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1 <br /> 3.3.1 Pilot Hole and Samolina <br /> tThe Contrsctor shall advance a 6-inch nominal diameter pilot hole to an estimated depth of 145 <br /> feet. During advancement of the pilot hole, 1-pound samples of the formation shall be collected <br /> � eve,r�+ 10 feet and at signif'icant changes in the foanadon as indicated by changes in drilling <br /> characteristics or cutdngs. Samples shall be put in standard sediment sample bags and delivered <br /> to the Engineer. <br /> � Of primary importance is to identify the extent and characteristics of the coarse sand and gravel <br /> layar f�scroen placement Tlu Connactor shall prepare a log of the pilot hole that idendfies <br /> � the extent of the coarse sand and gravel layer, and other significant layeis in the drift aquifer. <br /> The log shall be submiued as soon as poss�ble to the Engineer, The Contractor shall also submit <br /> the samples in the area to be sc�ened to the well scraen manufacwrer for analysis and screen <br /> � siu recommendation. The analysis results and recommendations shall be submiued W the <br /> Engineer fa approval. <br /> � 3.3.2 WellInstallation <br /> � The Contractor shall ream the pilot hole to a minim�un of 10.6 inches diameter borehole using <br /> drilling fluid composed of potable wai�ea with the minimum bentonite necessary to stabilize the <br /> borehole. <br /> iThe Conuactor shall assemble and center the 6-inch nominal diameter casing within the borehole <br /> using centering guides with a minimum spacing of 40 feet The casing shall extend from at least <br /> � 1-feet above g�rade to the bottom of the borehole. All welding shall be in accordance with <br /> AWWA C206. <br /> ' Immediat�ely aft,a installation of the 6-inch casing,the Contractor shall flush the bentonite firom <br /> the borehole by pumping potable wat�er tlu�ough the base of the casing up the annular space. The <br /> screen assembly shall be centered with centering guides at the bottom of the well within the 6- <br /> , inch casing. 'I�►e casing shall then be pulled back to expose the full length of the screen. <br /> The annular space between d�e casing and the bamehole shall be sealed as required by Section <br /> � 4725.3400, 4725.3800� and 4725.4100 of the Minnesota Water Well Construction Code. Any <br /> uncollapsod annular space shall be grouted with neat cement using a tremie pipe to p�mp the <br /> � grout under pressure from the bottom up in orn continuo�s operation. The Contractar shall insure <br /> that no grout reached the screened poriion of the borehole. The Contractor shall verify that the <br /> borehole has collapsed to kast 10 fcet above the screen or add an appropriate filter material tp <br /> ' insore the aanular space is filled to this level. <br /> 3.3.3 Temvorarv Caooina ' <br /> � At all ames during conswcdon the Contiactor shail pr�tect the well in a satisfactary manner w <br /> prevent tampering with the well or entiance of foreign matter inw i� A temporary cap shall be <br /> 1 installed over the well at the end of each day's work and wt�never the driller leaves the site. <br /> The temparary cap shall be fumly fued w the casing. Upon completion of well development <br /> , TS-3-S <br /> , <br />