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.� �,rs r� ..� rar F'�Fir`q: '#''� k' r.��� _rifr��i�' -�...-..��.•rm �r�`� -- � '�,r �r.�t"". " _ .` <br /> - - "iiai�na�wauinrrae�t�6�S�3d": � <br /> Groundwater Monitorinq Wells <br /> During monitoring well installation, the following procedu,:es <br /> will be used. These methods will ensure the proper identification of <br /> groundwater quality beneath the site. <br /> Groundwater Monitorin Well Installation. Three groundwater <br /> monitoring wells will be installed in the boreholes shown on <br /> Figure 1. <br /> The wells will be completed with 2--inch-diameter polyvinyl <br /> chloride (PvC) flush-threaded casing and will be screened with <br /> 0.020-inch slotted casing from 20 feet below the groundwater surface <br /> to 10 feet above the groundwater surface. Blank casing will extend <br /> from the top of the perforated section to ground surface. The actual <br /> depths of the boreholes and screened intervals of the wells will <br /> depend on conditions encountered during drilling. <br /> The wells will be packed with No. 20/40 sand from the bottom of <br /> the screen to approximately 2 feet above the top of the screen. A <br /> 2--foot seal . f bentonite pellets will be placed an the top of the <br /> sand pack. The wells will be grouted with bentonite-cement slurry or <br /> ( neat cement frc.a the top of t;e bentonite seal to the surface. The <br /> ! wells will be completed below grade, fitted with top and s atom PVC <br /> caps, and have locking covers installed. Typical well ;onstruction <br /> is illustrated on Figure 2. <br /> � 1 <br /> The monitoring wells will not be completed -yposite significant <br /> t clay zones nor will monitoring wells penetrate significant clay zones <br /> that might allow for downward migration of contamination into. lower <br /> s aquifers. <br /> Well Development and Groundwater Samples. Each well installed <br /> will be developed with an air-lift pump until clean, sediment-free <br /> water is produced from the well. The length of development time <br /> will vary depending upon field conditions. Water produced during <br /> development and sampling will be contained on site. ARCO will be <br /> responsible for the disposal of water and product collected. Prior <br /> to and following development, the thickness of free product, if any, <br /> will be gauged. <br /> Following proper development of each well, a nitrogen-driven <br /> F bladder pump or stainless steel bailer will be used to evacuate an <br /> additional amount of water before samples are taken. The amount of <br /> water evacuated will be defined by the stabilization of PH and <br /> electrcial conductivity readings for three consecutive measurements <br /> taken 5 minutes apart. When pH and electrical conductivity have been <br /> y s determined to have stabilized, water samples will be collected and <br /> - - _--submitted--to--the--laboratory—to--be----analyzed--for STX-(EPA 602), and <br /> total petroleum fuel hydrocarbons (modified EPA 8015). Sample <br /> r � <br /> i <br />