The surface of the old Telford Pavement was thoroughly swept by a machine-sweeper, and cleaned by stiff rattan brooms of all dirt and foreign material.

This surface was then scarified, loosened and reshaped. New two inch (2") Trap Rock Stone was added, in order to bring this surface to the proper shape and crown.

The surface was then covered with screenings and thoroughly rolled, so that it was three inches (3") below the top of the completed pavement.

On this prepared base was then placed the Asphalt surface, which consisted of:

(a) A Binder Course one inch (1") thick when compressed. (b) An Asphalt wearing surface two inches (2") in thickness when compressed.

The economy of using the old Telford Pavements as a base for a new Asphalt Pavement, brought about the following results:

1. It eliminated the earth excavation, which is necessary where a new base is required.

2. The saving in the cost of constructing a new Concrete base, six inches (6") thick.

Elizabeth, New Jersey, since 1914, has resurfaced over 150,000 square yards of this kind of pavement, with excellent results.

The average difference in cost per square yard, between a new Asphalt Pavement, with a six inch (6") concrete base, and a new Asphalt Pavement using the old Telford Pavement as a base, is $1.40 per square yard.

Our city, therefore, has actually saved over $210,000, by utilizing the old Telford Pavements.

The City of Elizabeth has six (6) streets over ten years old, where the old Telford Pavement was utilized as a base for the Asphalt Pavement.

These six roadways have been subjected to heavy traffic, and a recent inspection shows that the Telford Bases are holding firm. These results have convinced us that permanent and economical pavements have been obtained from this method of construction.

ECONOMICS OF SALVAGING OLD PAVEMENTS.

By R. Keith Compton, Director of Public Works, Richmond, Va.

It is assumed that in assigning this subject to the speaker, it was intended to include only those old pavements which may be used as a base and covered with one of the standard bituminous tops or wearing surfaces. The standard top would include the standard sheet asphalt pavement known as binder and top, asphaltic concrete-both fine and coarse aggregate, including the types known as Bitulithic and Topeka, and also Bessonite, the wearing surface designed some time ago by Major F. S. Besson, U. S. A., who was at that time assistant to the Engineer Commissioner, Washington, D. C.

The economics of this subject can be very intelligently discussed from a practical point of view, but it is a very difficult matter to intelligently discuss them from a financial standpoint. This difficulty is due largely to our governmental methods, both state and municipal, and our tendency to have a change of administration every few years, with the result that not only is there a change in the engineering executive, but frequently changes in the personnel of the engineer's office force. This results in either failure to continue systematic cost accounting or else considerable confusion in the records. A new executive coming into office is fortunate indeed if he can hold in office the subordinates who have been well trained by his predecessor and who are prepared to carry on the same intelligent system of cost accounting as may have been instituted under his predecessor.

Some years ago, urged by many of his colleagues, the speaker sent out a questionnaire on street paving and among the questions propounded was one as to conclusions regarding the life of each type of pavement and foundation. This questionnaire was sent to the responsible engineering head of approximately 750 cities of the United States and Canada, as well as to the State Highway Department in all the states. Approximately 300 replies were received to the questionnaire. Very few of them made any answer at all to the question regarding life of pavement and foundation, and those replies received as a rule were so indefinite and erroneous as to preclude any possibility of their being of value for publication. It is doubtful if there are a dozen municipalities which have accurate and well-balanced cost accounting methods on street pavement construction, with reference to replacement and maintenance.

The point the speaker is coming to is this: In every highway engineer's budget, be his position either municipal or state, there should be included three distinct accounts for street or road construction: New construction, replacement, maintenance; but, for the

purposes of this discussion, we are more particularly concerned in new construction and replacement.

New and old thoroughfares have to be considered in making up a paving program, and the engineer's duty is to obtain the best possible construction for the least cost. On unimproved or undeveloped roadways we have no choice except new construction under the standard methods, but roadways originally paved with stone block, cobblestone, brick, macadam and gravel can be considered as a base for a wearing surface of bituminous material. In considering this question we must, of course, estimate if we can the economy to the taxpayer, and the economy will be based on: First, the original cost of the old paving; second, its length of service; third, its cost in maintenance; fourth, its condition when resurfaced. It is on the first three points that the speaker desires to emphasize our weaknesses and point out that it is almost impossible to arrive at a value which can be depended upon.

