Section R18-9-E307. 4.07 General Permit: Lined Evapotranspiration Bed, Less Than 3000 Gallons Per Day Design Flow

A.      A 4.07 General Permit allows for the use of a lined evapo- transpiration 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 evapo- transpiration bed” means a disposal technology character- ized 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 reduc- tion or elimination of the volume of wastewater or nitro- gen load discharged to the native soil.

Provision of a reserve area is not required for a lined evapotranspiration bed.

strictions. Unless a person provides design documentation show that a lined evapotranspiration bed will properly func- n, the person shall not install this technology if:

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 evapo- transpiration 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 evapo- transpiration bed.

E.       Design requirements. In addition to the applicable require- ments 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 Relation- ships for Coarse- and Medium-Textured Soils by Porous- Plate Apparatus, D2325-68 (2003),” published by the American Society for Testing and Materials and the antic- ipated maximum frost depth. This material is incorpo- rated 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 cal- culated 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 landscape 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 per- cent organic matter, by dry weight, either natu- ral 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 toler- ant evergreens if vegetation is planted on the evapotrans- piration bed;

7.        Install at least two observation ports to allow determina- tion of the  depth to the liquid surface of wastewater within the evapotranspiration bed;

8.        Design the bed to pump out the saturated zone if accumu- lated salts or a similar condition impairs bed perfor- mance; 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 require- ments 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 Ari- zona-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 appli- cant shall submit the liner test results sealed by an Arizona-

registered professional engineer to the Department for issu- ance 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.

Historical Note

New Section adopted by final rulemaking at 7 A.A.R. 235, effective January 1, 2001 (Supp. 00-4). Amended by final rulemaking at 11 A.A.R. 4544, effective November 12, 2005 (05-3).