The Nation's Heaviest Airport Grading Project
The Kanawha Valley Airport
The Nation's Heaviest Airport Grading Project
In October 1944, in Charleston, W. Va., the contract for the Nation's Heaviest Airport Grading Job was awarded to Harrison Construction Company of Pittsburgh, Pennsylvania by the Kanawha County Court. The citizens of Kanawha County voted a $3,000,000 bond issue for the construction of a Modern Air Terminal, located approximately two and one-quarter miles northeast of the city of Charleston, and four and two-tenths miles by road from the business section of the town. Later Congress appropriated $2,750,000 to supplement the County fund to assure the completion of the Airport.
To complete the airport will require the moving of approximately 9 million yards of material of which 40% is rock. The maximum cuts of 130 feet and fills lowing out as much as 209 feet below the elevation of the airport. The airport is located on a series of ridges, whose area and direction make it ideal for the construction of three runways projecting into the maximum wind quadrants. The length of the runways will be. No. 1 6,000 feet; No. 2 5,000 feet; and No. 3 5,200 feet.
The site presents a very rugged terrain involving extensive grading operations, however, no other site within a reasonable distance of the city presents less difficult terrain. A mountain top site has been selected because any site available in the valley is unsuitable for the development of more than one runway of adequate length and with proper clearances in the required approach trapezoids. In addition, valley sites will be covered with mist and fog much more frequently than will a mountain top site. For all other sites investigated, the topography was such that the construction of runways of adequate length was impractical or land damages excessive.
In the early stages shovels worked on ledges that were 300 feet or more above the lowest ravine filling levels. Due to layers of pan materials between stone strata there was little opportunity for scrapers to load downhill. Early stage haul roads for both stone and dirt were among the steepest ever encountered by Harrison's men. Temporary roads up to 40% descending grades for scrapers and 25% for dump trucks. Main haul roads, those which could serve for several weeks between main cut and fill areas, are contoured to hold grades below 15% to 20% in order to save wear and tear on equipment.
The rock excavation was hauled by nine 1 3/4 yard to 2 1/2 yard shovels loading a fleet of twenty- three 10-yard rear dump trucks and eight 11-yard and 12-yard bottom dump trailers. The earth excavation was handled by ten 25-yard tractor-drawn scrapers and sixteen 12-yard scrapers. Seven pushers with the help of four rooters served the scrapers. With this equipment the contractor averaged from 20,000 to 27,000 cubic yards of earth and rock a day.
Alternate rock and shale layers created a situation favorable to horizontal drilling and blasting. This method is being used for all but small special pockets, where six wagon drills are employed, powered by five 365 cu. ft. compressors. Horizontal shooting has proven very successful with excellent fragmentation by this method, which also leaves the broken mass in convenient position for efficient shovel loading.
Two horizontal power drills are employed, one fitted with automatic feed. The procedure is to go into the hillside or face with parallel six-inch holes, spaced generally from 10 to 20 feet apart and carried from 40 to 60 feet back into the shale. The idea is to lift some 20 to 40 feet thickness of material at a shot.
Dynamite used is mostly 40% although some 60% has been tried. A typical blast consists of 2,500 pounds of dynamite placed in nine parallel 45 foot holes. There has been approximately 1,000,000 pounds of dynamite used to date.
For the bulk of the filling to within 20 to 40 feet of the embankment edge, run of shovel stone and scraper material are dumped on the grade mixed and spread by bulldozers, and rolled in 2-foot layers by 10-ton rollers. Individual stones too large for such layers are broken by a 4,000 pound skull cracker mounted on a crawler-crane.
To maintain all this equipment a large field shop was erected wherein hundreds of overhaul jobs have been turned out by repairmen, which at the present consists of 40 mechanics.
The airport was designed originally by Whitman, Reguardt and Associate Engineers of Baltimore, Maryland, and the paving and drainage was designed by Civil Aeronautics Administration.