Worthington State Forest Fire Hose Layout scenario exercise
Worthington State Forest Fire Hose Layout scenario exercise
Limited Aircraft, No UTV or Vehicle Access!
This scenario is an exercise designed around the FireBridge method of determining the needs of resources and equipment based off of the Initial Fire Behavior Nomograms, then using that information to determine the required Apparatus, number of hose lengths including size and number of nozzles etc and then we look at the ability to determine if such equipment or supplies are on hand and if not then what options remain.
The scenario is based upon a similar incident that took place in Feb 2020 in New Jersey in the Worthington State Forest near Dunnfield Creek and Red Dot Trail.
The Fuels are a grass component with some scrub oak and for this exercise Fire Behavior Nomogram Fuel Model 4 is used on the Low Wind side with a 1 & 5mph plots as well with plots on the High Wind side to obtain a wide range of stats for the fires estimated behavior. Below in Figure 1. Is a topographical section view of the Worthington State Forest showing the Dunnfield Crk Parking area and the Red Dot Trail.
Looking at several photos and videos various people of the area have posted online via YouTube and other sources shows the Red Dot trail to be very rough and rocky as well as too narrow for the USE of UTV’s and renders vehicle access nonexistent! Figures 2 & 3 show the Red Dot trail. There is a few pages of explanation as to why we continue to look at the hose lay scenario over aircraft although it will become apparent that hose lines and pumps are seriously problematic for this scenario. Yet this scenario is one that is designed to TAX the aspiring engineer.
The Trail from the parking area at Dunnfield is at a base elevation of approximately 320Ft MSL and the trail begins there and continues for 1.2 miles or 6,336 feet and ends (for our exercise) at an approximate altitude of 1,447 Ft MSL. This alone produces a continuous head pressure requirement of:
1,447 – 320 = 1,127 x .434 = 489.12 Psi.
Flowing water through KK nozzles mandates another 100 PSI is added to bring the total to:
489.12 + 100 = 589.12Psi. Then the flow demand would be necessary. This is where this problem becomes more complex & hose size and diameter more important. In order to determine GROUND resource needs we first need to look at our Fire nomogram for the appropriate fuel model. In this scenario we use Fuel Model 4 Low wind side. Figure 4, on the next page.
This design has several problems with it. One, in order to keep pressures as low as possible, the hose sizes have to be larger than standard 2 ½” hose. Otherwise this would require possibly triple the number of pumps. Another problem is the fact that 4 inch sized appliances are heavy, expensive and cumbersome or impossible to be carrying up a hill. Hence, the reason for a supply line and an attack line.
#’s are used to identify the elements used.
#1, is first obtaining the slope Percent. Since the Worthington SF area is comprised of a slope ranging anywhere from 50% to 100% this would have required over a dozen plots that are simply used to obtain the mid-flame effective wind speed that in turn is used to determine the fires rate of spread, this then tells us the fires HPA or Heat Per Unit that is measured in Btu per Square Foot, and then the Intensity, which, when we obtain when we multiply the HPA x the ROS in Feet per second. We used an average slope of 70%. This can be converted to degrees of slope for those that are not used to picturing % of slope, by taking the slope percentage and dividing by 100 then taking the inverse tangent of that to obtain the degrees. Like so:
Starting at Arrow 1, on the lower left quadrant of the nomogram, we say our first measured wind speed is 2.5mph. At Arrow 1, we would move upward to the 2.5mph line and then move left “straight” across to obtain an approximate Effective Mid-flame value of 5mph. This is the only purpose of this quadrant. The diagonal line that the Red 2 is to the right of, is what is called the “Turn Line” and this will be explained later.
Next at Arrow 3, (Upper left Quadrant) we have to draw our live fuel moisture percentage for those fuel models that have both a live and dead fuel moisture component. Here at the arrow location we arbitrarily chose a 125% Live FUEL moisture content and drew in the line starting from this boxes lower right corner up to the 4% Fine Dead Fuel Moisture line that runs horizontally from Arrow 4 as shown. This is drawn in a more straight line than curved and is called the K line.
