TWO GREAT WATER TUNNELS.
Two tunnels paralleling each other for part of their course have just been completed in New Jersey, through the Watchung mountains, above Montclair, for the supply of Newark and Jersey City. They represent an aggregate expenditure of nearly $15,000.000. That which is to convey the water from the Rockaway shed to Jersey City is the longest tunnel of any kind in the State, being 7,400 feet. The tunnel for the supply of Newark will bring the Pequan -nock water from the Cedar Grove reservoir. Although it is only one-half the length of Jersey City’s tunnel its construction presented equal difficulties, and in neither case did a single fatality take place, nor was there a shaft or air-hole driven to the sur face. Because of Contractor’ Flynn’s pecuniary embarrassments, the work was held up for six months, and a week or two ago the boring was completed, three years after it was begun, by the Hudson County funnel company, at a cost of $240,000. From above its western entrance to the Boonton reservoir, and from the eastern entrance the water is to be carried through steel pipes six feet in diameter. The excavation was made eleven and one-half feet square, and is being lined with a brick arch, backed by concrete. Its height and bottom width will he eight feet six inches. Trap rock and sandstone were the geological formations bored through. At a height of 240 feet above sea level, almost 300 feet lower than the Bonn ton reservoir, the floor of the tunnel is nearly level—the drop being only nine inches, just enough to admit 50,000,000 gallons (to be increased eventually to 70.000,000 when the second pipe line is laid) to have free run through, and even the sidewill be about halt covered. No pipes will be laid; the water will le turned directly into the tunnel from conduits at its farther extremity, with gatehouses and valves controling the (low at either end.
In the case of the Cedar Grove tunnel for the supply of Newark because of a slight curve near the western end. where the 3.000-feet-long boring comes up into the middle of what is to be the storage reservoir, the boring presented engineering difficulties which were even greater than those caused by the length and difficulties in the way of the other. Its cost, when completed, which should have been last December, will be something less than $100,000. No pipes will be laid in this tunnel, which is horseshoe in shape, and seven feet in height. Like its fellow tunnel, it is run through trap rock and sandstone. Its capacity is 70,000.000 gallons—more than enough to feed two five-foot steel mains. The water will flow from the reservoir into one end of the mile-long storage basin through a standpipe, will be aerated, flowed back to the middle or northern end to allow of sedimentation, and then sent to the city through the tunnel and a five-foot steel pipe line to be built from its eastern end at Mountain avenue, Upper Montclair. A second may one day be laid. While the boring is being brick-lined and concreted a shaft twenty-seven feet deep is being sunk into the tunnel from the reservoir bottom. Through this shaft connection is to be made with the intake mains, so that, in ease of need, water from the Pequannock mains can be sent direct into the tunnel, and so to Newark without flowing through the outlet standpipe into the reservoir and through the gatehouse and subterranean conduit across the bottom of the reservoir that is to connect the gatehouse with the tunnel. As soon as the spring is sufficiently advanced, the cast iron pipes to bring the water from the tunnel mouth on the eastern side across Mountain avenue will be begun. A few hundred feet beyond the entrance the east iron pipes to connect with the steel mains which will bring the water to Newark. In the reservoir a double conduit of two five-foot east iron pipes is to be laid from the gate house to the tunnel entrance.one to be reserved for emergency, until the growth of the city makes the use of both necessary.
The work on the Jersey City tunnel was under the direction of Charles W. Battee, of the Jersey City engineering corps. Albert Lozier was director of the Cedar Grove work.