Water-Supply Paper Volume 470 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ... of the presence of thin flat openings between the flakes of mica, but even this is inconsequential. The crustal disturbances to which this region has been repeatedly subjected have produced many joints and fissures which constitute an intricately inter connecting network of narrow but extensive channels. Other joints are due to shrinkage during the initial consolidation of the rock. When rain falls on the ground a portion of it is absorbed and slowly percolates downward. Most of this water, when it reaches the bedrock surface, will move approximately horizontally, but some will find its way into the joint system. In the upper zones of the bedrock the fissures are far more abundant than at greater depths, where they tend to be closed by the weight of the overlying rock. The water in the joint system may be recovered by drilled wells. It is highly probable that at any specific point one or more water-bearing fissures will be intersected before drilling beyond 250 to 300 feet. If none is cut it is better to try again in a new place than to drill deeper, for it is far less probable that a fissure will be cut between 300 and 600 feet in the old place. The depth of the drilled wells in New Canaan for which data were obtained averages 173 feet and ranges from 86 to 300 feet. The yield of 14 wells averages 23 gallons a minute and ranges from 2 to 70 gallons. A few dug wells blasted down into rock also draw water from fissures, but they are not satisfactory in general. The fissures very near the surface of bedrock are very apt to fail in drought, but the blasted cavity is of some value in that it acts as a reservoir and stores some water. Till.--Everywhere in New Canaan, except in parts of the valley floors and where ledges of rock outcrop, the bedrock is eovered b...