28 made of a soluble substance having low permeability and high strength for example the plug 28 may have an acid solubility greater than 70 and permeability of less than 10 md an exemplary substance is indiana limestone which is a relatively inexpensive material that is readily available in the united states and has permeability of less than 3 md in laboratory studies indiana limestone is generally composed of greater than 98 calcite which has high acid solubility additionally literature data has shown that the compressive young 39 s modulus of indiana limestone is approximately 30 600 mpa which is comparable to high strength concrete limestone with similar properties is also easily available in other countries and on other continents although the present disclosure refers to the soluble substance of the plugs 28 as limestone it should be understood that other materials having similar solubility permeability and strength may be utilized in the disclosed methods and systems in a non limiting embodiment the plugs 28 may be pre formed and secured at an end of the conduits 26 via a threaded hollow cap in other embodiments the plugs 28 may be force fit into the conduits 26 or inserted into the conduits 26 and abutted against the inside of a flange not shown on an.