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Landfill Gas Migration Monitoring Well Installation Report October 2009 North County Landfill Project No. 03160203 • Before placing the probes in the borehole, the total pipe lengths and the perforation lengths were measured in the presence of Vector and EHD staff, to confirm that the lengths were in accordance with the project's Plans and Specifications. Any necessary adjustements were performed by LFG Control personnel. • The deep probe was then placed in the borehole (Photograph 17, Appendix B). Clean gravel pack was backfilled around the probe, extending six inches above the top of the probe pipe perforations (Photograph 18, Appendix B). The depth to the top of the gravel pack was measured frequently during backfilling, until the desired depth (per the Plans and Specifications) was reached. • Five feet of bentonite was placed above the gravel pack. The depth to the top of the bentonite plug was measured before placing the intermediate probe pipe. • The remaining probes, gravel packs and bentonite seals were constructed in a similar fashion, according to the design shown in Figure 3. The installation of all the probes and backfill of the borehole with gravel pack and bentonite was observed by EHD inspectors. All probes were installed to design depth and specifications, except for those which were modified in the field in accordance with Title 27 Section 20925, where sand lenses in the native soil overlapped the backfilled bentonite seals that separate the gravel pack intervals. In each instance where sand layers were encountered in proposed bentonite seal intervals, the Vector inspector first notified Public Works field division and EHD inspectors. All adjusted probe dimensions were approved in the field by EHD inspectors. Vector Engineering, Inc. • 143E Spring Hill Drive•Grass Valley, CA 95945•(530)272-2448 4