WORK PLANS - Laserfiche WebLink

Home Browse Search

r a. j i Project No. 58100-06-30 July 25, 1995 Page 4 I shall act as the Task Order Manager and will be responsible for signing the final boring logs. Monitoring Wells • Install groundwater monitoring wells in any of the borings in which groundwater is encountered. The groundwater monitoring wells will be constructed using 4-inch diameter. polyvinyl chloride (PVC) casing. The lower portion of the wells will be constructed using 20 feet of 0.020-inch slotted screen PVC casing. A filter pack consisting of No. 3 monterey sand will be placed around the screen from the bottom of the boring to an elevation of two feet above the screen zone. • A surge block and intermittent groundwater extraction will be performed to densify the sand pack and to remove sediment prior to placement of a two foot thick seal consisting of hydrated bentonite chips. Above the seal a mixture of bentonite powder and cement will be,placed to within two feet of grade.level. A traffic-rated security wellhead cover set-in a concrete pad will be used to complete construction. The groundwater monitoring wells will be constructed as shown in Figure 3 - Typical Groundwater Monitoring Well Construction Detail. i • A Iminimum of 24 hours after well construction, the water level will be measured in the well(s) followed by subsequent purging and sampling. Well purging will typically consist of the removal of three well volumes of groundwater within the well casing prior to the collection of a groundwater sample. During purging, the pH, temperature, and electrical conductivity of the groundwater will be measured. The wastewater generated during purging activities and sampling activities will be stored in labeled 55-gallon drums and left onsite for proper disposal. • Obtain one groundwater sample from each groundwater monitoring well. The sample(s) will be obtained using a disposable Voss polyethylene bailer,placed in laboratory-provided sample containers, labeled, chilled, and delivered to an analytical laboratory following standard chain-of-custody procedures. • Submit the groundwater sample(s) obtained for testing for TPHg and TPHd following EPA Test Method 8015 modified, and BTEX following EPA Test Method 8020. • Provide quality control/quality assurance (QA/QC) procedures during the field activities. These procedures will include cleansing/rinsing of the sampling equipment prior to each sampling effort and providing chain-of-custody documentation for each sample collected and transferred to the laboratory for analytical testing. • Survey the top of casing elevation(s) for the groundwater monitoring well(s) relative to a fixed, assumed elevation at the site or a benchmark located within the vicinity (500 feet) i