leasing policies to ensure that all operators of marine terminals within the state and marine facilities under the commission’s jurisdiction always provide the best achievable protection of the public health and safety, and the environment ...’’ (PRC Section 8756). In order to develop ‘‘performance standards’’ for marine oil terminals, the California State Lands Commission (CSLC) requested funding through a hazard mitigation grant program of the US Federal Emergency Management Administration (FEMA) as a result of the 1994 Northridge earthquake. Along with additional funding from the CSLC, this effort is now complete and the Marine Oil Terminal Engineering and Maintenance Standards (MOTEMS) are now available. The prime consultant for the development of these standards was a joint venture of Han-Padron Associates of Long Beach, California and Ben C. Gerwick, Inc. of San Francisco, California. The Marine Oil Terminal Engineering and Maintenance Standards (MOTEMS 2003) provide a set of comprehensive engineering standards for the analysis, design and inspection/maintenance of marine oil terminals. These new standards define criteria for both new and existing facilities and are ‘‘performance-based’’ in terms of structural analysis and design.
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Additional contributions to the MOTEMS was provided through a ‘‘Cooperative Research and Development Agreement’’ with the NFESC. The NFESC has provided extensive input to the seismic, mooring and structural inspection sections (Ferritto et al. 1999). Inclusive in the NFESC effort was the work of Professor Nigel Priestley of the University of California at San Diego, who provided the detailed structural performance criteria for seismic loading at marine oil terminals. Professor Costas Synolakis of the civil engineering department of the University of Southern California directed the tsunami risk assessment (Synolakis 2002) based on the seismic information developed by Lawrence Livermore National Laboratory (Savy and Foxall 2003).
Non-regulatory progress Voluntarily, some of these marine oil terminal operators have already performed extensive underwater inspections of their facilities. As part of the testing of our proposed regulations, we have assisted a number of marine oil terminal operators, in these comprehensive inspections or ‘‘audits’’. These terminals are now involved in the rehabilitation process. The CSLC has developed a draft audit manual to provide guidance in the implementation of the MOTEMS and in documenting structural and mechanical/electrical deficiencies at marine oil terminals. Since the inception of the Marine Facilities Division (MFD) of the CSLC in late 1990, we have been concerned about the mooring of vessels at terminals under our jurisdiction. Most of these facilities were designed and built long ago to handle smaller vessels (e.g., T2 tankers). Over time, larger tankers have replaced the older ones, creating potential mooring problems. Larger vessels have greater sail areas resulting in greater wind loads; larger hull areas below the waterline result in potentially higher current loads. In addition, the aging structures with older design fender types may not be adequate for expected higher impact loads. Due to several recent, near-catastrophic incidents in the Carquinez Strait of Northern California, a ‘‘High Velocity Current’’ working group, including terminal operators, has formulated specific guidelines for the mooring of tank vessels in these areas of high currents. These guidelines require operators to install current meters at the facilities to accurately determine current magnitude and direction at various depths. Currents at these facilities are commonly greater than 2.5 knots. Previously, operators would merely simulate or extrapolate current/tide information from distant recording sites in the area. The new site-specific data is used to perform a mooring analysis using the largest vessel at maximum draft that may call at that location. In addition, four operators have independently installed load cells to monitor mooring line tension. The use of these devices assists in the evaluation of high or low loads which could indicate a potential sudden failure of the mooring line(s) or large vessel movement (surge or sway). Historically, the US Coast Guard (USCG) has approved operations manuals for marine oil terminals; manuals must also be approved by the MFD. The MFD requirements are more stringent that those of the USCG and specify the largest vessel that can be moored at a facility. In order to moor a tank vessel larger than that specified in the manual, the terminal must submit a mooring assessment and proposed change to the operations manual. The MFD then reviews the engineering assessment and either approves or disapproves the change in vessel size as a result of the mooring analysis and structural assessment. Inhouse, we use the ‘‘Optimoor’’ computer program from TensionTechnology to analyze both offshore and fixed onshore moorings.
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Seismic analysis and structural rehabilitation have been completed for one major marine oil terminal using the criteria and methodology of the MOTEMS. This terminal is over 50 years old, constructed of concrete piles and a reinforced concrete deck. In addition, the structure has had some severe structural damage in some areas. After completing a thorough above- and below-water inspection, the operator performed a structural analysis using a site-specific seismic hazard assessment with a new response spectrum. This facility has shown a ‘‘beta test’’ of our procedures and criteria as being reasonable. As a member of California’s ‘‘Lifeline Subcommittee’’ of the Strong Motion Instrumentation Program (CSMIP), the author has convinced one major oil terminal and three port authorities to install accelerometers on marine structures. The Port of Oakland has recently installed accelerometers on both new and rehabilitated wharves. The ports of Los Angeles and Long Beach are in the planning stages for placing accelerometers on their wharves and piers. The San Rafael Bridge, adjacent to the one marine oil terminal, has been fitted with ground motion accelerometers on or near bedrock. So, with the bedrock input motion and the in-structure response on this adjacent marine oil terminal, this scenario gives us a perfect opportunity to verify the seismic analysis and compare with the actual structural response. Following an earthquake, the acceleration records will be available on the Internet within 10–20 min (http://www.consrv.ca.gov/cgs/smip/index.htm). Having the in-structure response will also assist the owner/operator and the regulator in the determination of whether or not an underwater inspection is required, or whether the facility should shut-down until the damage has been repaired. As an additional benefit to having accelerometers, it is hoped that these devices will date/time stamp any major impact loads from vessels.
The Marine Oil Terminal Engineering and Maintenance Standards (MOTEMS) To comply with the MOTEMS audit and inspection requirements, the terminals are also conforming to the new America Society of Civil Engineering (ASCE) Standard for underwater inspection (Childs et al. 2001). The MOTEMS requires a 100% Level I underwater ‘‘swim-by’’ inspection. Depending upon the material (concrete, steel and timber), the results of the previous underwater inspection and the marine environment (benign or aggressive), these audits are to be performed at least once every 6 years. At the conclusion of the above and underwater inspection of the structure, the engineer/divers are able to determine the gross structural capacity and evaluate ‘‘fitness-for-purpose’’. These inspections serve many purposes in both documenting the current condition of the structure, as well as providing a baseline so that future damage, whether it be from an earthquake, vessel impact or tsunami, can be compared to the structure prior to the event. The MOTEMS also provides guidelines for inspection following an earthquake or other major damage-causing event (e.g., vessel impact). Post-event ratings are assigned and recommendations made that could limit or stop facility operations until corrected. As a result of the structural audit or inspection required by the MOTEMS, structural deficiencies are recorded; the facility operator is informed and required to provide a schedule of when the rehabilitation will be completed. Deficiencies will be monitored by MFD personnel. The audit or inspection also includes a structural evaluation from the waterline up and an evaluation of the fire suppression, mechanical and electrical systems of the terminal, including an evaluation of mooring equipment such as hooks, bitts and bollards.
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Nat Hazards (2006) 39:343–351 Table 1 Existing facility classification
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Classification level
Exposed oil (bbl)
Transfers per year/facility
Vessel size (DWT · 1000)
High Moderate Low
‡1,200
