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Farmington Groundwater Recharge Program STC Work Plan—Hammer Site 2.5.1. Groundwater Elevation Monitoring As mentioned previously, prior to the start of pilot recharge testing, groundwater elevations at the new monitoring well and existing agricultural well (if accessible) will be monitored according to the schedule in Appendix D to establish baseline conditions. During the pilot recharge test, groundwater elevations in the monitoring well will be monitored every 30 minutes with a pressure transducer. Monitoring will be conducted with the use of data loggers and supported with manual sounder readings. These manual groundwater elevation monitoring data will be collected weekly and recorded on the Groundwater Elevation Monitoring forms presented in Appendix F. The form includes columns for the date and time of the water elevation measurement, depth of water, field personnel, and unusual observations related to the monitoring well. It is important that the monitoring data be compiled during the tests and analyzed promptly for proper decision-making. For example, if water levels rise to within 10 feet of ground surface at the perimeter of the project, mitigation measures must be considered to prevent further rises to protect root zones in adjacent properties and/or damages to roadways, or other infrastructure problems. These measures will include one or more of the following: • Immediate cessation of the field flooding until water levels decline below 10 feet below ground surface. • Reducing the volume of water and/or total area of flooding when operations resume. • Re-operation to allow drying and decreased water levels in the vicinity of the high water table. 2.5.2. Source Water Monitoring Source water will be monitored for field parameters weekly during the pilot recharge test (Table 2) according to the schedule presented in Appendix D. It is necessary to routinely monitor the quality of source water used for recharge. Water with high turbidity causes soils to clog, which decreases the infiltration rate. Turbidity will be measured in the field and will not require laboratory analysis. Other field parameters that will be collected include temperature, pH, electrical conductivity, dissolved oxygen, and reduction oxygen potential. 2.5.3. Evaporation and Precipitation In order to obtain accurate volume measurements of recharged water, evaporation and precipitation will be monitored. Evaporation and precipitation data will be downloaded from the California Irrigation Management Information System (CIMIS) database and webpage according to the schedule in Appendix D. These data are updated daily with a CIMIS station (#166) near the City of Lodi.' The CIMIS station reports precipitation and reference evapotranspiration (ETo), which will be converted to evaporation by multiplying by the correct monthly factor derived from data from the CIMIS webpage. Precipitation is expected to be zero during the initial test period. If the testing continues into the rainy season, precipitation will be closely monitored by CIMIS station#166 and dedicated rain gauges may be installed at the test site. ' CIMIS data can be obtained at http://wwwcimis.water.ca.gov/cimis/data.jsp MWH 2-14 July 2004