| (a) The permittee must demonstrate in the engineering
report and ensure that the hydraulic application rate for a subsurface
area drip dispersal system meets one of the following.
(1) The hydraulic application rate shall not exceed
0.1 gallons per square foot per day for a subsurface area drip dispersal
system located west of the boundary shown in Figure 1 in paragraph
(2) of this subsection, and using a vegetative cover of non-native
grasses that are over seeded with cool season grasses in the winter
months (October - March).
(2) The hydraulic application rate for a subsurface
area drip dispersal system located east of the boundary shown in Figure
1 of this paragraph or in any part of the state when the vegetative
cover is any crop other than non-native grasses, the permittee shall
use the equations in Figure 2 or 3 of this paragraph to establish
the rate.
Attached Graphic
Attached Graphic
Attached Graphic
(3) The applicant must calculate the hydraulic application
rate for each month of the year. A monthly water balance is computed
that includes soil moisture storage. Any available soil moisture is
carried over to the next month. The maximum application rate is exceeded
when the total hydraulic loading (rainfall and irrigation) exceeds
the total of the available soil moisture storage, the actual water
requirement of crop (inches per month), and leaching.
Attached Graphic
(4) The permittee may use an alternative method to
calculate the hydraulic application rate with approval from the executive
director.
(b) The nitrogen application rate for a subsurface
area drip dispersal system must be calculated using the anticipated
nitrogen concentration of wastewater effluent prior to land application.
(1) The permittee must calculate the allowable annual
hydraulic loading rate based on nitrogen limits using the equation
in this paragraph.
Attached Graphic
(2) Upon request by the applicant, the executive director
may approve other fractions of applied nitrogen removed based upon
special conditions relating to a proposed site, if justified in the
engineering report.
(c) The result obtained from calculation of the allowable
annual hydraulic loading rate that is based upon nitrogen limits must
be compared to the hydraulic loading rate that is based on crop need
and soil water holding capacity in the figure in subsection (a)(3)
of this section. The more restrictive of the two calculations will
set the maximum hydraulic application rate.
(d) The volume of wastewater used when calculating
the disposal area required based on the hydraulic application rate
as described in this section may be reduced by the beneficial reuse
credit, as calculated in accordance with Chapter 309, Subchapter D
of this title (relating to Beneficial Reuse Credit) and approved by
the commission.
(e) The disposal site area required may not be reduced
by more than 50% of what the disposal site requirement would be using
the permitted flow without the beneficial reuse credit.
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