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<br /> <br />~ <br /> <br />~ <br /> <br />... <br /> <br />". <br /> <br />--- -" <br />------ <br /> <br />~ <br /> <br />.. <br /> <br />.~ <br /> <br />... <br /> <br />~ <br /> <br />.., <br /> <br />Individual sewage disposal systems, If Improperly located. designed, or <br />maintained, can cause contamination of ground and surface waters. In both of <br />the cases Illustrated. Insufficiently treated household effluent Is <br />contaminating waters used locally. On the left, the effluent reaches a sti-eam <br />due to thin. permeable gravels lying over Impermeable shale. On the right. a <br />homeowner unknowingly Is pollutIng his own well water due to the flow of <br />contaminated water from the septic system through the rock fractures. <br /> <br /> <br />UNCOf,,\'FINEJ) AQ.UII="E1L <br /> <br />. . . .: . <br /> <br />Th I 5 d I agrammat I c sketch shows common groun d water cond 1 t i on 5 <br />found in Colorado. Well "Aft, located near a stream <br />penetrates the water saturated sands and gravel. The ground <br />water Is recharged prlmar! Iy by the stream and irrigation If <br />the area Is agricultural. Water yields from this unconfined <br />aquifer can be as great 85 2,000 gallons per minute and the <br />ground water table may be only a couple of feet below the <br />ground surface. Well "B" Is located In older sand and gravel <br />on a stream terrace above the present stream. The ground <br />water levels and recharge are primarily the result of <br />precIpitation, runoff, and lawn Irrigation in the <br />subdivision. Notice the mounding of the ground water table <br />under the houses. Yields from this well will be less than <br /> <br />22 <br /> <br />TE.-p..ll..AC.E <br /> <br /> <br />, ',-:-.-". <br /> <br />"'P.E1i:C".i:D 'WATE.1t. TABL.L <br />G'R,.OU1-l.l) WATER. ThBU <br /> <br />,.~'.:-""~::::.!. <br /> <br />IMPER.MEAB\...E BE:n'!<<>CK.._ __ <br /> <br />.' ',' <br /> <br />..' .' <br /> <br />'," .- <br /> <br />..' -. <br /> <br />.;..... ..':' . '.. ..... ' <br />... .... " <br />C6~I=INE.D ActlJIF.Ef:I..:. <br /> <br />'.' <br /> <br />.' , <br /> <br />. ". . <br /> <br />.: : " :.......:::.:.-. ,:'.:.:. <br /> <br />. ,.,'.' <br /> <br />..' ',' <br /> <br />from ItA" because of a smaller saturated thickness and lower <br />permeabl I Ity of the aquifer. <br /> <br />Well "ell Is located on an upland surface characterized by <br />several feet of weathered bedrock at the surface. The wel I <br />penetrated this slightly more permeable layer before passing <br />through the impermeable shale bedrock Into a confined <br />sandstone aquifer. The ground water in the sandstone may be <br />recharged many mi les away and thus is susceptible to <br />overutll izatlon without the ability to fully recover. The <br />water may be artesian, which means it wi II rise in the well <br />above the top of the aquifer. Yields from this type of <br />aquifer are highly variable. <br />