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

Till. — Overlying the bedrock of Eidgefield is till, except where it is replaced by stratified drift or where ledges crop out. When the glacier overrode New England in the ice age it scraped up the mantle of decayed rock over the fresh, unweathered rock below. It also broke off and ground away a good deal of the firm bedrock. These materials were carried along by the ice sheet in its southerly movement and were eventually deposited as till in part in de- pressions and in part over the flat surfaces of the bedi^ock. The till is an intimate and heterogeneous mixture of all this debris. Pebbles and cobbles and even large boulders are embedded in a matrix of the finer materials — sand, silt, clay, and rock flour. The till is very compact because of the great weight of the overlying ice sheet which pressed it down. Part of the water that falls as rain soaks into tlse ground and percolates downward through it until an impervious RIDGEFIELD. 99 ■/.onQ is reached or a zone of pervious material completely saturated. Some of the water will get into fissures in the underlying bedrock, s(nae of it will moxo laterally and evputually bo roiurned to the sur- face in springs or swamps at a lower elevation, and some may lie withdrawn by wells. There are in some places bodies of partly washed and stratified materials in the till, and these greatly further tlie cireulntion of water. AVells dug iu till will furnish moderata supplies of water that slowly percolates into them. Such a supply is fairly dependable in times of drought unless the well is unfavor- ably situated, as on a steep slope from which the water may drain away. Wells that intersect rather more porous lenses in the till or that reach the watcrbed or saturated zone just above tlie bedrock are apt to yield the most abundant supplies. During the later part of November, lOlG. measurements were made of 57 wells dug in till in Ridgefield. At that time 3 were dry, 13 more were said by the owuers to fail, and 3- were said to be nonfailing. The data collected are given in detail in the table on page 102 and are summarized in the following table. The wells that were dry have been neglected in computing the depth to water and the depths of water in the wells. SininiKinj of iccUh duy in till hi Hidf/ejichl. Total depth. Depth to water. Depth of water in well. Maximum . .. Feet. 33.0 9.3 ISI.8 Feet. 29.9 5.9 14.7 Feci. 12.3 Miuimnm .4 \ TPFafw ... 3.& Strntiftcd drift. — Stratified drift is the mantle rock of a con- siderable part of the valleys of Eidgefield that are underlain by the Stockbridge dolomite, and of parts of the valley of Xorwalk River. It is a well-washed and sorted stratified deposit formed in large part from till by the action of running water. It is an older alluvium and on the map (PI. Ill) it is not differentiated from recent al- luvium. The only differences are, first, that stratified drift was laid down at the end of the glacial epoch by the streams of melt water that issued from the ice sheet, whereas alluvium is more recent and is still being laid down, and, second, that stratified drift is apt to be but is not necessarily the coarser. Owing to the sorting action of the water the interstices between the larger particles are not filled by smaller particles as in till, so that the porosity is greater. Moreover, the pores individually are larger and present less frictional resistance to the circulation of v/ater. Wells in stratified drift get w^ater in the 100 GKOTJND WATER. IIST NOR WALK AND OTHER AREAS, CONN. same way as wells in till but with greater abundance. Seven such wells w^ere measured in Eidgefield. Two were said to fail, and three to be nonfailing, but the reliability of the other two could not be ascer- tained. The data collected concerning these wells are given in de- tail in the table on page 103 and are summarized in the following table : Nummary of wells duff in stratified drift hi RidgefieJd. Total depth. Depth to water. Depth of water in well. Maximum Feet. 15.9 14.0 11.4 Feet. 13.3 7.7 11.8 Feet. 5.5 Minimum .9 Average 2.7 QUALITY OF GROUND WATER. The following table gives the rCnSults of t"^'o analyses and four assays of samples of ground water collected in the town of Kidge- fielcL The waters are moderately mineralized except Nos. 15, 72, and 74, which have a low mineral content. Nos. 72 and 74 are very soft, in contrast with No. 15, which is a soft water, and Nos. 16, 48, and 57, which are hard waters. The reason for this contrast is presumably that wells Nos. 72 and 74 lie in situations where the glacier brought no debris derived from the Stockbridge dolomite, whereas the till around the other wells contains a considerable pro- portion of the relatively soluble dolomitic material. A comparison of analysis No. 15, which represents a sample from a well drilled into the dolomite, v/ith analysis No. 16, which represents a samjple from a near-by shallow well