Water Supply – San Francisco Style
Arguably the most important element of a community’s fire protection is its water supplies available for firefighting. This article will highlight the San Francisco Fire Department’s many water supply options that, it is hoped, will assist other agencies in developing their own.
Over 7,000 domestic low-pressure potable hydrants serve as the backbone to the Fire Department's water supply arsenal. These wet-barrel hydrants are painted white and have two three-inch male National Standard Threaded gated outlets. The bonnets of the hydrants might be painted blue, indicating non-potable, or green, indicating a below-ground cistern is nearby.
The distribution of the low-pressure system hydrants is three such hydrants located on the corners of street intersections in the high-value downtown districts, with one or more intermediate hydrants between intersections, depending on the length of the block and the hazards of the district. In closely built-up residential districts, there are usually two hydrants on corners of street intersections and in areas of less hazard, one hydrant.
Most of the hydrants are connected to the Water Department pipeline by a 5 inch internal diameter branch pipe. Newer installations are 6-inch branch pipes.
Water Department mains from which these hydrants take supply are generally 6 to 16 inches in diameter and can be larger in some locations.
Pressure available at these hydrants range from 80 to 120 psi in the downtown high value area of the city to 40 to 100 psi in outlying residential areas.
High Pressure Hydrant System
The Auxiliary High Pressure Hydrant system is a water distribution system that the San Francisco Fire Department owns and operates. Firefighters simply call it the High Pressure System. There are two zones to this system, the upper zone and lower zone. The 750,000-gallon Jones Street Tank, which is set at the 360-foot elevation, is located in the lower zone and has hydrants with static pressures up to 160 psi. The 500,000-gallon Ashbury Tank, at 494 feet elevation, and the 10,500,000-gallon Twin Peaks Reservoir, at 758 feet elevation, serves the upper zone.
Ashbury Tank supply and pressure can be opened and added to the Jones Street lower zone supply to produce 214-psi pressures in hydrants in this lower downtown zone. When Twin Peaks valves are opened and added to the Jones Street supply, static pressures can top 328-psi in the lower zone.
High Pressure Hydrants are substantial, extra-heavy cast iron, 10-inch internal diameter barrel hydrants that weigh approximately 1,500 pounds and have three, 3½-inch male threaded outlets. The reason for the 3½-inch outlets is to prevent anyone from directly connecting hose to these outlets.
Fire Department procedure when using these hydrants is to always connect a Gleason Valve onto one or more of the three outlets for pressure discharge control. This brass, 97-pound pressure reducing valve, which was patented in 1926, brings pressure down to a manageable level. In effect, each High Pressure Hydrant, with Gleason Valves attached, become a pump from which to get high volumes of water at high pressures.
This High Pressure Hydrant system was developed at the time of horse-drawn steam fire engines. It was meant to be a “stand alone” water supply system and can still be used as such. A lower zone hydrant has the ability to flow 12,000 gpm.
Fire Department procedure calls for High Pressure Hydrants to be used as the first means of water supply when such hydrants are available for ladderpipes and other master stream devices. The supply goes directly to the master stream, not through a fire department pumper.
Should the two tanks or the 10,500,000-gallon reservoir be in danger of being depleted of water supply, the High Pressure System has the ability to put one or both of the two saltwater pump stations on line. Pump Station One is located in the basement of the current Fire Department Headquarters building at 2nd and Townsend St., and Pump Station Two, located at the foot of Van Ness Ave., below Fort Mason. They both have the ability to take supply from the San Francisco Bay and pump into the 135 miles of High Pressure Hydrant distribution mains.
Each of the pump stations is connected to the Bay with a below-ground 5-foot diameter concrete tunnel for pump station suction supply. Each pump station has four-stage turbine pumps. Each is operated by a 16-cylinder diesel engine and is capable of a 3,000-gpm discharge at 300-psi pump pressure for a total capacity of 10,000 gallons per minute.
Each station has a 15,000-gallon diesel fuel capacity to run the station for approximately 40 hours of continuous operation.
In addition to the saltwater pump stations the High Pressure distribution system can be supplied by fireboat pumps through any of five manifold inlets located on the city’s Bay waterfront. These manifolds are equipped with ten 3-inch swiveled female inlets arranged in a horizontal pattern.
The fireboat Phoenix has the ability to pump 9,600 gpm at 150 psi for a continuous period of 34 hours without need for replenishment of fuel supply. The fireboat Guardian can pump up to 24,000 gpm at 150 psi. Each fireboat has the ability to supply 3-inch supply lines off the boat at any onshore location they are able reach to lead hose lines off to land-based companies for supply. The fireboat Phoenix has 14 such discharge connections and the fireboat Guardian has 24 three-inch discharge connections.
Thirty-four Pierside Suction Connections are located along the waterfront from the Saint Francis Yacht Club on the north side of the city’s Bay front to Third Street, past Army Street, in the south portion of the Bay.
These six-inch NST female swivel connections are at pier edge or curbside to the waterfront for easy connection with one 10-foot hard-suction length to an engine’s suction inlet for drafting.
The Port Fire Marshal has also designated “fire lane” pierside drafting locations that will be readily available to engines. This would require two, 10-foot hard-suction lengths to account for changes in tide. San Francisco Fire Department standard operating procedure mandates quarterly drafting drills of all engine companies.
Moving inland toward Golden Gate Park, the Fire Department has taken advantage of one of the park's bigger manmade lakes, Stow Lake. On the south side of Fulton Street from 22nd Avenue to 48th Avenue, the Department has installed 27 “Fulton Street Emergency Hydrants.” Each hydrant is equipped with one, 6-inch female swiveled outlet from which to take supply.
These are nonpotable hydrants taking supply from the park's lakes. For this reason, the barrels are painted green, the bonnets blue, and the outlet cap white. Blue is a San Francisco Fire Department hydrant color meaning brackish or nonpotable.
There are 172 cisterns strategically located throughout the city so as to provide the Fire Department with a total storage capacity of approximately 11 million gallons of water.
Determination of cistern location is based on two fundamental fire-control considerations. One is where the underground water distribution system is more susceptible to damage by earthquake. The six-lane Van Ness Avenue, running north and south from the San Francisco Bay to Market Street, best describes the other example.
Van Ness Avenue was a stand-and-fight location for firefighters in 1906, the year of the great earthquake. It was here that firefighters fought hard to stop the fire from burning further west. This major thoroughfare is lined with cisterns and high-pressure hydrants that may be called on some day in the future to stop a major conflagration from burning down the city.
The average capacity of a cistern is 75,000 gallons with the smallest being 9,600 gallons, located at Stockton and Vallejo Streets, and the largest being 243,000 gallons, located in front of City Hall at the Civic Center.
Cisterns are designated by manholes with CISTERN SFFD marked on them, and most with a ring of bricks around the manhole cover in the street asphalt. Additionally, the nearest low-pressure hydrant's bonnet is painted green. Engines would utilize normal drafting procedures when using such cisterns. The manhole cover is removed and the engine spotted within 3 feet of the cistern opening, allowing for plenty of space to hook up and drop two lengths of hard-suction for drafting.
In addition to all of the above, the San Francisco Fire Department requires that all pools, reservoirs and roof top tanks over 5,000 gallons be connected to a 3-inch gated discharge outlet if under pressure or a 6-inch suction connection if under low or static pressure.
These emergency supply locations are maintained in an Emergency Water Supply binder, grouped by Battalion District and kept on each engine and in each chief’s vehicle.
Redundancy in water supplies should be the goal of all fire departments in their strategic planning of community fire protection.
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