Most fire chiefs know that ethanol poses a serious threat to a community and some know that it takes an alcohol-resistant AFFF concentrate to handle the incident.

The only UL-approved AR-AFFF concentrates available in the United States are 3% or 6%. The most current version, from 2005, of NFPA 11, Low -, and Medium-, and High-Expansion Foam, breaks down liquid-fuel fires into two major and five minor categories: spill fires — loading racks, diked areas and non-diked areas; and tank fires — full surface and seal area.

Within each of these categories, the standard spells out what the minimum-required flow rates are and the minimum duration these flow rates need to be sustained. The standard for a non-diked spill fire, the most common municipal incident, calls for an AR concentrate being applied at a minimum flow rate of 0.10 to 0.16 gpm per square foot of surface area for a minimum of 15 minutes. Generally, it is better to not begin an attack if these criteria cannot be met.

Departments should build in a safety factor of at least 50% to both the flow rates and flow duration. This is even more critical with ethanol. Most experts will plan for a minimum of 0.25 gpm per square foot.

An over-the-road tank truck typically carries 5,000 to 6,000 gallons while a rail tank car can carry 30,000 gallons. With these volumes, the spill areas can become quite large, particularly if more than one tank car has ruptured. Consider a spill area of 100 by 100 feet, or 10,000 square feet. NFPA 11 calls for a minimum of 0.16 gpm per square foot with a preferred rate of 0.25 gpm, which is 1,600 and 2,500 gpm, respectively. The minimum flow duration is 15 minutes while the preferred duration is 23 minutes.

Most departments will use 300-gallon totes or larger. These can be loaded on a flatbed trailer where the totes are connected with a common manifold to minimize the logistics of supplying concentrate. Another option is to find an old oil tanker and convert that to a foam trailer. These usually can be picked up very cheap. Use the density of the concentrate as the basis for calculating the tanker's capacity. Foam concentrate is more dense than fuel, and a 6,000-gallon fuel tanker may only safely carry 5,000 gallons of foam concentrate.

There are several ways to deliver foam. At the low end of the technology curve is the jet ratio controller, or JRC. Think of it as a super eductor. With a 1H-inch inlet and a 2H-inch outlet, it will provide approximately a 60-40 ratio of water to concentrate.

This super-rich foam solution is pumped to a monitor along with other lines supplying plain water. The two are mixed and hopefully the end result will be the desired 3% or 6% foam solution. There is some guesswork with this technique. For each JRC, plan for at least three personnel to handle the foam totes. The advantage of JRCs is their low initial investment. In operation, the wasted foam due to the system's inaccuracy and manpower requirements give JRCs a high operating cost.

At the other end of the technology curve are the automatic proportioning systems, such as the balanced-pressure and direct-injection proportioners. Both can be plumbed with single or multiple foam mixing points. The direct-injection systems offer several advantages over the older balanced-pressure technology. First, there are no flow restrictions, as they do not require a venturi. Second, they can be calibrated and tested quickly without consuming concentrate. Third, their accuracy and wide performance range cannot be matched by the balanced-pressure systems. Cost of the balanced-pressure and direct-injection systems are comparable. While the purchase prices are more than a JRC, the savings in staffing significantly reduce the operating costs of both. The accuracy of the direct-injection systems along with the labor savings makes its operating cost the lowest.

Foam-proportioning trailers are becoming popular in big-water foam operations. There is a significant advantage to having all of the water treated with foam at one central point, and a foam trailer can accomplish this. One trailer option uses a FoamPro AccuMax 3300 direct-injection foam proportioning system, supplying 2- to 3-inch and 2- to 6-inch manifolds. Each manifold is controllable for either plain water or foam solution from 0.1% to 10%.

With ethanol, as with any polar solvent, it is important not to plunge the foam into the fuel. The most effective means is to apply the foam as gently to the surface as possible.

Big-water operations are something that must be practiced before the incident. It is important to know for sure that a department can supply the required amount of foam solution for the necessary length of time and what it will take to do so.

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Bill Ballantyne is vice president of FoamPro Division of Hypro LLC.

Foam System Requirements (to supply 2,500 gpm)

Pumping distance (feet)	750	1,500
Application rate (gpm per square foot)	0.25	0.25
Flow rate (gpm)	2,500	2,500
Number of engines at 1,500 gpm	2	4
Number of 2.5-inch supply lines	10	10
Number of 4-inch supply lines	4	4
Number of 6-inch supply lines	2	2
Number of 8-inch supply lines	1	1
Flow rate (gpm)	2,500	2,500
Total water (gallons)	57,500	57,500
Proportioning rate	3%	6%
Concentrate flow rate (gpm)	75	150
Total concentrate required (gallons)	1,725	3,450
5-gallon pails (number required)	345	690
55-gallon drums (number required)	32	63
300-gallon totes (number required)	6	12
6,000-gallon tankers (number required)	1	1
Flow rate (gpm)	2,500	2,500
Proportioning rate	3%	6%
Concentrate rate (gpm)	75	150
5-gallon pails (usage rate)	4 seconds	2 seconds
55-gallon drums (usage rate)	43 seconds	22 seconds
300-gallon totes (usage rate)	4 minutes	2 minutes
6,000-gallon tanker (usage rate)	80 minutes	40 minutes

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