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E PpU1N N THOMAS R. FLINN DIRECTOR c )v -6 THOMAS M. GAU CHIEF DEPUTY DIRECTOR MICHAEL SELLING DEPUTY DIRECTOR STEVEN WINKLER DEPUTY DIRECTOR ROGER JANES BUSINESS ADMINISTRATOR June 8, 2010 P. O. BOX 1810 - 1810 E. HAZELTON AVENUE STOCKTON, CALIFORNIA 95201 (209) 468-3000 FAX (209) 468-2999 www.sjgov.org/pubworks Mr. Todd Del Frate ENVIRONIIEN I HEALTH California Regional Water Quality Control Board PERMIT/SERVICE Central Valley Region 11020 Sun Center Drive, #200 Rancho Cordova, California 95670-6114 SUBJECT: LYSIMETER STATUS NORTH COUNTY RECYCLING CENTER AND SANITARY LANDFILL Dear Mr. Del Frate: Following is a report on the condition and operational status of the lysimeters at the North County Recycling Center and Sanitary Landfill. All lysimeters were evaluated, including lysimeter VZ -1 through -3 which are reported as dry (Figure 1). Although our investigation originally focused on the lysimeters, inspection of construction drawings for Module 3 (installed in 1995) revealed the addition of a secondary leachate sump riser beneath the leachate sump, similar to that of recently -installed Module 4. The upper end of this riser has apparently been buried for over a decade. The unavailability of this riser was not noticed because it was not a point of compliance. We intend to locate and put this riser into service to monitor the liquid level in the secondary sump (if any) as we now monitor the secondary sump of Module 4. Lysimeters Evaluation of the lysimeters is based on the field data collected semi-annually. Although previously not discussed in the body of the text, this data is included in each groundwater and surface water quality report. The purpose of these lysimeters is to monitor for liquid leaking from the landfill liner. In pursuit of this, with the exception of VZ -1, they are installed beneath the liner, and are not subject to percolation of rainwater from above. Considering the dry climate at the site, it expected that no liquid would be collected from the lysimeter unless the liner was leaking, except at initial installation where the sampling tip is installed in a silica sand slurry, if the lysimeters were functioning properly (Figure 2). Normal sampling is according to the following three steps: 1. Vacuum (approximately 70 centibars, or 10 psi) is applied to the sampling tip. This applied vacuum is recorded, and the sampling tip is left overnight with this vacuum. This vacuum pulls free water from the surrounding soil, if any is present. 2. The next day, the vacuum is again recorded. The sampling tip is then pressurized, and any water collected over night is discharged. 3. The moisture content of the soil, as indicated by the conductivity of the moisture sensors, is also recorded.