M E M 0 R A N D U M
DATE: November 21, 1989
TO: Tom Elzey, PUC General Manager
FROM: Art Jensen, Acting General Manager
RE: Report to the Board of Supervisors Concerning the Water Supply
At the direction of the Board of Supervisors, Mr. John Taylor, Clerk of the Board, forwarded a request from Supervisor Richard Hongisto for information on certain aspects of the City water supply. Specifically, the request is for information on (1) the safety of the water supply, (2) whether there has been any rupture of the City's sewer system near any collapse or rupture of the water system that could lead to contamination of the water supply, and (3) what steps are being taken or plans being recommended to correct any structural defects and strengthen the water system and sewer system. The nature of the inquiry reflects a concern for the safety of the water supply with respect to the protection of public health. Additional information on other aspects of the reliability of the water supply is included in the last section of this report. As the request for information was made through the Chief Administrative Officer to you and both the Director of Health and the Director of Public Works, I contacted those two departments to discuss their intended responses and to share information on the water system. Each of the departments will respond separately. This memorandum represents the Water Department's response.
The ongoing water quality of the City's water supply has been unaffected by the earthquake of October 17, 1989. The flow of treated water to the City was uninterrupted. A power failure on the peninsula affected the San Andreas filter plant operation for approximately one hour and forty minutes; however, the reservoir of treated water, located at the plant, provided continuity of service to northern San Mateo County and the City. City reservoirs were also unaffected and continued to function.
The City-wide power outages affected service to eight hilltop neighborhoods which are supplied by hydropneumatic pumping stations, rather than storage tanks or reservoirs. These neighborhoods of three to twelve city blocks, did not have full service until power was restored. The length of time that these stations were without power varied from 4 to 15 hours, depending upon their location. The possibility of any water quality-related impacts during those periods is minimal. The Water Department's capital improvement program for FY 1990-91 already contains a project for modifying these stations so that small portable generators can be easily connected in the event of power failures. The pump motors are small, on the order of two horsepower, and this form of standby power is ideal. In a multiple disaster, such as a simultaneous power outage and fire, water for fire fighting is readily available from gravity-fed water mains in adjacent areas and pumped by fire trucks to the affected area.
On the morning of October 18, personnel from the Water Quality Division (WQD) began intensive water quality sampling throughout the peninsula and in the City to cover all normal sampling stations, all San Francisco Department of Public Health stations, areas around major main breaks and all major public buildings, primarily the hospitals. Tests were performed to check for a positive chlorine residual, indicating that the water has a disinfecting capability, and for the presence of coliform bacteria which if found is an indicator of possible contamination. Chlorine residual results can be obtained quickly. Laboratory analyses for coliform bacteria require 20 to 24 hours. In general, the water quality samples demonstrated that the quality of water throughout the delivery and distribution system was potable.
The greatest damage to the water system consisted of approximately 150 main breaks and service line leaks. Of the 102 main breaks, over 90 percent were in the Marina, Islais Creek and South of Market infirm areas. The significant loss of service occurred in the Marina area, where 67 main breaks and numerous service line leaks caused loss of pressure.
Immediately following the earthquake, City Distribution Division (CDD) personnel responded to news reports of a fire at the Marina. They attempted to increase water pressure in the domestic water system by opening valves to let water flow into the mains in the Marina area from higher pressure zones. This action resulted in only a marginal increase in fire fighting pressures due to the extensive local damage to the distribution system. The Fire Department was ultimately forced to rely on the Phoenix fire boat to fight the fire in the Marina. Following the fire, Water Department crews began isolating and repairing main breaks in the Marina, as they were elsewhere in the City.
The routine process of locating and repairing leaks was followed to affect repairs after the earthquake. Leaks are only visible when the mains are under pressure so that water can be seen to be leaking and/or the area of low pressure can be isolated. Once a leak is located, the section of main is valved out of the system, the area around the leak is excavated, the remaining pressure in the pipe is released, and repairs are made. When the repair is completed, valves are opened, pressure returns to normal, the line is flushed through a hydrant, and service is restored. These procedures mitigate the potential for contamination.