dug into the till, also suggests that the grouncl-up dolomitic material is especially siisceptible to solution and tends to make highly mineralized waters. The solid, firm dolo- mite, on the other hand, is less easily dissolved, by reason of its mechanical condition and therefore yields less highly mineralized waters. The waters represented by analyses Nos. 15, 72, and 74 are good for domestic purposes so far as may be judged from their mineral content, but the other waters are rated as fair because of their hard- ness. Nos. 15, 72, and 74 are also acceptable for boiler use, but the other waters are rated as poor because of excessive amounts of scale- forming ingredients. All are calcium-carbonate in type except the very soft waters, Nos. 72 and 74, which are sodium-carbonate waters. RlDtiKFIKLl). 101 Vhcinmil i<jiiii)i)f<itMii (IikI < Id.^si/icdtidii >,( yiouinl irdltin in h'itlffefield.'^ I Parts ]H>r million; analyzod by Alfred A. Chambris and C. 11. Kidw.ll. Nuinlici-s of analyses and assays corrcsjiond to those used on I'l. 11. J Analyses. 6 Silica (SiOs) Iron (Fe) Calcium (Ca ) Magiiesiiiiii ( Mg) Sodium (Xa) I'otiissinm (K) ( "all ■Dim le radicle (CO3) Bk-arboi.ate radicle (IICO3) ... . Snlphate radicle (SOj) ( hloride racUcle (CI) Nitrate radicle (NO3) Total d ssolved solids at 180° C. Total liardness as CaCOs Scale-formins constituents/ Foaming constituents / Chemical character I'rol lability of corrosion h Quality for boiler use Quality for domestic use.. 17 .14 IS 4.6 11 6.9 77 14 6.2 .08 114 /64 78 49 Ca-COs (?) Oood. Good. dl6 IS .40 r.7 17 12 C.4 7.0 230 22 6.8 4.1 253 /212 210 49 Ca-COa (?) Poor. Fair. -Vssays.c 0. 13 Trace. 7.2 2."d 11 3.6 /2S0 244 270 (?) Ca-CO, (?) I'oor. Fair. /22 4.S 334 27 14 /3S0 2S5 310 60 Ca-COa (?) I'oor. Fair. 'I'race. /14 .0 62 6.0 2.2 / 91 33 60 40 Xa-COs N Good. (iood. no .0 34 9.0 3.2 /73 22 30 Na-COa N Good. Good. a For location: and other descriptive information see pp. 102-103. 6 For methods used in analyses and accuracy of results see pp. 52-60. c Approximations; for methods used in assays and reliability of results ; ee pp. 52-GO. d Collected Nov. 28, 1916. e Collected Dec. S, 1916. /Computed. g Less than 10 parts per million. A Based on computed quantity; (?)=corrosion uncertain, N=noncorroslve. PUBLIC ^^'ATER SUPPLY. The Ridgefield Water Supply Co. has been serving its customers in and around tlie borough since 1900. Water ^vas first obtained from five driven wells in a svvamp a mile south-southwesl of Round Pond. These wells were GO feet deep; two were G inches and three were 3 inches in diameter. They drew moderate amounts of water from gravel, but the water was under veiy slight head and had to be lifted 50 feet. Subsequently three wells were vS.unk at the same l)Iace to depths of about 300 feet. They went through 10 to 50 feet of alluvium, 10 feet or so of clay, and finally through more than 200 feet of sand. Xo water was obtained below the cla}- and only moderate amounts above it. At present all the wells are abandoned and water is pumped from Round Pond to a steel standpipe of 188,000 gallons capacity located on a ridge 1^ miles south-southeast of the pond. There are two triplex single-acting pumps, 10 by 10 inches, driven by two 35-horse- power electric motors and working against a pressure of 75 pounds to the square inch. The water is distributed by gravity fi'om the .standpipe through 11 miles of mains to 70 hydrants and 383 service taps, of which 311 are metered. The pressure ranges from 75 to 90 pounds per square inch. Tlie 2,500 peojjle served consume on the average about 118,000 gallons a day, Roi.nd Pond is presumably 102 GROlTTs^D WATER IB NOEWALK AjSTD OTHER AREAS, CONX. fed by subaqueous springs.^ The water in the pond has heretofore been abundant, and a much larger quantity coukl be furnished. RECORDS or WELLS AKD SPRINGS. Wells dug in till in li. id fje field. No. on PI. 11. 0\vncr. Topogra- phic situa- tion. Ele- va- tion above sea level. Total depth Depth Depth to of water. 'water. Rix. Remarks. 2 Slope do Feci. 620 500 500 560 610 685 785 665 795 670 620 540 565 650 605 595 695 610 780 590 825 730 715 630 700 070 720 670 765 745 790 575 470 550 575 590 600 635 750 755 770 790 740 785 780 765 745 615 630 703 525 040 690 500 550 430 4S0 Feef. 9.4 18.5 12.7 17.9 21.6 19.2 30 25.2 13.4 12.3 22.9 15.4 24.6 25.7 13.5 10.6 23.3 21.2 25.7 24.6 21.0 22.0 24.0 10.1 19.9 13. 5 17.0 9.3 10.4 20.8 11.0 14.9 18 30.0 33.0 17.1 14.8 9.3 25.2 18.9 19.7 9.6 25.6 14.4 20.8 25.9 20.5 16.6 25.6 15.0 17.3 18.2 14.0 13.2 13.2 14.0 24.9 Feel. 5.9 14.2 7.7 11.1 14.8 13.8 'i2.'2' 13.3 23.5 24.4 11.2 13.9 19.8 19.0 24.4 10.0 19.6 21.7 20.5 9.6 17.4 12.0 10.0 6.0 8.9 15.0 9.7 14.0 3 29.9 29.8 15.5 12.4 7.0 19.4 13.3 11.7 8.0 13.3 10.3 12.5 23.5 13.6 13.3 15.5 13.6 14.7 12.9 12.9 10.6 12.1 12.7 24.5 Feet. 3.5 4.3 5.0 6.8 6.8 5.4 Dry Dry 1.2 Dry 2.2 2.1 1.1 1.3 2.3 2.7 3.5 2.2 1.3 8.6 1.4 0.3 3.5 0.5 2.5 1.5 0.4 3.3 7.5 5.8 1.9 0.9 15 0.7 3.2