LA s rehearsal. for the big one

Transcription

1 DISASTER RESPONSE LA s rehearsal for the big one The Los Angeles Department of Water and Power fully restored service within five days of a destructive, 6.8-magnitude earthquake. Larry McReynolds and Robert L. Simmons A Although the 6.8-magnitude Northridge earthquake in 1994 was not the big one Californians fear, it caused as much damage to the San Fernando Valley as would be expected from the big one which, experts say, will have a magnitude of 8.0 or higher. This extensive damage occurred because the epicenter was in a large population center, and the quake caused record ground accelerations. The devastation tested the preparedness of the Los Angeles Department of Water and Power. Extensive damage to the water system left 500,000 people without water or fire protection, but water trucks supplied citizens at various locations while repair crews worked around the clock. Full service was restored within five days to 99 percent of customers. t 4:31 a.m. on Jan. 17, 1994 (a national holiday), the Los Angeles, Calif., sky was lit for a few moments by blue white flashes from arcing electrical circuits. Then the city went black, as the Northridge earthquake devastated an area greater than 100 sq mi in the San Fernando Valley. The entire city of Los Angeles, an area of more than 450 sq mi, experienced an immediate and total power failure that would not be completely restored until three days later. The city s aqueducts and the heart of its water distribution system were ruptured, leaving more than half a million people without water or fire protection. The 6.8-magnitude Northridge earthquake that rolled through the valley caused record ground accelerations and uplifted ground masses by 15 in. or more. Crews from the Los Angeles Department of Water and Power (LADWP) and other assisting utilities worked around the clock to repair more than 1,000 breaks and leaks on pipes ranging from 4 to 96 in. in diameter. By January 21, water was restored to 99 percent of the customers, and by January 23, only MAY

2 The Northridge quake caused compression in LADWP s Rinaldi trunk line, causing it to buckle. public health in various parts of Los Angeles. An assessment of damage to the Los Angeles Aqueduct Filtration Plant in Sylmar, the remote chlorination treatment facilities, and major storage tanks was essential to determine water safety. This assessment was finished within 12 hours of the earthquake. As a result, and after chlorine residuals were evaluated and the state s Office of Drinking Water was consulted, the boil-water requirement for roughly half of Los Angeles was lifted the evening of January 17. small local areas were still without water. This phenomenal restoration effort is the subject of this article. From the onset at 4:31 a.m. it was obvious this earthquake was major and had probably extensively damaged water system facilities. The Water Emergency Coordination Center was activated according to the Emergency Response Plan, requiring the immediate presence of water system managers and support staff. Similarly, according to plan, field operations and construction personnel responded from their homes and began their preassigned duties of surveying damage and shutting down damaged facilities. These events occurred with little or no communication; most telephone and radio facilities were inoperative during the first few hours. First things first One of the highest priorities for LADWP after an earthquake is to survey the dams of five major water reservoirs located within Los Angeles. Caretakers who live at these reservoirs inspected the dams within minutes of the earthquake and reported by radio to the Central Supervisory Control Center for the water system that the dams apparently sustained no damage. Engineers responsible for dam safety also reported to the sites to begin a more thorough inspection and to monitor seepage levels from drains within these dams. Other operating personnel began surveying for damage at the city s 68 pump booster stations, 95 smaller reservoirs and tanks, and more than 200 pressureregulating stations. Another important precaution to protect public health was to issue a boilwater notice for the entire city of Los Angeles within 3 hours of the earthquake. This decision was made because of the magnitude of the shaking, the interruption of chlorination to the major open reservoir supplying the city, and the extended period of time that would be required to reliably assess the risk to Emergency response plan automatically triggered The Emergency Response Plan (ERP) was designed to be simple and easily understood. The plan s activities were triggered automatically based on the magnitude of the earthquake. Recognizing that normal communication systems could be unreliable during the initial few hours, every employee who could be