MR. DONALDSON.-I have never met such a thing under rock. I believe that in Europe under this magnesian limestone they have quicksand, but we do not have any in this country. This pocket that I spoke of was where the rock had folded and had crushed itself. The fold is shown on Fig. 6. The grout will not permeate the sand, and we drilled a great many holes. We forced grout in with a booster under 500 or 600 pounds pressure. That would make a series of grout balls, and when we got through we had that sand seam packed full of these balls of grout. We did not get it entirely tight at that. Before we started in we would open up three or four holes at once and get nearly 600 gallons of water per minute and then plug them quick before the shaft was flooded. When we got through grouting we simply sunk through the sand, cut into the solid rock below, started what the Englishmen call the wedging curb, put corrugated. iron clear around the wet section, inserted drain pipes, placed the lining and left it finally as dry as this ceiling.

MR. CONNER.-From that experience would you think that the system might. be applied to quicksand such as is encountered in the Wyoming Valley?

MR. DONALDSON.-No, sir; it would not fit. If you had your quicksand in between two layers of rock as we had, where it could not get out, it might fit; but where it is a case of overburden, I do not know how you could grout that.

Dr. Chance.—Just how long has this system of grouting rock fissures been introduced?

MR. DONALDSON.-As far as my experience goes, it was introduced four years.

ago.

DR. CHANCE.-I mean abroad.

MR. DONALDSON.-The first account I could find is about eight years ago, and in that case they struck water in large quantities; they put in an elaboratesystem of pipes and did not get the water cut off at that.

DR. CHANCE. They were attempting to grout the fissures?

MR. DONALDSON.-Yes, only they tried to take it from up above, as we did at first, instead of from the bottom. I have a great respect for the European engineers, and I do not know why they did that.

Dr. Chance.—The speaker has been entirely inconsistent. He told us in first place that European engineers were far ahead of American engineers, and now he tells us that he has succeeded where the European engineers failed.

MR. DONALDSON.-I will have to modify my remarks. In soft ground work. they have us beaten.

DR. CHANCE. That is because of the geological conditions, which are different abroad from those in this country. In certain places we have similar conditions, but we have so much coal and other minerals within easy reach of the surface that we do not have to go to difficult locations, as for instance below the sea, as they do abroad.

But it seems to me that Mr. Donaldson has given us a paper of very great value. I do not know that anything like this has ever been published; if it has, I have not read it. It seems to me that it is not only interesting, but is valu

able to the engineering profession, and it is quite an achievement to grout rock crevices and lute them just as nature has luted most of our fissures of clay. The underground is generally dry after you get below the surface water, and that is due to the fact that nature has closed most of the crevices of the rock with sediment and calcareous deposits. This process of Mr. Donaldson's is a process not entirely dissimilar to that of nature, an artificial closing of the fissures so that they become impervious.

Mr. Donaldson has undertaken a hard task if he tries to persuade American engineers that a circular shaft is better than a rectangular shaft. From the point of view of first cost, he is undoubtedly right. But many other conditions must be considered by the engineer apart from the question of first cost. If a shaft requires lining, and if he decided to line it with concrete rather than with timber (for the purpose of eliminating fire risk, etc.) to remove the dangers which follow from explosion and the consequent destruction of mine timber, all right; then the idea that a circular or elliptical form is going to be cheaper is erroneous, because, depending upon the size of the cages used, in lining a rectangular shaft where the rock is fairly well able to sustain itself, the grout lining would have to be very heavy and sufficiently strong to withstand very heavy pressure. In such a shaft concrete partition can be used to divide the shaft into compartments. These will act as walls and support the lateral faces in a large shaft. A shaft having four or six compartments is a relatively long opening, and if the rock is badly fissured or requires timbering, with the square system of timbering there is no difficulty in supporting the side walls. If you attempt to support them with concrete, an elliptical form is best, provided you are not going to crossbrace. The rectangular system lends itself well to cross bracing, so it is doubtful if American engineers will come to use circular or elliptical shafts.

MR. DONALDSON.—The circular shafts certainly seem to be the correct construction where you have only one compartment in the shaft and where it is designed for carrying air. For long shafts I agree with the gentleman who has just spoken. For a 2-compartment or a 3-compartment shaft, the compromise section I sketched is cheaper than cross-bracing. Where you have a 4- or 5compartment shaft, it is a difficult question to make an ellipse out of that, because you would have to take in the whole surrounding country. I think it would be cheaper to put in an iron and concrete lining and cross-brace it in the middle, and sort of arch the ends. It is a good deal cheaper lining if you can get one continuous stretch of forms around the outside.

MR. S. M. SWAAB.-On the aqueduct, were those shafts driven on the center line?

MR. DONALDSON.-The circular shafts were driven on the center line.

