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

rubbed against one another and polished, grooved, and broken. Eventually they were embedded in a matrix composed in part of their minute fragments, in part of scrapings from the bedrock, and in part of the soil which had covered the region in preghxcial time. The weight of the overlying ice sheet helped to compact the deposit. There are, however, manj^ minute pores in the till, and it is capable of absorbing considerable amounts of rain water, which percolates downward until it reaches the surface of the bedrock. Then part of it may enter the joints of the rock, and part of it may move more or less horizontally along the rock surface. Water may be recovered from the till by means of dug wells into which it will slowly seep. The most abundant supplies are found in a zone a few^ feet thick just above the bedrock or in lenses of partly washed material which is more porous. Sixty-nine wells dug in till were visited in Norwalk early in October, 1916. Two were found to be dry, and 13 more were said to fail. The dependability of 10 could not be ascertained, but the remaining 41 were said to be nonfailing. The data collected con- cerning these wells are given in detail in the table on pages 92-93, and are summarized in the following table : Sinnmarif of uyells duff in fill in Nnrtralk. Total depth. Depth to water. Depth of water. Feet. 40.1 8.4 19.4 Feet. 29.9 5.3 15.0 Feet. 13.8 Minimum .9 4.2 ^Stratified r/H/Y.— Deposits of stratified drift are found in the val- leys of the streams of Norwalk and are shown on the map (PL II). Most of the deposits are narrow, but in the valley of Norwalk River below Winnipauk and in the vallej'' connecting Cranberry and Nor- walk there are wider areas. At the seaward margin these deposits blend into the salt-marsh deposits. For the most part they are .stream deposits, but some of the more southerly stretches may be beach sands and gravels. Whether of marine or fluviatile origin, these deposits differ from the till described above in that they are well washed and sorted and are laid in separate beds. The elimina- tion of smaller particles from the chinks between the larger ones makes stratified drift highly porous, so that it absorbs and transmits more watei'. Unless unfavorably situated, as, for example, near the edge of a terrace, wells in stratified drift yield good supplies of water. Measurements of 24 such wells in Norwalk were made and are given in the table on page 93. The reliability of 19 of these wells was ascertained. Only two were said to fail. The data con- X or. WALK. 89 coniiiiir (lie (l(>pflis of tliesc Avolls aro Mimmari/cd in the followinj^ tal.U-:' Siiiiiiiiinii (if irclls (fiiff ill .stratified drift in \orinill,-. Tol al Depth to wilier. Depth of water. Afaximiim Feel. 29.0 7.7 1S..S Fed. 5.3 1(1. 4 Fffi. ■t.O Miiiiuium 1 0 A vet uj,'u 1'. 4 «^)i:.\LnY OF <;i;oiM) watku. The subjoined table gives the results of two analyses and three assays of samples of ground water collected in Xorwalk in December, U)U). All are low in mineral content except No. -ilA, which is moder- atel}^ mineralized. Nos. i? and 4TA are soft waters, and the other three are verA* soft. All are acceptable for domestic use so far as their mineral content and chemical character are concerned. Xo. iTA will give a little trouble with formation of scale if used in Ijoilersj but the rest are classed as good for boiler use. Xo. 47 is from a well drilled into gneiss and situated very close to the dug well in till from which Xo. 4TA was obtained. A comparison of the two analj'ses will show that because of the minute character of the par- ticles composing the till, greater opportunity is given for the ground water to take mineral matter into solution. The waters are sodium carbonate in type except Xo. 47, which is a calcium-carljonate water. Cucniicdl roiitpositioii and classification of (jround tratcr-s in Xonralk." [Parts per milUon; collected Dec. 9. lOltJ; analyzed by Alfred A. Chamber? and C. H. Kidwtll. Numbers ol analyses and assays correspond to those used on 11. 11.] Snica(Si0,,) Iron(Fe) Calcium (Ca) Magnesium (Ms;) Sodium and potassium (Na+K)« Carbonate radicle (CO3) Bicarbonate radicle { HCO3) SiUphate radicle ( SO4) Chloride radicle CCl) Nitrate radicle (NO3) Total dissolved solids at 180° C. . Totalhardness as CaCO., Scale-forminj; constituents f Foaming constituents « Chemical character Probability of corrosion/. Quality for boiler use Quality for domestic use. Analyses.'' 18 .90 17 3.7 7.3 .0 44 29 5.1 Trace. 101 c58 74 20 Ca-COa (?) Good. Good. 21 11 2.j .0 127 ].j 22 1.7 180 «98 110 U8 Na-COs N Fair. Good. Trace. f 03 17 40 20 Na-COa N Good. Good. 11 .0 41 s.o 1;. 1 f S2 2S 30 Na-COs N Good. Good. «120 42 05 00 Na-COj N Good. Good. " Fnrlocatioji and other descriptive information sec pp. 92-94. '' For methods u.sedin analyses and accuracy of results see pp. 52-60. ' Appro.ximations: for methods used in assays and reliability of results see pp. 52-0<l. d Collected Dec. 1, I9u;. f Computed. / Based on computed quantity; (?)=corrosion uncertain, N=noucorrosive. VO GEOUiS^D Vv'ATER IIS^ jSTOEWALK Aj^D OTHER AEEAS^ CONE". PUBLIC Wx^TEK SUPPLIES. Separate waterworks are maintained by Norv/alk and South Norwalk. The Xorwalk system, operated by the incorporated first taxing district, was started in 18T2. There are three storage reservoirs on Silvermine River, and a distributing reservoir of 4,500,000 gallons capacity in the city at an elevation of 197 feet above sea level. The lowest of the storage reservoirs, known as tlie Grupe reservoir, is in the northeast corner of the town, of New Canaan. It is formed by a stone dam 250 feet long and 28 feet high, v/hicli stores 62,000,000 gallons. Its elevation is 297 feet a,bove sea level. The Brown reservoir, a quarter of a ruile north of the Nev7 York State line, has a capacity of 201,000,000 gallons. The dam is of the core-wall type, 1,300 feet long, 43 feet high, and has a spillwa}' elevation of 420 feet abova sea level. The Scott reservoir, IJ miles north of the State line, with its spillway 500 feet above sea level, has a capacity of 58,000,000 gallons. The dam of this reservoir is 150 feet long and 25 feet high and is built of stone. The V7ater is distributed by gravity tlirough 44. miles of mains to 229 hydrants and 2,250 service taps. The pressure is from 60 to 80 pounds to the square inch. The consumption is said by the com- missioners to average 2,500,000 gallons a day. It is said that \\e\r measurement, the records of which have been lost, indicated an average discharge of 10,000,000 gallons a day for Silvermine River. The area of the tributary drainag'e basin is about 10 square miles. The water is treated in a liquid chlorine purification plant at the Grupe reservoir.^ The South Norwalk waterworks,^ which also serve East Nor- walk, are operated by the second taxing district of the city. Con- struction was -begun in 1875, and later in that year service v/as commenced. About 189 mains were laid across the river to East Worwalk. There are at present four reservoirs and a fifth is planned. All are in the town of Wilton. Silvermine reservoir (No. 1) is on a small tributary of Silvermine River, near the southwest corner of Wilton. The overflow is at an elevation of 223 feet above sea level. It has an area of 9 acres and a capacity of 12,000,000 gallons. This reservoir is no longer in use except in emergencies, as it is below the level of the filtration plant. A mile farther up the same stream is the dam of the Wilton reser- voir (No. 2) with its spillway 266 feet above sea level. This reservoir has an area of 135 acres and a capacity of 500,000,000 gallons and is ^ Ora.1 communication from commissioners. 2 Second Taxing District of tlie City of Norwalk Sixth Ann. Rept., 1919. NOin\ALK. 91 the largest of the system. Near its lower oiul it is crossed bv a gravel causeway Avhich elTetts a j)aiiial liltratioii of the water. A short distance above the Wilton reservoir is the Huckleberry reser\oir (No. :'.)• It lias an area of 2V) acres and a capacity of 1C)lMJ()-I,0'»() gallons, and its spillway is 327 feet above sea level. On a stream Mowing through North "Wilton and aljout midway between North AVilton and AVilton is the North Wilton leserxoir (No. 4). It covers only 3 acres and has a capacity of only 2,000,000 gallons. This reservoir is used merely to divert water to the Wilton reservoir to which it is connected by a large pipe line. Its spillway is 302 feet above sea level. A fifth reservoir is planned on this stream. It will have a capacity of 800.000,000 gallons, an area of 110 acres, and a spillway elevation of 100 feet above sea level. Just below the Wilton reservoir is a double sand Hltration plant built to eliminate objectionable odor-producing and taste-producing organisms. The primary filter consists of five roofed concrete coui- i)artments, each covering about 11,000 square feet. At the bottom are lateral lines of 10-inch split vitrified tile tributary to a large central effluent channel. The underdrains are covered with 18 inches of graded gravel, above which is 3 feet D inches of sand Avith an etfective size of 0.35 to 0.38 millimeter. Before entering the primary filters the water is aerated by running it through a steel box 9 feet 3 inches long by G feet 6 inches v/ide and 4 feet deep, in the bottom of which are (>,836 holes three-sixteenths of an inch in diameter. In a drop of about 3^ feet the streams of water twist and break and the water becomes thoroughly aerated.