Aviation Department Tech Tips Logo of USDA Technology & Development Program
June 1995
5700 9557 1305 - SDTDC

Portable Retardant Bases
Melinda Seevers, Phoenix Design Engineering

Why fight fire with just water when long-term retardant or foam could be used? Portable retardant base systems remove one of the barriers to using more effective fire fighting retardants. Portable retardant bases can enable aircraft- either fixed or rotary wing-to attack a fire from the closest possible location. This can maximize cost effectiveness and efficiency, especially when used with heavy lift (Type 1) helicopters.

Portable retardant bases mix and distribute long-term retardant to aircraft at locations without a permanent retardant base, locating the retardant base as close to the fire as possible. Ever-increasing environmental concerns can be addressed by careful location of a retardant base, along with using proper procedures in the handling of the retardant. Water intake screens may be required to protect animal life in water sources. Other considerations for choosing a base location include a sufficient water supply and adequate space to provide separation between the water source, mixing tanks, and dip tanks.

Although existing portable bases have been used successfully, increased access is still needed to remote areas. At present, access is limited to improved roads because of the size and weight of the chemical containers and associated equipment. More portable systems could access less improved roads, or even be airlifted by helicopter to areas with no road access. An additional design improvement for the tanks themselves would be sturdy dip tanks with larger openings and more depth.

Two companies, Monsanto Company Wildfire Division and Chemonics Industries, Inc., FIRE-TROL® Division currently have portable retardant bases available on a contract basis.

Monsanto Company Wildfire Division Portable Retardant Bases
The Monsanto Company Wildfire Division has three types of portable retardant bases available: the Portable Air Base, the Mobile PHOS-CHEK® Base, and the Portable Helicopter Base. The Monsanto systems are capable of mixing and loading retardant into fixed-wing airtankers or helicopters at a rate of 21,000 gallons per hour (79,490 Lph). Monsanto Wildfire provides a technical representative to assist in equipment assembly and to advise and to assist the mix crew for all systems.

Each of the portable retardant bases uses either PHOS-CHEK D-75F, D-75R, G-75F, G-75R or 259F long-term retardants. These retardants have U.S. Department of Agriculture (USDA), Forest Service, approval for use with fixed-wing airtankers and helicopters with buckets. PHOS-CHEK 259F also has approval for use with fixed-tank helicopters. A summary of the Monsanto systems available is shown in table 1.

Table 1-Summary of Monsanto's Portable Retardant Bases.
Unit Name Capability in Gal/hr (L/hr) Product Packaging Aircraft Type
Portable Air Base (PAB) 21,000 (79,490) D75F or D75R Phos-Bin containers or airslide trailer Fixed Wing
Mobile PHOS-CHEK Base (MPB) 21,000 (79,490) G-75F or 259F 18-ton self contained resupply with airslide trailer Rotary Wing
Portable Helicopter Base (PHB) 21,000 (79,490) G-75F or 259F Phos-Bin containers Rotary Wing

® FIRE-TROL® is a registered trademark of Chemonics Industries, Inc.
® PHOS-CHEK® is a registered trademark of Monsanto Company, St. Louis MO.

Monsanto Portable Air Base (PAB)
Monsanto's PAB is primarily intended to mix and load PHOS-CHEK long-term retardant into fixed-wing airtankers. The system is available in different configurations to service one or numerous aircraft operating from an existing airport. During the 1988 fire season in Helena, MT, a PAB system supplied retardant to a fleet of eight Modular Airborne Fire Fighting System (MAFFS) equipped C-130 aircraft.

The system uses a 1,000- or 3,000-gal (3,785- or 11,360-L) water storage tank, one to two retardant mix tanks and either a 6,000- or 15,000-gal (22,710- or 56,780-L) capacity tank for retardant storage. A combination of fold-up, metal frame, and open-top self-supporting collapsible tanks are used. Other primary components include a 350-gallon-per-minute (1,325-L-per-minute) eductor mixer, pumps for circulating and retardant loading, a Phos-Bin® container air supply, a water meter, and an aircraft loading manifold including hoses and valves. The weight of the PAB system is approximately 10,000 lb (4,536 kg), and can be transported either on a flatbed trailer or in a cargo aircraft.

