Natural Resources Conservation Service s61

NATURAL RESOURCES CONSERVATION SERVICE CONSERVATION PRACTICE STANDARD POND (No.) CODE 378

DEFINITION emergency spillway, the top of the dam is the upper limit. A water impoundment made by constructing a dam or an embankment or by excavating a pit 3. The effective height of the dam is 35 ft or or dugout. less, and the dam is hazard class (a). In this standard, ponds constructed by the first 4. Site conditions are such that runoff from the method are referred to as embankment ponds, design storm can be safely passed through and those constructed by the second method (1) a natural or constructed emergency are referred to as excavated ponds. Ponds spillway, (2) a combination of a principal constructed by combining the excavation and spillway and an emergency spillway, or (3) the embankment methods are classified as a principal spillway. embankment ponds if the depth of water 5. The drainage area contributing to the pond impounded against the embankment at is protected against erosion to the extent spillway elevation is 3 feet or more. that expected sedimentation will not shorten PURPOSE the planned effective life of the structure. The drainage area must be large enough so This practice may be applied as part of a that surface runoff and groundwater flow conservation management system to support will maintain an adequate supply of water in one or more of the following purposes: the pond for the intended purpose. The  Provide water for livestock, fish and water quality must be suitable for the wildlife, recreation, fire protection, and crop intended use. and orchard irrigation. 6. The topography and soils of the site permit  Maintain or improve water quality. storage of water at a depth and volume that ensures a dependable supply, considering CONDITIONS WHERE PRACTICE APPLIES beneficial use, sedimentation, season of use, and evaporation and seepage losses. This standard establishes the minimum If surface runoff is the primary source of acceptable quality for the design and water for a pond, the soils must be construction of ponds if: impervious enough to prevent excessive 1. Failure of the dam will not result in loss of seepage losses or must be of a type that life; in damage to homes, commercial or sealing is practicable. industrial buildings, main highways, or railroads; or in interruption of the use or GENERAL CRITERIA service of public utilities. All planned work shall comply with all federal, 2. The product of the storage (acre-ft.) times state, and local laws and regulations. Ponds the effective height (ft) of the dam is less may need to be approved by the appropriate than 3,000. Storage is the volume, in acre- permitting agency. feet, in the reservoir below the elevation of Vegetation. The exposed surfaces of the the crest of the emergency spillway. The embankment, earth spillway, borrow area, and effective height of the dam is the difference other areas disturbed during construction shall in elevation, in feet, between the be seeded or sodded as necessary to prevent emergency spillway crest and the lowest erosion. Areas shall be vegetated in point in the cross section taken along the accordance with NRCS Tennessee centerline of the dam. If there is no conservation practice standard for Critical Area Planting, Code 342.

Conservation practice standards are reviewed periodically, and updated if needed. To obtain the current version of this standard, contact the Natural Resources Conservation Service. NRCS, TN, August 2000 378-2

Visual resource design. The visual design of to be used as a public road, the minimum width ponds shall be carefully considered in areas of shall be 16 feet for one-way traffic and 26 feet high public visibility and those associated with for two-way traffic. Guardrails or other safety recreation. The underlying criterion for all measures shall be used where necessary and visual design is appropriateness. The shape shall meet the requirements of the responsible and form of ponds, excavated material, and road authority. plantings are to relate visually to their Table 1 - Minimum top width for dams surroundings and to their function. Total height of Top width (ft) CRITERIA FOR EMBANKMENT PONDS embankment (ft) < 10 6 Site Investigation. Field soil borings will be made to the extent necessary to determine 10 to < 15 8 adequate embankment foundation, emergency 15 to < 20 10 spillway and borrow locations. Borings for the 20 to < 25 12 embankment are usually along the centerline and used to determine if an adequate cutoff 25 to < 35 14 can be constructed. Borings in the emergency 35 15 spillway and borrow areas are used to determine the adequacy of material to be used in the foundation cutoff trench and Side slope. The combined upstream and embankment. A permanent record of all soil downstream side slopes of the settled borings and test pits made in the reservoir embankments shall not be less than that area, embankment foundation, borrow area, shown in Table 2. Neither slope shall be and emergency spillway area shall be steeper than two horizontal to one vertical maintained in the design folder. (2:1). All slopes must be designed to be stable, even if flatter side slopes are required. Foundation cutoff. A cutoff of relatively Dams to be mowed should have three impervious material shall be provided under horizontal to one vertical (3:1) side slopes or the dam if necessary. The cutoff shall be flatter. located at or upstream from the centerline of the dam. It shall extend up the abutments as Table 2 - Side Slope Based on Embankment required and shall be deep enough to extend Material into a relatively impervious layer (minimum of 1 Embankment Material Minimum Slopes foot) and provide for a stable dam when Horizontal to combined with seepage control. The cutoff Vertical Both trench shall have a bottom width adequate to Slopes* accommodate the equipment used for Clayey Sand (SC), 5:1 excavation, backfill, and compaction Sandy Clay (CL), Silty operations. Side slopes of the cutoff trench Clay (CL), Silty Sand shall be safe and in no case be steeper than (SM), Clayey Gravel one horizontal to one vertical (1:1). (GC), Silty Gravel (GM) Seepage control. Seepage control is to be Silt (ML), Fat Clay 6:1 included if (1) pervious layers are not (CH), Clayey Silts (MH) intercepted by the cutoff, (2) seepage creates swamping downstream, (3) such control is Fine Sand (SM-SP) 8:1 needed to ensure a stable embankment, or (4) (Minimum one side 3.5 special problems require drainage for a stable to 1) dam. Seepage may be controlled by (1) * For mowing, construct 3:1 side slopes or flatter. foundation, abutment, or embankment drains; (2) reservoir blanketing; or (3) a combination of Wave Protection. Where needed to protect the these measures. face of the dam, special wave protection Top Width. The minimum top width for a dam measures such as berms, rock riprap, sand- is shown in Table 1. If the embankment top is gravel, soil cement or special water tolerant vegetation (maidencane, switchgrass, sandbar

