R317-5-4. Feasibility Determination and Approval-in-Concept

  4.1. General Criteria for Determining LUWD System Feasibility.

  The division shall determine the feasibility of using a LUWD system. Upon favorable determination for feasibility an approval-in-concept will be granted by the division.

  A. General Information. The required information shall include:

  1. situs address if available;

  2. name and address of the property owner and person requesting feasibility;

  3. the location, type, and depth of all existing and proposed private and public drinking water wells, and other water supply sources within 1500 feet of the proposed LUWD system;

  4. the location of all drinking water source protection zones delineated on the project site;

  5. the location of all existing creeks, drainages, irrigation ditches, canals, and other surface and subsurface water conveyances within 1500 feet of the proposed LUWD system;

  6. the location and distance to nearest sewer, owner of sewer, whether property is located within service boundary, and size of sewer; and

  7. statement of proposed use if other than a single-family dwelling.

  B. If the proposed LUWD system is located in aquifer recharge areas or areas of other particular geologic concern, the division may require such additional information relative to ground water movement, or possible subsurface wastewater flow.

  C. Soil and Site Evaluation.

  1. Soil Exploration Pit and Percolation Test.

  a. A minimum of five soil exploration pits shall be excavated to allow the evaluation of the soils. The soil exploration pits shall be constructed and soil logs recorded as detailed in Section R317-4-14 Appendix C.

  b. The division may require percolation tests in addition to the soil exploration pits.

  c. The division may require additional pits, tests, or both where:

  i. soil structure varies;

  ii. limiting geologic conditions are encountered; or

  iii. the division deems it necessary.

  d. The percolation test shall be conducted as detailed in Section R317-4-14 Appendix D.

  e. Soil exploration pits and percolation tests shall be conducted as closely as possible to the proposed absorption system site. The division shall have the option of inspecting the open soil exploration pits and monitoring the percolation test procedure. All soil logs and percolation test results shall be submitted to the division.

  f. When there is a substantial discrepancy between the percolation rate and the soil classification, it shall be resolved through additional soil exploration pits, percolation tests, or both.

  g. Absorption system feasibility and sizing shall be based on Section R317-4-13 Table 5 or 6.

  2. Wind-Blown Sand.

  The extremely fine grained wind-blown sand found in some parts of Utah shall be deemed not feasible for LUWD systems unless pretreatment is provided, as percolation test results in wind-blown sand will generally be rapid, but experience has shown that this soil has a tendency to become sealed with minute organic particles within a short period of time.

  3. Suitable Soil Depth.

  For conventional systems, effective suitable soil depth shall extend at least 48 inches or more below the bottom of the dispersal system to bedrock formations, impervious strata, or excessively permeable soil. Some alternative LUWD systems may have other requirements.

  4. Ground Water Requirements.

  The elevation of the anticipated maximum ground water table shall meet the separation requirements of the anticipated absorption systems.

  a. Maximum Ground Water.

  Maximum ground water table shall be determined where the anticipated maximum ground water table, including irrigation induced water table, might be expected to rise closer than 48 inches to the elevation of the bottom of a LUWD system. Maximum ground water table shall be determined where alternative LUWD wastewater systems may be considered based on groundwater elevations. The maximum ground water table shall be determined by the following.

  i. Regular monitoring of the ground water table, or ground water table, perched, in an observation well for a period of one year, or for the period of the maximum groundwater table.

  (1) Previous ground water records and climatological or other information may be consulted for each site proposed for a LUWDS system and may be used to adjust the observed maximum ground water table elevation.

  ii. Direct visual observation of the maximum ground water table in a soil exploration pit for:

  (1) evidence of crystals of salt left by the maximum ground water table; or

  (2) chemically reduced iron in the soil, reflected by redoximorphoric features i.e., a mottled coloring.

  (3) Previous ground water records and climatological or other information may be consulted for each site proposed for a LUWD system and may be used to adjust the observed maximum ground water table elevation in determining the anticipated maximum ground water table elevation.

  iii. In cases where the anticipated maximum ground water table is expected to rise to closer than 34 inches from the original ground surface and an alternative LUWD system would be considered, previous ground water records and climatological or other information shall be used to adjust the observed maximum ground water table in determining the anticipated maximum ground water table.

  b. Curtain Drains.

  A curtain drain or other effective ground water interceptor may be allowed as an attempt to lower the groundwater table to meet the requirements of this rule. The division shall require that the effectiveness of such devices in lowering the ground water table be demonstrated during the season of maximum ground water table.

  5. Ground Slope.

  Absorption systems may not be placed on slopes where the addition of fluids is judged to create an unstable slope.

  a. Absorption systems may be placed on slopes between 0% and 25%, inclusive.

  b. Absorption systems may be placed on slopes greater than 25% but not exceeding 35% if:

  i. all other requirements of this rule can be met;

  ii. effluent from the proposed system will not contaminate ground water or surface water, and will not surface or move off site before it is adequately treated to protect public health and the environment;

  iii. no slope will fail, and there will be no other landslide or structural failure if the system is constructed and operated adequately, even if all properties in the vicinity are developed with a LUWD system; and

  iv. a report is submitted by a professional engineer or professional geologist that is licensed to practice in Utah. The report shall be imprinted with the engineer's or geologist's registration seal and signature and shall include the following.

  (1) Predictions and supporting information of ground water transport from the proposed system and of expected areas of ground water mounding.

  (2) A slope stability analysis that shall include information about the geology of the site and surrounding area, soil exploration and testing, and the effects of adding effluent.

  (3) The cumulative effect on slope stability of added effluent if all properties in the vicinity were developed with LUWD systems.

  c. Absorption systems may not be placed on slopes greater than 35%.

  6. Other Factors Affecting a LUWD System Feasibility.

  a. The locations of all rivers, streams, creeks, dry or ephemeral washes, lakes, canals, marshes, subsurface drains, natural storm water drains, lagoons, artificial impoundments, either existing or proposed, that will affect building sites, shall be provided.

  b. Areas proposed for LUWD wastewater systems shall comply with the setbacks in Section R317-4-13 Table 2.

  c. If any part of a property lies within or abuts a flood plain area, the flood plain shall be shown within a contour line and shall be clearly labeled on the plan with the words "flood plain area".

  7. Unsuitable.

  Where soil and other site conditions are clearly unsuitable for the placement of a LUWD system, there is no need for conducting soil exploration pits or percolation tests.