® Phos-Bin® is a registered trademark of Monsanto Company St. Louis, MO.

Requirements for the PAB include a water supply capable of providing 350 gallons per minute (1,325 L per minute), road access for a semi-trailer, an appropriate site with working space of 100 by 150 feet (30.48 by 45.72 m) adjacent to the aircraft loading area, a 5,000-lb (2,268-kg) capacity forklift, a two-person mixing crew and a minimum of two people to direct and load the aircraft. Monsanto personnel for mixing and aircraft loading can provide. PHOS-CHEK retardant can be provided in Phos-Bin containers or in bulk in airslide trailers for high-volume use if the base is located close enough to Ontario, CA, to permit efficient resupply. The term 'airslide' trailer refers to air that is blown through the powder retardant stored inside of the trailer, which causes the powder to flow as a liquid to dispense the dry retardant. The Phos-Bin containers use the same compressed air blowing system. Setup of a PAB after equipment arrives at the base requires 2 to 3 hours, using 2 to 4 people.

Monsanto PHOS-CHEK Base (MPB)
The Monsanto MPB is a mobile system similar to the PAB, except that it is mounted on an airslide trailer and is intended for use with a multi-helicopter campaign. A photo of the MPB is shown in figure 1. Normally, the MPB would mix either PHOS-CHEK G-75F retardant (or PHOS-CHEK 259F retardant if any fixed-tank helicopters would be using the system), and would be located at a helibase close to the fire.

Approximately 18 tons of dry powder retardant are available on the airslide trailer, which is enough to produce 34,000 gal (128,700 L) of retardant solution. Additional Phos-Bin containers can be used, but would require a forklift. The system includes a 350-gal-per-minute (1,325-L-per-minute) eductor mixer, 500-gal (1,893-L) water and retardant solution storage tanks attached to either side of the trailer, open-top self-supporting collapsible dip tanks (6,000- or 15,000-gallon capacity [22,710- or 56,780-L capacity]), loading hose, valves, and numerous fittings to provide flexibility. One to three different dip tanks can be used at the same time. Choices of tanks would depend on type, turn-around times, and number of helicopters.

An MPB site must have an adequate water source, sufficient space to accommodate equipment setup and safe helicopter operations, and road access to truck in the system. Monsanto recommends that the road be at least adequate for use by a Low-Boy trailer carrying a bulldozer. A minimum two-person mixing crew is needed. The ordering agency is responsible for providing any additional personnel needed to direct and/or to load the helicopters.

Monsanto Portable Helicopter Base (PHB)
The PHB is similar to the PAB, except that it is designed for helicopter use only. It does not utilize the airslide trailer as the source of retardant powder. The PHB uses dry retardant (either G-75F or 259F) packaged in 1-ton (1,016-kg) Phos-Bin containers. The 259F retardant must be used if helicopters with fixed tanks are going to operate from the PHB.

Mixing and distribution of retardant is accomplished with a 350-gallons per minute eductor mixer, hose, valves, and pumps. A diagram of the PHB system is shown in figure 2. To accommodate all sizes of helicopters, either 6,000- or 15,000-gallon (22,710- or 56,780-L) dip tanks are available. As with the MPB, one to three dip tanks could be set up, although two is usual. Aircraft can be separated by size when the system is set up for multiple flight paths. Monsanto Wildfire has recently redesigned a more efficient PHB system.

An adequate water supply, sufficient room for safe operation, a 5,000-lb (2,268-kg) capacity forklift with operator, and a two-person mixing crew is required.

Availability and Further Information
There are currently three PAB systems; two are based at Monsanto Wildfire's Ontario, CA, facility, and one is based at Channel Islands Air National Guard Base for use with the C-130 aircraft MAFFS system. At time of publication, one MPB system was based at Monsanto's Ontario, CA, location. Three PHB systems were available with a fourth system possible for the 1995 fire season. Monsanto emphasizes that additional helicopter support systems can be fabricated from modular equipment available at the Ontario facility.

