567—65.109 (459A) Settled open feedlot effluent basins—investigation, design and construction requirements. A settled open feedlot effluent basin required to be constructed pursuant to a construction permit issued pursuant to 2005 Iowa Code Supplement section 459A.205 shall meet the design and construction requirements set forth in this rule.
	 65.109(1) Drainage tile investigation and removal. Prior to constructing a settled open feedlot effluent basin, the owner of the open feedlot operation shall investigate the site for the basin for a drainage tile line. The investigation shall be made by digging a core trench to a depth of at least six feet deep from ground level at the projected center of the berm of the basin. A written record of the investigation shall be submitted as part of the construction certification required in rule 65.111(459A). If a drainage tile line is discovered, one of the following solutions shall be implemented:
	  a.   	 The drainage tile line shall be rerouted around the perimeter of the basin at a distance of least 25 feet horizontally separated from the outside toe of the berm of the basin. For an area of the basin where there is not a berm, the drainage tile line shall be rerouted at least 50 feet horizontally separated from the edge of the basin.
	  b.   	 The drainage tile line shall be replaced with a nonperforated tile line under the basin floor. The nonperforated tile line shall be continuous and without connecting joints. There must be a minimum of three feet between the nonperforated tile line and the basin floor.
	 65.109(2) Soils and hydrogeologic report. A settled open feedlot effluent basin required to be constructed pursuant to a construction permit issued pursuant to rule 65.105(459A) shall meet design standards as required by a soils and hydrogeologic report. The report shall be submitted with the construction permit application as provided in rule 65.107(459A). The report shall include all of the following:
	  a.   	 A description of the steps taken to determine the soils and hydrogeologic conditions at the proposed construction site, a description of the geologic units encountered, and a description of the effects of the soil and groundwater elevation and direction of flow on the construction and operation of the basin.
	  b.   	 The subsurface soil classification of the site. A subsurface soil classification shall be based on ASTM international designation D 2487-92 or D 2488-90.
	  c.   	 The results of a soils investigation conducted at a minimum of three locations within the area of the basin reflecting the continuous soil profile existing within the area of the basin. The soils investigation results shall be used in determining subsurface soil characteristics and groundwater elevation and direction of flow at the proposed site. The soils investigation shall be conducted and utilized as follows:
	 (1) 	 By a qualified person ordinarily engaged in the practice of performing soils investigations.
	 (2) 	 At locations that reflect the continuous soil profile conditions existing within the area of the proposed basin, including conditions found near the corners and the deepest point of the proposed basin. The soils investigation shall be conducted to a minimum depth of ten feet below the proposed bottom elevation of the basin.
	 (3) 	 By methods which identify the continuous soil profile and do not result in mixing of soil layers. Soil corings using hollow stem augers and other suitable methods may be used.
	 (4) 	 If located in karst terrain, at least one soil coring shall be taken to a minimum depth of 25 feet below the bottom elevation of the settled open feedlot effluent basin or into bedrock, whichever is shallower. The department may accept information from the department’s Geosam database in lieu of the coring. If bedrock is encountered, adequate investigation of the bedrock formation shall be made to determine if it consists of limestone, dolomite, or other soluble rock.
	 (5) 	 Soil corings may be used to determine current groundwater levels by completing the corings as temporary monitoring wells as provided in 65.109(3)“a”(1) and measuring the water levels in these wells no earlier than seven days after installation as provided in 65.109(3)“a”(2).
	 (6) 	 Upon abandonment of soil core holes, all soil core holes including those developed as temporary water level monitoring wells shall be plugged with concrete, Portland cement concrete grout, bentonite, or similar materials.
	 (7) 	 If excavation methods are used in conducting the soils investigation, upon closure these excavations must be filled with suitable materials and adequately compacted to ensure they will not compromise the integrity of the basin liner.
	 65.109(3) Hydrology.
	  a.   	 Determination of groundwater table. For purposes of this rule, groundwater table is the seasonal high-water table determined by a professional engineer, a groundwater professional certified pursuant to 567—Chapter 134, or qualified staff from the department or Natural Resources Conservation Service (NRCS). If a construction permit is required, the department must approve the groundwater table determination.
	 (1) 	 Current groundwater levels shall be measured as provided in this subparagraph for either a formed settled open feedlot effluent basin or an unformed settled open feedlot effluent basin. Three temporary monitoring wells shall be developed according to 567—subrule 110.11(8). The top of the well screen shall be within five feet of the ground surface. Each well shall be extended to at least two feet below the proposed top of the liner of an unformed settled open feedlot effluent basin, or to at least two feet below the proposed bottom of the footings of a formed settled open feedlot effluent basin. In addition, the wells must be installed as follows:
	  1. 	 Unformed basins. For an unformed settled open feedlot effluent basin, the monitoring wells may be installed in the soil core holes developed as part of conducting the soils investigation required in paragraph 65.109(2)“c.”
	  2. 	 Formed basins. For a formed settled open feedlot effluent basin, at least three temporary monitoring wells shall be installed as close as possible to three corners of the structure, with one of the wells close to the corner of deepest excavation. If the formed settled open feedlot effluent basin is circular, the three monitoring wells shall be equally spaced and one well shall be placed at the point of deepest excavation.
