Ventilation of underground porosity storage reservoirs

Abstract

An underground porosity reservoir includes substantially impermeable barriers and an aquiclude surrounding a volume of alluvial deposits for storing water within the pore spaces of the alluvial deposits. A conduit positioned below a surface layer of the reservoir includes an interior volume that communicates with the pore spaces of the alluvial deposits. An air vent connects the interior volume of the conduit with atmospheric air above the reservoir and allows air to pass to and from the pore spaces of the reservoir. Ventilation of the porosity reservoir provides pressure-relief during reservoir filling operations (when the incoming water would otherwise cause an increase in air pressure within the reservoir), and further provides a vacuum-break as water is extracted from the reservoir (i.e., air from the conduit enters the pore spaces as the water is extracted).

1 . A method for ventilating an underground porosity reservoir, wherein the reservoir is formed by one or more substantially water-impermeable barriers and an aquiclude, and wherein water is stored within pore spaces of alluvial material contained within the reservoir, the method comprising:
 positioning a conduit below a surface layer of the reservoir, wherein the conduit includes at least one opening so that an interior volume of the conduit communicates with the pore spaces of the reservoir; and   providing substantially atmospheric pressure to the interior volume of the conduit.   
   
   
       2 . The method according to  claim 1 , wherein the conduit comprises a perforated pipe. 
   
   
       3 . The method according to  claim 2 , wherein the step of positioning the perforated pipe below a surface layer of the reservoir further comprises:
 forming a trench through the surface layer and into the alluvial material;   placing coarse bedding material within a bottom portion of the trench;   positioning the perforated pipe atop the coarse bedding material; and   filling the remaining portion of the trench with coarse bedding material and backfill material.   
   
   
       4 . The method according to  claim 1 , wherein the step of proving substantially atmospheric pressure to the interior volume of the conduit comprises:
 connecting a first end of an air vent to the conduit so that an interior volume of the air vent communicates with the interior volume of the conduit; and   extending a second end of the air vent above a top surface of the reservoir to provide substantially atmospheric pressure to the interior volume of the air vent.   
   
   
       5 . The method according to  claim 4 , further comprising:
 filling the reservoir with water so that air entrapped within the pore spaces of the alluvial material is forced upward as water fills the reservoir; and   allowing the entrapped air to enter the conduit from the pore spaces of the alluvial material and escape the reservoir through the air vent.   
   
   
       6 . The method according to  claim 4 , further comprising:
 extracting water from the reservoir so that a partial vacuum is formed within the pore spaces of the alluvial material as water is removed from the reservoir; and   allowing air to enter the reservoir through the air vent and the conduit in order to substantially eliminate the partial vacuum formed in the pore spaces of the alluvial material.   
   
   
       7 . The method according to  claim 4 , further comprising:
 substantially enclosing the second end of the air vent to prevent contaminants from entering the air vent.   
   
   
       8 . The method according to  claim 4 , further comprising:
 positioning a plurality of conduits and attached air vents within the porosity reservoir.   
   
   
       9 . The method according to  claim 1 , further comprising:
 forming an extraction well that extends from the surface layer down to a bottom portion of the reservoir; and   positioning the conduit to run adjacent to the extraction well.   
   
   
       10 . An underground porosity reservoir for storing water in alluvial deposits, the reservoir formed by one or more substantially water-impermeable barriers and an aquiclude, the reservoir including:
 a conduit positioned below a surface layer of the reservoir, wherein the conduit includes at least one opening so that an interior volume of the conduit communicates with the alluvial deposits of the reservoir; and   means for providing substantially atmospheric pressure to the interior volume of the conduit.   
   
   
       11 . The porosity reservoir of  claim 10 , wherein the conduit comprises a perforated pipe. 
   
   
       12 . The porosity reservoir of  claim 11 , wherein:
 the perforated pipe is positioned within a trench that is formed through the surface layer and into the alluvial deposits of the reservoir; and   a coarse bedding material surrounds the perforated pipe within the trench to enhance air transfer between the pore spaces of the alluvial deposits and the interior of the perforated pipe.   
   
   
       13 . The porosity reservoir of  claim 10  wherein the alluvial deposits define pore spaces for storing water within the porosity reservoir, and wherein the interior volume of the conduit communicates with the pore spaces of the alluvial deposits within the reservoir. 
   
   
       14 . The porosity reservoir of  claim 13 , wherein the means for providing substantially atmospheric pressure to the interior volume of the conduit comprises an air vent having a first end connected to the conduit and a second end extending above a top surface of the reservoir so that an interior volume of the air vent communicates with the interior volume of the conduit and with atmospheric air above the reservoir. 
   
   
       15 . The porosity reservoir of  claim 14  wherein:
 the reservoir includes a recharge well for filling the reservoir with water; and   the conduit and air vent provide a path for air entrapped within the pore spaces of the alluvial deposits to escape the reservoir as the reservoir is filled with water.   
   
   
       16 . The porosity reservoir of  claim 15  wherein the conduit is positioned to run adjacent to the recharge well. 
   
   
       17 . The porosity reservoir of  claim 14  wherein:
 the reservoir includes an extraction well for pumping water out of the reservoir; and   the air vent and conduit provide a path for air to enter the reservoir in order to substantially eliminate a partial vacuum formed within the pore spaces of the alluvial deposits as the water is pumped from the reservoir.   
   
   
       18 . The porosity reservoir of  claim 17  wherein the conduit is positioned to run adjacent to the extraction well. 
   
   
       19 . The porosity reservoir of  claim 14 , further comprising a plurality of conduits and attached air vents positioned within the porosity reservoir.