half way up. The interceptors and pumping station are built for a million people.

In addition, a disposal plant and sanitary system is in operation covering a large part of Walbrook. Another disposal plant, with trunk sewers, covering a large section in the northwestern part of the city, is in operation.

The sewers completed and under contract, about one hundred and sixty miles, if placed end to end, would almost reach from Baltimore to New York, a portion of which are large enough to drive through in automobiles.

The Sewerage Commission will extend the sewer connections up to the property or building line, either front or rear, making the expense to the property holder of connecting up with the sewerage system a small one.

I feel safe in stating that the entire built-up portion of the city will be completely sewered and in operation in 1914, the time originally stated, provided we are allowed to continue in the rapid manner we have so far prosecuted the work.

The public has little conception of the extensive and urgent relief the installation of the storm-water drains is bringing to the city by preventing flooding, eliminating thousands of objectionable cross gutters, improvement of property, etc. If the present Commission had done nothing more than bring about the improvements caused by the building of the stormwater drains and the covering in of Jones Falls, eliminating this great nuisance, it would have performed a great and lasting service to the city. But the storm-water proposition is only a side issue compared to the sewering of the city.

The disposal plant is constructed on the unit system, in order that it may be added to as the sewers are gradually extended. The number of units at present drawing to completion are sufficient to purify the sewage of about 275,000 people, or that portion of the city which will be sewered under the present loan.

The method of treating the sewage is a follows:

At the mouth of the outfall sewer will be installed screens that will catch such things as sticks, rags, etc., which will be removed and burned. The sewage will then pass through the meter house, which will measure its flow; then through hydrolitic tanks, about 450 feet long, requiring eight hours for passage, a sufficient length of time to allow the solids to settle, the liquid passing on to an intercepting channel, to and through what we call the gate-house which distributes it to the stone sprinkling filters, located at a level fifteen feet below the hydrolitic tanks, giving a hydraulic head of sufficient force to spray the sewage over these stone beds through nozzles or jets, spaced fifteen feet apart. The hydraulic head will be controlled by butterfly valves, causing the sprays to rise and fall, varying from close to the nozzles out to the limit of fifteen feet, thus utilizing the entire

surface of the stone bed, a large portion of which would be wasted if the sprays were stationary. These nozzles will throw a square spray, thereby saving additional space which would be lost if the sprays were circular, as you know where circles touch there is a lost triangle.

The spraying of the sewage through the air is essential to the aeration and purification of the sewage. As the sewage falls on these beds it trickles down through 8-4 feet of broken stone varrying in size from 1 inch to 2 inches. The passing of the sewage through these beds forms a gelatine like film on the stones, in which certain bacteria multiply by the million, attacking and killing the injurious bacteria in the sewage. We therefore make the bacteria do the work for us by fighting each other. The sewage on reaching the bottom of these stone beds is practically pure, and is then carried by intercepting channels leading to a central channel under the stone beds, which finally delivers the purified sewage to the settling basins, requiring three hours to pass through. These settling basins are not for the purpose of causing additional purification, but to clarify the fluid, ast there are certain mineral substances in the sewage which the bacteria do not annihilate, such as is found in the Mississippi River Water, which is muddy but not injurious to drink. The sewage then passes with a drop of 18 feet through the power house, in which turbines are placed, operated by the flow of the sewage. They in turn run dynamos which generate electricity, giving us power to light the plant, run the sludge pumps and lift the clarified sewage to a water tower for flushing purposes.

In other words, by the simple gravity flow of the sewage it is purified, and power is obtained to light and run the plant at practically no cost.

It all comes down to the fact that we are getting nearer to the laws of God than ever before, which laws man cannot improve on, but can only strive to follow. For instance:

The pumps lifting the sewage from the low level to the outfall sewer, is the sun drawing the salt water from the sea to the cloud; the flow of the sewage through the outfall sewer to the disposal plant, is the cloud drifting through the air; the spraying of the sewage over the stone beds is the rain falling from the cloud to the earth; the trickling of the sewage down through the stones is the rain sinking into the earth; the purified sewage coming out into the settling basins is the spring water bubbling out of the ground, and the electric light produced by the flow of the sewage is the sunshine after the clouds have passed.

ONE SECTION OF FILTRATION BEDS, SHOWING SEWERAGE FLOWING INTO IT. ROWLAND PARK DISPOSAL PLANT.

ROLAND PARK DISPOSAL PLANT

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THE SEWERAGE SYSTEM AND DISPOSAL PLANT IN ROLAND PARK.

The system of sewage disposal, now in operation at Roland Park, is of the type known as a "Waring System" and was, in its original form, designed and built by the late Colonel G. E. Waring. In late years, however, the greatly increased area of the suburb has made necessary the construction of a much more extensive system, laid out on similar lines, under the direction of Rudolph Hering, of New York. This, in its present form, is supposed to be adequate for a population of from 5000 to 6000. The method of its installation was materially affected by the peculiar contour of the ground.

Roland Park covers an area of about 600 acres of land, forming at the center a broad ridge between two valleys. Running north from the city over the back-bone of this ridge, Roland Avenue, the main thoroughfare of the development, forms the dividing line from which the sewage of all the houses is carried by gravity east and west. The disposal field for sewage from the entire system lies across the valley on the west, near Jones' Falls. In the eastern section the sewage is collected by a number of feed pipes laid in the roadbeds, and, after flowing to a point near the bottom of the grade, is concentrated into a large concrete tank, 40 feet long, 10 feet wide, and divided into two sections. Before entering this tank, however, it passes through two brick chambers, in which a considerable part of the solid matter is allowed to settle. From time to time these chambers and the collecting tank are cleaned out, and their contents used in the manufacture of fertilizer.

From the large collecting tank, the sewage is forced up to Roland Avenue by two 5-horse-power pumps. These are electrically driven, having a capacity of 80 gallons per minute per pump, and are required to raise the sewage to a height of about 120 feet. From Roland Avenue the action of gravity carries it down the western slope, at the bottom of which, near Falls Road, the sewage from all parts of the system passes through large brick settling tanks. There are two of these tanks, each provided with a wide grating and a double screen of one-quarter inch wire mesh, which serve to break up or collect the heavier solids. From these tanks the sewage

is discharged in a virtually liquid state and is carried by gravity to the disposal fields, in the low land near Jones' Falls.

The sewage disposal field comprises an area of 34 acres, divided by earthen burms into seven beds of about one-half acre each. The surface of these beds is composed of sandy loam over a sub-drainage of drain tiles. about 3 feet deep and 20 feet apart. These drain tiles are laid on cypress boards with a slight fall to the main effluent pipe and are surrounded with broken stone, to prevent the loam from entering and choking them.