WORK PLANS - Laserfiche WebLink

Home Browse Search

San Joaquin County Environmental Health Department 5044.000.016 River Islands— Levee Relief Wells November 11, 2022 WORK PLAN FOR RELIEF WELL INSTALLTION Page 2 Filter Pack Based on the anticipated grain size of the soil within the proposed relief wells, #3 8x20 clean sand filter pack material will be placed in the annular space around the relief well screens to a minimum of 2 feet above the highest screen slot. The filter pack will be pumped as a water-filter pack slurry using a gravel pump. Tremie method will be used for placement of filter material to maintain a continuous flow and reduce segregation during placement. After the tremie pipe has been lowered to the bottom of the hole, filter pack material will be pumped as the tremie pipe is raised. The filter pack will extend about 2 feet above the top of the screen and the entire screen interval should be swabbed to help consolidate the filter pack material. Top Seal The top seal will consist of a bentonite layer above the filter pack and a sand-cement slurry.A layer of bentonite chips, at least 1 foot thick,will be placed on top of the filter pack material after consolidation. The bentonite should hydrate for at least 1 hour. Each well will be completed with a top seal of sand-cement slurry mixed in accordance with the California Well Standards: sand-cement shall be mixed at a ratio of not more than 188 pounds of sand to one 94-pound sack of Portland cement(2 parts sand to 1 part cement, by weight)and about 7 gallons of clean water,where Type I or Type II Portland cement is used.This is equivalent to a`10.3'sack mix.The sand-cement slurry will be pumped through a tremie pipe installed to 1 foot above the top of the bentonite seal. It may be practical to install a temporary 12-inch-diameter surface casing to a depth of approximately 12 feet prior to drilling the 10-inch bore and pour several top seals at one time using a ready-mix delivery truck. Depending on the final wellhead below-grade connections, it will be prudent to leave the top of the cement slurry about 3 feet below grade. After final wellhead below-grade grade connectors are in place, the remaining space will be filled with additional sand-cement slurry, as described above. The top of the well casing will be fitted with a check valve to prevent water from entering the well from the top. The valve will fit inside the well casing and sit flush on top of the casing with a gasket to prevent leakage. Based on our conversations with our client, we understand that a manhole or vault will be installed at each well. The vault size should accommodate routine future access to the well casing for inspection and maintenance, including well rehabilitation. See the Relief Well Details(Figure 3)for more information regarding well construction. SCHEDULE We plan to begin well construction beginning December 5, 2022, pending approval of this work plan and favorable weather. If you have any questions or comments regarding this letter, please call and we will be glad to discuss them with you. Sincerely, Q�pFESS/O ENGEO Incorporated ��` �,`IE HA"o <1c� No. 2804 /aso:ndore ZSteve Harris, GE �q TECHN��o��P OF C ALA js/sdh/ar Attachments: Figures 1 through 3