At Arrow 4, (Upper Right Quadrant) this dead fuel moisture percentage would be drawn all the way across from the upper right quadrant box with the dead fuel moisture, to the upper left quadrant box at Arrow 3. As can be seen the horizontal line serves as a boundary line for the live fuel moisture components.
Arrows 5, & 7, (Lower Right Quadrant) is showing what a 1mph wind component would indicate if the starting point was from a 4% Dead and 125% (Arrow 4) live fuel moistures starting point, then drawn vertically down to the 1mph line. Upon reaching the 1mph line a “Turn” to the left is made and drawn horizontally until the next box’s diagonal “Turn Line” is reached, and then another “TURN” to the right or upward is made until we reach the 125% live moisture line.
Once our line being drawn upward, touches this 125% moisture line, we again “TURN” to the right and then move horizontally to the right until our line intersects our original vertical line. At this location is our final numbers that we can use for estimating our fires behavior, ROS, HPA and Flame Lengths etc. In other words, this is the set of numbers our Suppression efforts should be based upon and what our water supply needs should be calculated from!
In this case the intersection is at Arrow 7, and is showing that for a 4% dead fuel moisture, our Heat Per Unit Area is approximately 2,700 BTU per Square Foot. Looking to the left we see the Rate of Spread is approximately 7 chains per hour. Back at the intersection of our lines we just drew, we can see the Fire intensity in Btu/s/ft is approx. 300-350. If you were to follow along the curved path to the left you will be able to determine that the Fire flame lengths are approximately 6-7ft in length or height.
Arrow 8 shows the same information only plotted for a 5mph wind speed (Arrow 6). This 4mph increase jumps from a intensity of only 345Btu per foot per second to 3,450 because the Rate of Spread went from 7 chains per hour to 70 chains per hour. 70ch/hr = 4,620 feet per hour, 77 feet per minute, or 1.28 feet per second. This compared to a 1mph wind producing a .128 foot per second spread. This translates into a ROS of 1.5” per second vs 15.3” per second.
If we use the 5mph winds, our final numbers will look like the following:
ROS ≅ 70Ch/hr or 4,620 feet per hour, 77 feet per minute, 1.28 feet per second.
HPA ≅ 2,700 Btu per square foot
Flame lengths ≅ 18 feet
Btu/s/ft ≅ 3,456
This alone does not tell us quite enough information yet, however, we can do a quick determination based upon the Btu/s/ft figure and look at a ground nozzle that can absorb at least this much heat on a per second basis.
A 20Gpm nozzle for the altitude of the particular area in question can absorb approximately 3,139Btu per second. So we will need a little more than 20 Gpm. Computing for 22Gpm (explained later), would yield a heat absorption capacity of 3,469Btu/sec!
Herein lies a deceptive solution. This figure would appear to show that a 1” KK Nozzle can in fact absorb more heat than what is being generated and the problem is solved. What one must not forget is that this is only on a per square foot basis. When you have this Heat per square foot multiplied by ½ mile of the 1.2 mile distance, the problem is then compounded because your nozzles are spread out 100 feet apart. That is a very LARGE gap in between while your flame front is still advancing. We will look at how much area each nozzle can cover later on.
We need to determine the fire line length to obtain the areas Btu/second/foot heat generation so we can determine the total amount of water needed and to then make a determination of what resource(s) is best needed. (Ordinarily, once this is done you have to make a decision if you can get crews and hand lines in the area or if it is going to be an airshow, in this case, it is an exercise in training on deductive processes for resources and materials and then the proper arrangement of those resources).
