A map of the portion of the village ultimately to be sewered, forming plate "H" of this report. A map showing location of sewer outlet and a copy of U. S. Govt. Chart No. 271, showing shore surroundings near sewer outlet, the two forming plate "I" of this report. Two sheets of sewer profiles. Two sheets of street sewer details. Forms for proposal, sureties, specifications, contract and bond. Descriptive statement by the designing engineer hereto appended. To the Honorable State Board of Health of the State of New York: Report of L. E. Van Etten, C. E., in regard to sewer system at Larchmont Manor, Westchester county, N. Y. The area embraced by the proposed system, as shown upon maps and profiles, is but sparsely built upon, with the exception of one block on Collins avenue, next the Boston post road. This portion has recently been built upon, for business purposes, from the Boston road to Addison street, on the northerly side only. Outside of this there are but six or eight scattered buildings in the entire area shown. The section proposed to be sewered is to relieve this block principally. The engineer has advocated the best construction. of the separate system, with broken stone foundation, for ground water drainage, with flush tanks at ends of laterals, and the plans as shown were accepted by the board of trustees, subject to approval by your honorable Board. Six-inch pipe was recommended at the extreme ends of laterals, but were disapproved by the Board, and eight-inch substituted. Y-branches are to be five-inch. An important and unfortunate fact showed itself during the progress of the work, and after plans were nearly completed, which was the elevations, as given, are not the true heights above mean high tide. It seems that the elevations in use at Larchmont are all established from what was supposed to be an old Government B. M., on a dock marked H. T. 9 ft. 2 inches. Grades for all existing sewers in the old part of village, road grades and all public work, both for old and new portions, are all in these terms. An established B. M. on stone monument at Boston road and Collins avenue was shown me, and levels were begun at that point. Upon entering the salt meadows it soon became apparent that something was wrong with the mean high tide. I investigated the subject, made measurements from the supposed Government B. M., did not agree within 3.3 feet, wrote to the United States Government for information, received from them their B. M., which was not the one in question, and found 3.43 feet should be subtracted from all elevations of former levels. I would even then have changed levels to true ones, although plans were about completed for section 1, but I at once ran into the confusion of the established grades in Chatsworth avenue, Addison and Sheldon avenues and concluded it best to use those in use, making a note on all plans to subtract 3.43 feet for true heights. For the same reason I have not attempted to show contour lines on plan of system other than the contours on the village map presented. I have established sewer grades on all streets possible. Roosevelt, Summit, Concord, Vanderburgh and Franklin are projected, but not opened or graded, and no houses. Chatsworth avenue has only two or three houses, but established grades, although not as yet graded to same. The plans of sewers for this street are made upon the established grades and not on the present ground levels. It is impossible to fix sewer grades upon these ungraded streets, as will be seen by the elevations, other than to show direction of fall, and that there will be ample fall to reach entire area. At Palmer avenue there is a 15-inch main shown, simply a possible future extension for property beyond N. Y., N. H. & H. R. R., which, however, will not be required for years. It may be well to state the building upon each street at present: From outlet on Boston road to Chatsworth avenue, only one building; restricted to residence use; sewers about seven feet deep. Boston road from Chatsworth to flush tank; for business purposes; sewers about 9.5 deep; five or six buildings. Collins avenue, Boston road to Addison; business purposes; northerly side nearly built up; sewer about 10.5 feet. Addison street, three houses; residence property. Chatsworth avenue, Addison to Boston road; residence property; no houses. OUTLET The outlet as proposed is placed under section 2. All the rest enumerated above is section 1, complete, with specifications. The outlet, or section 2, is not fully worked out as to specifications and estimates, the board of trustees considering it unnecessary until the lines, grades and disposal were passed upon by your Honorable Board. The conditions of this outlet are as follows: A long length of 18-inch pipe, over marshes and salt meadow, three-fourths iron pipe supported on piles, emptying into the "gut" at the head of Larchmont harbor, at about half tide elevation. While it is recognized that this pipe might be extended to advantage in the future, still the large cost of this outlet, with the few inhabitants benefited, would at present be fatal to the contemplated improvement. This outlet is in a small bay on the salt meadows, away from all houses, and for the present would seem to be adapted for the purpose, at least until there was a large increase in the population of this area. I present a copy of the surroundings, as taken from the United States Government chart, which shows clearly the neighboring shores, although on a small scale, but the information is so clear and comprehensive, I trust your honorable Board may excuse the small scale upon which same is shown. Dated April 1, 1898. L. E. VAN ETTEN, C. E.. NEW ROCHELLE, N. Y. MT. VERNON, N. Y. Changes in sewer plans Original plans for the sewer system of the city of Mt. Vernon were approved by the State Board of Health on December 16, 1887, and appear in the 9th annual report of the Board. Subsequent additions and changes in the plans have from time to time been approved by the State Board of Health and appear in the 14th, 15th, 16th and 17th annual reports respectively. On September 26, 1898, the State Board of Health approved plans for the proposed new outlet sewer described in the following report of the designing engineer, and shown on plates "J,"” “K,” "L" and "M" of this report. Description of the proposed outfall sewer for the city of It is proposed to intercept all the sewage of the city at some point probably near the junction of Sixth street continued and the Hutchinson river and from this point to construct a 36-inch double-course sewer, circular or its equivalent in elliptical or egg-shaped, to one of three points indicated on the accompanying plans. The exact location of the line selected will be governed by the expense of construction as determined by further detailed surveys and soundings and by the land damages and other obstructions encountered. The grade proposed is .001 or 1 foot per 1000 for most of the length. In some places the grade may be steeper, but from the present levels based on Mt. Vernon city elevations taken in connection with the coast survey and state topographical charts, it is not thought that any flatter grade will be necessary. The proposed construction for the outlet, when under water, is cast-iron pipe with the Ward flexible joint. If any channels are crossed a syphon will be put in if required. At these grades or a slight modification of them a 36-inch sewer is estimated to be ample for a population of 125,000 to 150,000. Man-holes will be constructed at the usual intervals and the outlet will be carried well down into deep water at the end. The sewage will be effectually screened within the limits of Mt. Vernon. The accompanying plans are intended to show the following information: Sheet 1. (Plate "K.") The general outline of the whole system from the Bronx river to the outlet at deep water in the sound. On this sheet also the proposed Grand street tunnel route is shown, which has already been approved by the Board of Health. It also shows the proposed alternative pumping plan for the Bronx river district. By this plan all the sewage now emptying or likely, in the future, to empty into the Bronx river from Mt. Vernon, will be pumped through the iron pipe already laid into a trunk sewer now laid, which will be intercepted by the new outfall sewer to the sound. Sheet 2 (Plate "L") shows the depths and general conditions at the proposed outlet. Sheet 3 (Plate "M") shows, from the careful tests made as to tide and currents by competent engineers, the favorable conditions existing for the removal to a distance of the sewage and its discharge into a vast body of deep water. SHEDD & SARLE, Engineers A plan was also approved by the State Board of Health on September 26, 1898, for an addition to the sewer system for portions of West and Northwest Mt. Vernon, as shown on plate "N" of this report. NORTH TARRYTOWN, N. Y. Change in sewer outlet Original plans for the sewer system of North Tarrytown were approved by the State Board of Health on June 29, 1894, and appear in the 15th annual report of the Board. Subsequent changes appear in the 17th and 18th annual reports. On June 30, 1898, the State Board of Health approved a plan for a change of location of the outlet sewer; this change is shown on plate "O" of this report. |