* VTA. A minimum of two sampling sites shall be established within each VTA cell, one located where runoff enters the VTA and one where runoff is discharged from the VTA. Soil samples shall be taken from these sites to a depth of 4 feet, with separate samples taken to represent the 0 to 6-inch depth, the 6- to 12-inch depth, and in one-foot increments thereafter. All samples shall be analyzed for N03 N, NH4 N, P by either the Olsen or Mehlich-3 method, and pH.
If the length of effluent flow through the VTA exceeds 400 feet, an additional soil sample representing the 0 to 6-inch depth should be taken for each additional 200 feet of VTA length. Samples shall be analyzed for N03 N, NH4 N, P by either the Olsen or Mehlich-3 method, and pH.
* VIB. One sampling site shall be established where open feedlot effluent enters the VIB. Soil samples at this site shall be taken to a depth of 4 feet, with separate samples taken to represent the 0 to 6-inch depth, the 6- to 12-inch depth, and in one-foot increments thereafter. These samples shall be analyzed for N03 N, NH4 N, P by either the Olsen or Mehlich-3 method, and pH.
An additional sampling site shall be established where open feedlot effluent is discharged from the VIB through the tile system. Soil samples shall be taken at this site to represent the 0 to 6-inch depth, and analyzed for N03 N, NH4 N, P by either the Olsen or Mehlich-3 method, and pH.
Monitoring requirements for an AT system following the initial two-year operation period will be determined at the time the NPDES permit for the operation is due for renewal.
Iowa Admin. Code r. 567-65.104