involved in earthquake repair work had been given a copy of that portion of the ERP that provided instructions on when and how to respond. The plan provides employees with clear instructions that are based on the magnitude and location of the earthquake as reported by radio and television news. If the earthquake is severe enough to disrupt radio and television, all employees are to report to work, and specific employees are designated to begin inspection activities. For small earthquakes, only sensitive facilities are inspected; for large earthquakes, both surveillance and repair personnel respond. These employees are trained to carry out inspection and repair activities independently if telephones and radios are inoperable. Field command center established. Because the LADWP serves a 450-sq-mi area, it is divided into five geographic regions, each of which has a water construction and operating yard. The number of construction, operation, and maintenance personnel reporting to each yard varies from 75 to 150. It is highly unlikely that a severe earthquake would damage more than one or two of these facilities because of the distance separating them. Therefore, the ERP assumes that a field command center can be established at the yard that Roof girders inside the Beverly Glen tank collapsed. Four of LADWP s steel tanks had to be removed from service for repairs. 66 JOURNAL AWWA

3 The Northridge quake caused more than 1,000 breaks and leaks on pipes and knocked three tanks out of service. MWDSC California Aqueduct Supply Second LA Aqueduct First LA Aqueduct MWDSC Filtration Plant Van Norman Pumping Station MWDSC Line Granada High Tank De soto Ave. LA - 33 (MWDSC) Roscoe Northridge Earthquake Epicenter Zelzah Tank MWDSC Line Topanga Tank Blvd. Vanowen St. Beverly Glen Pumping Station has not suffered significant damage itself yet is nearest the most heavily damaged areas. In the case of the Northridge earthquake, the West Valley yard which was just 3 mi from the epicenter functioned as the field command center. The ERP instructs all employees to go to their normal reporting locations, if possible. Therefore, the LADWP automatically had significant numbers of operation and maintenance personnel deployed throughout the city. Once the magnitude of the damage to the distribution system became more clear, crews from other district yards were assigned to the West Valley yard to aid in the repair efforts. Mutualaid crews from neighboring utilities also reported to this location. Beverly Glen Tank Coldwater Canyon Tank Maclay Reservoir LA Filtration Plant Van Norman Complex LA Reservoir Bypass Reservoir Van Norman Complex Additional Damage High Speed Channel Bypass (Low Speed) Channel LA - 25 (MWDSC) LA - 35T (MWDSC) Powerplant Tailrace VNPS I Discharge Pipe VNPS II Discharge Pipe N Located in the LADWP headquarters building, the Water Emergency Coordination Center (WECC) is the designated command center for management personnel during an earthquake. This facility and the West Valley yard became the command centers from which major operations were directed. System complexity complicates restoration effort The restoration effort facing the LADWP was difficult because the earthquake s epicenter was so close to many water system facilities and because of the immense size and complexity of Los Angeles water distribution system. The Los Angeles water system supplies 3.6 million people and covers an area of 469 sq mi with a range of elevations from sea level to 2,400 ft. To serve the wide range of elevations, the city s distribution system is divided into 118 pressure zones. These service zones are supplied by 101 reservoirs, more than 200 regulator stations, and 70 pump stations. The principal sources of water supply for Los Angeles are the two 338-mi-long Los Angeles aqueducts, which import water from the Owens Valley and Mono Basin in the Eastern Sierra Nevada. A significant additional source of supply is wholesale water purchased from the Metropolitan Water District of Southern California (MWDSC). MWDSC obtains supplies from the Colorado River Aqueduct and the California Aqueduct (State Water Project). MWDSC provides water to the San Fernando Valley from its West Branch extension of the California Aqueduct. The MWDSC supply is available through several connections that provide either treated or untreated water. Fifteen MAY

