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4e WELL CONSTRUCTION REPORT AND QUARTERLY MONITORING REPORT FORMER DIAMOND LUMBER-MANTECA AUGUST, 1996 The screened PVC casing consisted of 0 02-inch machine cut slots Number 2/12 sand was poured down the augers into the casing annulus, while removing approximately 2-feet of auger at a time The filter pack was placed to 2-feet above the screened interval Bentonite pellets were then poured through the augers to form an approximately 2-feet thick annular seal immediately above the sand pack A cement grout mixture was then used to fill the remaining annular space to 1-foot below grade Traffic rated, flush mounted well boxes were installed at a height of approximately 1-inch above grade to mmimize the potential for surface runoff entering the well 3.5 Well Development Each groundwater monitoring well was developed using a surge block for at least 20-minutes, and then purged of at least three well volumes of groundwater During purging, values of pH, conductivity and temperature were monitored and recorded Field logs from well development are included in Appendix C The wells were allowed to stand for a sufficient period of time for ' the groundwater to recharge to approximately 80 percent of the initial static groundwater level prior to sampling 36 Groundwater Measurements Prior to obtaining depths to groundwater measurements, the wells were checked for the presence of free product using a interface probe Depths to groundwater measurements were made using a Solinist sounder The depths were measured from the top of the surveyed well casings Groundwater level data collected to date from the site are shown in Table 1, and a copy of the ' field notes are included in Appendix D 3.7 Sampling 3.7.1 Monitoring Well Purging Each sampled well was purged using a submersible pump until at least three equivalent well volumes of water had been removed and pH,temperature and conductivity measurements had stabilized All purging and sampling equipment was washed in a tnsodium phosphate solution and rinsed in distilled water prior to each usage to reduce the potential for cross contamination between wells The pH,temperature and conductivity measurements were recorded on field data sheets, which are kept in a permanent protect file The wells were allowed to stand for a period of time to recover to a minimum of 80% of the initial water level prior to sampling Groundwater purged from the wells was placed into DOT approved 55-gallon drums The purge water will be disposed of by pumping into a vacuum truck and sending it to a recycling facility _ 3.7.2 Groundwater Sampling 1 Proper sample collection and handling are essential to assure quality data obtained from a sample Each groundwater sample, therefore,was collected using a new disposable bailer for each well 1 and placed in the appropriate laboratory prepared containers,using proper protocol 3