Surfacing of Ramps and Driveways

Before undertaking the surfacing of a drive-in theatre, it is of paramount importance to remember that the raw earth of the original plot has settled for long centuries. Millions of rain storms, floods, snows and frosts have packed and kneaded it into its original contours. Therefore, it is to be expected that, regardless of how well the ground is rolled and tamped, some settlement and soft spots will develop in the new grade for some months after the bulldozers, graders, and diggers have finished their work of grading the area into curved ramps and crisscrossing it with drainage and conduit ditches.

WAIT FOR SOIL SETTLEMENT
In view of this fact, the wise drive-in operator does well to wait a full season, or at least two or three months, before dressing or blacktopping either his ramp areas or driveways. In short, serviceable, dependable surfaces cannot be hurried, for hastily devised paved or gravel surfaces that look and feel perfectly solid may react very badly under the narrow wheels and weight of continued automobile traffic. With the exception of marshy areas, the sub-soil itself is the key, and it will not support any top surfacing, even cement, until it has settled and adjusted itself to its new planes.

If sufficient care has been taken in the choice of materials and original construction, settlement soft spots should not show up in any one night in enough quantity to constitute a major headache. The theatre area should, of course, be checked every day for holes, which should be properly filled to promote a smooth, hard surface more rapidly. In this connection, the versatile jeep has been found to be an invaluable helpmate. Aside from its assistance during evening operating hours in carting supplies to the concession stand, transporting gas to patrons, and giving emergency jump starts, a jeep with a small truck body is helpful in taking men and materials out during the daytime to fill soft and low spots.

GRAVELS AND FILLS
When the proper time to surface has arrived, the choice of different grades of construction fills, such as gravels or slags, depends to a large extent on the location of the theatre and the resultant available materials; these, of course, vary in different sections of the country. In New Jersey, for example, the most logical material is a grade A gravel, which is abundant and relatively cheap, consisting of sand, clay, and stone. In Florida, by contrast, there is a crushed coral material which is ideal, inexpensive, and affords one of the best surfacing and base materials. In other areas, the by-products of quarries supply varying grades of gravel or stone chips which are "naturals" for this purpose. In the majority of cases, the cost of these materials is relatively low, and the price is determined primarily on the basis of the distance they must be hauled.

These foundation materials, however, should be selected wisely with durability in mind, as they rest on the raw earth and provide early drainage without great susceptibility to washouts. Furthermore, they provide a porous, binding surface for future paving materials.

Although a gravel surfacing, which has been laid up to six inches in depth, rolled and tamped over, provides an economical and serviceable topping, it has one unfortunate disadvantage. Since it harbors some of the more persistent weed pests, some complete sterilizaation or some continuous method of weed control is necessary. This requirement is particularly important in view of the fact that many of the weeds so nurtured are of the thorn and burr variety. Thus, aside from creating an untidy appearance, they are a constant source of discomfort to patrons who walk through the ramps in the dark on their way to concession stands or restrooms.

On the other hand, certain forms of slag, being of cinder origin, are not susceptible to weed growth. A waste product from the manufacture of steel and other smelted metals, slag is often available close to industrial areas and packs well to provide a firm road surface. Although slag is slightly more expensive than natural gravel, it possesses commendable features which make it a worthwhile surfacing material in ceratin sections of the country.

BLACKTOP AND OIL TREATMENT
Particularly popular choices for surfacing driveways bearing the heaviest traffic loads, blacktop and oil treatment are composed of essentially the same bituminous substances. Blacktop is factory-mixed and is applied as a black paving mass. Oil treatment, as the name implies, is a liquid that is sprayed on the gravel or slag surface at the site and then covered with stone chips or sand.

Blacktop is made in both hot and cold-mix varieties. The former, however, is not particularly suitable for drive-in purposes due to two factors; it requires special baking equipment on the job, and has the disadvantage of cracking and buckling when not in use by much traffic, a characteristic which makes it more desirable for highway construction.

The cold-mix surface, on the other hand, requires only grading and rolling on the job, although it has approximately the same surface strength as the hot-mix variety. Furthermore, since it has greater flexibility during idle periods, it is more adaptable to drive-in construction.

Oil treatment contains in itself a naphtha agent which evaporates and leaves a tarry residue. The oil may be of the medium cure type, which evaporates slowly, penetrates deeply, and gives a good sub-surface seal. Rapid cure oil evaporates readily and serves as a bonding agent for the sand or stone chips applied over it.

Blacktop surfaces are generally two inches thick. Oil treated surfaces are usually one quarter of an inch thick. Since numerous layers of oil treatment can be applied, one over the other as needed, their depth and strength can eventually be brought up to a par with those of blacktopping, with the added advantage that any blemishes or cracks can be repaired with each new application.

APPLICATION OF SURFACINGS
Since the average 700-car drive-in to take a case in point, would encompass approximately 36,000 square yards, a complete blacktopping would be quite expensive. However, in view of the fact that the entrance and exit driveways carry the major part of the heavy traffic, it is advisable to apply a good two-inch layer on such surfaces.

Before blacktopping is begun, a check should be made to insure that the sub-soil has been packed tightly, so that there is no further possibility of soft spots or low areas cropping up. In order to assure a smooth surface, a jeep with a drag line (usually a heavy wire screen with heavy weights attached) should be repeatedly run over the roughly finished driveway surfaces. This procedure saws off the tops of ground upcroppings and fills in depressions with displaced soil. All areas should be covered with three to six inches of gravel fill, crushed rock, or slag, well-packed and rolled down. The blacktop cold mix is then applied and rolled to produce the finished surface.

Oil-treated surfaces, however, are likely to prove more practical in ramp areas and other secitons of the theatre which receive less traffic. After these places have been smoothed out by drag-chaining, a three-quarter-inch layer of filler is applied to provide traction, and the areas are opened to traffic. Once all soft spots and settled areas have been dug up, filled, and surfaced again with crushed rock as they materialize, an oil treatment may take place with sand or stone chips laid on top.

Unless ideal soil conditions exist, however, oil treatment should not start immediately for several reasons. First of all, if the soil beneath is the least bit porous, the oil will go right through the surface materials and be lost. Secondly, if the oil-gravel combine is not proprely supported, it begins to crack, sink and settle unevenly under the weight of the cars; the result is generally the forcing of a second expensive surfacing job in preference to continual patching of depressions and cracks. Furthermore, if such a contingency occurs, it may mean the sacrifice of the entire area containing the oil-gravel combine; this disastrous eventuality will necessitate special equipment to break up the treated surface into small pieces at added cost.

A good solid surfacing will prove to be well worth the pains required to lay it. A poor one will sag under the weight of cars, buckle under weather stress, and give operators headaches.