NRCS, TN, August 2000 378-3

willows, and rice cutgrass) will be provided Embankments used as public roads will be (see Technical Release 56 or 69). When the completed by traversing with two passes on location of the pond exposes the dam to each lift with a loaded pan or sheep foot type prevailing winds, and fetch length is greater roller. than 1320 ft., the upstream slope shall be Principal spillway. A pipe conduit, with protected from wave damage as a minimum by needed appurtenances, shall be placed under one of the following methods: or through the dam, except where rock, 1. Place an 8 ft. wide berm approximately 1 ft. concrete, or other types of mechanical above the permanent water elevation. spillways are used, or where the rate and duration of flow can be safely handled by a 2. Place a blanket of riprap 2 ft. thick at the vegetated or earth spillway without erosion. permanent water elevation, the upper side Vegetated or earth spillways will not be of this blanket being 2 ft. above and the adequate without a pipe spillway if long lower side being 1 ft. below the permanent duration, continuous, or frequent flows are water elevation. expected. 3. Increase the width through the dam at the Storm Storage. The principal spillway crest permanent water elevation at least 4 ft. by elevation shall be no less than 0.5 foot below flattening the side slopes. the crest of the emergency spillway for dams having a drainage area of 20 acres or less, and 4. Plant water tolerant vegetation of the right no less than 1 foot for those having a drainage character and height on properly area of more than 20 acres. constructed berms. When vegetation is recommended for wave erosion protection, When design discharge of the principal the vegetation should be capable of spillway is considered in calculating peak enduring short durations of inundation outflow through the emergency spillway, the without serious damage and should be sod crest elevation of the inlet shall be such that formers or bunch-type plants. full flow will be generated in the conduit before there is discharge through the emergency Freeboard. The minimum elevation of the top spillway. The inlets and outlets shall be of the settled embankment shall be 1 foot designed to function satisfactorily for the full above the water surface in the reservoir with range of flow and hydraulic head anticipated. the emergency spillway flowing at design depth. The minimum difference in elevation Capacity. The capacity of the pipe conduit between the crest of the emergency spillway shall be adequate to discharge long-duration, and the settled top of the dam shall be 2 feet continuous, or frequent flows without flow for all dams having more than a 20 acre through the emergency spillway. The drainage area or more than 20 feet in effective minimum design storm frequency to use for the height. principal spillway is listed in Table 6. Pipe Size. The diameter of the pipe shall not Settlement. The design height of the dam be less than 4 inches. All pipe sizes may be shall be increased by the amount needed to considered when the routed design hydrograph ensure that after settlement has taken place, is used to design the emergency spillway. the constructed height of dam will equal or exceed the design height. This settlement shall Pipe Loading. Pipe conduits under or through not be less than 3 percent for rubber tired pans the dam shall be capable of withstanding and scrapers and 5 percent for track type external loading without yielding, buckling, or equipment such as bulldozers, except where cracking and must be watertight. Flexible pipe detailed soil testing and laboratory analysis strength shall not be less than that necessary shows a lesser amount is adequate or field to support the design load with a maximum of observations indicate a greater amount is 5 percent deflection. The inlets and outlets needed to obtain the needed level of shall be structurally sound and made of materials compatible with those of the pipe. compaction. Maximum thickness of earthfill Total pipe length shall include a minimum of 4 layers will be 8 in. and will be traversed over the entire area by the hauling equipment.

feet added to extend beyond the downstream For dams more than 20 feet in effective height, embankment toe. conduits shall be reinforced concrete pipe, cast-in-place reinforced concrete, corrugated Pipe Materials. For dams 20 feet or less in steel or aluminum, or welded steel pipe. effective height, acceptable pipe materials are cast iron, welded steel, corrugated steel or PVC and HDPE pipe shall meet the aluminum, concrete, plastic including polyvinyl requirements in Table 3 and steel and chloride (PVC) and high density polyethylene aluminum pipe shall meet the requirements in (HDPE), and cast-in-place reinforced concrete. Table 4. Plastic pipe that will be exposed to direct High Density Polyethylene, Type III, Class C, sunlight should be made of ultraviolet resistant Category 4 or 5 conforming to ASTM D1248 materials or be protected by coating or and D3350 and AASHTO M252 or M294, Type shielding; or provisions made as necessary for S may be used for ponds with a hydraulic head replacement. Connections of plastic pipe to of 10 feet or less. Pipe connections must be less flexible pipe or structures must be water tight. Bell ended pipe is not acceptable designed to avoid stress concentrations that for use as a watertight connection. could rupture the plastic. Table 3.- Acceptable plastic pipe for use in earth dams 5/ Type of plastic pipe Nominal pipe size Maximum depth of fill over pipe (in) (ft) SDR 32.5 (125 psi) 1/ 6 - 12 10 SDR 26 (160 psi) 1/ 6 - 12 14 SDR 21 (200 psi) 1/ 6 - 12 20 Schedule 40 2/ 6 - 12 10 Schedule 80 2/ 6 - 12 20 C900 (100 psi) 3/ 4 - 12 10 C900 (150 psi) 3/ 4 - 12 15 C900 (200 psi) 3/ 4 - 12 20 HDPE or PVC 4/ 4 - 18 15 HDPE or PVC 4/ 24 - 36 10 1/ Polyvinyl chloride pipe, PVC 1120 or PVC 1220, conforming to ATSM-D2241. SDR = Standard Dimension Ratio (outside diameter/wall thickness). 2/ Polyvinyl chloride pipe, PVC 1120 or PVC 1220, conforming to ATSM-D1785 . 3/ Polyvinyl chloride pipe, PVC 1120 or PVC 1220, conforming to AWWA C900 4/ High Density Polyethylene, Type III, Class C, Category 4 or 5 conforming to ASTM D1248 and D3350 and AASHTO M252 or M294, Type S: or PVC; ASTM F949 5/ Backfill around pipe must be carefully placed and well-tamped with a density equal to conditions that existed before excavation

Table 4.- Minimum gage for corrugated metal pipe [2-2/3-in x ½-in corrugations]1/ Fill Minimum gauge for steel pipe Min. thickness (in) of aluminum pipe 2/ height (ft) (Diameter in inches) (Diameter in inches) < 24 30 36 42 48 > 21 24 30 36 1 to < 15 16 16 14 12 10 0.06 0.06 0.075 0.075 15 to < 20 16 16 14 12 10 0.06 0.075 0.105 0.105 20 to < 25 16 14 12 10 10 0.06 0.105 0.135 ----3/

1/ Pipe with 6-, 8-, and 10-inch diameters has 1-1/2 in x ¼-in corrugations. 2/ Riveted or helical fabrication. 3/ Not permitted

Pipe Joints and Appurtenances. The joints 2. The conduit is of smooth pipe larger than between sections of pipe shall be designed to 8 inches in diameter. remain watertight after joint elongation caused by foundation consolidation. Concrete pipe 3. The conduit is of corrugated metal pipe shall have concrete bedding or a concrete larger than 12 inches in diameter. cradle, if required. Cantilever outlet sections, if Seepage along pipes extending through the used, shall be designed to withstand the embankment shall be controlled by use of a cantilever load. Pipe supports shall be filter and drainage diaphragm, unless it is provided when needed. Other suitable devices determined that anti-seep collars will such as a Saint Anthony Falls stilling basin or adequately serve the purpose. an impact basin may be used to provide a safe, non-eroding outlet. Diaphragm Drain. The drain is to consist of sand, meeting fine concrete aggregate Pipe Protection. Protective coatings of asphalt requirements in ASTM C-33 (at least 15 or polymer on galvanized corrugated metal percent passing the No. 40 sieve but no more pipe, or coal tar enamel on welded steel pipe than 10 percent passing the No. 100 sieve). If must be provided in areas that have a history unusual soil conditions exist, a special design of pipe corrosion, or where the saturated soil analysis shall be made. resistivity is less than 4,000 ohms-cm, or where soil pH is lower than 5. The drain shall be a minimum of 2 feet thick and extend vertically upward and horizontally Cathodic Protection. Cathodic protection is to at least three times the pipe diameter, and be provided for coated welded steel and vertically downward at least 18 inches beneath galvanized corrugated metal pipe where soil the conduit invert. and resistivity studies indicate that the pipe needs a protective coating, and where the The drain diaphragm shall be located need and importance of the structure warrant immediately downstream of the cutoff trench, additional protection and longevity. If cathodic approximately parallel to the centerline of the protection is not provided for in the original dam. design and installation, electrical continuity in The drain shall be outletted at the embankment the form of joint-bridging straps should be used downstream toe, preferably using a drain on pipes that have protective coatings. backfill envelope continuously along the pipe to Cathodic protection should be added later if where it exits the embankment. Riprap monitoring indicates the need. NRCS protection of drain fill from surface erosion will conservation practice standard 430-FF be necessary. provides criteria for cathodic protection of welded steel pipe. Anti-Seep Collars. When anti-seep collars are used in lieu of drainage diaphragm, they shall Valves. A pipe with a suitable valve shall be be installed around the pipe conduit or pond provided to drain the pool area if needed for drain pipe within the normal saturated zone. proper pond management or if required by When one collar is used, it will be placed at State law. The principal spillway conduit may centerline of dam. Additional collars will be be used as a pond drain if it is located where it equally spaced alternately between the fill can perform this function. centerline and the upstream (us) end and Water Trough Supply Pipes. Supply pipes downstream (ds) end of the conduit with a through the dam to watering troughs and other spacing not to exceed 14 times the maximum appurtenances shall have an inside diameter projection of the collar. (Example: centerline of not less than 1.25 inches. -us-ds-us-ds). The pipe conduit shall have a minimum slope Anti-seep collars and their connections to the of 0.5 foot per 100 feet (after foundation pipe shall be watertight. The collar material settlement) to provide positive drainage. shall be compatible with pipe materials. Metal anti-seep collars and their connections to the Seepage Control. Seepage control along a pipe shall extend a minimum of 18 in. in all pipe conduit spillway shall be provided if any of directions from the pipe. Reinforced concrete the following conditions exist: collars shall have a minimum thickness of 6 in. and shall extend a minimum of 2 ft. in all 1. The effective height of dam is greater than directions from the pipe except when the pipe 15 feet. is bedded on rock. Concrete collars will not be

NRCS, TN, August 2000 378-6 used with corrugated metal pipe. On plastic sleeve shall be installed at the riser inlet on all pipes, use flexible collars of 6 mils. or thicker drainage area embankment ponds to prevent plastic or rubber sheeting attached with the conduit from clogging. Levee ponds shall stainless steel clamps or waterproof tape and have a trash guard or be screened to prevent caulked to ensure water tightness. fish from escaping and non-desirable fish from entering the pond through the pipe. The Table 5 or the following formula may be used minimum quality of material used shall be to calculate the number of collars. 16 gauge and shall be protected by asphalt

No. of collars = Length of Conduit Within Normal Saturation Zone -1 coating, galvanizing, or water durable paint. 14 x Minimum Projection of Collar Trash guards of PVC or polyethylene are acceptable if size and thickness are adequate. The length of conduit within normal saturation Barrels or plastic buckets are not acceptable. zone shall be taken along the pipe barrel from All hardware used for mounting shall be of the upstream toe to the midpoint between the equal and compatible material. centerline of the dam and downstream slope of the dam at the pipe outlet. Anti-vortex. Closed conduit spillways designed for pressure flow are to have adequate anti- Trash Guards. An approved type of trash vortex devices. guard sleeve (minimum length 24 in.) or wildlife

Table 5 - Recommended Number of Anti-Seep Collars Collar Projection Collar Projection Collar Projection Fill Height 1/ 1.5 ft. 2/ 2.0 ft. 2/ 2.0 ft. 3/ 0 - 13.9 1 1 1 14 - 16.9 2 1 2 17 - 21.9 3 2 3 22 - 26.9 4 3 4 27 - 31.9 5 4 5 32 - 35 6 4 5

1/ Fill height is the fill over the invert of the pipe at centerline of dam. (This height should not be used for hooded inlet and similar types of installations.) 2/ Collars computed on side slopes of 2 1/2:1 + top width x 0.75 for saturated zone. 3/ Computed on 3:1 slopes + top width x 0.75 for saturated zone.

Hood Inlet. A hood inlet may be used when a depth over the crest equal to about 1/3 the installed in the dam abutment with any size of pipe diameter. An air vent is provided to break pipe barrel. The section of pipe on which the the siphoning action when the reservoir water hood is installed must be at least 12 ft. long surface is drawn down to normal pool and be of steel, aluminum, concrete, PVC, or elevation. Because of the negative pressure bituminous coated corrugated metal. The hood that exists within the siphon when flowing full, shall be on top of the pipe and project three- the pipe joints must be air tight and the pipe fourths of the diameter of the pipe. The must be sufficiently rigid to withstand the vertical distance between the invert of the pipe collapsing forces. Welded steel or plastic pipe and control section of the emergency spillway with glued joints should be used. Pipe joints shall be no less than 1.5 times the diameter of using rubber gasketed joints may not be the pipe. sufficiently airtight to function properly in a siphon system. Siphon Spillway. A siphon pipe spillway is a closed conduit system formed in the shape of The following minimum criteria shall apply to an inverted "V", positioned so that the invert of siphon spillway systems, in addition to other the bend (CREST) of the upper passageway is applicable criteria listed elsewhere in this at normal water surface elevation. The initial standard: The total drop of the siphon will be discharge of the siphon, as the reservoir level limited to a maximum of 20 feet. A 2 inch rises above normal, is similar to flow over a diameter vent pipe will be used on siphon weir. Siphoning action begins after the air in pipes up through 8 inches and a 4 inch the siphon pipe has been exhausted, usually at diameter vent pipe will be used for siphons

10 inch through 16 inch diameters. Pipe used of the inlet channel may be curved to fit for siphons shall be smooth steel or smooth existing topography. plastic pipe with a minimum wall thickness Control Section. The control section shall be equivalent to Schedule 40 or SDR 26. The siphon will have an elbow on the downstream constructed level at designed grade with a end or will be submerged during flow to minimum length of 25 feet. completely seal the end of the pipe. If an Exit Channel. The exit channel, that portion elbow is used, it will have a 1/4 inch to 3/8 inch downstream from the control section, shall be weep hole drilled in the bottom of the elbow to straight in alignment for a distance of 50 ft. and ensure that water does not freeze in the pipe its centerline shall be perpendicular to the and possibly prevent the siphon from control section. The grade of the exit channel functioning. The pipe will be buried through shall fall within the range established by the dam and the downstream section of the discharge requirements and maximum pipe will be buried or have adequate anchors permissible velocities. The exit channel shall and restraints to prevent thrust forces and terminate at a point where the design flow may vibrations from breaking it. The vent pipe will be protected by a perforated pipe sleeve to be discharged without erosion or damage to prevent floating debris from clogging the vent. the earth embankment. Refer to Chapter 11, The total area of the perforations in the vent Ponds and Reservoirs, Engineering Field pipe sleeve should equal at least four times the Manual Handbook. vent pipe area. The inlet to the siphon shall Capacity. The minimum capacity of the natural have a perforated section which will exclude or constructed earth spillway shall be that trash, turtles, fish, etc. The perforated inlet required to pass the peak flow expected from a section must have an open area equivalent to design storm of the frequency and duration at least two times the cross sectional area of shown in Table 6 less any reduction creditable the siphon pipe. to conduit discharge and detention storage. Emergency Spillway. An emergency spillway Cross Section. The spillway shall be excavated shall be provided for all dams to safely pass the design storm runoff around the dam. in undisturbed earth and have a trapezoidal Where spillways are constructed in earth, they cross section with side slopes not steeper than shall be vegetated. Earthen portions of a three horizontal to one vertical. The side spillway constructed in rock shall be vegetated. slopes may be vertical when the spillway is All embankment ponds will have a minimum excavated in rock. 10 ft. wide spillway, except levee-type Structural emergency spillways. If chutes or embankment ponds which exclude outside drops are used for principal spillways or drainage area. These type levee ponds are emergency spillways, they shall be designed not required to have an emergency spillway if according to the principles set forth in the the principal spillway is designed to handle a National Engineering Field Handbook for 10 yr. - 24 hr. direct rainfall amount. Conservation Practices and the National Excavated spillways shall consist of an inlet Engineering Handbook-Section 5, Hydraulics; channel, a control section, and an exit channel. Section 11, Drop Spillways; and Section 14, Chute Spillways. The minimum capacity of a Inlet Channel. The inlet channel, portion structural spillway shall be that required to upstream from the control section, shall have a pass the peak flow expected from a design uniform negative grade toward the pond with a storm of the frequency and duration shown in minimum slope of 0.5 percent or enough grade Table 6, less any reduction creditable to to achieve adequate drainage. The alignment conduit discharge and detention storage.

