SITE INFORMATION AND CORRESPONDENCE

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Recycled Water Basin D 6561.4.003.01 Lathrop, California August 24, 2005 AUTHORIZATION REQUEST FOR WELL INSTALLATION AND Page 2 GROUNDWATER STUDY Drilling will include using 10-inch-diameter hollow stem augers. Soil samples will be collected for field soil classification only and for sampling by Hydrofocus. Well screen intervals will be from 15 to 30 feet below the ground surface (bgs). The well screens will consist of 4-inch-diameter, Schedule 40 PVC pipe with 0.010-inch-wide machined slots and flushed-threaded connections. The bottom of the well will be comprised of 2 feet of solid casing, sealed with a PVC cap. Based on grain size distribution analyses of soil samples collected during our geotechnical explorations at local sites, #2 clean, kiln-dried, silica sand filter pack material will be placed in the annular space around the well screens up to 3 feet above the highest screen slot. A surge block will then be used to consolidate the filter pack. A two-foot- thick layer of bentonite pellets with be placed over the filter pack and clean water will be added to hydrate the pellets for 30 minutes prior to sealing the remainder of the borehole with neat cement. We will extend the well casing between 2 to 3 feet above the ground surface and install a steel standpipe to protect the well casings and the data logging equipment that will be installed later. Protective crash posts will be installed around the monitoring wells. At least 48 hours after completion of the well installations, each monitoring well will be developed through purging groundwater to maximize the hydraulic connection between the well and the surrounding aquifer material and remove fine sediment. A minimum of three well casing volumes will be purged from the well using a 12-volt pump while monitoring stabilization of groundwater parameters (temperature, pH and electrical conductivity). Purging will continue during well development until flowing water is visually clear. We have assumed that the groundwater is not contaminated at the site, therefore the purge water will not be containerized. Water Level Data Collection Following well development, each shallow monitoring well will be equipped with a pressure transducer that will allow for automated data collection and efficient data retrieval. In addition, as recommended by the manufacture one additional transducer will be purchased to provide barometric corrections of the data (3 transducers total). We propose to download information from the data loggers onto a laptop computer once per month, for a period of three months following well construction to assure the data loggers are operating properly. We will then download data from the loggers once per quarter for three additional quarters. The water level data will be translated into an electronic spreadsheet format and the data for each well will be plotted versus time to illustrate changes in water levels over time. We will summarize the groundwater data quarterly using a cumulative format. Quarterly Water Quality Sampline We propose to sample the water wells on a quarterly basis with the first sampling event occurring shortly after well installation and development. Three additional events are currently proposed to provide one year of quarterly data. The following sampling protocol will be used to collect the water samples: