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Task 2: Drill Exploratoy Soil Borings and Install Groundwater Monitoring Wells <br /> To investigate the lateral extent off petroleum hydrocarbons in the soil and, <br /> groundwater, the iegddlhonal exploratory soil;boring`s will be drilled using a truck <br /> mounted,CME 75 drilling rig equipped with 8-inch-diameter hollow-stem augers. <br /> Soil samples will be collected at 5-foot intervals and at significant stratigraphic . <br /> changes beginning at 5-feet below-grade and continuing to,the total depth of the <br /> borings. Samples will be collected from a split-spoon sampler lined with stainless <br /> steel tubes and;logged in the field'.by a qualified geologist or engineer using the <br /> f: Unified Soils Classification'System Each sample will also be field screened using a <br /> photo-ionization detector or combustible gas indicator to assist in,selecting.the <br /> samples for laboratory analysis. The samples-selected for analysis will be sealed . <br /> F airtight with Teflon or aluminum sheeting, plastic caps, and adhesive tape, and <br /> placed immediately into a cooler containing blue or dry ice. <br /> The wells will be installed and constructed based on site-specific hydrogeologic <br /> conditions and the nature,of contamination encountered.' The borings will be < <br /> converted into 2-inch-diameter groundwater monitoring wells to a depth of <br /> approximately 10 to 15 feet below the top of the first saturated zone: The wells will <br /> be constructed using 2-inch-diameter, Schedule,40, polyvinyl chloride casing with <br /> 0.010-inch perforations, and the associated filter pack. An approximately 1-foot- ; <br /> thick bentonite spacer will be installed above the sand pack, and the remainder of- <br /> I the annulus will be sealed with Portland Type I/Il neat cement. The top.of each <br /> well will be secured with a watertight locking cap and utility box finished flush <br /> with the-ground surface.. The locations of the proposed monitoring wells,are <br /> I shown,in Figure.1. . <br /> Task 3- Develop Sample and Survey Groundwater Monitoring Wells <br />` Well development will be performed to: (1) consolidate and stabilize the.filfer pack;' <br /> (2) optimize well production; and (3) reduce the turbidity of subsequent <br /> groundwater samples. The proposed wells'will be developed during drilling before <br /> 'v installation of the bentonite spacer and neat cement seal. Development will <br /> continue to a maximum of 10 saturated well volumes or.-until the groundwater is <br /> relatively free of sediments.-- <br /> All <br /> ..-All the wells at the site will be sampled a minimum of 72 hours after well. <br />' development and installation of the neat cement seal. Before sampling, the water <br /> L `y level an each well will be measured, and the-wells will be observed for the presence. <br /> of free product or sheen. The wells will then be purged to allow groundwater <br /> t representative of the aquifer to enter. Purging will be accomplished using a bailer <br /> or pump so as not to agitate the groundwater or expose it to air. 'Purging will <br /> continue until a minimum'of 3 and a maximum of 10 saturated well casing <br /> volumes have been evacuated and indicator parameters have stabilized. Indicator <br /> parameters will be pH, temperature, and specific conductivity. Stabilization of the <br /> parameters will be determined when they vary no more"than the following values:, <br /> ,1013601/042793 �2 <br /> t ALISTO ENGINEERING GROUP <br />