4 There were 25 breaks or leaks on the major trunk lines at or near the Van Norman Complex. These lines transport water from the 10,000-acre-ft Los Angeles Reservoir. percent of Los Angeles water supply is obtained from 84 local wells with a production capacity of 440 cfs. A significant factor in the restoration of water to the majority of customers so quickly was the system s redundancy. In most areas of Los Angeles, it is usually possible to supply an area by several supply facilities. In many cases, even though the normal distribution flow pattern was interrupted, customers were provided water from other pipes or pump stations. Although some of this redundancy has not yet been reinstated, LADWP customers do not perceive any problems. Damage heavy near epicenter Aqueducts and trunk lines ruptured. The epicenter of the earthquake and its aftershocks was only 10 mi from Newhall Pass and the Van Norman Complex, the heart of Los Angeles s water system. Through the Newhall Pass come the two Los Angeles aqueducts and the West Branch supply from the California Aqueduct. On January 17, all three of the aqueducts supplies were ruptured. The Van Norman Complex, an area of more than 1,000 acres, contains the 10,000 acre-ft Los Angeles Reservoir. This reservoir feeds seven trunk lines that supply the city. The Los Angeles Reservoir is designed to provide about two weeks emergency supply for the San Fernando Valley if Los Angeles aqueducts are ruptured by an earthquake. Also contained in the complex are the Los Angeles Aqueduct Filtration Plant (LAAFP) and a 300-cfs pump station that boosts water to the mountains on the east, north, and west sides of the San Fernando Valley. In addition, the city s three largest connections to MWDSC are located in this complex. Most of the 25 breaks or leaks on major trunk lines were at or near the Van Norman Complex (see map on page 67). Four of the LADWP s steel tanks were severely damaged and removed from service. One had to be demolished, and it took several months to repair the other three tanks. There were about 1,000 small main leaks. The net result was that 17 of the water system s 118 service zones were knocked out, severing the water supply of roughly one third of the population of the San Fernando Valley and the Santa Monica Mountains. Filtration plant loses inflow. The LAAFP treats up to 600 mgd of water from the Los Angeles aqueducts and water from the two raw-water MWDSC connections. The plant combines ozone for predisinfection with rapid sand filtration. Chlorine is applied at the end of the treatment process to provide free chlorine residual in the distribution system. This plant received relatively modest damage, although it was immediately affected by a power failure and was without power for 4 hours until the standby generator could be put in service. During that time, the inflow dropped to zero because of damage to the Los Angeles aqueducts. Complete power from the grid was restored 11 hours after the earthquake. If water had been available, the LAAFP could have resumed treatment of 300 mgd (the capacity of half the plant) the same day as the earthquake. As it turned out, treatment resumed on January 20 with chlorine used as pretreatment in place of ozone, which was not restored for nearly two months. Emergency center directs restoration LADWP initially established restoration goals as follows: (1) restore water service to the most people as quickly as possible, (2) lift the boil-water notice as soon as possible, (3) do not interrupt water service to an area once supply has been returned, and (4) do not degrade water quality in an area once the boil-water notice has been lifted. The WECC was the heart of the restoration planning. The WECC was created to help coordinate the major decisions and activities that have to be undertaken after a major disaster. During such an event, management personnel convene in this large room in order to receive updates and to discuss strategy. The WECC room has several citywide distribution maps, emergency telephone lines, television monitors, charts used to log events and activities, and other necessary emergency-related equipment. All damage reports are received in this room and analyzed for overall effect on customers. Restoration of water service focused on activities that restored water to the most people in the shortest period of time. The whole western and southern parts of the San Fernando Valley were without water because the three city trunk lines that supply these areas were ruptured in many places. 68 JOURNAL AWWA

5 Although MWDSC has a large trunk line in this area, it could only supply a small quantity of water and only to the lower elevations because this line is supplied by the West Branch supply from the California Aqueduct, which was also ruptured. MWDSC was able to get this supply back in service by the morning of January 20, allowing LADWP to provide water to about 250,000 of the people who were without water in the West Valley area. Another 150,000 people in the West Valley were at elevations too high to be supplied from this MWDSC supply. About 20 fire department truck pumpers were used to pump across fire hydrants located along system boundaries to supply about 70 percent of these people. After five days of using fire department truck pumpers, the trunk lines supplying this