Table 6 - Minimum Hydrologic Criteria for Design of Class I Through V Dams Eng. Job Class 1/ Principal Spillway Emergency Spillway Freeboard 7/ or Detention Storage Design Storm Storm (24 hour) (24 hour)

years years 2/ years 3/ Ft. I 0.5 4/ 10 50 1 I 1 4/ 25 50 1 II 2 25 50 1 III 5/ 5 50 50 1 IV 5/ 10 50 50 1 V 10 50 50 6/ 1/ See Tennessee Engineering Job Approval Chart TN-ENG-17. 2/ When height and effective storage is less than 20 ft. or 50 acre-ft. respectively. 3/ When height and effective storage is equal to or more than 20 ft. or 50 acre-ft. respectively. 4/ Crest elevation of the emergency spillway is a minimum of 1 foot above permanent pool elevation except (a) may be 0.5 for less than 15 acre D.A., and (b) excavated ponds with spring flow or for water level control. All other Class I ponds use 1 year storm (use 0.5 year storm only on pond with D.A. less than 15 Acres). 5/ Where drainage area is less than 20 acres and storage is less than 50 acre ft., emergency spillway design storm may be reduced to 25 year frequency. 6/ Routed freeboard hydrograph for Class "A" dam shall be minimum 2 ft. above emergency spillway crest. 7/ Prevailing wind freeboard for fetch length shall be: 660 ft. or less, 1.0 ft.; 660 to 1,320 ft., 1.5 ft.; and 1320 to 5280 ft., 2 ft.

EXCAVATED PONDS 1. Uniformly spread to a height that does not exceed 3 feet, with the top graded to a Site Investigation. Site suitability and design continuous slope away from the pond. shall be based on adequate investigations and surveys as described in the National 2. Uniformly placed or shaped reasonably Engineering Field Handbook for Conservation well, with side slopes assuming a natural Practices, Chapter 11, Ponds and Reservoirs. angle of repose. The excavated material will be placed at a distance equal to the Runoff. Provisions shall be made for a pipe depth of the pond but not less than 12 feet and emergency spillway if necessary. Runoff from the edge of the pond. flow patterns and ground water recharge rate shall be considered when locating the 3. Shaped to a designed form that blends excavated pond and placing the spoil. visually with the landscape. Side slopes. Side slopes of excavated ponds 4. Used for low embankment and leveling. shall be stable and shall not be steeper than 5. Hauled away. one horizontal to one vertical (1:1). If livestock will water directly from the pond, a watering Additional Criteria for Livestock Water ramp of ample width shall be provided. The ramp shall extend to a depth of 3 feet below The required storage shall be calculated using the anticipated low water elevation at a slope 1.5 times the sum of the following: no steeper than four horizontal to one vertical 1. The specified minimum gallons per animal (4:1). per day as stated in NRCS conservation Perimeter form. If ponds are to be used for practice standard Trough or Tank, Code recreation or are highly visible to the public, the 614, for the estimated number of days to be perimeter or edge should be curvilinear. used. Inlet protection. If surface water enters the 2. The net evaporation loss for the design pond in a natural or excavated channel, the days of storage. side slope of the pond shall be protected 3. Seepage loss based on the best available against erosion. data. Excavated material. The material excavated Additional Criteria for Fish and Wildlife from the pond shall be placed so that its weight will not endanger the stability of the pond side The reservoir shall be designed for a maximum slopes and so that it will not erode back into amount of water in excess of three feet in the pond by rainfall. It shall be disposed of in depth. Management of ponds for fish one of the following ways: production shall be in accordance with NRCS conservation practice standard Fish Pond Management, Code 399.

Additional Criteria for Recreation spillway. In addition, the pond will be designed with a permanent pool deep enough to hold The volume of water should be sufficient to water all year and with shallow areas (littoral exceed evaporation and seepage losses and zones) with dense vegetation. These practices maintain a desirable water level. The water will increase sedimentation of suspended must be free of pollution, especially where it is solids, reduce resuspension of sediments by to be used for swimming. wave action, remove floating debris from storm Additional Criteria for Fire Protection water, and aid in mosquito control. Fire protection shall be incorporated into the CONSIDERATIONS structure design by incorporating an underground piping system which connects the Ponds will affect the water budget, especially reservoir to a dry hydrant. Minimum water effects on volumes and rates of runoff, storage, location of intake pipe, etc., shall meet infiltration, evaporation, transpiration, deep the requirements of Tennessee NRCS percolation, and ground water recharge. conservation practice standard Dry Hydrant, Generally the peak discharge will be reduced Code 432. The pump shall be of sufficient and in many instances reduced to zero during capacity and hoses shall be of sufficient length dry periods that could affect other water uses to reach the structures to be protected. or users. There may be an increase in recharge to the ground water since most ponds Additional Criteria for Crop and Orchard seep and the base flow may extend for a Irrigation longer period of time. Effects on the volume of The capacity of the pond shall be adequate to downstream flow may prohibit undesirable meet the irrigation requirement of the planned environmental, social or economic effects. crop(s). The required capacity shall be based Ponds have the potential for multiple uses. on the irrigation requirements of the crops to Storage requirements for each purpose should be irrigated, the effective rainfall expected be considered to ensure an adequate water during the growing season, the application supply for all intended uses. Ponds used for efficiency of the irrigation method used, the multiple uses should be compatible. losses due to evaporation and seepage, and the expected inflow into the pond. Properly designed ponds will trap nutrients, sediments and pesticides. Therefore chemical Additional storage shall be provided for the concentrations will normally be higher in the estimated volume of sediment that will be pond area and lower in the downstream deposited during the life of the structure. channel section. Suitable means should be provided to convey This practice will affect the visual quality of water from the pond to the spray equipment. onsite and downstream water resources. The To prevent contamination of the water supply embankment may be shaped to blend with the from the spray equipment into which chemicals natural topography. The edge of the pond may are injected, the design must incorporate be shaped so that it is generally curvilinear backflow prevention devices. rather than rectangular. Excavated material Chemigation shall be applied in conformance can be shaped so that the final form is smooth, with NRCS Tennessee conservation practice flowing, and fitting to the adjacent landscape standards Nutrient Management, Code 590, rather than angular geometric mounds. If and Pest Management, Code 595. feasible, islands may be added for visual interest and to attract wildlife. Additional Criteria for Maintaining and Improving Water Quality Short-term and construction-related effects of this practice may affect the quality of Water quality problems include sediment, downstream water courses. fertilizers, pesticides, litter, oils, and solvents. A reduction of peak flows to a receiving stream Surface water temperature of the pond will or water body will slow water flow and thereby increase and may affect the temperatures of carry less suspended solids. Ponds designed downstream water and cause undesired for water quality improvement of downstream effects on aquatic and wildlife communities. water bodies shall be designed so that the first Ponds constructed in upland areas may have a flush of a storm event will be retained within positive effect on wildlife habitats. the pond and later storm water flow will be the first flows released through the principal

