diff --git a/Tests/Data/HydroMechanics/Linear/Confined_Compression/cube_1e3.prj b/Tests/Data/HydroMechanics/Linear/Confined_Compression/cube_1e3.prj
index de0d4e1d073e1744a67095437cefaaba129278aa..3a52e8dcda5f9efba263435f67713baca05c13bd 100644
--- a/Tests/Data/HydroMechanics/Linear/Confined_Compression/cube_1e3.prj
+++ b/Tests/Data/HydroMechanics/Linear/Confined_Compression/cube_1e3.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_fr</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -27,6 +26,7 @@
             <secondary_variables>
             </secondary_variables>
             <specific_body_force>0 0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -87,11 +87,6 @@
             <type>Constant</type>
             <value>1e-12</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2.prj b/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2.prj
index 0e74896a34523ded0a654aaeb7b27790478edfb3..9bb973a794214994f6ad0fcd1a891316d9033f26 100644
--- a/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2.prj
+++ b/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_fr</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -36,6 +35,7 @@
                 <secondary_variable type="static" internal_name="velocity" output_name="velocity"/>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -121,11 +121,6 @@
             <type>Constant</type>
             <value>1e-12</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_quad9.prj b/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_quad9.prj
index c926e69279d68318255ff0a256809283580aa347..7ce892fd90404e15b7ec646f33db453e02ec9125 100644
--- a/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_quad9.prj
+++ b/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_quad9.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_fr</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -27,6 +26,7 @@
             <secondary_variables>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -87,11 +87,6 @@
             <type>Constant</type>
             <value>1e-12</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_tri.prj b/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_tri.prj
index 290c1898b2ae6629ed5fab36fe72de0cbe0de7cf..8d0e6e847555134b2ffba37b7de6c5377568f43b 100644
--- a/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_tri.prj
+++ b/Tests/Data/HydroMechanics/Linear/Confined_Compression/square_1e2_tri.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_fr</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -27,6 +26,7 @@
             <secondary_variables>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -87,11 +87,6 @@
             <type>Constant</type>
             <value>1e-12</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Gravity/flow_gravity.prj b/Tests/Data/HydroMechanics/Linear/Gravity/flow_gravity.prj
index ebb4682dc862ca31af7139b796278c3ef0d997a4..d4387af5730f33b57ce1d64722c2349c0c657bfc 100644
--- a/Tests/Data/HydroMechanics/Linear/Gravity/flow_gravity.prj
+++ b/Tests/Data/HydroMechanics/Linear/Gravity/flow_gravity.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_fr</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -36,6 +35,7 @@
                 <secondary_variable type="static" internal_name="velocity" output_name="velocity"/>
             </secondary_variables>
             <specific_body_force>0 -10</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -113,11 +113,6 @@
             <type>Constant</type>
             <value>1e-12</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e2_UC_early.prj b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e2_UC_early.prj
index 91ceb3179048850b483739c3c76c928f88ca60df..d31b77d91e7bdf2360116920f02f34804d9c9398 100644
--- a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e2_UC_early.prj
+++ b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e2_UC_early.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <biot_coefficient>alpha</biot_coefficient>
             <porosity>phi</porosity>
@@ -27,6 +26,7 @@
             <secondary_variables>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -87,11 +87,6 @@
             <type>Constant</type>
             <value>1e-10</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e4_UC_early.prj b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e4_UC_early.prj
index aa33e3d7b0a228190ab0131956ec30a6c0bbbf6a..73aa98a3ff6278b6fe4d13fae4580e16121290d9 100644
--- a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e4_UC_early.prj
+++ b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_early/square_1e4_UC_early.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <biot_coefficient>alpha</biot_coefficient>
             <porosity>phi</porosity>
@@ -27,6 +26,7 @@
             <secondary_variables>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -87,11 +87,6 @@
             <type>Constant</type>
             <value>1e-10</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e2_UC_late.prj b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e2_UC_late.prj
