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' Technical Revision <br /> Permit No. M-1980-183 <br /> ' Page 3 of 4 <br /> The resulting underflow is estimated at Q=5,000(0.0038)19,000=361,000 gal/day=0.56 cfs <br /> ' The proposed French drain is designed to carry a minimum of 1.0 cfs. <br /> ' The French drain will consist of a 12-inch ID perforated pipe. <br /> The preliminary engineering drawings for the French drain are attached as Sheets 1 and 2. <br /> ' Profile locations for the drain are shown as A-A' and B-B' on Figure 6 and the profile views are on <br /> ' Figures 7 and 8. The south side drain will collect ground water and transport it to the west side drain <br /> where the collected ground water will drain to the north and weep into the alluvium along the path of <br /> the west side drain. The goal of this French drain system installation is to approximate the historic <br /> ' ground water flow in this area as if the Pit 29 slurry walls were not there. Manholes will be installed <br /> at the beginning, end, and angle point of the system as shown on Figure 5. They will be used as <br /> ' cleanout access points for the French drain system and for monitoring water levels. <br /> t As shown on Figure 3 the water level in the drainage ditch on the Frei property is now at a level of <br /> 5002.9 msl which is about 2 feet below the proposed invert of the terminus of the French drain. This <br /> ' should be a sufficient gradient to allow the ground water collected in the French drain system to <br /> weep into the alluvium. Once Frei installs their drainage system, the water level in the drainage ditch <br /> ' on the Frei property should drop by about 2 feet which should enhance the weeping of collected <br /> ground water back into the alluvium. <br /> ' The plan is to install the south side drain on the Einspahr property and the west side drain within the <br /> Pit 29 property. Brannan does not anticipate any delay in getting approval for installation of the south <br /> ' side drain. However, if the west side drain has to be located within the county right of way, then <br /> there will be a delay associated with obtaining the necessary authorizations for that installation. <br /> ' Cross Sections <br /> As required by DBMS, we prepared cross sections across the Einspahr property to show the <br /> testimated pre and post mitigation water levels. The cross section locations are shown on Figure 6. <br /> The cross sections are shown on Figures 9 and 10. As shown on both cross sections the lowered <br /> ' ground water level will be sufficient to eliminate mounding on the Einspahr property. <br /> 1 <br />