If the fire line is approx. ½ mile long then 2,640 feet x 1.28 feet x 2,700 will be our intensity. Our fire line intensity is 3,456 Btu/s/ft x the length of 2,640 = 9,123,840 Btu per second. Figuring this another way, the area of the fire is 1.28ft x 2,640 ft = 3,379.2 square feet. Multiply this by the Btu per square foot of 2700 is 3,379.2 x 2,700 = 9,123,840.
Next we need to determine the amount of water required and we first have to determine the Altitude and the temperature water boils at. Using the FireBridge method, which is to construct a mathematical bridge between Fire behavior and Operations or what the fire is doing vs what we need, we can then bring in the right resources. Again, however, this is a training scenario for Hose-lays so we will not dive into FireBridge much for this.
The altitude our fire is at is first determined for the highest point we’ll need water and in this case is 1,450 feet approximately. The obvious need of this is head pressure for pumping operations, however, the second is Boiling Temperature for heat absorption. First take the altitude and divide this figure by 1,000. 1,450 ÷ 1,000 = 1.450 Then multiply this figure by the lapse rate of 1.84 degrees per 1,000 feet and you should obtain a figure of 2.68. Next you take the boiling temperature of water at sea level of 212° degrees and subtract 2.68 from this number to obtain 212° - 2.68 = 209.32° . This is the boiling temperature for the altitude we use.
Next, we have to estimate or determine by thermometer the water temperature we will be using, either from draft or tank or snap tanks. Here we will simply say the water temperature to be about 50 degrees then the Specific BTU absorption capacity per pound of water can be determined. 209.32° – 50° = 159.32 . Every pound of water will absorb 159.32 Btu in raising (absorbing) the temperature from 50 degrees to its boiling temperature of 209 degrees. After this we can absorb another 970.3 Btu per lb of heat in the conversion to steam. A total thermal capacity of each pound of water is now 159.32+970.3 = 1129.62 Btu / lb. 1 Gallon of fresh water will then absorb 8.34 x 1129.62 = 9,421Btu/gallon.
Back to our 9,123,840 Btu/second. If we divide this figure by the 1,129.62 we’ll obtain the number of pounds of water required. 8,076.31 pounds per second is required. Divide this figure by 8.34 to obtain the gallons. 8,076.91lbs/sec ÷ 8.34lbs/gal = 968.45 gallons per second. If we have a 6,300 foot fire line and each nozzle spread out 100 feet apart, then that is 63 nozzles. If we further divide this gallon per second figure by the number of nozzles we have, we would arrive at a figure of 15.372. 15 gallons per second, means that, each nozzle has to flow 922 Gpm. This fire will now have to be broken up into sections for suppression actions as no wildland pump alone can move 968 gallons per second.
Further this tells you that the Hose-lay will have to be a secondary control method of suppression activity and not the primary in Ordinary Operations as the initial Knockdown would have to come from Air Resources “IF” this was to be slowed instantly and time is of the essence.
Understand that 1.28 feet (15 inches) per second is 77 feet per minute. For this area it was stated that the ROS was more akin to 4 feet per minute. This means for a slower Rate of Spread, the winds have to be less.
1MPH wind speed:
If we use the rate of 4 feet per minute, we can determine that this is both .067 feet per second OR working backwards, we can determine the ROS in chains per hour to be 3.6. Leaving the HPA the same at 2,700Btu per square foot, and then re computing the Btu/s/ft / Area we obtain:
2,700 x .067 x 2,640 = 477,575 Btu/s/ft/Area. 477,575Btu/s/ft ÷ 1,129.62Btu/lb = 422.775lbs/sec = 50gps. Or in 60 seconds, this is 3,041 Gpm. For our 1,200 foot sections we can compute the heat intensity to be approximately 2,700 x .067 x 1200 = 217,080. This requires 192.17 Pounds of water every second dividing by the pounds per gallon tells us that we need to be supplying over 1,200 feet a rate of 23 gallons per second. Dividing the 23 by the number of nozzles we have, 12, each nozzle in the ideal world would have to flow 1.92 gallons per second. That is equal to 1.92 x 60 seconds or 115 Gpm.
