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Central Valley Regional Water Quality Control Board 6793.4.001.01 North Lathrop Properties May 20, 2005 WORK PLAN FOR GROUNDWATER STUDIES Page 3 Laboratory Testine Selected soil samples from our exploratory locations may be tested in our laboratory to determine moisture contents, density, sieve analysis, and hydrometer testing for this project. Additional soil samples may be collected for chemical analysis. These 2-inch by 6-inch brass tubes will be sealed using Teflon sheets secured by tight-fitting plastic caps. The soil samples will be labeled to indicate a unique sample number,time and date collected, sample location, and sampler's identification. Samples will be preserved in a chilled cooler during transportation to Severn Trent Laboratories, Inc. (STL) in Pleasanton, California with a completed chain-of custody document for analysis. Survevine The services of a licensed land surveyor will be retained to establish horizontal coordinates and elevation data for each of the five wells. Elevation data provided by the surveyor will include elevations for the top of well casing, the top of the concrete monument for the well, and the ground surface at the well. We will request the surveyor tie the survey of the wells to the nearest documented benchmark to establish elevation control. 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. 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 SamnlinQ We propose to sample the water wells on a quarterly basis starting the first quarter after the wells have been developed. The following sampling protocol will be used to collect the water samples: • The groundwater depth in the monitoring well will be measured to calculate the number of well volumes required for purging. • The wells will be purged using a 12-volt pump while monitoring stabilization of groundwater parameters (temperature, pH and electrical conductivity). The pump will be decontaminated between each well sampling.