How is the water stored?
The soils portion of the PRC Design required extensive background information on the types of soils that exist in this region and determining the optimum/available soil for use. There are eight soil associations which exist in this region. A soil association is a landscape that is comprised of an original pattern of soils. An association consists of one or more major soils and at least a minor soil if not more. The association will always take the name of the soil that has the larger percentage present (major soil). A soil can be present in another association but would be structured in a different pattern.
Researching and developing a general soil profile consisting of the following: Landscaping aggregate (evaporation barrier), weed barrier, soil class (loam), a silt barrier (prevents clogging of the drainage path), and a capillary barrier (to allow excess water to drain only when needed).
Maximizing the amount of rainfall to be captured by the soil is detrimental to the success of the PRC Design. Gravity is our enemy; therefore a soil that can sustain as much water as necessary and is available within this region is ideal for the design. Various categories of soils were researched with the specific requirements always accounted for. An in-depth understanding of applicable characteristics that could influence this portion of the design was investigated. Drought tolerant trees, plants, and shrubs that are native to this region aid in the amount of water to be used.
Background information on soil associations was obtained from ”Soil Survey El Paso County Texas” (United States Department of Agriculture in cooperation with Texas Agricultural Experiment Station, Issued in November 1971). Brief descriptions for each association along with its main points are stated.
The Hueco-Wink Association is present on almost level to gently sloping soils which consists of fine sandy loam subsoil and is moderately deep over caliche. This association covers approximately 41% of the county. The Hueco soils (major soil) occupy about 42% and 38% is Wink soils the rest is minor soils. Hueco soils normally consists of a brown loamy fine sand surface layer of about 4” thick. The subsoil is brown and yellowish –brown, calcareous fine sandy loam about 22” thick, and there still exist about 32” thickness of caliche underlying it.
The Bluepoint Association is present on deep, slightly sloping to extreme sloping soils which consist of a loamy sand underlying material. This association covers approximately 15% of the county. The Bluepoint soils (major soil) occupy about 98% and 2% is minor soils. Bluepoint soils have a gravelly sand surface layer (at high elevations). Pajarito soils are the principle minor soil (at low lying elevations).
The Harkey-Glendale Association is present on deep, almost level soil that consists of loamy very fine sand to a silty clay loam underlying material. This association covers approximately 12% of the county. The Harkey soils (major soil1) occupy about 37% and about 16% of the Glendale soils and about 47% is minor soils. Harkey soils typically consist of a surface layer of pink, calcareous silty clay loam about 12” thick. Layers of silt loam, loamy very fine sand, very fine sandy loam, and silty clay loam is the underlain for the surface layer. Please note that the underlying material has an average texture of loam. The Glendale soils (major soil2) consist of a surface layer that is brown, calcareous silty clay loam of about 17” thick. A silty clay loam of about 18” thick exists below the previous layer and covers a fine sandy loam. Many different minor soils exist in this association.
The Delnorte-Canutio Association is present on almost level to steep soils. The soils are at shallow or very shallow over caliche if not it is deep and gravelly throughout. This association covers approximately 9% of the county. The Delnorte soils (major soil1) occupy about 55% and about 18% of the Canutio soils and about 27% is minor soils. Delnorte soils typically consists of a surface layer of pinkish-gray, calcareous very gravelly loam about 6” thick. Caliche is underlying this surface layer with about 24” thick, also a gravelly fine sand below the caliche. Canutio soils (major soil2) which are calcareous very gravelly sandy loam throughout. The minor soils such as Bluepoint, Agustin, and Pajarito soils exist but at lower elevations. *Note* about 50% of this association is within the city of El Paso and Fort Bliss.
The Wink-Simona-Mimbres Association is present at sloping and almost level soils that can be moderately deep or shallow over caliche and can also exist with deep soils with silt loam subsoil. This association covers approximately 8% of the county. The Wink soils (major soil1) occupy about 39% and about 21% of the Simona soils and about 17% of the Mimbres soils leaving about 23% of minor soils. Wink soils typically consists of a pale-brown and light yellowish-brown, calcareous fine sandy loam about 24” thick over caliche (nearly level area). Simona soils (major soil2) typically have a light pale brown gravelly loam surface layer about 3” thick. A pale-brown gravelly fine sandy loam subsoil about 13” thick underlies it and caliche layer begins at about 16” (occupy higher and steeper part). Mimbres soils (major soil3) is a light-brownish-gray and brown silt loam to a depth of about 50” (occupy lower portion). Minor soils such as Hueco, Pajarito, Agustin, and Lozier soils also makeup the association.
