Current through Register Vol. 30, No. 38, September 20, 2024
A. A 4.07
General Permit allows for the use of a lined evapotranspiration bed receiving
wastewater treated to a level equal to or better than that specified in
R18-9-E302(B).
1. Definition. For purposes of
this Section, a "lined evapotranspiration bed" means a disposal technology
characterized by a bed of sand or other media with an internal wastewater
distribution system contained on the bottom and sidewalls by an impervious
synthetic liner.
2. An applicant
may use a lined evapotranspiration bed if site conditions restrict soil
infiltration or require reduction or elimination of the volume of wastewater or
nitrogen load discharged to the native soil.
3. Provision of a reserve area is not
required for a lined evapotranspiration bed.
B. Restrictions. Unless a person provides
design documentation to show that a lined evapotranspiration bed will properly
function, the person shall not install this technology if:
1. Average minimum temperature in any month
is 20° F or less,
2. Over 1/3
of average annual precipitation falls in a 30-day period, or
3. Design flow exceeds net
evaporation.
C.
Performance. An applicant shall ensure that a lined evapotranspiration bed:
1. Prevents discharge to the native soil by a
synthetic liner,
2. Attains full
disposal of wastewater to the atmosphere by evapotranspiration, and
3. Prevents ponding of wastewater on the bed
surface and maintains an interval of unsaturated media directly beneath the bed
surface.
D. Notice of
Intent to Discharge. In addition to the Notice of Intent to Discharge
requirements specified in
R18-9-A301(B)
and
R18-9-A309(B),
an applicant shall submit:
1. Capillary rise
potential test results for the media used to fill the evapotranspiration bed,
unless sand meeting a D50 of 0.1 millimeter (50 percent
by weight of grains equal to or smaller than 0.1 millimeter in size) is used;
and
2. Water mass balance
calculations used to size the evapotranspiration bed.
E. Design requirements. In addition to the
applicable requirements in
R18-9-A312,
an applicant shall:
1. Ensure that the
evapotranspiration bed is from 18 to 36 inches deep and calculate the bed
design on the basis of the capillary rise of the bed media, according to the
"Standard Test Method for Capillary-Moisture Relationships for Coarse- and
Medium-Textured Soils by Porous-Plate Apparatus, D2325-68 (2003)," published by
the American Society for Testing and Materials and the anticipated maximum
frost depth. This material is incorporated by reference and does not include
any later amendments or editions of the incorporated material. Copies of the
incorporated material are available for inspection at the Arizona Department of
Environmental Quality, 1110 W. Washington, Phoenix, AZ 85007 or may be obtained
from the American Society for Testing and Materials International, 100 Barr
Harbor Drive, West Conshohocken, PA 19428-2959;
2. Ensure the media is sand or other durable
material;
3. Base design area
calculations on a water mass balance for the winter months;
4. Ensure that the evapotranspiration bed
liner is a durable, low hydraulic conductivity synthetic liner that has a
calculated bottom area and sidewall seepage rate of less than 550 gallons per
acre per day;
5. If a surfacing
layer is used, use topsoil, dark cinders, decomposed granite, or similar
landscaping material placed to a maximum depth of 2 inches. The applicant shall
ensure that:
a. If topsoil is used as a
surfacing layer for growth of land scape plants:
i. The topsoil is a fertile, friable soil
obtained from well-drained arable land;
ii. The topsoil is free of nut grass, refuse, roots, heavy clay,
clods, noxious weeds, or any other material toxic to plant growth;
iii. The pH of the topsoil is between 5.5
and 8.0;
iv. The plasticity index
of the topsoil is between 3 and 15; and
v. The topsoil contains approximately 1 1/2
percent organic matter, by dry weight, either natural or
added;
b. If another
landscaping material is used as a surfacing layer, the material meets the
following gradation:
|
Sieve Size
|
Percent Passing
|
|
1"
|
100
|
|
1/2"
|
95-100
|
|
No. 4
|
90-100
|
|
No. 10
|
70-100
|
|
No. 200
|
15-70
|
6. Use shallow-rooted, non-invasive, salt and
drought tolerant evergreens if vegetation is planted on the evapotranspiration
bed;
7. Install at least two
observation ports to allow determination of the depth to the liquid surface of
wastewater within the evapotranspiration bed;
8. Design the bed to pump out the saturated
zone if accumulated salts or a similar condition impairs bed performance;
and
9. Instead of the minimum
vertical separation required under
R18-9-A312(E),
ensure that the minimum vertical separation from the bottom of the
evapotranspiration bed liner to the surface of the seasonal high water table or
impervious layer or formation is at least 12 inches.
F. Installation requirements. In addition to
the applicable requirements in
R18-9-A313(A),
an applicant shall ensure that:
1. All liner
seams are factory fabricated or field welded according to manufacturer's
specifications. The applicant shall ensure that:
2. The liner covers the bottom and all
sidewalls of the bed and is cushioned on the top and bottom with layers of sand
at least 2 inches thick or other puncture-protective material;
3. If the inlet pipe passes through the
liner, the joint is tightly sealed to minimize leakage during the operational
life of the facility;
4. The liner
is leak tested under the supervision of an Arizona-registered professional
engineer; and
5. A 2- to 4-inch
layer of one-half to 1-inch gravel or crushed stone is placed around the
distribution pipes within the bed. The applicant shall place filter cloth on
top of the gravel or crushed stone to prevent sand from settling into the
crushed stone or gravel.
G. Additional Discharge Authorization
requirements. An applicant shall submit the liner test results sealed by an
Arizona-registered professional engineer to the Department for issuance of the
Discharge Authorization.
H.
Operation and maintenance requirements. In addition to the applicable
requirements in
R18-9-A313(B),
the permittee shall:
1. Not allow irrigation
of an evapotranspiration bed; and
2. Protect the bed from vehicle loads and
other damaging activities.