Ponds constructed in wetland areas must be PLANS AND SPECIFICATIONS evaluated to ensure the net wetland benefits are maintained or increased. Plans and specifications for installing ponds shall be in keeping with this standard and shall Where water must be conveyed for use describe the requirements for applying the elsewhere, such as for irrigation or fire practice to achieve its intended purpose. protection, ponds should be located as close to Copies of the plans and specifications shall be the point of use as feasible. given to the landuser. Ponds used for public recreation should have minimum facilities such as access roads, OPERATION AND MAINTENANCE parking areas, boat ramps or docks, and drinking and sanitary facilities. Where areas An operation and maintenance plan will be are used for swimming, safety signs should be made for each structure site and given to the installed indicating the depth of water and landuser. All ponds must be adequately flatter side slopes should be installed for maintained if their purposes are to be realized safety. Water should be tested for quality on a through the expected life. Special regular basis. considerations shall be given for maintenance needs during the planning, design, and During the construction of ponds, there is the construction of the pond. potential for earth moving to uncover or The pond should be inspected periodically, redistribute toxic materials. especially after heavy rains, to determine Due consideration should be given to whether it is functioning properly or if repairs economics, safety, and health factors. are needed. Appurtenances such as trash guards, outlet structures, and valves shall be kept free of trash and replaced when needed. Rills on the slopes of the dam and eroded areas in the earth spillway shall be filled with suitable material, compacted, seeded and fertilized as needed. Should the upstream face of the dam erode due to wave action, protection such as riprap may be needed. If seepage through or under the dam occurs, proper corrective measures shall be taken immediately. The vegetative cover of the dam and earth spillway shall be maintained by mowing, fertilizing or burning when needed. Trees can cause leaks and safety hazards and should not be permitted on the embankment or in the emergency spillway. When needed, fencing and watering troughs will be provided to protect the pond and vegetation from livestock.

REFERENCES NRCS Technical Release 56, 59, 60, 69 National Engineering Field Handbook, Chapter 11 National Engineering Handbook, Section 5 National Engineering Handbook, Section 11 National Engineering Handbook, Section 14 NRCS Conservation Practice Standards Critical Area Planting, Code 342 Dry Hydrant, Code 432 Fish Pond Management, Code 399

Irrigation Water Conveyance, Steel, 430-FF Trough or Tank, Code 614 Nutrient Management, Code 590 Pest Management, Code 595

NATURAL RESOURCES CONSERVATION SERVICE CONSTRUCTION SPECIFICATIONS

EMBANKMENT POND

SCOPE one horizontal to one vertical (1:1). All material containing excessive amounts of organic matter This item shall consist of the clearing, excavation, shall be removed. The surface of the foundation backfill, concrete and other appurtenances area will be thoroughly scarified before placement required for the construction of the embankment of the embankment material. and the disposal of all cleared and excavated materials for the water impoundment. Topsoil. Topsoil excavated from the foundation Construction operations shall be carried out in area and from the emergency spillway and borrow such a manner that erosion, air, water and noise areas shall be stock piled and placed on the dam, pollution will be minimized and held within legal emergency spillway and borrow areas to facilitate limits as established by state regulations. establishment of vegetation.

CLEARING AND GRUBBING EXCAVATION Pond Area. All trees and brush shall be cut as Excavation and Backfill of Cutoff Trench. The flush with the ground as practicable, and all such cutoff trench shall be excavated to the depths, trees, brush, logs and other debris shall be bottom width and side slopes (minimum one removed from the pond site. Clearing shall be horizontal to one vertical) shown on the plans. All performed around the shoreline as specified. standing water shall be removed from the trench and it shall be backfilled using thin layers Spillway and Borrow Areas. On areas from (maximum 8 inches) to the ground surface with which fill materials are to be obtained, all trees, suitable material by the same methods herein brush, logs, roots and other debris larger than 1 prescribed for "embankment construction." inch in diameter shall be removed. Excavation and Backfill of Stream Channels. The Embankment Site. All trees, brush and Existing stream channels crossing the foundation other debris shall be removed from the area on area shall be deepened and widened as which fill is to be placed. All stumps and roots one necessary to remove all stones, gravel, sand, inch in diameter and larger should be removed sediment, stumps, roots, organic matter and other from the fill site to a depth of 12 inches. objectionable material and to accommodate Disposal of Cleared and Grubbed Material. All compaction equipment. Side slopes shall be combustible material cleared and grubbed from constructed no steeper than one horizontal to one the site shall be disposed of by burning, burying at vertical (1:1). All water shall be removed from the approved locations or removing from the site. All channels, and they shall be backfilled in the same burning shall conform to Tennessee laws and manner as prescribed for the cutoff trench. regulations. All noncombustible materials cleared and grubbed from these areas shall be removed from the site or buried with a minimum cover of 2 feet. Topsoil, when available, should be stockpiled at a convenient location for use on the embankment, emergency spillway and other disturbed areas to facilitate establishment of vegetative cover. FOUNDATION PREPARATION Surface Treatment. The foundation area shall be cleared of all trees, stumps, roots, brush, boulders, sod, and debris. All channel banks and sharp breaks shall be sloped to no steeper than