The Monsanto systems are on Emergency Rental Agreements with the U.S. Departments of Agriculture and Interior, which are administered from National Interagency Fire Cache (NIFC). Additional information regarding the Monsanto portable retardant bases, including current pricing, is available from:

Monsanto Co., Wildfire Division
810 E. Main St.
Ontario, CA 91761
Day: (909) 983-0772
After Hours: (909) 946-7371

Chemonics Industries, Inc., FIRE-TROL® Division Mobile Retardant Base
Chemonics Industries, Inc., FIRE-TROL Division, provides Mobile Retardant Bases, known as MRBs. The MRB system enables the mixing and loading of Chemonics FIRE-TROL LCA, LCG-R or -F (regular or fugitive colored) liquid concentrate (LC) long-term retardant at locations without permanent retardant bases. Helicopter operations with close proximity to wildfires, or temporary fixed-wing operations at airports can be conducted with the MRB. The MRB is capable of supplying mixed retardant at 450 gal per minute (1,703 L per minute). As much as 10,000 gal (37,850 L) of LC (enough to produce 60,000 gal [227,100 L] of retardant mixture) can be stored onsite. FIRE-TROL LCA liquid concentrate long-term retardant is approved for use with fixed-wing airtankers and helicopters with buckets. At the time of this publication, FIRE-TROL LCG long-term retardant had conditional approval for these same aircraft.

Helicopter Operations or Fixed-Wing Air Tanker Operations Requirements
For helicopter operations, a usable water supply capable of providing water at 450 gal per minute (1,703 L per minute) (either water tender or natural source), and adequate space for safe helicopter bucketing operations are necessary. FIRE-TROL LC can be transported to the retardant base in small quantities and stored in portable tanks if road access restricts the use of large transport containers. An additional dip tank can be set up to use foam, such as Fire-Trol FIREFOAM® 103 or 103B fire suppressant. A suitable airport with a water supply and two operators are required to set up the MRB for normal airtanker operations. Chemonics can provide additional personnel.

System Description
The FIRE-TROL LC can be supplied from a tanker trailer or from a portable LC storage tank. With the exception of the LC, all of the MRB components, including the dip tank, are completely self contained and are trailer mounted. The water and concentrate are mixed by the orifice blender on the MRB trailer, and, at the same time, the retardant solution is pumped to the airtanker intake or helicopter dip tank. The system includes three 6,000-gal (22,710-L) flexible water storage tanks, four pumps, 3- and 4-in (76.2- and 101.6-mm) hose lines, a Model 400 orifice blender, MRB trailer, LC storage tanker trailer with approximately 10,000-gal (37,850-L) capacity, 6-in (152.4-mm) aluminum irrigation pipe and manifold, a 5,000-gal (18,930-L) capacity steel dip tank, and environmental berms and pads to contain any spills around the MRB trailer.

® FIREFOAM® is a registered trademark of Chemonics Industires, Inc.

As shown in figure 3, water is pumped from the water source via two 3-in (76.2-mm) 300-gal-per-minute (1,136-L) pumps into the three connected 6,000-gal (22,7100-L) self-supporting open-top, collapsible holding tanks. Water and concentrate are proportioned through the orifice blender on the MRB trailer at a mix ratio of either 5:1 parts of water to concentrate for LCA or 4.75:1 for LCG. A 3-in (76.2-mm) pump transfers concentrate from the storage tanker trailer to the orifice blender. Retardant solution is then pumped and further mixed by a 4-in (101.6-mm) 450-gal-per-minute (1,703-L) pump through the aluminum irrigation pipe to the airtanker or portable helicopter dip tank. The aluminum pipe has special gum/rubber pressure sealed gaskets to prevent leakage.

The Chemonics MRB is shown in figure 4. The dip tank is an 8 ft-deep (2.44-m), 10 ft (3.05-m) in diameter steel cylinder with an additional top flange that provides extra protection against spills and increases the outside diameter at the top to 14 ft (4.27 m) for improved helicopter bucket access. The flange is installed at the retardant base, constructed from 16 pieces which slide into receiver sockets, and bolted into place. The dip tank has a side-mounted axle, wheels, and towbar that allow it to be towed to the temporary retardant base location. All systems tanks have been designed for easy emptying and cleaning.

