R317-4-4. Feasibility Determination

4.1. General Criteria for Determining Onsite Wastewater System Feasibility.

The regulatory authority shall determine the feasibility of using an onsite wastewater system. The regulatory authority will review required information for any existing or proposed lot to determine onsite wastewater system feasibility. The required information shall be prepared at the owner's expense by, or under the supervision of, a qualified person approved by the regulatory authority.

A. General Information.

The required information shall include:

1. the county recorder's plat and parcel ID and situs address if available;

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

3. the location, type, and depth of all existing and proposed non-public water supply sources within 200 feet of the proposed onsite wastewater systems, and of all existing or proposed public water supply sources within 1,500 feet of the proposed onsite wastewater systems.

a. If the lot is located in aquifer recharge areas or areas of other particular geologic concern, the regulatory authority may require such additional information relative to ground water movement, or possible subsurface wastewater flow.

b. If the proposed onsite wastewater system is located within any drinking water source protection zone two, this zone shall be shown.

4. The location and distance to nearest sewer, owner of sewer, whether property is located within service boundary, and size of sewer.

5. Statement of proposed use if other than a single-family dwelling.

B. Soil and Site Evaluation.

1. Soil Exploration Pit and Percolation Test.

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

b. The regulatory authority shall have the option of requiring a percolation test in addition to the soil exploration pit.

c. The regulatory authority:

i. shall require additional soil exploration pits, percolation tests, or both where flows are greater than 1,000 gallons per day; and

ii. may require additional pits, tests, or both where:

(1) soil structure varies;

(2) limiting geologic conditions are encountered; or

(3) the regulatory authority 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 regulatory authority 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 regulatory authority.

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 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 absorption systems. This does not apply to lots that have received final local health department approval prior to the effective date of this rule.

a. 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. For lots that have received final local health department approval prior to the effective date of this rule, systems may be constructed in such material provided it is found to be within the required range of percolation rates specified in these rules, and provided further that the required area shall be calculated on the assumption of minimum acceptable percolation rate of 60 minutes per inch for standard trenches, deep wall trenches, and seepage pits, and 40 minutes per inch for absorption beds.

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 onsite wastewater 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. Local health departments and other local government entities may impose stricter separation requirements between absorption systems and the maximum ground water table when deemed necessary. Building lots recorded or having received final local health department approval prior to May 21, 1984 shall be subject to the ground water table separation requirements of the then Part IV of the Code of Waste Disposal Regulations dated June 21, 1967, that states "high ground water elevation shall be at least 1 foot below the bottom of absorption systems and at least 4 feet below finished grade". Notwithstanding this grandfather provision for recorded or other approved lots, the depth to ground water requirements are applicable if compelling or countervailing public health interests would necessitate application of the more stringent requirements of this regulation.

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 the onsite wastewater system. Maximum ground water table shall be determined where alternative onsite 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 an onsite wastewater 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 redoxmorphoric features, i.e. a mottled coloring.

(3) Previous ground water records and climatological or other information may be consulted for each site proposed for an onsite wastewater 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 or experimental onsite wastewater 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 regulatory authority shall require that the effectiveness of such devices in lowering the ground water table be demonstrated during the season of maximum ground water table.

4. 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 onsite wastewater systems; 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 onsite wastewater systems.

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

5. Other Factors Affecting Onsite Wastewater 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 onsite 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".

6. Unsuitable.

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

C. Lot Size.

One of the following two methods shall be used for determining minimum lot size. Determination of minimum lot size by the regulatory authority would not preempt local governments from establishing larger minimum lot sizes.

1. Method 1.

The local health department having jurisdiction may determine minimum lot size. Under this method, local health departments may elect to involve other affected governmental entities and the division in making joint lot size determinations. The division will develop technical information, training programs, and provide engineering and geohydrologic assistance in making lot size determinations that will be available to local health departments upon their request. Individuals or developers requesting lot size determinations under this method will be required to submit to the local health department, at their own expense, a report that accurately takes into account at least the following factors:

a. soil type and depth;

b. area drainage, lot drainage, and potential for flooding;

c. protection of surface and ground waters;

d. setbacks from property lines, water supplies, etc.;

e. source of culinary water;

f. topography, geology, hydrology and ground cover;

g. availability of public sewers;

h. activity or land use, present and anticipated;

i. growth patterns;

j. individual and accumulated gross effects on water quality;

k. reserve areas for additional subsurface dispersal;

l. anticipated wastewater volume;

m. climatic conditions;

n. installation plans for wastewater system; and

o. area to be utilized by dwelling and other structures.

2. Method 2.

a. Whenever local health departments do not establish minimum lot sizes for single-family dwellings that will be served by onsite wastewater systems, the requirements of Section R317-4-13 Tables 1.1 and 1.2 shall be met.

b. For non-residential facilities, one-half of the buildable area of the lot must be available for the absorption system and replacement area.

i. The area required for the absorption system and replacement area may be adjusted during the permitting process.

4.2. Subdivision Onsite Wastewater System Feasibility Determination.

A. In addition to information in Subsection R317-4-4.1, the following information must be provided on a plat map:

1. the proposed street and lot layout with all lots consecutively numbered;

2. size and dimensions of each lot, with the minimum required area sufficient to permit the safe and effective use of an onsite wastewater system, including a replacement area for the absorption system;

3. location of all water lines;

4. location of any easements; and

5. areas proposed for wastewater dispersal, including replacement area.

B. Surface drainage systems shall be included on the plan, as naturally occurring, and as altered by roadways or any drainage, grading or improvement, installed or proposed by the developer. The details of the system shall show the surface drainage structures, whether ditches, pipes, or culverts, will in no way affect onsite wastewater systems on the property.

C. Each proposed lot shall have at least one soil exploration pit, percolation test, or both.

1. The regulatory authority may allow fewer tests based on the uniformity of prevailing soil and ground water characteristics and available percolation or soil log test data.

2. If soil conditions and surface topography indicate, a greater number of soil exploration pits or percolation tests may be required by the regulatory authority.

3. The location of all soil exploration pits and percolation test holes shall be clearly identified on the subdivision final plat and identified by a key number or letter designation.

4. The results of such soil tests, including stratified depths of soils and final percolation rates for each lot shall be recorded on or with the final plat.

5. Soil exploration pits and percolation tests shall be conducted as closely as possible to the dispersal system sites on the lots or parcels.

D. Whenever available, information from published soil studies of the area of the proposed subdivision shall be submitted for review.

E. If soil or site conditions exist in or near the project so as to complicate design and location of an onsite wastewater system, a detailed system layout shall be provided for those lots presenting the greatest design difficulty by meeting rules in Section R317-4-5.

4.3. Statement of Feasibility.

After review of all information, plans, and proposals, the regulatory authority shall make a written determination of feasibility stating the results of the review or the need for additional information.

A. An affirmative statement of feasibility for a subdivision does not imply that it will be possible to install onsite wastewater systems on all of the proposed lots, but shall mean that such onsite wastewater systems may be installed on the majority of the proposed lots in accordance with minimum state requirements and any conditions that may be imposed.

B. The regulatory authority shall establish the expiration, if any, of the statement of feasibility.