The Limestone Rock Land-Lozier Association is present on steep, rocky areas, and very shallow, stony soils located in the Hueco Mountains. This association approximately covers 6% of the county. Limestone Rock Land (major soil1) occupies about 63% and the remaining area is Lozier soils and small areas of igneous rock land, Brewster soils, and Simona soils. The Limestone Rock Land consists of vertical outcrops of limestone together with sandstone in areas. Lozier soils have a surface layer consisting of a pinkish-gray, calcareous, stony loam that is about 5” thick over limestone (occupy lower slopes, and small hills). *Note* all the association is used as rangeland or for wildlife recreation, and Hueco Tanks Park lies in this association.
The Turney-Berino Association is present at almost level and slightly sloping soils that have clay loam subsoil and are somewhat deep over caliche. This association approximately covers 5% of the county. Turney soils (major soil1) occupy about 68% and 18% of the Berino soils and 14% of minor soils. Turney soils typically have a surface layer of about 10” thick. It is light reddish-brown fine sandy loam to a depth of about 3” and there is a light-brown loam below. The subsoil is a light –brown, calcareous loam and to reach a soft caliche it is about 34”. Berino soils (major soil2) typically consists of a surface layer that almost resembles Turney soils but that is noncalcareous and the subsoil of clay loam contains clay films on the soil particle. The minor soils that also exist in this association are the Hueco soils (eastern edge) and the Agustin and Pajarito soils (slightly higher elevations and on the western edge).
Igneous Rock Land-Limestone Rock Land Association is present at steep areas and limestone rocks and stony soils (in Franklin Mountains). This association approximately covers 4% of the county. Igneous Rock Land (major soil1) and adjacent Brewster soils occupies about 52% and 46% of the Limestone Rock Land and adjacent Lozier soils and about 2% of Delnorte and Canutio soils. Igneous Rock Land consists mostly of granite, monzanite, and rhyolite rocks. Brewster soils typically have a dark reddish-gray, noncalcareous stony loam surface layer that is about 10” thick and is underlain by granite. Limestone Rock Land is made up of limestone together with sandstone. Lozier soils typically have a surface layer of pinkish-gray, calcareous stony loam that is about 5” thick over limestone.*Note* no area of this association is suitable for cultivation.
Another soil map and a publication “Soil Resources of El Paso” illustrating a simplistic distinction for layers of soil available within the El Paso area was obtained from the Texas Cooperative Extension located locally. This publication has illustrations of soil profiles for all areas of the city. This map was compiled using 26 soil survey maps from this region by the Natural Resources Conservation Service. It divided the areas into two categories the Upland and Valley Soils. Under each category there are several groups. The Upland Soils consists of five groups (U-1 to U-5) and the Valley Soils consists of four groups (V-1 to V-2). The composition of the following groups will not be explained as they have already been covered in the above paragraphs.
The Upland soil (U-1) consists of Pajarito, Berino, and Turney loam. The U-2 soil consists of Bluepoint loamy sand and gravelly coarse sand. The U-3 soils are comprised of Hueco and Wink sandy loam. The U-4 soils consist of Augustin gravelly loam and Canutio gravelly sandy loam.
The Valley soil (V-1) is comprised of Gila, Harkey, and Glendale loam. The V-2 is made up of Brazito, Gila, and Vinton sandy loam. The V-3 consists of Anapra, Harkey, Glendale, and Saneli silty clay loam. The V-4 soil is comprised of Glendale, Saneli, and Tigua silty clay.