Conservation practice standards are reviewed periodically, and updated if needed. To obtain the current version of this standard, contact the Natural Resources Conservation Service. NRCS, TN, August 2000 378-2

Spillway and Borrow Excavation. The Drainfill shall be kept from being contaminated by completed spillway excavation shall conform as adjacent soil materials during placement by either nearly to the lines, grades, bottom width and side placing it in a cleanly excavated trench or by slopes shown on the plans as skillful operation of keeping the drain at least 1 foot above the the excavating equipment will permit. The adjacent earthfill. channel bottom shall be constructed transversely Selected drainfill and backfill material shall be level and the side slopes uniform. All borrow placed around structures, pipe conduits, and areas outside the pool area shall be graded and antiseep collars at about the same rate on all constructed in such a manner that they are well sides to prevent damage from unequal loading. drained and protected from erosion by the use of diversions or other conservation measures. Side Moisture Control. The moisture content of fill slopes of borrow areas shall be constructed in material shall be such that the specified such condition that establishment of vegetation, compaction can be obtained with the equipment mowing and maintenance operations will be used. The moisture content of the fill shall be facilitated. maintained within a range to: Excavation in borrow areas within the permanent 1. prevent the bulking or dilatence of the material pool area shall be graded in such a manner that under the action of the hauling or compaction they are well drained and will provide the equipment minimum specified depth of water at the normal water level. When specified, shoreline treatment 2. prevent adherence of the fill material to the shall be performed by cut or fill to develop the equipment desired depth of flooded area around the normal 3. ensure the crushing and blending of the soil pool. clods and aggregation into a homogeneous mass EMBANKMENT CONSTRUCTION 4. contain adequate moisture so that a sample Selecting, Placing and Spreading of Material. can be hand molded The fill material shall be free of all sod, roots, frozen soil, stones over 6 inches in diameter, and The completed fill shall conform as nearly to the other objectionable material. The placing and lines and grades, top width, and side slopes spreading of the fill material shall begin at the shown on the plans as skillful operation of the lowest point of the foundation (cutoff trench) and construction equipment will permit. the fill shall be brought up in approximately horizontal layers not exceeding 8 inches in PIPE CONDUIT INSTALLATION uncompacted thickness. Special attention will be The pipe conduit barrel shall be placed on a firm given to compaction in the cutoff trench where it foundation to the lines and grades shown on the joins the abutment slopes. plans. Selected backfill material shall be placed These layers shall be of approximately uniform around the barrel and its component parts in elevation and shall extend over the entire area of layers not exceeding 4 inches in thickness. Each the fill. Each layer shall be thoroughly compacted successive layer shall be thoroughly compacted by at least two complete passes of the by hand or power tampers. Heavy equipment construction equipment over the entire surface shall not cross over the pipe conduit barrel until 2 area of each layer after the layer has been spread feet of hand compacted material has been placed to the lift thickness. Special compaction over the pipe. equipment shall be used when the required Materials. All of the component parts of the compaction cannot be obtained by routing of the principal spillway conduit including barrel, riser, construction equipment. trashrack or deep water release, anti-seep collars, The distribution and gradation of materials support posts, braces and hardware for mounting throughout the fill shall be such that there will be shall be of the quality specified and constructed as no lenses, pockets, streaks or layers of material shown on the plans. differing substantially in texture or gradation from Concrete. The work shall consist of furnishing, the surrounding material. Where it is necessary to forming, placing, finishing and curing Portland use material of varying texture and gradation, the cement concrete. more impervious material shall be placed in the upstream and center portions of the fill.

