[jacket3ree]

I think the most succinct analysis I've seen is that public firefighting infrastructure is designed to put out isolated house fires, not combat an extreme natural disaster sweeping into a highly populated suburb.

This is exactly right. I've designed municipal water systems for nearly 40 years and we do not design them with massive wildfires in mind. Those are natural disaster, Force Majure, Act of God scenarios (even if god is an electric company) and no one can afford water systems capable of fighting that. I've done systems across California, on Maui, and Santa Rose after the Coffee Fire that melted underground distribution piping. 

Community, mutual, and municipal water systems are organized into pressure zones. Hilly terrain including the most devastated locations in LA will need many pressure zones. Potable water for domestic consumption, irrigation, fire fighting, and emergencies is fed into each pressure zone by gravity or pumping and stored within that zone (tanks) or fed through pressure regulators to a lower zone or by booster pumps into a higher zone. Each zone is supplied its maximum day demand from a wholesale source like SFPUC or Valley Water or groundwater. Demand varies across the day and those spikes in demand (peak hour) must come from water stored within the pressure zone or stored water brought into the pressure zone from another pressure zone. 

Fire flow demands are on top of that peak hour demand. We design the pumping, storage, and distribution systems (pipes and hydrants) to deliver fire flows during a peak hour so that we do not have an unacceptable pressure loss (no less than 20 psi residual during a fire anywhere in the system) that can lead to back siphoning contaminants into the system and leading to health problems. The working assumption is one fire at a time within the pressure zone. If the zone is entirely residential, that's a single house. A code fire demand might be 1,500 gallons per minute (gpm) for two hours. That equates to 180,000 gallons that need to be stored on top of storage for peak hour demand and other emergencies. Plus you never want to completely drain a tank because they leads to lower residual pressure in the system. If the pressure zone is mixed use with commercial and industrial development, the fire demand might be 4,000 gpm for four hours or 960,000 gallons of storage for fire.  I think the UFC and ISO charts top out at 8,000 gpm for 4 hours and there are allowances for sprinklered buildings, etc.

I have done lots and lots of 200,000 gallon tanks and 2 million gallon tanks. The largest ever for me was 6 million gallons.  Why not just play it safe and build mega tanks everywhere?  Cost, impact, and problems with water quality. Usually fires are fought with potable water. The same water we all drink and use daily. With a mega tank and no fires, that water stagnates in the tank and we start having problems with circulation, water quality, and again health. The chlorine residual, if chlorine is used for disinfection, just dissipates over the long time that water sits there waiting for a fire. Occasionally we have designed dual systems for that very reason, but again, expensive.

So, take thousands of homes multiplied by 1,500 gallons per minute and you run out of water pretty quickly. It is no one's fault. Certainly not the Delta smelt's. Wildland fire fighting takes over with tankers, lake water, ocean water, whatever they can do.  Unfortunately though, removing fuel in urban areas isn't like the wildland, where swaths of trees can be chain sawed. That was driven home in Santa Rosa when even Highway 101 proved to be an inadequate fire break.

I worked with an attorney today and the subject came up. There will be time for recriminations and responsibility. He showed me a phone picture of his friend in Altadena who had snapped a picture of the transmission lines sparking in the high winds. She (his friend) evacuated and is now famous on the internet for the picture. Her home was spared (for now) by the direction of the wind. This is awful and hopefully we can all help our southern neighbors. Searching for early blame doesn't help, in my opinion.

This came up on something I was watching making dinner. (CNN maybe?) 'How can the hydrants run dry? Incompetence!' I had to turn it off.

[jacket3ree]

I think the most succinct analysis I've seen is that public firefighting infrastructure is designed to put out isolated house fires, not combat an extreme natural disaster sweeping into a highly populated suburb.

This is exactly right. I've designed municipal water systems for nearly 40 years and we do not design them with massive wildfires in mind. Those are natural disaster, Force Majure, Act of God scenarios (even if god is an electric company) and no one can afford water systems capable of fighting that. I've done systems across California, on Maui, and Santa Rose after the Coffee Fire that melted underground distribution piping. 

Community, mutual, and municipal water systems are organized into pressure zones. Hilly terrain including the most devastated locations in LA will need many pressure zones. Potable water for domestic consumption, irrigation, fire fighting, and emergencies is fed into each pressure zone by gravity or pumping and stored within that zone (tanks) or fed through pressure regulators to a lower zone or by booster pumps into a higher zone. Each zone is supplied its maximum day demand from a wholesale source like SFPUC or Valley Water or groundwater. Demand varies across the day and those spikes in demand (peak hour) must come from water stored within the pressure zone or stored water brought into the pressure zone from another pressure zone. 

Fire flow demands are on top of that peak hour demand. We design the pumping, storage, and distribution systems (pipes and hydrants) to deliver fire flows during a peak hour so that we do not have an unacceptable pressure loss (no less than 20 psi residual during a fire anywhere in the system) that can lead to back siphoning contaminants into the system and leading to health problems. The working assumption is one fire at a time within the pressure zone. If the zone is entirely residential, that's a single house. A code fire demand might be 1,500 gallons per minute (gpm) for two hours. That equates to 180,000 gallons that need to be stored on top of storage for peak hour demand and other emergencies. Plus you never want to completely drain a tank because they leads to lower residual pressure in the system. If the pressure zone is mixed use with commercial and industrial development, the fire demand might be 4,000 gpm for four hours or 960,000 gallons of storage for fire.  I think the UFC and ISO charts top out at 8,000 gpm for 4 hours and there are allowances for sprinklered buildings, etc.

I have done lots and lots of 200,000 gallon tanks and 2 million gallon tanks. The largest ever for me was 6 million gallons.  Why not just play it safe and build mega tanks everywhere?  Cost, impact, and problems with water quality. Usually fires are fought with potable water. The same water we all drink and use daily. With a mega tank and no fires, that water stagnates in the tank and we start having problems with circulation, water quality, and again health. The chlorine residual, if chlorine is used for disinfection, just dissipates over the long time that water sits there waiting for a fire. Occasionally we have designed dual systems for that very reason, but again, expensive.

So, take thousands of homes multiplied by 1,500 gallons per minute and you run out of water pretty quickly. It is no one's fault. Certainly not the Delta smelt's. Wildland fire fighting takes over with tankers, lake water, ocean water, whatever they can do.  Unfortunately though, removing fuel in urban areas isn't like the wildland, where swaths of trees can be chain sawed. That was driven home in Santa Rosa when even Highway 101 proved to be an inadequate fire break.

I worked with an attorney today and the subject came up. There will be time for recriminations and responsibility. He showed me a phone picture of his friend in Altadena who had snapped a picture of the transmission lines sparking in the high winds. She (his friend) evacuated and is now famous on the internet for the picture. Her home was spared (for now) by the direction of the wind. This is awful and hopefully we can all help our southern neighbors. Searching for early blame doesn't help, in my opinion.

This came up on something I was watching making dinner. (CNN maybe?) 'How can the hydrants run dry? Incompetence!' I had to turn it off.