Natural Resources Conservation Service s14

576 - 1 NATURAL RESOURCES CONSERVATION SERVICE CONSERVATION PRACTICE STANDARD ARIZONA

LIVESTOCK SHELTER STRUCTURE (No.)

CODE 576

DEFINITION banks or depressions. This practice must A permanent or portable structure with be used in conjunction with exclusion of less than four walls and/or a roof to animals from the sensitive area. Use a provide for improved utilization of livestock exclusion practice NRCS pastureland and rangeland and to shelter Conservation Practice (CPS) Fence livestock from negative environmental (Code 382). factors. This structure is not to be This practice is applicable where animal construed to be a building. productivity and well-being are adversely affected by negative environmental PURPOSE conditions such as direct and unimpeded * To provide protection for livestock sunshine, wind, or snow. from excessive heat, wind, cold, or This practice can facilitate livestock snow. management under prescribed grazing to * Protect surface waters from protect water quality and soil health. nutrient and pathogen loading. This practice can be used to provide * Protect wooded areas from protection on range or pasture; cropland accelerated erosion and excessive or hayland used for grazing; winter nutrient deposition by providing feeding areas; or in a livestock heavy use alternative livestock shelter/shade area. location. CRITERIA * Improve the distribution of grazing livestock to enhance wildlife General Criteria Applicable to All habitat, reduce over-used areas, or Purposes and Structure Types correct other resource concerns Transport of Portable Structure. Equip resulting from improper livestock the portable structure with runners or distribution. wheels or other means to facilitate transport. Provide lateral support to CONDITIONS WHERE PRACTICE vertical and horizontal structural members APPLIES to prevent twisting and/or buckling. This practice is applied to provide Location. Locate the structure to avoid protection to sensitive areas by providing adverse effects to cultural resources and a source of shade or shelter that is endangered, threatened, and candidate located away from the existing shade or species and their habitat. Select upland shelter in wooded areas and on stream locations that are away from riparian

NRCS, AZ September 2014 576 - 2 areas and concentrated flow areas to avoid impairment of water quality. Locate structures a minimum of 100 feet from any surface water bodies, 150 feet from an up-gradient well and 300 feet from a down-gradient well. Select location(s) that will not have surface water flow through the structure. Erosion Protection. Provide erosion protection from roof runoff. Materials. Construct the structure of durable materials that are commensurate Orientation. Orient the longest axis in a with a minimum structure life of 10 years. north to south direction to maximize the Fabric or other non-structural material amount of shade and to allow sunlight to may need to be replaced in accordance dry the area under the structure. with its anticipated lifespan (typically no more than 5 years). Dispose of or recycle Shade cover. Design the top of the worn out fabric or other non-structural structure to be relatively flat so that wind material as appropriate. will have minimum load on the structural supports. Provide a minimum1:25 pitch Waste Management. Design the for the structure roof to allow runoff. structure to facilitate the distribution of Anchor the four corners of the shade manure across grazing lands in structure with tie-downs of adequate size accordance with a nutrient management and strength to meet the local wind plan. conditions during season of use. Prescribed Grazing. When the livestock Size. The minimum size requirements for protection structure is installed to improve a shade structure are shown in Table 1. livestock distribution to address resource Limit the maximum size of individual concerns, then NRCS CPS Prescribed shade structure units to 25 feet wide by Grazing (Code 528) must also be 50 feet in length (1250 sq ft). Portable included in the resource management structures may be smaller to facilitate plan. movement. Multiple structures may be Additional Criteria Applicable to Shade needed depending on the number of Structures animals to be sheltered. Figure 1 – Typical Shade Structure In prescribed grazing systems for high- producing livestock, provide shade for at least 75% of the herd, particularly for dairy or beef cows. Table 1 – Minimum Shade Requirements Minimum Shade Animal Requirements Type Height Area 2 (ft) Dairy, beef, (ft35-50/head) 10 – 12 or horse

NRCS, AZ September 2014 576 - 3 Swine, 10-15 7 Shape and Size. Wind shelters shall be sheep, or a 90º “V” shaped, semi-circular shaped, Poultry 3 - 7 7 or straight line structures. For optimum protection from wind and drifting snow, a “V” shaped or Location. Locate the structure a semicircular structure is recommended. minimum of 50 feet from any existing The shelter opening width (perpendicular structure that could obstruct the to the wind direction) should be no wider circulation of air. Use the location of the than 15 times the shelter height. structure to create the desired livestock “ V” Shelters. Construct “V” shaped travel patterns. Move portable structures shelters with a solid face to divert drifting as needed to maintain healthy vegetation snow around ends of the barrier. Wind in the immediate area. speed reduction of 60-80 percent is Additional Criteria Applicable to Wind possible in the protected area extending Shelter Structures 5H downwind of the barrier (Figure 3). The V, or closed end, should point in the Location. Locate the wind shelter direction of the winter and early spring structure in an area where livestock prevailing winds. The shelters cause the shelter from prevailing winds is desired. snow to be diverted around the shelter See Figure 2. The site must be and deposited in drifts extending five accessible by vehicle or equipment. times the shelter width (D) downwind. Figure 2 – Typical Wind Shelter Compute the shelter zone area as shown Structure in Figure 3. Table 2 shows the shelter zone. The shelter structure shall provide a shelter zone area based on the values in Table 2. Design the shelter dimensions following guidance provided in Tables 2 and 3. Figure 3 -- Snowdrift Protection from “V” Shaped Structures

Locate the shelter on level, uninterrupted terrain, if possible. If the shelter must be located downwind of a hill, place the shelter as far downwind as possible. A shelter upwind of a hill shall be placed a minimum of 75 times the shelter height upwind of the base of the hill. Locate wind shelters perpendicular to the prevailing winter winds, where possible. Be careful that wind shelters do not block summer breezes, increasing heat stress.