INTERJECTION: This figure of course assumes you want the suppression done in that instant of time. We can afford to use the same 1” KK nozzles and spread out our time frame while the fire is still advancing and make progress at suppression. This is standard how we do it now. There are methods to determine the approximate amount of time for suppression operations as well but that is beyond the scope of this writing. However, simply stated the Suppression time is determine by the Btu being generated on a per minute or per hour basis divided by the absorption in Btu on a per minute or hour basis. The formula one can use is as shown below:
A 20gpm nozzle is only able to flow 0.33 gallons per second. And a 60gpm nozzle is flowing 1 gallon per second. So you would need nozzles flowing 120 gallons per minute the entirety of the fire line to instantly knock it down in that one second of time. Not possible.
Now this is largely figured for only a 1 and 5 mile per hour wind speed with a 70% slope and 4% Dead fuel moisture. Shown on the next page is a plot of the same fuel model with multiple wind speed plots from 7.5mph to 25mph. We will not discuss them, however, It is requested that one take a look at the Rates of Spread and the Intensities in Btu/s/ft and consider the logistical and control problems that would ensue with such activity after only dealing with a low wind speed problem so far!
Figure 6. (Page 10) shows the Heat Absorption Capacity of Water worksheet and is showing how to determine the amount of heat a pump, nozzle, helicopter bucket, SEAT, or LAT could absorb IF the individual with the right thought process and deducing skills are placed on the task.
This figure will show the amount of heat that a single nozzle flowing 20 gallons per minute can absorb.
One should be mindful that nozzles are rated in a Gallon Per Minute capacity while a fires Btu generation is on a per second basis. Always divide the Btu per minute capacity of a nozzle by 60 to determine it’s per second capacity to make sure it is able to absorb more than the fire is producing.
This fire according to these figures instantly places a hose lay out of reach but is something that still must be utilized for mop up, control and suppression all the same. As the fire in question was in February, the likelihood of having aircraft to be able to drop may not be available and even though it may appear futile, there are other aspects to consider and we will look at these.
The next phase of the problem is looking at our available resources and determining what can be placed where. So let us have a change in winds, our winds have dropped to 1mph and our rate of spread is now at 3.7 chains per hour, this gives us a ROS of 244 feet per hour, 4.07 feet per minute, .068 feet per second. Taking our .068 feet per second and multiplying by the HPA of 2700 gives us a new fire intensity figure of 183.6 Btu/s/ft. Let’s stop right here and think about this for a moment. .068 feet x 12 inches is .816”. This is just slightly less than 3/16th of an inch less than one inch per second. Now we begin determining the coverage area our 1” kk nozzles can cover and be effective with this Intensity figure.
Reviewing Figure 6 above, we see that the nozzle can absorb 3,139btu/second. If we take this figure and divide it by the fires Btu generation of 183.6 Btu/s/ft then we obtain 17. This is the area in square feet that this nozzle will be effective. Dividing this by the rate of spread of .068 feet gives us the effective line distance that this single nozzle can cover at this rate. 17, square feet ÷ 0.068ft per sec = 250 feet ea. If we have laterals placed every 100 feet, then we’ll have overlapping coverage.
The fire line in this scenario is 1.2 miles or 6,336 feet in length and nozzles every 100 feet would require a flow demand of 1,260 GPM. 63 x 20 = 1,260. This is going to require that we break this up into sections to be effective and the 1,260 GPM is assuming ALL nozzles are flowing simultaneously even though this may never be the case. (PLAN FOR IT!)
Our standard Cascade® wildland friction loss slide rules only go up to a flow of 800 gallons per minute and show only 2 ½” hose and this would require 130psi per 100 feet of hose. At 63 sections this would demand over 8,000 psi just in friction loss alone. For 1,200 foot sections it would still require 1,560psi. We must continue to break this up into sections once again. Taking the total distance and breaking it up to what a 2 ½” hose is more suited for would be a good start. Approx. 240gpm, and this means breaking the hose-lay up into 1,200 foot sections with 12 nozzles at 20gpm.