area were repaired, and normal service was restored. Repairs of the distribution system and less critical trunk lines and damaged tanks continued for months. However, systemwide water service was fully restored nine days after the earthquake. Water-quality precautions taken The first citywide boil-water notice was issued the morning of Jan. 17, This initial notice enabled LADWP to return many trunk lines and storage tanks to service as soon as they were repaired, thereby rapidly restoring domestic water service and fire protection to those areas affected by the earthquake. The final announcement rescinding all boil-water notices was issued the morning of Jan. 29, During these The epicenter of the earthquake and its aftershocks was only 10 mi from Newhall Pass and the Van Norman Complex, the heart of Los Angeles s water system. 12 days, the notices were lifted sequentially in seven areas as water pressure was restored and sampling indicated the water in that area was safe. The California Department of Health Services (DHS) provided the criteria for lifting boil-water notices. These were (1) a tight distribution system (i.e., pressurized and having normal leaks), (2) chlorine residuals of 2 mg/l, and (3) two consecutive negative coliform bacterial tests. Before the boil-water notice was lifted in an area, intensive sampling was conducted for several days in a row. Monitoring results were given to the DHS, and its approval was obtained before boil-water notices were lifted. It was a major challenge to accurately communicate to the media and customers the boundaries of the boil-water areas. Los Angeles uses free chlorine at its filtration plant and at all disinfection stations. Following the quake, chlorine doses were increased to 3 mg/l. In addition, the city has several connections with the local wholesale supplier, MWDSC. The disinfectant MWDSC normally uses is chloramine. Within 8 hours of the earthquake, arrangements had been made with MWDSC to switch to free chlorine at the two MWDSC treatment plants that could deliver water to the quake-affected areas. This arrangement allowed Los Angeles to take water from connections with MWDSC and ensured there would be no disinfectantcompatibility problems. Because of the superior disinfectant performance of chlorine at high dosage rates, no regrowth was detected. MWDSC also boosted the chlorine dose to 3 mg/l at the treatment plants serving the affected areas. The increased chlorine dosage allowed the distribution system to meet all bacterial standards. Trucks transport potable water On January 18, about 10 rented and city-owned water trucks began a water-trucking operation to supply potable water to locations throughout the city. Water trucks were also donated by the US Army Corps of Engineers, US Army National Guard, and MWDSC. Additional trucks were contracted for on an as-needed basis to provide support. At the height of the operation, 72 trucks were being dispatched and were providing more than 10,000 gal of water each day. Thirty-six employees (excluding truck drivers) were involved in the 13-day operation, which provided continuous service from 7:00 a.m. to midnight at published locations. They included most high schools and large parks in the San Fernando Valley and were limited to about 10 locations on any one day. However, in response to other requests from the Red Cross, the California Office of Emergency Services, City Emergency Operations Center, private customers, and others, more than 50 additional sites were served throughout the operation. Neighboring utilities offer aid Offers of help, primarily from neighboring utilities in Southern California but also from northern California and other states, were overwhelming. The greatest difficulty was organizing the repair efforts so that these crews could be used effectively. Many offers had to be turned down because much of the damage to the trunk lines and the distribution system could only be identified after the initial damage had been repaired and water was available in the system. In the end, 21 crews from neighboring utilities were utilized. In addition, four crews came from East Bay Municipal Utility District in the Oakland area and worked almost a week. In all, 25 crews from 11 neighboring utilities combined with more MAY

