(a) General Requirement. To document the soil and site conditions, a complete site evaluation shall be performed by either a site evaluator or a professional engineer on every tract of land where an OSSF will be installed. A report prepared by either the site evaluator or the professional engineer providing the site evaluation criteria in subsection (b) of this section shall be submitted with the planning materials.
(b) Site evaluation criteria. All aspects of the site evaluation shall be performed by either a site evaluator or a professional engineer according to this section. The information obtained during the site evaluation shall be used to determine the type and size of the OSSF.
  (1) Soil analysis. The site evaluator or the professional engineer shall either drill two soil borings or excavate two backhoe pits at opposite ends of the proposed disposal area to determine the characteristics of the soil. In areas of high soil variability, the permitting authority may require additional borings or backhoe pits. The borings or backhoe pits shall either be excavated to a depth of two feet below the adopted excavation of the disposal area, or to a restrictive horizon, whichever is less. The location of all borings or backhoe pits shall be clearly indicated on the site drawing required in §285.5(a) of this title (relating to Submittal Requirements for Planning Materials).
    (A) Soil texture analysis. A general texture analysis shall be performed to identify the classification of the soil. The different soils in each class are provided in §285.91(6) of this title (relating to Tables).
      (i) Soil Class Ia. This class includes sandy textured soils that contain more than 30% gravel.
      (ii) Soil Class Ib. This class includes sand and loamy sand soils that contain less than or equal to 30% gravel.
      (iii) Soil Class II. This class includes sandy loam and loam soils.
      (iv) Soil Class III. This class includes silt, silt loam, silty clay loam, clay loam, sandy clay loam, and sandy clay soils.
      (v) Soil Class IV. This class includes silty clay and clay soils.
    (B) Gravel analysis. Class II or Class III soils containing gravel shall be further evaluated by either a site evaluator or a professional engineer by using a sieve analysis to determine the percentage of gravel by volume and the size of the gravel as indicated in §285.91(5) of this title.
    (C) Restrictive horizons analysis. The soils within the borings or backhoe pits shall be analyzed by either a site evaluator or a professional engineer to determine if a restrictive horizon exists. Clay subsoils, rock, and plugged laminar soils are considered restrictive horizons. Restrictive horizons are recognized by an abrupt change in texture from a sandy or loamy surface horizon to:
      (i) a clayey subsoil which an auger will not penetrate; or
      (ii) rock-like material which an auger will not penetrate.
  (2) Groundwater evaluation. The soil profile shall be examined by either a site evaluator or a professional engineer to determine if there are indications of groundwater within 24 inches of the bottom of the excavation.
    (A) If the designated representative and the site evaluator or the professional engineer disagree on the presence of groundwater, the designated representative shall verify groundwater information using the Natural Resources Conservation Service (NRCS) soil survey for that county, if it is available.
    (B) If the designated representative or the site evaluator or the professional engineer disagree with the NRCS soil survey, or if an NRCS soil survey does not exist for that county, the owner has the option to retain a certified professional soil scientist to evaluate the presence of groundwater and present that information to the designated representative for a final decision.
  (3) Surface drainage analysis.
    (A) Topography. The slope of each tract of land where an OSSF will be installed, areas of poor drainage such as depressions, and areas of complex slope patterns where slopes are dissected by gullies and ravines shall be determined. All slope patterns shall be clearly indicated on the site drawing, as required in §285.5(a) of this title.
    (B) Flood hazard. The 100-year floodplain for each tract of land where an OSSF will be installed shall be determined from either Federal Emergency Management Agency (FEMA) maps or from a flood study prepared by a professional engineer when FEMA maps are not available. The 100-year flood boundaries shall be clearly indicated on the site drawing, as required in §285.5(a) of this title. The drawing(s) shall also indicate if the 100-year floodplain does not exist within the tract.
  (4) Separation requirements. All features in the area where the OSSF is to be installed that could be contaminated by the OSSF or could prevent the proper operation of the system shall be identified during the site evaluation. The separation requirements are in §285.91(10) of this title. All features and separation distances shall be clearly indicated on the site drawing, as required in §285.5(a) of this title.

Source Note: The provisions of this §285.30 adopted to be effective June 13, 2001, 26 TexReg 4115; amended to be effective December 17, 2001, 26 TexReg 10363; amended to be effective September 11, 2008, 33 TexReg 7536