index ccb31ba3c5d13834082dd387df5b96f7b3ed2262..1e4066f63c19b8abba4f1fea4d231dfdc450d6ab 100644
--- a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e2_UC_late.prj
+++ b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e2_UC_late.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <biot_coefficient>alpha</biot_coefficient>
             <porosity>phi</porosity>
@@ -27,6 +26,7 @@
             <secondary_variables>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -87,11 +87,6 @@
             <type>Constant</type>
             <value>1e-10</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e4_UC_late.prj b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e4_UC_late.prj
index 81918ffcfa090c37666f91faf914b95e0f07a95c..980b479a734978f91a07e82bb5aa8dacab9e3ad8 100644
--- a/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e4_UC_late.prj
+++ b/Tests/Data/HydroMechanics/Linear/Unconfined_Compression_late/square_1e4_UC_late.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <biot_coefficient>alpha</biot_coefficient>
             <porosity>phi</porosity>
@@ -27,6 +26,7 @@
             <secondary_variables>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -87,11 +87,6 @@
             <type>Constant</type>
             <value>1e-10</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/InjectionProduction1D.prj b/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/InjectionProduction1D.prj
index 2af65e40ae5513c5d38eef55dd4e1995b4f4ddc1..f0a7d36cb423625e3071e908dac4d98d072297cf 100644
--- a/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/InjectionProduction1D.prj
+++ b/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/InjectionProduction1D.prj
@@ -15,7 +15,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_f</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -37,6 +36,9 @@
                 <secondary_variable type="static" internal_name="velocity" output_name="velocity"/>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>compressible_fluid</fluid_type>
+            <!--this value creates the same result as a specific storage of S = 1e-5 -->
+            <fluid_compressibility>3.33333333333e-5</fluid_compressibility>
         </process>
     </processes>
     <time_loop>
@@ -155,11 +157,6 @@
             <type>Constant</type>
             <value>4.9346165e-11</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>1e-5</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/RerefenceSolutionByMonolithicScheme/InjectionProduction1DMono.prj b/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/RerefenceSolutionByMonolithicScheme/InjectionProduction1DMono.prj
index e9fd97d658fa3b1bb72d9c96216f04888a1f837b..e1c8b8c1df18e9602f6513b3cf722c1e34aabca9 100644
--- a/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/RerefenceSolutionByMonolithicScheme/InjectionProduction1DMono.prj
+++ b/Tests/Data/HydroMechanics/StaggeredScheme/InjectionProduction1D/RerefenceSolutionByMonolithicScheme/InjectionProduction1DMono.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_f</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -36,6 +35,9 @@
                 <secondary_variable type="static" internal_name="velocity" output_name="velocity"/>
             </secondary_variables>
             <specific_body_force>0 0</specific_body_force>
+            <fluid_type>compressible_fluid</fluid_type>
+            <!--this value creates the same result as a specific storage of S = 1e-5 -->
+            <fluid_compressibility>3.33333333333e-5</fluid_compressibility>
         </process>
     </processes>
     <time_loop>
@@ -114,11 +116,6 @@
             <type>Constant</type>
             <value>4.9346165e-11</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>1e-5</value>
-        </parameter>
         <parameter>
             <name>mu</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm1_1Dbeam.prj b/Tests/Data/HydroMechanics/Verification/hm1_1Dbeam.prj
index f459664d1a92d5697627a094c099fdcb5293d3d2..0a1f540888a2cb0684f66d0568ba961024891ca2 100755
--- a/Tests/Data/HydroMechanics/Verification/hm1_1Dbeam.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm1_1Dbeam.prj
@@ -15,7 +15,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -41,6 +40,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force> 0 0 0 </specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -199,11 +199,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm1_2Dsquare.prj b/Tests/Data/HydroMechanics/Verification/hm1_2Dsquare.prj
index f4c24762767bc3d08dd2d76b18ba41da7d503acc..477a7495bcf7431d874eb8919dbabcee43671027 100755
--- a/Tests/Data/HydroMechanics/Verification/hm1_2Dsquare.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm1_2Dsquare.prj
@@ -15,7 +15,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -41,6 +40,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force> 0 0 0 </specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -198,11 +198,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm1_3Dcube.prj b/Tests/Data/HydroMechanics/Verification/hm1_3Dcube.prj
index 8523394a9896cca04dec4cca2c8d4663fa1d8e9f..88588a196fa84250f1e8cfa448b48e7991c6f91e 100755
