Ground Water in the Norwalk, Suffield, and Glastonbury Areas, Connecticut

d Norwalk was not counted separately but was included with Stamford and Greenwich at tliis census. « For a period of 20 years. There has been growth in each period except that from 1771 to 1782. In the decade from 1830 to 1840 there was enough increase to a little more than offset the loss of population by the cession of part of Westport in 1835. In 1849 the New York & New Haven Railroad was opened, and in 1852 the Danbury & Norwalk Railroad. In the two decades from 1850 to 1870 Norwalk nearly trebled in popu- lation as manufactures became well established. The population continued to increase steadily and doubled between 1870 and 1910. It is to be expected that the growth will continue. In addition to Norwalk, South Norwalk, and East Norwalk, which are built up without break, there are four small settlements in the town. Rowayton, in the southwest corner of the town, is in large part a summer settlement. West Norwalk is on Fivemile Brook just south of the New Canaan town line. Winnipauk is a small manu- facturing village on Norwalk River 1^ miles north of Norwalk. Cranberry is a little settlement near the northeast corner of the toAvn. NOiaVALK. 85 The main line of the New '^ oik, New Ilaxon «.'v; Tlniirord IJaili'Oiid crosses the town near tlie shore oi' Lono; Island Sound and has sta- tions at Rowayton, Sonth Xorwalk, and East Xorwalk. Tlie Dan- bur}^ branch, connectino; Sonth XorAA'alk Avith Danbury, lias stations also at Norwalk and AVinnipank. Trolleys connect South Xorwalk with Darien and Stamford by way of Rowayton; East Xorwalk, Saupitnck, AVestport. and Bridgeport; Roton Point; (Jregory Point; and Xorwalk and AVinnipank. A trnnk-line State highw^ay con- nects with points east and west along the shore, and another follows Xorwalk River to Ridgefield and to Danbnry. There is automobile- stage service to Xew Canaan from Xorwalk. Post offices are main- tained at Xorwalk, South Xorwalk, and Rowayton, with carrier serAice in Xorwalk. South Xorwalk, and East Xorwalk. The out- lying districts are served by rural delivery. The principal industries of Xorwalk are the manufacture of cor- sets, shirts, silks, paper and paper goods, brass, rugs. hats, hardware and machinery, boots and shoes, Avoolen goods, lace, automobile tires, motor trucks, engines, stores, and stone and earthen Avare; ship- building: oyster fishing: and agriculture in the outlying districts. SURFACE FEATURES. Norwalk is in that portion of the Avestern highlands of Connect icr.t that lies along the shore of Long Island Sound. The inland portion of the province is a plateau sloping gently to the south-southeast, underlain by intensely folded, crushed, and injected rocks. The plateau has been deeply trenched by streams so that, although the hills and ridges rise to concordant altitudes, the topography is I'ugged. At the seaAvard margin these features persist but in a re- duced degree. Formerly the land stood higl.er relatiA^e to sea level and X'orAvalk was Avell inland, and under such conditions it dcA^eloped the topographic features characteristic of the present inland. Subse- quent depressing of the land has droAvned the XorAvalk coast. Arms of the sea extend up the A^alleys making bays of the shorter ones and an estuary of the valley of Xorwalk River. The ridges between these droAvned A^alleys are noAv peninsulas. In the heads of the bays and estuaries the Avater has but little motion, and deposits of mud haA'e been made. These are the salt marshes that form so prominent a feature of the topography of the Connecticut shore. The greatest elevation in the town, 340 feet above sea leA^el, is on the divide be- tAveen Silvermine and Xorwalk riA^^ers at the AVilton toAvn line. FiA'emile Ri\'er and XorAvalk River are through- fiow^ing streams Avhieh Avith their tributaries drain the Avest and central parts of the town. On Silvermine RiA'er. Avhich enters Xorwalk River a little 86 GEOUND WATER 1:^- jSTOEWALK AND OTHER AREAS, CONH. beloAY Winnipauk, and on Xorwalk Eiver there are se\'eral small water powers deveiopecL Tlie northeast corner of the town is drained hy the headwaters of Stony Brook which crosses into Westport and joins Saugatuck iii^'er. There are a few short brooks which drain parts of the shore zone and flow through salt marshes into the Sound. W A TER -BE ARIN G FOR M ATIO X S , /Schist and gneiss. — There are three bedrock formations in Nor- walk^— the Danbury granodiorite gneiss, which underlies a strip 2 miles long west of Fivemile E-iver ; the Becket granite gneiss, under- lying the rest of the elevated territory west of Norwalk Ei^er ; and the Thomaston granite gneiss, underlying the south margin of the town and most of