SR0085184 (2) - Laserfiche WebLink

Home Browse Search

SHALLOW INJECTION WELL INSTALLATION WORK PLAN arcadis.com 2022.02.15 OCC Lathrop_Shallow Injection Well Installation Work Plan_final 6 and placement for the annular materials for review. Once approved, the injection well screen and casing will be installed inside the reamed hole. The injection well will consist of 10-inch-diameter 316 stainless steel screen and SDR17 polyvinyl chloride (PVC) blank casing. SDR17 PVC blank casing is proposed to mitigate the potential for long term corrosion and fouling of the well. A minimum of a 5-foot long well sump will also be installed below the deepest well screen and constructed with same materials as the final well casing. The 10-inch blank casing will extend from the surface to the first upper screen section (to be determined; TBD) and between each identified screen interval. Centralizers will be placed above and below the screens and in 50-foot intervals above the screens. A schematic of the preliminary injection well design is presented on Figure 3; however, the number of screen intervals and their depths will be determined based on lithology encountered. 4.1.2.3 Filter Pack Installation and Grouting After the screens and blank casings have been placed inside the borehole, the well annulus materials will be added by pumping the materials through a tremie pipe. The well annulus in the screened intervals will be filled with the appropriate filter pack to a minimum of 20 feet above the upper most screen. A minimum of 5 feet of bentonite chips will be placed and hydrated above the filter pack to isolate the screened intervals and to prevent the entrance of grout into the filter pack. After the bentonite seal has hydrated, neat cement grout will be placed utilizing the tremie method in the annular space above the bentonite seal to the ground surface to seal the remainder of the borehole. Material used for sealing the casing will consist of a neat cement grout using Type II-V Portland Cement conforming to ASTM C 150. Neat cement grout shall contain no more than 5.2 gallons of water per 94- pound sack of cement. The SJCEHD will be notified before the wells are sealed so that a field inspector can witness this activity. 4.1.2.4 Well Development and Well Testing Grout will be allowed to cure for a minimum of 48 hours before development activities are conducted. The well will be developed using one or more of the following methods: air development, water jetting, mechanical surging and pumping. The specific methods and duration of well development will be determined in the field based on professional judgment. Water quality parameters including pH, conductivity, turbidity, water level and flowrate will be monitored to track and document progress during development. Development will continue until the well is free of sand, turbidity is low and has stabilized, and the specific capacity is no longer increasing significantly. Development water will be stored in frac tanks and transported to the treatment plant for disposal. Development will additionally include a shock chlorination event to ensure any bio-fouling introduced during well drilling activities is removed from the well and formation. The total amount of chlorine to be added will depend on the final constructed depth of the well, and casing volume. Any added chlorine will be purged from the well during development. Following development, a stepped-rate pumping test will be performed to assess the well capacity. The well will be pumped at least four successively increasing pumping rates, with the initial rate selected based on the approximate specific capacities observed during well development. The duration for each step will be approximately 1 hour during which pumping rate will be maintained at a constant rate. The