Shown on the next page is the sketch that one should make for their planning purposes. Figure 7
Initial locations of pump & snap tank platforms(shown as P-T). There would be 6 total not counting the Draft/Supply pumpers which could be located at either area or both at the Dunnfield creek drainage area closest to the Delaware River, or multiple portable pumps, could be setup at the Dunnfield parking area next to the creek. A third alternative is to use Class A pumpers and draft from the river itself, relay the water to another pumper and this 1st inline relay would in fact be the first of the 6 pumping platforms.
Pump platforms are spaced approximately 1,200 feet in distance (plus or minus) and each section would be comprised of 12 laterals 100 feet apart. The main trunk should be no less than 4” line size. At the location of each pump is a 3,000 gallon Pumpkin/Snap Tank. Portable pumps are a wide and mixed variety, however, for this area and the topography and terrain type presents unique challenges so this dramatically reduces the selection of portable pumps that would be available.
The 2 selections that could be used are the Rosenbauer Fox Gen 4 (Right) and the Darley Hercules (Left) Portable pumps. {other portable pumps could be used/substituted, however they must be able to provide the baseline flow of 240gpm at a minimum pressure of 200psi to viable}.
The Darley Pump could provide 240GPM @225psi and the Rosenbauer could provide for 264GPM @ 217psi. This information is derived from Manufacturer pump curves. The Darley pump weighs in at 225lbs and the Fox4 pump weighs 365lbs fueled and ready to go. Both pumps use a 4” suction and have 2 - 2 ½” discharge ports. Cost is believed would be the deciding factor.
The Darley & Rosenbauer pumps could be dropped in by helicopter. The Rosenbauer pump would need stortz to NH adapters and due weight might make sling loading more challenging but not impossible. The other issues are that both pumps to faciliate flows would have to use at least 3” line with 2.5” couplings as a minimum size for Friction loss aspects. It is preferred that the abilitiy to use 4” hose the entirety of the hoselay be done. Gravity feeding options present several other challenges such as not being able to supply pressure to the entirety of the nozzles and mainting proper flow.
The issue of dropping in Pumpkins on the Tammany Fire Rd and filling with helicopters is a moot issue and not recommended. The rationale being if you can air drop and fill pumpkins with a helicopter then you might as well be dropping on the fire foremost. Second, using helicopters to fill tanks and pumpkins is highly cost ineffective.
Also, relaying water from the fire road reservoir to the 6th pump and tank platform and supplying water that direction would require 4 plus miles of LDH and multiple pumps to facilitate and is believed to be time prohibitive and cost prohibitive.
Unfortunately, the only practical and visible area to obtain an abundant amount of water, and have a readymade scratch line for hose and holding is in fact Red Dot trail.
We now look in depth at the actual numbers of water supply on the next page. Keep in mind this is solving for ONE part of the problem, the initial supply. Delivery to nozzles must still take place and pending the activity of the fire may require double the number of pumps. One series to handle the initial supply, and another series to handle the actual nozzles at each section! Otherwise if multiple sections are flowing and depleting tanks and the intake is having to perform double duty, this could cause the operation to fail.
The Supply line Initial Setup. 4 Inch NH supply line.
Left side of map, At Dunnfield, North of I-80 (is up),
D = Draft site locations and at least two are selected, one north and one south of the interstate. If, the areas are covered with foliage and not accessible, then it would be wise to make them accessible. Any draft pump should be capable of supplying the rate to that which is demanded as opposed to simply “settling” for whatever is delivered by the pump. If a pump, for example, will not deliver say 720Gpm for the a flow that would Ideally be able to provide the full use of water for up to Platform 3, then it should be replaced with one that will. One should not even consider 3 or 4” trash pumps as a viable alternative regardless of the GPM rating because they will not build pressure and lose their head rapidly.