--- a/Tests/Data/HydroMechanics/Verification/hm1_3Dcube.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm1_3Dcube.prj
@@ -15,7 +15,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -41,6 +40,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force> 0 0 0 </specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -198,11 +198,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm1_3Dgravity.prj b/Tests/Data/HydroMechanics/Verification/hm1_3Dgravity.prj
index 6e49ed6a57e2716e5276db4f16e5d4929eded9bb..716f8fd439a25c1a50c612f549ed9fb215e2d1fc 100755
--- a/Tests/Data/HydroMechanics/Verification/hm1_3Dgravity.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm1_3Dgravity.prj
@@ -15,7 +15,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -41,6 +40,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force> 0 0 -9.81 </specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -270,11 +270,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm2_1D1bt.prj b/Tests/Data/HydroMechanics/Verification/hm2_1D1bt.prj
index a79b55245f1bcd1ebfe0dafc16d1e0b4f9aac3fc..bf0f5dc1769d6d6d205f1608685bb46b2433c883 100755
--- a/Tests/Data/HydroMechanics/Verification/hm2_1D1bt.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm2_1D1bt.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -40,6 +39,7 @@
                <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force>0 0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -152,11 +152,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm2_1D2bt.prj b/Tests/Data/HydroMechanics/Verification/hm2_1D2bt.prj
index 996b4ac1791f2521d471a2f499ee9b2e4e8181c5..2f1945b6b9dc2b1281a83bf39b4d0d7aeaa059a9 100755
--- a/Tests/Data/HydroMechanics/Verification/hm2_1D2bt.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm2_1D2bt.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -40,6 +39,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force>0 0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -152,11 +152,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm2_1Dbiot.prj b/Tests/Data/HydroMechanics/Verification/hm2_1Dbiot.prj
index 70ae31c01cfdc56ed750e0f16a1add6427faddbf..4cc2face5c3b36841e5ef7337b4f8dc31bf10bc2 100755
--- a/Tests/Data/HydroMechanics/Verification/hm2_1Dbiot.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm2_1Dbiot.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -40,6 +39,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force>0 0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -152,11 +152,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn1.prj b/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn1.prj
index 1399cd7996f42d351c13b7dd377c1725bb3135fd..338e3ae40cb2805fec0524d3b960b1310d4f3f9b 100755
--- a/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn1.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn1.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -40,6 +39,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force>0 0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -152,11 +152,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn2.prj b/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn2.prj
index 8c1a5a4f5b8ba79b5c81329fe83382fdc01dd392..eea967213e5b265c5d59f9cf329393abdeb5b0ab 100755
--- a/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn2.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm2_1Dcolumn2.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -40,6 +39,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force>0 0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -156,11 +156,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>
diff --git a/Tests/Data/HydroMechanics/Verification/hm2_2Dmandel.prj b/Tests/Data/HydroMechanics/Verification/hm2_2Dmandel.prj
index 4861e69894065806fc7a593f4d91ea8b4459ca8b..87534d1bd5483da0b775c5a82661ff47a2d65cba 100755
--- a/Tests/Data/HydroMechanics/Verification/hm2_2Dmandel.prj
+++ b/Tests/Data/HydroMechanics/Verification/hm2_2Dmandel.prj
@@ -14,7 +14,6 @@
                 <poissons_ratio>nu</poissons_ratio>
             </constitutive_relation>
             <intrinsic_permeability>k</intrinsic_permeability>
-            <specific_storage>S</specific_storage>
             <fluid_viscosity>mu</fluid_viscosity>
             <fluid_density>rho_liquid</fluid_density>
             <biot_coefficient>alpha</biot_coefficient>
@@ -40,6 +39,7 @@
                 <secondary_variable type="static" internal_name="epsilon_yz" output_name="epsilon_yz"/>
             </secondary_variables>
             <specific_body_force>0 0 0</specific_body_force>
+            <fluid_type>incompressible_fluid</fluid_type>
         </process>
     </processes>
     <time_loop>
@@ -156,11 +156,6 @@
             <type>Constant</type>
             <value>1e-3</value>
         </parameter>
-        <parameter>
-            <name>S</name>
-            <type>Constant</type>
-            <value>0</value>
-        </parameter>
         <parameter>
             <name>rho_liquid</name>
             <type>Constant</type>