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B The pea gravel shall be uniformly graded from coarse to fine with a maximum particle size of 314 inch, a maximum of 50% passing a No 4 sieve, and a maximum of 15% passing a No 200 sieve C The sand shall be uniformly graded from coarse to fine, with a maximum particle size of 318 inch, a maximum of 50% passing a No 30 sieve, and a maximum of 15% passing a No 200 sieve 202 BENTONITE SEALS Form bentonite seals placed during isolated water quality sampling with bentonite pellets PART 3 - EXECUTION 3 01 SAMPLING Execute the sampling as follows A The Contractor shall fill the test holes with native material and bentonite tablets to within five (5) feet of the depth of the bottom of the first (lowest) strata ' selected for testing Bentonite and fill material shall be installed by tremle to the bottom of the hole Said depth shall be sounded to confirm the hole has been filled to the proper level B The Contractor shall then lower a 6-inch diameter, sampling string with a twenty- foot (20') perforated pipe to the proper depth for developing the test strata After placement of the perforated pipe, the Contractor shall fill the test hole with pea gravel to a level twenty feet (20') above the top of the perforated piping The volume of gravel placed shall be measured and compared to the theoretical volume required The well shall be sounded to measure the depth to the top of the gravel pack The Contractor shall then place a ten-foot (10') minimum, impervious layer of bentonite on top of the gravel pack to isolate the test strata using a tremae pipe C The Contractor shall then develop the test strata by air lifting for a period of 24 hours or until the following conditions, as determined by the Engineer, have been met 1 Water being pumped becomes clear to the eye 2 The electrical conductivity and pH of the water have stabilized D Once these conditions have been fulfilled, water samples of the isolated zone shall be taken as described below 1 Because chemical constituents with known volatility will be sampled and tested, a 4-inch submersible pump shall be used for obtaining the water sample 2 The zone shall be pumped with the submersible pump for an additional 12 hours before a sample is taken or until the Engineer, or his designee, is satisfied that the water sample meets appropriate sampling conditions The submersible pump provided shall be capable of pumping up to 75 GPM against 300 feet of total head August 2001 Division 111 -15 Ball Park& Park& Ride Wells Ph 1