Numbers 1-6 are labeled with a P-T which stands for Pump & Tank. Each section lists the Head between sections, then the distance from the source pumper, then the elevation at that location.
S = Source Pumper location(s) two possibilities or both simultaneously. D = Draft Pump.
An operation such as this would necessitate a Water delivery crew being assigned to operate the pumps at the various sections. This operation should have at a minimum 6 Pump Operators and an assistant at each station. There should be a Supply Line side (BLUE), and an Attack Line side (RED).
Further this operation is of such that the Water Supply Organization needs its OWN tactical Frequencies and more than one to keep confusion down between the pumping platforms and the source pumpers operations.
Keep in Mind Cutting down to 6 laterals every 200 feet apart will drop the required Flow to 120GPM and the FL to half that value. Of course your suppression efforts are now half as well.
Equipment Needed: 6, Gated Wye Valves 4” NH Intake x 2 - 4” NH outputs.
Necessary adapters for connecting 4” to 2 ½” etc.
4” NH Supply Hose, Min 3,600 Feet. Preferably 5,600 feet.
2 ½” NH Attack Hose 25ft sections for Supply of Snap Tanks x 6 with snap tank mounts to secure the hose ends.
Back Flow Preventers at each Pump station sized for 4” NH supply line. OR in the alternative the Gated Wye Valves could be positions so they can serve as the backflow prevention devices. The caution to this is it being forgotten and left closed.
See the attached hose-lay spreadsheet for the next pages numbers.
Not all of the hose lay is clearly defined in this paper as it is considered a pre planning and draft.
Supply Line leg inputs.
All Leg inputs are initially calculated for only 240GPM.
The Leg 1 input is for the supply line being setup between the Source pumper to the #1 Pump Platform.
Distance ≅ 1200 feet
Elevation 520ft
Head 168ft
Np = 100
FL = 13.82
Hp = 72.91
Ep = 186.74
Leg 2 Input is between P1 and P2.
Distance ≅ 1200 feet (2400ft)
Elevation 720ft
Head 200ft
Np = 100
Hp = 86.8
FL = 13.82
Ep = 200.62
Leg 3 input is between P2 and P3
Distance ≅ 1200 - 1300 feet (3600ft)
Elevation between 890 & 903 ft
Head 183 ft
Np = 100
Hp = 79.42
FL = 13.82
Ep = 193.25
Leg 4 input between P3 and P4
Distance ≅ 1200 to 1300 feet (4900ft)
Elevation = 1209ft
Head 300ft
Np = 100
Hp = 130.2
FL = 13.82 – 14.5
Ep = 244.02
Leg 5 input between P4 and P5
Distance ≅ 1200 feet (5966ft)
Elevation = 1424ft
Head 210ft
Np = 100
Hp = 91.14
FL = 13.82
Ep = 204.96
Leg 6 Input between P5 and P6
Distance ≅ 370 feet (6,336ft)
Elevation = 1450 ft
Head = 27ft
Np = 100
Hp = 11.7
FL = 17
Ep = 9.98
The included Np figures are for if the same pumps are going to be providing the nozzle pressures between each Input leg. If a separate pump and hose (recommended) will be installed at each Pump Platform Snap Tank, then the Np’s can be removed to only that required to obtaining the flow to each respective tank, thus further enhancing the pumping capability at each station.
6300 feet of hose lay will require 63 1” kk nozzles. It is suggested that the flow be provided to the top, and the pumps to augment 240GPM via 2.5” hose pumping downhill so as to not have to overcome the Head pressures while supplying nozzles.
This is Option #1. As one makes a study of this scenario one should be able to see that providing for flows from a location that is at the bottom and no intermediary apparatus can be positioned into the desired locations. This would appear to offer up the best alternative for this exercise.
Joseph Moylan
hydro@wildfireengineer.com