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4. In the event the borehole collapses prior to placement of the concrete grout, Contractor shall take whatever steps are necessary to reopen the hole and place the seal as specified. Any such remedial action shall be conducted at the Contractor's expense. C. Installation of Casing and Screen: I. Contractor shall install well casing and screen within forty-eight (48) hours of reaching the total depth of the borehole with hole opener. Casing and screen lengths and locations will be determined by the Engineer based on results from sampling of the borehole and geophysical logging. 2. Contractor shall be responsible for supporting and anchoring the well casing in such a way as to hold it in tension during the placement of the filter pack and annular seals, during development, and when the well is completed. The bottom of the casing shall be at sufficient distance above the bottom of the hole to ensure that none of the weight of the casing will be supporting from the bottom of the hole. 3. Contractor shall place PVC casing guides at intervals along the length of the casing to ensure a minimum separation of 2 inches(2")between the casing and borehole. 4. A PVC end cap shall be sealed to the bottom of the casing string. 5. Any casing and/or screen that fails,collapses,separates,or does not allow performance of pumping test shall be required or replaced, or a new well drilled as approved by the Engineer,at Contractor's sole expense. D. Installation of Filter Pack: I. The filter pack shall be placed in the well bore annulus using a tremie pipe in accordance with AWWA A100-90,Section 6.7. Filter pack shall be placed in the levels as specified by the Engineer. The filter pack shall be placed through a feed line or tremie pipe that extends to the bottom of the casing annulus. The feed line shall be gradually withdrawn as the filter pack is placed. The rate of filter pack placement shall not exceed 1-1/2 feet per minute, as measured by a sounding line, and placement shall proceed without interruption until completion. 2. After placement of the filter pack around the screen interval. swabbing in the wall shall occur across the entire length of screen. The diameter of the swab shall be no more than '/2 inch smaller than the inside dimeter of the casing. As the filter pack material settles. more shall be added.This operations hall continue until there is no measureable settlement of the filter pack materials. Should the borehole not take the calculated volume of filter pack material,with allowances for normal loses and settling,the Engineer will have cause to reject the well. E. Installation of Intermediate Bentonite Transition Layer(s)(Annular Seals, /I'Applicahle): I. The intermediate seals of sand and granular bentonite mixture shall be installed VIN pumping the mixture through a tremie pipe to the intervals specified by the Engineer. a. These interval locations and lengths will be provided by the Engineer based on observations of the borehole. 2. The seal mix shall not be allowed to freefall more than 20 feet from the bottom of the tremie pipe to the top of the filter pack material or seal interface established from previous sounding. Each seal, or portion thereof, shall be placed form the bottom of each interval to the top, in a continuous operation. 3. The Contractor will sound the seal to verify the location of the top of the seal after each mixture has been pumped. (Jpon completion of installation ofeach annular seal.or portion thereof, no additional work will be performed until the depth to the top of that seal has been accurately determined by sounding. GRINDSTONE.TOE'S SUMMARY OF WORK REPLACEMENT WELL O1 11 00-8 J"nc 2�, 2019