Mr. HOLIFIELD. Now, there you have a door that would give you much more protection than a wood door.

Mr. VORTMAN. This is a wooden door. The report (WT-1218) shows the thickness to be two thicknesses of 1-inch plywood.

Mr. HOLIFIELD. Your walls of that bathroom were 3 inches of concrete.

Mr. VORTMAN. Eight inches of concrete, walls, ceiling, and floor. Mr. HOLIFIELD. Would that indicate that your 3-inches of plywood would give you the same protection as 8 inches of concrete? I would not suppose that it would.

Mr. VORTMAN. Over the short span of the window and the door they would.

Mr. HOLIFIELD. As far as gamma penetration is concerned, they would not serve the shielding purpose like concrete?

Mr. VORTMAN. There again the shielding was about the same as in the shelters discussed earlier.

Mr. HOLIFIELD. Did you have a reading on the roentgens of exposure in those?

Mr. VORTMAN. I have again the shielding factors that I had before. The shelter reduced the prompt gamma radiation to only onequarter of that outside.

Mr. HOLIFIELD. Give it to us in the number of roentgens, if you have it, as well as percentagewise.

Mr. VORTMAN. The levels inside were of the order of 25 to 50 roentgens.

Mr. CORSBIE. And that was at 4,700 feet. Just short of a mile from the bursts I mentioned earlier; 30 to 35 kiloton.

Mr. HOLIFIELD. Well, you could survive with a 25- to 50-roentgen dose. You might lose a few white corpuscles, but it certainly would not induce a sickness that would be fatal.

Mr. CORSBIE. That is right. I mention that this was a shelter in which there were 2 animals which were taken out within 2 hours after the burst and apparently were undamaged.

Mr. HOLIFIELD. What did their blood count read, do you know? Mr. CORSBIE. No, sir; I do not have that information.

Mr. HOLIFIELD. There was an appreciable decrease of blood cells, I suppose?

Mr. CORSBIE. Well, that was a pretty low level of radiation, but there might have been.

Mr. VORTMAN. The maximum pressure inside these same shelters was one-quarter of the maximum overpressure measured outside of the shelter.

At this point I would like to mention some of the disadvantages of aboveground structures. The most important is that while most structures are designed to carry vertical loads, few, except earthquake-resistant structures are designed to take any significant lateral loads.

In addition, blast pressures are even greater on structures built with vertical walls above ground than on those built flush with the ground, because of the reflected overpressure and the drag pressure which loads the aboveground structure.

Aboveground structures, then, are economically practical only for relatively low pressure levels. Although such structures can be made to resist high pressure levels as in the reinforced-concrete protective vault in Operation Plumbbob-this was project 30.4, and perhaps someone from FCDA may discuss that particular project—the costs of such structure are high enough to discourage their use except for very special structures.

It should also be kept in mind that aboveground structures do not ordinarily provide adequate protection from prompt radiation. In most cases, adequate radiation protection can be furnished only by providing adequate earth cover and a suitable entrance detail.

Mr. HOLIFIELD. However, there are areas in our country where the water level is so high in the ground that it would probably be necessary to have structures above ground, if structures were planned, and in those cases different shapes of structures would be needed. I am thinking of the quonset hut, arch-type structure. The mounding of earth over such a structure would give aboveground protection which would help to compensate for these factors you have mentioned. Mr. VORTMAN. That is certainly right.

Mr. HOLIFIELD. Was not this proven in subsequent tests?

Mr. VORTMAN. It has been and I will go right into that in the following example.

The first of these examples I want to show is a shelter sponsored on Operation Greenhouse by Office, Chief of Engineers, and it is shown in figure 9.

56'-0"

Sectional Plan

56'-0"

Transverse Section

71'-0"

71'-0"

Longitudinal Section

PERSONNEL SHELTER

FIGURE 9.-Personnel shelter.

Mr. HOLIFIELD. What year?

Mr. VORTMAN. 1951.

This structure consisted of one end of rectangular reinforced concrete construction, the other end of circular reinforced concrete pipe and then on the very end, one section of corrugated metal pipe.