Another point which must not be overlooked, but which is intangible in so far as a valuing it in dollars and cents is concerned, is the time saved during the period of construction of the new paving to the abutting property and to the public in general. The speaker has one point in mind which occurred in his office in Richmond just a few months ago. It was found desirable, in order to relieve one of our most prominent main business thoroughfares, to improve a parallel street. This street was first designed for a concrete base, 11⁄2-inch binder, 11⁄2-inch top. Its original pavement was secondclass granite block. The time assigned for its construction, including the period for the base to set, was 60 days. It was finally determined to allow the old block pavement to remain and resurface with Bessonite. The street varies in width from a 35 to 42-foot roadway and is 4,000 feet in length, including a cross street tying up the main thoroughfare. Its area was 13,454 square yards. The time saved under the resurfacing method, as compared with the original design, was approximately 66 per cent. It is impossible to value this time-saving to all concerned, but there is no question but that the value is great and should be considered in our plans.

The estimated cost of this street as calculated for concrete base and asphalt topping, including the hauling away of the spall for other work, was $39,366.00, or approximately $3.00 per square yard. The actual cost under the resurfacing method with Bessonite was $23,269.00, or approximately $1.73 per square yard. The actual saving, therefore, was $16,097.00, or $1.27 per square yard-a saving of 41 per cent.

On a similar job of approximately 6200 square yards, the total cost of concrete base, binder and topping was estimated at $18,000.00, including all incidentals, or approximately $3.00 per square yard. Under the resurfacing method with Bessonite the actual cost was $9,300.00, or $1.59 per square yard. This represents a total saving

of $8,600.00, or $1.41 per square yard-a saving of 47 per cent. On this project the estimated time for standard work was 35 days. The resurfacing method was completed in seven days, a saving of 28 days in time, or 80 per cent.

There is yet another case in which resurfacing of gravel was used in place of a concrete base and standard binder and topping. This street, which is about 1,000 feet in length and 42 feet in width, was found to have an excellent gravel base. It was finally decided to resurface the gravel with Bessonite instead of placing a concrete base. Our estimated cost for standard construction-that is to say, concrete base, 12-inch binder, 12-inch topping-including excavation, was $14,700.00, or $3.00 per square yard. The actual cost of resurfacing was $7,874.00, or $1.67 per square yard, a saving of $6,788.00, or $1.33 per square yard. This represents a saving of 48 per cent.

The average saving in time on the three projects was 71 per cent and in money 45 per cent.

Where there is a possibility of saving the old bases and utilizing them for resurfacing work, it is the speaker's opinion that a great deal can be saved, and almost, if not as good a pavement, with as long life, be had. Of course, in the resurfacing of granite streets we cannot hope to have the perfect contour which would be gotten by laying a concrete base to the proper grade, but there is so little difference in the riding qualities of a well-resurfaced street and a newly constructed street that the difference is inappreciable. The extra money that can be saved will go that much farther to give the city additional paving.

Although it is impossible to estimate closely the life of granite spall paving, it would seem that if it had given service for twenty years that you might safely say that it had paid for itself and therefore it does not owe you anything.

From the above figures it would seem reasonable to estimate that by resurfacing you really save the cost of a concrete base.

Another point which the engineer should give consideration to is the installation of underground structures such as water, sewerage, gas, etc., and if these structures are to be installed, what will be the condition of the old pavement when he is ready to install the top? The speaker can point, during his fifteen years of experience in street paving operations, to any number of old block pavements which were in good condition for resurfacing at the time of the first inspection, but after underground structures were installed the pavement was practically useless as a base. In the case of old stone pavements, such as granite block, spall or cobble, it is impossible to relay this material as securely as it was before being disturbed. If there are any number of trenches in the street and an attempt is made to concrete them, it will be found that the expense incident to such construction will largely increase the cost. In such cases, it has been the speaker's experience that the best thing to do is to