6 than 600 LADWP water system employees to complete the Herculean task. Successes and areas needing improvement noted As tragic as these types of disasters are, they offer a valuable opportunity to review the adequacy of preplanning and to highlight areas needing improvement. Following is a brief summary of what went well and what needed improvement. Planning pays off. In many instances, preliminary planning paid off for the LADWP when the Northridge earthquake put workers to the test. Employees reported to work in accordance with predetermined instructions and training. They surveyed facilities to determine damage, shut down damaged facilities, and began repair efforts. This took place in most cases with few communications for the first 8 hours following the quake. Field and central command centers established to coordinate and direct efforts functioned well. However, it took about 8 hours to develop a sketchy picture of the damage. Mutual aid offered from other California water utilities was overwhelming. Redundancy in water supply facilities and the use of portable pumps and fire department pumpers allowed many damaged facilities to be bypassed and water service to be restored within four or five days to the vast majority of the damaged area. Facilities designed using earthquake-design criteria developed since the 1971 Sylmar earthquake functioned well and experienced little damage. It was decided to internally inspect about 37,000 ft of large-diameter pipelines rather than taking the approach of repairing a leak, filling the pipeline, and draining the pipeline again when another leak became apparent. By using this approach, workers found breaks that were not apparent from the surface and could repair them right away rather than waiting until water was restored to that section to discover leaks. Challenges identified. Unanticipated problems hindered managers and field crews as the restoration effort proceeded. A citywide boil-water notice had not been anticipated, and few preparations had been made to provide drinking water throughout Los Angeles. Food and water sources usually used by construction employees were not available, and the limited quantities stored for emergencies were inadequate. There had been inadequate preparation to house employees who could not commute because of damaged freeways. Several employees had commuting times of several hours each way because of damaged freeways. These employees were either housed temporarily at the LADWP construction yards or stayed with fellow employees or friends who lived close to work. One important trunk line that is located in poor foundation material was heavily damaged in the 1971 Sylmar earthquake. This trunk line was repaired in 1971, but it was not relocated onto good foundation. In the 1994 Northridge earthquake, it again suffered damage almost identical to that experienced in Communication was the most immediate problem. With the loss of power, most telephone communication was lost, as was much of LADWP s 900- megahertz voice radio communication. Radios provided limited communications, but their range and capacity were greatly limited because all transmission from vehicle to vehicle was without the benefit of booster antennas or central computer routing of transmission. The water system s emergency response preparedness did not foresee the extent to which trucked water would be demanded, nor was it foreseen that the need for trucked water would last as long as it did. The bulk of this operation was assembled on short notice, and with better foresight it might have been coordinated more quickly. LADWP s water system had conducted several exercises simulating a major earthquake. These exercises were designed to test both field and WECC procedures. The field procedures generally worked well, as was discussed previously. However, the WECC did not function as efficiently during the earthquake as it did during the exercises primarily because the practice exercises lasted 2 hours, whereas the real thing lasted 10 days! Although managers can be expected to remain in the WECC for a couple of hours during an exercise, that expectation was unrealistic during the actual emergency, which lasted more than a week. It is impossible to predict when an earthquake will occur, but it is absolutely certain that earthquakes will continue to plague California. LADWP s most recent experience has enabled emergency planners for the water system to refine strategies that work and formulate new tactics in response to problems not previously identified. The ongoing planning effort is in keeping with the agency s philosophy that all utilities have a responsibility to the public to be prepared. About the authors: Larry Mc- Reynolds is engineer in charge of operations for the Los Angeles Department of Water and Power (LADWP), POB 111, Los Angeles, CA He has directed operations and construction for LADWP s water system for seven years and was in charge of restoration efforts after the Northridge earthquake. McReynolds has a BS degree in civil engineering from the University of Missouri, Columbia, and an MS in civil engineering from the University of Southern California in Los Angeles. He has 30 years experience in all phases of water system operation, design, and management, and his work has been published previously in JOUR- NAL AWWA. Robert L. Simmons is LADWP s assistant engineer in charge of operations. 70 JOURNAL AWWA