MR. SWAAB. Is it not considered good practice to drive the shaft off the center line?

MR. DONALDSON.-Where there are rectangular shafts the two compartments were not quite above the center line of the tunnel. They moved it enough to get the center line away from the buntons.

MR. SWAAB.-It seems to me that if Mr. Donaldson finds he has sufficient time he has done some work in this country which I believe was not done before— we would like him to tell us about it. Of course, it is the same process as was used in Europe in driving the Alpine tunnels, but Mr. Donaldson has driven tunnels by that bottom heading method in New York, and I would like to ask him if he would not say something about that, and the typical way of working. I have been in bottom head tunnels and could not see a whole lot of advantage in that method.

MR. DONALDSON.-I agree with Mr. Swaab; I don't either, and I would not do it again.

On one section of the aqueduct it was figured they would drive the heading clear through first, working the maximum economy, as cheaply as they could, and then take the bench out. I believe where you have good hard rock it is cheaper to drive the bottom heading and slope the roof down. I know that we abandoned the method that Mr. Swaab referred to-that is shooting the roof down on timbers at the same time we were driving the heading-we went ahead with the bottom heading to the end of the tunnel and then shot the roof down on the floor and mucked it by hand. While we were taking the roof down, Rinehart & Dennis, having driven the top heading, were removing their bench. We doubled their progress, taking out twice the material. In other words, the stopping method was about fifty per cent. better than the bench method for enlarging the section, but where the two things are going on simultaneously, the method of shooting the arch down on timber is not intended for the American tunnel

man.

MR. E. E. KRAUSS.-Mr. Donaldson referred to the use of concrete for lining of tunnels against high water pressures. It would be interesting to know what proportions were used for the concrete and as to whether special measures were taken to obtain a concrete of maximum density, as I understand no waterproofing material is used in tunnel lining work of the character described.

MR. DONALDSON.-No, nothing was used.

MR. KRAUSS.-With 1-2-4 mixing?

A.—1——2—4. But we used 1-11⁄2-3 in the Hudson Siphon.

MR. SWAAB. Did you use any lime in the cement ground at all?

MR. DONALDSON.—No, but in the Pennsylvania River Tunnel I understand they used considerable English lime.

MR. SWAAB. Of course, that was just for filling up the spaces around the shield.

MR. W. C. FURBER.-I would like to ask Mr. Donaldson if he will describe in a little more detail the instance he cited where they faced the fissures in the rock, the preparation of the sleeve or concrete lining; just how was that done?

MR. DONALDSON.-Just before the Hudson Siphon was turned over to the contractor, the City forces drilled into quite a stream of water in the heading. Instead of attempting to grout off the water, they shot the cut and got a strong flow from the cavity. When we took the work this stream was flowing, and we

had to build a strong bulkhead so that grouting would be possible. We stuck a pipe into the fissure at the bottom of the cut and drained the water through it, then built a bulkhead of concrete 8 feet thick across the entire face of the heading. The bulkhead was heavily reinforced by rails set into holes drilled in the ribs. We provided additional grout pipes through the bulkhead after the concrete had set for a week, grouted all pipes at pressures up to 1,000 pounds per square inch, completely cutting off the water. When driving was resumed no water was encountered.

MR. FURBER. That grouting was sufficient to fill up the fissures, was it?

MR. DONALDSON.-Yes, we put in about three carloads of cement.

PAPER NO. 1130

THE DESIGN AND CONSTRUCTION OF THE HYDROELECTRIC PLANT AT ESTACADA, OREGON.*

BY HERMANN V. SCHREIBER

Read March 15, 1913

The extremely heavy precipitation on the nearby mountains and snow peaks, combined with the high fuel costs along the northern portion of the Pacific Coast, give us conditions very favorable for development of large hydro-electric transmission projects. Several of such projects center about Seattle and Portland, and other systems are being developed around the smaller cities.

At Portland the Columbia river, which is the largest stream in the northwestern section of the United States, breaks through the Cascade mountains and flows westward to the Pacific past Portland, where it is joined by the Willamette river flowing from the south. Both these streams and some of their branches are navigable and also provide considerable power. Flowing from the east into the Willamette river south of Portland is the Clackamas river, which finds its sources among the peaks of the Casca Range south of Mount Hood. This river, being fed from several snow covered peaks and forest reserves, has a comparatively steady flow, and because of its rapid fall and high banks offers numerous attractive power sites.

The Portland Railway, Light & Power Company, controlling the electrical market in and around Portland, having already acquired a development on the Clackamas river about 40 miles southeast of Portland with an interurban railway connection partially paralleling the streams, naturally investigated the further possibilities for development on this stream as soon as their increasing load conditions indicated that they would require more power than their existing plants could produce.

*Portion of Paper presented to the National Association of Cement Users at Kansas City, Mo., February, 1912.