For additional protection against spills, a pad (ground cloth) is placed under and around the MRB trailer, the dip tank, and the concentrate storage tanker trailer. The pad is constructed of a high-density, lightweight, repairable, polypropylene-weave material. An inflatable collar on the pad sides is filled with either air or water to an approximate height of 16 in (406.4 mm) to form a berm. Environmental pads with inflatable collars are also used with the 3-in (76.2-mm) pumps, which pump water or unload concentrate from a delivery truck or trailer.

Availability and Further Information
The MRB and personnel are available from Chemonics Industries, Inc. on a national contract basis. There are four MRB units that are based at strategic locations in the west, as fire season warrants. For contract pricing, ordering, or additional information, contact Chemonics Industries, Inc., FIRE-TROL Division at:

Chemonics Industries, Inc.
FIRE-TROL Division
P.O. Box 277
County Road 200 East
Orland, CA 95963
Phone: (916) 865-4932
Fax: (916) 865-5479

All system information was provided by Monsanto Company Wildfire Division and Chemonics Industries, Inc., FIRE-TROL Division.

Support Systems
The following information is provided on services related to portable mixing bases.

Adequate water supply and the ability to separate equipment are important considerations when setting up portable retardant bases. Portable Water Supply System Co., Ltd. (PWSS) provides a system which could be used for high-volume water supply to mixing bases. The system uses a high-volume (1,200 GPM [4,542 LPM]), high-pressure pump that can be placed at water sources up to 200 ft (60.96 m) horizontal or 165 ft (50.29 m) vertical from the power unit. Standard with the system is 1 mile (1.61 km) of 5-in (127-mm) diameter hose, 600 ft (182.9 m) of 3-in (76.2-mm) hose, and a complete supply of NST and camlock fittings. Also provided are portable hydrants, personnel, hosetender, and heavy-duty vehicle hose ramps that allow vehicles to cross hoselines. PWSS can set up the pump and power unit portion of the system in 10 to 30 minutes. Hoseline lays out by truck, and can be set up quickly depending on length and terrain.

Current rates (1995) for the PWSS water system are $2,875 per day. If the system were deployed with a remote mixing base on a multiple-day incident, this cost could be recovered in time savings after only a few round trips with one Type I helicopter at approximately $7,000 per hour. For example, reducing turnaround time by 9 minutes each trip by locating the PWSS system mixing base in a more remote area for a hypothetical three round trips saves 27 minutes or $3,150 (1995), full recovery of the PWSS cost. The same rationale applies to the use and cost recovery of the portable mixing bases themselves, but the cost savings can obviously be increased as the base is placed closer to the incident.

Air-Ops Support Services/Tin Man's Emergency Services provides helicopter dip tank systems and support personnel. The systems include 15,000-gal (56,780-L) soft-sided dip tanks, receiving and storage tanks, pumps, hose and fittings, foam proportioning, and spill containment equipment. The system is capable of long-term retardant production, although the company does not supply the concentrate. The dip tank systems can be prepared for air cargo overnight delivery throughout the United States. The company can also supply water tenders.

For current pricing, ordering, or additional information, contact the companies as follows:

Portable Water Supply System Co., LTD.
3184 Spring Street
Redwood City, CA 94063
Frank Blackburn, President
Phone: (415) 368-0428
Fax: (415) 368-0446


Bob Kress
Director of Wildland Operations
Phone: (209) 795-4119

Air-Ops Support Services/
Tin Man's Emergency Services
Phone: 1-800-522-8662

The Technology and Development Center is interested in receiving feedback from the field regarding successes or failures encountered with these systems.

TD logo
For Additional Information Contact:
Aviation Program Leader
San Dimas Technology and Development Center
444 East Bonita Avenue, San Dimas CA 91773-3198
Phone 909-599-1267; TDD: 909-599-2357; FAX: 909-592-2309
E-mail: mailroom_wo_sdtdc@fs.fed.us

Information contained in this document has been developed for the guidance of employees of the Forest Service, United States Department of Agriculture (USDA), its contractors, and cooperating Federal and State agencies. The USDA assumes no responsibility for the interpretation or use of this information by other than its own employees. The use of trade, firm, or corporation names is for the information and convenience of the reader. Such use does not constitute an official evaluation, conclusion, recommendation, endorsement, or approval of any product or service to the exclusion of others that may be suitable.

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