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' Mr. Allan Fetters - 3 - 13 June 2007 Next Steps Ripon Farm Service needs to continue the investigation into the lateral and vertical extent of nitrate pollution in soil and groundwater at the Ripon Farm Service facility. Please provide a work plan that develops the following avenues of investigation: • Provide a vertical profile of nitrogen in soil and groundwater beneath potential source areas. • Test the integrity of the containment and stormwater collection system. • Evaluate the integrity of the on-site supply well and its seal. • Determine the influence, if any, of pumping cycles from Municipal Well 12 and the on-site supply well on groundwater movement observed at the on-site shallow wells. • Propose a means to estimate what portion of the nitrate observed in Municipal Well W-12, if any, might be attributed to Ripon Farm Service. Ripon Farm Service samples the on-site and off-site wells quarterly for nitrate, ammonium, and water surface elevation. Please add the following to the quarterly monitoring events: • The on-site water supply well should be sampled for groundwater surface elevation and nitrogen compounds. • Obtain water surface elevations from on-site wells MW-4, MW-5, MW-101 , MW-102, MW-103, MW-104, the water supply well and off-site wells RMW-1 S-R, RMW-2S, RMW-3S during the same groundwater elevation monitoring event. Regional Water Board staff will prepare a monitoring and reporting program for your review and comment, which will be transmitted under separate cover. Changes to Reports With a few modifications, the monitoring reports provided by Genesis Engineering and Advanced GeoEnvironmental could be made more useful to the reader. Genesis Engineering needs to include a column in the Groundwater Elevations table that identifies the screen interval of each well. Genesis Engineering also needs to provide a diagram illustrating the measured groundwater contours of the shallow water-bearing zone, and include the location of Municipal Well 12 on its figures. Advanced GeoEnvironmental should include at least one figure that shows the western portion of the site, the off-site monitoring wells, and Municipal Well 12. Advanced GeoEnvironmental also needs to include a table that shows the general mineral analytical data obtained. General mineral data was presented in the 27 October 2006 Limited Subsurface Investigation Report, the 11 December 2006 Quarterly Report— Fourth Quarter 2006, and the 5 March 2007 Quarterly Report— First Quarter 2007. Summary Please provide a work plan to evaluate the depth and extent of on-site pollution in soil and groundwater by 10 August 2007. Please add the water supply well to the on-site monitoring well sampling events, measure all shallow groundwater elevations at the same event, and implement the above listed modifications to regular monitoring reports. Regional Water Board staff look forward to working with Ripon Farm Service to develop answers to the questions of