the part east of Norwalk River. There is also an area of Becket granite gneiss half a mile wide and extending a mik> along the middle of the Westport boundary. The Becket granite gneiss underlies much of western Connecticut, and is composed of feldspar, quartz, and black mica which are con- centrated in contrasting light and dark laj^ers. These give the rock the banded and cleavable character typical of gneisses. There is some doubt as to Avhether this rock was originally an igneous or sedimentary rock. The minerals are those defining the granite family of igneous rocks, but certain phases are so highly quartzose as to suggest sandstone. It is possible that a very minor part of the rock is of sedimentary origin but that an extreme amount of igneous material has been added so as to give it a dominantl}' igneous character. It is a resistant rock and forms a high ridge between Fivemile Eiver and Norwalk Eiver. This ridge is bounded on the west by a valley cut in large part in Danbury granodiorite gneiss, and on the south and east by a lower area of the Thomaston granite gneiss. The essential constituents of the Danbury granodiorite gneiss are quartz, feldsi:>ar, and mica or hornblende or both. Where tlie mica is the chief dark mineral the rock approaches a true granite in com- position, but where hornblende is dominant it becomes a granodiorite. The granodiorite seems to be the variety found most commonly in the southern part of Fairfield County, according to Gregory.^ Cer- tain of the feldspar crystals tend to be much larger than the other crystals, so the rock has a porphyritic texture on which mashing has superposed a gneissoid texture. The only essential differences between the Thomaston granite gneiss and the Danbury granodiorite gneiss are that the former con- tains little or no hornblende and the porphyritic texture is less 1 Gregory, H. E., ami Robinson, H. H., Preliminary geological map of Connecticut : Connecticut Geol. and Xat. Hist. Survey Bull. 7, 1907. = Gregory, U. E., and Rice. W. N., Manual of the geology of Connecticut : Connecticut Geol. and Nat. Flist. Survey Bull. 6, p. 108, 1906. NORWALK. 87 pvoiuinent. Both are probably younger than the lieckel jirf'.nhe gneiss, lor they have been altered les.s by metamorphinnu The capacities of the three types of bedrock for carrying N\ater are substantially the same. Igneous rocks have only negligible amounts of pore bpace. Moreover, the effect of dynamic metamorphism is to reduce the porosity still more. Therefore we expect to hud and actually do fuid no appreciable amounts of interstitial >vater in these rocks. It is possible that the minute flat openings betvveen mica ilakes in the more schistose phases may contain a little water, but the.-e openings arc so small and circvdation is so retarded by friction that no valuable supply of water can be obtained from them. Open- ings of another kind do exist in these rocks and are capable of taking in. transmitting, and again giving out some ground water. These are the rather extensive joints and fissures formed in part by shrink- age of the rock and in part by the mechanical forces which have acted on the rocks. They fonn a very complicated network of intercon- necting fissures better developed near the surface of the bedrock than in depth. The base of the overlying mantle of unconsolidated rock is saturated in most places with water. This water, derived pri- marily by absorption of rain, works its way through and fills the network of fissures and may be recovered by means of drilled Avells. Detailed data concerning a number of such wells in Xorwalk are «jii\ en in the table on page 94:. The following table summarizes these data : ^^luiiiiinrii of ihiUcd ireUs in XonraJk. Maxiniiim. Miniiniim. Average... Total Depth to Depth to depth. rock. water. Feet. Feet. Feet. 250 12 20 45 SO 0 166 35 12 Yield in gallous per miniito. 7//7,_Tliere are two types of mantle rock in Xorwaliv from which water is obtained— till and stratified drift. In addition there are the deposits of the salt marshes and beacli sands, which would give only salt water. Well No. 95 (see map, PL II) is of this type. The till, which is also called boulder clay and " hardpan/' overlies the bedrock of the more elevated portions of the town. The name '^ hardpan " is descriptive of the physical properties which make it difficult to excavate. The till consists of an intimate and thoroughly heterogeneous mixture of glacial debris, which includes fragments of all conceivable sizes and shapes derived from all the varieties of rock overridden by the ice. Boulders, cobbles, and pelibles torn and scraped off the ledges were carried along by the ice sheet. They were o8 GEOUXD WATER IX ISTOE WALK AND OTHER AREAS, CONISI'.