Airborne Chemical Attack Addendum

Airborne Chemical Attack Addendum

In its January 1957 issue, FIRE ENGINEERING published an article “Airborne Chemical Attack on Brush and Forest Fires Pays Off,” which was widely and favorably received. The editors gratefully acknowledged the assistance of the Transland Company and its representatives, John T. Hales and Nick Spaise, in the preparation of the text of that report.

Since its publication, additional information on the subject has been obtained from the same source which further amplifies the published account and at the same time corrects certain omissions and revises some of the original findings.

Research history of air drops

The United States Forest Service first conducted aerial bombing trials in 1936. Study was made at this time of containers, aircraft, auxiliary equipment and personnel factors. The bombing experiments were again conducted in 1946 and 1947 by the Forest Service in cooperation with the Army Air Corps.

Paralleling this study was the development by Canadian foresters of a water bag drop technique which has met with considerable success. Other known studies have also been conducted in Australia.

In 1955, field trials, calibration tests and actual water drops were made on fires at Mendocino National Forest in California. These water drops proved effective in quieting hot spots on large fires and in retarding the spread of small fires in brush and grass.

During 1956, extensive aerial water and chemical drops were made on fires in both national and state forest areas in California. Between August 12, 1956, and September 30, 1956, a total of 23 fires were combatted by aerial tankers with a total of 83,120 gallons of water and 40,580 gallons of chemical retardant being dropped.

The drops were of real help on 14 fires, of good help on four fires, of no help on four and of adverse value on one fire. The latter drop put out a backfire and made control more difficult. Among these fires was the McKinley fire in San Bernardino County (FIRE ENGINEERING, December 1956), where revised data indicates 24,480 gallons of water and 25,400 gallons of chemical retardant were dropped.

The sodium-calcium borate used in these, as well as the later San Bernardino and San Diego drops, is produced under the trade name “Firebrake” and manufactured by the Pacific Coast Borax Company, Division of U. S. Borate and Chemical Corp., Los Angeles, Calif. When properly mixed with water, it will stay in suspension indefinitely. The mixed weight of the solution when used in a proportion of four pounds to one gallon of water is 10.1 pounds per gallon.

Chemical solution non-corrosive

The solution is reported to be noncorrosive to aircraft hoppers, tanks and dumping mechanisms. When the water dries after an aerial drop, the solution becomes very hard and is still fire-resistant when dry. The manufacturer states that there is no evidence that the solution will sterilize the ground for three years, cause soil breakdown or act as a defoliant as reported. At present, research is being conducted to determine the net effect to soil or plant life.

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