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.
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.
