On account of the low rate of interest paid on the bonds, the city was obliged to sell the first loan at $516,529.83 less than its face value, leaving only $9,483,470.17 available for the work. Unless you take the time to visit in person some of the construction work being carried on in various parts of the city by the Sewerage Commission, you cannot realize the magnitude of the work nor the diversified engineering problems that are being solved every day. The people outside of Baltimore seem to appreciate this more than do the citizens of Baltimore, from the fact that we have more visitors from outside (some having traveled thousands of miles), than we have from the people living in Baltimore. These foreign visitors are not the merely idle or curious, but are citizens of consequence and engineers who are doing things throughout the world. Our work is most interesting on account of its complications. I will endeavor to give you a slight idea of its magnitude and difficulties. We will start on the supposition that water must flow down hill. This means that an 8-inch sewer, beginning at Forest Park, thirteen miles distant from the Disposal Plant, must continue on a constantly falling grade, which cannot be flattened beyond certain rates, ever increasing in size as sewers lead into it from valleys and hills covering an area of thirty-two square miles, in its path, crossing Peck's Branch, the B. & O. tunnel, over and under Jones Falls, the Pennsylvania tunnels, crossing over ravines, swinging around hills, tunneling through ridges, passing through narrow valleys, by the side of tall buildings, ever continuing on the constant falling grade; ever increasing in size until on reaching the disposal plant, it is large enough to contain two automobiles, one on top of the other. Two-thirds of the sewage of the city is intercepted and carried to the disposal plant by gravity; the other third is lifted by enormous pumps, each with a capacity of 27,500,000 gallons a day, from a point thirteen feet below tide to the Outfall Sewer, a height of seventy-two feet (including friction); an unusually heavy lift, especially as sewage is much more difficult to pump than water. Three of these enormous pumps are constructed and now being installed. The Pumping Station is large enough for two more, to be installed later. The foundations for these pumps have been so constructed, independent of the foundations for the building, as to absorb all shocks. The difficulty of our work is doubled on account of having to construct two systems of sewers and drains, crossing and recrossing each other in a thousand different places. The reason for the necessity of having to construct two systems is that the legislature requires every gallon of sewage to be taken into the sanitary system, to be purified before discharging it into the Chesapeake Bay or its tributaries. It is therefore of the utmost importance that we reduce the amount of sewage to be pumped and treated to a mini mum, in order to keep down the size of the sewers, the pumping plant, the disposal plant, and the unnecessary constant treating and pumping of clean rainwater. To attempt to treat all the rain that falls would break a city. Therefore, the sanitary sewers will take care of the drainage from bathtubs, kitchen sinks and toilets, the rainwater will pass off through the storm-water drains, by inlets at the corners. Now, to attempt to install these two systems of drains and sewers in the beds of streets of a city over a hundred years old, in which a mass of pipes have been laid, but in which practically no space for sewers or drains has been left, brings us face to face with a serious problem, as these sewers and drains must continue on ever-descending, regular grades and cannot twist over and under obstructions like water pipes, gas pipes and other public structures. If the sewers could be laid in the streets it would simplify matters, but as far as we can we are attempting to lay them in the alleys, which are very narrow. Unless you have had experience in building a sewer in a narrow alley, having a constant surface flow from kitchen sinks and bath tubs, lined with old brick buildings on shallow foundations, in bad condition, with leaking water pipes and sewers under the surface, you cannot realize the difficulties we have to overcome. In the low section around the harbor the troubles are even greater, as the sewers are below the tide level. The constant accumulation of ice in these alleys, caused by this surface flow, will be entirely eliminated when the sanitary sewers are constructed. The constant trickling flow in cold weather causes a rapid accumulation of ice. The city is getting its sewers constructed for almost cost, on account of the wholesale prices secured by the manner in which we have extensively advertised and let the contracts, doing a great part of the work by machinery, which is the proper way to get low prices. There has been completed, the outfall sewer, extending from Chase and Durham Streets to the disposal plant at Back River; the high level interceptor to Jones Falls; the Jones Falls sanitary interceptor, paralleling the east side of Jones Falls, passing under the new Union Station, and crossing Jones Falls at North Avenue, extending through McMechen and Laurens Streets to Druid Hill Avenue; the force-mains and the force main sewer, from the outfall sewer to the pumping station at Eastern and East Falls Avenues; the east low level interceptor, from the pumping station to Boston and Hudson Streets; the west low level interceptor, from the pumping station through President, Pratt, Light, Hill, Sharp, Ostend and Warner Streets to Alluvion Street. The majority of the sanitary laterals in east Baltimore have been laid in the streets to the curb lines. The pumping station is practically completed, with the roof on, and the chimney |