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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 4 • We will collect filtered and non-filtered groundwater samples to allow for assessment of potential aquifer matrix effects on groundwater chemistry. • Non-filtered groundwater samples will be collected using a disposable polyethylene bailer for each monitoring well and decanted into pre-cleaned laboratory sample containers. • Filtered groundwater samples will be collected using a disposable polyethylene pressurized bailer. The collected sample will then be passed through a 0.45 micron filter in the field and decanted into pre-cleaned laboratory sample containers. • All samples will be placed in an ice-cooled chest for transport under a documented chain of custody to the appropriate analytical testing facility. The water quality samples will be submitted for the analysis to Severn Trent Laboratories (STL) in Pleasanton, California. Samples will be analyzed for a suite of general minerals and inorganic chemicals. • The general minerals suite include filtered analysis of ammonia as N, bicarbonate alkalinity, bromide, carbonate alkalinity, chloride, fluoride, hardness, methylene blue activated substances (MBAS), nitrates + nitrite as N, pH, phosphate, sulfate, sulfite, total alkalinity, total dissolved solids (TDS), specific conductance (EC), total Kjedahl nitrogen (TKN), total nitrogen, total/fecal Coliform organisms, and trihalomethanes including chloroform, bromodichloromethane,dibromochloromethane,and bromoform. • The metals suite includes filtered and unfiltered metals analyses of aluminum, barium, boron, calcium,magnesium,iron, chromium, copper, lead,manganese,potassium,sodium,and zinc. Rpports will prepare an installation summary report and quarterly groundwater sampling reports that include water quality sampling results presented in data tables, a well location map, and a sketch map describing water level data for each quarter. Quarterly reports will include quarterly and cumulative data of all sampling parameters and interpretation of analytical data. Discussion and analysis will be focus on baseline data compared to potential effects of the wastewater sprayfield. Each of the quarterly reports will include a groundwater plot for each well's data and figures to illustrate the groundwater flow direction and gradient calculated using selected water level data. SCHEDULE We plan to complete the monitoring well installation within approximately 4 weeks of receiving formal approval of this work plan. Reporting and continued monitoring efforts for the groundwater study will be performed over the next year.