In areas of the City where leaks were small and isolated, and where it was not necessary to take the water mains out of service, the mains were left under pressure so that service and fire fighting capability were not disrupted. These leaks were repaired in order of severity when crews were available. Normal repair procedures were followed. Under these circumstances the lines are not depressurized except for the period of repair, following which the lines are flushed before service is restored. Conditions in the Marina area prompted the precautionary measures described below.
Given the degree of destruction in the Marina (the short block of Rico had 5 main breaks and 8 service leaks) it was necessary to pressurize and depressurize sections of pipe repeatedly until all leaks could be located and repaired. Initially. all service connections were closed to prevent loss of water pressure and damage to residences due to possible plumbing leaks internal to the buildings. CDD crews started by bringing perimeter mains back into service for fire protection. This work began the night of October 17 and continued until all service was restored to the Marina on October 21.
In the Marina area, precautionary measures were taken regarding the use of the water for potable purposes because (1) unlike typical main break situations, soil conditions causing breaks in the water mains were suspected of also causing damage to the sewer system, (2) also unlike typical main break situations, the mains needed to be repeatedly taken in and out of service in order to locate all of the leaks, and (3) people in the area would necessarily experience fluctuating pressures until the repair process was completed. Until repairs were complete it was not possible to flush the mains and ensure the potability of the water. Therefore, the Water Department, in conjunction with the City Health Department, and after having discussed the matter with the California Department of Health Services (CDHS), released a water quality advisory message to the residents of the Marina area. The advisory instructed the Marina residents that they should not drink or cook with the water until further notice, that if they had water service the water could be used for flushing toilets and washing, and that they could call either of two phone numbers provided for additional information on water quality or service. The Water Department also stationed personnel at the utility information trailer at the Marina and at the FEMA office at the Presidio to answer questions and assist people with service restoration.
On October 23, six days after the earthquake, service was restored to most of the Marina area and water quality test results indicated that water in that area was safe to drink. An advisory to that effect was issued with the concurrence of the CDHS. On the following day, when additional main breaks were discovered in isolated areas of the Marina, a limited water quality advisory was distributed to only the affected addresses. This advisory stated that because of newly discovered main breaks, those residents were instructed not to drink tap water without boiling it for two days after their water service had been restored. This advisory was issued as a precautionary measure, even though tests of the water indicated the presence of a chlorine residual and no evidence of contamination. The WQD manager reviewed these actions with the CDHS Northern California Supervising Sanitary Engineer. He noted that the "boil water" advisory was actually unnecessary, given the high level of chlorine residual maintained throughout the event, but concurred that the City's actions were certainly prudent, conservative and with the public's welfare in mind.
Several measures are being taken to strengthen the water system to minimize the likelihood of similar damage or to minimize the potential extent of damage. Many prudent actions have been and continue to be elements of business as historically conducted by the Water Department. Other steps are being actively pursued or are now under active consideration.
Actions Being Taken. Actions currently being taken to secure the system against damage are both preventive and corrective in nature. First, cast iron water mains are no longer being installed. New mains of up to 16 inches in diameter are made of ductile iron, and connections between pipe segments are now made with flexible joints that permit limited amounts of movement. Under a long-term capital program, older cast iron mains are being replaced with ductile iron pipe. In the Marina area, approximately 8,000 feet of cast iron mains will be selectively replaced as a result of the earthquake. These lines would have been scheduled for replacement at a future time, but work will be done now to mitigate the possibility of continued failures of these pipes. Distribution system pipes above 16 inches in diameter are made of welded steel, which is also less prone to damage than cast iron. The earthquake caused no damage to pipes greater than 16 inches in diameter.
Second, sewer lines are typically buried deeper than water pipelines, and water lines, unlike most sewer lines, are pressurized. Both features work to minimize the potential for cross-contamination. As noted by Richard Cunningham, the Department of Public Works Superintendent of Street and Sewer Repair, "The initial lack of water service in the Marina made it difficult to determine the extent of damage to sewers in that area. No sanitary or rain water was flowing through the sewers." This condition further mitigated the possibility of cross contamination at the Marina.
Third, the water distribution system is constructed with valves at intersections and interconnections so that problem areas can be isolated from the balance of the system. This feature serves to minimize the size of any area affected by a main break or service leak. Additionally, valves are located between pressure zones (different elevations in the City are served by different water distribution zones to limit the range of pressures in any one area). These valves can be and are opened to maintain pressure in lower zones whenever pressures decrease during repairs to major water mains and to ensure that the Fire Department has sufficient pressure to fight major fires. As a matter of routine, the Water Department responds to every fire of two alarms or greater, and operates these valves if and when necessary to support fire fighting efforts.
Fourth, the Water Department conducts water quality sampling and analyses on a routine basis as well as in the event of a potential cross-connection or contamination problem.
Work currently planned or in progress will result in additional recommendations for improving the integrity of the delivery and distribution systems. Specific examples are cited below.
(1) The possible installation of pressure sensing instrumentation at key locations within the distribution system will be evaluated so that more data is readily available for locating the cause of losses in pressure.
(2) The CDD will investigate the infirm areas of the City, those most likely to be affected by earthquakes, to see whether major mains, if damaged, can be removed from service without loss of transmission capacity to other parts of the same pressure zone. Recommendations for redundant pipeline capacity or other safeguards will be sought.
(3) With respect to the delivery facilities supplying water to Alameda, Santa Clara, and San Mateo Counties, as well as the City and County of San Francisco, the Water Department has several capital projects directed at improving the reliability of the system. A study has been funded to evaluate the existing pipeline construction in the vicinity of known earthquake faults and to develop recommendations and criteria for more reliable pipeline designs in such areas. Funds have also been approved for initial studies of a second tunnel through the East Bay hills. The existing single tunnel represents a point of vulnerability, should an earthquake damage connections to the tunnel or some other event require that the tunnel be taken out of service. The existing tunnel between the Sunol Valley and Irvington cannot now be removed from service for inspections or repairs, given current demands upon the system. Storage and treatment facilities on the peninsula will be capable of maintaining service to northern San Mateo County and the City and County of San Francisco even if pipelines across the South Bay are disrupted.
(4) The water treatment plants and the City distribution facilities are subject to established preventive maintenance programs. These programs are updated, expanded and improved over time. In contrast, a formal preventive maintenance program for the large pipelines and other major facilities of the delivery system is only now being developed. A preventive maintenance program for the large valves on these pipelines is being implemented through the current FY 1989/90 budget. Staffing and other requirements to support a preventive maintenance program for the other elements of the system have been proposed. Information is now being refined to support a request for funding.
(5) This year the Water Department, Hetch Hetchy Water and Power, and the Utilities Engineering Bureau formed a committee to begin a systematic review, evaluation and ongoing monitoring of all dams, reservoirs, and other key facilities. The need for this program results in part from changes in the role being played by the State of California Department of Safety of Dams (DSOD). The DSOD formerly was the State agency that received facilities monitoring data, conducted analyses and evaluations, and issued recommendations for improvements. The DSOD now requires agencies to submit completed analyses and evaluations for review.
(6) Key Water Department facilities have been and continue to be fitted with standby power equipment. Additional such facilities are being designed for the San Andreas Water Treatment Plant at this time. As mentioned previously, standby power capabilities are planned for the small hydropneumatic pump stations in the City distribution system.
(7) Existing City reservoirs have a capacity of over 400 million gallons, equivalent to over 4 days of supply at average levels of consumption. The Department is currently conducting a study of City reservoirs to determine how additional storage capacity may benefit the distribution system in terms of maintaining suitable pressures and providing operational and emergency storage.
(8) Finally, the value of the Department's annual emergency preparedness exercises and planning efforts was demonstrated during and following this earthquake. Nonetheless, the experience of the earthquake on October 17 highlighted several areas where improvements can be made with respect to emergency communications, prepared checklists for emergency response and recovery functions, and availability of emergency response equipment packages for water quality sampling. Recommendations from staff have been solicited and will be reviewed and implemented or incorporated into the Department's budget, as appropriate. A consistent conclusion from both the management and staff of the Water Department is the need to have some level of staff resources dedicated solely to the duties of emergency preparedness planning and the ongoing maintenance of procedures, checklists, communications, utility mutual aide agreements and other elements of a preparedness program necessary for a water utility of the size and geographical extent of the San Francisco Water Department. Members of the Water Department hold positions on the Disaster Preparedness Committee of the American Water Works Association or have formal training in event response planning and management. To devote these individuals to this effort may require that their existing duties be reassigned. The impacts of such reassignments or alternative means for reaching the same objective have not yet been evaluated and will require additional work.