The Croton aqueduct commissioners, having removed the earthen core-wall—about one-fifth of the new Croton dam—it was found that the foundation on which the new masonry work was to rest consisted of disintegrated limestone, and that, even after excavating to a depth of 115 feet, the material necessary for a solid foundation has not yet been reached. It is, therefore, found that the enormous mass of masonry already built may be resting on material equally treacherous.

Chief Engineer W. R. Hill has submitted the following report on the subject, under date of May 8, 1903:

To THE AQUEDUCT COMMISSIONERS, Gentlemen : On March 30 of this year, I called to your attention the character of the natural foundation disclosed as underlying the core-wall at the south end of the new Croton dam, which is in process of removal, prior to the substitution therefor of the solid masonry construction recommended by me shortly after my appointment as chief engineer. In that report I stated that the natural limestone foundation was more or less disintegrated, and gave every evidence of being in the process of further disintegration, and that the softer portion would quickly absorb water and could be easily and completely crushed in the hand to the form of sand. On April 3, in Report No. 539, I stated that, after receiving an official report from the division engineer on the subject, I would recommend that the services of competent geologists be obtained to make a report upon the character and probable extent of any soluble and shattered material found under the core-wall, gatehouse, and in the foundation pit, and also upon the character of the rock upon which the said extended masonry dam will be founded. At your meeting on that day you approved of my recommendation, and authorised and directed me to invite Professor James Furman Kemp, of Columbia university, and Professor John J. Stevenson, of the New York university, geologists, to give their opinion upon this subject as suggested. On April 30, I transmitted to you, in accordance with your resolution of April 3, two reports from Pro lessors Kemp and Stevenson, dated April 16 and 30. respectively. In these reports the insecure and unstable character of the formation underlying the core wall is shown. In certain locations it is stated that the material was found so soft that it “runs with water like sand,” and that it is uncertain how far down the disintegration may have penetrated, —depending largely upon geological conditions in the past. They find the condition of the foundation of gatehouse No. 1 and the adjoining portions of the old aqueduct as “deserving very serious consideration” These last mentioned portions of the structure are south of, and adjoining the core wall before mentioned, which is now partly removed. In my weekly report to yon. dated May 5, I stated that the foundation had been investigated to a depth of forty-five feet below the base upon which the core-wall stood, and that at that depth no improvement had been shown in the character of the material. As a result of these investigations it may be necessary to remove and reconstruct gatehouse No 1 and small portions of the adjoining sections of the old aqueduct, and to make further geological and engineering examinations. The conditions to which I call your attention do not necessarily involve the stability of the main portion of the dam, records show the existence of two narrow seams of softer material than the surrounding rock, which were examined and treated before its construction was begun. There may be leakage under the masonry, but there is no evidence of it. and the investigation suggested will set at rest any doubts on this point. In view of the$e facts, and considering the importance of the engineering work involved, I recommend that the aqueduct commissioners appoint a consulting export engineer to advise with me in such investigations and upon all future questions arising in the construction of the new Croton dam. Yours respectfully.

W. R. HILL, Chief Engineer.

In accordance with Chief Hill’s recommendation, the aqueduct commissioners have appointed Professor William H. Burr, of Columbia university, expert engineer, to advise the commissioners and consult with their chief engineer on the whole subject involved in the report.

If the New York syndicate which was reported (apparently without due authority) to have been granted permission to lease the waterworks of Pittsburg. Pa., for fifty years, had carried out its intentions, it would have furnished the city with distilled water, installed meters, and paid the municipality at least $500,000 a year for operating the water system.


No posts to display