NRCS, AZ September 2014 576 - 4 shaped design since less protection is Table 2 – Minimum Wind Shelter provided if wind direction varies from Requirements anything perpendicular to the fence. They will however provide effective wind Minimum Shelter Zone protection for up to 15 to 20 times the Animal Requirement Type 2 height of the structure for solid and Area (ft /head) porous walls. Snow is forced over the Dairy, beef, 35-50 fence and deposited downwind of the or horse structure rather than diverted around it. Swine, 10-15 General Structural Criteria. Post sheep, or spacing and depth will require site goat specific designs based on sustained wind Poultry 3 - 7 speed and direction. Lumber installed within eight inches of the ground must be pressure treated in accordance with ASTM D1760 Standard Specification for Pressure Treatment of Table 3 - Protected Area at Maximum Timber products. For facilities that are Wing Length (See Figure 3) organic producers or that sell compost to Barrier Wing L, Wing Protect organic producers, ensure that the height, ft. D, ft. ed area, treated lumber used in the shelter meets ft. ft². the requirements for organic production. It may be best to have the producer 6 60 84.8 3,964 consult with the organic certifier as to the 8 80 113.1 7,047 use and acceptability of treated lumber. 10 105 148.5 11,823 CONSIDERATIONS 12 125 176.8 16,828 14 145 205.1 22,714 Permanent structures should be centrally located in the grazing system to promote equidistant travel to all grazing areas. Semi-circular Shelters. Semi-circular shaped shelters can be built with The livestock shelter structure may approximately the same quantity of require pollution and erosion prevention materials as the “V” design. The ratio of measures in the design. protected area to shelter length is about Consider the economics, the overall 27 percent higher than in the “V” shape. waste management system plan, and Base the dimensions for the semi-circular safety and health factors. shaped barrier on a radius equal to one- half D for the “V” shaped barriers as If the structure is permanent, consider shown in Table 3. Semi-circular shelters applying NRCS Conservation Practice are generally the most economical Standard Heavy Use Area Protection (material cost per square foot); however, (Code 561) where vegetation cannot be the type of material used for board or maintained underneath or within the panels can be a limiting factor due to the structure. shape. The semi-circular shape also When applicable, consider the use of tends to be self-bracing. NRCS CPS Animal Trails and Walkways Straight line shelters. Straight line (Code 575) when frequent travel to windbreaks are not as effective as the “V” headquarters, grazing areas or watering NRCS, AZ September 2014 576 - 5 facilities is required. OPERATION AND MAINTENANCE With portable shade structures, consider Prepare an operation and removing and storing the structure or maintenance (O&M) plan for the fabric during winter months to extend the operator. The minimum requirements life of the shade cloth. to be addressed in the O&M plan are: Consider removing and storing mobile * Inspect the structure annually and shade structures during stormy weather after major storm events. events. * Maintain the structural and fabric Consider soil types and seasonal water components through the practice table zones when planning the location of lifespan. the livestock shelter structure. * Replace and/or repair PLANS AND SPECIFICATIONS maintenance coatings on structural steel components as necessary. Prepare plans and specifications for a livestock shelter structure according to * Periodically tighten the shade cloth this standard. Describe the requirements to minimize wind damage. for applying the practice to achieve its * Replace the fabric cover when it intended purposes. has deteriorated due to Include construction plans, drawings, job environmental conditions. sheets or other similar documents. * Move portable structures Specify in these documents the periodically to prevent destruction requirements for installing the practice. of vegetation in the immediate As a minimum, include: area. * The type, location (if permanent * If shelters are not moved structure), and orientation of the frequently, collect and remove shelter structure. accumulated animal waste on a regular basis or specified time * Wind calculations, as needed to interval and utilize in accordance set minimum thicknesses, with NRCS CPS Waste Recycling strengths, etc., for the structures (Code 633) or Nutrient based on a standard design wind Management (Code 590), as speed. Include the seasonal wind appropriate. directions needed to determine the orientation of the structure. REFERENCES * Develop a plan for movement of ASTM D A-36, A-120, D-751, D-1494, D- the structure, if portable. 1682, D-1760, D1910.; * Job sheets or construction Federal Specification TT-P-641; drawings. Federal Test Method Standard No. 191, * Construction specifications Method 5804; including dimensions of the “Warm Cows & Cool Breezes”, Montana structure, and configuration. State University Extension Service; * Materials, including the http://www.msuextension.org/counties/Stil dimensions, amount, any coatings, lwater/articles/Ag and quality to be used. %20Articles/Windbreaks.pdf ;

NRCS, AZ September 2014 576 - 6 “Taming Blizzards for Animal Protection, “Effect of a Solid Windbreak in a Cattle Drift Control and Stock Water”, R. L. Feeding Area”, Earl M. Bates, Oregon Jairell and R.A. Schmidt, USDA Forest State University and Ralph L. Phillips, Service; Eastern Oregon Agricultural Research Center. “Portable Animal Protection Shelter and Wind Screen”, R. L. Jairell and R.A. Schmidt, USDA Forest Service;

NRCS, AZ September 2014