	 (2) 	 The seasonal high-water table shall be determined by considering all relevant data, including the groundwater levels measured in the temporary monitoring wells not earlier than seven days following installation, NRCS soil survey information, soil characteristics such as color and mottling, other existing water table data, and other pertinent information. If a drainage system for artificially lowering the groundwater table will be installed in accordance with the requirements of paragraph 65.109(3)“c,”the level to which the groundwater table will be lowered will be considered to represent the seasonal high-water table.
	  b.   	 The settled open feedlot effluent basin shall be constructed with a minimum separation of two feet between the top of the liner of the basin and the seasonal high-water table.
	  c.   	 If a drainage tile line around the perimeter of the basin is installed a minimum of two feet below the top of the basin liner to artificially lower the seasonal high-water table, the top of the basin’s liner may be a maximum of four feet below the seasonal high-water table which existed prior to installation of the perimeter tile system. The seasonal high-water table may be artificially lowered by gravity flow tile lines or other similar system. However, the following shall apply:
	 (1) 	 Except as provided in subparagraph (2), an open feedlot operation shall not use a nongravity mechanical system that uses pumping equipment.
	 (2) 	 If the open feedlot operation was constructed before July 1, 2005, the operation may continue to use its existing nongravity mechanical system that uses pumping equipment, or it may construct a new nongravity mechanical system that uses pumping equipment. However, an open feedlot operation that expands the area of its open feedlot on or after April 1, 2011, shall not use a nongravity mechanical system that uses pumping equipment.
	 (3) 	 Drainage tile lines may be installed to artificially lower the seasonal high-water table at a settled open feedlot effluent basin, if all of the following conditions are satisfied:
	  1. 	 A device to allow monitoring of the water in the drainage tile lines and a device to allow shutoff of the flow in the drainage tile lines are installed, if the drainage tile lines do not have a surface outlet accessible on the property where the settled open feedlot effluent basin is located.
	  2. 	 Drainage tile lines are installed horizontally at least 25 feet away from the outside toe of the berm of the settled open feedlot effluent basin. Drainage tile lines shall be placed in a vertical trench and encased in granular material which extends upward to the level of the seasonal high-water table which existed prior to installation of the perimeter tile system.
	 65.109(4) Karst terrain.
	  a.   	 Construction prohibited. Settled open feedlot effluent basins shall not be constructed in areas which drain to known sinkholes or in karst terrain. Structure sites located within one mile of karst terrain shall be considered to be located in karst terrain, unless site-specific geologic information is submitted documenting that 25 feet of suitable materials exist between the structure bottom and carbonated bedrock or limestone or dolomite.
	  b.   	 The use of formed structures is required to store liquid or dry manure in karst terrain.
	 (1) 	 Formed structures constructed of concrete in karst terrain shall comply with the provisions of 65.15(14).
	 (2) 	 The use of formed structures constructed of materials other than concrete and located in areas which drain to known sinkholes or located in karst terrain may be approved by the department if the proposed structures are designed by a professional engineer, a minimum of five feet vertical separation is maintained between the structure bottom and carbonated bedrock, and the engineer certifies and provides data showing the permeability of the geologic material below the structure’s base is sufficiently low to provide an adequate barrier to prevent percolation into carbonated bedrock or groundwater.
	  c.   	 Construction of settled open feedlot effluent basins is allowed in areas identified as karst terrain if site-specific geologic information is submitted documenting that 25 feet of suitable materials exist between the structure bottom and carbonated bedrock or limestone or dolomite.
	 65.109(5) Bedrock separation. A settled open feedlot effluent basin shall be constructed with at least four feet of separation between the bottom of the basin and a bedrock formation.
	 65.109(6) Floodplain requirements.
	  a.   	 Construction in floodplains. Open feedlot operation structures located on a floodplain or within a floodway of a river or stream may be required to obtain DNR permits and provide protection from inundation by flood waters, as specified in 567—Chapters 71 and 72.
	  b.   	 Permits for dam construction. Open feedlot operation structures exceeding storage capacity or dam height thresholds may be required to obtain DNR permits, as specified in 567—71.3(455B) and 72.3(455B).
	 65.109(7) Liner design and construction. The liner of a settled open feedlot effluent basin shall comply with all of the following:
	  a.   	 The liner shall comply with any of the following permeability standards:
	 (1) 	 The liner shall be constructed to have a percolation rate that shall not exceed one-sixteenth inch per day at the design depth of the basin as determined by percolation tests conducted by the professional engineer. If a clay soil liner is used, the liner shall be constructed with a minimum thickness of 12 inches or the minimum thickness necessary to comply with the percolation rate in this paragraph, whichever is greater.
	 (2) 	 The liner shall be constructed to have a percolation rate that shall not exceed one-sixteenth inch per day at the design depth of the basin. The design of the liner will specify a moisture content, compaction requirement, and liner thickness that will comply with the maximum allowable percolation requirement, and will be based on moisture content and percentage of maximum density as determined by a standard 5 point proctor test performed in accordance with ASTM D698 (Method A). The liner thickness will be based on laboratory tests of the compacted material, with a minimum liner thickness of 12 inches. Appropriate field or laboratory testing during construction shall be provided to verify the design requirements are met.
	  b.   	 If a synthetic liner is used, the liner shall be installed to comply with the percolation rate required in 65.109(7)“a”(1).
	 65.109(8) Berm erosion inspection and repair. The owner of an open feedlot operation using a settled open feedlot effluent basin shall inspect the berms of the basin at least semiannually for evidence of erosion. If the inspection reveals erosion which may impact the basin’s structural stability or the integrity of the basin’s liner, the owner shall repair the berms.