The structure was partially above ground and covered with 6 feet of earth, as you can see in the transverse section and the section below. The shelter was satisfactorily tested and resisted between 50 and 70 pounds per square inch.

The loading of the structure by the earth cover was not as clearly defined as the one I want to show in the following project.

Mr. HOLIFIELD. Did you have distances on that, by the way, from this shot and also the kiloton yield?

Mr. VORTMAN. There again I believe the yield of that shot is still classified, is it not, Mr. Corsbie?

Mr. CORSBIE. Yes.

Mr. HOLIFIELD. Now, let me ask for the record, why should the yield of that shot be classified?

Mr. VORTMAN. That is a question I certainly am not prepared to answer. People dealing with weapons development would have to answer a question of that type.

Mr. HOLIFIELD. All right.

Mr. VORTMAN. I might point out, however, in passing, with regard to questions on the overpressure that if a yield is classified, then the overpressure and distance combination are also classified because one can infer the yield, knowing the overpressure and the distance.

Mr. ROBACK. Mr. Corsbie, may I ask before you proceed, the explosions of these test shots were developmental in the sense that they were designed to test the weapons rather than to test the shelters? Therefore, you could not necessarily get the information you wanted and you could not declassify it?

Mr. CORSBIE. That is correct. These are weapons developments shots as contrasted with weapons effects.

Mr. ROBACK. The weapons effects people are the orphans in these experiments. They are designed for other purposes and you have to hook in the best way you can. Is that not right?

Mr. CORSBIE. That has been generally the pattern followed.

Mr. HOLIFIELD. Notwithstanding the fact that this was primarily for developmental purposes, the scientific knowledge as to pressure per square inch and intensity of radiation could be determined subsequent to the shot and therefore related to the effect upon structures and animals within those structures, could it not?

Mr. CORSBIE. As a matter of fact, it was measured at the time. Mr. HOLIFIELD. So while you did not predetermine exactly what would happen, postoperation, you could determine what had happened?

Mr. CORSBIE. Yes, sir, that is correct, and it is clear that if, for instance, the yield of a device were known, the reasons for testing it would be quite marginal. So usually there is a best guess from the people who are responsible for the design, as to the yield, but there is no assurance that it would be correct and therefore where you have to construct a building or a shelter, you may or may not receive the pressure that you need in order to have a successful effect experiment. It may be too high. So much so that you simply crush your structure or it may be so low as not to give you a test.

Mr. VORTMAN. The next structure was a Navy-sponsored project and consisted of a 25- by 48-foot semicircular arch of 8-gage multiplate corrugated steel.

The foundation was at natural grade, and the arch had an earth cover about 3 feet thick over the crown with sides sloping at about 35 degress. That was on the 1955 tests.

I show the inside of it in this slide (Fig. 10). The damage to this structure was produced by a shock wave with a maximum overpressure between 30 and 35 pounds per square inch.

Mr. HOLIFIELD. That is above ground, is it?

Mr. VORTMAN. Yes. The floor of the structure is at natural grade. Mr. HOLIFIELD. And the lumber structures in there are for the purposes of your testing devices and not for any other reason?

Mr. VORTMAN. That is right. They are not structural.
Mr. HOLIFIELD. Were the ends open on this structure?

Mr. VORTMAN. No, the ends were closed. The structure was completely closed so far as blast pressure entering the inside was concerned.

The deformation of this structure is shown in a diagrammatic way in the following slide (fig. 11).

You can see the difference between the original, predicted and actual deflections.

The damage occurred to the forward side of the structure simply because a covered structure which is above ground is subject in some measure to the same diffractive and drag loading as any above-ground structure. However, earth cover allows a structure to withstand a much larger overpressure than usual because of these reasons.

Mr. HOLIFIELD. What was your pounds per square inch pressure on that structure?

Mr. VORTMAN. Between 30 and 35.

Mr. HOLIFIELD. That had no dirt over it?

Mr. VORTMAN. This had 3 feet of earth over the crown. The earth cover allows the structure to withstand a larger overpressure for these

reasons.