After, gathering the above information on existing soils research was aimed towards which category of soil would be optimal and available for the intended use for the PRC design. Obtaining a model demonstrating the water holding properties of soils based on texture from the U.S. Department of Agriculture (Yearbook, 1955) it was calculated by taking the difference between the field capacity and wilting point of various categories of soils and it was determined that a loam type material with a water holding value of 0.19≈0.20 would be ideal (optimum) source. All other articles read stated that a loam is the perfect type for plant-life. Loam is comprised of varying amounts (in percent by weight) of sand, silt, and clay. A soil texture diagram can further show the varying combinations of sand, silt, and clay that would categorize a soil as a loam.
The landscaping aggregate was researched to determine which would be implemented into the PRC Design (surface layer of the soil profile). This acts as both an evaporation barrier and will not allow the ultraviolet light to penetrate and cause growth of unwanted weeds. A local distributor of landscaping aggregate was contacted (Jobe Concrete) and prices were obtained per ton in a variety of aggregates. Prices for the following landscaping aggregates were quoted for Franklin Red, Antique Grey, Crystal White, Desert Tan, Mesa Red, Lava Rock, and Santa Fe Red. When determining the appropriate landscaping aggregate it was solely dependent on price, therefore Franklin Red is the aggregate that was incorporated in the PRC Design because it is one of the most popular colors used in the El Paso area and also one of the least expensive of the above listed choices.
The PRC Design depends greatly on a weed barrier (second layer of soil profile) that will allow the rainwater to flow in to the soil to be captured. The weed barrier is to be placed in all areas where landscaping aggregate (Franklin Red) will be placed. A vast quantity of weed barriers were researched and found a particular barrier by Easy Gardner Products which met all required specifications and is our recommendation for use in this PRC Design.
An additional moisture barrier (landscaping sheeting) will be used in areas surrounding the home where crushed stone is showed because the water runoff must flow to the plant area (capture zone) these areas are not used as storage areas but rather a tool to direct runoff.
The silt barrier (directly following the storage area—loam soil) is used as a prevention device to do just that, prevent the soil from clogging the drainage path for any excess water that must exit the system.
The capillary barrier (bottom layer of the soil profile) is the layer that will prevent the water from exiting the storage area (tank) before the water can be captured by the soil and used by the trees, plants, and shrubs. This barrier has a very important characteristic it must also allow a very slow percolation (drainage) rate. The trees, plants, and shrubs cannot survive if too much water is present because they will basically drown (waterlogged). Plants have tolerances for surviving without water as they do for an excess of water (must keep in mind). After researching several possible types of aggregates just any ordinary gravel would be sufficient for the design.
Many different sources were contacted in different areas of research. The Texas Cooperative Extension was used to gather information on the soils that exist in this region. The City of El Paso was also contacted for their feedback on water table information. The El Paso Water Utilities Conservation Department gathering information on whether this design could be beneficial to this area and to find out what type of incentives the water utilities offered to the public for implementing water conservation techniques. The Texas Department of Transportation was contacted by several members for different reasons, but I contacted them to obtain aerials of certain areas of east, northeast, downtown, and west El Paso. Professors at the University of Texas at El Paso also assisted with background information on soils.
A loam type material is optimal and available for use in the PRC Design. It meets the specific requirements (water-holding properties based on texture). All read material (websites) is in agreement that this class of material is ideal for plant-life survival.
All layers of the PRC Design soil profile have been researched and approved by all team members. Layers of the soil profile consist of the following: Landscaping aggregate (evaporation barrier), weed barrier, soil class (loam), a silt barrier (prevents clogging of the drainage path), and a capillary barrier (to allow excess water to drain only when needed).
There are many considerations to account for when importing a new material that is not consistent with the existing soil area. The new soil (if required) to import was discussed in a conversation with a contact from the cooperative extension and was told with time the old surrounding soil will overcome the newly imported soil but no definite time frame was ever mentioned.
Implementing this PRC Design has several other aspects to consider. Testing the existing material (soil) is necessary to determine what must be done (excavate/import or excavate/re-use). Once a new soil is determined necessary and a loam class of material is located it to must be tested to be certain it is within the specified possible combinations of a loam classification. Testing can be provided by any local geotechnical engineering firm or contact your local cooperative extension center for help.
Notes:
Soil classification is a very complex and is not an exact science (regarding a general soils map).
Many factors have to be considered and time was a constraint but major points were researched but not all.