When concrete is used for footings under risers, flexible collars will be held in place during anti-seep collars, and bedding for reinforced installation with wire or light wood framing. Proper concrete pipe barrels, the mixture shall be not less inspection of the installation is essential, than five bags per cubic yard. The consistency of especially during the bedding of the conduit and the concrete shall be such as to allow the backfilling adjacent to the conduit and anti-seep concrete to be worked into place without collars. All other requirements for installation of segregation or excessive laitance. plastic pipe will be in accordance with NRCS conservation practice standard Subsurface The components of the mix shall be as follows: A Drains, Code 606. standard known brand, Type I Portland cement, washed sand and gravel. Clean water shall be Principal Spillways, Trash Guards and Fittings. used in the mix. (Suggested ratio in mix: 94 The pipe and pipe connecting bands shall conform pounds cement (1 bag), 6 gallons water, with the following specifications and requirements: 170 pounds clean dry sand, 315 pounds dry Corrugated Steel Pipe. ASTM A760, 762, 885 or gravel. Smaller batches: 1 part cement, 2 parts Federal Specification WW-P-405; helical sand, 3 parts gravel, and water at the rate of 1 corrugated or close riveted annular corrugated; gallon per 16 pounds of cement). asphalt or polymer coated; and watertight Concrete shall not be placed when the connections as specified below: atmospheric temperature may be expected to fall Rubber "O" Ring type: all types and diameters below 40oF at the time concrete is delivered and of pipe. placed at the work site nor when it is expected to exceed 90oF during placement. All exposed Flanged Type: for pipe diameters 12 in. and surfaces of concrete shall be protected from the under. direct rays of the sun for at least the first seven days. All concrete shall be cured by keeping it Conventional Connecting Bands: All diameters continuously moist for at least seven days after annular corrugated pipe only. Twelve inch being placed or by spraying with two coats of minimum band width with rods and lugs curing compound when other concrete will not be required. bonded to the concrete surface. Concrete shall Corrugated Aluminum Alloy Pipe. ASTM B745, not be exposed to freezing temperature during the 790 or Federal Specification WW-P-402; lock, or curing period. welded seam helical corrugated with watertight Pre-Bedding. The strength of lightweight, flexible connections as specified above for corrugated PVC and corrugated steel and aluminum pipe is steel pipe. highly dependent on the bedding and backfill. It Steel Pipe. ASTM A120 standard weight must be carefully jointed together, bedded, and (Schedule 40). Used pipe is satisfactory provided backfilled. The backfill to be used in the vicinity of its wall thickness has not been reduced by the pipe should be the most impervious fine corrosion. grained material available and have proper moisture content to assure good compaction Concrete Pipe. AWWA C300, C301, and C302, or around the conduit. The pipe conduit should be ASTM C76 Class II with joint sealed with rubber cambered to prevent breaking or joint separation gaskets. Requires concrete bedding (minimum when the dam is built. That is, the pipe should be 3 inches thickness) under bottom third of pipe. laid essentially level to centerline of dam, then laid Plastic Pipe. Polyvinyl chloride pipe, PVC 1120 or essentially straight to the exit end elevation. Then PVC 1220, conforming to ASTM D1785, when the earthfill load is applied over the pipe, the ASTM D2241, or AWWA C900. pipe will flatten to a smooth uniform grade and tighten the joint. Flexible anti-seep collars should High Density Polyethylene Pipe. High density be used to avoid stress concentrations in the pipe polyethylene Type III, Class C, Category 4 or 5 as it deflects. The bottom of the bedding trench conforming to ASTM D1248 and D3350 and will be shaped as a minimum to fit the lower one AASHTO M252 or M294, Type S. third (120o) of the pipe. Flexible anti-seep collars Markings. Marking on plastic (PVC) pipe verifies may be constructed of 6 mil or thicker plastic or product specifications and includes: rubber sheeting attached to the pipe with stainless a. Manufacturer's name or trademark and steel clamps, waterproof tape, or closet flanges product code. and caulk material to ensure water tightness. The

b. Nominal pipe size (e.g. 6 inches). construction shall be installed and maintained as needed and according to NPDES permit if c. Material code designation (PVC 1120, required. BMP's consisting of silt fences, hay bale 1220). barriers, diversions, mulching, stream crossings, d. Standard Dimension Ratio or schedule no. temporary vegetation, fencing and others may be (SDR-26, SCH. 40). appropriate to adequately control erosion and sediment during construction. e. Pressure rating or pressure class (160 psi). f. Specification designation (D1785, D2241). VEGETATION Antiseep collars are to be of materials compatible Vegetation will be established as specified in the with the pipe and installed so as to be watertight. vegetative plan. The embankment, spillway, The pipe shall be installed in accordance with the borrow areas and other non-impounded areas manufacturer's instructions and to the lines and disturbed during construction will be seeded or grades shown on the drawings. planted to perennial non-woody vegetation and then mulched. A perennial vegetation filter strip at Other Materials. Other materials used in the least 50 feet wide will be established immediately principal spillway system that are not specified will above the normal waterline of the impoundment be as noted in the plans or drawings. area, when adequate vegetation does not exist. Inspection of Materials. All materials used in the This filter strip will be a part of the vegetation fabrication and installation of the principal process. spillway, trash rack, valves and other fittings, shall Temporary vegetation or mulching will be used be visually inspected prior to or during their after construction is completed until conditions are installation to assure quality and integrity of favorable for seeding and planting permanent material. vegetation. POLLUTION CONTROL NRCS conservation practice standard, Critical Area Planting, Code 342 shall be used for plant Construction operations shall be performed so selection, seedbed preparation, liming, fertilizing, that erosion and sediment are controlled during seeding and mulching for both temporary and construction, and air and water pollution are permanent vegetation. Treated areas will be minimized. Best management practices (BMP) for fenced when needed to protect the vegetation.

NRCS, TN, August 2000 CS-378-1

NATURAL RESOURCES CONSERVATION SERVICE CONSTRUCTION SPECIFICATIONS

EXCAVATED POND

SCOPE POLLUTION CONTROL This item shall consist of the clearing, filling, Construction operations shall be carried out so and/or excavation required for the construction of that erosion and sediment control during an excavated pond and the disposal of all cleared construction is addressed, and air and water and excavated materials for the water pollution is minimized. Best Management impoundment. The construction operations shall Practices (BMP) for construction shall be installed be carried out to minimize erosion, air, water and and maintained as needed and according to noise pollution and maintain these within legal NPDES permit if required. BMP's consisting of silt limits as established by state regulations. fence, hay bale barriers, diversions, mulching, stream crossing, temporary vegetation, fencing CLEARING and others may be appropriate to adequately All trees, brush and stumps shall be cut as flush control erosion and sediment during construction. with the ground as is practical and removed from the site and spoil areas before excavation is VEGETATION performed. All material cleared from the area Vegetation will be established as specified in the shall be disposed of by burning or removing from vegetative plan. The berm, spoil banks and other the site. All burning shall conform to state laws disturbed areas will be seeded or planted to and regulations. perennial, non-woody vegetation and then mulched. A perennial vegetation filter strip at EXCAVATION OR SPOIL least 50 feet wide will be established around the The completed pond, berms and spoil banks (spoil excavated pond. disposal) and waste material shall conform as Treated areas will be fenced when needed to nearly to lines, dimensions, grades and slopes protect the vegetation from grazing or traffic. shown on the plans or staked on the site as skillful operations of the excavating equipment will permit.

Conservation practice standards are reviewed periodically, and updated if needed. To obtain the current version of this standard, contact the Natural Resources Conservation Service. NRCS, TN, August 2000